Digital Beam Synthesis (DBS) For A High Capability Opto .
------------- -----Digital Beam Synthesis (DBS) for a High CapabilityOpto-Electronic Radar (HICAPOR)Study Leaders:Alvin DespainJohn VeseckyJSR-97-230September 1997Approved for public release; distribution unlimited.JASONThe MITRE Corporation1820 Dolley Madison BoulevardMcLean, Virginia 22102-3481(703) 883-6997,D:f Tiiili"tf {5f.T :J'rl i ·:} J1E:l:· :::f-:{i-"·r"---.-.--- . -. --, .App;rO H;1!. .'T.Cx J.t''';;; · : Dlmrt'i:IUI,i1' m\ Un" 1
IIIIIIIIIIIIIIIIIIForm ApprovedOMB No. 0704-0188REPORT DOCUMENTATION PAGEPublic reporting burden for this collection of Information estimated to average 1 hour per response, Including the time for review Instructions, searc hing existing data sources,gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of thiscollection of Information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 JeffersonDavis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget. Paperwork Reduction Project (0704·0188), Washington, DC 20503.1. AGENCY USE ONLY (Leave blank)r'\2. REPORT DATESeptember 25,1997REPORT TYPE AND DATES COVERED5. RJNDING NUMBERS4. TITLE AND SUBTITLEDigital Beam Synthesis (DBS) For A High Capability Opto-ElectronicRadar (IDCAPOR)13-988534-046. AUTHOR{S)A. Despain, J. Vesecky8. PERFORMING ORGANIZATIONREPORT NUMBER7. PERFORMING ORGANIZATION NAME{S) AND ADDRESS(ES)The MITRE CorporationJASON Program Office1820 Dolley Madison BlvdMclean, Virginia 22102JSR-97-23010. SPONSORINGIMONITORINGAGENCY REPORT NUMBER9. SPONSORINGIMONITORING AGENCY NAME{S) AND ADDRESS{ES)Office of Naval ResearchCode 111800 North Quincy StreetArlington, Virginia 22217JSR-97-23011. SUPPLEMENTARY NOTES12a. DISTRIBUTIONIAVAILABIUTY STATEMENT12b. DISTRIBUTION CODEApproved for public release; distribution unlimited.3. ABSTRACT (Maximum 200 words)Digital beam synthesis using a high capability opto-electronic radar (HICAPOR) by Alvin M.Despain and John F. Vesecky. This JASON study investigates the capabilities of HICAPOR bycalculating the antenna beam patterns formed by typical implementations of this concept. Awide variety of para-meter choices are investigated and antenna patterns for HICAPOR arecompared with conventional phased array and true time delay techniques of beam formation.The presentation begins with an introduction of the HICAPOR concept and how it fits within ahigh capability, very wide band radar. This is followed by presentation of a computersimulation of the beam and pulse forming capabilities of HICAPOR over a range of radarparameters. HICAPOR beamforming performance is then compared with the performance ofother radar types. Finally conclusions are drawn and recommendations made. 4. SUBJECT TERMS15. NUMBER OF PAGES16. PRICE CODE7. SECURITY CLASSIFICATIONOF REPORTUnclassifiedNSN7540.(J1-28 50018. SECURITY CLASSIACATIONOF THIS PAGEUnclassified19. SECURITY CLASSIFICATIONOF ABSTRACTUnclassifiedO. LIMITATION OF ABSTRACtSARStandard Form 298 (Rev. 2·89)P,eocribed by ANSI Std. Z39-18288·102
------------ ---- -OutlineDigital beam synthesis using a high capability opto-electronicradar (HICAPOR) by Alvin M. Despain and John F .Vesecky.This JASON study investigates the capabilities of HICAPORby calculating the antenna beam patterns formed by typicalimplementations of this concept. A wide variety of parameter choices are investigated and antenna patterns forHICAPOR are compared with conventional phased array andtrue time delay techniques of beam formation. The presentation begins with an introduction of the HICAPOR conceptand how it fits within a high capability, very wide band radar.This is followed by presentation of a computer simulation ofthe beam and pulse forming capabilities of HICAPOR over arange of radar parameters. HICAPOR beamformingperformance is then compared with the performance of otherradar types. Finally conclusions are drawn andrecommendations made.I JASON HICAPOR1I
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-- -------------- -HICAPOR3
