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Ambiguities are proportional to the strength of the offending backscatter, and as such, they contribute to the multiplicative noise* ratio (MNR) of the system. Antenna sidelobes and ambiguities are further suppressed by appropriate weighting in the processor. The trade-off is lower MNR, at the expense of broader impulse response width (IRW). |
M. Weiner, Chapter 9,2 courtesy SciTech ) ch23.indd 24 12/20/07 2:21:42 PMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2008 The McGraw-Hill Companies. All rights reserved. |
21. no. I. |
Proc. IRE. vol. |
FM-CW was applied to the measurement of the height of the ionosphere in the 1920s32 and as an aircraft altimeter in the 1930s.33 FM-CW altimeter. The FM-CW radar principle is used in the aircraft radio altimeter to measure height above the surface of the earth. The large backscatter cross scction and the relatively short ranges required of altimeters permit low transmitter power and low antenna gain. |
7 SAW transducer types: ( a) dispersive output, ( b) both input and output dispersive, and (c) dispersive reflections ch08.indd 10 12/20/07 12:49:54 PMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2008 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Pulse Compression Radar. |
ORY BEHIND THE METHOD AND HOW IT IS APPLIED TO THE ANALYSIS OF REFLECTOR ANTENNAS n 0/ IS A VERY GENERAL hHIGH FREQUENCYv ANALYSIS METHOD THAT GENERALLY PROVIDES HIGH FIDELITY PATTERN PREDICTIONS FOR MOST REFLECTOR SYSTEMS AS LONG AS THE REFLECTOR DIMEN |
10. Lewis, B. L., J.P. |
#7 RADAR 4HIS #7 RADAR USES FREQUENCY MODULATION OF THE WAVEFORM TO ALLOW A RANGE MEASUREMENT 3URVEILLANCE RADAR !LTHOUGH A DICTIONARY MIGHT NOT DEFINE SURVEILLANCE THIS WAY A SURVEILLANCE RADAR IS ONE THAT DETECTS THE PRESENCE OF A TARGET SUCH AS AN AIRCRAFT OR A SHIP AND DETERMINES ITS LOCATION IN RANGE AND ANGLE )T CAN ALSO OBSERVE THE TARGET OVER A PERIOD OF TIME SO AS TO OBTAIN ITS TRACK -OVING TARGET INDICATION -4) 4HIS IS A PULSE RADAR THAT DETECTS MOVING TARGETS IN CLUTTER BY USING A LOW PULSE REPETITION FREQUENCY 02& THAT USUALLY HAS NO RANGE AMBIGUITIES )T DOES HAVE AMBIGUITIES IN THE DOPPLER DOMAIN THAT RESULT IN SO |
F.: The Continuous-Cathode (Emitting.-Sole) Crossed-Field Amplifier, Proc. IEEE, vol 61. pp 330 356, March. |
GRAZING CONDITIONS THE MODELS MUST ACCOUNT FOR SHADOWING 3IMPLIFIED -ODELS %ARLY RADAR THEORIES FOR GROUND RETURN ASSUMED AS IN OPTICS THAT MANY TARGETS COULD BE DESCRIBED BY A ,AMBERT |
10 5 0 1 2 5 10 20 50 100(a)(b) (c) (d)(e) f/GHz a) Bi-polar Transistor-Amplifier b) FET-Amplifier c) GaAs-Schottky-Mixer, d) Parametric Amplifier e) P-HEMT Amplifier. Radar System Engineering Chapter 6 – Radar Receiver Noise and Target Detection 30 The antenna noise temperature TAnt, which takes these noise contributions into consideration, can be calculated, with help from (6.5), by the convolution of the background temperature TB with the squared directivity € C(θ,ϕ). Figure 6.2 shows the convolution. |
In particular, hydrogen can be present in the interior metal plating and has been known to cause long-term reliability concerns in some GaAs amplifiers. One solution involves the use of an internal hydrogen getter to counterbalance the reliability impact. A getter is a material included in the module housing to absorb residual hydrogen. |
J. I).: "Antennas," McGraw-Hill Hook Company, New York. 1950. |
