sensor and simulation notes note 244 surface field measurements with image and ground...
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Sensor and Simulation Notes
Note 244
November 1977
Surface Field Measurements withImage and Ground Planes
!3.L. SenguptaJ. E. Ferris
T. B. A. Senior
University of MichiganAnn Arbor, MI 48109
Abstract
Results obtained from the measurement of currents and charges induced
on some selected conducting bodies illuminated by plane electromagnetic
waves are presented. The bodies considered are cylinders, bodies of
revolution, and scale models of 747 aircraft. The measurements using
the image plane technique were performed in the model frequency range of
0.45 GHz to 4.25 GHz. Data are presented for simulated conditions of free
space, and in the presence of perfectly conducting and lossy ground planes.
The cylinder length-to-diameter ratio, including its image, is 10; and the
measurements cover the frequency range corresponding to ka = OiQ15’n to.
ka - 1.5 m. The body of revolution and the 747 results are shown at the
full scale frequency ranges 1.13 MHz to 21.2 MHz and 0.98
respectively. These full scale results have been deduced
frequency data.
Acknowledgment
MHz to 26.5 M1-iz,
from the model
It is a pleasure to acknowledge the assistance of Messrs. D. Sayre,R. Stoddard, J. Tedesco, and K. Young, all of the Radiation Laboratory, in~erforming the measurements, computer programming, data processing and othertasks involved in this study.
-.=.
Sensor and Simulation Notes
Note 244
Noveiiiber1977
Surface Field Measurements withImage and Ground Planes
V. V. Li.epaD. L. SenguptaJ. E. Ferris
‘T. B. A. Senior
University ofllichiganAnn Arbor, MI 48109
. . .,’-
Abstract....
Results obtained from the measurement of currents and charges induced
on some selected conducting bodies illuminated by plane electromagnetic
waves are presented. The bodies considered are cylinders, bodies of
revolution, and scale models of-747 aircraft. The measurements using
‘the image plane technique were performed in the model frequency range of
0.45 GHz to 4.25 GHz. Data are presented for simulated conditions of free ‘-
space, and in the presence of perfectly conducting and lossy ground planes.
The cylinder length-to-diameter ratio, including its image, is 10; and the
measurements cover the frequency range corresponding to ka = 0.015 m to-
ka - 1.5 n. The body of revolution and the 747 results are shown at theW.*1.$Fc1full scale frequency ranges 1.13 MHz to 21.2 MHz and Q~98 MHz to ,;. Z> ‘ ,2
~. .... *W.respectively.
T
‘These’full scale results have been deduced from @ , *+ s “~m
frequency data. W\it ‘:@
Acknowledgment “e Q&
It is a pleasure to acknowledge the assistance of Messrs. II.Sah ~~1
R. Stoddard, “J.Tedesco, and K. Young, all of the Radiation Laboratory, Inperforming the measurements, computer programing, data processing and othertasks involved in this study.
,.F-
TABLE OF CONTENTS
Section
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DATA
3.1
3.2
3.3
COW.
The
The
Chamber and Its
Ground Plane. .
Image Plane
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Excitation Antenna.
Test Models . . . .
Sensors and Their Implementation.
Instrumentation . . .
Measurement Procedure
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Cylinders . . .
3.1.1 Cylinder
3.1.2 Cylinder
3.1.3 Cylinder
Body of Revolution.
747 Aircraft. . . .
,USIONS.. , . . . .
in Free Space
Near Perfectly Conducting Ground Plane..
Near Lossy Ground Plane . . . . . . .,
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c. APPENDIX A. THEORETICAL ANALYSIS OF REFLECTIONS FROMA
1 FINITELY CONDUCTING GROUND PLANE. . . . . . . .
A.1 Earth Constants at Full Scale Frequencies . . . . . . .
A.2 Simulated Ground Plane. . . . . . . . . . . . . . . . .
(continued on next page)
2
TABLE OF CONTENTS
(Continued)
A.3
A.4
A.5
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Reflections From The Simulated Ground
Numerical Results and Discussion. . .
Computer Program Listing. . . . .*.
Plane
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3
1. INTRODUCTION
During the past 20 months the fields and charges have been nwasured as
functions of frequency at selected stations on a variety of bodies, many of
them in the presence of Iossy and/ormetallic ground planes. One group of
measurements was distinct from the rest in being concerned exclusively with
scale nmdels of the F-111 aircraft in simulated free space; and since the
results have already been presented in a technical report [1], it is sufficient
to confine attention to the remaining portions of the study.
The overall objectives were to obtain data under experimentally controlled
conditions that will aid in better understanding the material interaction of hori-
zontally and vertically polarized hybrid and dipole simulators with test objects, and
that will also serve as a data base for comparison with calculations using any
of the computer codes available. The objects to be considered were circular
cylinders, a body of revolution rode] of an aircraft, and a scale model of the
747 aircraft. All were to be probed in the presence of a perfectly conducting
ground or image plane and, i’nsome cases, a lossy ground plane as well, model-
ling the earth in the vicinity of the Achilles/Athamas simulators at Kirtland
Air Force Base. It was therefore necessary to convert our free space measure-
ment facility into an image plane set-up by constructing a large metallic plane
in one of our anechoic chambers.
The 20-nmth duration of the contract saw a number of changes in our
experimental facilities and in the techniques used for the acquisition and
processing of surface field data. Some of these changes were voluntary and
aimed at improving”efficiency and the quality of the data obtained; however,
one was involuntary and though it ultimately led to an improvement in capa-
bility, the change itself was disruptive, and costly in both time and effort.
Because these evolutions have had an impact on the performance of the work,
it would seem appropriate to give.a brief historical account.
[1] Valdis V. Liepa, “Surface Field Measurenmts on Scale Model F-111 Aircraft,”The University ofhiichigan Radiation Laboratory Report No. 014449-I-T;InteractionApplication Memos, Memo 13, September 1977.
4
4!)o In the early stages of the contract two anechoic chambers were available.
The first was a tapered room 50 ft. in length with a rectangular (test) section
12 ft. high, 18ft. wide and long. This was specifically designed for surface
field measurements and has VHP-48 absorber on the back wall and VHP-18 absorber
on critical areas of the sidewalls, ceiling and floor. The other was a larger
multipurpose room 15 ft. high, 30 ft. wide~ and 100 ft” lon9 of somewhat Poorer
electrical performance. It was our original intention to use the tapered room
(actualIy, a predecessor of the one just described); but because of the necessity
of having the image plane vertically in this, it was felt that the modification !+.-ewould be too disruptive of the other measurement programs for which this room
wwas
Wil’
was
1/2
required. The decision was therefore made to use the multiPurPose room at:
ow Run Airport where the image plane could be installed horizontally.
Since the cement floor of this room was remarkably flat, the image plane
constructed by removing the absorber and then laying 4 fto bY 8 ft” sheet$ of
inch thick drywall (or sheetrock) sheets directly on the floor over an area
3 2Q ft. by 48 ft. The joints were filled, taped, and subsequently sanded to obtain%
9)the required smoothness, and the whole was then covered with overlapping strips
of 0.0015 inch thick aluminum foil to make the surface conducting. Edges were
fastened with Scotch tape. In critical areas near the transmitting antenna arid”
the test objects, 1/8 inch thick aluminum sheets were used instead of foil, and
these were placed on top of 3/8 inch thick drywall to ensure a level surface
for the plane. Probe and sensor leads were taken out through channels cut in._
the drywall sheets. While this construction was underway, the necessary probes
and models were being fabricated; and by early November we had completed our
probing of the field in the vicinity of the image plane, and had just started.measurements on the cylindrical models.
Y
The major disruption came at the beginning of December when the University.
.,&of Michigan announced the sale of Willow Run Airport effective 1 January 1977.
Although we were irnnediatelygiven access to a nearby anechoic room which,
though srnqller$Was actually better in electrical performance, there was no
way to transfer the ground plane without effectively destroying it. We were,
L2therefore faced with a massive relocation operation and the construction of
0yet another image plane in the new facility.
5
The new chamber is 15 ft. high, 30 ft. wide and 50 ft. long and lined with
absorbing material suitable for RF operation down to 0.4 GHz; and since time
was now important, we were fortunate that its design made a simpler and better
image plane possible. The floor is wood and has a recessed area (or crawl
space) 8 ft. square and 4 ft. deep underneath. By perfoming the measurements
in a region above this area, it was now possible to lay a purely metallic ground
plane directly on the wooden floor, with the probe leads coming out into the
recess. A plane was therefore constructed from 4 by 12 ft. sheets of 1/32 iich
aluminum covering an area 24 by 44 ft. Joints were covered using conducting
adhesive aluminum tape, and by late January we had a superior facility at our
disposal and were in a position to carry on with the program where we had left
off. However, two considerations suggested that it would be better to start
the measurements from scratch. In the first olace the ground plane (size and
construction), the antenna location and the chamber itself were all different
from before, and the changes would almost certainly show up when data for
different and/or different-sized bodies were compared; and, secondly, we were
now ~n the process of converting to an automatic data acquisition system to
avoid the tedious and error-producing task of digitizing analog data manually.
The developments in our data acquisition and processing systems in this period
of time have been described by Liepa [2, 3J. It was therefore decided that we
should repeat all the measurements that had previously been performed in the
old chamber? and in effect the data presented here are the pvodutt of a nine-
month investigation.
.
J
In Section 2 we describe the physical setup, including the ground planes,
models~ sensors and instrumentation used. The data are presented in Section3
in the form of amplitude and phase plats as functions of the full scale frequency <in the case of the aircraft modelsl and as functions of ka for the cylinders, !.where a is the cylinder radius. A brief discussion of the data is given in
,....
Section 4.
[2] Valdis V. Liepa,The UniversInteraction
[3] Valdfs V. Liepa,The Univers”Interaction
“Surface Field Measurements an Scale Model EC-135 Aircraft,”ty of Mi@igan Radiation Laboratory R ort No. 014182-1-F;Appllcatlon Memas, Memo 15, August 19%
“Surface Field Measurements on Scale Model EC-4 Aircraft>”
i;p?lJl\!igi!&:ihwTYbfi:::trf9!w0rt ‘o” ‘14182-2-F’ 0
6
2. PHYSICAL DESCRIPTIONS...
2.1 The Chamber and Its Image Plane
-.
The measurements presented in this report were all made inan anechoic
chamber 15 ft. in height, 30 ft. in width and 50 ft. long designed to operate,.down to at least 0.4 6Hz. The chamber occupies an entire building apart from
..a small room at one end containing metal and tioodshop equipment, and a room
at the other (front) end for iristrumentation,storage and personnel. An aperturek-
.. .in the wall separating the latter room from the chamber can be used for feedingl
cables into the room, placing antennas for pattern or scattering measurements,
or merely observing work in”progress in the chamber.
L
‘To convert the chamber,from a free space measurement facility to a ground
(or image) plane facility, a portion of the floor was stripped of absorber and
then covered by 4 by 12 ft. aluminum ”sheets1/32 inch in thickness. The joints
were sealed using 1-1/2 inch wide adhesive conducting aluminum tape. The re-
sulting 24 by 44 ft. image plane was placed symmetrically about the center line
of the room and butted into the VHP-18 absorber on the backwall to provide a
reasonable match for the currents flowing down the plane: see Figure 1 for -
a sketch emphasizing the image plane rather than the chamber. The transmitting
antenna was located near the edge closest to the front wall, thereby creating
a working area extending 30 ft. db~” the plane to the test location. Instru-...mentation was housed in”the ro&”6ehind the front wall.
--
2.2 The Ground Plane
In many applications a ground plan: is
screen placed horizontally, often
@S!!2.Planes and the 9round Planeof ground plane were required: a
lossy one simulating the earth in
suitably scaled frequencies.
on the ground,
is vertical as
a large metallic plate or :&’but in our case this is the
shown in Figure 2. Two types -
metallic (perfectly conducting) plane, and a
the vicinity of Kirtland Air Force Base at
7
/.. ,. ..J $.
cm
o
Figure 1. Image plane facility.
4$0
U
0
Figure 2. Loss:{ groJnd plane. The perfectly coi-l-ducting gt-ound plane is behind. The 747
model is 1/160.01 scale.
f)
At first glance it might appear that the ground plane should be chosen as
large as posstble, but th~s is not necessarily true in practice. Any plane
perpendicular to the direction of propagation will reflect most of the incident
energy back to the transmitting antenna, where half is reradiated to create an
effective incident field which is frequency dependent. In a previous study [2]
the interaction between a 4 by 12 ft. metallic ground plane and the transmitting
antenna produced oscillations of as much as 6 dB when the sigpal was recorded
as a function of frequency. Various methods were explored for decreasing the
interaction. One is obviously to rotate the plane to direct the reflected
energy away from the antenna; but this was not deemed acceptable, and we were
finally forced to reduce the plane to minimum size consistent with the mainten-
ance of its image-forming property. In fact, all but a 4 by 4 ft. section of
the ground plane had to’be covered with absorber to reduce the oscillations to
an acceptable ?evel.’
In view of this experience, we now chose inxnediatelya 4 by 4 ft. ground
plane mounted verticatlyon the image plane and corresponding to a 4 by 8 ft.
ground plane under free space conditions, but special care was necessary to
minimize the distortion of the surface field created by the
incident field is vertically polarized the only significant
current is likewise vertical. The side edges of the ground
edges. Since the
component of the
plane then have only
a negligible effect on the current, which is within 10 percent of its physical
optics value at all points more than a small fraction of a wavelength from these
edges [4]. However, a horizontal edge is another matter; and since this would
reflect the current to produce a standing wave pattern, the ground plane was
smoothly mated to a cylindrical surface at its upper edge, ~nd the shadowed
portion of the cylinder treated with absorber. The resulting ground plane
structure weighs about 80 Tbs. and can be moved as required. When in position,
its bottom edge is fastened to the image plane using metallic tape to ensure
continuity of the current from the image plane to the ground plane.
