uwb conformal aerospace antennas

7/31/2019 Uwb Conformal Aerospace Antennas

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ULTRA WIDEBAND ANDCONFORMAL ANTENNAS FORAEROSPACE APPLICATIONS

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ULTRA WIDEBAND ANTENNASINTRODUCTION

An antenna is said to be broadband if its inputimpedance and radiation pattern do not varysignificantly over at least one octave.

A transmission system is considered to be UWB inaccordance with the FCCs definition if it has abandwidth greater than 500 MHz, or a relativebandwidth greater than 20%, defined at 10 dB


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ULTRA WIDEBAND ANTENNASTHE SPIRAL AND DISCONE

Spiral Antennas Disadvantages

Balanced Feed Required

Polarization varies with frequency

The discone antenna is a variant of the biconical antenna.This is made up of a cone opposite a metal disk. The feed issupplied by a coaxial cable at the tip of the cone, whichpasses through the metal disk. The disk typically has a radius

0.7 times /4 at the lowest working frequency, the cone anangle of 25 (Stutzman, 1998). This antenna gives a stableradiation pattern over an octave and good matching overseveral octaves. The polarisation is linear and the radiationpattern is similar to that for a dipole.


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ULTRA WIDEBAND ANTENNASTHE DIAMOND ANTENNA

A model which is a hybrid of the biconical antenna and

the discone antenna was proposed for UWB use by Kim etal. (2005).

Instead of a flat disk, a wide-angle ( k = 70 ) metal cone

is used.

This gives excellent broadband matching of 100:1 andacceptable omnidirectionality in the radiation pattern.

One example inspired by this, although not frequency-

independent, is the diamond antenna which is very popularin UWB systems.

This antenna is made up of two opposing triangularplates. The feed point is located between them.


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ULTRA WIDEBAND ANTENNASTHE MODIFIED BOW-TIE

A bow tie antenna was proposed by Kiminami et al. (2004),in which the metal triangles are located on different faces ofthe substrate, in order to obtain greater bandwidth. This givesa reflection coefficient less than 10 dB between 3.1 and 10.6GHz.


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ULTRA WIDEBAND ANTENNASTHE LOG PERIODIC

A type of log-periodicantenna attributed to Isbell usesdipoles set out in a series ofincreasing size.

All the dimensions of the setare scaled by a factor, includingthe separations between theelements.

For optimal operation, eachdipole must be fed at a phasedifference of 180 compared toits neighbours.

At an arbitrary frequency,

there is ideally only one dipole


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ULTRA WIDEBAND ANTENNASTHE HORN

Horn antennas are very popular for UWB

The main disadvantage of the horn antennas is the factthat the gain is not stable over frequency.

They also tend to be electrically large, of considerable size,

typically around one wavelength of the lower operatingfrequency.

Other critical aspects are the reflections produced at theend, and the diffraction at the edges.

A typical technique for reducing this effect is to haverounded edges, which attenuates the side lobes and gives aradiation pattern that is more stable over frequency


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ULTRA WIDEBAND ANTENNASTHE 2D HORN

The best known one in the group of 2D Horn Antennas is the Vivaldiantenna, introduced by Gibson in 1979.

This can theoretically provide infinite bandwidth, although inpractice this is limited by its size, manufacturing techniques and thetype of feed.

The feed is provided through a microstrip-line and a slot-line.

Good directivity, in the region of 1015 dBi.

The level of the co-polar component and the beamwidth can becontrolled by changing the radius of the curved profile of the

metallic parts.


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ULTRA WIDEBAND ANTENNASTHE PLANAR MONOPOLE

A linear monopole antenna oflength /4 is a resonant antennaand not suitable for UWB.

Dubost and Zisler, 1976, studiedtechniques to increase thebandwidth by widening theantenna.

This provided a satisfactoryresponse to requirements for UWB

and broadband applications ingeneral.

