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(E-plane metal-plate lens.) (7.20)250INTRODUCTION TORADAR SYSTEMS Whentheparticles aremetaIlic spheresofradiusaandspacingsbetween centers, the dielectric constant oftheartificial dielectric isapproximately (= 1+41r~l3 5 assuming nointeraction between thespheres.47 Anartificial dielectric mayalsobeconstructed byusingasoliddielectric material witha controlled patternofvoids.ThisisaformofBabinet inverseofthemoreusualartificial dielectric composed ofparticles imbedded inalow-dielectric-constant material.4!lThevoids maybeeitherspheresorcylinders, butthelatterareeasiertomachine. Lensesmadefromartificial dielectrics aregenerally oflessweightthanthosefromsolid dielectrics. Forthisreason,artificial dielectrics areoftenpreferred whenthesizeoftheantenna is large,as,forexample, atthelowerradarfrequencies.

9.7 SOURCES OF ERROR There are many sources of error in radar-tracking performance. Fortunately, most are insignificant except for very high-precision tracking-radar applications such as range instrumentation, where the angle precision required may be of the order of 0.05 mrad (mrad, or milliradian, is one thousandth of a radial, or the angle subtended by 1-m cross-range at 1000-m range). Many sources of error can be avoided or reduced by radar design or modification of the tracking geometry.

The collapsing loss is the additional signal required to maintain the same PD and Pfa when unwanted noise samples along with the desired signal-plus-noise samples are integrated. The number of signal sam - ples integrated is N, the number of extraneous noise samples integrated is M, and the collapsing ratio r = (N + M)/N. ● Most automatic detectors are required not only to detect targets but also to make angu - lar estimates of the azimuth position of the target.

The calibration of the radar does, of course, depend on stable system characteristics and antenna parameters that are invariant with the spacing of the front surface and the antenna. Although on first consideration, frequency domain radars should offer a superior sensitivity to time-domain radars, because of their lower IF receiver bandwidth and hence thermal noise, both the type of receiver and the range sidelobes of the radiated spectrum may result in an equivalent or worse sensitivity in terms of range resolution as discussed above. Pseudo-random-coded Radar.

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vol. AES-8. pp.

K(ZTO K(ZWITHRESPECT TOTHE)&CENTERFREQUENCY-(:TOTALPASSBAND ATTHE

The parameter x might represent a voltage, and (x2).,. the mean, or average. value of the voltage squared.

The main source of noise is termed thermal noise and is due to agitation of electr ons caused by heat. The noise can arise from  received atmospheric or cosmic noise  receiver noise - generated internally in the radar receiver. The overall receiver sensitivity is directly related to the noise figure of the radar receiver.

The usual method isillustrated inFig. 13.40. The principal T#mingpulse J.1 Modulator Rectangular Ir–-----l Inter.wavepulse generator Pulse.

The output of each stage is multiplied by weight ai9 which is either +1 or — 1 in ac- cordance with the reference sequence. The summation circuit provides the out- put correlation function or compressed pulse. Figure 10.136 shows an implementation where the reference may be changed for each transmitted pulse.

An array of antenna elements collects the radiated energy and passes it through the phase shifters which provide a correction for the spherical wavefront, as well as a linear phast: shift across the aperture to steer the beam in angle. Another set of elements on the opposite side of the structure radiate the beam into space. The primary pattern of the feeti illuminating the space-fed array provides a natural amplitude taper.

POINTFEEDISUSUALLYSMALLTOPRODUCEABROADPATTERNANDMUSTBECOMPACTTOAVOIDBLOCKAGEOFTHEANTENNAAPERTURE)NSOMECASES THESMALLOPTIMUMSIZEREQUIREDISBELOWWAVEGUIDECUTOFF ANDDIELECTRICLOADINGOFTHEHORNAPERTURESBECOMESNEC

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10.6, an alert, trained operator viewing a properly designed cathode-ray tube display is a close approximation to the theoretical postdetection integrator. The efficiency of postdetection integration relative to ideal predetection integration has been computed by Marcum10 when all pulses are or equal amplitude. The integration efficiency may be defined as follows: (2.31) where n = number or pulses integrated (S/N)i = value of signal-to-noise ratio of a single pulse required to produce given probability of detection (for n = 1) (S/ N),, = value of signal-to-noise ratio per pulse required to produce same probability or detection when n pulses are integrated The improvement in the signal-to-noise ratio when n pulses are integrated postdetection is nE1(n) and is the integration-improvement factor.

