Download - NAVSAT: A Global Satellite Based Navigation System

NAVSAT: A GLOBAL SATELLITE BASEDNAVIGATION SYSTEM

C. RosettiEuropean Space Agency

8/10 Rue M. Nikis75738 PARIS 15 - FRANCE

C. CarnebiancaItalspazio

Via V.E. Orlando, 8300185 ROMA - ITALY

ABSTRACT Space Segment: The NAVSAT Space segment [1] con-sists of 18 elements (fig. 1): 12 satellites spread over six

The NAVSAT concept, developed by the European Space twelve hours highly eccentric orbits (HEO), inclined 63.450Agency, in close cooperation with the industries and user over the equator and 6 navigation packages on board equallyorganizations has been conceived to fulfill the civilian user spaced geostationary host satellites. The satellites will em-requirements for a better navigation capability and mobile bark simple low power C/L band transponders, broadcastingcommunication needs in the future. In selecting the NAV- the navigation signals (L-band), received from the groundSAT architecture, special care has been devoted to different stations (C-band), toward the users.satellite constellation alternatives in order to identify themost promising solution in terms of navigation performanceand system cost. The paper describes the present NAVSATbaseline and status. This baseline while offering precisenavigation performance comparable or better than GPS, cuts

6

significantly the overall cost of a satellite navigation system.The particular constellation selected is also easing the set upof the integrated navigation-communications-search and 17

rescue service.

NAVSAT SYSTEM

The NAVSAT system encompasses four major t4g0 , .elements: space segment, signal structure, ground control ,/ tt,\ 'segment, user segment.. (/ -' 5

Based on a paper presented at the 1986 PositionLocation and Navigation Symposium.0885-8985/87/1200-0015 $1.00 ©r 1987 IEEE Figure 1. NAYSAT GEO + HEO Constellation

IEEE AES Magazine, December 1987 15

Signal Structure: a Time Division Multiple Access Master Station (MCS), leading to a "star" topology of the(TDMA) format has been selected for NAVSAT [2,3,4]. ground network.The TDMA frame (fig. 2) will consist of nine sequential With this approach, each of the 6 RC stations (fig. 4) up-bursts of 230 msec., separated by a suitable guard band of loads each tracked satellite in view and sends the tracking120 msec. to avoid overlapping. The frame duration is 3.15 data to the master station through the GEO-satellites triadsec. Antipodal satellites will share the same time slots. Each selected for this function. The upload signals and the systemTDMA burst is composed by three types of signals (fig.3). data flow will use the C-band.

A continuous CW for coarse position fixing by using /538doppler shifts or for acquisition aiding of the spread 70

60

spectrum components. F 50

- A Spread Spectrum Signal, for precise ranging 3-"WAY 0

measurements (the code is the same for all satellites). ID- A data stream, for sending satellites ephemeris and .0 -VUN

6-C28R88AR 20

other application data. PRETORIA 30

5060

70

230.6 SO

_ _ _6Sat. 1,7 180 210 240 270 300 330 0 i3 60 90 2i0 150' 18

.. . .._/S2,8Figure 4. Proposed Sites for NAVSAT Ground StationsSat. 3,9

_. _ . L ._ _ . _ __ ____Sa~~~~~~St 4,1 0---F<Th -~ ___ 5.6 4,10The MCS monitors the entire system by processing the

E2_ __ -43S.t6,2 telemetry and tracking data coming from each RCs through-; _ _ _3. _ _ . ______3____Sat. 13,16 the selected GEO-satellites links. The down link for most of

--- - J.ZI TX 5^t' 14the satellites consists of TDMA bursts for position fix and

' ''3 -" see.-5dt120 telemetry data which are collected by the RCs and sent to; the Master Control Station, along with tracking data for

ephemeris prediction. Only the GEO-satellites in charge ofFge.Ps len relay function, will receive and retransmit the network data.

User Segment: The user equipment that can be cate-gorized according to the user class which include stationaryand slow motion users (e.g. Marine), high speed users (e.g.Aviation) and very high speed users (e.g. Earth observation

CARRIER satellites). Due to the signal structure characteristics theposition determination, depending on the type of the user

DATA equipment can be accomplished by the Doppler mode ofRANGING SIGNAL operation (slow motion users) or by ranging mode of opera-

tion (high speed users). In the ranging mode the userreceiver measures the pseudoranges to four satellites,evaluates satellites position by processing the ephemeris dataand estimates the user position and time. Doppler mode can

Figure 3. Navigation Signal Components be used for code phase prediction, to acquire the pseudoran-dom code for pseudorange measurement, avoiding lengthycode searching.