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ,Opto-Electronic Control Conventional Low-Performance Phased ArrayRadar- Simple control of a single transmit beam- Moderate bandwidth, complex waveforms available- Large changes in frequency cause squint of beam for angles offboresight- Single receive beam only- No null steering capability High-Performance, True Time Delay (TTD) SteeringPhased Array Radar- Use of optical delay devices allows large changes in frequencywith no beam squint- Use of optical fibers makes signal transmission easier and moreimmune to interference High-Capability Opto-Electronic Radar (HICAPOR)- Combines optical signal transmission with direct digitalsynthesis of transmit signal at array elementI JASON HICAPORI.4 ;
-- ---------------Optc-Electronic ControlConventional low-performance phased array radar suffers from a variety of shortcomings. In particular phase shift is used to control beam angle and this leads todegradation of the beam shape when frequency is shifted a large amount from thenominal operating frequency. This problem is called beam squint. One way tocorrect the squint problem for very large bandwidths or large changes in operatingfrequency is to use time delay to steer the antenna beam rather than phase shift.Time delay beam steering can be implemented electronically, but the size ofwaveguides and other electronic devices makes the implementation awkward.Optical fibers are very effective in the transmission of very wide bandwidth andtime delay devices, such as the bifodal (a switched, binary tree of fiber optic delaylines), can be used to steer phased array antenna beams. However, there aredrawbacks to optical delay lines, including stability, sensitivity to severeenvironments and production of long delays. Further, improvement can be madeby using optical fibers to transmit microwave signals around the radar, but doingthe time delay (along with waveform generation) by direct digital synthesis at eacharray transmit element.5
The HICAPOR Strawman 'N' Transmit Beams- Transmit waveform synthesis at each array element 'N' Receive Beams- AID conversion at each antenna element Optical Fiber used for:-RF-Clock distributionSynchronizationAID data link to computerComputer link to waveform generator Employ D/A waveform generator for both pulseforming and beam forming Optical Fiber/Devices are NOT used forbeamforming!I JASON HICAPOR,'.I6
------------ ------The HICAPOR StrawmanTo illustrate the HICAPOR concept we construct a strawman design and thencompute the beam formation capability of HICAPOR for a variety of parameters.We also compare the HICAPOR capability with a variety of other options includingconventional phased array radar and true time delay beam steering. In theHICAPOR strawman design optical fiber is used extensively for RF clockdistribution, synchronization, NO data link to computer and computer link towaveform generator. This is illustrated on the following viewgraphs. However,optical fiber/devices are NOT used for beamforming. Instead a electronic digitalO/A is used for both waveform generation and beam formation. This means thatthe waveform timing must be at the 0.1 ns level to accomplish the beam formingfunction. The HICAPOR concept and how it fits into a high capability arrayantenna radar is illustrated in the following viewgraphs.I JASON HICAPOR I7
HICAPOR ArchitectureArrayModuleL.-------.///" /- : IHTSCSTALOAmpOpticalSplitterArrayModule.I")'[fJ -------f ---"7/ J/,l /". .,."'///I'/ArrayModule ---t.rf?',/ /// Pulse \/ ,//Gen.f'I'i A.f'/// /&1'/.--- --------------- . bYkJ//' //'",/,/0 ArrayModuleComputer SystemJASON HICAPOR8------ ------------