-
[4] J.J. Bowman, T.B.A. Senior and P.L.E. Uslenghi, “Electromagnetic andAcoustic Scattering by Simple Shapes,” North-Holland Publishing Co.,Amsterdam, 1969.
0
10
The lossy ground
scaled frequencies of
electrical properties
are shown in Figure 3.
plane was required to provide simulation at suitably
the ground at Kirtland Air Force Base, and the measured
of the ground expressed in terns of complex permittivity [5] (
The soil is practically nonmagnetic, so that its per-\,
meability is that of free space. In order to specify the complex permittivity
desired for our ground plane material, it is necessary to take into account -
the scale factor p relating the laboratory frequencies to the full scale ones.
Thus
“lab. = “
-&’’lab. = E“IP
where p ranges from 39.25 for the large cylinder to 460.25 for the small 747
~del. More complete scaling factor information is given in Section 2.4.
Some of the considerations that went into the selection of a suitable
material are given in Appendix A, and ultimately the LS-26 dielectric manu-
facturedby Emerson and Cuming, Inc. was chosen. Its electromagnetic properties
have been measured by the Avionics Laboratory of Wright-Patterson Air Force
Base, and the data are presented as functions of frequency in Figures 4 and 5.
Based on these values, the performance expected of our ground plane is dis-
cussed in Appendix A.
The metallic ground plane was used as the support structure for the 10SSY
ground plane. The LS-26 material is 3/4 inch in thickness and comes in-12-foot square panels. A total of 12 panels were acquired and assembled into
a three-layer sandwich 4 by 4 ft. in size. This was then attached to the
metallic ground plane.~~,
-.
[5] R.D. Carrel, W.R. Eberle, D.R. Cunningham and M.J. Cunningham, “ElectricalProperties of Earth at the AFSWC Dipole Facility and HorizontallyPolarized Simulator Sites at Kirtland Air Force Base, New Mexico,”U.S. Geological Survey, Special Project 27, February 1970.
E’
o
20
15
10
5
0
\ c“
,
80 1000’ 20 40 60
Frequency (MHz)
Figure 3. Average values of E’ and c“ !s: frequency for theearth beneath the Dipole Faclllty [5]. P = Uo.
o
!00
300
c“
200t
100
0
--n
-P.
(9
-c
o-i-l
.
‘mi,
i.l‘N- i !.
~! _i*---
II0)”‘
./
I.,,.“-+--‘--
—-.._.. _ -.i
.— ---- +--
m -—- — . _ j.-i~-,— -’ -
-—l. — – ~~~–-”-4 f
0
,
8
~~-f ; i ~ ! 3! !4H N’8;qq: ! :“-0 p--- ----14 5 !6 \7”-:“?‘$_”W
! J - !“Od- I I* Il,. I ...—-—-—---} —.—...-—. -.- ...-.—- -—
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& ,., ‘ i: ‘.:__[___~ ,“ . , ,:-1..; . .::”. ._;i,1“
-%--.-4-.-. --J---
‘.[t.-.—. I~....”-
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Cu .- . —-- --— —- — — 4,. -
i; “ ‘ ‘“ ;: I i\ , 1
–1
m1
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----- - .— -—- —- - ---- .-—;: ‘
m“ : ! ‘: : :“ ! ‘; !_ _ _ “._ ._ . ...-. .i ;,.
.: :.
,.. . 1.”” ,. .“ 1; ,.
:. —- I,
:.- f—
8:
“ . i i‘1.’ “
.,a
., ,.8 # “~
- +-r.— . .-
~“1 ;, ~ ‘,~ -,,,,,~ “,; “’
,.L1.’.~IL ,
.:. .:.
“ .:..,. . -- &— ,, ,. . ...
;.’:!..}.-,,,.
,1 ‘“: . ,. i
11
- I.--- .& I .,. /. ,~.$ ‘.1
I,:., : ] ‘“!::),-: i ‘: ‘ i ~.“ I I
.41C13
\o? i::l’l I 2 I ~ .5I
i4 I ,56/7;8’4\Oo~!:~l1 1 I 1
H ‘4!5 :6 ~+ @ $Ii.”!, Iii‘y
LS-25 #2(270WLS) %3APi?77 273/JK FREQUENCY (GHz)
Figure 5. Measured G“ and v“ of LS-26 used.
o 0 0,
2.3 Excitation Antenna.<,
The wide bandwidth requirement swewhat limits the choice of antenna
for illuminatirigthe”facility. Both the log periodic and rudimentary horn
antennas meet this’requirement; but in the case of the former, the backward
wave characteristic pwduces an effective phase center whose location varies
as a function of frequency in a manner which is difficult to compensate for.
Attention was therefore given to the rudimentary horn which, for an image plane
facility, is essentially a strip line with exponentially increasing separation>-A-—>-.
be&een the strip and the plane. Various designs were tried including one
where th’estrip e’xtendedall the way to the ceiling . Although most exhibited
a tolerable VSUR, all had large side lobes, and the resulting signals bouncing
off the chamber walls significantly degraded the uniformity of the field in
the’test are~. ‘-”;.=,----
A? For these reasons it was decided to use the same broadband horn antenna
a? previously employed in our free space measurements. This covers the required
w
frequency range and has 8
Because ’of’itsrelatively
30°.-L,,
‘ The horn was mounted
height ht = 29.5 cm above
center’of the test region.
to 12 dB gain with a maximum VSMR of 3:1 over the band.
low gain, its beamwidth in free space is at least
with the center (phase center) of its aperture at a
the image plane and at a distance d = 9G0 cm from the
The variation in the incident field amplitude as a
function of the heighty of the probe above the plane is then
[1
2~htyCos — Ad
3
The 3 dB point ranges fromy = 271 cm at the lowest frequency to 28.7 cm at the .~“”+
highest, and the only model for which the variation is significant is the largest
cylinder whose physical length ~ is 50.83 cm. We remark that with this body the
variation in ~l?umination over its length is less than 3 dB if f s2.40 GHz, but
even at higher frequencies the fact that the cylinder is primarily excited at its
base will scinewhatreduce the effect of the illumination taper.
15
2.4 Test Models
Induced current and charge measurements were made on three types of
metallic models over a 10:1 frequency range from 0.45 to 4.25 GHz. The models
were right circular cylinders, bodies of revolution models of an aircraft, and
scale models of the 747 aircraft, and these are described below.
Cylinders
All the cylinders were required to have t/a = 10where .tis the
physical length and a is the radius, and frequency coverage such that the
characteristicparameter ka varied from 0.0157rto 1.5n. TWO sizes of cylinder
were used to produce this coverage. The small ones were 0.55 cm in radius and
5.55 cmlong, while the large one had a = 5.085 cm and 2 = 50.83 cm. Orielarge
and five small cylinders were fabricated, and these are shown along with their
vital dimensions in Figures 6 and 7. Because of the size of the small cylinders,
it was not possible to employ our usual external sensors, and the cylinders
which were fabricated had built-in sensors appropriate to the locations and
types of measurement ~o be made.
The contract called for charge measurements on and near the top of
the cylinder, and current measurements at the midpoint and near the base (see
Figure 6). Near was specified as a distance of 5 sensor diameters, but this
is ambiguous in our measurements since the models are scaled but not the sensors.
On the large cylinder the sensors employed were the MGL-8 and ACD-1, and con-
sidering the sizes of these and our small ones, an average sensor diameter
was defined, which was then used to find the desired measurement locations
near to the ends of the cylinders. These turned out to be 9.04 percent of the
cylinder length from
On the top
a small hole through
the ends.
of the small cylinder, a charge sensor was made by drilling
which a 0.020 inch diameter coax was passed and soldered
to the cylinder. The outer shield was then removed and the center conductor
and dielectric trimned back to a 2 mm projection. The charge probes near the
top and the center were produced in a similar fashion on the second and third
small cylinders, the idea of mounting more than one
having been abandoned because of the fragile nature
16
sensor on the same model
of the probes and the
%----
*=
6!.dITI
1-5DI
Small cylinder: Therewere five cylinders made,each having only onebuilt-in sensor. = OSSM c~nne~tor
Surface cut flat formountinq MGL-8 andACD-1 s;nsors.
Large cylinder ,0---+ \,
T4.83T
51
f-
.83
Figure 6. Cylinders used in measurements.
83
(Dimensions in cm.)
17
Figure 7. Cylinder models. Note the ACD-lA(A) sensornlountedon the large cylinder.
o a“
,
sensor leads. Magnetic loop (current) sensors were built at the center and
near the base of the remaining two ~mall cyl;nders. The sensors were of
standard design and were made by drilling two holes about 2 nxnapart in a
cylinder, through which a coax was passed to form a half loop. A slot (or
gap) was then cut in the outer shield at the-surface of the cylinder.e.., ..
<,
Body of Revolution
For their computer analyses Taylor et al. [6] designed a conglomerate,.. ,,.,of ellipsoids and cylinders to simulate t’he’EC-135 aircraft, and the shape and
(full scale) dimensions of thl; structure are given in Figure 8. Our body of
revolution is a scaled vers~’~~,of~~i’s.”’If was-required that we cover the range
ka = 0.015Trto<0.27m where a i<the ra~ius ’ofthe’(central portion of the). .fuselage; and’to achieve-this-with the 10:l’range~of’frequencies’available, it
..—— —.--~=- ---,---- .-.— -:was necessaryLto_construct two different sized mo.~s~ ‘“T~se are shown in
Figure 9, Their actual scale factors are 1/199.35 and 1/399.20 (nominally
1/200 and 1/400), and together they provide coverage from ka = 0.015n to
0.28~..+,;,.,.,
The models were machined from solid brass and because of the tapered
shapes of the various members, the construction was a complicated task involvirlg
almost 80 hours of machinists’ time. The tapering was first done’in staircase
fashion, and the piece was then smoothed to the shape prescribed by the appro-
priate equation in [6]. Because of our image plane, only a half-model was
needed; but for the fuselage and the vertical fin, the cofipletemembers were
constructed and the right sides ground off on a milling machine. The wings
and fins were .then attached (soldered for the smaller model and with screws &&.
for the larger) to form the left side of the aircraft. Finally, each model was
mounted on a metal plate approximately 20 by 30 cm in size, and the minute gap
between the fuselage and plate was filled with silver paint to ensure good
electrical contact.
[6] C,D. Taylor, K.T. Chen and T.T. Crow, “Electromagnetic Pulse Interactionwith the EC-135 Aircraft,’’Interaction Application Memos, Memo 10,July 1975.
IWT/T
55.1%
Station Legend
WT/T - Wing Tip, Top
WC/T - Wing Center, Top
WR/T - Wing Root, Top
F/S - Fuselage, Side
Figure 8, Body of revolution; full scale dimensions inmeters.
.
#
‘.
.!,
747 Aircraft
Two plastic scale model kits for the 747 aircraft were purchased.
Only the left sides were assembled and these were filled with plastic (auto
body fiberglass) to help in mounting the models on aluminum plates. The
models were smoothed and painted with conducting (silver) paint, and finally
the contact edges with the plates were ttiuchedup to avoid any gaps. The
fuselages were of lengths 14.54 and 44.08 cm, but since the excitation was
antisymnetric, the wingspan provides the critical dimension- On this basis
the scale factors for the two models were 1/460.75 and 1/160.01. Drawings
and photographs of the models are shown in’Figures 10 and 11.
2.5 Sensors and Their Implementation.“ ;-
,,Three types of sensors were used in this study: built-in ones for
the small cylinders, the MGL-8 and ACD-1 for the large cylinder, and miniature
surface probes for the bodies of revolution and the 747 aircraft.
The built-in ones were an integral part of the model and were described
in the previous section. The large cylinder was big enough to accommodate the
B-dot MGL-8A(R) and D-dotACD-lA(A) sensors for current and charge measure-
ments respectively. Each has a base plate and requires a hole to be drilled
in the surface to take the signal lead into the interior of the model. Mount-
ing was easy on the top of the cylinder, but on the side of the cylinder an
area equal to that of the base plate was machined flat at each sensor location
and then the hole drilled. To minimize the possibility of ~erturbing the
surface fields, the milled areas which were not in use were taped over to
bring the surface back to its original curvature.
The above sensors are too large
and our original idea of building in
the difficulty in calibrating them.
fore constructed and these are shown
for the body of revolution and 747 models,
sensors was finally abandoned because of
Special surface-mounted probes were there-
in Figure 12. Each is made from 0.020 inch
o
.. .
22
a
A’.:..- \... \---. ---- T %
I
,1
. .
WT/T - Wing
WC/T - Wing
WR/T - Wing
: ...
----,.
Tip, Top...—-
,’
Center, TOP ..Root, TOP ..
F/S - Fuselage, Side.-:. ‘,.. _,_.
.-:”*. ‘5., ---- - -+= ,- ,- .,:. =4.. ..:
Figurg 10. ““747”’aircraft.Full.......- fuselage length (L)span (H) = 29.82m.
scale din]ensions:= 68.63m, hulf wing-
o
.- 1Fiqure Il. 747 scale models. The dark area around each fuselage
is conductive silver paint.
o0
,!
2.5 m
lt-
7
d+OSSM 552-1
+
--i
10 m
~ 47
J
30 cm long0.020 inch coax
+OSSM 552.1
Current Sensor Charge Sensor
.- —
,- -.
i...%.,— !2%’
Figure 12: Miniature external current and chargesensors.
-..