The particular form of Spread Spectrum chosen for NAV- Overall System performance: The 3-D navigationSAT is depleted of power on the vicinity of the carrier fre- performance, on the basis of a 1-sigma pseudorangequency and orthogonal to it. insuring freedom from mutual measurement error of 5 m (table 1), is 12.5 m (SEP).interference. For the data transmission, Manchester codedPSK has been selected which is also orthogonal to both CW Error Contributor Valueand to the modified spread spectrum (m-sinc) signal. Satellite ephemeris 1. 5 m

Ground Control Segment: The function of the Ground Satel lite clock noise 0.9 m

Segment is the control of all the operations required by the Ionosiheric resiouai 3.0navigation system [5]. The tasks allocated to the ground T'ropospheric residual I 2.0 m0segment include: navigation signal uploading, time syn-dV011oJLiL.dL1iI, ionospheric delay correction,? satellite health Muit ipath 1.0mstatus control, ephemeris determination and prediction. SUBtiOTAL 4.2 mThe proposed NAVSAT constellation offers a big advanl- Receiver accuracy 2m

tage compared to the subsynchronous circular constellation.XIn fact, with three GEO-satellites, spaced 1200 apart over the Toarerrovr atS) I5equator, all the ground station (RC) needed to track thenavigation satellites can be continuously linked with the Table 1. Pseudorange Measurement Errors Budget

16 IEEE AES Magazine, December 1987

CHARACTERISTICS OF NAVSAT GEO + HEO IrALWPAZO CAD

WORLDWIDE SERVICE 7060

5040The proposed NAVSAT GEO + HEO constellation con- 20

sists of 6 navigation packages in Geosynchronous orbit and A.n12 satellites in HEO. The GEO navigation packages are V0equally spaced (i.e. 600 apart) on ffie equatorial plane. The 30HEO's are divided into two groups of three orbits with two 50

navigation satellites each. The orbits of each group, one for 70

each Earth hemisphere, are displaced 1200 apart in longitude 020 240 270 0 30 60 90 120 150 180and share the same orbital planes with those ones of theother hemisphere. The constellation general characteristics Figure 6. NAYSAT GEO Subsatellite Pointsare shown in table 2. In fig. 5 are shown the northern HEOsatellites subtracks and in fig. 6 the position over the equator The second random variable is associated with theof the GEO-navigation packages. The HEO satellites are variability of the errors in the pseudorange measurements.considered operational when the altitude is greater than The overall performance of the NAVSAT GEO + HEO10635 Km as indicated by the dotted line in fig. 5. configuration, and a comparison with circular orbit con-

figurations including GPS, are shown in fig. 7 for the PDOPstatistics.

'I APOGEEIPERIGEEIjRAAN* I INCL. IARG. OFIINITIALSAT JORBITI ALT. ALT. IPERIGEEI TRUEN. TYPEI (Km) (Km) I(deg)j (deg) (deg) JANOMALY ITAL95'AZIO Ca

g I .(deg) _r

1 HEO 39105 1250 340 63.45 270 180 0.9 -

2 f 2403 1" 1001 1 168 0.8 -4 so "f i i 2065 If 220 I 155 0 .7 -

6 1o of " 1 192 /7 1 3401 90 180 0.6 -8 1 " fI" 240 69 ofI 100 168 Lo 0101" I I " I " ~~~~~~~~~~~~~~~2060

11 of is is 2 2() 1 5 5 E/NAVSAT 18 GEO+HEO121 220 oI 155

t0.4 - +CIRCULAR 24/3/2 [7]12 1"# 192

13 GEO 35786 35786 0 0 0 285 <3OGPS 18/3/0 [7]14 f 0 |0|0 1 345 : 0.3 AGPS NON UNIFOR.M 18 [o]15 1 " 0 1 0 0 451611 101 0 0 105 0 0.2 -

