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BLOCKAGE REFLECTOR BLOCKING ITSELF IS ANOTHER POTENTIAL LIMITING FACTOR IN SPHER |
AIR SEARCH 4HE CHOICE BETWEEN HIGH AND MEDIUM 02& INVOLVES A NUMBER OF CONSIDERATIONS SUCH AS TRANSMITTER DUTY CYCLE LIMIT PULSE COMPRESSION AVAILABILITY SIGNAL |
Kittredge, F., E. Ornstein, and M. C. |
Amplitude scintillation effects on SAR. IET Radar Sonar Navig. 2014 ,8, 658–666. |
ORTHOGONALITY ON THE SCATTERING PROPERTIES OF DIHEDRAL REFLECTORS v )%%% 4RANS VOL !0 |
86. Mortley, W. S., and S. |
However, when the target is in motion relative to the radar, /4 has a value other than zero and the voltage corresponding to the dilkrence frequency from the mixer [Eq. (4.3)] will be a function of time. An example of the output from the mixer when the doppler frequency/;, is large compared with the reciprocal of the pulse width is shown in Fig. |
R. K. Moore, J. |
Each correlator may actually consist of several correlators, one for each quantization bit of the digitized signal. Two methods of implementing the correlators are shown in Fig. 10.13. |
It exhibits optimum performance when the pyra - mids are pointed toward the direction of the incident wave, and the pyramids should be of the order of 3 to 6 wavelengths deep. Fire-retardant paint is usually applied to pyramidal absorbers to satisfy safety requirements, but at high frequencies, the paint tends to degrade the performance of the material. Nevertheless, pyramidal absorbers of sufficient depth consistently turn in performances better than (less than) −50 dB. |
WATER CONTENT AND IS INDEPENDENT OF THE DROP |
Glint Reduction in the Bistatic RCS Region. A second effect can occur in the bistatic region. When the bistatic RCS reduction is caused by a loss or attenuation of ch23.indd 20 12/20/07 2:21:34 PMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2008 The McGraw-Hill Companies. |
Zrnic, and C. L. Frush, “Review of range velocity ambiguity mitigation tech - niques,” in 29th Conf. |
Timing signals are also supplied to the indicator to provide the range zero. Angle information is obtained from the pointing direction of the antenna. The most common form of cathode-ray tube display is the plan position indicator, or PPI (Fig. |
SUREMENT CELL AND 3.2 IS THE SIGNAL |
10.45a; Fig. 10.45b shows the equivalent circuit ofaprac- tical transformer (all values referred tothe secondary orhigh-voltage Low-voltage High-voltage end end :~~[, ;q-R[L (a) (b) FIG. 10.45.—Puke transformer circuit diagram. |
'l'lic pliasc-phase array is what is generally implied when the term elrc~~r~o~tic~c~llr .\reclrctl phctseel clr.rirJ1 is used. The phased array antenna has seen application in radar for such purposes as aircraft sirrveillatice fro111 on board sflip (AN/SPS-33), satellite surveillance (AN/FPS-85). ballistic rriissile defense (PAR, MSR), air defense (AN/SPY-1 and Patriot), aircraft landing systeriis (AN/TPN-19 and AN/TPS-32), mortar (AN/TPQ-36) and artillery (AN/TPQ-37) location. |
If saturations do occur in a range gate during an integration period, an option in a multiple-range-gated system is simply to blank detection reports from that gate. Tb most stressing dynamic-range requirement is due to main-beam clutter when searching for a small low-flying target. Here, full sensitivity must be main- tained in the presence of the clutter to maximize the probability of detecting the target. |
J. H .. and D. |
12.12. The dotted portions arethe additions necessary toinclude beacon AFC. SEC. |
14. PRIME POWER SUPPLIES FOR RADAR. 555 .41RCRAFT SYSTEMS 141 14.2 143 14.4 145 14.6 14.7 14.8 14.9Choice ofFrequency. |
Feedback can be used to narrow the rejection notch without much degradation of I. If feedback is used to increase the improvement factor, the single-scan probability of detection becomes worse. Figure 2.37 shows the improvement factor limitation due to scanning for cancelers with feedback. |