25
diameter coaxial line about 30 cm long and a 10 by 12fMn 3-roilthick flexible
brass plate. For the current probe two holes are drilled in the plate and a
previously bent section of coaxial line is inserted through. The coax (including
center conductor) is then soldered to the plate from the underside and, finally,
a slot is cut in the outer shield at the center top of the loop. This last step is
the most tricky part of the entire operation. There is a rather high probability
of slicing through the center conductor as well, thereby destroying the sensor,
and it usually took three attempts to make a single good probe. The charge
probe was much easier to construct. The coax was simply passed through a hole
in the plate where the outer conductor was soldered. From the short end the
outer conductor was removed, being cut flush with the surface of the plate,
leaving just the dielectric and the center conductor. With both probes, the
output ends of the coaxial lines had connectors of the Omni-Spectra OSSM 551-1
(male} or -2 (female) type.
To use these probes on the body of revolution and 747 models, slots were
cut at the desired locations on the wings and fuselages through which to pass
the coaxial lead. The small sensor plate was then taped to the model with
conducting tape and in addition the slots not in use were taped. The sensor
lead emerged on the other side of the model (in the case of a wing, the under-
side), and from there was taped to the surface until it reached the image plane
where it passed through a hole out of harm’s way. Itwill be obvious that the
process of mounting and taping a probe was tedious and time consuming, and
required a good deal of care to ensure that the signal lead was not bent.in a
manner that would nullify the calibration.
2.6 Instrumentation.r-
For the most part the instrumentation used was the same as in our
previous [1, 2] free space model measurements? the only differences being in
the cabling and [in some cases) the sensors. The main categories of equipment
are showm in Figure 13, where thdl+P (Hewlett-Packard)numbers indicate the
26
181’
N-4
I,Broadband Antenna
Signal Gen. iand
Power AmpsLr
I(HP 8620A) 8c I
I aJL IIIIIII1~
IIIIIII1-——
~signal flow
‘———digital control
0)Model
&
2
I
I Test FacilityCY L ———— .——— ——.— ——.— .
I “m1 &Network .1-
Low Noise mAnalyzer
(HP 841OA) Pre-Amps
IIIII1III
I 4 F————— ————————————-———___,
I I :Post Processing
1Digital~
DigitalI
University of P1otterData Acquisition Michigan (HP 2703)
System1-
Computer
(HP 9830A)Punch Cards]
I Amdahl 470 V/6 +
~ 4 Mag Tape I
Figure 13. Block diagram of the experimental setup.
I
I I
key Items. However, each block may contain many individual pieces. Thus, the
HP 9830A calculator in the digital data acquisition block is only one of
almost a dozen pieces here, and represents only about a third of the total cost
of the equipment in the block. The same is true for most of the other blocks.
The heart of the system is the data acquisition group which controls the
transmitted frequencies and records and stores the measured surface field
values. The process is as follows. Information is sent to the 8620A signal
source to generate a particular cw signal, and the latter is then amplified to
about 1 watt by a transistor or traveling wave tube amplifier and passed to a
broadband ridged horn antenna where it is radiated. Just prior to the antenna,
a small portion (-20 dB} of the signal is tapped and fed to the network analyzer
as a reference. The radiated field excites currents and charges on the model.
The sensor relates the current or charge to a voltage that is first amplified
(20 to 40 dB depending on the frequency band) by a low noise preamplifier and
then passed to the network analyzer which measures its amplitude and phase
relatiye to those of the reference signal. The values are digitized by the
data acquisition system and stored in its memory. The frequency is now incre-
mented to a new value and the whole sequence repeated.
About 125 frequencies are used to cover a frequency band and the measure-
ments take about Z minutes. At the end of this, the data are transferred from
the calculator core to a preassigned file on a cassette magnetic tape, and
the equipment becomes available for the next set of measurements, e.g., a cali-
bration run, measurements of a different field component or at a different
station, or measurements in a different frequency band. A single transfer
functim such as those shown in Section 3may require as many as nine sets of
measurements: two models over each of three frequency bands, plus three
calibration runs.
28
2.7 Measurement Procedure
The data recorded seldom resemble what one might initially
expect. What is actually measured is the ratio of the received and reference
signals at the terminals of the network analyzer, and this is quite different
from the ratio of the field at the sensor to the field incident on the model.
For example, the transmitted field is not frequency independent and may vary
as much as + 5 dB over the entire 10:1 band. It is virtually impossible to
build an antenna which is frequency independent, yet reasonably efficient and
directive, and there are also the effects caused by the chamber itself. On
the receiving or sensing side, the frequency response of a small sensor is not
ideal, and its output is furth@r modified by the losses in the miniature semi-
rigid coax used to make the sensor, the miniature connectors that may have a
VSWR as high as 1.5:1, and the 50 or more feet of cable from the sensor to the
recording equipment. The transistor preamplifiers with their input VSIJRSof-
2:1 will also introduce amplitude variations if their inputs are not properly
padded, and a 4 dB attenuator is generally inserted to reduce the mismatch at
the input. Finally, there is the network analyzer. When properly locked on
to the frequency, the accuracy of this instrument is well within the accuracy
desired of the final data; but sometimes due to the wide range over which the
frequency is swept, plus the presence of harmonics generated by the power
amplifier (or even noise per se), the instrument fails to lock and produces
erroneous output. For the A-D conversion and the data processing, the accuracy
is orders of magnitude better than in the other parts of the system, and is of
no concern.
.
To obtain meaningful data from these measurements, it is obvious that th~? F<*components must be calibrated. The critical ones are those on the paths
followed by the reference and measurement signals from the directional coupler
(ahead of the antenna) to the network analyzer. In the case of the latter
signal, the path includes the antenna, chamber, sensor, cables, connectors and
preamplifier, and with so many elements it is obviously impractical toL)(o’
29
calibrate them individually. The system (including sensor) is therefore
calibrated as a whole and it is this information which is used in processing
the data.
The calibration consists of mounting the sensor fn the image plane and
recording the inctdent field over all three frequency bands. Mounting the
surface sensors (see
forward, but the bui’
attention. For each
trough was cut in a ‘
Figure 12) and the MGL-1 and ACD-1 was relatively straight-
t-in sensors on the small cylinders required special
of the three cylinders with side probes, a cylindrical
/8-inch thick metal plate so it would rest snuglyon the
side of the cylinder. The trough was cut just through the plate to allow the
probe to project through the Totally plane surface, and the entire structure
was then mounted in the image plane. For the cylinder with the top probe, a
circular hole of the same diameter as the cylinder was cut in a metal plate,
the cylinder pushed through until its top was flush with the plate, and the
structure mounted in the image plane as before. Wherever appropriate, joints
and cracks were sealed with metallic tape prior to measurement.
On completing the calibration ofa probe, this same probe with all its
cables and connectors attached is mounted on a model. The system is now in-
spected to make sure that the fragile probe has not been damaged, and that the
cables and connectors have not been strained or distorted in a manner that
would Vitiate the calibration. If everything appears alright, the measure-
ments are performed on the model at first one station and then another. (In
the other hand, if at any stage the probe and its associated cabling is
damaged, repairs must be made, and the system then has to-be recalibrated
priorto the next measurement.
2.8 Data Reduction
When allowance is made for repeated measurements caused by equip-
ment breakdowns and human.errors, the study required almost 500 measurement
30
runs, and to keep track of these a log book is maintained listing models,
stations, field components, frequency bands, calibrations, etc. On completion
of a group of measurements, the 9830A calculator is used to normalize the
fJ
measured fields to the incident field (calibration) values, and the reduced
data are then stored back on the cassett~. To avoid the possibility of acci-
dentally erasing the raw data, this is stored in the odd files on the cassette,,
and the reduced data on the next adjacent (even) file. Using the 9830A calcu-
lator as a remote ccmputer terminal, the reduced data”are then transmitted to
the central University of Michigan computer where it is further processed,%-.,
leading ultimately to the form of plots presented in Section 3. Each such
plot has a set of characters in the top right hand corner identifying the
model, station, etc., as well tisgiving the file name where the data from which
the plot was generated is stored. In addition to plots, the data can be printlsd
out, written on magnetic tape or punched on cards.
g==.
31
3. DATA
The surface current and charge data are
three devoted to the cylinder models and one
presented here in five groups,
each to the body of revolution
and 747 aircraft. Each section provides such needed information as the phase
reference plane and frequency scales used and, in addition, contains a summary
table giving the figure numbers for the various measurement situations.
Six data sets (two models over each of three frequency bands) are required
to generate a transfer function. The data are stored on magnetic tape and
the file format is:
1.
2.
3.
4.
5.
6.
tsG
1
FILENAME (4A4)
Comments (18A4)
Comments (18A4)
TITLE used in plotting (18A4)
FMIN, FMAX, AMPMIN, AMPMAX, PHASEMIN, PHASEMAX, NN
(4F8.3, 2F8.2, 15)
F(l) AMP(1) PHASE(I) F(2) AMP(2) PHASE(2) F(3) AMP(3)
PHASE(3) (3(2F8.3, F8.2)
. . . . F(NN) AMP(NN) PHASE(NN)
where NN is the number of data points in the set. Table 1 is a listing of
a typical file.
9
32
—.-. —.- . . .. -—- ---- . . ----- . . . .
....>:>>>>;>:>...:>.....:>>>>>..>
:>>>>:>;>>
1~3456789
1011121314151A171s192021>9.,....~~?4252627292?30?)132333435365738594041424344454647484?5051
TABLE I: lLLUSIKAllUN Uh UAIA >Ll
J2929747 SrF/Tr JTl?EIAND l?J, FSPIO/12/77, KY460
0+9820,9821.0131.0441,076101071+1381,169l,~ool,~3i1.2631,2941.3251.3561,3871+4181.449l.4E31”-1.5121 *5431.5741,6051,6361*6681.6991.7301.7611 .7?21.8231.0551 *8861,9171.9481.9792.0102,041200732,1042.1352 ,16.52.197~,2~8~,2602,2912.3222.3532,384
2.405 1*3031,303 -92,101 +358 -96,601*435 -97*9O1*439 -97*3O1.3?3 -101*4O1,545 -95*9O1.656 -996401+706 -96,001.811 -101,301,932 -9s.402.l@4 -105.202.118 -97,902:355 -104,602,213 -102,30~* 735 -102,402.606 -106.302.965 -105.403, 027 -111.103*311 -10’?,403.412 -114.503.548 -111.403,917 -116*6O4,027 -119*5O4,365 -120,704.446 -122.905,000 -126,004,943 -129.205.346 -129,005,888 -134,805.875 -138.006.516 -139,806.668 -146,906,761 -151.407*379 -155*7O7*345 -162,307,482 -164.707*907 -173.407.621 -178,407,586 178,107,638 172,207*413 168.907.499 163,606,982 157*4O6.871 156,906,902 152,106,.546 147.80
8,017 -179.50 101.400,992100241 ,05s1,0861*1171.1481.1791*2111,2421 +2731.3041,3351.3661,3981.4291.4601.49i1.5221,5531.5841.6161,6471,6781.7091.740107711.8031,8341,8651,8961.9271,9581,9?02.0212,0522,0832$1142.1452,1762,~082,2392,~70
2,3012.3322,3632.395
1.380 -94.601,36S -95*5O1 *355 -99.401,452 -100,901*479 -91 ,5010641 -96,801.600 -100.301 *799 -98,(501 *799 -96.502.051 -97.801,968 -98,002.291 -100.60-),239 -105.602.393 -IOO*1O2,716 -106.402.673 -10s$003,020 -10S.203.062 -111,?03,334 -110,603*451 -113.003,681 -113,504,036 -118.904.0s5 -12O*1O4,395 -119,704.592 -122.805,000 -127,204.909 -131*1O5.623 -129.305.808 -137.2o5,916 -136.206,699 -144.006,637 -147.307,047 -152,407*447 -1!57.307,396 -162.6074743 -166,308.017 -176,207,464 -179,507,709 176*VO7,551 171*1O7*430 167.407,621 161,106.887 155,607,063 156.*4O6,730 149,s06,353 147,10
1381.0031,0341.0651,0961*1271*1591,1901,2211*2521,-1~3
1,3141,3461.3771.4081.4391.4701.5011 *5331,5641,5951 *6261.6571,6881.7201.7511.7821,8131.8441,8751.9061.9381,9692,0002.0312,0622.0932,1252.1562.1872.2182,2492,280~,31-J
2,3432,3742,405
1.324 -96,101.439 -97.101,455 -97.501,486 -99.!501.459 -91.f?o1.657 -100.1301,667 -96,!;01.820 -100.:!01,782 -96.!502.188 -103.,101,928 -99.202.3Y3 -103.002*143 -103.,10p,~~~ -100.:502*594 -1OEI,!;O2.805 -104.!;03,097 -105,:!03,199 -108,(~03*327 -113,003.499 -112.;io3.837 -115,(,03,981 -117,’)04, 236 -116,[}04.426 -124,00 .4.786 -123,(105,023 -129,305.093 -130,?;05.808 -131.[)05*701 -139.006.180 -138,:;06.808 -146,;’06,683 -148,407.194 -153.:!07.295 -160.407.362 -162,(,O7.816 -168,:;07,016 -177.IiO7,S86 lal,~.o7,727 174.307.534 170, :io7.413 166.(,07 * 295 159,:’06,808 137,(106.966 155,E:06.761 147*(O6,223 145,EI0
3.3
3.1 Cylinders *
Of the three types of models considered, the largest amount of
data was obtained for the cylinder, and for presentation purposes it is
convenient to subdivide these data into categories corresponding to the -
measurements in simulated free space (F/S), and in the presence of perfectly
conducting (GP) and 10SSY (LGP) ground planes. The measurements were made
at four locations along the cylinder, and these are listed in Table 2.
