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Wu: "The Scattering and Diffraction of Waves." Harvard University Press, Cambridge, Mass., 1959. 70. IEEE Standard Letter Designations for Radar-Frequency Bands. |
386-400. 8. Welle, G. |
DOPPLER TARGETS THAT ARE IN THE CLUTTER |
the aperture and fall into the class of phase-comparison monopulse. However, the basic performance of amplitude- and phase-comparison monopulse is essen- tially the same.3 Figure 18.17 shows the antenna and receiver for one angular-coordinate track- ing by phase-comparison monopulse. Any phase shifts occurring in the mixer and IF amplifier stages cause a shift in the boresight of the system. |
ANGLE CLUTTER WIND SPEED ABOUT KT AFTER & " $YER AND . # #URRIE Ú )%%% . £x°ÓÈ 2!$!2 (!.$"//+ THE FACT THAT THE EXCITATION OF THE SURFACE |
20 The characteristics of a CFA are illustrated by the Varian SFD-257, a forward-wave tube used in the final high-power amplifier stage or the transmitter chain in the AN/MPS-36 C-band range-instrumentation tracking radar.18 The SFD-257 operates over the frequency range 5.4 to 5.7 GHz with a peak power of 1 MW, 0.001 duty cycle, and an efficiency of over 50 percent. The tube is d-c operated in that the RF pulse turns the tube on and a control electrode turns it off. In this radar application the pulse widths arc 0.25, 0.5, or 1.0 ,,s, but the tube can deliver a pulse as wide as 5 µs. |
Aircraft at any altitude within this region can be detected, located, and tracked so as to provide a cost-effective over-ocean air-traffic-control capability. Target height is not obtained with this OTIl radar. (Nor is height obtained with tlie usual microwave air-traffic-control radars.) It is possible to utilize modified H F communications equipment as transponders on each aircraft which can relay back to the radar tlie height of the aircraft as determined by the onboard altimeter, as well as tlie identity of the aircraft. |
CENTERED REGION 4HE TERM COOPERATIVE TRANSMITTER IS SOMEWHAT OF A MISNOMER &OR EXAMPLE A COOP |
Ground Penetrating Radar (GPR), discussed in Chapter 21, is an example of what is called an ultrawideband (UWB) radar. Its wide signal bandwidth sometimes cov - ers both the VHF and UHF bands. Such a radar’s signal bandwidth might extend, for instance, from 50 to 500 MHz. |
-/" )N !-4) SYSTEMS HAVING MANY HITS PER SCAN SCANNING IS A SECONDARY LIMITATION FOR AN UNCOMPENSATED DOUBLE CANCELER (OWEVER THE PERFORMANCE OF A $0#! SYSTEM IS SIGNIFICANTLY REDUCED WHEN IT IS SCANNED 4HIS IS DUE TO THE SCANNING MODULATION ON THE DIFFERENCE PATTERN USED FOR PLATFORM |
ANCE OF THE SEA SPIKES IS VERY SIMILAR FOR BOTH MODERATE AND WEAK WIND CONDITIONS ALTHOUGH THE AMPLITUDES DIFFER BY ALMOST D" AND THE VERTICALLY POLARIZED RETURNS APPEAR TO BE SOMEWHAT BROADER WHILE THE HORIZONTALLY POLARIZED RETURNS ARE MORE SPIKY PARTICULARLY FOR SHORT PULSES IN CALM SEAS 4HESE ARE ALL CHARACTERISTICS OF SEA CLUTTER AT LOW GRAZING ANGLES 4HE PROBABILITY DISTRIBUTIONS OF LOW GRAZING ANGLE SEA CLUTTER CHANGE WITH WIND SPEED %XAMPLES MAY BE FOUND IN THE MEASUREMENTS BY 4RIZNA OF L OW |
Range Boxcar gate - generotor No. n .. .. |
72. E. K. |
Any use is subject to the Terms of Use as given at the website. Automatic Detection, Tracking, and Sensor Integration. AUTOMATIC DETECTION, TRACKING, AND SENSOR INTEGRATION 7 .336x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 7 As seen in Figure 7.28, the selection of Q(tk) and thus gtrack allows one to uniquely determine the steady-state tracking gains as a function of gtrack. One can see that large assumed maneuvers (large q, aa, or a); larger time between updates, T; or very accurate radar measurements (small ℜ) will result in large tracking gains. |
306-310 paraboloid. 226 Fences. radar, 175. |
-...--2.2 .-...—.-.---L.f...–.l :- _.L--L__,.. _. .L:.--:- .-..-;.11.. |