This type of 3D monopole is calleda Planar Monopole Antenna (PMA)over perpendicular ground plane,

or simply a planar monopole, forshort


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Like all monopoles, the 3D monopoles exhibit good phaselinearity (Kerhoffet al., 2001), very high efficiency (Schantzand Fullerton, 2001) and very high bandwidths, for example14:1 (Qiu et al., 2005), can be achieved.

Additionally, techniques may be used to filter out certainfrequency bands.

Their radiation pattern is relatively omnidirectional.

The cost of manufacturing this type of antenna is low.


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One technique for increasing the bandwidth is the use ofdifferent Euclidean shapes.

The most representative antenna of the planar monopoleswith Euclidean shapes is the square antenna (Agrawall etal., 1998). Its bandwidth is around 75%, with VSWR < 2 inthe S-band.

Of all the Euclidean shapes, the circular and elliptical onesgive the highest bandwidths. For example, an optimisedelliptical monopole for which the ratio of the longer axis to

the shorter one is 1.1, provides a bandwidth of 10.7:1


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Computer techniques using Genetic Algorithms (GA), allowmore elaborate shapes to be developed

Another way of studying planar monopoles is by makingmodifications to geometries that have already been studied.

This is the case when the profile of the lower edge ismodified to increase bandwidth, for example by making abeveled notch or cut (Ammann, 2001)


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The use of parasitic elements isone possibility.

This means that elementswithout a wired connection to afeed (i.e., passive) are locatedclose to elements connected tothe feed (i.e., active).

Other solutions based on thesetechniques focus on the case in

which the active monopole isnarrow and the parasite has asquare or rectangular Euclideanshape of known characteristics.


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Another design technique for planar monopoles consists inusing short-circuit pins in the areas with high currentdensity.

In addition to providing greater bandwidth, this is also usefulfor making the antenna more compact.

Bandwidth is increased from 75% in the S-band, up to 110%(Ammann, 2000).

If this is implemented on a dielectric, the size is reduced byup to 50%


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Double feed: This technique is based on using two feedpoints, instead of the more usual one.

The horizontal currents are reduced. A square planar

monopole is proposed by (Daviu et al., 2003) with two feedpoints which are symmetrically placed with respect to thecentre of the antenna.

Cross-polarisation is reduced because this system reinforcesthe excitation of vertical modes.


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ULTRA WIDEBAND ANTENNASTHE 2D MONOPOLE

Full 2D monopoles consist of a metal patch on one face of adielectric board, with the ground plane parallel to it, usuallyon the other face of the printed circuit.

The feed is normally provided through a microstrip linehaving the same ground plane as the monopole. When bothparts (monopole and ground plane) are coplanar on thesame surface, the feed is normally provided by a coplanarwaveguide.


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ULTRA WIDEBAND ANTENNASTHE 2D MONOPOLE

Liang et al. (2005) studied a circular patch antenna with acoplanar waveguide feed, as shown in Figure. This gives abandwidth at 10 dB from 3.27 to 12 GHz.

The dimensions of the patch can be used to control the firstresonant frequency, and therefore the lower end of theband. The radiation pattern remains acceptablyomnidirectional.


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BANDWIDTH

ENHANCEMENTTECHNIQUES FOR THE

MICROSTRIP PATCHANTENNA


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The expressions for approximately calculating thepercentage BW of the RMSA in terms of patch dimensionsand substrate parameters is given by

With an increase in W, BW increases. However, Wshould betaken less than to avoid excitation of higher order modes.For other regularly shaped patches, values of equivalent Wcan be obtained by equating the area with that of the RMSA

Another simplified relation for quick calculation of BW (inmegahertz)

for VSWR = 2 of the MSA operating at frequency fin

MSA BANDWIDTH ENHANCEMENTTECHNIQUES

INTRODUCTION


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The regular MSA configurations, such as rectangular andcircular patches can be modified to rectangular ring [1] andcircular ring [2], respectively, to enhance the BW.