TABLE 2: CYLINDER STATIONS
Station
+5D
L/4
-5D
Measurement
J
J,Q
Q
I Q
Location I(see Figure 6)
near bottom of cylinder
center of cylinder
near top of cylinder
I top of cylinderI
For the free space case, the measurements were made at O“, 45°, 90b, 135°,
and 180° azimuthal positions, while for the perfectly conducting and the
Iossy ground plane cases only the 180° measurement was made. The azimuthal
angle is measured clockwise when viewed from the top of the cylinder, with
P = O at the front (toward the transmitting antenna) and 0 = 180 at the back
(in the shadow region). The phase reference plane is at the front of the
cylinder, and the data are presented as functions of ka, where k is the
wavenumber and a is the cylinder radius. To show more explicitly the resonant
behavior of the cylinder, such as the resonant frequency and the height and
the width of the peak, the resonant region data are also presented on an
34
4!9@ expanded scale. For these plots, cleaning and slight filtering were applied
on the data to remove some of the noise introduced by the equipment.
3.1.1 Cylinder in Free Space
The data presented for cylinders in free space are summarized in
Table 3. To simplify the-presentation, the four curves of data relating to
the same measurement are presented under the same figure number, but subdivided
by letters a and b’ designating the full plot amplitude and phase, and w-!
the expanded plot amplitude and phase, respectively..
TABLE 3: CYLINDER- FREE SPACE
I STA J/Q
b+5D J
Cl L/4 J
,)L/4 Q
II -5D Qt
I T QI
*
19 I 20
24 25
29 I
30 I
90°
Figure 16
21
26
Each figure has two parts:
a) amplitude and phase, full plot
b) amplitude and phase,”expanded plot;:...,,:.~<.
do
35
12.0
U.o
0.0
Oo. c
0.0
-100.0
-200.0
0.0
CYL +!$0 O FS 1 C1G67.6S,71,K220S
\–12 DEc 7’7 UH
1.0 2.0 3.0 U.o
CYL +5D O FS I C1867,69,71.K2203
11 NOV 77 UM—.-O.u 1.0 2.Uu
3.0 U.o s
Figure14a, CurrentonTcylin&r at STA:+5D;0 = 0°, free space.
36
12.0
z. HIHO2w=!- 8.0
U.a
O.c
CYL +50 O ?S J C1971,69,137
7 RUG 76 Utl—. -.0 0.1 0.2 0.9 O.u 0.s
200.0 —.
C7L +5D OFSJ C1971,69.67
100.0
-100.(
-200.CRUG 78 Uli
0.0 0.1 0.2 0.s O.u --(
-.3
,5
Figure14b. Current on cylinderat STA:+5D;b = o“! freespace(expandedscale)’37
18.0
12.0
U.a
o.a
CYL +S0 US FS I [email protected],85. .K2l7l
\,, -7-T-’-tl IiDv 77 UN
2aa.o
lao.o
-100.0
-200.0
0.0 1.0 2.0 3.0 u.a #.
CYL +5U US FS X C1961,69,65. .K2l7t
11 Hov 77 U14
0.0 1.0 2.0 S.(I U.o
o
5.0 0KA
Ffgure15a. Current on cylfnderat STA:+5D;9 = 45”, free space.
38
18.0
12.0
H/H
5°
U.o
0.0
..— ..——— --CYL +SD @U5 fS J C1961.6306S
0.0
200.0
100.0
-100.0
-200.0
0.1
\
7 RUG 70 UPI—..0.2 0.9 O.u 0.!5
CYL +5D ●U5 FS J Clesl.eis.$s
\
7 RUG 70 Ukl—— . .-. .- -- a ,, n.O.u 0.1 (7.2 U.a U.u w. 5
KA
~fqure15b. Cumnt on cylfnderatSTA:+5D;0 = 45°, free space (expandedscale).
39
16.0
12.0
Q.o
0.0t
200.0
100.0
-100.0
-200.0
I
\11 Nov 77 Un
} 1.0 2.0 3.0 U.a s
CYL +50 90 FS I C1957.55.K21E$5
P
1
11 NOV 77 LIB
o
0.0 1.0 2.0 KA S.o U.o S.o
Figure16a. Currenton CY1friderat STA:+5L3;0 * 9Q”, free space.
40
,
b .U
1200
H/H*
0.0
U.o
0.0c
200.0
100.0
0.0
100.0
-200.0c
—
CYL +S0 ●00 FS J C1057,55
J 0.1 0.2 0.3 O.u 0.5
CYL +50 s90 FS’ J Cl 7,55
b“
\
7 f3ucl 76 Ull
2 0.1 0.2 0.3 O.u 7.5
KA
Figure16b, Currenton cylinderat STA:+5D;P ~ 90°, free space (expandedscale),
41
12*Q
a.o
%.0
0.0[
2fJo. t
100. C
-loo. a
-200.0(
CYL +s0 135 Fs 1 C1Q4Q,51,S3,K2159
It!tl Hov 77 UH
) 1.0 2.0 S.(J U.o s
CTL +5C) 135 FS 1 Cf949.5i.59.K21Ss
%.
o
1.0 2.0 M S.o U.o 5.0
Ffgure17a.Cdrrenton cylinderat STA:+5D;~ B 135°, free space.
42
u!o
12.0
O*O
H/H.
U.o
0.0
@l –200.0. .
100.0
O.u ~ 0.1 0.2 0.3 O.u 0.5
,,
CYL +50 ●135 FS J C1SU9,S1*53
7 RU13 76 un——
0.0
-100.0
-200.0
CYL +50 ●1S5 FS J C19U9,51*53
%
7 Ruo 78 UH.-0.0 0.1 0.2 0.3 O.u 0.s
K4
Ffgure17b, Current on cylfnderit STA:+5D;6 = 135”, free space (expandedscale),
43
b-lN
WIw
6.0
HfHo
U.o
0.0c
200.0
SOo. o
0.0
-100.0
-200.0c
CYL +50 160 FS 1 C10U7,U5, U!),C23U7,K2I5S,C2351
11-NUV 77 UH
o 1.0 2.0 9.0 U.o 5.0
ICYL +5D 180 FS I C1947, U5,U3.C29U7,K21 5S.
\ ‘1.
11 NOV 77 UHo 1.0 2.0 KA 9.0 U,o m.
Figure18a. Current on cyltnderat STA:+5D;P = 180”, free space.
44
12.0
8.0
H/H~
U.o
0.00
200.0
100.0
0.0
100.0
—CYL +50 ●180 FS J C19U7,U5,U3
7 RUG 78 UH> 0.1 0.2 0.3 O.u T. 5
---CYL +50 OIE FS J Ci9U7,U5.U3
L
7 RUG 78 UHo.o— 0.1 0.2
.—.ox O.u
,..
5
w
FigureIllb. Current on cyl{nderat STA:+5D;B_= 180°, free.space (expandedscale).
45”
12.0
8*C
Iwo
U.c
0.0 L
CYL L~ @ FS 1 C2025.27. 29.K2231.3S,35
200.0
100.0
-100.0
12 t(uv 77 Un
0.0 1.0 2.0 S.o U.!3 S*O
-200.0
CYL LU O FS 1 C2025,27, 29,K2291.33,9S
tI Nav 77 UH,-O.v 1.0 2.0 u S.o U.o 5.0
FfgurcIga. Current ,.gn cyl fnderat S7A:L/4;9 = 0°, free space.
46
4!!)o
.
:
6*O
H/H.
U.o
“0.0
CYL L/U CO FS J C2025,27,28
7 Iiuo 78 Un
-0.0~.t .–>,=:
0.2 0.si !’
O.u 0.5
200.0
100.0
0.0
-100.0
-200.0(
CYL L/U CO F9 J C2025,27,29
7 RUG 76 Un.- - .,
0 O.i 0.2 U.a U.u ‘.
M
r-z+
,“
Figure19b. Current on cylinder at $TA:U4;II“ V, free space(expandedSCalr).47
12.0
8.0
Ii/H.
Q.o
O.a
200.0
100.0
0.0
-100.0
-200.0
CYL LU Ufi FS I C2023.21, 1B,K222Q.27,2S
12 U(IV -)7 Un
o S.O 2.0 9.0 U.o 5.0
CYL LU US FS I C2029.21. i9.K2229,27,25
0,0 1.0 2.0 M S.o U.o !
Figure20a. Current on cyl~nderat STA:L/4;LI= 45°, free space.
48
f-’- .2
)
4!9@
8.0
H/H ~
U.o
0.0
200.0
100.0
0.0
-100.0
-200.0
CYL L/U sU5 FS J C2D29.21 ,19
0.07 RUG 78 un—.. — —. . . .
0.1 0.2 0.3 O.u 0.5
—-——-—-—--CYL L/U *U5 FS J C2029.21.19
7 RUG 78 Utl —0.0 0.1 0.2 0.3 O.u o
K4
5
F{qure20b, CurrentOn cylinderat STf!:l/If;B = 45°, free space (expandedscdle),49
u.a
u.a
CYL LU S0 FS I C201~.15, 17,K221Q,2i,23 1
O.c0.0 1.0 2.0 9.0 4.0 3.0
200.0
100.0
-100.0
-200.0(
23
1 1.0 2.0 w S.O U.o 5.0
-..
I
e
F{gure21a. Current on cyl{riderat STA:L/4;O = 90°, free space.
50
4!)o
8.0
WH ~
U.o
0.00.0
7 RUG 76 UEI—
200.0
100.0
0.0
-100.0
-200.0(
CYL L/U 090 FS J C201S,15,17
0.1 0.2 0.3 O.u (
CYL L/U s90 FS J C201S,15,17
7 fluo 78 Utl—
D 0.1 0.2 0.3 O.u 0.!5M
....–-
Figure21b. Currenton cylinderat $TA:L/4;$ = 90°, free space (expandedscale),51
10.0
e.c
2.0
0.0
CYL LU 135 FS 1 C2R11,0$. 07,K2217,15. I !3
~77 UH0.0 1.(I
—.2.0
●S.o U.o !5.0
200.C
!Oo.c
-100.0
-200.0(
CYL t.U 13S FS I C2011.09, 07,K2217. t5.l 9
k11 Not’ 77 UH
3 1.0 2.0
Figure22a. Currenton cylfnder
KA S.o U.o :
at STA:L/4;$3= 135°, free space,
52
0
..-
.
@
,)
10.0
8*O
6.0
H/H.
4.0
2.0
0.00
200.0
100.0
0.0
-100.0
-200.0
CYL L/U ●1S5 FS J C2011,09.07
7 RUG 78 un.—-—0 0.1 0.2 0.3 O.u —0.5
—
CYL L/U 9195 FS J C2011,0g,07
7 RUG 78 UM
0.0 0.1 0.2 0.3 O.u c
K4
Figure22b. Currenton cylinderat STA:L/4;6 = 135°, free space (expandedscale),
53
F-
5
too
8.0
6.0
H/HO
4.0
2.0
0.0
200. C
100.0
CYL LU 160 FS I C2001,0S, 05,K221i,0D,07
1
~77 Uli0.0 ,1.0 2.0 S.o U.o ,.
0.0
O*O
-100.0
-200.01.0 2.0 KA 3.0 U.o
0
g)S.o
Ftgure23a. Currenton cylinderat STA:L/4;@ = 180”,free Space,
54
10.0
e.a
2.0
0.00.0
0g) 200.0
100.0
-100.0
-200.0
CYL L/U ●180 F!l J C2001,03,05
0.1 0.2 0.s O.u (
CYL L/U 0180 FS J C2001,03.05
.
7 RUG 70 U1’1
0.0 0.1 0.2 0.9KA
O.u 0.5
Ffgure23b, Curr@nton cylinderat STA:L/4;b = 180”, free space (expandedscale).
55
10.0
ti. o
2.(3
0.0
200. C
100. C
-too. c
-200.0
CYL LU O FS O C1U25,27,29,K2257.67,US
0.0 1.0 2.0 3.0 U.() 5.0
Ii NoY 77 UH[ 1.0 2.0 KA 3.0 U.o 5.0
figure24a. Charge cylfnderat STA:L/4;0 = 0°, free space.
56
%“
io. o
0.0
8.0
En/Eo
U.o
2.0
0.0
CYL L/U ●O FS Q C192S.27,2Q
./
7 RUG 76 UPI.
—O.v 0.1 0.2 0.9 O.u 0.5
200.0
100.0
0.0
00.0
-200.0
CYL L/U sO FS Q C1925,27,29
[
O.u 0.1 0.2KA
0.9 O.u 0.5
F’.?
F!WM ?!4. Char@ on cylinder at 5TA:V4:$ “ 0’,free space (expandedscale).57
0.0
6*O
z~u En/EoE* U.aJ&==
2.0
O*O
LU U5 FS a cae2s.2i, la,K22ss.65,ua
200.0
100.0
a.o 1.0 2.0 9.0 U.o S.o
-100.0
-200.0c
I
‘1LU US FS Q C192S.21.18,K2
11 HOV 77 UH
3 i.o 2.0 KA 9.0 U,o S.o
Ffcj F{gurc25Q. Chargecylinderat STA:L/4;@ = 45°, free space,
58
S.o
6.C
EnlEo
U.o
2.0
0.0
100.0
-100.0
‘.. J
-200.0
\
CYL L/U ●U5 FS Q
/
C192S,21,1O
‘-’-’b7 RU13 78 UH
0.0 0.1 0.2 0.9 O.u ().5
7 Ruo 76 uFl
0.0
F
0.1 0.2 0.!3 O.u 0.!5
K4
~Ure 25b. Chargeon cylInderat STA:L/4;O = 45’, free space (expandedscale).
..
59
8.0
6.0
z
~E/E0 no=1- U.ci;sa
2.0
0.01)
200.0
-100.0
-200.0
LU 90 FS Q CIQIS. i5.17,K225S,63.73
LU 9 S Q C1913.15. 17.K2253.63, 73
/+
11 NOV 7? UH
0.0 1.0 2.0 K4 S.o U.o 3.0
-...
0
o
Figure26a. Chargeon cylfnderat STA:L/4;p = 90°, free space.