- - - - . '- -' - - -' . . - - - - -'HICAPOR ArchitectureThis viewgraph illustrates the radar concept of HICAPOR. Much of the radar isconventional, but advanced components are used in several places. To decreasephase noise for better Doppler discrimination of low cross section targets, a hightemperature superconducting stable local oscillator (HTSC STALO) is used.Communication of RF and digital signals around the radar is done by fiber optics.This includes the master RF carrier signal for radar transmissions, time synchronization signals as well as the digital information needed by the array modules forbeam formation, waveform generation and other radar functions. The receivedradar echo signal is digitized at the array module level and this information istransmitted by optical fiber to the radar's computer system for receive beamformation, Doppler proceSSing and other data analysis functions.I JASON HICAPOR I9
Array Module--OpticalFiberRF & SyncWaveform Generator"JlOpticalFiberData Link-. ---T/RAID/ AntennaElement--- -----------4 JASONHICAPOR., ,,,1
1- .; ' ,!Array ModuleEach array module contains devices for generation of the radar transmit signal aswell as the AID conversion of the received echo signal. The waveform generatorreceives RF carrier, synchronization and waveform and beam forming instructionsby optical fiber links to the radar computer system. The synchronization pulsebegins each pulse forming process. This generator then manufactures the outputsignal to be transmitted by the particular array module at say 10 GHz. Thisgenerator is the heart of the HICAPOR concept and is described in more detail onthe following viewgraphs. On receive, the received signal is down converted tobaseband and then digitized with 15 bit accuracy at a typical bandwidth of say 10MHz. Although the individual echo signals at each array module are digitized atonly 15 bit accuracy, the aggregate accuracy of the combination of many arraymodule signals in the beamforming process increases the accuracy significantly fora large array. For a large array this increased accuracy by combination can resultin 20 significant bits and a dynamic range of say 120 dB in the Doppler-processedsignal.I JASON HICAPOR I11
Waveform GeneratorOpticalFiberRF & Sync- - - - - - - - - RF CarrierL.-----I ------t) PIN SwitchesShift ClockBeam 1ToT/RShift Register,. .Beam 2Shift RegisterOpticalFiberData LinkJASONHICAPOR- - - - -- - - - : . - - ,- -) - - - 12'
- - - - - - - - - - - - -- -, - - :- Waveform GeneratorThe waveform generator is controlled by a digital data stream providing thesuccessive loads to a large shift register (bottom left). This data stream contains theinformation necessary to generate the output waveform, complete in both waveformcharacteristics and location in time so that the desired beam is formed. The uppershift register contains the information for one complete output pulse. Thus, atinstant of time, i.e. each 0.1 ns interval, this upper shift register shifts out eightbinary numbers to control the eight PIN diodes. Throughout the radar pulse thisupper shift register keeps shifting out 8 bit sequences to control the PIN diodes. Fora 100 ns pulse length this would amount to 1000 8-bit sequences. When the pulseis finished the lower shift register loads the upper register with the information for thenext pulse. This can be done at leisure since there is typically about 1 ms betweenpulses. The fact that each 8-bit sequence controls the signal phase allows thebeam to be steered with high efficiency. The effects of changing the size of the shiftregister and the number of PIN diode control points is explored in the viewgraphsthat follow somewhat further on. In this implementation we show how multiple beamcapability is introduced. Namely, a second row of PIN diodes uses the same RFcarrier and phase shifts, but with different 8-bit sequences corresponding to anotherwaveform in a different direction. Each additional beam requires a doubling of thesize of the upper shift register.I JASON HICAPOR I13
Simple WaveformsCarrier waveform---. TimeSync Pulse (loads SR and begins shift-out) O --------------------------------------- Time Dela Time'Phase'PIN Control Data Stream out of 00000------------------------------------------ TimePIN Switch Waveform----------- -------- ----------------------------- TimeDesired Waveform------------------------- . Time JASONHICAPOR------------------14