17 1 01 0 0 165 L18 1" ! " 10! 0 ! 0 1 225 0.1

0*1 3 5 7 9Table 2. NAVSAT Constellation Characteristics OPDO LEVEL

Figure 7. Availability Curves for Selected Constellations

These curves represent the probability that PDOP is lessthan the value reported on the abscissa. The PDOP can be

6, 7< P ^~ >S03 considered as the amplification factor of pseudorange errors

* 4eIrt0 into user errors due to effect of the satellites geometry.A12t Therefore the 3-D position error can be simply estimated by

10 multiplying the PDOP by the pseudorange error. Using the/X /\t1X:0 Spherical Error Probability (SEP), which is given by the

30/ \ /\Xprobability of the navigation error being less than 50%, asso comparison criterion, the NAVSAT 18 GEO + HEO

satellites constellation provides a lower SEP value (about240 24o *X o 12.5 meters) than GPS non uniform 18 satellites constella-

tion. It is worth to remind that only GPS C/A code isFigure 5. NAVSAT HEO Ground Tracks available for civilian applications, providing a SEP greater

than 100 m.However at the highest probabilities, the navigation

performance of the GPS non uniform 18 satellite constella-PDOP and 3-D Position Error: The navigation accuracy tion exceeds that of the NAVSAT 18 GEO + HEO satellite

can be considered as a function of two random variables, constellation. This can be explained as follows: NAVSATThe first one is associated with the geometric properties of GEO + HEO is optimized in zones of main interest for civilthe spacecraft constellation: Geometry Dilution of Precision users (i.e. North Atlantic) while the GPS non uniform was(GDOP) or Position Dilution of Precision (PDOP). optimized to fulfill other requirements. Therefore at the


lowest probabilities, NAVSAT exhibits more areas with the system accuracy up to an acceptable level until the user

lower PDOP than GPS (this explains the steeper climbing of leaves the outage zone. An example of the system capability

NAVSAT in fig. 7), while at the highest probabilities, NAV- to overcome outage periods, switching from 4-satellites to

SAT degrades more than GPS (in fact, GPS non uniform 3-satellites with a precise clock support, is shown in fig. 10

recovers at 90% of probability). As it will be shown later (worst case condition). The overall improved performances

the high PDOP level can be improved with alternative indicate that a PDOP =5 is never exceeded (fig. 11).techniques which require only 3 satellites in good visibility.System Outages: As it results from the visibility analysis,

a minimum of 4 visible satellites from whatever location on 5 CAB _ _the Earth are available with an elevation mask angle of 5degrees. Nevertheless, in few places and for limited time in-tervals a poor satellites geometry occurs, resulting in largePDOP (greater than 10) and 3-D position error values. TheNAVSAT composite outages (i.e. all the zones whereoutages occur even though at different times) are shown in - ,

fig. 8. -

JTALMOA?OISAT. NAVIGATION

.................... ......SAT. Rb)

50 s40... -.- sa.-. . t':. . 20 ~~~~~~~~~~~~~~~~~rimeMos)~~~~~~~~~~30

-*-->_....a-- [ 10

..... g) ~> ~, Figure 10. 3-D Position Error Using 4 Satellites and20 -- < - l-i ,3 Satellites with Clock50

60M.S,~ ~~0 ........... ... ....... 70s

F=w ,~~~~~~~~~......- j,j,.. j71MSD>~~~~~ITAL39 ZD A

IS0 210 240 270 300 33 ° 30 60 90 120 1t0 180

Figure 8. Composite Outages of NAVSAT GEO + HEO 0,|Constellation 0il

e0..

For comparison purpose the GPS outages are reported in fig. 9. j. |

X 0.4-

0.3

0.2 -

Ep tj \; >? 1 t I~~~~~~~~~~~~~~~13 7 3

Figure 11. Availability Curve with Precise Clock Support

mU -WY-ID 4-l-06 ON0 AM21 wooIIII l'rt4 System Availability: The system availability is defined as

the probability that the PDOP is less than a preselected valueFigure 9. Composite Outages of GPS Non-Uniform (e.g. PDOP less than 6). An important aspect is the

