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It is simply a function computed from the reciprocal of a true adapted antenna pattern. Superresolution and adaptive antennas for jammer can - cellation are intimately related. Roughly speaking, the difference is that one produces a pattern with the nulls down (adaptive antenna for jammer cancellation) and the other with the nulls up, i.e., peaks (superresolution of jammers).

The prime difference between optical and microwave refraction is that water vapor has a negligible effect on the former; consequently the second term of Eq. (12.9) may be neglected at optical frequencies. Since the barometric pressure p and the water-vapor content e decrease rapidly with height, while the temperature T decreases slowly with height, the index of refraction normally decreases with increasing altitude.

MALLYBENIGNCONDITIONSONTHEBRIDGEOFALARGEMODERNSHIP THEDISPLAYANDRADARPROCESSORCANBESUBJECTTOHIGHLEVELSOFSHOCKANDVIBRATIONANDMUSTMEETHIGHVARIATIONSINTEMPERATURE

A P-4. pp. 60, 609, October, 1956.

ALARMPROBABILITYACCORDINGTO 0F 

The induction motor rating should beabout 50per cent larger than that required todrive the alternator. Itis desirable tohave the alternator output the same asthe ship’s power so that theradar system can beoperated directly from the ship’s supply in case ofbreakdown ormaintenance shutdown ofthemotor-alternator set. The motor may bedirect-coupled orbelt-connected tothealternator; usually direct coupling ispreferred because ofitssimplicity.

Arancibia, “A sidelobe blanking system design and demonstration,” Microwave J ., vol. 21, pp. 69–73, March 1978; reprinted in Ref.

.2#3 . '2/5.$0%.%42!4).'2!$!2 Ó£°Ó£ THATTHEPEAKSIGNALOUTPUTTOMEANNOISERATIOISGREATERTHANCANBEACHIEVEDWITHANY OTHERLINEARFILTER4HISISNOT ALWAYSTHEBESTFILTERTOUSE FORTIME

(24), thegreatest possible subclutter visibility is26db. There isthen noneed tomake theindividual subclutter risibilities forscanning and wind greater than 30db. For thecase ofscanning, that means, from Eq.

Raven, and P. Waterman, Airborne Radar , Boston: Boston Technical Publishers, 1965, pp. 203–207.

The echo from the ground directly beneath the aircraft is called the altiwde return. The altitude return is not shifted in frequency since the relative velocity between radar and ground is essentially zero. Clutter to either side of the perpendicu­ lar will have a relative-velocity component and hence some doppler frequency shift; con­ sequently the clutter spectrum from the altitude return will be of finite width.

Thechoiceofpolarization alsoinfluences thea'mount ofseaorlandabsorption. Vertical polarization isabsorbed morethanhorizontal. Thetotalantenna temperature canbefoundbyintegrating thetemperature" seen"bythe antenna, weighted bytheantenna gainovertheentiresphere.60 '7:~'f78(0,c/J)G(O,c/J)dO.

Practical Detectors. Many different detectors (often called integrators ) are used to accumulate the radar returns as the radar sweeps by a target. A few of the most common detectors7 are shown in Figure 7.3.

10.22 RADAR HANDBOOK 6x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 10 rectangular pulse, a large bandwidth would likely cause interference to other radars and other electromagnetic systems. For this reason, government frequency allocation agencies usually require that the frequency spectrum from a radar not contain large energy at other frequencies. This is becoming more important as the occupancy of the electromagnetic spectrum is increasingly crowded with transmitters.

This is especially useful in an air-traffic-control display in which such information as target ide~ltity a~id altitude is desired to be displayed. The positions of targets on a predeterniiried number of previous scans might be shown on a synthetic display, or a line might be generated tb indicate the direction of the target's trajectory and the target's speed. (The length of the line can be made proportional to target speed.) The use of a computer to generate the grapllicq arid coritrol the CRT display offers flexibility in the choice of such things as range scales, olfcenter displ;ty, blow-up of selected areas, physical map outlines, grid displays, airport runways, stored clutter map, raw video, outlines of areas of weather blanked by the operator, tlispiay of stored flight plans, arid time-compressed display of several successive radar scans.