The larger BW is because of a reduction in the quality factorQ of the patch resonator, which is due to less energy storedbeneath the patch and higher radiation.

When a U-shaped slot is cut inside the rectangular patch, itgives a BW of approximately 40% for VSWR < 2 [3].

Similar results are obtained when a U-slot is cut inside a

circular or a

triangular MSA [4,5].


INTRODUCTION


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MSA BANDWIDTH ENHANCEMENT


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PLANAR MULTIRESONATORCONFIGURATIONS


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MULTILAYER CONFIGURATIONS

In the aperture-coupled MSA, the field is coupled fromthe microstrip feed line placed on the other side of theground plane to the radiating patch through anelectrically small aperture/slot in the ground plane. Twodifferent dielectric substrates could be chosen, one for

the patch and the other for the feed line to optimize theindividual performances. A BW of nearly 70% has beenobtained by stacking patches with resonant apertures[6].



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STACKED MULTIRESONATOR MSAs

The planar and stacked multiresonator techniques arecombined to further increase the BW and gain. A probe-fedsingle rectangular or circular patch located on the bottomlayer has been used to excite multiple rectangular orcircular patches on the top layer, respectively [7,8]. Besides

increasing the BW, these configurations also provide anincrease in gain



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APERTURE STACKED PATCH

The ASP (aperture-stacked patch) consists of a large slotand two directive patches. They have attractive characteristicsthat make them suitable for wideband applications as goodimpedance and gain bandwidth, good polarization control,compactness, relatively simple development and, despite its

electrical thickness, it does not suffer from surface waveproblems since the surface wave power is coupled to theadjacent patches and radiated into space.



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ELECTRICAL PARAMETER VARIATION IN THE SUBSTRATEREGION

Kiziltas [10] proposed that the substrate be discretized intoa large number of cubic elements with varying permittivity.Using an algorithm, the layout and permittivity perturbationsof these cubic elements is optimized. Resulting designsrealized with this approach give increased impedance

bandwidths.

Mosallaei [11] also makes use of a technique utilizingsubstrate variations. In his work he utilizes an engineeredmagneto-dielectric material composed of a woodpilearrangement of electric and magnetic materials as thesubstrate.



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Consider a linearly polarized rectangular patch antennaand a substrate that is sectioned into three block-like regions:two that are on the outer regions of the substrate, near theradiating edges, and one that is on inner region of thesubstrate. In order to make the comparisons of these different

designs clear, identical patch dimensions, substrate height,and feed probe location are used.

Two configurations: one where the permittivities in theouter and inner regions were respectively,lower and higherthan the simple substrate permittivity (LHL) and the otherwere there was an inverse arrangement (HLH).

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IMPEDANCE-MATCHING NETWORKS

The impedance-matching networks are used to increase theBW of the MSA. Some examples that provide about 10% BWare the rectangular MSA with a coplanar microstripimpedance-matching network and an electromagneticallycoupled MSA with single-stub matching



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LOG-PERIODIC MSA CONFIGURATIONS

The concept of log-periodic antenna has been applied toMSA to obtain a multi-octave BW.

In this configuration, the patch dimensions are increased

logarithmically and the subsequent patches are fed at 180out of phase with respect to the previous patch [9-12].

The main disadvantage of this configuration is that the

radiation pattern varies significantly over the impedance BW



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SUSPENDED RMSA

The BW of the MSA increases with an increase in h and adecrease in r

The effect of the increase in h and the decrease in r canalso be realized using the suspended-microstripconfiguration as shown in Figure

The patch is fabricated on one side of the dielectricsubstrate, and it is suspended in air with an air gap of D.

The suspended configuration consisting of two dielectriclayers can be replaced by a single layer of equivalent

dielectric constant eq of thickness h + D


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II - CONFORMALANTENNAS


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Aerodynamics can be improved by adjusting the antennas tothe contour of the vehicles

Provide broader beams than their planar counterparts

Less disturbing to the human eye since there are integratedon the structure. This attribute might be useful for urban ormilitary environments.