(ILL #HAP & .ATHANSON 2ADAR $ESIGN 0RINCIPLES .EW 9ORK -C'RAW |
Results of most of these measurements are summarized in Ulaby, Moore, and Fung37 and Ulaby and Dobson.38 More complete summaries of the earlier work and near-grazing studies are in Long22,39 and in the work of Billingsley.17 Many applica - tion summaries are also in the Manual of Remote Sensing .40,41 Readers requiring more detailed information should consult these books . 16.2 PARAMETERS AFFECTING GROUND RETURN Radar return depends upon a combination of system parameters and ground parameters: Radar system parameters (Eqs. 16.1 and 16. |
ARRAY OUTPUTS IS EQUAL SUBSEQUENTLY THE MISSING TAPER WEIGHTS ARE APPLIED DIGITALLY AT SUB |
WAVE METHODS 0HYSICAL /PTICS 0/ 2EFLECTOR !NALYSIS 4HE 0HYSICAL /PTICS 0/ METHOD IS COMMONLY EMPLOYED FOR THE MOST RIGOROUS REFLECTOR ANALYSIS DUE TO ITS ACCURACY )T INCORPORATES THE FIELD PROPERTIES OF THE FEED AND MODELS THE RESULTANT FIELDS FROM THE REFLECTOR THUS ENABLING THE COMPUTATION OF THE CROSS POLARIZATION PROPERTIES &URTHERMORE THE METHOD IS MORE ACCURATE FOR FEEDS THAT ARE NOT AT THE FOCAL POINT AND REFLECTORS THAT ARE NOT PARABOLIC 4HERE ARE MANY GOOD REFERENCES THAT DESCRIBE THE THE |
SEC. 9,5] CONSTRUCTION OF RADAR ANTENNAS 279 Beacon antennas areoften made upofavertical array ofradiating elements excited inphase. Bycorrect design ofsuch anantenna the pattern canbemade reasonably uniform inazimuth and atthesame time well confined totheregion ofthehorizon. |
The natural result in this case is the so- called dawn-dusk orbit, in which the satellite—and its solar-panel-dependent power system—avoids the shadow of the Earth almost always for almost all seasons. Certain applications are particularly well-served by exact-repeat orbits. For exam - ple, if a group of orbital trajectories falls within a small radius of each other when over an area of interest, then radar measurements from several orbits may be compared coherently, thus potentially sensitive at the order of a wavelength to changes in the scene between observations. |
XXYXY R XR XR RYR YR RZR ZR R |
Burgers, J. Application of a Model System to Illustrate Some Points of the Statistical Theory of Free T urbulence ; Springer: Dordrecht, Netherlands, 1940. 20. |
IDEAL FILTER RESPONSES !N INFINITE NUMBER OF TAPS WOULD BE REQUIRED TO SET THE PASSBAND GAIN TO UNITY AND THE STOPBAND GAIN TO ZERO HOWEVER FOR MOST APPLICATIONS SUFFICIENT PROCESSING RESOURCES ARE AVAILABLE TO REDUCE THE ERRORS TO INSIGNIFICANT LEVELS &INITE LENGTH WORDS FOR FILTER COEFFICIENTS PRODUCE NON |
The antenna equivalent of the conventional Fourier transform is the Blass beam-forming network illustrated by Fig. 8.26. The Blass network required N~ couplers for N inputs and N outputs, while the conventional Fourier transform also requires NZ computations for an N-point transform. |
R. Forrest: Principles of Independent Receivers for Use with Co-operative Radar Transmitters, Radio Electron. Eng., vol. |
Themeasurement ofdistance relativetooneofthesitesrequires a knowledge ofboththeangleofarrivalatthereceiving siteandthedistance between transmit terandreceiver, aswasindicated byEq.(14.33).Anyofthemethods formeasuring rangewith amonostatic radarcanbeappliedtobistaticradar,including pulseandFM-CW modulations. Ifthedirectsignalfromthetransmitter isavailable atthereceiving site,itcanbelIsedasa reference signaltoextractthedoppler frequency shift.However, thedirectsignalcanseriously interfere withthemeasurement oftheangleofarrival,justasdoesamullipatl1 signal.To extracttheangular location ofthetarget,thedirectsignalmustbeseparated insomemanner fromthetargetsignals.Thisisnotaneasytasksincetheanglesofarrivalofthedirectand scattered signalsaregenerally closetooneanother whenthebistaticradarisarrangl:d to provide fencecoverage. BistaticRadarequation. |