------------------Simple WaveformsHere we illustrate the HICAPOR pulse formation scheme with a simple waveformconsisting of a single pulse that lasts for eleven shift register clock periods. At thetop is the carrier waveform that supplies the signal to the phase shifters. The nexttime series below shows the sync pulse that loads the upper shift register from thelower one and begins the shift out to form one complete pulse. The third timeseries from the top shows which PIN diode is turned on. In this case all the PINdiodes are turned off except number two which is turned on for eleven shift outperiods. The fourth time series shows the switch waveform for diode number two.The output waveform is shown at the bottom of the viewgraph.I JASON HICAPOR I15
Waveforms-Two Beams---. TimeCarrier waveformI""Sync Pulse (loads SR and begins shift-out) ---------------------------------- TimeTim elay 1/ h L T i m e D 'Phase 2'PIN Control Data Stream out of 000000-------------------------------------- TimePIN Switch WaveformI----------- I------- ---------------------- TimePIN Switch WaveformI---- I-------- -------------------------- TimeDesired Waveform---- H H H H H H ----------------------- TimeI JASON HICAPORI------------------16
------------------Waveforms-Two BeamsHere we illustrate the H ICAPOR pulse formation scheme for two independentbeams. At the top is the carrier waveform that supplies the signal to the phaseshifters. The next time series below shows the sync pulse that loads the upper shiftregister from the lower one and begins the shift out to form one complete pulse.The third time series from the top shows which PIN diodes are turned on. At firstonly one pulse is specified to be on. Soon codes in the shift register begin tospecify both pulses. Later the first pulse ends and finally the output is specified tobe zero. The fourth time series shows the switch waveform for the pin diodes. Theoutput waveform is shown at the bottom of the viewgraph.I JASON HICAPOR I17
Waveforms-Phase Encoding[Pulse Compression] Carrier waveformv VVV VVVV,---II TimeVSync Pulse (loads SR and begins shift-out) -------- TimeTime Dela\o000'Phase'714 2PIN Control Data Stream out of ----------------------------- Time------------ rl- I-- ---------------------------------------- Time---------------- ---------------------------------------- Time-------------- r l-- ------------1IrPIN Switch aveforms ---------- Time11 . . . - ---1.- Time.-. Time.-. Time-.TimeJASON HICAPOR18
------------------Waveforms-Phase Encoding[Pulse Compression]Here we illustrate the HICAPOR pulse formation scheme for pulse compression. Atthe top is the carrier waveform that supplies the signal to the phase shifters. Thenext time series below shows the sync pulse that loads the upper shift register fromthe lower one and begins the shift out to form one complete pulse. Different codesare used to specify which phase to transmit at each time. The next set of timeseries from the top shows which PIN diodes are turned on. The output wave-form isshown at the bottom of the viewgraph.I JASON HICAPOR I19
Examples for Simple Pulse RadarsrA/AntennaElementClassic Phased Array16 taps of a delay lineu Time Delay Array / : :I ; I; : taps UL EDRF (1OGH ) I .1 APS. 1 . .I/TTTT TT TTTT TT TT TT . .6 s. TT TT TT TT TT TT TT TTI. 1Delay LineHICAPOR16 taps &100 stage shift register10 GHz ClockSimple & SolvesSquint problem,adds flexibilityDelay LinePULSED RF (10 GHz) ,:-.problekm: fCf bmplexltY!Many mOl er(16 Phases)"TTT'Problem: Squinting! Parametersf 10GHzPhase Res. nIBer100 stage shift r e rDelay liner -;;; TTTTTTT--RFCARRIER (10 GHz) -- IDelay Line 16 TAPS.t1-: OFFTAPJASON HICAPOR------------------?J
