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Measurement uncertainty result from: - Imprecise measurement equipment - Quantization errors - Noise - Signal distortion. For an example a sine wave o scillation with be analyzed. 5.1 Measurement Accuracy and Sine Wave Oscill ations As shown in Figure 5.1, when one observes a sine wave, with superimposed noise n(t), so differs the observed amplitude from the true amplitude around € ΔU=n(t) € u(t)=U0sin(ωt+ϕ0)+n(t) (5.1) Figure 5.1 Sine wave oscillation with superimposed noise. |
R., and W. W. Shrader: MTI Performance Caused by Limiting, EASCON '68 Record, Supplement to IEEE Trans, vol. |
Thelargedoppler shiftsatmillimeter wavelengths, however, cansometimes result intheechosignalbeingoutsidethereceiverbandwidth, whichcomplicates thereceiverdesign. Also,thelargedoppler frequencies atmillimeter wavelerigths causetheblindspeedsofMTI radarstoappearatlowervelocities thanatmicrowaves, anundesirable property. Thus,afrustrating paradox ofthemillimeter-wavelength regionisthatsomeofits claimed goodpointsarealsoitsweaknesses. |
Giannini. R. J., J. |
32. Li, T.: A Study of Spherical Reflectors as Wide-angle Scanning Antennas, IRE Tru11s., vol. AP-7, pp. |
It performs doppler . 140 INTRODUCTION TO RADAR SYSTEMS filtering on a single spectral line of the pulse spectrum. (A radar which employs multiple pulse repetition frequencies to avoid blind speeds is usually classed as an MTI if its average prf would cause blind speeds. |
ANCE ETC OVER THE ENEMY IN A GIVEN SITUATION %-#/. PERMITS ESSENTIAL OPERATIONS WHILE MINIMIZING THE DISCLOSURE OF LOCATION IDENTIFICATION FORCE LEVEL OR OPERATIONAL INTENTIONS TO ENEMY INTELLIGENCE RECEPTORS )T INCLUDES THE AUT HORIZATION TO RADIATE THE CONTROL OF RADIATION PARAMETERS SUCH AS AMPLITUDE FREQUENCY PHASE DIRECTION AND TIME THE PROHIBITION OF RADIATION AND THE SCHEDULING OF SUCH ACTIONS FOR ALL UNITS AND EQUIPMENT OF A COMPLEX 4HE ON |
DEFINED ANGULAR SPACING &OR A GRID WITH SUPPORTS AND ASSOCIATED ERRORS A DISTANCE S APART THE GRATING LOBE APPEARS AT P ARCSINSK 4HE GRATING LOBE AMPLITUDE DEPENDS ON THE DEPTH OF THE DISTORTION &IGURE AND IS TYPICALLY 'RATING,OBE ¤ ¦¥³ µ´PE L WHERE D IS THE DEPTH OF THE CUSP &EED $ISPLACEMENT 4HE PERMISSIBLE TOTAL ERROR IN THE OVERALL FEED |
Radar Conf. Rec ., 1975 pp. 396–401. |
inany given case. 3However, wemay aswell lump together theeffect ofthedetector, thecathode-ray- tube modulation characteristics, the screen characteristics, and those of the eye, and admit that nobrief discussion ofthese factors ispossible. Inmost cases one has torely onexperience; that istosay, one has to design bymaking relatively short extrapolations from previous practice, orbymaking preliminary tests under conditions approximating those selected. |
Naval Research Laboratory for over 30 years. Before that he was involved in advances in radar while at the MIT Lincoln Laboratory, the Institute for Defense Analyses, and the Research Division of Electronic Communications, Inc. He is the author of the popular McGraw-Hill textbook Introduction to Radar Systems , now in its third edition, the editor of Radar Applications , as well as being a former editor of the Proceedings of the IEEE . |
The Gotcha public release dataset is used to verify our aspect entropy extraction methods at the pixel and target levels. The result shows that the aspect entropy of pixels and targets can be extracted from CSAR data. Aspect entropy of pixels can be used to discriminate between isotropic and anisotropic scattering. |