60
8.0
6.0
E /Eno
4.0
2.0
0.0c
200. C
100.0
0.0
-100.0
-200.0
CYL L/u .90 FS Q C1E13,1S,17
! 0.1 0.2 0.9 O.u 0.5
CYL L/U ●90 FS Q c1919, i5,17
0.0 0.1 0.2 0.3 O.u o
w
FigureZ6b. CMr9e cyl{nderat STA:L/4;9 = 90”, free space (expancJerJ scale).
61
!3
6.0
8.0
z
U.o
2.0
0.0
LU 13S FS @ C1911.0U.07, K22Sl.61.7~
F.10. .N(JTJ77 UH
u
0.0 1.0 2.0 9.0 U.o 5.0
200.0
100.0
0.0
100.0
-200.0(
\
,
LU 135 FS Q C1911.09, 07.K225t .61. 71
\
12 NOV 77 Utl
r 1.0 2.0 KA 3.0 U.o
o
00
Ffgure27a. Charge on cy~lnderat STA:L/4;0 ‘ 135”, free sPace.
62
0.0
6.0
EnlEO
4.0
2.0
0.0
—
CYL L/U ●135 Fs a clall,08,D7
0.0
7 RUG 78 UFI— — ,—
200.0
100.0
-100.0
-200.0
0.1 0.2 0.3 O.u 0.5
CYL L/U s135 FS Q C1911,09,07
r’
7 RUG 7s Utl
o 0.1 0.2 0.9 O.u 0.5
u
F\yure27b, Ctwr9d on cylinderat STA:L/4;B = 135”, free space (expandedscale).
63
10*O
0.0
4.0
2.0
0.0
..
LU 180 FS Q C1901,0S,65PK2Z40,80,6Q
200.C
100.0
0.0 1.0 2.a S.LI U.11 S.@
0.()
00.0
O*U 1.0 2.0 F/l S.o U.o 5.0-200.0 12 ffov 7? LJH
.- . .
Ffgure28a. Ckrge on cylinderat STA:L/4;0 = 180”, free space.
64
---lU. U
0.0
8.0
En/Eo
4.0
2.0
0.0
CYL L/U ●180 FS O C1901,09.OS
7 RUG 78 UH-.
0.0 0.1 0.2 0.3 O.u 0.5
00.0
0.0
-100.0
-200.C
CYL L/U e180 FS Q C1901,03.05
7 RUG 75 uPl—.-- A ,!
o 0.1 0.2 U.3 v.%
KA
Ffgure 28b. Chargeon CY1fnderat STA:L/4;0 = 180°, free space (expandedscale),65
16.0
!2.0
En/Eo
8.0
U.o
0.0a
200.0
100.0
0.0
-100.0
-200.0
CYt. ’80 0 FS Q C20U3,U5. U7.71,60.U7
a 1.0 2.0 S.o U.o 5.0
J“$L
-50 0 FS Q C20U9.U5. q7.7!,69.67
I
11 NOV 77 Ill!
0.0 1.0 2.(I M S.a U.o 5.0
Ftgure29a. Charge on cYlfnderat STA:-SO;0 = o“, free space.66
16.0
12.0
En/Eo
(01)
8.0
U.o
0.0“a
200.0
100.0
0.0
-200.0c
-.
CYL -50 ●O rs o/
C20US,U5,U7
7 RUG 78 urno 0.1 0.2 0.9 O.u o
—
CYL -50 ●O FS O C20U9.U5,U7
7 RUG 78 UM
2 0.1 0.2 0.3 O.u c
M
Fi91 Figurt29b. Clwrgehn cylinderat STA:-5D;6 = O“, free space (expandedscale).
67
P?=:
5
1s.0
12.0
En/Eo
8.0
U.o
O.c
200. C
100.0
-100.0
-200.0
CYL T O F3 Q C20SS, S3.S1,81,63,6S
0.0 1.0 2.0 KA 3.0 U.o ,
CYL T O FS 9 C203S. S3.31.61.63,65
12 NOV 77 UH.-
ir
0
O.u 1.0 2.0 M 3.0 U.o 5.0
Ffgure 308. Charge on cylinder at STA:T; free space.
68
.
i6.o
12.0
En/Eo
8.0
U.o
0.0a
200.0
100.0
0.0
100.0
-200.0c
7 RUG 78 un
o-.
0.1 0.2 0.3 O.u c
CYL TFSO C2095.99,31
7 HUG 78 U14
5
> 0.1 0.2 0.3 O.u 0.5u
Ftgure30b, Chargeon cylinderat STA:T;free space (expandedscale).69
3.1.2 Cylinder Near Perfectly Conducting Ground Plane
The current was measured at the back (0 = 180°) of the cylinder
near the base (.STA:+5D) and the charge at the top (STA: T) for various
cylinder to ground plane spacings. The spacing h is measured from the
center of the cylinder to the ground plane and is expressed in terms of
the radius a. Data are presented for the full range of ka measured and
in expanded form for the resonance region. Table 4 summarizes the data
presented.
TABLE 4. CYLIF+DERNEAR PERFECTLY CONDUCTING GROUND PLANEf
h,I
1.5a ~
2a
5a
1Oa
20a
40a
I
J. STA: +5D I
Figure 31
32
33
34
35
36
Each figure has two parts:
iQ, STA: T I
nFigure 37
38
39
40
41
42
i
a) amplitude and phase, full plot
b} amplitude and phase, expanded plot,–-.
70
. 80.0
80.0
z..J H/HO
za$- Uo. o“
20.0.
o.a
-)(D, 2oo. a
ioo. a
-100. [
CYL +50 1S0 0? I K2S67,60, 71.C2S57,55.5S
77 UH
D 1.0 2.0 3.0 U.o 9
\
\
CYL +50 180 GP I K2867 69,71.C2357,55,53
\
12 140V 77 UH
0.0 1.0 2.0KA
S.o U.o 5
Figura31a. CurrentJonCY1inderat STA:+5D;!J= 180”,h = 1.5a,near perfectlyconductinggroundplane.
71
.. -.,..
0
o
‘ 80.0
60.0
20.0
0.0c
200.0
ioo. o
-Loo. o
-200.0
CYL ●SD ●100 H=l.!5R G? J K2667,69.71
e RUG 78 UH
0.1 0.2 0.3 U.u 0.5
0.0
8 RUG 7a un0.9 0.1 0.2 0.3 O,u c
--3
iKA
%Ig@e 31b.,Currenton CY1inderat STA:+5D;0 = 180”, h = 1,5a, near Perfect~Yconductinggroundplane (expandedscale). 72
.
80.0
Uo. o
H/H.
20.0
0“. o
CYL +50 180 GP I K2705.0S, K2S7S,C2S59,8 1,11
~.77 UH
200.0
100.0
0.0
100.0
0.0 1.0 2.0 9.0 U.o 15.0
‘)● -200.0O.u
CYL +50 180 GP I K2705.03. K2E73.C2359
A
12 NOV 77 UH,,. ...
1.0 2.0 m 3.0 U.o
. ..-
!5.0 ●,Ffgure32a, Current on cylfnderat STA:+5D;@ = 180°, h = 2a, near perfectly
conductinggroundplane.
73
o“4, .+=
40.0
z
2000
0.0
o
E RUG 78 IJH
0.0 0.1 0.2 0.s O.u 0.s
200.0
CYL +!5D 8180 tl=2R GP J K270S,0SIK262S
100.0
0.0
-100.0
0 -200.0O*U
.,
8 RUG 78 UH.
0.1 0.2 0.3 O*U O*5
KA. Ffgura32b. Current on cylInderat STA:+5D;d = 180’, h = 2a, near perfectlyconductingground
plane (expandedscale).74
60.0
@o. o
20.0
.
100.0
-100.0
-200,00
CYL +S9 180 G? I K2707,09, 11,C2SUE,8706~
A\- 77 UN
1.0 2.0 3.0 U.o <.0
\
\\
CyL +5D 180 GP I K2707.09, 11.C2989.87,135
)
Figure
1.0 2.0 M !!.0
12 NOV 77 UH
U.o <.0 ●33a. Current on cylinderat STA:+5D;jl= 180”, h x 5a, near perfectlyconductinggroundplane.
75
60.0
Uo. c
H/H~
20.0
0.0
.200. C
10Q. O
-100.0
-200.0(
0.0
CYL +!50 ●t60 Hs5@ GP J K2707.0!l, il
9 RUG
O.f 0.2 0.s O.u 0.5
—
CYL +5U ●180 H=5R GP J
b
9 RUG 75 UM
Figure
0.1
33b. Currentonplane (expanded
0.2 0.3 O.u
Kk
cyl fnderat STA:+5D;1!= 180°,h * 5a, near perfectlyconductingscale}.
76
ground
0.5
. . ..
50.0
Uo.o
30.0
H/HO
20.0
10.0
‘ 0.0
CYL +SD 180 GP I K2717,15, 1S.C2971,73,C2Q G
0.0 1.0 2.0 S.o U.o ;.0
200.0
100.0
0.0
-100.0
0@i -200.0
0.1 7 LIEC 77 UH
o 1.0 2.0 L4 3.0 U.o !5.0 0Ffgure34a. Current on cylinderat STA:+5D;0 = 180”,h = 10a, near perfectly
conductinggroundplane.77
00.0
60.0
20.0
0.0
200.0
100.0
-1 OO. G
-200. C
0.0 0.1
CYL +5D 0100 H-1OR G? J K27i7. lS,13
0.2 0.3 O.u 0.s
cYI. +50 ●180 H=1OR G? J K2717.1S,19
a RUC! 78 un.
0.0 0.1 0.2. 9.3 O.u U.s
●
✎✌
KA
Ffgure34b. Current on cylinderat STA:+5D;@ “ lW, h : l@I, near perfectlyconductinggroundplane (expandedscale).
78
, 20,0
H/H.
$.0
4.0
0.0
CT!. +SU 180 W I K2710.21,23, C2U07.0B,09
0.0 1.0 2.0 3.0 U.o ~
@ 200.0
100.0
‘\
-100.0
@ J-200.0
I
——0.0
# I+5D 180 GF I K2718.21. 23.C2U07,05 .09
I
~ti 7 DCC 77 UHJ1.0 2.0 L4 S.o U.o 5.0
o
----
Ffgure35a. CurrentonCY1\nderatSTA:+5D;0 x 180°,h = 20a,near perfectlycon&ctfng groundPIane.
79
20.0
10. C
12.0
H/H.
8.0
U.o
0.0
200.0
100.0
-100.0
-200.0
CYL +50 ●180 H-20R GP J K2719.21,2S
9 RUG 78 Utl0.0 0.1
—,0.2 0.3 O.u 0.5
CYL +5U s180 H=20R GP J K2719.21.23
0.0 0.1 0.2 0.3 O.u 0.5M
Ffgure35b. Currentcylinderat STA:+5D;B = 180°,h = 20a, nearperfectlyconductinggroundplane (expandedscale).
80
SO*O
80.0
20.0
.
10.0
0.0
CYL +50 tk30 OP I K272Q,27.25
Ilk, 7 DEC 7? lllf—
200.0
100.0
-100.0
-200.0
0.0 1.0 2.0 9.0 U.o E
I—
CYL +50 180 GP I K2729.27.25
0.0
e.’
\
7 OEC 77 Utl
KAo
1.0 2.0 3.0 U.o 5.0
Figure 36a, Current orIcylinderat STA:+5D;0 x 180°,h x 40a, near perfectlyconductinggroundplane.
81
CYL +S0 s180 tl=UOfi 0? J tf272e,27,25
0.0 0.1 0.2 0.9 O.u
\
RUG 70 UM—...
o 200.0
100.0
0.0
00.0
0-200.0
●
CYL +S0 ●160 H=UOR G~ J K2729,27.25
0.0 0.1
Ffgure36b. Currenton cylfnderplane (expandedscale).
0.2
Iu
0.3
c
‘1
\/ 9 RW 7S UH
O.u c
At STA:+5D;@ = 180”,h - 4CM, near Perfect~Yconductfw ground%2
—
s
5
w-2-
30.0
En/Eo
20.0
10.0
0.0I
CYL T G? Q K2553.51. U9.C2US5.53.5 t
3 1.0 2.0 3.0 U*O S,o
200.0
CYL T ‘&F Q K2559.51. U9.C2U55.59, 51
100.0
-100.0
&-200.0
\ &15 UEC 77 Un
o 1.0 2.0 w 3*O U.o s
,, Ff@re 37a. Charge on cylfnderat STA:T;h = 1.5a,near perfectlyconductinggroundplane,
83
-
. 40.0
30.0
En/Eo
20.0
10.0
0.0c
200.0
100.0
-100.0
-200.0
, CYL T H=l. Sft G? O K2S5!l,51,Ua
;2 0.1 0.2 0.9 O.u (
CYL T H=l.5R GP Q K2S53,51,U$I
‘1)”S flUG 78 UM
.0 0.1 0.2 0.9 0.4 was
KA
, Ftgu~ 37b. Chargeon cylinderat STA:T;h - 1.5a,nearperfectlyconductinggroundplane.-(expandedscale],
J’ .34
*U. O
U8. O
En/Eo
S2. O
16.0
0.0
CYL T G? Q K2555,57, 59,C2U57.58,6 1
12 NoV 77 UH——— .-.— - . ..——
200.C
100.C
-100.0
-200.0
0.0 1.0 2.0 3.0 U,o s
CYL T 13P Q K2555,57,59.C2Y57.59,61
.
15 DEC 77 UH..—— —5.0
Figure38a. Chargeon cylinderat STA:T;h = 2a, near perfectlyconductinggroundplane,
85
,,.,
●
o
8U. O
oUa. o
0.0
0 200.0
100.0
-100.0
0 -200.0
CYi. T H=2R G? Q K2S5S.57,S9
0.0 0.1 0.2 0.!3 O.u 0.5
CYL T tl-2fl GF G K2S55.S7.59
0.0
F
w
9 RUG 76 UFl— .—.
M
38b. Chargeon c I!nderat STA:T;h = 2a, near perfectlyconductinggroundplane!(expandedscale .