11.27 Angles of incidence and scattering for wedge geometry. guished between "uniform" and "nonuniform" induced surface currents. The uniform currents are the surface currents assumed in the theory of physical op- tics, and the nonuniform currents are associated with the edge itself (filamentary currents). |
Puhl. no. 155. |
REGION APPROXIMA |
The first is to focus on one particular term of the radar range equation, the propagation factor FP (defined in Section 26.6). Encompassed within the propagation factor are all the effects upon propagation attrib - utable to the natural environment. These effects are energy absorption from gasses and liquid water, diffraction, refraction, multipath interference, earth-surface dielectrics, terrain interference, and a number of other natural environmental considerations. |
The local oscillator isa2K25 klystron, which can betuned mechani- cally over alarge range and electrically over arestricted range ofsome 30Me/see. The electrical tuning can bedone manually, bymeans ofa remote potentiometer, orautomatically. The AFC circuit operates asfollows. |
4IME !DAPTIVE 0ROCESSING 344 3INGLE 4ARGET 4RACKER 4O! 4IME OF !RRIVAL 43) 4ERRAIN 3CATTERED )NTERFERENCE 46 |
Burrows, and E. B. Ferrell: Ultra-Short-Wave Propagation, Proc. |
This content has been downloaded from IOPscience. |
RATED INTO PROBABILISTIC DATA ASSOCIATION v * %LEC %LECTRON %NG !USTRALIA )% !UST AND )2%% !UST VOL PP n 9 "AR |
ARRAY ARCHITECTURE THE MAXIMUM VALUE OF THE 3).2 IS LOG n TAPERING LOSSES &IGURE DEPICTS THE 3).2 FOR THE REGULAR ARRAY CONFIGURATION AND ABSENCE OF TAPERING )T IS NOTED THAT WHEN THE JAMMER $O! IS AROUND THE 3).2 DECREASES THIS IS BECAUSE OF THE GRATING LOBE 4HE MAXIMUM VALUE OF 3).2 IS D" LOG BECAUSE THERE ARE NO TAPERING LOSSES&)'52% 3).2 VERSUS THE JAMMER $O! *$O! |
I'- L. L L-_....l._----'- __ o10203040506070 GRAZING ANGLE (degrees) Figure13.8Boundaries ofmeasured radarreturnatXbandfromvarious landclutter. 35(Co/lrresyof1.Karz.)E22Z3CITYc==JCULTIVATED TERRAIN \::::::::::::;:;:::3ASPHALT c=JCONCRE TEVERTICAL POLARIZATION r 10'--__ .J--_-L-._~.L_L_----'--_----.L __ L.-_--'----_--.J 2030405060708090 GRAZING ANGLE (degrees)20 \0 0 -10 CD ~-20 0 b -30 -40 -50 -60 0 asoft.wetsnowcover onvegetation tendstolowerthereturnbyasmuchas6dB.40Measure mentsmadeoversnowfields nearThule,Greenland, showed thebackscatter tobepropor tionaltothesquareofthefrequency overthefrequency rangefromUHFtoXbandandat grazing anglesfrom5to20°:!? Frequency dependence. |
19.59. 115. Miller. |
The operational use made ofthe SCR-584 asmodified foraircraft control was basically any that required precise navigation under restricted visibility. Large aircraft could carry radio and radar navigational aids which often made itpossible forthem tocarry outsuch missions without assistance, but thefighters and fighter-bombers oftheTAC’S had neilhcr ———.——— FIG.7.17.—X-Y plotting board forSCR-584. space nor operators forsuch equipment. |
14.16 Subcarriers ........................................................ 14.16 Amplication ........................................................ 14.18 Doppler Filter Banks .......................................... |
Examples of passive ECM are chaff, decoys, and radar cross-section reduction. One of the earliest forms of countermeasures used against radar was cJu~ft: Chaff consists of a large number of dipole reflectors, usually in the form of metallic foil strips packaged as a bundle. The many foil strips constituting the chaff bundle, on being released fr9m an aircraft, are scattered by the wind and blossom to form a highly reflecting cloud. |