MEASURING RADARS ! DOPPLER TRACKING SYSTEM THAT AUTOMATICALLY TRACKS THE FREQUENCY OF A SPECTRAL LINE OF THE ECHO IS SUBJECTED TO TWO PROBLEMS THERE IS THE POSSIBILITY OF LOCKING ON A FALSE LINE CAUSED BY MOVING PARTS OF THE TARGET AND WHEN PROPERLY LOCKED ONTO THE AIRFRAME DOPPLER SPECTRUM THE DOPPLER READING WILL BE NOISY AS DEFINED BY THE RANDOM FLUCTUATION IN INSTANTANEOUS FREQUENCY AS OBSERVED BY THE SPREAD OF THE DOP |
nckefi. G., and G. W. |
Rodriguez and J. M. Martin, “Theory and design of interferometric synthetic aperture radar,” IEE Proceedings , Part F, vol. |
The beat frequency is amplified and limited to remove any amplitude fluctuations. The frequency of the amplitude-limited beat note is measured with a cycle-counting frequency meter calibrated in distance. In the above, the target was assumed to be stationary. |
RING ASSEMBLY WHICH ENDED ITS MISSION IN /CTOBER AFTER ONLY THREE MONTHS OF OPERATION 3)2 3!2 3ERIES 4HE 3HUTTLE IMAGING RADARS 3)2 |
2 ......... 0.52 3 ~0.5 0.63 0.17 0.7 0.51053 0.17 0.7-5.0 06120 0.02 4.7 145 01 1.030.0 I161.7X._----. RADAR CLUTTER 497 well as the fact that radar waves can penetrate the surface and can be scattered from discon- tinuities underneath the surface. |
IMENTAL 2OCKS SOILS AND CONCRETE ARE COMPLEX MATERIALS COMPOSED OF MANY DIFFERENT MINERALS IN WIDELY VARYING PROPORTIONS AND THEIR DIELECTRIC PARAMETERS MAY DIFFER GREATLY EVEN WITHIN MATERIALS THAT ARE NOMINALLY SIMILAR -OST EARTH MATERIALS CONTAIN MOISTURE USUALLY WITH SOME MEASURE OF SALINITY 3INCE THE RELATIVE PERMITTIVITY OF WATER IS IN THE ORDER OF EVEN SMALL AMOUNTS OF MOISTURE CAUSE A SIGNIFICANT INCREASE OF THE RELATIVE PERMITTIVITY OF THE MATERIAL ! LARGE NUMBER OF WORKERS HAVE INVESTI |
FIELD PARTS REPLACEMENT (OWEVER THE PAYOFF FROM RADARS IN SPACE MORE THAN COMPENSATES FOR THESE CHALLENGES SINCE SPACE OFFERS A UNIQUE PERSPECTIVE FOR %ARTH OBSERVATION AND IS AN ESSENTIAL VIEWPOINT FOR LUNAR OR PLANETARY EXPLORATION #OVERED AND /MITTED 4OPICS 4HIS CHAPTER INTRODUCES SPACE |
440 INTRODUCTION TO RADAR SYSTEMS 45. Hynes, R., and R. E. |
The TEM horn has ultrawideband capabilities from 200 MHz to 4 GHz. It is positioned above a metallic target buried in the ground as shown in Figure 21.12. The distance between the horn aperture and the air-ground, interface is 25 cm (different from the earlier model). |
Themeansquarevalue(m2)ofthecurrent whenmultiplied bytheresistancet givesthemeanpower.Themeansquarevalueofvoltage timestheconductance isalsothemeanpower.Thevariance isdefined as Il2=(12=«(x-/IId2)"=f(x-11Id21'(x)c1x=1112-11Ii=(x2).v-(x);v(2.14) -co Thevariance isthemeansquaredeviation ofxaboutitsmeanandissometimes calledthe secOIldcentralmoment.Iftherandom variable isanoisecurrent, theproductofthevariance andresistance givesthemeanpowerofthea-ccomponent. Thesquarerootofthevariance (Jis calledthestandard deviation andistheroot-mean-square (rms)valueofthea-ccomponent. Weshallconsider fourexamples ofprobability-density functions: theuniform, gaussian, Rayleigh. |
A.. and H. T. |
1)obson: Radar Characteristics of Rirds in Flight. Scic~rtc.cs. vol. |
TheFTC,orfasttime-constant, actsasadifferen tiatingcircuit"orhigh-pass filter,toremovethemeanvalueoftheclutterornoise.This function canbeobtained withamoresophisticated filterconsisting ofaparallelcombination ofintegrator andsubtractor.83Theintegrator isanarrow-band filterthataverages theorderof tenrange-resolution cellstoestablish thebackground level.Areceiver implemented inthis manner hasbeencalledalog-CFAR.' ThetermLOGjCFAR hasbeenappliedtothecell averaging CFARwhich-ispreceded Iby:alogarithmic detector.84Thenormalization ofthe threshold isaccomplished inthe'COGjCFAR bysubtraction ratherthanbydivision