S. Pearson, “On the problems of the most efficient tests of statistical hypoth - eses,” Philos. Trans.

The entire unit rotates at a 6 rpm rate. It houses a broadside array of Yagi-type endfire elements. It' 1.

SIGHTPROPAGATIONISTOREDUCETHEANGLEOFTHELOWESTLOBE BRINGINGITCLOSERTOTHESURFACE    & $ ! #
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Lines ofconstant height arehorizontal and equally spaced. Arrangements aresometimes made tomove therange origin offthetube face toallow expansion ofaregion ofinterest. Iftheheight-finding antenna isrequired toscan over anappreciable range ofazimuth angles, theRHI isusu- ally blanked except during arelatively10,OOO narrow azimuth sector, inorder toimprove the ratio ofsignal tonoise and toavoid ZPconfusion between targets atdifferent ; azimuths.

This was said to apply to a good operator viewing a PPI under good conditions. Its degree of applicability, however, is not clear. It is not iinusual to find no accoutlt of the operator loss being taken in the radar equation.

705-706, December, 1957. 50. Payne-Scott, R.: The Visibility of Small Echoes on Radar PPI Displays, Proc.

2 INTRODUCTION TO RADAR SYSTEMS The name radar reflects the emphasis placed by the early experimenters on a device to detect the presence of a target and measure its range. Radar is a contraction of the words radio detection and ranging. It was first developed as a detection device to warn of the approach of hostile aircraft and for directing antiaircraft weapons.

MADESLINGORHARNESSTOSUPPORTTHETARGET4HEFIRSTUSESASINGLEOVERHEADSUPPORTPOINTANDGUYLINESTOAFLOOR

Tlle evaporation duct that lies just above the surface of the sea is a result of tlie water vapor. or liumidity, evaporated from the sea. The air in contact with the sea is saturated 14tIi water vapor, wit11 a saturation vapor pressure appropriate to the temperature of tl~e sea si~rface.'~ The air several meters above the sea is not usually saturated so there will be a gradual decrease in water vapor pressure from the surface value to the ambient value well above tlie surface.

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Platform is a generic term referring to the vehicle where the radar and antenna are installed. Typical radar platforms include pedestal (fixed site), ground vehicles, ships, airplanes, UA Vs, and spacecraft/satellites. The following short section is devoted to platform impacts and some key associated design drivers.

Some of the prediction methods have not been well documented although widely distributed; also, users frequently “improve” upon a model and prediction method to suit their specific needs. As an example, the model RADAR C29 is the basic building block of Thomason et al. in NRL Report 832122; however, they added a D region, a collision-frequency distribution, an Earth’s magnetic field, a topside elec - tron distribution, an auroral electron-density modification,34 and other features that make the model more generally useful.

Conf ., September 14–16, 1964, pp. 259–263. 11.

The term pseudo-monostatic will be used to characterize bistatic geometries that approximate monostatic operation. 23.2 COORDINATE SYSTEMS A two-dimensional north-referenced coordinate system21 is used throughout this chapter. Figure 23.1 shows the coordinate system and parameters defining bistatic radar opera - tion in the ( x, y) plane, also called the bistatic plane .22 The bistatic triangle lies in the bistatic plane.

The sine pulse, inaddition toitstracking role, triggers aflip-flop controlling the cosine-pulse switch, and thecosine pulse similarly triggers aflip-flop con- trolling themodulator pulse switch. The modulator pulse ispassed onto theindicators and, inaddition, triggers aflip-flop which closes theswitch ahead ofthedecoder while video signals arebeing received, and opens it shortly before thenext basic pulse. Afew words should besaid about theprocess of“locking in” initially orafter tracking has been lost through failure ofsignals orsevere inter- ference.

It was shown in Chap. 2 that the dividing line between these two regions depended upon the probability of a false alarm, which in turn is related to the average time between false alarms. There are two types of errors that might be made in the decision process.

Electron ., vol. 16, pp. 170–185, October 1984.

Maffett, F. Smith, R.C. Heimiller, and A.

24,Sec. 6.2. The latter effect makes the detection ofadesired target echo within therain clutter even more difficult, forthevery persistence ofthetarget echo onsuccessive pulses helps greatly todistinguish itfrom noise (Sec.