Constellat'ion behaviour of the system availability degradation versus miss-

ing satellites. The level of degradation, besides quantifying

Techniques for Outage Overcoming: For a 3-D position the impact on the service quality, is the key element for an

fix 4 informations are needed to solve the system equations. in-orbit spare strategy.The 4 unknowns are x, y, z, t. With an updated clock The analysis results, shown in fig. 12 and table 3 and

technique, as suggested for UPS [6], only 3 information are compared to the UPS and the circular constellation with 24

needed (x, y, z). Therefore, equipping the 3-D user receiver satellites, indicate that the degradation is "graceful".with a precise clock, the navigation solution can be ac- Aeronautical Applications: As anticipated in the NAV-

complished using only 3-satellites in the outage locations. SAT service requirements, the aeronautical users rank among

In conclusion, when the 4-satellites navigation perform- the most demanding ones. Therefore, the suitability of

ances degrade under a certain standard, the 3-satellites NAVSAT for such a kind of applications was considered

navigation, aided by a precise clock, can be used to improve mandatory. To verify the system performance along the ma-


ITAL3'AZ CD - tooA050IAAZIO Ca

s0 A 'NORTH MID-ATLANTIC 3O' 1 - 48'N

so0 40-

V

70

so*

: 1 3

Nunb.r of SLtl.l1ts MtasIvi rime (hours)J 24 circ.Orb.[7] 2 NAVSAT 18 GEO+HEO 1 1GPS NON-UNIFORM 18 [7IXIiAL]AD CM

B OKNASTK SEA 128 E - 38WNFigure 12. Approximate Worst Case Availability for

Selected Constellations '

N. OF APPROXIMATE WORST CASE AVAILABILITYSAT'S (PDOP <.6)MISSINGI -------------I.---I-------------

I CIRCULAR NAVSAT 18 GPS24/3/2 [7] GEO + HEO NON-UNIFORM

I 18 [71 4 SAT. NAVIGATION._______ ___ ______ ___ __ -I--3 SAT. NAVIGATION (Rb)

0 1.00 0.953 0.98 1-

1 1 1.00 0.935 0.933 6 9 Q 1S 10 2f X

2 0.98 0.890 1 0.85 Time (hours)

._ _ _ _ _ -_-_-I . - ----------I. ---I .--- -----

3 0.95 0.812 0.76

._________________ - , ,Figure 14 A/B. 3-D Navigation Accuracy from SelectedPoints of Figure 13

Table 3. Approximate Worst Case Availability for theCircular and GEO + HEO Configurations CONSTELLATION FOR SELECTED AREA SERVICE

A unique feature of this GEO + HEO constellation isthat, with a reduced number of space elements it is possible

jor aeronautical routes (fig. 13), the 3-D position error has to set-up a continuous 3-D navigation service in selectedbeen evaluated for selected points (fig. 14) over the oceans. areas. An important consequence from economic stand point,The results show that high navigation performances (typically is the possibility of a gradual constellation implementation.20 m) are expected to be achievable. Selecting North Atlantic and Pacific zones (double shaded

areas in fig. 15) the best reduced constellation is that onehighlighted in fig. 16 and table 4 and consists of 4 GEOnavigation packages and 3 HEO satellites.

IT1lt X

70 706~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0

50 50

40 4070 30

- 0

180 210 241 270 300 320030 60 90 120 150 18~~~~~0 80 210 240 270 300 330 0 306090120 150 180

Figure 13. Main Operating Aeronautical Routes Figure 15. Selected Areas


With regards to the navigation performance in the reducedSAT. SAT. 3' North Atlantic and Pacific zones, the PDOP statistics can be

X 9\ 5 h I improved with a precise clock support (fig. 18) in order toremove outages occurrences (defined as PDOP greater than10).

HEO SATELLITES 1r ______CM __X

10.-9S S.2'(2) 0.7

/ ~~~~~~~~~~~~~~~~~~~~~~~~~0.7

0.75

SAT.2t(1)~ ~ ~ ~ ST.'()

0.4

60'~~~~~~~~~~~~~~~~.

o 0.2

1I~~~~~~~~~~~~~~~ ~~~~0.1

EL~~~~~~~~~~PO UE

SAT. 2'(1)

Figure 16. Minimum Constellation for 3-D Navigation Figure 18. Availability Curves for the MinimumConfiguration

N. SAT.; APOGEE PERIGEE ARGUMENT RAAN INCLINATION 1 PHASING PHASINGIALT.(Xm)I ALT(KmI 10F PERIGEE) I (II (2)-------- I---------: I----------