asinthe conventionalcell-averaging CFAR~Also,theLOGjCF ARiscapableofoperating overalarger dynamic rangeofbackground noiselevels,butithaspoorerdetectability for'thesamenumber ofreference noisesamples thantheconventional cell-averaging CFAR.. DETECTION OF RADAR SIGNALS IN NOISE 3% CFAR is widely used to prevent clutter and noise interference from saturating the display of an ordinary radar and preventing targets from being obscured. It is also needed in ADT, or track-while-scan systems, to prevent the tracking computer from being overloaded by extra- neous clutter targets or noise. |
DOMAIN RADAR TRANSMITS ON A REPETITIVE BASIS A SHORT DURATION IMPULSE #ONSEQUENTLY ITS PEAK POWER IS SIGNIFICANTLY GREATER THAN ITS MEAN POWER 4HIS IS NOT THE CASE WITH STEPPED FREQUENCY WHOSE RADIATED POWER PER SPECTRAL LINE IS HIGHER THAN THE TIME |
CALIBRATING AND THEREFORE RELATIVELY ROBUST IN RESPONSE TO SUCH IMPERFECTIONS )N BRIEF UNDER THE CONDITION THAT R (( R 66 THE MEAN SIGNAL LEVEL IN THE TWO RECEIVE CHANNELS SHOULD BE EQUAL )N TERMS OF THE 3TOKES PARAMETERS 3 4HE ( AND 6 BACKSCATTER COEFFICIENTS WILL ALWAYS BE EQUIVALENT WHEN THE RADARS ILLUMINATION IS PERPENDICULAR TO THE SURFACE (ENCE ANY HYBRID |
25–44, 281–298. 11. D. |
FIG.927.-Four-way r-fswitch used intheAN/MPG-l. The principal elements oftheantenna area5-by15-ft grating reflec- torwhich stands onend, an8-by2-byl-ft convoluted parallel-plate horn whose aperture is5ftfrom thereflector, and arotating waveguide feeding thehorn. The feed, which does not show inFig. |
The filter whose frequency-response function is given by Eq. ( 10.1) has been called the North filter, the conjugate filter, or more usually the matched filter. It has also been called the Fourier transform criterion. |
NOISE RATIOS AND IS SPECIFIED BY XJ MXJ K XJ KI II KM IN |
The usual detection criteria employ the concept of direct probabil- ity, which describes the chance of an event happening on a given hypothesis. For example, the probability that a particular radar will detect a certain target under specified conditions is a direct probability. On the other hand, if an event actually happens, the problem of forming the best estimate of the cause of the event is a problem in inverse probability. |
In order to obtain the required short-range performance, it transmits a frame of pulses with differing lengths. Each pulse within the frame is optimized to cover a specified range bracket. Overall, the pulse sequence completely covers the instrumented range and ensures that the IMO specified minimum range requirement is met. |
The output from one of the antennas was used for transmission and for provid- ing the range information. with such an arrangement it was difficult to obtain the desired aperture illuminations and to maintain a stable boresight. A more satisfactory method of operation is to form the sum and difference patterns in the RF and to process the signals as in a conventional amplitude-comparison monopulse radar. |
L. N.: " Radar- System Engineering," McGraw-Hill Book Co., New York. 1947, pp. |
Turnstile junc- tions7 achieve isolations as high as 40 to 60 dB. The use of orthogonal polarizations for transmitting and receiving is limited to short- range radars because of the relatively small amount of isolation that can be obtained.' An important factor which limits the use of isolation devices with a common antenna is the reflections produced in the transmission line by the antenna. The antenna can never be perfectly matched to free space, and there will always be some transmitted signal reflected back toward the receiver. |