BEAMCLUTTER4HERESULTINTHESPECTRALDOMAINISSPURIOUSMODULATIONSIDEBANDS2ANDOMMULTIPLICATIVENOISEBROADENSTHESPECTRUMOFTHECAR

L. Fante and J. A.

FOLDEDCLUTTER)NPARTICULAR THECLASSOF&-

The If represents the performance of the adaptive array: it accounts for the target signal integration and the interference cancellation. Practical applications of the equation above are, for instance, in Chapter 5 of Farina.34 Crucial for the understanding of the adapted array pattern is the concept of eigenvalue-eigenvector decomposition of the interference covariance matrix M: see again Chapter 5 of Farina34 and Testa and Vannicola.99 An important technique that mitigates the deleterious effects of the noise eigenvectors, thus continuing to maintain a prescribed level of low sidelobes in the adapted array pattern is the so-called diagonal loading.100,101 Adaptive arrays came about after the successful application of SLC, the applica - tion of Eq. 24.6, and of more general and powerful adaptive array concepts (e.g., GSLC: generalized SLC34).

ZMAR, MAR, Typhon, Hapdar, ADAR, MERA, RASSR, and others. Although much effort and funds have been expended, except for limited-scan arrays there has been no large serial production of such radars comparable to the serial production of radars with mechan­ ically rotating reflector antennas. 8.12 ADVANTAGES AND LIMITATIONS The array antenna has several unique characteristics that make it a candidate for considera­ tion in radar application.

37, March, 1959. 22. Knop, C.

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)) PPn !PRIL *2"ARNUMAND%%3IMPSON h/VER

44. M. I.

The surface-reflected signal may be thought of as originating from the image of the target mirrored by the earth's surface. Thus, the effect on tracking is similar to the two-target model used to describe glint, as discussed previously. The surface-reflected signal is sometimes called a multipath signal.

Note that the first blind speed of the composite response is increased several times over what it would be for a radar operating on only a single pulse repetition frequency. Zero response occurs only when the blind speeds of each prf coincide. In the example of Fig.



The intersec - tion of these ellipses, or constant range-sum contours , locate the target. It is similar to multilateration because only range measurements are used to locate the target. * A multistatic radar can also use triangulation for target location by taking simul - taneous target DOA measurements from multiple receive sites at known locations.

HIGHPRECISIONTRACKINGRADARMEASUREDUNDERIDEAL#OMPONENT "IAS .OISE 2ADAR

The extensive use of digital signal processing of radar data has resulted in a demand for converters with both state-of-the-art sampling rates and dynamic range. Analog to digital converters transform continuous time analog signals into discrete time digital signals. The process includes both sampling in the time domain, convert - ing from continuous time to discrete time signals and quantization, converting from continuous analog voltages to discrete fixed-length digital words.

RANGEREGION WHERETHEIMAGEAPPEARSWITHINTHEHALF

3.3.1 Waveform generator type 26 The waveform generator acted as the master clock for the radar, providing the timing waveforms for the scanner, the PPI and height tube displays, and the modulator. Thebasic timing reference was a free-running multivibrator with a repetition interval of 1500μs ± 10%, giving a nominal pulse repetition frequency (PRF) of 660 c/s. 3.3.2 Transmitter –receiver (T 2R unit) TR.

^KiW1 + mK2W2 + • • • + mKKWK = WqK which can be expressed in matrix notation as MW = Wq (16.24) This set of equations can be solved for the steady-state set of weights Wl to WK, which can be expressed in matrix notation as the familiar equation W= M~lWq (16.25) These weights have been shown17'18 to be the optimum set which maximizes the signal-to-interference ratio. Because of the smoothing required to keep the weights from jittering,18 the weights adapt to their steady-state values in a time determined by the clutter power and the allowable steady-state variation in the weights. Other algorithms19 can speed up the adaptation rate, but a more com- plex mechanization is required.