PI------I------ I I (As concerns the remaining zones, where for most of the1 3O GEO GEO GEO GO - 75' 105.~~~- I-----I--------------------I---------I----- time at least 3 satellites are in visibility, apart limited2 GEG GEO GEO GEO GEO -15'

,065'

3' 39105 1250 270' It00' 63.45' 1 68' periods with 1 or 2 satellites at polar latitudes, 2-D naviga-4 39105 1250 _270' 100':63.45-' 206' tion service is expected to be achievable while 3-D naviga-S. - 39105 -1250 270' 220* 63.45' 154¢ t3on is possible (but time limited) with a precise clock

Table 4. Selected Constellation for 3-D Navigation support.in the Selected Areas

NAVSAT PERFORMANCES FOR SPACEAPPLICATIONS

The visibility analysis results show that, in the reducedNorth Atlantic and Pacific zones (double shaded areas in fig. Use of the NAVSAT system for space applications re-15) and for most of the time, 4 satellites are in visibility quires a sufficient number of navigation satellites in view,(fig. 17). For the remaining zones (single shaded in fig. 15) signal availability and usability. A low altitude spacecraft3 satellites are visible most of the time. (LEO) (fig. 19), which falls in geometric view of a naviga-

tion satellite beyond the edge of the Earth coverage, is ex-

60 IALAZOX pected to experience a reduction of the navigation signal64.3 EIRP and an increase of the path losses along with the

possibility that the incoming signal is not usable due to thereceiving antenna characteristics.

40W - aT/40O1 LEO USER

20 -j

N0NVST ofSC

s

Figure 17. Probability of Having N Satellites in Viewfor the Minimum Constellation Figure 19. System Geometry

20 Foreign Technology Insert follows. IEEE AES Magaz.ine, December 1987

The analysis results indicate that, using a skyward receiv- the service over, but not limited to, the polar zones. This or-ing antenna with a beam-width of 1000 (half cone angle), the bital commonality is expected to provide opportunity for em-proposed system seems well suitable for space applications, barking navigation packages on board of host satellites bothas far as PDOP performances are concerned. Considering an in GEO and HEO's, reducing drastically the number oforbit of the European Columbus Mission [7] (1000 Km of dedicated satellites. In principle, considering 3 HEOaltitude and 28.50 of inclination), the number of satellites in satellites for mobile communications service with coveragevisibility, (providing usable navigation signals) ranges from 6 extension beyond the polar zones to complement and supple-to 9 (fig. 20) and the PDOP values do not exceed 2.5 (fig. ment the service provided by GEO satellites (e.g. INMAR-21). SAT), as identified in recent ESA studies, the number of

dedicated navigation satellites could be reduced to six. Con-sidering that mobile communications and navigation servicewill operate at L-band, the commonality would includebesides the major spacecraft subsystems, also the antennawhich would further enhance the system economy.

qs STATUS

4_ #The NAVSAT Concept has been developed with contribu-t3- tion from several industrial and research organizations in the2- frame of studies funded by the European Space Agency. The

system Configuration presented in this paper summarizes thecharacteristics of the current NAVSAT baseline.

' IV 21, * ? ss sr xsA harmonization study is now in progress, under the aegisTiae (hoirs) of the European Space Agency, between the NAVSAT

system and another European conceived system (GRANAS)Figure 20. Visibility Time History for the Selected LEO for assessment and selection of a common system concept

User Removing also Antipodal Satellites that could be the basis for a future development of aSatellite-based navigation system for civilian applications.

3 TALYA2IOCM

CONCLUSIONS

2.4- | A 1l l lThe current NAVSAT concept, based on GEO + HEO2.1-; , 4 constellation, which exhibits performances comparable to

1.8- ~~~~~~~~~~~~~~GPS,looks very attractive and has the potential to cutRu, 1.5f |significantly the cost of a satellite based navigation system.

F'S 1.2- The advantages offered by this approach include:,., Reduced Number of Satellites: 12 satellites in HEO equally*.6- shared between Northern and Southern hemisphere and 69.32- navigation packages on board geosynchronous host satellites.

T,e , , , , , , ,Growth Capability Starting from a Reduced Configura-I .7 F .9 V a to 2f 2X tion: The proposed NAVSAT constellation presents the(ie(hoirs) unique feature that only few elements are needed to set-up a

continuous 3-D navigation system over selected areas (e.g.Figure 21. PDOP Time History for the Selected LEO UserNorth-Atlantic, Pacific). This reduced configuration can, astime goes by, be expanded to global coverage.