In fact, the sharp falloff of the nonducting data in Figure 15.18 might be further evidence of the threshold shadowing mentioned earlier. However, the common idea of shadowing derives from the geometrical optics concept of a sharp transition between light and darkness. By considering the implications of diffraction at the wave peaks, it is possible to determine the domain of radar frequen - cies and wind speeds over which the concepts of geometrical optics may be applied.

Further, it can be shown that the average SCR improvement calculated for a single filter is equal to the MTI improvement factor as defined in Sec. 15.4. The basis for obtaining the optimum MTI filter is again the covariance matrix of the clutter returns as given by Eq.

(Ajler Sa~nders,~ IRE Trans.) CWANDFREQUENCY-MODULATED RADAR89 whereJ0,JI,J2,etc=Besselfunctions offirstkindandorder0,I,2,etc.,respectively D=(~I/f~)sin2rrf~Role Ro=distance totargetattimet=0(distance thatwouldhavebeenmeas­ urediftargetwerestationary) c=velocity ofpropagation Id=2l',.f~/c=doppler frequency shift 1',=relative velocity oftargetwithrespecttoradar <Po=phaseshiftapproximately equaltoangular distance 4rrfoRole cPm=phaseshiftapproximately equalto2rrfmRole Thedifference-frequcncy signalofEq.(3.16)consists ofadoppler-frequency component ofamplitude Jo(D)andaseriesofcosinewavesoffrequency 1m'~rm,~rm'etc.Eachofthese harmonics off~ismodulatcd byadoppler-frequency component withamplitude proportional toJn(IJ).Theproduct ofthedoppler-frequency factortimesthenthharmonic factorisequiva­ lenttoasuppressed-carrier double-sidcband modulation (Fig.3.15). Inprinciple, anyoftheJncomponents ofthedifference-frequency signalcanbeextracted inthcFM-CW radar.Consider firstthedoctermJo(D)cos(2rrfdt-4>0)'Thisisacosinewave atthctloppler frequency withanamplitude proportional toJo(D).Figure3.16showsaplotof severaloftheBesselfunctions. Theargument DoftheBesselfunction isproportional torange.

22.11 Maximum time for viewing objects from a space vehicle if the objects are tracked.28 3. Atmospheric propagation problems can be minimized by proper selection of operating frequencies and favorable geometry selection. 4.

The MTI in the lower beams can be optimized for surface clutter and MTI in the upper beams, ~f used at all, can be optimized for rain and chaff. The individual pencil beams have a higher gain than a fan-beam antenna, and can provide a larger number of hits at a higher data rate than can a 3D radar with a single scanning beam in elevation. -) Scanning pencil beam.

Any use is subject to the Terms of Use as given at the website. Electronic Counter-Countermeasures. ELECTRONIC COUNTER-COUNTERMEASURES 24.636x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 24 100. B.

11.6 Measured RCS pattern of a dipole 5.221X long. (Courtesy of University of Michigan Radiation Laboratory.6) Figure 11.7 shows the broadside resonances of a wire dipole as a function of dipole length. The first resonance occurs when the dipole is just under a half wavelength long, and its magnitude is very nearly X2.

III and ASV Mk. VI are shown in figures 4.33 and4.34. Figure 4.33 compares detection ranges for a U class submarine, either beam-on or end-on to the radar.

23-25, 1973, pp. 292-296. 42.

MTI-14, pp. 24 -28, January, 1966. 41.

STAP is a fairly broad topic that has applicability beyond this chapter on airborne MTI radar. The primary motivation for STAP is to improve clutter cancellation perfor - mance and to better integrate a radar’s spatial processing (antenna sidelobe control and sidelobe jamming cancellation) with its temporal clutter cancellation processing. The applicability of STAP to improving clutter cancellation must be assessed spe - cifically in the context of the key performance limiters to airborne MTI radar clut - ter cancellation as described at the start of this chapter.

11.20. This device generates a binary pseudorandom code of zeros and ones oflength 2" I, where n is the number of stages in the shift register. Feedback is provided by taking the output of the shift register and adding it, modulo two, to the output from one of the previous stages of the shift register.