(4.25) and (4.26) cannot be extended over too great a frequency range since account is not taken of any variation in radar cross section of the individual scatterers as a function of frequency. The leaves and branches of trees, for example, might have considerably different reflecting proper- ties at K, band (A = 0.86 cm), where the dimensions are comparable with the wavelength, from those at VHF (A = 1.35 m), where the wavelength is long compared with the dimensions. The general expression for improvement factor for an N-pulse canceler with N, = N - 1 delay lines is6' Antenna scanning rn~dulation.~~.~~-~~ As the antenna scans by a target, it observes the target for a finite time equal to to = n$ fp = 88/8,, where n, = number of hits received, fp = pulse repetition frequency, 0, = antenna beamwidth and 0, = antenna scanning rate. |
DWELL STAGGER OPERATION IS CONSIDERABLY MORE DIFFICULT 4YPICALLY PULSE |
I mπ λ (19.17) where the ai are droplet radii, r is the density of water, and Im is the imaginary part. Values of K1 for ice and water clouds are given for various wavelengths and tempera - tures by Gunn and East44 in Table 19.1. Several important facts are demonstrated by Table 19.1. |
The scattering from these two·· resonant" wave component:,; is similar to that from a diffraction grating. The term Bragg st:.ttter is sometimes used to describe this form of scattering, by analogy to the Bragg-scatte.- mode for the X-ray diffraction by crystals. The velocity of a water wave (a gravity wave in deep water) is v = (g..l,.,/2n)112, where g is the acceleration of gravity. |
The range frequency fr may be extracted by measuring the average beat frequency; that is, , f[h(up) + fb(down)] = f,. If fb(up) and fb(down) are measured separately, for example, by switching a frequency counter every half modulation cycle, one-half the difference between the frequencies will yield the doppler frequency. This assumes.fr > fd . |
Retrieval of biophysical parameters of agricultural crops using polarimetric SAR interferometry. IEEE T rans. Geosci. |
KM IMAGE FRAME )TS STRIP MAPPING MODE IS BASELINED AT |
There are two basic approaches for taking advantage of the nonlinearity of these metal contacts. In one approach a single frequency is transmitted and a harmonic of the transmitted frequency is received. The nature of the nonlinearity of typical contacts is such that the third harmonic is usually the greatest. |
197 207. hlarcll. 1973. |
Anderson, “Limits to the extraction of information from multi-hop skywave radar signals,” Proc. Int. Radar Conf ., Adelaide, September 2003, pp. |
4, pp. 368-376, 1987. CHAPTER 24 HF OVER-THE-HORIZON RADAR* J. |
Twersky, V.: On Scattering and Rdlection of Electromagnetic Waves hy Rough Surface~. IR I:." Trans., vol. AP-5, pp. |
LENGTH SEQUENCES HAVE A STRUCTURE SIMI |
Apositive potential isappliedtothiscutoffelectrode atthetermination ofthepulse tocollect,orqllellclr,theremaining electron current. Thepositive potential needbeappliedfor onlyashorttime;hencetheenergyrequirements arelow.Thismethodofmodulation inwhich thed-canode-cathode voltage isappliedcontinuously andthetubeisturnedonbythestartof theRf7drive-pulse andturnedofTattileendoftilepulsebytheaidofacut-offelectrode to relllovetileclcctrons,hasheencalledd-c0l'erati01l. Itisapplicable toforward-wave Cf7As,but itisnotusuallyuscdwithbackward-wave CFAssincethevariation ofoutputpowerwitII frcqucncy ataconstant d-cvoltagethatischaracteristic ofbackward-wave tubeswouldlimit thebandwidth tobutafewpercent. |
499-505, May, 1971. (Also available in ref. 1.) 9. |
All rights reserved. Any use is subject to the Terms of Use as given at the website. Solid-State Transmitters. 11.6 RADAR HANDBOOK 6x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 11 the drain and source contacts, allowing the current flowing between the drain and source to be modulated accordingly; hence, FETs are referred to as voltage controlled devices . |
ING SOMETIMES CALLED COMPRESSION BECAUSE IT IS SIMILAR TO PHASE MATCHED PULSE COM |
V.: GaAs FET Development-Low Noise and High Power, Microwave J., vol. 21, pp. 39-44, February, 1978. |