The jamming signals in the channels may be regarded as samples of a stochastic process having zero mean value and a certain time autocorrelation function. For linear prediction problems, the set of samples V is completely described by its Af-dimensional covariance ma- trix M = E(V*V7), where E(.) denotes the statistical expectation, the asterisk * indicates the complex conjugate, and Vris the transpose vector of V. The statis- tical relationship between VM and V is mathematically represented by the N- .

HF OVER-THE-HORIZON RADAR 20.296x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 20 20.8 CLUTTER: ECHOES FROM THE ENVIRONMENT Earth Surface Clutter. The geometry of skywave illumination ensures that tar - get echoes will be immersed in returns from the Earth’s surface, that is, clutter. In order to detect the targets, the properties of this clutter need to be understood so that the choice of frequency, waveform, and signal processing are compatible with the need to separate target echoes from clutter, and also so that the required dynamic range of the radar can be correctly specified.

Resolution, 20 ft (6 m). (Courtesy of En- vironmental Research Institute of Michigan.) storage must be read out for performing the azimuth compression and the pulse compression. Motion Compensation.

38. Tang Dazhang, S. G.

Proportional navigation is based on the fact that if two objects are closing on each other, they will collide if the LOS does not rotate in inertial space, as illus- trated in Fig. 19.4. Any rotation of the LOS (i.e., an LOS rate) is indicative of a deviation from the collision course which must be corrected by a missile maneu- ver.

     
   &)'52%4YPICAL'02SYSTEM#OURTESY532ADAR &)'52%4YPICALDISPLAYFROM'02 . '2/5.$0%.%42!4).'2!$!2 Ó£°Î DIELECTRICVARIATION NOTNECESSARILYINVOLVINGCONDUCTIVITY WOULDALSOPRODUCEREFLEC

J. R. Guerci, Space-Time Adaptive Processing for Radar , Norwood, MA: Artech House, 2003, pp.

AES-4, pp. 4 10 - 4 16, May, 1968. 37.

'RUMMAN3PACE4ECHNOLOGIES!STRO!EROSPACEGROUP HASBEENSUCCESSFULLYLAUNCHEDANDDEPLOYEDANDISCURRENTLYINUSEONSEVERALCOMMUNICATIONSATELLITES  !TOTALOFFIVEREFLECTORSOFAPERTUREDIAMETERSMETERS METERS ANDMETERSHAVEBEENFLOWN3TUDIESHAVEADDRESSEDTHEPOTENTIALUSAGEOF THISREFLECTORTECHNOL

pp. 180-199. February, 1977.

ENERGYDISTRIBUTIONOFANGLESCINTILLATIONMEASUREDONTHENOSE ASPECTOFASMALLTWO

SPREADECHOESWITHTHEPOTENTIALTOOBSCURETARGETS 3CATTERINGFROMTHEAURORALREGIONHASBEENSTUDIEDEXTENSIVELYUSINGTHE3UPER$!2. (&RADARNETWORKINITIATEDBY'REENWALD ANDANAURORALECHO

Knight (eds.), vol. 2, London: Peter Peregrinus, Ltd., 1983. 19.

Hovanessian, S. A.: Medium PRF Performance Analysis, IEEE Trans., vol. AES-18, pp.

The TPS-63 produces a much sharper slope at the horizon than a shaped reflector of equal height. The array feed enables superposi - tion of beams close to the aperture normal, thereby enabling very high taper efficiency (near full aperture gain). FIGURE 12.17 Paraboloidal reflector aperture shapes or rims: ( a) round outline/rim, ( b) oblong, (c) offset feed, ( d) mitered corner, ( e) square corner, and ( f ) stepped corner FIGURE 12.18 AN/TPS-63 parabolic-cylinder antenna ( Courtesy Northrop Grumman Corporation ) ch12.indd 18 12/17/07 2:31:23 PMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2008 The McGraw-Hill Companies.

