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Althougll the resolution of an HF radar is poorer in range and angle than that of tnicrowave radar, its resolution in the doppler-frequency domain is quite good. Targets not resolvable in range or angle can be readily resolved in doppler. After targets are resolved in doppler, measurements in range and angle can be made to a greater accuracy than given by the noniinal resolution in those coordinates. |
Jones, and J. W. Johnson, “The Seasat-A satellite scat - terometer,” IEEE Journal of Oceanic Engineering , vol. |
DAY REPEAT CYCLE PREFERRED OPERATIONS ARE DURING THE HOURS OF DARKNESS IN THE ASCENDING PASSES FOR MOST MODES EXCEPTING LOWER DATA |
December. 1957. 47.McMahon. |
The sampled range interval is selected so that clutter is likely to be the dominant signal. From this measurement of clutter doppler within the sampled range interval, compensation is made over the entire range of observation either by changing the reference signal from the coho or by adjusting the phase shifter inserted in one of the arms of the delay-line canceler. Generally, the average doppler frequency or phase shift is obtained by averaging the sampled range-interval over a number of pulse repetition periods. |
The upsampling is accomplished by zero insertion as described in the previous section, “Interpolation Filters.” Note that the processing only consists of delays and adds. Figure 25.37 a shows the sin( x)/x frequency response of a single-stage CIC deci - mator, where R = D = 8. The desired passband is the lightly shaded area centered at 0 Hz with bandwidth BW. |
(2) When taking sequential doppler measurements, the target’s velocity vector remains constant64 or predictable.62 For example, many doppler-only, precision range instrumentation systems were developed in the U.S. after WWII.9 Both beacon-aided and skin-track systems were developed. All required initialization of the track data, which was conveniently provided by the target’s launch coordinates. |
However, the field strength at, and just within, the geometrical hori~on decreases with decreas- ing frequency. It is concluded that if low-altitude radar coverage is desired beyond the geometrical horizon in the diffraction region, the frequency should be as low as possible. If, on the other hand, low-altitude coverage is to be optimized within the interference region and if there is no concern for coverage beyond the horizon, the radar frequency should be as high as possible. |
It is worth noting that in case Δfdiffers from zero (i.e., has a finite value) an unambiguous time interval Δτof the ISAR compressed signal registration has to be defined (i.e., Δτ=1/Δf). In a discrete time-frequency grid of the asteroid’s signal registration, the range compression can be expressed as ˆS(k,p)=R−1⎭summationdisplay r=0⎭summationdisplay g∈G⎭tildewideag[ˆtg(p)]·exp⎭parenleftBig j·2π·fr·ˆtg(p)⎭parenrightBig (10) 111. Sensors 2019 ,19, 3344 Figure 5. |
TIONS OF )-/ RADAR PERFORMANCE STANDARDS )N ADDITION IT WAS AGREED THAT THE )%# STANDARDS WOULD INCLUDE TEST PROCEDURES WHICH COULD BE USED BY NATIONAL MARITIME ADMINISTRATIONS SUCH AS THE #OAST 'UARD IN THE 5NITED 3TATES OF !MERICA TO TEST FOR CONFORMANCE OF SPECIFIC DESIGNS BY MANUFACTURERS TO )-/ AND )45 REQUIREMENTS 4ODAY VIRTUALLY ALL NATIONAL ADMINISTRATIONS USE )%# STANDARDS TO ASSESS RADAR AND MOST OTHER )-/ |
Consequently, the high precision tracking radars with typically 4000 to 8000 phase shifters and four or more phase shift bits have small resultant electrical axis error steps on the order of 0.1 milliradians or less. The electrical axis errors are essentially random and can be further reduced by averaging. Intentional dither of phase steps may be introduced to aid in averaging. |
For ex- ample, with two targets present at different dopplers, the two frequencies ob- served during the FM period cannot be unambiguously paired with the two frequencies observed during the no-FM period. Thus, typical high-PRF range- while-search radars use a three-segment scheme in which there are no- . FM, FM-iip, and FM-down segments. |
15. Goetz, L. P., and J. |
L. Posner, and J. P. |
'(Z DOPPLER RADAR FOR CLOUD OBSERVATIONS v * !TMOS /CEAN 4ECHNOL VOL PP n * ( 2ICHTER h(IGH |
The voltage across thecombination isthen jl(A +Bsin0)+~@ +Bcoso), where fland fzrepresent theaudi~frequency input voltages and Aand B areconstants. Since Aisgreater than B,theamplitude terms arealways positive. This voltage ismixed with aconstant-amplitude a-fsignal of frequency fj(which isused forAGC atthereceiver), and thecombination isused tomodulate asubcarrier ofsomewhat higher frequency than the maximum required forvideo signals. |