POLARIZEDRETURNSFROM VOLUMESCATTERERSWITHELEMENTSTHATARELARGECOMPAREDWITHA WAVELENGTHARESTRON

A single "snapshot" of a PPI would not likely differentiate the echo of a small target from that of the sea spikes. The individual sea spikes, however, will disappear with time and new spikes will appear at other locations. If it is possible to observe the radar display for a sufficient period of time, the small targets can be recognized since they will remain relatively fixed in amplitude while the sea spikes come and go.

Isolation can also be increased by transmitting on an orthogonal polarization to that received. Providing they are operating with linear gain, there are no adverse effects from radar sidelobe interrogation. However, at close ranges, the signal from the main beam of the radar may saturate within the RTE, effectively enhancing the levels of the RTE received signal through the radar sidelobes.

For a finite array the properties vary with location of the element within the array. In some arrays, dummy elements are placed on the periphery so as to provide the elements near the edge with an environment more like those located in the interior. Although there have been many di!Terent kinds of radiators used in phased arrays, the dipole.

PRODUCTSAREGENERATED WHICHREDUCETHEECHOSMATCHED

Houze, Jr., and J. D. Locatelli: Real-Time Wind Measurement in Extratropical Cyclones by Means of Doppler Radar, /.

and T. F. Bush: Corn Growth as Monitored by Rada1.

2!$!2$)')4!,3)'.!,02/#%33).' Óx°ÓÇ #OMPAREDTO&)2FILTERS ))2FILTERSOFFERSEVERALADVANTAGES)NGENERAL THEYREQUIRE LESSPROCESSINGANDMEMORYTOIMPLEMENTSIMILARFUNCTIONS)TISALSOEASIERTOIMPLE

When tile wind is blowing toward the radar tlie dpproacliing-wavc spectral line IS the larger of the two. When the wind is blowing away from the radar, the receding-wave spectral line is the larger When the wind IS blowing perpendicular to the direction of the radar beam, the two spectral lines are equal. Thus the relative magnitude of the two major components of the doppler spectrum can provide a measure of the direction of the wind.

● The combiner should have RF isolation among ports, such that failed modules do not affect the load impedances or combining efficiency for the remaining functioning modules. ● The combiner should provide a controlled RF impedance to the amplifier modules, such that the amplifier characteristics are not degraded. ● The dissipated power capability of the power combiner terminations should be suf - ficient to accommodate any combination of power amplifier failures.

BASEDMEASUREMENTS4HUS BEINGABLETOMEASURESTRONGPRECIPITATIONECHOESATSHORTRANGEANDALSOWEAKPRECIPITATIONECHOESATLONGRANGEREQUIRESRADARRECEIVERSHAVINGATOTALDYNAMICRANGEOFnD"WHEREASMEASURINGWEAKECHOESINTHEPRESENCEOFSTRONGGROUNDCLUTTERREQUIRESASLARGEANINSTANTA

The calibrations shown in Figure 16.12 are incomplete without knowing the antenna patterns and absolute gains. Since accurate gain measurements are difficult, absolute calibrations may be made by comparing received signals (with proper rela - tive calibration) from the target being measured and from a standard target . Standard targets may be metal spheres, Luneburg-lens reflectors, metal plates, corner reflectors, or active radar calibrators (ARCs—actually repeaters).84,85 Of the passive calibrators, the Luneburg-lens reflector is best because it has a large cross section for its volume and has a very wide pattern so that alignment is not critical.

MAP

COST643SYSTEMSSTILLCOMMONLYUSESUBSYSTEMSINTENDEDFORSHIPBORNEUSE GIVINGGOODCOSTSAVINGSCOMPAREDTOCUSTOM

vi. Adjust the orientation of the PPI so that the upward direction on the tube face is the heading of the aircraft. This is effected by setting the track line onthe Perspex screen to zero, setting the switch on the heading control unit to manual, and turning the setting knob until the course marker lies under the track line.

9.26. Examples ofRadomes.—Types ofradomes vary greatly insize, shape, and method ofconstruction. Attention iscalled toafew repre- sentative radomes.

Patent No. 3,797,017, Mar. 12, 1974.