Because thunderstorms contain important spatial features, such as heavy precipita - tion shafts and updraft cores, with horizontal dimensions of the order 1 to 5 km, a 1 ° beam is reasonably well matched to these atmospheric phenomena being observed out to ranges of a few hundred km. Shorter-range airborne weather radars often employ beamwidths of 2–3 ° as a compromise between wavelength requirements and antenna size constraints whereas spaceborne radars may use a fraction of a degree beamwidth to retain usable horizontal resolution at typical long ranges (250–500 km). Operational weather radars normally are capable of short and long pulse operation in the range of 0.5 µs to about 6 µs and PRFs between 300 and 3000 Hz for long- range precipitation radars. |
LYZE THE SYSTEM IN THE TIME DOMAIN INSTEAD 4HIS IS 3!2 4HE EQUIPMENT REMAINS THE SAMEnJUST THE EXPLANATION CHANGES #ONCEPTION WAS REPORTED IN A 'OODYEAR !IRCRAFT REPORT IN v 3UBSEQUENTLY AS DESCRIBED IN 3ECTION OF 3CHLEHER $"3 CAME TO REFER TO AN AIRBORNE SCANNING MODE IN WHICH THE ECHOES FROM THE SCANNING REAL BEAM ARE DOPPLER |
Emerson, R. C.: Some Pulsed Doppler MTI and AMTI Techniques, Rand Corporation Kept. R-214, DDC Doc. |
2AYLEIGH RETURNS NOTED IN 3ECTION HAS LED TO AN AUGMENTATION OF THE TWO |
2.16x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 2 MTI Radar William W. |
Hence,the cross-range resolution of the focused synthetic aperture using Eq. (14.4) with L" = RJ/D is D dcr = R(J, = 2 (14.6) The resolution of the focused SAR is independent of the range and the wavelength, and depends solely on the dimension D of the real antenna. An example comparing the resolution of the conventional antenna and the two types of synthetic aperture antennas is shown in Fig. |
This is not so in radar. Both position (range or time delay) and velocity (doppler frequency) may in theory be determined simultaneously if the pa product and/or the E/No ratio are sufficiently large. The two uncertainty principles apply to different phenomena, and the radar principle based on classical concepts shouldnot be confused with the physics principle that describes quantum-mechanical effects. |
ELEMENT SLOTTED WAVEGUIDE PHASED ARRAY WITH D" GAIN IS ELECTRONICALLY SCANNED OVER on ACROSS TRACK COVERING A SWATH |
All rights reserved. Any use is subject to the Terms of Use as given at the website. Space-Based Remote Sensing Radars. 18.16 RADAR HANDBOOK 6x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 18 Modern space-based SARs owe their large mode variety to active electronic- steered antenna arrays. |
The two curves in Fig. 20.6« correspond to uniformly illuminated sum beams. In one case, the delta beam is formed by subtracting the upper and lower halves of a uniformly illuminated aperture. |
LOOK AZIMUTH RESOLUTION AVAILABLE FROM THE -AGELLAN ANTENNA COULD BE ABOUT METERS 3ECTION 4HIS IS ON THE ORDER OF TIMES SMALLER THAN THE SCI |
-ISSILE |
These lines ofconstant efficiency arethedotted lines looping upand totheright onthediagram. 101 1 1 o10 20 30 40 50 60 70 80 Current Inamperes—. 338 THE MAGNETRON A.VD THE PULSER [SEC. |
HERTZ DIFFERENCE FREQUENCY ;CALLED A K(Z PHASE SIGNAL IN THE FIGURE=x 4HERE IS A RADIO RECEIVER AND CONSEQUENTLY A |
143-144 externally coherent, 138 filter bank. 121-125, 127 IF cancellation, 126 improvement factor: antenna scanning. 134-136 antenna sidelobes, 145 clutter fluctuations. |
Substituting into this equation produces bADDER = 12 + CEIL[log2(103)] = 12 + CEIL[9.966] = 12 + 10 = 22 In practice, although the first adder stage must support this number of bits, lower order bits may be pruned from the adders in successive stages, as described by Harris.10 A CIC interpolating filter would be preceded by a FIR-filter-based interpolator. CIC interpolators are described in detail in the referenced literature. The Discrete Fourier Transform (DFT). |
138. Zhuk, M. S .. |