Conformal antennas are divided into singly and doublycurved antennas, depending on how many curvatures thegeometry has.

CONFORMAL ANTENNASINTRODUCTION - NECESSITY


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Most of the publications study methods of analysis suitablefor non-planar structures.

In many cases, the analysis of conformal antennas can bebased on approximate techniques and when the antennahas very large radii of curvature, it may be often analyzedas if it were planar.

Other important factor for the method selection is theaccuracy and time consumption since, for instance, thecavity model is relatively fast but not as accurate as the full-wave analysis.

CONFORMAL ANTENNASINTRODUCTION - NECESSITY


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This type ofantenna has anearlyomnidirectional

radiation pattern inthe azimuth planeand a dipole-likeradiation pattern in

the elevation plane.The antenna is a

microstrip patchwrapped around a

grounded dielectric

CONFORMAL ANTENNASTHE CIRCULARLY POLARIZED CYLINDRICAL PATCH


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The geometry of the cylindrical stackedpatch antenna, as can be seen in Figure,consists of an inner ground cylinder with aradius of 1.42 cm and two substrates with arelative permittivity of r = 2.3 separated byan air gap.

The inner dielectric has a radius of rinner =1.422 cm and a thickness of 1.8 mm whilethe outer dielectric has a radius of router=1.852 cm and a thickness of 1.6 mm.

In this case a driven patch is used to feedthe antenna, having 2.53 cm of length and5.30 cm of width.

The driven patch (inner patch) is fed by acoaxial probe placed 2.18 cm below itscenter.

The wraparound patch has the followingdimensions: 10 cm length and 5.42 cmwidth.

Both patches are centered, i.e. their centers

CONFORMAL ANTENNASSTACKED PATCH ANTENNA ON CYLINDRICAL STRUCTURE


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The relative RL bandwidth of the antenna is 13.4%, from1.81 GHz to 2.07 GHz, much improved in comparison to theprevious model.

The radiation pattern still remains nearly omnidirectional,with approximately 4 dB of omnidirectionality in the azimuthplane.

Unlike the previous antenna, this one is designed for linearpolarization.

CONFORMAL ANTENNASSTACKED PATCH ANTENNA ON CYLINDRICAL STRUCTURE

CONFORMAL ANTENNAS


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Consider a quasi-square patchprinted on a grounded cylinder withArlon CuClad TM 250 GX substrate(relative permittivity r = 2.55, losstangent tan = 0.0022) andthickness h = 3.048 mm.

The standard radius of thecylinder is 250 mm and the proberadius is 1 mm. l = 39.397 mm, l= 14.153 mm, 2b =

38.005 mm, z = -13.854 mm;

where l is the azimuth width ofthe patch, 2b is the axial length ofthe patch, lis the azimuth positionof the probe and z is the axial

CONFORMAL ANTENNASPARAMETER VARIATION STUDY OF THE CYLINDRICAL

STRUCTURE

CONFORMAL ANTENNAS


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The probe must be placed at the specificpoint that excites the modes TM01 (z-direction excitation) and TM10 ( -direction excitation) with the sameamplitude and 90 phase difference inorder to produce RHCP.

For this, the feeding must be selected inthe diagonal of the quasi-square patch[22] so that


STRUCTURE

CONFORMAL ANTENNAS


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Through the RHCP spinned radiation pattern, it is possibleto observe the coverage of the reference cylindrical microstripantenna and its polarization purity.


STRUCTURE

CONFORMAL ANTENNAS


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Let us see how the variation of the main physical parameters of asingle patch conformed on a cylindrical structure, namely

the cylinder radius,

the substrate thickness and

the substrate permittivity, affects the antenna characteristics.

Mainly three characteristics are observed:

the return loss,

the axial ratio and

the radiation patterns.

The resonance frequency for this comparative analysis was chosento be 2.25 GHz as an arbitrar test fre uenc .