MULTIMISSION COMPATIBILITY Multimission Compatibility: Both the GEO and the HEOpart of the system offers multimission between the navigation

The GEO + HEO configuration selected for the NAVSAT and the communications function. It has to be reminded thatsystem looks very promising as far as multimission satellites a dedicated satellite system for "polar" mobile communica-are concerned for cost sharing. The most natural co- tions could not be economically self maintaining. Since bothpassenger of a navigation payload is a communication one, the navigation and the mobile communications servicein particular a mobile communications payload. This would operate at L-band, it will be possible to obtain a certainprovide the opportunity for an integrated high value com- commonality of satellite subsystem, with the consequent in-munications/navigation service. In this perspective the poten- crease of economy.tial user can relay its position, basically through a paging Launch Strategy Optimization for HEO's: Due to the factservice, to another location. While the geostationary satellite that three orbital planes spaced 1200 apart over the equatorcan provide this service up to a certain latitude, satellites have been selected for HEO satellites (each orbital plan con-placed in HEO at least 2 for each hemisphere, could extend tamning 4 satellites equally distributed over the Northern andIEEE AES Magazine, December 1987 21

the Southern hemisphere) only 3 launches with multi-launch BIBLIOGRAPHYconfiguration are in principle needed to deploy the HEOsatellites in both hemispheres.Ground Control Segment Complexity Relaxation: The I "NAVSAT GEO + HEO Configuration" Final Report, ESA Contract

N. 6354/85/F/RD(SC)-lJuly 1985, ITALSPAZIO -Rome. Italy.presence of geosynchronous satellites in the proposed con-stellation are expected to ease the satellite tracking function 2. C. Rosetti: "NAVSAT, a Worldwide Civil Satellite Navigationand the system data flow, due to the fact that 3 GEO- System" IAF-83-90.satellites can handle all the required links between the 3. "Study of the User Segment of NAVSAT" Final Report, ESA Contract

Regional Ground Stations and the Master Station. N. 5231/82/F/RD, Racal Decca Ltd. U.K.Cost Saving: Cost reduction of NAVSAT GEO + HEO 4. "Aeromatitime Navigation Receiver Study" Final Report, SEAT Con-

derives mainly from the reduced number of dedicated tract N. 5012/82/F/RD(SC). November 1982, Miller Communicationssatellites and the cost launch sharing both for the multilaunch Systems, Ltd - Kanata, Ontario, Canada.configuration and for piggy-back solution (i.e. navigation 5. "Study of NAVSAT Control Segment Characteristics" Partpackage on host satellites). 1: Elements of a control segment concept. ESA Contract N.

GradualCapital Investment: Due to the fact that the pro- 5501/83/F/RD(SC). National Aerospace Laboratory NLR and DelftGradual Capital Investment: Due to the fact that the pro- Univ. of Technology - The Netherlands.posed NAVSAT GEO + HEO configuration can be set upregionally, offering a continuous 3-D navigation service in 6. Sturza, Mark A. "GPS Navigation Using Three Satellites and a Precise

Clock" Global Positioning System, Papers published in Navigation,selected geographical areas with a reduced number of reprinted by the institute of Navigation, Volume II, Washington DC,satellites, it is possible to implement the system in those 1984, pp 122-132.areas where it is mostly needed without a large capital in-

vestmen. Infatwith GEO naigationpackage and37. "'Accurate Position Measuring Spacecraft Package". WPvestment. In fact with 2 GEO navigation packages and 3 2100: Performance Analysis, Intermediate Report - SENER ContractHEO satellites, full operational capability can be achieved in PS-5420/01/ITAL relevant to ESA Contract N. 6239/85/NL/PP(SC) -

areas where the service is most needed. As time goes by the April 1986. ITALSPAZIO - Rome, Italy. Usystem could be gradually expanded to full global coverage.

1986 William E. Newell Power Electronics Award

Philip L. Hower - Unitrode Corporation

The William E. Newell Power Electronics Award is presented annually by the PowerElectronics Council for outstanding achievement in power electronics. The recipient isjudged to be outstanding in the multi-disciplinary field of power electronics, whichcrosses the technical boundaries of a number of IEEE societies and groups.


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