Amplifiers may be placed between the individual antenna elements and the beam- forming (phase-shifting) networks to amplify the incoming signal and compensate for any losses in the beam-forming networks. The output of each amplifier is subdivided in to a nurnber of independent signals which are individually processed as if they'were from separate receivers. Postamplification beam forming. |
12.20. The swept oscillator must produce a linear sweep; this is easy with yttrium- iron-garnet (YIG)-tuned oscillators but requires linearizing circuits if tuning uses a varactor. If dual antennas are used (as shown), the overlap of the beams must be considered.69 Single-antenna systems are sometimes used, with a circulator isolating transmitter and receiver; their performance is somewhat poorer than that of dual-antenna systems because of internal reflections and leakage through the circulator. |
44Scattering Mechanisms Double diffraction from sharp corners Diffraction from rounded objectSPECULAR DUCTING, WAVEGUIDE MODESMULTIPLE REFLECTIONS EDGE DIFFRACTIONSURFACE WAVES CREEPING WAVES• Scattering mechanisms are used to describe wave behavior. Especially important at radar frequencies:specular = "mirror like" reflections that satisfy Snell's law surface waves = the body surface acts like a transmission line diffraction = scattered waves that origin ate at abrupt discontinuities. 45Example: Dipole and Box •f =1 GHz, −100 dBm (blue) to −35 dBm (red), 0 dBm Tx power, 1 m metal cube ANTENNABOX Reflected Field OnlyREFLECTEDIncident + Reflected Reflected + Diffracted Incident + Reflected + Diffracted ANTENNABOX Reflected Field OnlyREFLECTEDIncident + Reflected Reflected + Diffracted Incident + Reflected + Diffracted. |
22. George, S. F.: EKectiveness of Crosscorrelation Detectors, Proc. |
CIRCLE DISTANCE AND BEARING GRID REGISTRATION REQUIRES THAT TILT OR GRADIENT EFFECTS BE TAKEN INTO ACCOUNT 4HE DAYTIME EXAMPLE HAS LITTLE HORIZONTAL GRADIENT AND THE SIMPLIFYING ASSUMPTION MAKES LITTLE DIFFERENCE 7HEN BETTER ACCURACY IS DESIRED THE CORRECT VERTICAL PROFILE CAN BE USED FOR EACH RADIATION ANGLE ALSO GRADIENTS CAN BE SIMULATED BY MAKING THE IONOSPHERE NONCONCENTRIC WITH THE %ARTH ! MORE COMPLETE PATH ANALYSIS SHOULD BE USED IN RADAR PERFORMANCE ASSESSMENT AND MANAGEMENT BUT THESE PLASMA DENSITY CONTOURS CAN BE USED TO ESTIMATE THE MAGNITUDE OF THE ERRORS INTRODUCED BY THE ASSUMPTI ON OF A SPHERICALLY SYMMETRIC IONOSPHERE &IGURE SHOWS A PERFORMANCE PREDICTION FOR A HYPOTHETICAL RADAR IN THE FORM OF AN OBLIQUE SOUNDING ! TYPICAL SKYWAVE RADAR IS SUPPORTED BY ONE OR MORE VERTI |
In fact, in the latter case the useful signal is integrated while the interference is canceled. The implementation of an adaptive array has been limited to experimental sys- tems with a small number of antennas (say, 10), so that the matrix inversion can be handled by practical computing systems.44'45 Arrays with a large number of receiving elements need some form of processing reduction. One method of par- tial adaptivity is to arrange the array elements in subgroups which form the inputs of the adaptive processor. |
BASED OR HELICOPTER SYSTEM THAT IS WELL CALIBRATED AND TO COMPARE THE IMAGES TO THESE MEASURED VALUES &)'52% "ASIC BLOCK DIAGRAM OF AN &- |
W. Meadows, and P.A. Matthews: Layer Structure of the Troposphere, !'roe. |
Inorder toreduce hunting, astabilizing transformer (Fig. 1413) isnow used with most of thelarger alternators. Such atransformer provides acorrection depend- ingontherate ofchange ofexcitation. |
H. S.: Characteristics of Triangular Lattice Arrays, Proc. IEEE, vol. |
Sometimes the terms /cr·d and cross IC'l'el are used to refer to the angles in a stabilized system. 14 The /ere/ angle is the angle between the horizontal plane and the deck plane, measured in the vertical plane through the line of sight. The cross-level angle is the angle, measured about the line of sight. |
King, D. D.: The Measurement and Interpretation of Antenna Scattering, Proc. IRE, vol. |