Atthesametime,moisture isaddedfromthesea toproduce amoisture gradient. Thisformofanomalous propagation overtheseatendstobe moreprominent ontheleeward sideoflandmasses.Ducting occursduringeitherthedayor nightandcanlastforlongperiodsoftime.Itismostlikelytooccur,however, inthelate afternoon andevening whenthewarmafternoon airdriftsoutoverthesea..B Thusthecharacter ofducting' islikelytodifferoverlandandsea.Landmasseschange temperature muchmorequickly than'does thesea.Asaresult,thereismuchmoreofadiurnal variation ofducting overlandthanoversea,whereitislikelytobemorecontinuous and widespread.32 .Superrefracting groundductsmayalsobeproduced bythediverging downdraft undera thunderstorm.3!Therelatively coolairwhichspreadsoutfromthebaseofathunderstorm resultsinatemperature inversion inthelowestfewthousand feet.Themoisture gradient is alsoappropriate fortheformation ofaduct.Ductformation bythunderstorms maynotbeas frequent asotherducting mechanisms, butitisofimportance sinceitmaybeusedasameans ofdetecting thepresence ofastorm.Anoperator carefully watching aradardisplaycanddcct thepresence ofastormbythesuddeninc'rease inthenumberandrangeofgroundtargets.The conditions appropriate tothe'formation Iofathunderstorm ductareshort-lived andhavea timeduration oftheorderof'perhaps 30minto1h. Withtheexception ofthunderstorms, ducting isessentially afine-weather phenomenon.

Thesumsignalhashigher sidelobes because theseparation between thephasecentersoftheseparate antennas islarge.(Thesehighsidelobes aretheresultof gratinglohes.similartothoseproduced inphasedarrays.)Theproblem ofhighsidelobes can hereduced byoverlapping theantenna apertures. Withreflector antennas, thisresultsinaloss ofanglesensitivity andantenna gain. 5.5TARGET-REFLECTION CHARACTERISTICS ANDANGULAR ACCURACyJo.41.Q5 Theangular accuracy oftracking radarwillbeinfluenced bysuchfactorsasthemechanical properties oftheradarantenna andpedestal, themethodbywhichtheangular position ofthe antenna ismeasured, thequalityofthes~osysteQ'l,thestability oftheelectronic circuits, the noiselevelofthereceiver, theantenna beamwidth, atmospheric fluctuations, andthereflection characteristics ofthetarget.Thesefactorscandegrade thetracking accuracy bycausingthe antenna beamtofluctuate inarandom manner aboutthetruetargetpath.Thesenoiselike fluctuations aresometimes calledtracking noise,orjitter.

This delay is quantized by a range gate pull off (RGPO) device. A range gate stealer system linearly delays the quantized signal in order to generate a constant range-rate false target. The joint effect of phase and delay quantization in DRFM can be analyzed as reported in Greco, Gini, and Farina.26 Other artifacts in the deception signals can be introduced by imperfections in the down-up conversion and demodulation/modulation of the signal performed in the DRFM device.

This is known as target classification. The time delay between the transmission of the radar signal and the receipt of an echo is a measure of the distance, or range, to the target. The range measurement is usually the most significant a radar makes.

Any use is subject to the Terms of Use as given at the website. Synthetic Aperture Radar. 17 .36 RADAR HANDBOOK 6x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 17 34. R.

1, pp. 272-293, 1958. 42.

Improved Delay Line Technique Study, RADC Tech. Rept. RADC-TR-65-45, May 1965.

N.: Use of Bistatic Radar Techniques to Improve Resolution in the Ver- tical Plane, IEE Electron. Lett., vol. 4, pp.

The nature of the circuit may also demand that the lagging edge be vertical, to produce an imstantaneous cut-off. Such a wave-form is produced in the transmitter modulator, the pulse of energy is broadcast, and a signal received by the radar receiver. Now there is one impor- tant difference between a radar and a broadcast radio receiver.

into the holes of the hole-and-slot resonators to change the inductance of the resonant circuit. A tuner that consists of a series of rods inserted into each cavity resonator so as to alter the inductance is called a crown-of-thorns tuner, or a sprocket t1111cr. The amount of mechanical motion of the tuning element need not be large (perhaps a fraction of an inch at L band) to tune the frequency over a 5 to 10 percent frequency range.

(&/6%2

M.: A Note on Doppler-Shifted Signals, Proc. IEEE, vol. 54, pp.