!SWITHSURVEILLANCERADARS SIDELOBENOISEJAMMINGANDDECEPTION CANBEFURTHERATTENUATEDBYTHEUSEOF3,#INCONJUNCTIONWITH3," ASDESCRIBEDIN3ECTION 4HEUSEOFHIGHERTRANSMISSIONFREQUENCIESFORTRACKINGRADARSGENERALLYMAKETHEM LESSSUSCEPTIBLETONOISEJAMMINGTHANSURVEILLANCERADARS)N ADDITION TACTICALTRACK

YPLANEOF $X $Y K)NPRACTICE THE ACTIVEARRAYELEMENTSARETURNEDONONEATATIMEINCOORDINATIONWITHTHEPROBEPOSI

The height control on the switch unit was adjusted until this blip disappeared into the height return and the aircraft height was read from the dial of the control on the switch unit. A range ring was also available. This appeared as a bright ring on the PPI or another blip (to the right) on the height tube.

For present purposes it will be assumed that the aperture extends in one dimension only. This might represent the distribution across a line source or the distribution in one plane of a rectangular aperture. If the constant .

PEAKVALUEOF AP P4HEVALUEOFTHEPEAKPHASE

(23.19) is not especially representative of shower rainfall. Dennis30 has done considerable work in examining rainfall determinations in shower-type activity. His observations show that the reflectivity factor Z(mm6/m3) of an element of a vertical slice taken through a spherical shower cell is well represented by a regression line of the form Z = Cl(ro - r)c2 (23.20) In Eq.

CLUSIONTHAT34!0WILLIMPROVEPERFORMANCE 34!0SABILITYTOINTEGRATECLUTTERCANCELLATIONTEMPORAL ANDSPATIALINTERFERENCE CANCELLATIONCANBEQUITEIMPORTANTTOMANYRADARSYSTEMSWHETHERTHEYTYPICALLYHAVETODEALWITHINTENTIONALJAMMINGINTERFERENCEORUNINTENTIONALORCASUAL ELECTROMAGNETICINTERFERENCE%-) 34!0GETSAWAYFROMCASCADEDSOLUTIONSSUCHASANALOGSIDELOBECANCELLERSFOLLOWEDBYDIGITAL$0#!ANDOR-4)FILTERSˆTHATDONOTGENERALLYCREATEANOPTIMUMINTERFERENCECANCELLATIONSOLUTION /PTIMAL!DAPTIVE7EIGHTS-C'UFFIN  4HEOPTIMALLINEARESTIMATEISDETER

This was men- tioned in Sec. 8.4. The other is a receive-only ntethod that uses a receiving array with rnixers and local oscill:~tors (Lor;), arrarigecl so as to provide N separate receiving beams fixed in space (Fig.

Extended clutter tends to be noise like and will not pulse-compress, which keeps down inter - ference displayed to operators.29 The disadvantages of pulse compression are related to the long duration of the coded pulse, which gives more time for the ECM equip - ment to process the pulse. In many cases, pulse compression can provide the means for easy radar jamming for the enemy ECM operator. Pulse compression is also vulnerable to cover-pulse jamming, in which the ECM pulse is returned to the radar with a high JNR such that the normal target return is covered by the jamming pulse.

This chapter will provide a high-level outline of some of the major digital pro - cessing techniques for radar systems that have become practical since the Second Edition of this Handbook was published, as well as some design tradeoffs that need to be considered.Chapter 25 ch25.indd 1 12/20/07 1:39:46 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. Source: RADAR HANDBOOK.

IRE.) . 238 INTRODUCTION TO RADAR SYSTEMS radiated toward the edge of the reflector should usually be about one-tenth the maximum intensity. The aperture distribution at the edges will be even less than one-tenth the maximum because of the longer path from the feed to the edge of the reflector than from the feed to the center of the dish.

/ ÊÊ ,"1 Ê,

In the bistatic case, the isodops are skewed away from the look angle, depending upon the geometry and platform motion, and the clutter is called nonstationary . Bistatic isodops are developed analytically for two dimensions and a flat earth by setting fTR = constant in Eq. 23.12 and solving for qR (or q T, if appropriate).

Sometimes both conditions cannot· he met simultaneously and a compromise is necessary. The upper cutoff frequency is selected to pass the highest doppler frequency expected. The indicator might be a pair of earphones or a frequency meter.