If the clutter cross section is log normal, the probability density function describing its statistics is p(oJ = -.~ · exp [----~2 ( In <le )2 ] .,/ 21[ (J(j C 2a (J' m <Jc> 0 (13.lla) where <J, clutter cross section a,., median value of a, a itandard deviation of In <re (natural logarithm) The probability density function that describes the statistics of the voltage amplitude at the output of the envelope detector when Eq. (13.l la) is the clutter input, is given by (13.llb) where ,,,,, is the median value of v and u remains the standard deviation of ln <1, .114 A fit of the Jog~normal probability density function with a = 6 dB to actual data for sea state 2 to 3 is shown in Fig. 13.5. |
DELAY SECTIONS AS SHOWN IN &IGURE &)'52% &OUR |
The conventional definition is the angular width of the beam between the half- power points of the pattern. Pattern is used here in the usual antenna sense, for one-way transmission. It is not the two-way pattern of the radar echo signal from a stationary target as the antenna scans past it. |
Ê- 1 / |
Table 13.2 lists examples of the Weibull parameter ex (in Eq. 13.12) for several types of clutter and sea state. Land clutter models. |
Theproblem ofsynthesizing optimum waveforms fromanambiguity diagram specified byoperational requirements isadifficultoneandisoften approached bytrialanderror. Thenameambiguity function forIX(TR,fd)12issomewhat misleading sincethisfun,::tion describes moreaboutthewaveform thanjustitsambiguity properties. Woodwardscoinedthe nametodemonstrate thatthetotalvolume underthisfunction isaconstant equalto(2E)2, independent oftheshapeofthetransmitted waveform, [Eq.(11.54)]. |
60. Johnson, J. B.: Thermal Agitation of Electricity in Conductors, Phys. |
Since the antennas generally used in pulse doppler radars have a single, relatively high- gain main beam, main-beam clutter may be the largest signal handled by the radar when in a down-look condition. The narrow beam limits the frequency extent of this clutter to a relatively small portion of the doppler spectrum. The remainder of the antenna pat - tern consists of sidelobes, which result in sidelobe clutter. |
Remote Se11si11g. All radars are remote sensors; however, as this term is used it implies the sensing of geophysical objects, or the'.' environment." For some time, radar has been used as a remote sensor of the weather. It was also used in the past to probe the moon and the planets (radar astronomy). |
In general, the effective noise temperature has been preferred fgr describing low-noise devices, and the noise figure is preferred for conventional receivers. For radar receivers the noise figure is the more widely used term, and is what is used in this text. 18 Measurement of noise figure. |
D. West, “ECM modeling for multitarget tracking and data association,” in Multitarget-Multisensor Tracking: Applications and Advances , vol. III, Y . |
SIZE DISTRI |
F. Gabriel, Guest editor, special issue on adaptive antennas, IEEE Trans ., vol. AP-24, September 1976. |
The d-crestorers V.hold thesweep origin fixed regardless ofduty ratio. Two fixed and one variable sweep speeds are shown. The square- wave generator isautomatically turned offatthe proper time bythe action ofV1.The positive sawtooth isdelivered tothegrid ofV,,which isbiased beyond cutoff bysuch anamount that itstarts toamplify just asthesawtooth reaches the desired peak amplitude. |
On the other hand. the radars cannot be placed too Pdr apart since tlie curvature of the cart11 will limit the minimum altitude at which targets can be seen. For example. |
If there is precipitation in thecloud then the operator can expect a detectable echo. Hail With respect to water, hail which is essentially frozen rain reflects radar energy less effectively than water. Therefore, in general the clutter andattenuation from hail are likely to prove less detectable than that from rain. |
SECTIONS OF TERRAIN NEAR VERTICAL INCI |
30.Ashmead, J.,andA.B.Pippard: TheUseofSpherical Reflectors asMicrowave Scanning Aerials,J. IEEE(London), vol.93,pt.IlIA,p.627,1946. 31.Ramsey, 1.F.,andJ.A.C.Jackson: Wide-angle Scanning Performance ofMirrorAntennas, hiarconi Rev.,vol.19,3dqtr.,pp.119-140, 1956. |