It might have a frequency-response characteristic similar to that of Fig. 3.2b. The low-frequency cutoff must he high enough to reject the d-c component caused by stationary targets, but yet it must he low enough to pass the smallest doppler frequency expected.

It is also possible to utilize a common aperture for both transmit and receive, with equal transmit and receive beamwidths. Duplexers would be required as in a microwave phased-array radar. The antenna might also support several simultaneous, independent radar beams; or multiple beams can be generated sequentially (a pulse burst).

For frequencies of 2 MHz to 57 GHz, AREPS uses the APM. For HF sky wave communications, AREPS uses an HF modeling suite,22 consisting of a fully 3D ionosphere ray trace model, an HF field strength model, and an HF noise model. In addition to these EM propagation models, AREPS may optionally use two internationally recognized ionosphere models, the Parameterized Ionospheric Model (PIM)23 and the International Reference Ionosphere (IRI).24 In addition to the propaga - tion models, AREPS contains a system performance radar model, which is discussed in the next section.

The reentering electrons, however, might contain modulation which will be amplified in the next pass through the circuit. To circumvent this the tube of Fig. 6.12 has a drift space to demodulate the electron stream so as to remove this RF feedback.

2OWELL AND 69UDIN h!DVANCEDMODELINGOF THEIONOSPHEREANDUPPERATMOSPHERE v %NVIRONMENTAL2ESEARCH4ECHNOLOGIES2EPORT ! *UNE *+(ILL h%XACTRAYPATHSINAMULTISEGMENTQUASI

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Two-Pole Filter. The two-pole filter in Fig. 8.3c requires the storage of an intermediate calculation in addition to the integrated output and is described mathematically byLIMIT FOR MAX.STANDARD DEVIATION (FRACTION OF BEAMWIDTH) .

3.Duplexer, TR and ATR tubes. 4.Local oscillator. 5.Radar and AFC mixer.

They are often dual-band (3 and 9 GHz). The ITU recommends that for pulse lengths of 0.2 µs or longer, the frequency accuracy of the responding signal should be within ±1.5 MHz, and for pulses of less than 0.2 µs, the frequency should be within ±3.5 MHz. Swept frequency racons are effectively obsolescent but are still permitted.

Radar engineers can learn a great deal from their communications colleagues who realize similar concepts for sof tware- defined radios (SDR). In the future, the processing needs for communications are comparable to remote sensing or even higher. 14.3 SDRS and SD -SAR System Aspects Because the entire functionality of this new type of software -defined Radar sensors can be dow n- loaded, their operat ing modes may be multifunctional, selective, active, pa ssive and corrective.

Thesynthesis techniques whichapplytoarrayantennas usuallyassumeuniformly spaced isotropic elements. Theelement spacingisgenerally takentoheahalfwave-length. Ifthe elemerlts werenotisotropic buthadapatternEe(8),andifthedesiredoverallpatternwere denotedEd(8),thepatterntobefoundbysynthesis usingtechniques derived for.isotropic elements wouldbegivenbyEd(8)/Ee(8).

Finally, for the exponential clutter spectrum model, the optimum improvement fac - tor is shown in Figure 2.29, again as a function of the RMS relative spectrum width, assuming zero mean for the spectrum. FIGURE 2.27 Optimum improvement factor for gaussian spectrum model ch02.indd 31 12/20/07 1:44:32 PMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2008 The McGraw-Hill Companies. All rights reserved.

One of the advantages of a lens over a reflector antenna is the absence of aperture blocking. Considerable equipmen1 can be placed at the focus of the lens without interfering with the resultant antenna pattern. The first monopulse radars used lenses for this purpose, but with time the monopulse RF circuitry was reduced in size and the reflector antenna came to be preferred over the lens.

than with linear.79 An alternative to circular polarization is to transmit any linear polarization and receive on the orthogonal linear polarization.79.!H Spherical raindrops will give no return in the orthogonal channel if no cross-polarization distortion takes place in the radar or the propaga­ tion medium. There is some evidence to indicate that crossed linear polarization may give better rain rejection than conventional circular polarization. I .og-FTC receiver.

Only one power supply voltage is necessary for the collector terminal of the transistor. The Class-C operation is a self-bias, wherein the transistor draws collector current only when the RF voltage swing on the input exceeds the built- in potential of the emitter-base junction. Additional reverse biasing may be intro- duced as a result of the voltage drop induced by current flow across parasitic re- sistance of the base or emitter bias return, and in common-base operation this will result in degraded power gain.