The LFM waveform has a knife-edge ambiguity function with contours that are approximately elliptical with a major axis defined by the line v = at, where a = ± B/T is the LFM slope. This property introduces range-doppler coupling at the matched filter output causing the matched filter output peak to occur earlier in time for a target with a positive doppler frequency compared to a stationary target at the same range, assuming a positive linear frequency modulation slope and later in time for a negative slope. The compressed pulse shape and SNR are tolerant to doppler shift for the LFM waveform. |
2AO BOUND FOR ANGULAR ESTIMATES FOR FLUCTUATING AND NONFLUCTUATING TARGETS R IS THE STANDARD DEVIATION OF THE ESTIMATION ERROR AND . IS THE NUMBER OF PULSES WITHIN THE |
SENTS O THE NEXT BIT REPRESENTS O AND SO ON )N THE PHASE ACCUMULATOR THE TUN |
PULSE PERIODS FROM A SINGLE FREQUENCY REFERENCE 4HIS FULLY COHERENT ARCHITECTURE INSURES THAT BOTH THE DESIRED FREQUENCIES AND ALL THE INTERNALLY GENERATED SPURIOUS SIGNALS ARE COHERENT ELIMINATING THE DEGRADATION OF CLUTTER REJECTION -ANY RADAR SYSTEMS ARE PSEUDO |
Thus, when the grid draws current during astrong signal, itdoes not accumulate abias; hence the gain isnot reduced and the amplifier remains sensitive toweak signals. The gain Gofthesingle-tuned stage shown inFig. 12.6 isgiven bythe expression G=g.RL, (2) combined response ofthevideo andi-famplifier) willbetaken autheequivalent i-f amplifier bandwidth unless otherwise stated.. |
15.7. It can be seen that filters 3 and 4 will provide significant suppression of both clutter sources. FIG. |
On the other hand, a rough surface will tend to break upthe reflection, and will improve the strength of echoes returned from thosetargets whose shape and aspect normally give weak echoes. Composition The ability of various substances to reflect radar pulses depends on the intrinsic electrical properties of those substances. Thus metal and water aregood reflectors. |
S #)4 AND |
Therefore, while the antenna is radiating less power, individual components must be designed to handle more peak power. With antennas that do not scan, the mismatch may often be tuned out by conventional tech - niques, preferably at a point as close to the source of the mismatch as possible. In a scanning array, the impedance of a radiating element varies as the array is scanned, and the matching problem is considerably more complicated. |
Iftheleakage current at“cutoff” amounts. ‘it. -@,,’@ (ii)’#’tF 5D21 715B 829 3E29 3D21 i .“......---- -....”..—..-.!.—...—-— -—. |
When this materml isdispensed from aircraft, large volumes of space canbefilled with it.Itfalls ataspeed ofonly afewmales perhour, Tbe strong signals itreturns soeffectively mask theradar signals from aircraft that arc intbemidst ofacloud ofwindow that several tons ofaluminum used tohedispensed. 82 PROPERTIES OFRADAR TARGETS [SEC. 310 FIG. |
AP-18, pp. 83–88, January 1970. 81. |
RANGE PATROL AIRCRAFT $URING THE LATTER PART OF 7ORLD 7AR )) AIRBOR NE EARLY |
Ê/ |
(2.39b) The probability-density function assumed in cases l and 2 applies to a complex target consisting of many independent scatterers of approximately equal echoing areas. Although, in theory, the number of independent scatterers must be essentially infinite, in practice the number may be as few as four or five. The probability-density function assumed in cases 3 and 4 is more indicative of targets that can be represented as one large rellector together with other small rellectors. |