Inagroup ofbuildings, alarge proportion ofthe flat surfaces will bevertical walls, while many others aresmooth pave- ments orflat roofs. There aremany opportunities forcombinations of three flat surfaces atright angles toform corner reflectors (Sec. 3.5), which arehighly retredirect ivetargets. |
The compensating delay must beinserted after thepoint atwhich thetrigger pulse hasleftthat channel but before cancellation. The first method istoadd the required delay either atcarrier or video frequency. Unfortunately, noelectrical delay lines areavailable which arecapable ofreproducing amicrosecond pulse with lessthan 1per cent distortion. |
(OLLAND P 0 )A 5FIMTSEV h!PPROXIMATE COMPUTATION OF THE DIFFRACTION OF PLANE ELECTROMAGNETIC WAVES AT CERTAIN METAL BOUNDARIES 0ART ) $IFFRACTION PATTERNS AT A WEDGE AND A RIBBON v :H 4EKHN &IZ 5332 VOL NO PP n 0 )A 5FIMTSEV h!PPROXIMATE COMPUTATION OF THE DIFFRACTION OF PLANE ELECTROMAGNETIC WAVES AT CERTAIN METAL BOUNDARIES 0ART )) 4HE DIFFRACTION BY A DISK AND BY A FINITE CYLINDER v :H 4EKHN &IZ 5332 VOL NO PP n 0 )A 5FIMTSEV h-ETHOD OF EDGE WAVES IN THE PHYSICAL THEORY OF DIFFRACTION v 5 3 !IR &ORCE 3YSTEMS #OMMAND &OREIGN 4ECHNOLOGY $IVISION $OC &4$ |
SEL THEN 2#3 MIGHT BE M AND A M RANGE RESOLUTION MIGHT BE USED FOR SEARCH &)'52% 4&4! TERRAIN MERGING #OURTESY 3CI4ECH 0UBLISHING . -5,4)&5.#4)/.!, 2!$!2 3934%-3 &/2 &)'(4%2 !)2#2!&4 x°Î£ AND ACQUISITION )F THE TARGET IS A PERISCOPE OR PERSON IN A LIFE RAFT THEN M RESOLU |
PULSE STAGGERING AND INTERNAL |
5.9 Block diagram of a generic transceiver module for phased array radar. 1. Low-cost circuitry: Component assembly is eliminated since complex cir- cuit configurations using both active and passive components are batch- processed on the same substrate. |
SPHERE 4HESE FACTORS ARE MENTIONED TO EMPHASIZE THAT THEY CAN BE HIGHLY IMPORTANT IN THE DESIGN AND APPLICATION OF A RADAR 2ADAR 4RANSMITTERS 4HE RADAR TRANSMITTER MUST NOT ONLY BE ABLE TO GENERATE THE PEAK AND AVERAGE POWERS REQUIRED TO DETECT THE DESIRED TARGETS AT THE MAXIMUM RANGE BUT ALSO HAS TO GENERATE A SIGNAL WITH THE PROPER WAVEFORM AND THE STABILITY NEEDED FOR THE PARTICULAR APPLICATION 4RANSMITTERS MAY BE OSCILLATORS OR AMPLIFIERS BUT THE LATTER USUALLY OFFER MORE ADVANTAGES 4HERE HAVE BEEN MANY TYPES OF RADAR POWER SOURCES USED IN RADAR #HAPTER 4HE MAGNETRON POWER OSCILLATOR WAS AT ONE TIME VERY POPULAR BUT IT IS SELDOM USED EXCEPT FOR CIVIL MARINE RADAR #HAPTER "ECAUSE OF THE MAGNETRONS RELATIVELY LOW AVERAGE POWER ONE OR TWO KILOWATTS AND POOR STABILITY OTHER POWER SOURCES ARE USUALLY MORE APPROPRIATE FOR APPLICATIONS REQUIRING LONG |
Although the typical radar transmits a simple pulse-modulated waveform, there are a number of other suitable modulations that might be used. The pulse carrier might be frequency- or phase-modulated to permit the echo signals to be compressed in time after reception. This achieves the benefits of high range-resolution without the need to resort to a short pulse. |
J. Daniels, Ground Penetrating Radar , 2nd Ed. IEE Radar Sonar Navigation and Avionics Series, London: IEE Books, July 2004. |
(ALL PP n * & 2AMSEY h,AMBDA FUNCTIONS DESCRIBE ANTENNADIFFRACTION PATTERNS v -ICROWAVES P *UNE 7 - 9ARNALL h4WENTY |
Patent, 4, 006, 478, February 1, 1977, filed August 15, 1958. 156. R. |
2!$!2 $)')4!, 3)'.!, 02/#%33).' Óx° SAMPLE RATE 4HE SINE AND COSINE SIGNALS FROM THE .#/ ARE THEN DIGITALLY MULTIPLIED BY THE DIGITIZED )& SIGNAL )N THIS PARTICULAR EXAMPLE THE REL ATIONSHIP BETWEEN THE ,/ FREQUENCY AND THE SAMPLING RATE WILL MAKE THE REQUIRED .#/ AND THE MULTIPLIERS BOTH RATHER TRIVIAL BECAUSE EACH REQUIRED .#/ OUTPUT VALUE IS ZERO OR o AND THAT SPECIAL CASE WILL BE ADDRESSED SHORTLY &OR NOW THIS ARCHITECTURE SUPPOSES THAT NO SUCH SPECIAL SITUATION EXISTS AND THAT A GENERAL .#/MULTIPLIER STRUCTURE IS NEEDED 4HE DESIGN OF &)'52% $IGITAL DOWNCONVERSION IN THE FREQUENCY DOMAIN 0 |
ADDED EFFICIENCY IS A CIRCUIT DESIGNERS TERM AND IS DEFINED BY 0!% 0/ |