86
0.1 0.2 0.9 O.u 0.5
gure
.
. Cu. o
f48*o
En/Eo
32,0
16.0
--–0:0
[
200.0
100.0
-100.0
-200.00
CYL T GP Q K25BS,63. 61,K2US7.E5,C2U6S
b \ 12 Nov 77 UM—o 1.0 2.0 S.o U.o S.o
9
15 DEC 77 urn. ,,. .) 1.0 2.0 M 3.0 U.o :
Ftgure”39a, Charge on cylinderat STA:T;h = 5a, near perfectlyconductinggroundplane,
. . .
o
87
, 6U. O
Ua.o
!6.0
0.0
0 200.0
100.0
!0. o—- 0.1 0.2 0.3 O.u a.5
0.0
-100.0
-200.0
CYL T H=SR GF Q K2S8S,l13.%1
CYL T li=5R GP Q K256S,63.BI
A -. .- -- . .O.v
F
U.1 U.d U.Y O.u U.5
K4
qure 39b. Charqeon cylfnderat STA:T;h = 5a, near perfectlyconductinggroundplane(expandedscale).
88
.
50,0
Uo. o
z 30.0.~
:~ En/Eo~x5
20.0
10.0
‘“’0.0
CYL T 9P U K2587,89, 71.K2U60.71,7S
_l > No~ Un 770.0 1.0 2.0 ?!.0 U.o 3.0
200.0 —.
100.0
0.0
-100.0
-200.00.0
\ \
CYL ~ G? Q K2587.69, 71,K2U69,71. 73
L
115 DEC 77 Ull
1.0 2.0 M 3.0 U.o <,0 @
Figure40a. Charge w @inder at STA:T;h = 10a, near perfectlyconductinggroundplane,
89
So. c
Uo. c
So. a
En/Eo
20.0
10.0
0.0
CYL T H=1OR Gf a K2S07,89,71
0.0
200.0
100.0
-100.0
0.2 0.s O.u 0.:
CYL T H=1OFI 13P Q K2S87.B9,71
\
-200.0 s Rua 78 UH
0.0 0.1 0.2 0.3
K4Ffgure40b. Charge on cylfnderat STA:T;h = I(!.a,near perfectly
(explmfedscale].90
0.4 0.s
conductinggroundplane
92.0. .
2U*0
8.0
‘0.0o
zw=
200.0
100.0
0.0
-100.0
1.0 ._.::.2.o. . ._ 3.0 U.o <
0.0 1.0
CYL T GF Q K2805.03. 01. K2505,03,01
I
15 DEC 77 UH
2.0 KA 9.0. U.o :
Figur~f]:~e,Chargeoncyllnderat STA:T;h x 20a, near perfectlyconductingground
91
a
32.0
2U. O
En/Eo
16.0
8.0
0.0
0200.0
100.0
O.c
-1 OO. C
im
I -200. C
CYL T H=20R G? Q K260S,03,01
0.0 0.1 0.2 0.?s O.u
CYL T H-20R Gf’ Q K2605,03*OI
0.0
0.5
&
0.1 0.2 0.s O.u 0.5
~fgure 41b. Chargeon cylinderat STA:T;h ● 204, near perfectlyconductinggroundplane(expandedscale).
92
200.0
100.0
-100.0
Uo.o
32.0
18.0
8.0
CYL T 6P R K2607,00,11
lU NOV 77 UHO*O0.0 1.0 2.0 3.0 U.o 5.0
-200,0
CYL T GP Q K2607.09,11
&-!*-—
I I
lU Nov 77 UH9
D 1.0 2.0 ~ 9.0 U.o —5.0
Ff@re 42%, Chargeon cylinderat STA:T;h = 40a, near perfectlyconductinggroundplane.
93
200.0
100.0
GMa~
0.0umu=L
-100.0
-200.0
0.0 0.1 0.2 0.9 O.u 0.5
CYL T H=UOR GP Q !(2807 ,09,11
U RUG 76 Uttc0.0 0.1 0.2 0.9 O.u c
KA
Figure42b. Chtrge*oncyllnderat STA:T;h = 4C&, nearperfectlyconductinggroundplane(expandedscale).
94
93,1,3 Cylinder Near Lossy Ground Plane
The current was measured at the back (~= 180°) of thecyljn(jer ‘\
\near the base (STA: +5D) and the charge at the top (STA: T) for various
L
cylinder to ground plane spacings, The spacing h is measured from the center
of the cylinder to the ground plane and is expressed in terms of the radius a.
To be consistent with the data for the cylinder in the free space case, and
near the perfectly conducting ground plane, the data presented here are also’*5
plotted as a function of ka. However, due to the frequency dependant complex.
permitivity of the lossy ground plane material, the measurements made on
the small and the large cylinders at different frequencies but corresponding
to the same ka values are not expected to match. The data definitely indicate
this at ka = 0,5. For O c ka c 0.5 data were obtained on the small cylinder..+-while-for ka > 0,5~ they were measured on the large cylinder. Table 5
sunmarizek the data presented,KY
‘TABLE 5: CYLINDER NEAR LOSSY GROUND PLANE.,.-.. .—.r
h J, STA: +5D Q, STA: T .
1.5a Figure 43 Figure 49
2a 44 50
5a 45 51
1Oa 46 52
20a 47 53
40a 48 54●
Each figure has two parts:-,
a) amplitude and phase, full plot
b) amplitude and phase, expanded plot
95
. 18.a
t2. a
H/H.
e.a
U.a
0.0
CYL ●5D 180 LOP ! K2781,63,8S,C2U33, 35.37
200.C
100.C
-100.0
O.u 1.0 2.0 3.0 U.o 3.0
a-200.0
CYL +50 180 LGP I K2761.89,65. C2U33, 9s.37
lU Nov 77 Un
0.0 1.0
Ffgure43a. Current on cyl
2.0 u S.o U.o S.o
riderat STA:+5D;0 = I&lO*,h = 1,5a,near lossygroundplane,
96
“20.0
ois. o. .
Si. o
0.00
6?200.0
100.0
0.0
-100.0
. CYL +S0 s180 H=l.SR LGP J K27L11,83,65
) 0.1 0.2 0.9 O.u 0.5
CYL +5D ●180 H=l.5R LGP J K27E1,83.65
10 RUG 78 UH.-V.ci 0.1 0.2 0.3 O.u 0.5
M
Ffgure 43b, Current on cyl fnder at STA:+58; 180°, h = l,$a, neir 10SSy
ground plane (expandedscale).97
.—
0
a
Su. o
o Uo. o
20.0
$0.0
0.0
CYL +50 l@O LGP 1 K27!j9, 57, !4S.C21J3i.2g,27
200.0
-100.0
-200.0
0.0 1.0 2.0 9.0 U.o s
CYL +50 180 LGP I K27S9.57, 5S.C2U31,2Q,27
0.0 1.0 2.0 KA S.o U.o 5
figure 44a . Current on cylfnderat STA:+5D;0 = I@I”,h = 2a, near 10SSYgroundplane.
98
0
0
.-
0
40.0
So, o
10.0
0.0U.u 0.1
----1
a1)200.0
00.0
O.(Y
-100.0
-200.0
0.2
.,.. .. .-a. .
0.3 o’. u
...
0.5
-=,;+ <$ ---....,, —. ;.:-;-- ,.:-
CYL +5i) 0180 H=2R LGP J K27.59,57,55
10 RUG 78 UH
O.u 0.1 0.2 0.9 O.u 0.5
M
.FfgureUb. Currenton cylinderat STA:+5D;S = 180”,h = 2a, nearlossYWWund plane (expanded~~le).
‘ 80.0
0 Qo. o
So. o
H/H.
20.0
10.0
0.0
CYL ●SD 180 L(i? 1 K27U0, L11.S3,C2U21.2S.2S
q’.. .uLAl@f-77 UH
o 200.0
100.0
O*O 1.0 2.0 S.9 U.o S.o
-100.0
0-20a.o
29.25
lU Uov 77 Un,,.
0.0 1.0 2.0 FA !!.0 U*O
‘h -=-
.
*!s.0
Ftgurc45a. Currat on cylinderat STA:+!iD;B = 180”, h = 5a, near loMy groundplane.
lW
4?,.. So. o
40.0
90.0
H/H~
20.0
10.0
0.0
—CYL ●SD ●180 H-SR LGP J K27UQ,51,S3
200.0
100.0
0.0
%0.0 0.1 0.2 0.3 O.u --i
-100.0
-200.0c
—
CYL +50 ●1130 H-5R LGP J K27UQ,51,53
v
10 RUG 70 UH. . . —.-U 0.1 0.2 0.3 O.u 0
KA
-P-
5
Figure45b. Current on cylinderat STA:+5D;@ = 180”, h = 5a, near 10SSYgroundplane (expandedscale).
101
‘ 60.0
0 40.0
10.0
O*O
CYL +5~ 160 LO? 1 K27U7, US,U!l,C2Ul@,t7,15
77 Un
o 200.0
100.0
-100.0
0.0 i.u 2.0 9.0 U.o s
@-200.0
180 LC
tU NOV 77 UH0.0 1.0 2.0 Kh S.o 4.0 5,0
o
Figure46a. Current on cylimlerat STA:+5D;0 = 180”,h = 108, near Iossygroundplane.
102
So. o
UO*O
10.0
CYL +50 ●180 H-1OR LGP J K27U7.U5.US
. .0.,0 ..—..
.,. 0:0–”” “’--, 0.1 0.2 0.9.- O.u ;.5
rI@)200.0
100.0
-100.0
“),’
[*-200.0
0.0
CYL +5D @180 H=1OH LGP J K2747,U5,U3
10 RUG 78 Utl.—
0.2 0.3KA
F
0.1 O.u c
gure 46b. Currenton cyl{nderat STA:+5D;~ = 180°, h = 10a, near10SSYgroundplane (expandedscale).
103
●5-
20.0.,
1s.0
e.o
U.o
0.00.
200.9
100.0
-100.0
-200.0a
CYL +50 100 LU? I K2S27, S9.U1.C2U00. 11. 13
F
II
1.
:YL 5D 180 LGP I K2797.98.U1.C2U0
1.0 2.0 KA
FREQUENCY
gure 47a. Current on cyl i rider at STA:+5D;
r.-
0
Itu Nav 77 Un
3.0 U.o 5
IHHE1
0 = 18U0, h = 20a, near lossygroundplane.
o
104
20.0
1s.0
10.0
H/H~
!5.0
0.0
CYL +50 ●180 H=20R LGP J K27!17,S9,U1
O.u 0.1 0.2 0.9 O.u 0.!5
200.0
100.0
-100.0
-200.0
CYL +50 ●180 H=20R LGP J K2737,99,UI
\
lLFIUG 78 Uli——
e
e
0.0 0.1 0.2 0.9 O.u 0.5
M
Figure 47b. Currenton cyllnderat STA:+5D;~ = 180°, h = 2(M, near lossygroundplane (expandedscale).
105
z 2U. O
~u
: H/tlo.
=E
t8. o
0.0
O*Go
200.0
100.0
Gug
0.0wmu=&
-100.0
-200.0
CYL ●5O 180 I.GP 1 K27SS,SS.!I1
h, tu Uav 77 Un
1.0 2.0 9.0 U.o :
CTL +59 i60 LGP X K2735.33.81
lU Ilov 77 Ull
. .
0
e
. .
0.0 1.0 2.0 K4 S.o U.o 5.0
FfgureM&. Currenton clyfmkr at STA:+5D;II= 180”,h = 40a, near Iossygroundplane.
106
SO*O
20.0
H/H.
10.0
0.0
100.0
0.0
-100.0
- .)—
-200.0
CYL +50 ●180 H=U08 LG? J K27SS,S3,31
10 RUG 78 U)l.O.(I 0.1 0.2 0.9 O.u 0.s
.O.u 0.1 0.2 0.3 O.u (M
o
05
Ftgure48b. ‘Currenton c lind rat STA:+5D;@ = 180°,h = 40a, near lossygroundb{ane faxpandedKale).
107
‘ to. a
e.a
u.a
2.0
0.00.0
cYL T LE? E K28Q3,US.U7,K2S31 ,33, 3S
77 Utl
200.C
iao.c
-100.0
1.0 2.0 9.0 U.o S.o
P
\
v:YL T L6P U K28U3. U5,U7,K2591,9S, 95
lU NoV 77 UH
2.0 KA S.o U.o 5*OI 0.0 1.0
Figure49a. Charge on cy’inderit STA:T;h * 1.5a,near 10SSYgroundplane,
108
‘“),1
10.0
8.0
8.0
En/Eo
%.0
2.0
0.00
200.0
100.0
-100.0
-200.0
CYL T H=l.5R LGF O K28U3,U5, U7
10 RUG 7S UH
o- 0.1 0.2 0“.9 n.u ;.s
CYL T H=l.5R LGP Q K26U3.45,47
10 FiuG 70 Ufl——
0.0 0.1
Ffgure 49b. Chargegruund plane
•8 0.2 0.3 O.u U.5
KA
on cyl{nderat STA:T;h = 1.5a, near lossY(expandingscale).
109
‘20. a
1s.0
!$. G
U.a0.0
200.0
100.0
0.0
-100.0
.77 Ull
1*O 2.0 S.o U.o 5.0
CYL T LGP Q K2641.39.9?, K2S29,27, 25
,
15 NOV 77 UH. .—0 S.o 2.0 M 3.0 U.o 5.0
Ffgure908. Charge w cylfnderSTA:T;h = 2a, near 10SSYgroundplane.