21.16x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 21 Ground Penetrating Radar David Daniels ERA Technology 21.1 INTRODUCTION The terms ground penetrating radar (GPR), ground probing radar, subsurface radar, or surface penetrating radar (SPR) refer to a radar-based electromagnetic technique designed primarily for the location of objects or interfaces buried beneath the Earth’s surface or located within a visually opaque structure. |
In the transmit condition (Fig. 9.6~) power is divided equally into each waveguide by the first short- slot hybrid junction. Both TR tubes break down and reflect the incident power out the antenna arm as shown. |
Anytargettotherightofcurve6maybeconsidered tobewithinthediffraction region.This illustrates whymostradarsoperating atmicrowave orUHFfrequencies arelimitedtocover agewithinthegeometrical lincofsight. 12.7A'n'ENUATION BYATMOSPHERIC GASES5.12.28 Theattenuation ofradarenergyinaclearatmosphere intheabsenceofprecipitation isdueto thepresence ofoxygenandwatervapor.Attenuation resultswhenaportionoftheenergy incident onthemolecules oftheseatmospheric gasesisabsorbed asheatandislost.The reduction inradarsignalpowerwhenpropagating overadistance Randback(two-way path) maybeexpressed asexp(-2exR),whereexisthe(one-way) attenuation coefficient measured in unitsof(distance) -'.Insteadofplotting ex,itismoreusualtoplottheone-way attenuation in decibels perunitdistance. Thisisequivalent toplotting thequantity 4.34ex,wheretheconstant accounts fortheconversion fromthenaturallogarithm tothebase10logarithm. |
CESS !N ENORMOUS LITERATURE IS DEVOTED TO THE THEORY OF SURFACE SCATTER FROM THIS POINT OF VIEW STEMMING FROM THE IMPORTANCE NOT ONLY OF RADAR SEA SCATTER BUT ALSO RADAR GROUND SCATTER AND SONAR REVERBERATION THE ACOUSTIC EQUIVALENT OF RADAR CLUTTER FROM BOTH THE SURFACE AND THE BOTTOM OF THE SEA "ECAUSE THE '"60 APPROACH LEADS TO THE ANALYTICAL EXPRESSION OF THE "RAGG SCATTERING HYPOTHESIS THAT HAS DOMINATED THE THEORY OF SEA SCATTER SINCE THE LATE S A BRIEF EXPLANATION OF SOME OF THE CENTRAL IDEAS IS INCLUDED BELOW 4HEORIES "ASED ON 'LOBAL "OUNDARY |
The ratio of the actual boresight velocity to the coplanar boresight velocity is defined as the normal - ized boresight-velocity ratio: VBR = =cos coscosα ψφ0 00 (3.2) where f0 is the depression angle of the antenna centerline from the horizontal. Figure 3.5 shows the variation of the normalized boresight-velocity ratio as a function of slant range for a curved earth and different aircraft altitudes. The variation is fairly rapid for slant ranges less than 15 nmi. |
Magellan: Innovative Venus Mapper. Magellan (Figure 18.15) had to face up to two driving mission restraints: cost and data rate. The first was set by NASA and the U.S. |
The radialcoordinate canalsobespecified bythereflection coefficientroftheloadsincethe VSWRpandreflection coefficient arerelatedbytheequationIrI=(p-1)j(p+1).The centeroftheSmithchart(Riekediagram) corresponds tounityVSWR,orzeroreflection coefficient. Thecircumference ofthechartcorresponds toinfiniteVSWR,orunityreflection coefficient. Thustheregionoflowstanding-wave ratioistowardthecenterofthechart.. |
53. Ward, H. R., and W. |
Since these devices exhibit this narrow operating range, small decreases in the input RF drive level to a multistage amplifier may bring the final tier of devices out of saturation. Failure to control these conditions accurately can result in unacceptably degraded output pulse fidelity. In a very simple sense, the design of an amplifier module consists of matching the power transistors to the proper impedance level and then combining the power levels at these impedances. |
ECHO THEORY 4HE PAIRED |
L. Rubin, Radar Detection, Norwood, MA: Artech House, Inc., 1980. 69. |