Ruze showed that the radiation pattern can be expressed as (7.31) where G0(0. q,) is the no-error radiation pattern whose axial value (at O = 0, </J = 0) is 110(n:IJ/A)2• {) is the antenna diameter, Pa is the aperture efficiency, C is the correlation interval of the error, and II equals sin 0. The mean square phase error Pis assumed to be gaussian. |
A procedure is proposed aimed at both improving the range migration algorithm and imaging data from different view angles in a unified coordinate system. This provides images with the same resolution, not deformed and scaled, that can be fused quickly and accurately. The work in [ 2] also deals with the optimal processing of SAR data acquired with wide aperture, as for circular SAR systems, and in particular tackles the problem of aspect-dependent backscattering. |
It produces a negative voltage at A’s anode, which is fed to B’s grid and produces a positive voltage at B’s anode, which adds itself to the original r-volt change. There will be two very different results, depending on whether the application of 1 volt positive will make B’s anode go more or less than 1 volt positive. Suppose that the effect of 1 volt positive is that A’s anode goes 4 volt negative, making B’s grid, of course, also go 4 volt negative. |
The minimum operational display area is defined as a diameter: 180 mm for ships less than 500 gt; 250 mm for ships from 500 to 10,000 gt; and 320 mm for ships above 10,000 gt. The minimum recommended display areas for small craft radar are given in Table 22.2. The color of radar targets and background is not mandated. |
CIALLY IN URBAN AND SUBURBAN AREAS CAN SIGNIFICANTLY DEGRADE 0"2 PERFORMANCE 4HIS SECTION SUMMARIZES THE PROBLEMS AND REMEDIES ENCOUNTERED BY A 0"2 EXPLOITING THESE BROADCAST TRANSMITTERS. |
K. L. S. |
Amein, A.S.; Soraghan, J.J. Fractional Chirp Scaling Algorithm: Mathematical Model. IEEE T rans. |
10.17 atapoint ofhigh efficiency and low frequency stability corresponding topoint A.This can beaccomplished byintro- ducing atransformer which sets upa2-to-1 VSWR and making itsdis- tance from themagnetron such that thephase ofthis VSWR corresponds topoint A. Bymoving this transformer along theline ineither direction one-quarter wavelength, operation corresponding topoint Bcan be obtained. Incomparing the eflect ofdifferent loads corresponding to various points onthe Rieke diagram, itshould berealized that these points represent transformations that reduce the size ofacircle ofcon- stant VSWR asitscenter ismoved away from thecenter ofthediagram. |
11.6. The amplitude distribution across the aperture as a (11.35)EXTRACTION OFINFORMATION ANDWAVEFORM DESIGN409 spectrum andawidewaveform yieldsanarrowspectrum andboththetimewaveform andthe frequency spectrum cannotbemadearbitrarily smallsimultaneously. TherelationofEq.(11.34)isuseful,however, asanindication oftheaccuracy withwhich timedelayandfrequency maybemeasured simultaneously. |
2.10 RADAR HANDBOOK 6x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 2 shifted precisely 360° or multiples thereof between pulses, which results in no change in the phase-detector output. The blind speeds can be calculated V kfkBr= ⋅⋅= ±λ 20 1 2, , ,... (2.1) where VB is the blind speed, in meters per second; l is the transmitted wavelength, in meters; and fr is the PRF, in hertz. |
BAND AND '(Z 4HE )45 RECOMMENDS THAT FOR PULSE LENGTHS OF §S OR LONGER THE FREQUENCY ACCURACY OF THE RESPONDING SIGNAL SHOULD BE WITHIN o -(Z AND FOR PULSES OF LESS THAN §S THE FREQUENCY SHOULD BE WITHIN o -(Z 3WEPT FREQUENCY RACONS ARE EFFECTIVELY OBSOLESCENT BUT ARE STILL PERMITTED 4HESE WORK BY HAVING AN INTERNAL 2& SOURCE THAT IS SLEWING IN FREQUENCY ACROSS THE ENTIRE RADAR BAND WITH A SAW |
71.Siebert, W.M.:SomeApplications ofDetection TheorytoRadar,IRENatl.Conv.Record,vol.6, pt.4,pp.5-14,1958. 72.Hansen, V.G.,andA.J.Zottl:TheDetection Performance oftheSiebertandDicke-Fix CFARRadar Detectors, IEEETrans.,vol.AES-7,pp.706-709, July,1971. 73.Carpentier, M.H.:..Radars: NewConcepts," Gordon andBreach,NewYork,1968,sec.4.6. |