PP n " $ 3TEINBERG h(IGH ANGULAR MICROWAVE RESOLUTION FROM DISTORTED ARRAYS v 0ROC )NT #OMPUT #ONF VOL 4 # #HESTON AND * &RANK h0HASED ARRAY ANTENNAS v #HAPTER IN 2ADAR (ANDBOOK - ) 3KOLNIK ED ND %D .EW 9ORK -C'RAW |
BUNCHED IN THEIR CYCLOTRON ORBITS AS A RESULT OF THE RELATIVISTIC MASS CHANGE OF THE ELECTRONS 4HE GYROTRON BUNCHING OPERATION ALSO CAN BE OBTAINED AT HARMONICS OF THE CYCLOTRON FREQUENCY BUT THERE CAN BE PROBLEMS WITH HIGHER CIRCUIT LOSSES AND COMPETITION WITH MODES OPERATING AT LOWER HARMONICS SO THAT MOST HIGH |
Automatic Noise-Level Control. Another widely employed use for AGC is to maintain a desired level of receiver noise at the A/D converter. As will be described in Section 6.10, too little noise relative to the quantization increment of the A/D con - verter causes a loss in sensitivity. |
Side-lobe cancelation in DInSAR pixel selection with SVA. IEEE Geosci. Remote Sens. |
6.3>b performs this . («) (f) (g) FIG. 6.3 Common reflector antenna types, (a) Paraboloid, (b) Parabolic cylinder, (c) Shaped, (c/) Stacked beam, (e) Monopulse. |
COVERED AREAS OF 'REENLAND 4HESE RESULTS ARE CONSISTENT WITH PREDICTED SCATTERING COEFFICIENT VARIATIONS BASED ON THE TOPOGRAPHY AND THE ELECTRICAL PROPERTIES OF THE SURFACES 3UBSEQUENTLY OBSERVA |
LOG |
Thus the circuit isstable and uncritical; itonly remains to beshown that the noise contr- ibution ofthe second triode is small. This isnotobvious, and a rigorous proof isbeyond thescope ofthis book (see Vol. 18ofthis series). |
MENT FOR THE INCUMBENT HARDWARE 2ADAR TRANSMIT WAVEFORMS THAT PREVIOUSLY HAD BEEN ARCHITECTED TO MAKE OPTIMUM USE OF THE HIGH PEAK POWER AND LOW DUTY CYCLE CAPABILITY OF THE TUBE NO LONGER FAVOR THE SOLID |
TO |
Relative range acc11raq,-typically.2to A km for a target location relative to a known location observed hy the same radar. Ahsolute range acrnracy-- lO to 20 km, assuming real-time analysis of the propagation path is made. Angil' resoilltion determined hy the beam width; it can be less than 1 ° which corresponds to 50 km at a distance of 3000 km. |
CLUTTER RATIO IMPROVEMENT AGAINST CLUTTER AT ZERO DOPPLER AS A FUNCTION OF TARGET DOPPLER FREQUENCY /NLY THE RESPONSE OF THE FILTER PROVIDING THE GREATEST IMPROVEMENT IS PLOTTED AT EACH TARGET DOPPLER &OR COMPARISON THE OPTIMUM CURVE FROM &IGURE IS SHOWN BY A BROKEN LINE AND THUS PROVIDES A DIRECT ASSESSMENT OF HOW WELL THE #HEBYSHEV FILTER DESIGN PERFORMS AGAINST A GIVEN CLUTTER MODEL !LSO SHOWN IS THE AVERAGE 3#2 IMPROVEMENT FOR BOTH THE OPTIMUM AND THE #HEBYSHEV FILTER BANK &)'52% #HEBYSHEV &)2 FILTER DESIGN WITH D" DOPPLER SIDELOBES . |
Performance Analysis of L-Band Geosynchronous SAR Imaging in the Presence of Ionospheric Scintillation. IEEE T rans. Geosci. |
Symons, “The constant efficiency amplifier,” NAB Broadcast Engr. Conf. Proc ., 1977, pp. |
Fourth, pulse waveforms may be less susceptible to some forms of jamming. ch20.indd 22 12/20/07 1:15:38 PMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2008 The McGraw-Hill Companies. All rights reserved. |
fuzes.andmissileguidance. These,aswellasotherapplications. havenotbeenwidely employed because oftheconcomitant limitations thatoccurwithoperation atmillimeter waves. |
Therefore. the improvement factor is (4.25) Similarly. for a double canceler. |
ATED AT FREQUENCIES FROM 5(& TO MILLIMETER WAVELENGTHS AND HAVE FOUND USE IN SUCH DIVERSE APPLICATIONS AS AIRPORT SURVEILLANCE RADARS WHERE THE AVERAGE POWERS MIGHT BE MORE THAN ONE KILOWATT IN AIRBORNE MILITARY AIRCRAFT WHERE THE AVERAGE POWER MIGHT BE OF THE ORDER OF K7 OR MORE AND IN LONG RANGE DETECTION OF INTERCONTINENTAL BALLISTIC MISSILES WHERE THE AVERAGE POWER PER TUBE CAN BE GREATER THAN K7 &IGURE DEPICTS THE PRINCIPAL PARTS OF A THREE |