110
20.0
15.0
~ En/Eoeg’b-,
-1&z
...,.
.,..”
10.0
5.0
0.0
200.0
lCO. O
-100,0
-200.0
—
CYL T H=2R LGP O K28U1.39,S7
O.u 0.1 0.2 0.3 O.u 0.!5
CYL T H=2f7 LGP Q K28U1,39.37
*
o
L.
10 RUG 70 UH-—..0.0 0.1 0.2 0.3 O.u 0.50
w
Figure50b. Chargeon cylfnderat STA:T;h = 2a, near IOSSY
groundplane (expandedscale),77tIll
Uo. (
30. C
En/Eo
20.0
!0.0
0.0(
00.0
0.0
-100.0
6 -200.0Q
CYL T LGP Q K2631.SS.35, K2S18,21.23
1.0 2.0 S.o U.o S.O
CYL T LGP Q K263t,99, 95,K2518,21. 29
1!5 140V 77 UH
) 1.0 2.0 IL4
Figure51a. Chargeon cylinderat STA:T;h s 5a,
3.0 U.o S.o
tear 10SSYgroundplane.
112
30.0
En/Eo
20.0
10.0
0.00
200.0
100.0
0.9
-100.0
-200.0
—
CYL T H=SR LGP Q K2831,33,3S
I
\
\
\
.-.—0 0.1 0.2 0.3 O.u 5
——..—-. 7-—
--. . . CYL T H=SR LGP O K2831.33.35 o
I
10 RUG 78 UH,—0.0 0.1 0.2
KA0.3 O.u 0 5 0
Ftgure51b, Charge on cylinderat STA:T;h ● 5a, near 10SSYgroundplane (expandedscale), 113
.-
, U8. O
CYL T LSP R K2828,27. 25,K2517,1S ,13
16.0
Et.o
O.ac
200.(
100.(
-1OO.C
-200.0
Ih
IS NoV 77 UH
1.0 2.0 9,0 U.o s.
II
o
0.0 1.0
CYt. T LGP U K2629.27. 25.K2Fi17.i5. l 9
b\
2.0 KA 3.0
1S NOV 17 UH
U.o 5.0 0
,.
F{gure52a. Charge on cylfnderat STA:T; h = 10a,near 10SSYgroundplane.
114
!50.0
40.0
10.0
~,.o.o..,
2.00.0
100.0
0.0
-100.0
-200.0(
—
CYL T H=IOR LGF a K2629,27,25
o’ “’ 0.1 0.2 0.3 O.u 0.!5
——.. ——- —— ...—. -----
CYL T H=1OR LGP O K2629,27.25
I
~
~
I
-1
.— —10 RUG 78 Ull
..—.— .———- —-0 0.1 0.2 0.3 O.u 0.5
0
?&
K4
Figure52b. Chargeon cylinderat STA:T;h = 10a,near 10SSYgroundplane (expandedscale).
115
CYL T LGP Q K261tl. 21.23.K2Si07.00 ,11
100.0
&iw= 0.0wmaE
-100.0
@
i -200.0
0.0 1.0 2.0 9.0 U.o ,.
CYL T LGP IJ K2619,21. 23.K2S07.09.! 1
1S NOV 77 UHI 0.0 1.0 2.0 KA 9.0 U.o n.
Ffqure53a. Charge on cylfnderat STA:T;h = 20a, near Iossygroundplane.
o3
116
‘ 2U.O
18.0
12.0
En/Eo
8.0
.0.0
CYL T H=20R LGP O K261S3,21,23
0.0 0.1 0.2 0.9 O.u (
I CYL T H=20R LGP Q K2819.21.23
100.0
i
-100.0
-200.010 RUG 28 U!..
0.0 0.1 0.2 0.3 O.u 0.5
M
o
F{gure53b. Chargeon cyllnderat STA:T;h = 20a, near lossygroundplane (expandedscale).
117
,0
.Uo. o
So. o
10.0
0.00
200.0
100.0
-100.0
-200.0
CYL T LGP O K2E17,1S,1S
.
_!!h____ ~~~~ 1S NW 77 UH
) 1.0 2.0 ‘ 9.0. U.11 5.0
1“
CYL T LGP U K28t7,15,t3
15 NOV 77 UH
0.0 1.0 2.0 la 3.0 U,o s
Ffgure54a. Charge on cylinderat STA:T;h = Ma, near lossygroundplane.
118
Uo.o
30.0
En/Eo
20.0
10.0
0.0
.CYL T H=UOR LG? O K2617,15,13
●
;
200.C
100.0
0.0
-100.0
.
(@/-200.0
CYL T H=UOR LGP Q K2817,1S,13
10 RUG 78 UH0.0 0.1” 0.2 0.9
MO.u “i. 5
Figure54b, Cturge on cylinderat STA:Tih = 40a, near lossygroundplane (expandedscale).
119
o3.2 Body of Revolution
The data are presented as functions of the full scale frequency usjng
the full scale dimensions shown in Figure 8. This same figure also shows the ,
location of measurement stations, as follows:
F/S - Fuselage, Side
WR/T - Wing Root, Top
WC/T - Wing Center, Top
WT/T - Ming Tip, Top
Lp
The current component measured was the axial one. The data are for simu-
lated free space, and near to perfectly conducting and lossy ground planes.
ln the latter cases, the spacing between the model and the ground plane is
a/2 where a is the (maximum) radius of the fuselage.
●The phase reference is
at the top of the fuselage”,midway along its length. The electrical properties oof the lossy ground plane are given in Section 2.2.
The data presented are summarized in Table 6.
TABLE 6: BODY OF REVOLUTION DATA
STA J/Q F/s GP LGP *
F/S J Figure 55 Figure 59 Figure ~1
WR/T J 56
WC/T J 57 59 62
WT/T Q 58
ksee section 3-1.3 on problems when scaling lossy ground planemeasurements.
12rl
i6. o
12.0
U.o.
(,
0.0
BR F/S FS J BRS027, 29.31,BR2959,5 1,U9I
200..0
100.0
8 NoV 77 UH
O*O S.o 16.0 2i
0.0
-100.0
BR F/S FS J BR3027, 29,31,BR295S.5 1,U9
(& -200.0$ NOV 77 Uli
0.0 8.0 18.0 :Z.oKA
o
.=..
Figura55. Chrrent on My of revolutionat $TA:F/S;free space.
121
I
12.0
8.0
U.o
200.0
100.0
O.a
-100.0
-200.00
UR lfR/T ?S J 0R3067,6S,6S,UR3025.23, 21
~ WV 77 UH
o %.0 16.0 24.0
6Fl HRfT FS J BR3067. 65.63,BR9025.23. 2i
‘1
) 8.0 16.0 2U.O
K.4Figure56. Cbrrenton body of r-evoluttonat STA:MR/T;free space.
122
0
=.=
12.0
8.0
U.o
200.0
100.0
0.0
-100.0
-200.0
.
OR HC/T FS J BR3057. 50,61.BRS009. I 1.1S
S NOV 77 UH
D 8.0 16.0 =.0
,. —>:.bym,>-~. ~,.. ,;z. .-i
‘LBR HC/T FS J BR9057,59, 61.BR3009.1 1,1S
S NUV 77 UH—0.0 8.0 16.0 2Q
KA
Ffgure57, Currenton body of revolutionat STA:WC/T;free space.
123
Q
28.0
20.0
10.0
5.0
0.00
2Q0. O
100.0
0.0
-200.0
CM HT/T FS U BlllSU3,US,U7.BfiS015, 17, 1S
i.
f
) 8.0 18.0 2U.O
6R itTfT FS U 5Ri5U9.U5,U7.BR9015, i7 ,18
,.
8 Uov 77 UK0.0 13.o
lot113.O 2U.O
Ffgure58. Chargeon body of revolutionat !3TA:KT./T;free space.
124
, Uo. o
30.0
10.0
y.. .0.0I
,. 0
200.0
100.0
0.0
100 .0
-200.0c
. . .
0 NOV 77 UHo 8.0 16.0-... Z.o
BR F/S GP J BR3097, 35,9S,BR2955,57 ,59
8.0 16.0 2U.OM
Ffgure59. Currenton body of revolutionat sTA:F/S;near Perfectlycon-ductinggroundplane.
125
2U. O
16.0
5.0
0.0c
200.0
100.0
0.0
-100.0
-200.00
BR UC[T 0? J BRS05S. S3,S1,BR3007,0S, 03
1
J
8 uav 77 uH8.0 16.0
BR HC~T GP J B139055.5S.51, BF13007.05, 09
-*L--
Ffgure60, Currenton body of revolutionat STA:WC/T;near perfectlycon-ductinggrwnd plane,
126
16.0
12.0
U.o
0.0..-!
200.0
,.
100.0
-100.0
—
BR F/S LOP J BR30S9. U1,U3,BR296S.8S. 61
9 NOV 77 UH.
o“ ~. B.O 18.0 21,‘?
--.—. .—
,. BF! F/S LGP J BF13039, U1.U3,BR2965.83 ,6!-..—
B NOV 77 UH.- -..
0.(7 8.0 15.0 Zv.ou
Figure61. Chrrenton ‘*Y of revolutionat STA:F/S;near 10SSYgroundplane,
127
-200.0
0.0
8.0
2.0
0.0
200. C
Ioo. c
-100.0
-200.0
BU ilCfT LGP J EiR30U9,U7, U5,BFt2967,EiQ. 71
9 NOV 77 Ui(
0.0 8.0 16.0 2U.O
BR HC/T LGP J Bf190U9. U7,kS.Bi32967,69, 71
9 Nu’# 77 UHIt-l . . ..- -.,
9w-
0
/ KA
Fl~ure62, Currentan body of revolution at STA:h’C/T; near 10SSY ground plane.
128
, 10.0
8.0
U.o
.2.0
-&&o=.o,c
l--*)
7U7 f/8 FS J J2E29,27, 25,J286S,6fI, 61
9 NOV 77 UM
2 10.0 20.0 :) I-k.,. >fi- ,. .— ..–. .-—.i%. . -.. x,.
200.0
..:. L.
100.0
-100.0
-200.0c
7U7 F/S FS J J26129. 27.25,J2865.63. 81
9 Nov 77 UH
> 10.0 20.0 ~ c1
M
D
.;-.. .-’.’,
Ff~re 63. Current on 747 at STA:F/S; free space,
129
3.3 747 Aircraft
These data are also presented as functions of the full scale frequency,
using the dimensions shown In Figure 10. The measurement locations were
F/S - Fuselage, Side
WR/T - Wing Root, Top
WC/T - Wing Center, Top
WT/T -Ming Tip, Top
and are indicated in Figure 10. The current component measured was again the
axial one, but it should be no~ed that on the wing this component is along the
bisector of the wing (see Figure 10). The phase reference for all of the data
is the top of the fuselage midway along its length. The data are for $~mu-
Iated free space, and near perfectly conducting and lossy ground planes. The
spacing between the model and the ground plane is a/2, where a is the fuselage
radius at its midpoint.
Table...7sucmaarizesthe data provided.
TABLE 7: 747 ~ATA.8
STA J/Q FS Gp LGP *
F/S J Figure 63 Figure 67 Figure 69
WR/T J 64●
WC/T J 65 68 70
WT/T Q 66
b
1.-.
i
o
Asee section 3,1,3 on problem when scaling ~OSSy ground plane lM2aSUN?lIK!lltS
130
#*o
6.0
2.d
0.00.0
100.0
-100.0
7U7 MR/T ?8 J Jft8Sl,SS,8S007, 00Cll
10 Nov 77 urn
10.0 20.0
7U7 Iififl FS J J2Q91,99. 95.07,0S.11
10 NOV 77 UM
D 10.0 20.0 30.0
M
Figure 64. Current on 747 at STA:UR/T; free space.
131
- :4m.
“ 12.0
8.0
U.o
747 MCf7 FS J J2019,21.5S.%~.UG
0.0 8 NOV 77 UH. .
200.C
100.0
-100.0
-200.0c1
0.0 10.0 20.0
7U7 HC[T FS J J2819,21,5s,51,UQ
IA
a NoV 77 UJI
10.0 20.0 30,Qe
KA
Figure 65. Current on 747 at STA:UC/T;free space.
132
.18.0
12. C
En/Eo
6.0
4.0
O.a
200.0
100.0
-100.0
7U7 14T/T FS Q J2855.57. 50.17, 15,t3
*
=%’
D . ..—- 10.0 20.0 310.0
!&i
O.v 10.0 20.0 90.0w
Figure 66. Current on 747 at STA:YT/T;free space.
133
2!5.0
20. C
to. a
!3. C
O.c
200.0
100.0
-100.0
-200.0(
7U7 F/S G? J J2SIG,21.2S, J2@57,UQ,7 I
10.D 20.0
7U7 F/S GP J J29t9.21. 29,J213Ei7,69,7S
So.o
)
●
10.0 20.0 SC
KA
Figure67. Currenton 747 at STA:F/S; near perfectlyconductingground plane.
134
o 9
20.0
1s.0
H/H.
10.0
S.o
200.0
100.0
O*O
-100.0
-200.0
7U7 MC/T GP J J2S29,27.2S. US,U5.U7
NOV 77 UM—10.0 20.0 3(
—. . ...> . .. . .
747 HC{T GP J J2829,27, 25.U9,q5,U7
9 Nov 77 UYI0.0 10.0 20.0 30
KA
Figure 68, Current.on 747 at STA:UC/T; near perfectly conductingground plane,
135
,0
0
10.0
a.o
4.0
2.0
0.(2
200. (
100. (
-100.0
-200.0(
7U7 F/S LOP J J2fii7. lS,lS,OS,OS,Ol
10 NOV 77 UH.- . .--O.u 10.0 20.0 3L?.O
\
7U7 F{S LGP J J2917.15, 19.OS,OSI.01
\
L10.0 20.0 30
L4
Ffgure 69. Currenton 747 at STA:F/S;near 10SSY ground plane.