Noradar system iscomplete until adequate provisions forperformance testing and maintenance have been made and appropriate maintenance procedures prescribed. The most important function oftest equipment inradar maintenance istopermit quantitative measurement ofthose properties ofthesystem which affect itsrange performance. Experience has shown that itis essential todetermine byreliable quantitative methods how well aradar is operating. |
CHAPTER FOUR MTI AND PULSE DOPPLER RADAR 4.1 INTRODUCTION The doppler frequency shift [Eq. (3.2)] produced by a moving target may be used in a pulse radar. just as in the CW radar discussed in Chap. |
1.2 RADAR HANDBOOK 6x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 1 airport-surveillance radars. Its wavelength might be about 10 cm (rounding off, for simplicity). With the proper antenna such a radar might detect aircraft out to ranges‡ of 50 to 60 nmi, more or less. |
Metcalf shows strong evidence that the region penetrated by the aircraft, while appearing to be free of echo, had actually been obliterated because of severe attenuation. Severe storms can also produce very strong absorption at 5-cm wavelength, as noted by Allen et al.16 In some meteorological radar applications, it is desirable to attempt to mea- sure attenuation along selected propagation paths. This is done because absorp- tion is related to liquid-water content and can provide useful information for the detection of such phenomena as hail, in accordance with the dual-wavelength technique described by Eccles and Atlas.17 In the following subsections, quantitative expressions relating attenuation to precipitation are given. |
Any use is subject to the Terms of Use as given at the website. Phased Array Radar Antennas. PHASED ARRAY RADAR ANTENNAS 13.256x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 13 phasing for which the couplings from many elements will add in-phase to cause a large reflection in a typical element. Consider an array in which the velocity of the surface wave is that of free space. |
12.1. Inaddition tothescreen, these consist ofahot-cathode electron source, a“control grid” whose potential deter- mines thebeam intensity, and amechanism fordeflecting thebeam. In theexample illustrated, the deflection mechanism consists oftwo orthog- onal pairs ofparallel plates between which the beam must pass, the deflection due toeach pair being proportional tothe potential across it. |
New York. 1970. 51. |
These effects are discussed below. Amplitude fluctuations. A complex target such as an aircraft or a ship may be considered as a number of independent scattering elements. |
Defense Science Board, Future DoD Airborne High-Frequency Radar Needs/Resources, Office of the Under Secretary of Defense for Acquisition and Technology, Washington, DC, April 2001. 13. M. |
WAVE CIRCUIT IS USED IT IS CALLED A GYRO |
Jitter is usually dependent primarily on a single stage and is therefore usually not budgeted among stages. RF Leakage. A typical amplifier chain may have 90 dB of gain at the trans- mitter frequency in one shielded room or one location. |
Neyman-Pearson observer. The threshold level was selected in Chap. 2 so as not to exceed a specified false-alarm probability; that is, the probability of detection was maximized for a fixed probability of false alarm. |
I.: Tlie Band Retween Microwave and Infrared Regions, Proc. IRE. vol. |
RANGE DIMENSION CAN BE OBTAINED BY EMPLOYING THE DOPPLER FREQUENCY DOMAIN BASED ON 3!2 SYNTHETIC APERTURE RADAR OR )3!2 INVERSE SYNTHETIC APERTURE RADAR SYSTEMS AS DISCUSSED IN #HAPTER 4HERE NEEDS TO BE RELATIVE MOTION BETWEEN THE TARGET AND THE RADAR IN ORDER TO OBTAIN THE CROSS |
Anaircraftwouldbeflownona radialcourseandoneachscanoftheantenna itwouldberecorded whetherornotatargetblip hadbeendetected ontheradardisplay.Thiswasrepeated manytimesuntilsufficient datawas obtained tocomputc. asafunctigllQ[r1!.llge, theratiooftheaverage num~erofscansthetarget wasseenataparticular range(blips)tothetotalnumber oftimesitcouldhavebeenseen (scans).Thisistheblip-scan ratioandistheprobability ofdetecting atargetataparticuJar range.altitude, andaspect.Thehead-on andtail-onarethetwoeasiestaspectstoprovide in fieldmeasurements. Theexperimentally foundblip-scan ratiocurvesaresubjecttomany limitations, butitrepresents oneofthefewmethods forevaluating theperformance ofan actualradarequipment againstrealtargetsundersomewhat controlled conditions.. |