TO |
Trunk, G.rV.: Comparison of Two Scanning Radar Detectors: The Moving Window and the Feed back Integrator, IEEE Trans., vol. AES-7, pp. 395-398, March, 1971. |
0HOENIX * 0 #AMPBELL h"ACK |
The diodes attached to the ends or the particular line selected are operated with forward bias to present a low impedance. The remaining diodes attached to the unwanted lines are operated with hack-hias to present a high impedance. The switched lines can be any standard RF transmission line. |
SURFACE ! |
,/" - $EFINITIONS 4HE INSTANTANEOUS BANDWIDTH OF A COMPONENT IS THE FREQUENCY BAND OVER WHICH THE COMPONENT CAN SIMULTANEOUSLY PROCESS TWO OR MORE SIGNALS TO WITHIN A SPECIFIED ACCURACY 7HEN THE TERM INSTANTANEOUS BANDWIDTH IS USED AS A RADAR RECEIVER PARAMETER IT REFERS TO THE RESULTING BANDWIDTH SET BY THE COMBINATION OF 2& )& VIDEO AND DIGITAL FILTERING THAT OCCURS WITHIN THE RECEIVER 7HEN THE RADAR RECEIVER EMPLOYS STRETCH PROCESSING DEFINED LATER IN THIS SEC |
On one side you have some indication of the transmitter pulse; then, a distance along the trace, you have the blip indi- cating reception of an echo. The distance between these two objects on the tube is proportional to the actual dis- tance in space between them; but as a map it is too elementary to be of any other use than in indicating range, for we cannot tell which direction is being taken by the object giving a reflection. Of course, we could fit either our transmitter or our receiver with a direc- tional aerial, and by rotation we should be able to get some idea of azimuth, just as one does in ordinary radio DF-ing. |
R. K.: Ioriosplieric Scintillation. Proc. |
OUT SPECTRAL ENERGY ! #%! SUCH AS MANUFACTURED BY , |
TIME |
CARRIED A PULSE |
Beforethedevelopment oftheklystronamplifier, theonlyhigh-power transmitter avail ableatmicrowave frequencies for\radarapplication wasthemagnetron oscillator. Inan oscillator thephaseoftheRFbearsnorelationship frompulsetopulse.Forthisreasonthe reference signalcannotbegenerated byacontinuously runningoscillator. However, acoher entreference signalmaybereadilyobtained withthepower oscill~tor byreadjusting thephase ofthecohoatthebeginning ofeachsweepaccording tothephaseofthetransmitted pulse.The phaseofthecohoislockedtothephaseofthetransmitted pulseeachtimea pulseisgenerated. |
More complete descriptions will be fourid it1 the Rtrtiur Ilar~dhook. ' For the most part, this chapter discusses tlie tubes used in radar transmitters and not tlie transmitters tllemselves. A transmitter is far more than the tube alone. |
Remote Sens. Lett. 2017 ,14, 1323–1327. |
QUENCY MODULATION ,&- WAVEFORM PULSE COMPRESSION IS DISCUSSED 7AVEFORM SIGNAL ANALYSIS TECHNIQUES MATCHED FILTER PROPERTIES AND THE WAVEFORM AUTOCOR |
BAND -ULTIFUNCTIONAL 2ADAR !RCHITECTURE !N EXAMPLE -&!2 BLOCK DIAGRAM IS SHOWN IN &IGURE 4HE MODERN INTEGRATED AVIONIC SUITE CONCEPT BLURS THE BOUNDARIES BETWEEN TRADITIONAL RADAR FUNCTIONS AND OTHER SENSORS COUNTERMEASURES WEAPONS AND COMMUNICATIONS SEE &IGURES AND LATER IN THE CHAPTER 4HERE IS A MICROWAVE AND 2& SUITE AN ELECTRO |