136
0.0
8.0
,..
2.0
0.0(
200.0
,.. .
100.0
.
GMI=
0.0uma=&
-100.0
-200,0
7U7 NC/T LO? J J28S1, !IS,S5,U1,39,S7
10 Nov 77 Uno 10.0 20.0 3
10 NOV 77 Ull-.
10.0KA
20.0 30.0
,:’
Figure 70. Current on 747 at STA:WC/T;near 10SSY ground plane.
-137
4. CONCLUSIONS
A total of 57 transfer functions have been presented. A glance at these
Indicates that the data points are too crowded near the resonance regions and
do not show explicitly the details of the resonance characteristics. This is
due to the linear scale used to show the results over the wide band of frequen-
cies required. Plotting the frequencyon a log scale would have increased the
resolution at the lower frequency end but at the expense of that at the higher.
Some of the curves have blank areas where data points are missing. In most
“casesthese were caused by an i~abi’lityto retrieve the recorded data from the
cassette tapesl and the situation is made worse if calibration data required
to reduce a set of test data are lost, There is also the problem of noise. As
discussed in Section 2.7, the noise-like appearance of the raw data is due to
the nonuniform frequency response of-the system. The calibration procedure
removes most of this noise.’ Some of the more important conditions that a facility
must satisfy in order to successfully calibrate it are:
The physical layout must be fixed apart from the models;
The sampling frequencies must be the same for the test and cali-
bration data;
The receiver or network analyzer must have a linear response.
-g5=--
. .
The fact that not all of these requirements weremet has some effect on the data.#
The large physical layout required long lengths of cable in the crawl
space under the chamber, and their electrical lengths can change due to varia-
tions in humidity and temperature. Temperature changes can also affect the
frequency stability of the generator; andas a result of such instabilities,
the frequencies at which the calibration data are taken may differ from those
of the test data taken at a later time.
138
Problems were experienced with the network analyzer, and we did not become
aware of these until the cylinder measurements were completed. The slow but
progressive failure of the harmonic converter (HP 8411A) made its response non-
linear, and also reduced its ability to track the signals properly. Much of
the noise in the cylinder data is attributable to this. The equipment was repaired
prior to measuring the body of revolution and 747 aircraft, and resulted in ~.
much improved data for these models. .,
With the cylinder models, the data for ka ~ 3 may be questionable due to
the nonuniform nature of the illumination associated with the image plane, and
the variation is most pronounced in the data taken on the top of the cylinder.
It,,should also be recognized that the test mo.dels,,werescaled but the sensors. .~.,. .were,not? and the effects of’’this are clearly evident in the measured data for
the body of revolution models’(for example, Figures 58 and 60). In addition,
the distance of a cylinder from the perfectly conducting or lossy ground plane
The jumps in the data for some cylinder modelswas ,difficultto control exactly.,
are attributable to some slight variations in the distances (for example, Fig-
ures 47 and 53). —
Our final remarks concern the large noise-like spikes present in.some of
the,data. Most of these are due toexperimental and/or equipment shortcomings
and, being spurous, should be ignored in any comparisons of the data with the
results of other experimental,ornumerical investigations.
139
.
APPENDIXA. THEORETICAL ANALYSIS OF REFLECTIONS FROMA FINITELY CONDUCTINGGROUND PLANE
We here examine the reflection of plane electromagneticwave at norms?
incidence on a ground plane consisting of a slab of finitely conducting material.
It is required that over the model frequency range 0.4 to 4.0 GHz the ground
plane simulate the electrical properties of the earth immediately beneath the
Air Force Weapons Center Oipole Facility at Kirtland Air Force Base. The full
scale frequency range beingl.5 to 15 M1-fz,the required scale factor for simu-
lation is about 267.
A.1 Earth Constants at Full Scale Frequencies
The results of the experimental investigation at 1 to 100 MHz described
in [5] indicate that the earth inxnediatelybeneath the Dipole Facility contains
three layers of contrasting electrical properties withfn 3 m of the surface.
Subsurface resistivities at the site range from 2 to 82 ohm-m depending on
the layer and the frequency of interest and average dielectric constants range
from 6 to 6 x 10b. The permeabi’
of free space.
The electrical characterist
the Dipole Facility are shown in
ity of the earth may be assumed equal to that
cs of the top two layers of the earth beneath
Table A-1. The relative permittivity (or the
dielectric constant) and the resistivity shown in Table A-1 are the measured
values”obtained from [5], and the other quantities represent the corresponding
calculated values. The relative complex permittivity of the medium is
c s’ - is”= (Al)
where
~’ is the dielectric constant
ll=(YE— WC0
u is the conductivity in mhos/m
(A.2)
140
-..
TABLE A-1. ELECTRICAL CHARACTERISTICS OF THE EARTH BENEATHTHE DIPOLE FACILITY [5]
Depth of ThicknessLayer Fm~;;;cyof Layer(m) (m} [Q~m) (U?m) “ ‘“ (:)
1.5 48 2.083x 10-2 19 2500.0- 0.15 0.15 2.87
15 44 2.273x 10”2 13 27 0.87
0.15 -0.18 0.731.5 73 1.370X 10-2 16 164 3.54
. 15 65 1.538x 10-2 11 18 1.07a
iii
)(“ u is ,theradian frequency
1 ““ -9‘Kx’o Farad/m is the permittivity of free space‘o
and p= ~ is the resistivity in ohm-m.
With this notation the skindepth d is given by
..
‘here‘Mt-lz ‘s
We shall
of the values
68 1 ~—.‘MHz @
the frequency in MHz.——
assume that the earth constants to be
for the top two layers, and these are
p- .
(A.3)
.,,
simulated are the averages
shown in Table A.2.
141
TABLE A-2. AVERAGE VALUES OF THE EARTH CONSTANTS AT THE FULL SCALEFREQUEN~IES
Frequency p
(GHz) (n-m) (U;m) c’ ‘1’ (:)
1.5 61 1.639 X 10-2 18 197 3.23
15 55 1.818X 10-2 12 22 0.97
A.2 Simulated Ground Plane
For a scale factor of 267, the required values for the electrical
com$ants of the simulated ground plane at the model frequencies are shown
in Table A.3.
TABU A-3. REQUIRED VALUES OF THE ELECTRICAL CONSTANTS FORTHE SIMULATED GROUN!IAT THE MODEL FREQUENCIES
,.
Frequency Q c1
(Gtiz) (Q-m) (lJIm) “ ‘“ (m)
0.4 0.23 4.4 18 197 1.2%X 10-2
4.0 0.21 4.9 12 22 3.62 X 10-2
.F5-
,----.-
142
.
.
Emerson and Cuming, Inc. makes a material under the trade name Eccosorb
LS-26 which has E’ = 10 and u = 0.6~/mat 1.0 GHz. The material is available
in 2 by 2 ft. panels 3/4 inch in thickness. The conductivity of this material
is about l/8th of the,desired values shown in Table A-3, and the measured
values of the electrical constants of Eccosorb LS-26 at 0,5 and 5 GHz are
shown in Table A-4.
TABLE A-4. MEASURED VALUES OF VARIOUS ELECTRICALCONSTANTS FOR ECCOSORB LS-26
-i--
.—
Frequency p 6
(GHz) (Q-m) (u~m) “ ‘“ (m)..—- .-
-0.5 1.67 0.6 20 20 3.04 x 10-2
5.0- 0.71 1.4 5 5 0.6 X 10-2
In the light of the above results and for lack of a more appropriate
material, the decision was made to construct our simulated ground plane from
a 2-1/4 inch (= 5.7 cm) thick layer of Eccosorb LS-26. The thickness corres-
ponds to 9.526 and 1.886 respectively at the high and low ends of the frequency
range.,
.
A.3 Reflections From The Simulated Ground PlaneG:
In the present section we discuss theoretically the reflection of a
plane electromagnetic wave incident normally on an infinite slab of Eccosorb
LS-26. Three arbitrary media are considered as shown in Figure A-1, where
the various fields are~)to
d in the z-direction,
in the three media can
displayed. Medium 2 is an infinite slab of thickness
With assumed time dependence e‘Wt, the field quantities
be written as follows.
143
(1)
‘1
Ei, Hi
>
<
Er, Hr
/
Figure A-1. Reflection and transmission of ~lanewaves by an infinite slab at nohalincidence.
-iklz‘~ EEi=Eoe ,Hi=—
UIJ i1
-ik z ik zEm = E~e 1 2 E~e 2
+ ~+e-iqzik2zHm==
22- E~e
i k3z k3 ik3z
‘t =E3e , Ht=re3
(A.7)
o
-.-
(A.4)
(A.5)
(A.6)
144
●
✎
where the propagation constants kl, k2, k3 in the three media are defined by
with
kj =a.- ifi.,JJ
j = 1, 2, 3
=&laj
..,
Assuming Vj =
.
(A.8)
1/2
(A.9)
(A.1O)
P. and using Eq. (A.2) we can rewrite Eqs. (A.8) and (A.9) as
where k. = ~ is the propagation constant in free space.
(All)
(A.12)
Application of the boundary conditions at z = O and d-to the field quan-;–;
tities in Eqs. (A.4) to(A.7) leads to the following~-:I.-..
EO+$=E;+E;
E. - El = Z12(Ej- E;)
lA!i
e-i k2d {k2d -ik3d
El e +E~e =Ee3
-ik2d ik2d -ik3d (A.13)El e -E~e = ‘23E3 e
from which the reflection and transmission coefficients of the infinite slab
can be determined asi2k2d
El (1 - Z23){I + Z12) + (1 + Z23)(1 - Z12)er = —=
E. i2k2cf(1 - Z23)(I - Z12) + (1 + Z23)(I + z12)e
ik3d‘3T=y= 4e
ik2d -tkzcl0 (1 + Z12)(l + Z23)e +(1- zlz)(~ - z23)e
.— ... .. ->
where
..=—. .
Zj=~ , ‘j~’> , j, k =i,2,3,. *j k ,.
1 .-,
Note that
Z.=z =1Jk kj
Z.. Z. = ZijlJ Jk }
For computational purposes it is convenient to define,
.*. W..rkJ “‘jk Zk+zj “ ,-
jk
Using Eqs. (A.8), (A.16) and (A.18) it can be shown that
(Nkaj - ~jak) - ‘(~kaj - ~j~k)
‘jk = (~kaj + ‘jak) - ‘(vkaj + ‘jak)
I=
(A.14)
(A.15)
o(A.16)
(A.17)
(A.19)
o
146
Thus, the reflection coefficient r can be written in the following form
-2$2de-i2a2d
r = ’12 + ’23 e (A.20)-262de-i2a2d .. ..1 +r12r23e -.,. .3-w- .....,.--
where r.k
~
is given,by Eq:(A.19). Observe that if d =-m (i.e.,,medium 3 is,
missing Eq. (A.20) implies-~.=
..“\,\
.(A.21)
;i
A c-hputer program has be~n written to determine lrl~afndarg r as functions
of d under var~ous c~nditions, and theJprograryisl_i~J:Q3~~Sec,tion A.~”..—..—--- -----.L, i \
A.4 Numerical Results and Discussion#-f- . ..).
~---
(0’ Figure A-2 shows 11’Ivs. d for normal incidence on an infinite slab
of Eccosorb LS-26 at two selected frequencies. The curves marked F in Fig-
ure A-2 are for a slab in free space, i.e., when media 1 and 3,are free space,
and the dotted curves are for a slab of infinite thickness. Observe that at
both frequenci~s Irl initially fluctua~es around Irml before asymptotically
approaching Irml. The curves labelled “with absorber backing” refer to the
cases when medium 1 is free space and medium 3 is filled with an absorbing,
material having S’ = 5, c; = 1 at both frequencies.3
With absorber backing the
, slab behaves as though it were infinitely thick at smaller values of d. Fig-
ure A-3 shows the corresponding values of arg 1’vs. d at the two frequencies. #The results shown in Figures A-2 and A-3 indicate that as far as the reflection ‘,
$;,of a normally incident plane electromagnetic wave is concerned, a thickness d
of Eccosorb LS-26 material behaves like infinitely thick slab at 5 GHz and
0.5 GHz for d :2 cm and d ;8 cm, respectively.
As seen from Table A-4 the skin depths of Eccosorb LS-26 at these two fre-
~-j quencies are 0.6 cm and 3.04 cm, respectively, suggesting that a slab of thick-
,) ness d ~ 36 will behave as if it were infinitely thick.
147
o
-2
-4
TmT -6
—L—
-8
-10
F
~r \ = 3.03 dBm
..........
with absorber backing
f = 5.OGHZ
.
1---
2 4 6 8 “--10
d (cm) j ‘
Figure A-2. 1~~ vs. d for an infintte slab ofEccosorb I-S-26.
49t“
(,’
8
.
L!
180
170
160
150
-.
f= 0.5 GHz
4
---- -..
.
.
v arg rm = 162°
2 4 6 8 10
d (cm) _
Figure A-3. Arg F vs. d for an infinite slab ofEccosorb LS-26.
149
1
As discussed in Section 2b we have fabricated ground plane out of a
5.7 cm-thick slab of Eccosorb LS-26. From the results shown in Figures A-2
and A-3, it can be seen that even with d = 4 cm the simulated ground plane
may be considered to be infinitely thick at the upper region of the model
frequency range. At the lower end of the model frequency range ]r~ differs
from Irml by about 0.5 dBwhich is well within the experimental accuracy.
Thus the 5,7 cm-thick ground plane should provide an adequate simulation of
an infinitely thick ground of the same material.
A.5 Computer Program Listing
See next page.
I
9-.?,@
SGFE:GAMMA ,,
. .151 * U.S.COVSRNMINT ?RINTINCOfflCf: 1979-678-432-286