Deception jammers have a number of specific characteristics that can be used by radars to identify their presence. The most prominent is that false-target returns must usually follow the return from the jammer-carrying target and must all lie in the same direction within a radar PRI. If the deception jammer uses a delay that is greater than a PRI period to generate an anticipatory false-target return, then pulse-to-pulse PRI jitter identifies the false-target returns. |
It is a good technique OTHER RADAR TOPICS543 Monopulse. Anelevation anglemeasurement canbemadesimilartothatofthemonopulse radardescribed inSec.5.4.Twofanbeamsarcdisplaced ("squinted ")inelevation angleand thesumanddifference patterns areobtained. Themeasurement ofangleissimilartothatofan amplitude-comparison monopulse tracking radarexceptthatitismadeopenloop;i.e..the outputvoltage fromtheangle-error detector iscalibrated toreadelevation angle.Two displaced hornswithcombining circuitry. |
H.: Helix Frequency Scanning Feed, Microwaoe J., vol. 8, pp. 39-44, December. |
2.22, bandwidths of1to4Me/see arecommon. The narrowest r-fcomponent, ahigh-Q TR switch, isso much wider than this that, once adjusted, nodrifts large enough tocause serious detuning are likely tooccur over aperiod ofaday orso. The problem ofkeeping aradar intune, then, consists essentially inmaintain- ing the difference between the magnetron frequency and the local- oscillator frequency constant and equal tothe intermediate frequency, with anaccuracy of1Me/see orbetter. |
CHANGING IONOSPHERE 4HIS CHAPTER SETS OUT TO EXPLAIN THE PRINCIPAL FEATURES OF (& SKYWAVE RADAR AS IT IS PRESENTLY IMPLEMENTED EMPHASIZING THE PHYSICAL CONSIDERATIONS THAT GOVERN SYSTEM DESIGN AND PERFORMANCE Óä°ÓÊ / |
However, if one does this, the homogeneity assumption (i.e., all the reference cells are sta- tistically similar) might be violated. A good rule of thumb is to use enough refer- ence cells so that the CFAR loss is below 1 dB and at the same time not let the reference cells extend beyond 1 nmi on either side of the test cell. For a particular radar this might not be feasible. |
and S. S. Allwood: "Radio Wave Propagation," Academic Press. |
4.Bayma, R.W.,andP.A.Mcinnes: Aperture SizeandAmbiguity Constraints foraSynthetic Aperture Radar,IEEE1975International RadarConference, pp.499-504, IEEEPublication 75CHO 93~-1 AES.(Alsoavailable inref.1.) 5.Cutrona, L.J.:Optical Computing Techniques, IEEESpectrum, vol.I,pp.101-IO!i, Octobt:r, 1964. 6.Kirk,J.c.,Jr.:ADiscussion ofDigitalProcessing inSynthetic Aperture Radar,/EEETrw/s., pp.326-337, May,1975.(Alsoavailable inref.1.) 7.Leith,E.N.:Optical Processing Techniques forSimultaneous PulseCompression andBeamSharp ening,IEEETrans.,vol.AES-4,pp.878-885, November, 1968.(Alsoavailable inref.1.) 8.Raney,R.K.:Synthetic Aperture Imaging RadarandMoving Targets, /EEETnHls.,vol.AES-7, pp.499-505, May,1971.(Alsoavailable inref.1.) 9.vandeLindt,W.J.:DigitalTechniques forGenerating Synthctic Apcrture RadarImages, /BMJOllr. ofResearch andDevelopment, vol.21,no.5,pp.4t5-432, September, 1977. |
20.Holland, M.G.,andL.T.Claiborne: Practical SurfaceAcoustic WaveDevices. Proc.IEEE,vol.62, pp.582-611, May,1974. 2\.Maines.J.D..andE.G.S.Paige:Surface-Acoustic-Wave DevicesforSignalProcessing Applications. |
An HF radar must be designed to accommodate such clutter levels even though they will not exist all the time or at any one time over all areas, es- pecially at the lower operating frequencies. NORMALIZED DOPPLER (fd/\/~g7*tt FIG. 24.3 The nominal maximum values of the seascattering coefficient are given as a function of doppler frequency for a coherent processing time of 51 s. |