STRUCTURE

CONFORMAL ANTENNAS


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Variation in radius : Effect on the return loss


STRUCTURE

CONFORMAL ANTENNAS


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Variation in radius : Effect on the Radiation Patterns


STRUCTURE

CONFORMAL ANTENNAS


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Variation in the relative permittivity

As known from non-conformal antenna design, for low relativepermittivities, the RL bandwidth is larger, and when the substratepermittivity increases the resonance frequency decreases.

Thus, low relative permittivity materials like foams are oftenemployed in multilayer antennas.

These foams tend to be fragile, difficult to glue and difficult to bend[19] which might cause problems for the manufacturing.

Therefore, not only the performance must be taken into account in

conformal antenna design but also the manufacturing.


STRUCTURE

CONFORMAL ANTENNAS


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Variation in the relative permittivity : Effect on the returnloss


STRUCTURE

CONFORMAL ANTENNAS


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Variation in the relative permittivity : Effect on the AxialRatio


STRUCTURE

CONFORMAL ANTENNAS


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Variation in relative permittivity : Effect on the radiationpatterns


STRUCTURE

CONFORMAL ANTENNAS


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Variation in the substrate thickness

Another important factor in the antenna performance is thesubstrate thickness.

The thickness of the substrate is critical for the conformalantenna manufacture since the flexibility of the material is worsefor thick substrates and very thin materials may be too fragile tobend.

As for planar antennas, the RL and AR bandwidth are increasedwhen the substrate thickness is increased. It is also seen thatvarying the thickness causes a shift of the resonance frequency.


STRUCTURE

CONFORMAL ANTENNAS


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Variation in the substrate thickness : Effect on the returnloss


STRUCTURE

CONFORMAL ANTENNAS


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Variation in the substrate thickness : Effect on the AxialRatio


STRUCTURE

CONFORMAL ANTENNAS


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Variation in the substrate thickness : Effect on theRadiation Patterns


STRUCTURE


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CONFORMAL ANTENNAS


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A quasi-square patch antenna is printed on differentgeometries with the same resonant frequency in order toachieve reasonable results for comparison.

CONFORMAL ANTENNASCOMPARATIVE STUDY OF DIFFERENT GEOMETRIES

CONFORMAL ANTENNAS


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The comparison of the E-field radiation patterns shows that the planar antennapresents the narrowest beam.

In the = 0 plane, the radiation from the doubly curved geometries is broader sincethere is a curved surface whereas for the singly curved geometries it is straight.

In the = 90 plane, all analyzed conformal antennas have the same curvature of0.3 0. That leads to approximately the same beamwidth in the hemisphere ofmaximum radiation

CONFORMAL ANTENNASCOMPARATIVE STUDY OF DIFFERENT GEOMETRIES

CONFORMAL ANTENNAS


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Nearly omnidirectional patterns using a single radiating elementare achieved with wraparound patch antennas.

Cylindrical wraparound patches have the drawback of dipole-likeradiation patterns in the plane that includes the length of the cylinder,

resulting in almost null radiation in that direction.

To avoid this problem, the possibility of bending the cylinder hasbeen analyzed. The result is a toroidal wraparound patch.

CONFORMAL ANTENNASWRAP AROUND PATCHES

CONFORMAL ANTENNAS


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Comparison between a patch wrapped around a cylinder and a patchwrapped around a torus. The resonant frequency is 1.575 GHz andthe substrate used is Teflon, with a relative permittivity r = 2.1.


CONFORMAL ANTENNAS


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Both type of antennas have similar radiation patterns in the = 0 plane,providing nearly omnidirectional coverage. In the = 90 plane thecylindrical antenna has dipole-like radiation pattern while the toroidal onepresents nearly omnidirectional coverage.


CONFORMAL ANTENNAS


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CONFORMAL ANTENNASADVANTAGES AND DIS-ADVANTAGES

CONFORMAL ANTENNAS


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The surface of the aircraft where the antenna must be mountedaffects the radiation properties and it is important to be able topredict such variations.