------------------Examples for Simple Pulse RadarThis viewgraph illustrates the important differences between the classic phasedarray, the true time delay (TTD) array and the HICAPOR concept. In each case weconsider an individual array module and show what is required to generate thetransmitted signal for some desired antenna beam direction. The classic phasedarray at the top the antenna can be hooked to any of 16 taps on a delay line. Thedelay line taps are such that a phase change of 360 0 is distributed over the 16taps. Thus, the delay line acts like a phase shifter, which is what we want for thiscomparison. The problem for the classic phase array antenna is the squintingproblem, discussed above. In the time delay array case the delay line requiresenough taps to allow each element to select the correct delay. For a 100 elementarray this requirement means that the tapped delay line at each element must havesome 16 x 100 delays. Such a delay line can be implemented using fiber opticcables and optical switches. Schemes, such as the bifodal which switches in or outa number of optical fibers to construct the correct delay, can reduce the complexity.Still the problem is one of complexity as the optical delay lines are long if thechange in time delay is done by changing optical wavelength or many opticalI JASON HICAPOR I21
Examples for Simple Pulse Radar(concluded)switches are required if one changes delay by propagating through a differentphysical set of fibers. The HICAPOR concept uses a 100 stage shift register todigitally control the delay and to digitally control the 16 stage delay line as shown inthe viewgraph. Thus, the HICAPOR system uses optical fibers where they can dothe most good, i.e. in digital and analog signal communication within the radar. Thedigital waveform generator can be made very small and thus fit nicely within anarray module, whereas current optical delay devices would make this fit much moredifficult. We also think that the cost of H ICAPOR modules would be significantlyless than their optical counterparts.I JASON HICAPOR I------------------22
------------------- - - - -SIMULATION OF THE DIGITALBEAM SYNTHESIS SYSTEM23
Digital Beam Synthesis (DBS) DBS is a component of the HICAPOR system thatforms a RADAR transmitted beam. DBS is an invention to greatly reduces cost and sizeof a true-time delay beamformer. DBS separately modulates a carrier for each arrayantenna element at exactly the right time for thatelement. In DBS delay is provided by a digital circuit undercomputer control. A shift register is one example of such a digitalcontrol circuit. One form of DBS employs a vernier scheme such thatthe shift register provides a control character thatselects a desired phase of the RF carrier.I JASON HICAPOR J------------------24
------------------Digital Beam Synthesis (DBS)The DBS invention greatly reduces the cost and size of RADAR systems bymoving the modulation process after the delay process. Thus the delays can bespecified in a simple digital shift register or other digital circuit under computercontrol.I JASON HICAPOR I25
Digital Representation DBS, being digital, employs discrete stepapproximations for the radar signals. If the steps are too gross, error artifacts willappear in the beam pattern. The DBS and six other beam forming systemshave been simulated. Artifacts unique only to DBS can be determinedby comparison to the other systems.I JASON HICAPORI------------------26
------------------Digital RepresentationThe DBS system(as well as other systems) employ discrete approximations forthe RADAR signals. If these are too crude, then undesireable artifacts will appearin the transmitted RADAR beam. By simulating DBS and other systems, thesource of the artifacts can be determined.I JASON HICAPOR I27
Simulation Errors Simulation method: Direct, time-domaintrapezoidal integration of antenna elementsignals. Time-step resolution is an issue:- If too small, simulation cost is too high- If too large, simulation is not accurate. A number of time step sizes were tried. Result: 0.125 nanoseconds was chosen. An example at 0.25 ns is shown to validate thischoice. ------------------- JASON HICAPORI28----------------- -