TERREGION HOWEVER BYINTERPRETING 2 OASTHERANGEWHERETHESIGNALISEQUALTO SIDELOBECLUTTERPLUSSYSTEMNOISEn4HE#&!2LOSSMAYALSOBEHIGHEROWING TOTHEINCREASEDVARIABILITYOFTHETHRESHOLDWHENTHECLUTTERVARIESOVERTHETARGETDETECTIONREGION-OREACCURATECALCULATIONSOFDETECTIONPERFORMANCEINTHESIDE

9.12. Inthefinal design oftheantenna mount, thereflectors fortheupper and lower beams are mounted back-to-back, sothat their axes differ by180°. This complicates somewhat the mechanism fortransmission ofazimuth-angle data from theantenna mount totheindicators.

This negates the benefit of the increased signal-to-clutter ratio achieved by high resolution as expressed by Eq. (13.8) for the detection of targets in clutter. (As will be discussed in Sec.

-ODES -ODE 7IDTH7 !CCESS 2ESOLUTION ,OOKS 13!2713!2 3ELECTIVEPOLARIZATION KM KM M 2Gr!Z 2Gr!Z 3TANDARD  n r r   7IDE  n r r   &INE  n r r   3CAN3!27IDE  n r r   3CAN3!2.ARROW  n r r   3INGLEPOLARIZATION ,OWINCIDENCE  n r r   (IGHINCIDENCE  n r r   0OLARIMETRY 3TANDARD1UAD0OL  n r r   &INE1UAD0OL  n r r   3ELECTIVE3INGLE0OL-ULTI

The thresholds of the ind i- vidual CFAR algorithms (CFAR -parameter setting α = 1 and β > 0 because of the LOG - amplifier) cause no false alarms, meaning that the signal ampl itudes in the scenario exceed the CFAR threshold only for targets. Thus, a criterion for the qua lity of the CFAR threshold (i.e., the fit of the threshold to the clutter scenario) is given by summing the threshold crossings. These are defined as q=s(i)−c(i) [ ] ∑ for all i with s(i) > c(i), wher e s is the scenario and c .

FORAIR

One method for · protecting the tube is to direct the arc-discharge currents with a device called an electro11ic crowbar. It places a virtual short circuit across the capacitor bank to transfer the stored energy by means of a switch which is not damaged by the momentary short-circuit conditions. The name .is derived from the analogous action of placing a heavy conductor, like a crowbar, directly across the capacitor bank.

Another important fighter category is weapon support. Missile update is the mea - surement of missile and target position, velocity and acceleration to allow statistically independent measurements for transfer alignment, as well as missile state-of-health. Missile update provides the latest target information and future dynamics prediction by data link.

EFFICIENCYAMPLIFIERHASBEENAGOALFORTRANSMITTERENGINEERSEVERSINCE,EE$E&ORESTAND!MBROSE&LEMINGINVENTEDTHEFIRSTELECTRONICAMPLIFIERSv4HISGOALSEEMSTOHAVEBEENACHIEVEDBYTHE#%!GRID

corresponds to rc = -1-0.443~ and 0- to 11 = -0.443~ The sin 0 - sin 11, term in the expres- sion for 11 car1 be writtetll ' sin 0 - sin Uo = sin (0 - 00) cos Oo - El - cos (0 - i)o)] sin Oo (8.11) 'Pllc second terrn on the right-hand side of Eq. (8.1 1) can be neglected when Oo is small (beam is near broadside), so that sin 0 - sin O0 = sin (0 - 00) cos O0 (8.12) Using the above approximatioi~, the two angles corresponding to the 3-dB points of the arltenrla pattern are 0.4431 hl 0.443A 0, - 0 - sin-" - 0 - NdcosOO NdcosOO - 0.4431 - 0.443A 0- - Oo = sin - ' .- .- --- - - ... - Nri cos O0 Nti cos O0 Til£'EI.ITTRONICAI.LY STEERED PHASED ARRAYANTENNA INRADAR283 Figure8.2Sleering ofanantenna beamwith variable phaseshifters(parallel-fed array).