QUENCY MODULATE THE WAVEFORM OF A MAGNETRON AS IS NEEDED FOR PULSE COMPRESSION 4HUS POWER AMPLIFIERS ARE ALMOST ALWAYS USED FOR PULSE COMPRESSION APPLICATIONS -AGNETRONS ARE NOT STABLE ENOUGH TO BE SUITABLE FOR VERY LONG PULSES EG §S AND STARTING JITTER LIMITS THEIR USE AT VERY SHORT PULSE WIDTHS EG §S ESPECIALLY AT HIGH POWER AND AT THE LOWER FREQUENCY BANDS )TS MAXIMUM AVERAGE POWER IS OF THE ORDER OF SEVERAL KILOWATTS WHICH IS LESS THAN THAT REQUIRED FOR SOME MILITARY APPLICATIONS . £ä°£È 2!$!2 (!.$"//+ 3INCE THE MAGNETRON IS AN OSCILLATOR WITH A RANDOM STARTING PHASE ON EACH PULSE IT CAN |
(Receiver detection-criteria for compensating the effects of a change in clutter sta tistics with high resolution are discussed later in this section.) Third, if the pulse is too short, it might encompass only part of a large target such as a ship, and the target cross section might be reduced. However, if the echoes from the various parts of a large target are displayed without collapsing loss and if the operator knows the general shape of the target, there will be little, if any, loss in detectability. Antenna beamwidth. |
" |
TO |
All rights reserved. Any use is subject to the Terms of Use as given at the website. MTI Radar. MTI RADAR 2.56x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 2 have in the past been referred to as bipolar videos, but a more correct terminology is that of the complex envelope of the received signals. |
Inanormalfrequency-scan radar,thebeamdwellsateachangular resolution cell(beam width)foroneormorepulserepetition intervals. Another method forutilizing thefrequency domain toscananangular regionistoradiateasinglefrequency-modulated pulsewitha modulation-band wideenoughtoscanthebeamovertheentireangular region.Thus,overthe duration ofasinglepulse,theantenna beamscansallangles.Thisissometimes cal.ledwithin pulsefrequency scanning. 66.122(Thetermwithin-pulse scanning hasbeenapplied toother methods ofscanning, asdescribed inSec.8.7.)Thetransmitted waveform issimilartothe frequency-modulated pulsecompression waveform (chirp)discussed inSec.11.5.Thecarrier frequencies ofanyechopulsesreturned totheradarwillbedetermined bytheelevation angle ofthetargets.Thereceiver employs abankoffilters,eachtunedtoadifferent carrierfrequency whichinturncorresponds toadifferent angle.Thisisanalogous totheoutputofabeam forming matrix,asinSec.8.7.Thenumber offiltersdepends ontheantenna beamwidth and. |
Naturally occurring dihedrals, such as rough rock for - mations created by a large impact, could generate false water-ice signatures. To reduce the potential ambiguity of CPR and brightness measurements, the radar observations must be repeatable and should be correlated with other indicators. Chandrayaan-1 and the Lunar Reconnaissance Orbiter (LRO) include in each of their payloads a “Mini-RF” radar.110 The version for Chandrayaan-1 is at S-band (12-cm wavelength), with 150-m resolution at 16 looks. |
The chief factor that made this possible was the introduction of reliable. small, and inexpensive digital processing hardware. CHAPTER FOUR MTIANDPULSEDOPPLER RADAR 4.1INTRODUCTION Thedoppler frequency shift[Eq.(3.2)]produced byamovingtargetmaybeusedinapulse radar.justasintheCWradardiscussed inChap.3,todetermine therelativevelocityofa targetortoseparate desired moving targetsfromundesired stationary objects(clutter). |
GATE AND VELOCITY |
It is not enough to match one element in the pres - ence of all its terminated neighbors. The element will deliver power to its neighbors, and this loss in power corresponds to the average power lost when scanning. An ideal, although not necessarily realizable element pattern, would place all the radiated power into the scan region, giving a pattern like a cosine on a pedestal and thereby providing maximum antenna gain for the number of elements used. |
Thus, AREPS contains a fairly simplistic pulsed-radar model to calculate free-space propaga - tion loss from radar system parameters such as frequency, pulse length, etc. The models to do this calculation are taken from Blake28 and are fully described within the AREPS online help and the AREPS operator’s manual. Thus, AREPS’ radar system assessment model will not be repeated here. |