For < small, sin 5 may be replaced by (ha + h,)/R so that'^ = 2ha(ha + h,)/R s 211. h,/R. The latter expression Figure 12.1 Propagation over a plane reflecting surface. |
W. B. Adams, “Phased array radar performance with wideband signals,” AES Conv. |
Onewayto establish some absolute basis isto give the ~bserved value ofthe ratio ofminimum detectable signal power to average noise power, forone particular system. This isdone inTable 22, inwhich aredisplayed therelevant constants ofthesystem selected. TABLE 22.-(2HARACTERISTICS OFASAMPLE SYSTEM Type ofindication. |
Stretch Pulse Compression.57–60,62 Stretch pulse compression is a technique for performing LFM pulse compression of wideband waveforms using a signal processor with bandwidth that is much smaller than the waveform bandwidth, without loss of signal-to-noise ratio or range resolution. Stretch pulse compression is used for a single target or for multiple targets that are located within a relatively small range window centered at a selected range. Figure 8.28 shows a block diagram of a stretch pulse compression system. |
Figure 4.15. Schematic block diagram of ASV Mk. VIB [ 6].Airborne Maritime Surveillance Radar, Volume 1 4-15. |
All rights reserved. Any use is subject to the Terms of Use as given at the website. Space-Based Remote Sensing Radars. SPACE-BASED REMOTE SENSING RADARS 18.296x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 18 representing the data, and several alternative methods for data analysis. |
H. Ackroyd: Uniform Complex Codes with Low Autocorrelation Sidelobes, IEEE Trans., vol. IT-20, pp. |
In the adaptive MTI implementation described above, the number of zeros allo - cated to each of the two cancelers was fixed, based on an a priori assessment of the clutter suppression requirement. The only variation possible would be to completely bypass one (or both) of the MTI cancelers if no land clutter or weather or chaff returns are received on a given radial. A more capable system can be implemented if the num - ber of zeros can be allocated dynamically to either clutter source as a function of range. |
POLARIZED ON RECEIVE &IGURE 4HIS ARCHITECTURE REQUIRES LESS MASS AND OFFERS GREATER EFFICIENCY THAN ALTERNATIVES WHILE CAPTURING ALL OF THE POTENTIAL INFORMA |
PRODUCES A MUCH SHARPER SLOPE AT THE HORIZON THAN A SHAPED REFLECTOR OF EQUAL HEIGHT 4HE ARRAY FEED ENABLES SUPERPOSI |
The majority of radars that operate ovnr the sea usually employ horizontal polarization. Air-surveillance radars with horizontal polarization achieve greater range than with vertical polarization because of the higher reflection coefficient of horizontal polarization (Sec. 12.2). |
Villasenor, “Decorrelation in interferometric radar echoes,” IEEE Trans Geoscience and Remote Sensing , vol. 30, pp. 950–959, 1992. |
Conv. Rec., (supplement to IEEE Trans. vol. |
Target detection is similar to that of monostatic radar: target illuminated by the transmitter and target echoes detected and processed by the receiver. Tar- get location is similar to but more complicated than that of a monostatic radar: total signal propagation time, orthogonal angle measurements by the receiver, and some estimate of the transmitter location are required to solve the transmitter-target-receiver triangle, called the bistatic triangle. Continuous-wave (CW) waveforms can often be used by a bistatic radar because site separation, possibly augmented by sidelobe cancellation, provides sufficient spatial isolation of the direct-path transmit signal. |
LIKE TECHNOLOGY AND WAS ORIGINALLY BASED ON THE MILITARY )&& )DENTIFICATION &RIEND OR &OE SYSTEM /THER !PPLICATIONS ! HIGHLY SIGNIFICANT APPLICATION OF RADAR THAT PROVIDED INFORMATION NOT AVAILABLE BY ANY OTHER METHOD WAS THE EXPLORATION OF THE SURFACE OF THE PLANET 6ENUS BY AN IMAGING RADAR THAT COULD SEE UNDER THE EVER |