Harriger, “Medium PRF for the AN/APG-66 radar,” in IEEE Proceedings , vol. 73, no. 2, p.

Farina, E. Giaccari, F. Madia, R.

ccEEEEE WTIIS   WHERE D`ISTHEREALPARTOFTHEDIELECTRICPERMITTIVITY D` REALPARTOFTHEDIELECTRICPERMITTIVITY Dp IMAGINARYPARTOFTHEDIELECTRICPERMITTIVITY Dc HIGHFREQUENCYLIMITINGVALUEOFTHEPERMITTIVITY.

600 EXAMPLES OFRADAR SYSTEM DESIGN [SEC. 15.8 adequate forasimple tracking orcontrol problem, but complex problems clearly called forhigher scan rates even attheexpense ofcoverage. Foreseeing awide range ofapplications forthenew radar equipment, itsdesigners provided anantenna drive bymeans ofwhich the scanning rate could beadjusted over therange from 1to6rpm.

162THEGATHERING ANDPRESENTATION OFRADAR DATA [S’EC. 62 Informing the displays, radar echo signals may beused either to displace (deflection-modulate) the electron beam, asinthe ordinary oscilloscope, ortointensify (intensity-modulate) it,asisdone intelevision. Deflection modulation affords precise information about the strength and character ofthe signals delivered bythe receiver, but leaves only one dimension ofthetube face free torepresent ageometrical quantity.

S. Hartwick, and M. T.

This version scans over arange ofelevation angle from ~to7#. The beam- tilting isachieved byaltering the relative phasing ofthe groups of dipoles; each group isfed from amechanical phase shifter mounted in thecenter ofthemast. The banks ofdipoles can betilted mechanically.

IEEE T rans. Aerosp. Electron.

Against a single clutter source, an implementa - tion is required that permits the MTI clutter notch to be shifted as a function of range. An example of such an adaptive MTI implementation is shown in Figure 2.85. The phase-error circuit compares the clutter return from one sweep to the next.

Attain- ment of very long life, in the region of 10,000 h or more, requires judicious se- lection of power ratings, conservative cathode-current density, and conscientious counseling of the marriage between tube and transmitter. RF Tube Power Capabilities. The peak power capabilities of RF tubes have progressed sufficiently far that the limitation has become breakdown in practical waveguide systems, even with 20 lb/in2 of SF6 in the waveguide.

205-213. 37. Hovanessian, S.

      

,.0.672 0.5 ;. DETECTION OF RADAR SIGNALS IN NOISE 375 the values of Br which maximize the signal-to-noise ratio (SNR) for various combinations of filters and pulse shapes. It can be seen that the loss in SNR incurred by use of these non- matched filters is small.

Therefore, the problem of distinguishing di fferent scatterers at di fferent azimuth angles can be transformed into the problem of distinguishing di fferent scatterers at di fferent Doppler frequencies. Suppose a scatterer is located at the azimuth angle θ0, and the azimuth angle θ0is also the center of the antenna beam. The boundaries of the antenna beam can be denoted as θ0–Δθ/2 andθ0+Δθ/2, which correspond to the Doppler frequencies fdhand fdl, respectively.

Methodology The SBAS-InSAR method is used to process Radarsat-2 WUF SLC images in the ENVI SARScape module to obtain land subsidence information in Wuhan city [ 31]. The SBAS-InSAR method is an advanced InSAR technique that could improve the monitoring accuracy [ 51]. The SBAS-InSAR method relies on an appropriate combination of differential interferograms within the thresholds of temporal and spatial baselines, so the geometric decorrelation is minimal [ 26,31,36,52].

SIDELOBEnVOLTAGERATIOAPPROACHESO -

N. Freedman, “Bistatic radar system configuration and evaluation,” Raytheon Company, Independ. Dev.

2, pp. 111–115, April 1962. (Reprinted in Kovaly.15) 15.

Time Domain. Most commercially available GPR systems use short pulses or impulses such as the Ricker wavelet, as shown previously in Figure 21.5. The high- speed sequential sampling approach used to acquire RF waveforms produces a low ch21.indd 21 12/17/07 2:51:29 PMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2008 The McGraw-Hill Companies.