Complex geometries lead to elaborate problems and long-time EMsimulations.

Therefore, the antennas are placed on an aircraft footprint to predictthe E-field radiation instead on a complete aircraft where they could

be also affected by multipath effects from, for example, the wings ofthe aircraft.

CONFORMAL ANTENNASEFFECT OF THE AIR-CRAFT FOOTPRINT

CONFORMAL ANTENNAS


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The antenna might be located on the forward part of the fuselage (or close tothe centreline) to minimize shadowing by the vertical stabilizer and by thewing during all manoeuvres. Figure illustrates the aircraft footprintdimensions.


CONFORMAL ANTENNAS


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The antennas are integrated on the footprint in mostly three positions: alongthe footprint surface, 6.5 cm over the footprint and with an absorber belowthe antenna.



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CONFORMAL ANTENNAS


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The figure shows aquasi square patchprinted on a sphere.

Patches withdifferent shapes canbe printed on thesphere, like a

rectangular, anannular ring or awraparoundantenna.

A better

CONFORMAL ANTENNASDOUBLY CURVED SURFACES

CONFORMAL ANTENNAS


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The polarization of doubly curved antennas is an important factor tobe considered

Three alternative definitions are adopted by Ludwig


CONFORMAL ANTENNAS


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The XPD of cylindrical antennas is worse than their planarcounterparts due to the curvature effects.

Therefore, for doubly curved surfaces this effect is even moresignificant since there is one additional curvature.

For array configurations, the curvature is very important to be takeninto account since when the radiating elements are almost free of

cross polarization, the curvature of the structure can produce crosspolarization.


CONFORMAL ANTENNAS


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This doubly-curved antenna has two differentradii that vary the curvature of the patch. Theradius of the bent cylinder is referred to asinner radius and the radius of the torus ring isreferred to as torus radius.

The torus radius must be always equal orsmaller than the inner radius.

CONFORMAL ANTENNASTHE TOROIDAL MICROSTRIP ANTENNA


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III - AIRCRAFTANTENNAS


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ANTENNAS FOR AIRCRAFT


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COMMUNICATIONANTENNAS

Communication antennas arebasic in operation and have relatively

few problems, except fordelamination.

Each com transmitter has its ownantenna, mostly for redundancy.

The antennas can be mounted oneither the top or bottom of theaircraft, but each installation is

susceptible to shadowing from theusel e.




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LORAN ANTENNAS

The loran antenna is similar insize to the com antenna andsometimes the exact same shape, but

it is different inside.

Most modern loran antennas havean amplifier built into the base toboost the signal

A loran antenna can be eithertop- or bottom-mounted, but thereceiver must be configured for theantenna position.

Loran systems are alsosusceptible to P-static interference,

caused by a buildup of electrical




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ADF ANTENNAS

They have the ability todetermine which direction a signal iscoming from; hence, they are also

called directional antennas.

Most have two or three separatecoils of very thin wire wound atvarying angles to each other in theshape of a bagel laid flat.

The signal is received at differentstrengths between the coils, and the

receiver uses those different signalstren ths to determine the direction



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MARKER BEACONANTENNAS

Marker beacon signals are highlydirectional, which means you have to

be almost directly over thetransmitting ground station to receivethem;

Therefore, marker beaconantennas need to be on the bottom ofthe aircraft.

There are a few different types of

marker antennas; the more commont es look like little c noes bout 1




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UHF ANTENNASUHF antennas are commonly used

for transponders and DMEs and arealways found on the bottom of theaircraft.

They are about four inches long,and the same antenna is often usedfor both systems because thetransponder frequency is in themiddle of the DME frequency band.

Two types are commonly used,spike (one frequency) (Fig 5) andblade antennas (broadband) (Fig 6).

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NAV ANTENNAS

The cat whisker consists of acouple of rods jutting out from eachside of the vertical stabilizer at a 45-

degree angle (Figure 9). poor atreceiving signals from the side andwas developed for aircraft that fly lowand commonly track either directly toor from a station.