.The target echo causes a detection and initializes the motion estimation channel. The high [fine] resolution data are initially smoothed in range to decrease [coarsen] the range reso - lution. Then the processor looks for the range cell with the maximum energy content and computes the WVD [Wigner-Ville Distribution48] of that cell only. |
The purpose or unequal element spacing in a highly thinned array is to eliminate the grating lobes that would appear if equal element spacings of large value were used. Grating lobes are not necessarily undesirable, since the energy contained in the grating lobes can be used to detect targets. However, if this energy is distributed in the sidelobes by employing unequal spacings, it is wasted. |
If the sea surface is disturbed by the wind, the resulting fine-scale roughness decreases the power of the pulse reflected back to the altimeter. Hence, for wind speeds of more than about two knots, WS is inversely related to mean waveform power. In practice, the inflections of the idealized flat-surface response function waveform are softened by the pulse weighting, and the waveform is attenu - ated over time by the weighting of the antenna pattern. |
Relaxing the Brightness Constancy Assumption in Computing Optical Flow ; A.I. Lab Memo 975; Massachusetts Institute of Technology: Cambridge, MA, USA, 1987. 32. |
HAND SIDE IS DOMINATED BY THE RADAR MEASUREMENT NOISE COMPONENT "ECAUSE THE GAINS HORIZONTAL AXIS ARE THE DESIGNERS CHOICE THE SINGLE RADAR 2/5 IS THE MINIMUM OF THE hBATHTUBv CURVE .OW CONSIDER THE FUSION OF TWO RADARS IN A PARTICULAR DIMENSION )F ONE RADAR HAS ONE |
Simrson. JI. R.: Performance Measures and Optimization Condition for a Third-Order Sampled Data Tracker. |
AMPLITUDE INTERNAL WAVES )N A MORE SUBTLE WAY MODULATED CURRENTS ARE HELD RESPONSIBLE FOR SYNTHETIC APERTURE RADAR 3!2 IMAGES THAT CONTAIN THE EXPRESSION OF BOTTOM TOPOGRAPHY PRODUCED BY THE "ERNOULLI %FFECT IN SHALLOW WATERS )N EACH OF THE EXAMPLES CITED ABOVE THE CURRENT PRODUCES A CHANGE IN THE SURFACE ROUGHNESS WHICH CAN BE EXPECTED TO GIVE RISE TO A CHANGE IN SEA CLUTTER CROSS SECTION #ONTAMINANTS 4HE IDEA OF POURING OIL ON TROUBLED WATERS IS A FAMILIAR ONE THE ANGRY SURFACE WILL SMOOTH AND SUBSIDE )N ANOTHER AGE THE SURVIVAL |
This sweep may represent either asmall part ornearly allofthe period between successive pulses. Inthe former case, the particular range interval that appears onthe display isdetermined bythe delay elapsing between the transmission ofthe outgoing pulse and the starting ofthe range sweep. The general classification “type A” isused todescribe one-dimen- sional displays. |
OPTIMUM (OWEVER SUCH SOURCES MAY HAVE GREATER POWER AND ANTENNA GAIN AT THEIR DISPOSAL ALLOWING THE SIGNALS TO REACH THE RADAR RECEIVER WITH APPRECIABLE STRENGTH SOMETIMES AFTER PROPAGATION VIA HIGHLY DISTURBED AND NONSTATIONARY IONOSPHERIC PATHS AS COMMONLY OCCURS IN THE EQUATORIAL AND POLAR REGIONS 5NDER NORMAL CIRCUMSTANCES /4( RADARS SEEK TO FIND RELATIVELY CLEAR FREQUENCY CHANNELS IN THE USER |
SIGHT 4HIS CAN BE IMPORTANT IN HARBOR RIVER ISLAND AND ESTUARY REGIONS WHERE SHIELDING BY THE TERRAIN OR BUILDINGS CAN AFFECT RADAR RANGE ! SHIPBORNE !)3 STATION BROADCASTS INFORMATION DIVIDED INTO A NUMBER OF SETS 4HESE COMPRISE STATIC DATA SUCH AS THE SHIPS NAME TYPE LENGTH AND BEAM DYNAMIC DATA INCLUDING POSITION 3/' #/' AND HEADING AND VOYAGE |
Figure 12.11 shows a series of actual pulses, followed by a series of samples at range R1. The spec- trum of Fig. 12.10 is the spectrum of the envelope of samples at R1 (after low- pass filtering). |
The root ofthe difficulty isthat wehave todowith astatistical problem, agame of chance. The answers will begiven asprobabditics, and will depend upon many features ofthesystem bywhich thesignal ispresented tothe observer, aswell asupon the precise description ofthe “reasonable certainty” mentioned above. We approach theproblem byexamining first the character ofthenoise fluctuations. |