A range compressed signal RCS1 with time delay 0.5 μs. Figure 6. Three range compressed signals RCS1, RCS2, RCS3 and their sum RCS. |
BASED 3!2 PRECEDENTS . |
PP n $ECEMBER $ ( #OOPER h"INARY QUANTIZATION OF SIGNAL AMPLITUDES EFFECT FOR RADAR ANGULAR ACCURACY v )%%% 4RANS VOL !NE |
It might consist of an air-core inductance with taps along its length to which are attached n ,f capacitance to ground. A transformer is used to match the impedance of the delay line to that of the load. A perfect match is not always possible because of the nonlinear impedance characteristic of microwave tubes. |
END NOISE TO MIXER NOISE D" D" D" 3ACRIFICE IN MIXER DYNAMIC RANGE D" D" D" $EGRADATION OF SYSTEM NOISE TEMPERATURE DUE TO MIXER NOISE D" D" D" 4HE SAME CONSIDERATIONS APPLY TO THE SETTING OF THE NOISE LEVEL AT THE INPUT TO THE !$ CONVERTERS 4RADITIONALLY THE NOISE CONTRIBUTION OF THE !$ CONVERTER WAS CON |
For very high powers, the rising-sun system has considerable promise. Unlike strapped systems, the rising-sun system permits the anode tobemade with acircumference and alength which arenot small compared toawavelength without producing mode instabilities. Thus even athigh frequencies large cathodes and large emissions arepossible. |
But when the air is crowded with civilian traffic the same difficulties may be experienced, and the advantage of coded beacons is obvious. Beacons can provide an indication of bearing with a remarkable accuracy, but for air-travel we must know ; . 162 HOW RADAR WORKS more than bearing; we must have some radar device to indicate height. |
However. the smaller effective antenna aperture associated with the broad receiving beam results in less echo signal. This must be compensated by greater transmitter power. |
-ULTISENSOR 4RACKING !PPLICATIONS AND !DVANCES VOL ))) 9 "AR |
OE-9, pp. 291–308, 1984. 12. |
BAND OF FREQUENCIES )T CAN RADIATE A HIGHER MEAN POWER LEVEL PER SPECTRAL LINE THAN THE TIME |
TION AND TRANSPARENT TO ORTHOGONAL POLARIZATION )T IS ORIENTED TO BE TRANSPARENT TO THE 8 |
M. Bracalente, D. H. |
Today the possibilities are simple to list after many disappointments due to disillusionment: Optimization of the shape and style (wideband) Covering with Radar absorbing material (wideband) Layering of the outer -surface materials (narrowband) These three possibilities will be further discussed in the coming sections. 11.8.1 Optimization of Shape and Style It was shown by the representation of backscattering characteristics of simple bodies that, based upon the projection surface , the sphere had the smallest scattering cross -section, with: € σKugel=r2π (11.24) For bodies with differing curvature in both planes the following applies, where r1 and r2 are the two radii of curvature: € σ=r1r2π (11.25) From this it follows that the radius of curvature is to be minimized. In these cases, in which not all aspect angles are expected, one can also consider working with mirrored reflection at diagonal angles of incidence, as Figure 11.18 shows. |
Cook: Effects or Limiting on the Detectability of Partially Time Coincident Pulse Compression Signals, IEEE Trans., vol. MIL-9, pp. 17-24, January, 1965. |
The term Bragg scatter is often used to describe the mechanism for the small-perturbation model. The idea comes from the concept illustrated in Fig. 12.66. |
"ASED -IDCOURSE $EFENSE SYSTEM INCLUDING SEARCH ACQUISITION TRACKING DISCRIMINATION AND KILL ASSESSMENT 309 |