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NAV ANTENNAS

The dual blade is just that, twoblades, one on each side of the tail(Figure 10).

The towel bar resembles thecommon bathroom fixture, one oneach side of the tail.

The blade and towel bar antennasare both "balanced loop" designs,which have equal receiving sensitivityfrom all directions.




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GPS ANTENNAS

The GPS satellites transmit less than five watts of power, so by thetime the signal reaches you, it is very, very weak.

Because of this, the GPS antenna has a built-in amplifier to boostthe signal for the receiver.

Additionally, the GPS frequency is so high (in the gigahertz band)that the signals travel in a line-of-sight manner.

This makes receiving the signal susceptible to airframe shadowing,thus mandating that a GPS antenna be mounted at the very top of the

fuselage.



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RADAR ALTIMETERS

Radar altimeter antennas are simple, comprising either a single ordual antenna system.

They look like plates about six inches square and live on thebottom of the aircraft.

The radar signal is transmitted straight down to bounce off theground.

The time between transmitting and receiving the signal ismeasured and used to determine the distance above the ground.



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IV - MISSILE ANTENNAS

MISSILE ANTENNAS


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Innovative conformal antenna designs are being sought fora number of existing missile airframes capable of transmittingand receiving an ultra wide bandwidth of frequencies (30 MHzto 2000 MHz).

These antennas are meant to replace the current weaponantennas which are narrow band and directional.

Omni directionality is also required by the so called

Network Enabled Weapons (NEW) to allow them to have asimultaneous link completion with as many network nodes asis possible.

The introduction of new antennas should not produce new

MISSILE ANTENNAS

MISSILE ANTENNAS


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Some of the design requirements for the conformalantennas which have to be installed on existing airframes are

1) size depth less than 0.7 inch for a missile diameter of 9 inchesto 21 inches,

2) Weight less than 5 lbs,

3) Bandwidth 100 MHz to 2000 Mhz for a VSWR < 2.0,

4) Antenna Pattern Less than 2dB isotropic variation,

5) Polarization - Vertical relative to skin of weapon airframe,6) Material Need to withstand high speed (supersonic) flight and

need to be highly repeatable for manufacturing purposes,

7) Power ability to handle a nominal power of 90 Watts with amaximum of 125 Watts,

MISSILE ANTENNAS

MISSILE ANTENNAS


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Insert Dielectric Guide (IDG) antenna for deployment on amissile.

MISSILE ANTENNAS


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MISSILE ANTENNAS


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The antennas mounted in the aircraft are SubstrateIntegrated Waveguide (SIW) slot antennas. The four slotsarranged in line are to reduce the beam width in H plane andincrease the gain.

MISSILE ANTENNAS

MISSILE ANTENNAS


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The antennas mounted in the aircraft are SubstrateIntegrated Waveguide (SIW) slot antennas. The four slotsarranged in line are to reduce the beam width in H plane andincrease the gain.

MISSILE ANTENNAS


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ANTENNAS FOR SPACE APPLICATIONS


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Launch vibrations and depressurisationLocal accelerations of several gs

Risk of mechanical damage

Vacuum

No thermal convection

Outgassing of plastic material(deterioration and pollution of opticalinstruments)

AMBIENT CONDITIONS



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Antennas are outside the spacecraft

Direct exposure to space environment

Antennas are often semi-detached

Worst condition during launch

Antennas are often very big

Need complex deployment mechanisms

Some antennas are mission-critical If they fail the mission is lost

AMBIENT CONDITIONS



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Antennas with dimensions comparable to the wavelength

Directional radiation pattern

Circular beam with 60-120 aperture

Gain is below 10dBi

Used mostly as service antennas

Main design objective: maximum gain within desired angle

LOW GAIN ANTENNAS



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Size between 3 to 10

Gain of about 10 to 20dBi

Typically waveguide horns and arrays, but also travelling wavestructures : e.g. the Yagi-Uda antenna for TVs.