The measured radar cross section of a man has been reported3* to be as follows: Frequency, MHz 0, m2 The spread in cross-section values represents the variation with aspect and polarization. 44INTRODUCTION TORADAR SYSTEMS Table2.2Example radarcrosssectionsatmicrowave frequencies Squaremeters Conventional, unmanned wingedmissile Small,singleengineaircraft Smallfighter,or4-passenger jet Largefighter Medium bomber ormedium jetairliner Largebomber orlargejetairliner Jumbojet Smallopenboat Smallpleasure boat Cabincruiser Shipatzerograzing angle Shipathighergrazing angles Pickuptruck Automobile Bicycle Man Bird Insect0.5 1 2 6 20 40 100 0.02 2 10 SeeEq.(2.38) Displacement tonnage expressed inm2 200 100 2 1 0.01 10-5 where (J=radarcrosssectioninsquaremeters,f=radarfrequency inmegahertz, andDisthe ship's(fullload)displacement inkilotons.31Thisexpression wasderivedfrommeasurements madeatX,S,andLbandsandfornavalshipsrangingfrom2000to17,000tons.Although it isprobably validoutside thissizeandfrequency range,itdoesnotapplytoelevation anglesotherthangrazingincidence. Athigherelevation angles,asmightbeviewedfrom aircraft, thecrosssections ofshipsmightbeconsiderably lessthanatgrazing incidence, perhaps byanorderofmagnitude. |
m2 R = range to target, m L,, one-way propagation loss L., system losses The corresponding equation for the bistatic radar is I 'r histatic whnc < ;, -,--transmitting antenna gain in direction of target (i, = receiving a11te1111a gain in direction of target n,. = histatic cross section. m2 IJ, = transmitter-to-target distarn..:c. |
RADAR CLUTIER 515 85.Beasley.E.W.:EffectofSurface Reflections onRainCancellation inRadarsUsingCircular Polariza tion.ProcIEEE.vol.54.pp.2000-"2(Xll.December: 1966. 86.Kalafus. R.M.:RainCancellation Deterioration DuetoSurface Rellections inGround-Mapping RadarsUsingCircular Polarization. |
transfers theproblem ofexcessive accelerations tosome otherdirection; inthiscase,inthedirection oftheelevation axis.Athree-axis mountavoids theproblem ofexcessive acceleration. Thetwo-axis mountof(d)issimilarto(c)exceptthatitisarranged toprovide roll stabilization. Therolldatafromastableverticalcanbeappliedtothebasicrollaxiswithout theneedforcomputer ordersasrequired intheothertwo-axis mounts. |
The doppler frequency shift of the echo signal from a moving target also provides a measure of radial velocity. However, the doppler frequency measurement in many pulse radars is highly ambiguous, thus reducing its utility as a direct measurement of radial velocity. When it can be used, it is often preferred to successive range measurements since it can achieve a more accurate measurement in a shorter time. |
71. Aydin, K., T. A. |
They represent contiguous time (or range) samples with 3. 125-nanosecond (47-centimeter) resolution. A typical ocean-return shape for a 2-meter wave height is shown in Fig. |
AGED THE OVERALL WAVEFORM SET CAN RESULT IN BEING hSMEAREDv SPATIALLY IF THE RADAR IS MOVING AT ANY SPEED 4HE STABILITY OF THE TIMING INCREMENT IS VERY IMPORTANT AND GEN |
PRF of the radar. The abscissa can also be interpreted as the ratio of the doppler frequency to the average PRF of the radar. The canceler configurations shown are not the most general feedforward, feedback networks possible but, rather, are practical configurations easy to im- plement. |
Long, “Tradeoffs in the design of a spaceborne scanning pencil beam scatterometer: Application to Sea-Winds,” IEEE Transactions on Geoscience and Remote Sensing , vol. 35, pp. 115–126, 1997. |
AMPLITUDE MODULATION0 D PROBABILITY OF DETECTION 0# PULSE COMPRESSION0$) POSTDETECTION INTEGRATION NONCOHERENT INTEGRATION 0 &! PROBABILITY OF FALSE ALARM 0- PHASE MODULATION00- PULSE |