Beam scan mode analysis and design for geosynchronous SAR. Sci. China (Inf. |
Multiple sets ofindices with different scale factors ran be. SEC. 73] AIDS TO PLOTTING AND CONTROL 219 conveniently provided byruling each individual setonathin transparent sheet. |
(a)Search antenna pattern. (b) Homing antenna pattern. results from improper installation ortrimming ofantennas, hasthesame operational effect ascrabbing ofthe aircraft inacross-wind; ineither case, theoperator notices that therelative signal strength oftheleft and right echoes changes when the aircraft issteady onacompass course initially chosen togive equal signals. |
The doppler component con t.1i11ed in the amplitude fluctuations may also be detected by applying the output of the amplitude detector to an A-scope. Amplitude fluctuations due to doppler produce a butterfly modulation similar to that in Fig. 4.3, but in this case, they ride on top of the clutter echoes. |
The two adjacent antenna feeds are connected to the two arms of a hybrid junction such as a .. magic T," a" rat race," or a short-slot coupler. The sum and difference signals appear at the two other arms of the hybrid. |
TATIVE ANALYSIS OF POLARIMETRIC 3!2 DATA 7HEN IN COMBINATION WITH INTERFEROMETRIC DATA THE FIELD IS KNOWN AS 0OL)N3!2 FOR WHICH DEDICATED SPECIALIST MEETINGS ARE CONVENED FREQUENTLY !N IMPORTANT METHODOLOGY IS TARGET DECOMPOSITION THROUGH WHICH SPECIFIC BACKSCATTER CLASSES SUCH AS DOUBLE |
S=A.tileindexofrefraction isequalto0.866.Thecloserthespacing, thelesswillbe theindexofrefraction andthethinnerwillbethelens.However, thespacing, andtherefore the indexorrefraction. cannot bemadearbitrarily smallsincethereflection fromtheinterface bctween theIcnsandairwillincrease justasinthecaseofthesolid-dielectric lenses.Fora valueors=,1./2.theilldexorrefraction iszeroandthewaveguide isbeyondcutoffThewave incident onthelenswillbecompletely reflected. Inpractice, acompromise valueoftTbetween 0.5and0.6isoftenselected. |
84. Bhagavan. B. |
Albersheim, W. J.: Elevation Tracking Through Clutter Fences, S11pplemelll to I £EE Trw1s .• vol. AES-3, pp. |
50. B. G. |
In the optically clear, lower atmo - spheric boundary layer, “clear air” Z values of the order –20 dB Z to 20 dB Z are typical and frequently originate from insects and birds.35,36 In rain Z may range from about 0–10 dB Z to as much as 60 dB Z, with a 55 to 60 dB Z rain being of the type that can cause severe flooding. Severe hailstorms may produce Z values higher than 70 dB Z. Many operational radar types are designed to detect those Z values that produce mea - surable precipitation (0 to 60 dB Z) and “clear air” echoes to 100 km where the Earth’s curvature prevents surface-based measurements. |
The optimal values for log-normal interference were calculated by Schleher19 and are M = 3, 8, and 25 for N = 3, 10, and 30, respectively. Batch Processor . The batch processor (Figure 7.3 e) is very useful when a large number of pulses are within the 3-dB beamwidth. |
It is not sufficient that only the first stage of a low-noise receiver have a small noise figure. The succeeding stage must also have a small noise figure, or else the gain of the first stage must be high enough to swamp the noise of the succeeding stage. If the first network is not an amplifier but is a network with loss (as in a crystal mixer), the gain G 1 should be interpreted as a number less than unity. |
The dynamic range (peak signal to rms noise) is limited to about 20 dB for a PPI display. A key distinction, sometimes lost in the complexities of the systems that follow, is that an MTI radar system eliminates fixed clutter because the phase of signals returned from consecutive transmitted pulses do not (appreciably) change. The fixed clutter is removed after as few as two transmitted pulses by the subtraction process described FIGURE 2. |
D. T. Sandwell and W. |
IRE, vol. 26, pp. 309-316, October, 1963. |