Main design objectives: gain, polarisation purity

MEDIUM GAIN ANTENNAS


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The antennas for the Telemetry and Tele-command subsystem of a satellitemust satisfy the following requirements:

Provide coverage all around the satellite (full sphere)

Be extremely reliable

Have minimum losses

OTHER REQUIREMENTS

Polarization

Earth-Space (Uplink) and Space-Earth (Downlink) links shall becircularly polarized.

Coverage : Hemispherical. 0 360;0 90

Gain value : 0 dBi

Cross-polarization : -10 dBi

Power handlin : U to 10 Watts for tele-command

TELEMETRY AND TELECOMMAND ANTENNAS

ANTENNAS FOR SPACE APPLICATIONSTELEMETRY AND TELECOMMAND ANTENNAS


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The Bands of Operation

L: 1.2-1.5 GHz X: 7-8 GHz

S: 2.0-2.4 GHz Ku: 12-14 GHzC: 4.0-6.0 GHz Ka: 20-30GHz

TELEMETRY AND TELECOMMAND ANTENNAS

REFERENCES


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[1] Palanisamy, V., and R. Garg, Rectangular Ring and H-Shaped Microstrip AntennasAlternative to Rectangular Patch Antennas, Electronics Letters, Vol. 21, No. 19, 1985,pp. 874876.

[2] Chew, W. C., A Broadband Annular Ring Microstrip Antennas, IEEE Trans.Antennas Propagation, Vol. AP-30, September 1982, pp. 918922.

[3] Huynh, T., and K. F. Lee, Single-Layer Single-Patch Wideband Microstrip Antenna,Electronics Letters, Vol. 31, No. 16, 1995, pp. 1310

[4] Luk, K. M., K. F. Lee, and W. L. Tam, Circular U-Slot Patch with DielectricSuperstrate, Electronics Letters, Vol. 33, No. 12, 1997, pp. 10011002.

[5] Wong, K. L., and Hsu W. H., Broadband Triangular Microstrip Antenna with U-Shaped Slot, Electronics Letters, Vol. 33, No. 25, 1997, pp. 20852087. 1312.

[6] Targonski, S. D., R. B.Waterhouse, and D. M. Pozar, Design of Wideband ApertureStacked Patch Microstrip Antenna, IEEE Trans. Antennas Propagation, Vol. AP-46, No.9, 1998, pp. 12451251.

[7] Legay, H., and L. Shafai, A New Stacked Microstrip Antenna with Large Bandwidthand High Gain, IEEE AP-S Int. Symp. Digest, 1993, pp. 948951.

[8] Balakrishnan, B., and G. Kumar, Wideband and High Gain Electromagnetically

REFERENCESC td


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[9] Hall, P. S., Multi-Octave Bandwidth Log-Periodic Microstrip Antenna Array, IEEProc. Microwaves, Antennas Propagation, Pt. H, Vol. 133, No. 2, April 1986, pp. 127138.

[10] Kakkar, R., and G. Kumar, Stagger Tuned Microstrip Log-Periodic Antennas,IEEE AP-S Int. Symp. Digest, July 1996, pp.12621265.

[11] Popovic, B. D., et al., Broadband Quasi-Microstrip Antenna, IEEE Trans.Antennas Propagation, Vol. AP-43, No. 10, 1995, pp. 11481152.

[12] Gitin, M. M., et al., Broadband Characterization of Millimeter-Wave Log-PeriodicAntennas by Photoconductive Sampling, IEEE Trans. Antennas Propagation, Vol. AP-42, No. 3, 1994, pp. 335339.

[13] Kin-Lu Wong, Design of Nonplanar Microstrip Antennas and Transmission Lines,John Wiley & Sons, 1999.

[21] Per-Simon Kildal, FOUNDATIONS OF ANTENNAS. A Unified Approach.Studentlitteratur, 2004. pp. 23-30, 191-214.

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