Although this is a rather simple example of a "complex" target, it is complicated enough to indicate the type of behavior to be expected with practical radar targets. The radar cross sections of actual targets are far more complicated in structure than the . i I simple two-scatterer target.

Errors in the array spacings produce phase errors which generate amplitude ripples and delay nonlinearities. Since many paths exist at a given frequency, these delay and am- plitude errors tend to average out. Because of the averaging of the phase errors, the best delay linearity is achieved when the maximum number of grating lines is used.

Applebaum, “Cassegrain systems,” IRE Trans ., vol. AP-9, pp. 119–120, January 1961.

E. Filer and J. Hartt, “COBRA DANE wideband pulse compression system,” IEEE EASCON ’76, 1976, pp.

3.8. In channel A the signal is processed as in the simple CW radar of Fig. 3.2.

Any one of a number of transmitting-tube types might be used as the power amplifier. These iticlirde thc triode, tetrode, klystron, traveling-wave tube, and the crossed-field amplifier. Pulse Duplexer amplifier '; "c TI ompljfier ,~~ld I I detector Mix Figure4.5 Block diagram of MTI radar with power-amplifier transmitter.

PRESSTHESEOSCILLATIONSCOMPLETELY(OWEVER SINCETHISPARTICULAROSCILLATIONDEPENDSONELECTRONVELOCITY WHICHINTURNDEPENDSONBEAMVOLTAGE THEPROBLEMISAVOIDEDBYTHEUSEOFMOD

In contrast to the lens, which is placed between the radar and the test object, the radar and the test object remain on the same side of the reflector, as shown in Figure 14.23. The reflector is typically an offset paraboloid, meaning the paraboloidal surface does not include the vertex of the generating parabola. This permits the feed that excites the reflector to be placed out of the beam reflected toward the target.

13.3. The changes in clutter statistics must be accounted for in the detector design, else the large signal-to-clutter ratios required of a conventional threshold detector might negate any benefit of the shortened pulse. As mentioned previously, a radar with a very short pulse (or narrow beamwidth) might prove to be worse than one with a longer pulse (or a wider beamwidth) because of the change in clutter statistics.

All rights reserved. Any use is subject to the Terms of Use as given at the website. Multifunctional Radar Systems for Fighter Aircraft. MULTIFUNCTIONAL RADAR SYSTEMS FOR FIGHTER AIRCRAFT 5.236x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 5 identification methods such as JTIDS, IFF, and RF tagging that can be unique.

Trunk, G. V.: Comparison of th~ Collapsing Losses in Linear and Square-law Detectors, Proc. IEEE, vol.

These are discussed in the paragraphs which follow. TABLE 17.3 Discrete Clutter Model Radar cross section, m2 106 105 104Density, per mi2 0.01 0.1 1 . Guard Channel.

POLARCORRELATIONRATIOQHV \ %H %V \ % H%H ˜ % V%V ˜  ,INEARDEPOLARIZATIONRATIO,$2 :CXV  :COH  :HAND:VARETHEMEASUREDREFLECTIVITIESOFTHEHORIZONTALANDVERTICALCO

Note: In MTI, a single value of CA will be obtained, while in doppler radar the value will generally vary over the different target doppler filters. In MTI, CA will be equal to MTI improvement factor if the targets are assumed uniformly distributed in velocity. See also: MTI improvement factor.

TYPE TRACKINGRADARSCAUSEDBYHIGH

Output ratings vary from 14orless toover 1200 volts, and from 30ma to5amp, with any combination oftwo, three, orfour atatime. Weights vary from 5lb,foratotal output of20watts, to26lb,foranoutput of400 watts. Efficiencies range from 40percent to60percent.

 /THER.,&-WAVEFORMSTHATHAVEBEENUTILIZEDINRADARINCLUDETHENONSYM

Each receiver site consists of an interferometer antenna to obtain an angle measurement in the plane of the fan beam. There are three sets of transmitter-receiver stations to provide fence coverage of the southern United States. The CW radar, when used for short or moderate ranges, is characterized by simpler equipment than a pulse radar.