TheRFcircuitry that generates thesumanddifference signalsinamonopulse radarhasbeensteadilyimproved, and canberealized withoutexcessive physical bulk.Apopular formofantenna formonopulse is theCassegrain. Withthe1l10nopulse trackeritispossible toobtainameasure oftheangularerrorintwo coordinates onthehasisofasinglepulse.1\minimum offourpulsesareusuallynecessary with theconical-scan radar.However, acontinuous-tracking radarseldommakesameasurement onasinglepulse.(Phased-array radarsandsomesurveillance radars,however, mightuscthe monopulse principle toextractananglemeasurement onthebasisofasinglepulse.)In practice. thetworadarsutilizeessentially thesamenumberofpulsestoobtainanerrorsignal iftheservotracking bandwidths andpulserepetition frequencies arethesame.Themonopulse radarfirstmakesitsanglemeasurement andthenintegrates anumberofpulsestoobtain therequired signal-to-noise ratioandtosmooth theerror.Theconical-scan radar,onthe otherhand,integrates anumberofpulsesfirstandthenextracts theanglemeasurement. |
Arapidchangeofcourseislesslikelyforcivilianaircraft: hence.theslower rotation rateof5rpmfortheARSR-3. Thepul~ewidthof2liScorresponds toarangeresolution ofabout300m.(Inpractice, theresoluticfn issaidtobeabout500m.46)Iflimitations onpeakpowerrequireaco'nsidcrably longerpulsewidthinordertoachieve thenecessary energywithinthepulse,someformof pulsecompression couldbeused.(TheARSR-J doesnothavepulsecompression, however.) FM(chirp)isacommon choiceofpulse-compression waveform. The12.8m(42ft)wideby6.9m(22.6ft)highantenna reflector produces al.25°azimuth heamwidth andashapedelevation beamextending beyond40°soastoprovide coverage toan altitude of18.6km(61ft).Theuppercornersoftheantenna aperture haveasquarerather thanrounded outline.Thiscausestheunderside oftheelevation beamtohaveasharpdrop-ofT whichminimizes theground-reflected energythatcausesalobedelevation patternanda degradation oftherain-rejection capability ofcircular polarization. |
Forcomplete knowledge oftheeffectofpolarization, thepolarization matrixmustbe determined. IfHstandsforlinearhorizontal polarization, 'vforlinearvertical, andifthefirst letterofatwo-letter grouping denotes thetransmitted polarization andthesecondlctter denotes thepolarization ofthereceived signal,thenthepolarization matrixrequires knowl edgeoftheamplitudes andphaseofthefollowing components: HH,VV,HVandVH.HV andVHaresometimes calledthecrosspolarization components. IngeneralHV=VHsothat onlyoneneedbedetermined. |
FERENCE SPIKES AND WORKS EXTREMELY WELL WHEN THE NOISE HAS A NON |
EARTH AND MAY BE GENERALIZED TO CURVED |
Ridenour, L. N.: "Radar System Engirieering," MIT Radiation Laboratory Series, voi. I, sec. |
R.. F. L. |
34!4% 42!.3-)44%23 ££°x WILL NOT hFAILv IN LESS THAN THREE MONTHS HOWEVER THE COST OF REPLACEMENT MODULES AND LABOR WOULD BE VERY UNATTRACTIVE BECAUSE NEARLY OF THE TRANSMITTER WOULD HAVE TO BE REPLACED EVERY YEAR (IGHER -4"&S ARE THUS ESSENTIAL TO ENSURE THAT THE TRANSMITTER IS NOT ONLY AVAILABLE BUT ALSO AFFORDABLE &ORTUNATELY SOLID |
2ECORD /CTOBER PP n ' 7 %WELL AND 3 0 :EHNER h"ISTATIC SEA CLUTTER RETURN NEAR GRAZING INCIDENCE v IN )%% )NT #ONF 2ADAR 0UBLICATION .O ,ONDON /CTOBER PP n ' 7 %WELL h4ECHNIQUES OF RADAR REFLECTIVITY MEASUREMENT v #HAPTER IN "ISTATIC 2ADAR #ROSS |
If the surface has a large radius of curvature so that all the radiating elements point to substantially the same direction, then the characteristics are similar to those of a planar array even though the exact 3D position of the element has to be taken into account to calculate the required phase. A small radius of curvature is found with cylindrical (or spherical) arrays used for 360° coverage. Elements are switched to avoid sec- tions of the antenna where they point away from the desired beam direction. |
58–61. 20. Ken Craig and Mireille Levy, http://www.signalscience.com. |
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