------------------Simulation ErrorsComputer simulation is employed to study the different beam forming schemesand their parameter settings. To get an accurate simulation the simulation timestep cannot be too big. For the range of parameters of interest, a simulated timestep of 0.125 nanoseconds is the right choice. This will be shown in a later plot.I JASON HICAPOR I29
Beam Pattern - Antenna TypesTCWDCW90TTD0PHADPADBSDOD.0'"012060-10 J.)enc0a.en30-20 J.)a:('ljcc-30 -50.0210330240300270JASON HICAPOR------------------30
------------------Beam Pattern - Antenna TypesThis plot shows a nominal beam steered to zero degrees for each of the seven beam formingmethods studied. These are:TCW: True Carrier Wave beam forming.When an RF carrier is modulated, with a pulse for example, the resulting signal has a widerbandwidth than the original carrier. As a result beams formed on a pulsed modulated carrierhave additional artifacts (side-lobes, etc . ) TCW is thus shown so comparisons can be made.DCW: Discrete Carrier Wave beam forming.If the phases of each carrier wave at each antenna element are set in discrete steps, artifactscan appear in the beam. Simulation of the DCW provides a measure of the required number ofdiscrete phases needed for accurate beam forming.PHA: Phased Array. pulsed RADAR beam forming.This is the classic phased array RADAR with continuous setting of each phase at each antennaelement.DPA: Discrete Phased Array beam forming.This is the classic PHA but with discrete settings of each phase angle.I JASON HICAPOR31.I
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ,Beam Pattern - Antenna Types{concluded}TTD: True Time Delay beam forming.Beams are formed by first pulse modulating a carrier, then delaying a copy of it for eachantenna element. Beam steering is accomplished by providing the correct delay for eachelement.DBS: Digital Beam Synthesis beam forming.This is beam forming by separately modulating an RF carrier at each element. Time delay iscontrolled by a digital shift register for each element. Hence, time delays are discrete.DDD: Digital-Carrier and Digital Delay. beam forming.It may be desirable to employ digitally synthesized carrier waves in RADAR systems. DDDprovides various discrete approximations to sine waves to test the DBS system on these typesof carriers.I JASON HICAPORI------------------32
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Beam Pattern900 10 20 - . - 0;-:j(}12060.c"'040 -------"- Steered Elevation BeamsQ)enc:)0-10060 Q.enQ)a:30-20ct!cc--c«Q)-30-40PARAMETERS. - 5.010.20.0240300270-----JASON HICAPOR-----------34
------------------Beam Pattern - Steered Elevation BeamsThis antenna response plot illustrates the computer simulation of the base-linecase. All the other plots are variants that explore different issues with the OBSscheme.The legend for the individual plots is shown in the upper left-hand side of thefigure. For this figure, the individual plots are for beams steered to point toelevation angles of 0 , 10 , 20 , 30 , 40 , 50 , and 60 .The parameter settings for this base- line case are shown on the lower left-handside of the figure.For this base-line case, a simple pulse is modeled. The carrier frequency is 1GHz, the antenna is a 1-0 linear array of 100 elements spaced at /",/2 (0.5 ns),there is no tapering, and the OBS employs shift registers of length 50 and 8 phaseangles.I JASON HICAPOR I35
Beam Pattern -Steered Elevation Beams[ Time Resolution: 0.25 ]90.w. .0 10 20 . .,----- 0:::\0'12060.c40 5060 "'0-10 D(f)c0Q.(f)30-20 Da::cocc.c-30 270JASON HICAPOR------------------36