The parametric amplifierl0.I8 has the lowest noise figure of those devices described here, especially at the higher microwave frequencies. Ifowever, it is generally more complex and expensive compared to the other fro11 t-ends. 'The transistor a~rlplifier can be applied over most of the entire range of frequencies of inter- est to radar.10-'9.20 The silicon bipolar-transistor has been used at the lower radar frequencies (bclow I, batld) atld tile galiu~tl arserlide field-eKect transistor (GaAs FET) is preferred at the I I I I I I Ill I I 5000 10,000 30,000 Frequency - MHz Figure 9.4 Noise figures of typical microwave receiver front-ends as a function of frequency- 6 0 50 m = 4 0.- I ?! 1T' w 30.- 0 z 2 0 10- - Image-recovery mlxer wtlh r parametric amplifier RECEIVERS, DISPLAYS, ANDDUPLEXERS 351 Thenoisefigureofareceiver withnoisefigureFr,preceded byRFlossesequaltoLRFis F2-1F0=FI+------=LRF+(Fr-l)LRF=FrLRFG1 whereF1=4F,G1=I/LRF,andF2=Fr· 9.4LOW-NOISE FRONT-ENDS(9.15) Earlymicrowave superheterodyne receivers didnotuseanRFamplifier asthefirststage,or front-end. |
Kimpel, D. S. Zrnic, S. |
The purpose of the rear receiver is to provide a coherent reference for detec- tion of the front (target) signal. The rear signal, after conversion to IF, closes the automatic frequency control (AFC) loop around the microwave local oscillator (LO) and acts as the reference for the IF coherent detector. The target signal, received in the front antenna, is heterodyned to IF and amplified in a relatively wideband amplifier (typically 1 MHz or wider). |
For example, a typical waveform in this class has N contiguous pulses of width τ whose spectra of width 1/ t are placed side by side in frequency to eliminate gaps in the composite spectrum. Since the waveform band - width is now N/t , the nominal compressed-pulse width is t /N. These relationships are summarized in Table 8.7. |
Astropical (butnotequatorial) climates arenotedfortheirfineweather, itisnotsurprising to findthemostintenseducting occurring 'insuchregions.32Intemperate climates ducting is morecommon insummer thaninwinter.Itdoesnotoccurwhentheatmosphere iswellmixed, acondition generally accompanying'poor weather. Whenitiscold,rough,stormy, rainy,or cloudy,theloweratmosphere isweillS'tirred~upandpropagation islikelytobenormal. Both roughterrainandhighwindstendto'increase atmospheric mixi,ng,consequently reducing the occurrence ofducting. |
One limiting factor of superresolution techniques is that they often require the received signals to obey accurate models of the array manifold. This can be violated due to propagation effects (e.g., spatial spreading and nonstationarity) as well as instru - mental effects (e.g., channel mismatch). These factors also affect the performance of adaptive antennas for jammer cancellation, but model mismatches can degrade the performance of superresolution techniques more severely. |
These lower level functional suites are connected by standardized bus - ses, which may be fiber optic or wired. The programmable devices are controlled by software operating environments invoking programs. The architecture objective is to have standard interfaces, few unique assemblies, and single-level maintenance. |
46. J. L. |
IN GROUND |
The middle threshold divides the “tentative” region into a tentatively correlated region and a tentatively uncorrelated region. The rationale in setting the threshold is to set the two associated error probabilities equal for a particular separation. The threshold TM was found by using simulation techniques and is also shown in Figure 7.42. |
13ofthisseries. z‘~he changes ofintensitv caused bystatistical fluctuations ofthemmber Of raindrops within apulse packet aresmall compared with these changes.. 84 PROPERTIES OF RADAR TARGETS [SEC. |
COUNTERMEASURES %##- TO ENSURE EFFECTIVE USE OF THE %- SPECTRUM DESPITE AN ENEMYS USE OF %7 ACTIONS 4HIS CHAPTER IS DEVOTED TO THE DESCRIPTION OF THE %##- TECHNIQUES AND DESIGN PRIN |
The output power capability of GaAs FETs increases almost linearly with increases in the total gate width, while the power gain decreases slowly with increasing total gate width. The maximum practical total gate width that can be accommodated on a single chip is limited by the following factors: 1. Yield of the device: A typical dc processing yield may be 0.995 per 100 |xm of gate periphery. |