------------------Beam Pattern - Steered Elevation Beams[Time Resolution: 0.25]The simulation method employed is direct time-domain trapezoidal integration of allthe signals produced by all the antenna elements.An issue then is the resolution of the numeric integration. This figure shows theresults of employing a time-step of 0.25 nanoseconds (ns); that is, twice as long asthe step of 0.125 ns employed in all the other studies. It can be seen that very littledifference results. If the time-step is increased to 0.5 nsec, noticeable artifactsappear. (This result is not shown.) The conclusion is that 0.125 nsec is the propertime step to employ in the calculations.I JASON HICAPOR I37
Beam Pattern- Steered Elevation Beams [2-D]900 10'020 , I.012060'. )\.)-.Q40'"'0'll.)Q)60 c0a.(f))-10(f)30-20Q)a:cocc-30Q)- -'C«-40PARAMETERS-- . - .- 20.0210330240300270JASON HICAPOR------------------38
-- ----------------Beam Pattern - Steered Elevation Beams [2-D]This plot is for a two dimensional antenna of 35 by 35 elements spaced at /",/2. Thisshows beams steered to elevation angles from 0 to 60 . The relatively large sidelobes at 300 result from the steered azirmuth angle being set to 45 , and theelevation angle to 60 .I JASON HICAPOR39I
Beam Pattern- Steered Elevation Beams[ 2-D, Full Taper]0 10 20 09012060';('l--40 .0"060 c-10----- .())(f)0Cl.30-20(f)())a:cocc())-30 -'C CPARAMETERS-- .- 5.060.045.045.020.21.0240300JASON H ICAPOR-- ---------------4lil1li
------------------Beam Pattern - Steered Elevation Beams[ 2-D, Full Taper]This shows what tapering can do for the close-in side lobes. It does suppress themat the cost of a wider main beam. Later the amount of tapering will be varied tobetter illustrate this. Note that at extreme directions (e.g. 300 ) and extremesteering (60 ) the side lobes are not suppressed, they are enhanced! Simpleamptitude tapering will not suppress these side lobes.I JASON HICAPOR I41
Beam Pattern- Steered Azimuth [2-D]900 10 20 ,----,-- :30'40 012060.Cl"0!:SU) /7-10Q)!J)c60 00!J).f-20. Q)cr: cc-30--cQ)«I'J'l2.:, -40(.1/,"-f: (. :AZMDIR6DBS850350.51.05.07 - /''P'210133045.045.060.045.045.020.20.02403004.--- ----- --- -- 270JASON HICAPOR
-- ------------ ---Beam Pattern - Steered Azmiuth [2-D]This plot is for a two dimensional antenna of 35 to 35 elements spaced at 'A/2. Theelevation angle is set to 45 . The beam is then steered through 0 to 60 in azimuth.Note the beam broadening due to both the 45 elevation and various azimuthsteerings.I JASON HICAPOR I43
- - - - . - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ,Beam Pattern- Antenna Taper900.00.2---- 0.30.-.----0.7 ----- -.0"0iJ. 31.012060-10 D(j)c00.30-20(j) Da:ctlcc D.C«-30-40PARAMETERS--- . ------- . RTAPER0-50,6.((DBS !!"!( 8501000.51.05.071J 21033045.045.060.045.045.010.20.0240300270.------ ------ - --JASON HICAPOR'14-
-- - ----- - ---Beam Pattern - Antenna TaperTapering the antenna array reduces the antenna side-lobes at the cost of wideningthe main beam. This figure shows no tapering and six uniform levels of tapering.The full tapering is a 100% raised cosine function.I JASON HICAPOR I45
Beam Pattern- Number of Elements/Dimension149028- - - 43---- -.-0 ) -/12060Ll"'071Q)(fJc100-100a.(fJQ)a:30-20ct:IccQ) -'-30C«-40PARAMETERS--- . . - . 45.00.20.0240300270.-.-- - ----- - - --JASON HICAPOR46'
Beam Pattern - Number of Elements DimensionHere the number of antenna elements is varied from 14 to 100 elements in 7 steps.With only 14 elements, the beam is wide and the side lobes are large.I JASON HICAPOR I47
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ,Beam Pattern - Frequencies.-- ------.--0.14GHz0.29 GHz0.43 GHzOS? GH 0.71 GHz;'), ,36( .! '-l?:1.0 GHz900.0"'012060-10CD(/)c00.30-20(/)CDa:cocc-30Q) -'C«-40PARAMETERS--------------.--STUDYMXCASESAN
The MITRE Corporation REPORT NUMBER JASON Program Office 1820 Dolley Madison Blvd JSR-97-230 Mclean, Virginia 22102 9. SPONSORINGIMONITORING AGENCY NAME{S) AND ADDRESS{ES) 10. SPONSORINGIMONITORING Office of Naval Research AGENCY REPORT NUMBER Code 111 800 North Quincy Street JSR-97-230 Arlington, Virginia 22217 11. SUPPLEMENTARY NOTES 12a.
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