(o)Oscillator intune with i-fsignals. (~)Oscillator detuned.retain the video amplifier and make sure that the coherent oscillator is always well tuned tothei-fsignals. Noserious loss insignal-to-noise will occur ifthere isless than one-quarter ofabeat cycle ineach pulse. |
F. Gatelli, A. Guarnieri, F. |
J. Sullivan, Radar Foundations for Imaging and Advanced Concepts , Raleigh, NC: SciTech, 2004; previously published as Microwave Radar: Imaging and Advanced Concepts , Norwood, MA: Artech House, 2000. 2. |
126- 133. 65. Johnson, M. |
3 2 4 1ZLZLZLZL ZL2 λ 4λ 4λ 4 3λ 4sum Σ beam 1beam 2 difference Δbeam 1 beam 21 234 sum Σdifference Δ Figure 13.5 Reception with a monopulse antenna for the ψ−plane (equivalent θ−plane). Left: 6x λ/4 Hybrid. Right: Magic Tee. |
The train ofpulses is‘‘rectified” bythecathode-ray tube, sothat 4.5kclsecII II oscdlator Scansynchro Controlsynchro ——AY-101 AY-101 I Ampl!fler _Detector, T +300V &6sr47.—-- ‘F100k 3WA---- r * Im$150k f6SN7 --- M0,01 ?5k300k Pulsedoscillator +150V 4 +36SN7 47k --- ~r0.0001 IL L1 FIG.13.34 .—Synchro null indices. themarker appears asarow ofdots which merge except onfairly fast sweeps. Anoscillation ofthis sort ispreferable toasimple rectangular pulse ifthe signals are tobepassed through mixing orother circuits whose low-frequency response isnot asgood as demanded bythevery long (asmuch as~see) marker pulse. |
ING LOBES )N A SPECIFIC EXAMPLE PRESENTED IN &ARINA AND 4IMMONERI TWO CARRIER FREQUENCIES ARE USED AND THE VALUES OF DK WHERE h Dv IS THE INTER |
This permits the AFC crystal tobe operated atapredetermined power level. The alternative-taking the AFC information from the output signal ofthe radar crystal arising from transmitter power that leaks through the TR switch-has been used but suffers from serious disadvantages. The leakage power may be10to20times that desired formost favorable operation ofthecrystal, and isvariable from one TR tube toanother. |
Enhanced solar activity impacts on the ionosphere in many ways, but its most sig - nificant action from a radar perspective is to produce substantially higher ionization levels that persist at usable levels through the night, so higher radar frequencies can be employed and the minimum achievable range decreases. In addition, the height of the maximum electron density increases, so one-hop propagation can reach greater ranges. FIGURE 20.6 The variation of the monthly median sunspot number since 1956, the year of the first opera - tional skywave radar detections ch20.indd 17 12/20/07 1:15:36 PMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2008 The McGraw-Hill Companies. |
NUMBER O K &P X IS A FUNCTION OF POLARIZATION P GRAZING ANGLE X AND THE ELECTRICAL PROPERTIES OF SEAWATER H IS THE RMS SEA WAVEHEIGHT AND #Y IS THE SURFACE CORRELATION COEFFICIENT /F COURSE THE REDUCTION OF A COMPLICATED BOUNDARY |
If all those factors affecting radar range were known, it. would be possible, in principle, to make an accurate prediction of radar perfoqnance. But, as is true for most endeavors, the quality of the prediction is a function of the amount of effort employed in determining the quantitative effects of the various pa rameters. |
¤ ¦¥³ µ´§ ©¨ ¨¶ ¸· ·COSQ &)'52% 0HASOR DIAGRAM FOR SIMULTANEOUS SCANNING AND MOTION COMPENSATION. !)2"/2.% -4) ΰ£ WHERE P IS THE DIRECTION OF THE CLUTTER CELL WITH RESPECT TO THE ANTENNA POINTING ANGLE WHEN THE SECOND PULSE IS RECEIVED AND VR IS THE ANTENNA SCAN RATE 4HE SUBSCRIPTS ON THE RECEIVED SIGNALS 3I AND $I INDICATE THE PULSE RECEPTION SEQUENCE 4HE DIFFERENCE PATTERN $ IS USED TO GENERATE AN IN |
As shown in Figure 3b, the Lungui Highway is located close to three hydrological systems: the Xi River and the Rongui and Shunde Branch Rivers. Plenty of ponds and a large amount of silt are distributed along the route. Figure 3. |
This, unfortunately, is seldom done. It is suspected that sometimes the decision as to which RF power source to use is deter - mined by what the radar system designer thinks the buyer (or customer) of the radar desires. Sometimes the buyer will actually specify the type of transmitter to be delivered. |
POWER BEAMWIDTH IN %Q OR %Q WITH AN ERROR THAT IS USUALLY ONLY OR D" #LUTTER 3TATISTICS 3UMMARIES OF CLUTTER MEASUREMENTS MADE BEFORE ABOUT MAY BE FOUND IN SEVERAL OF THE STANDARD REFERENCE BOOKS ON RADAR AND RADAR CLUTTER !MONG THE PROGRAMS OF THIS PERIOD THE MOST AMBITIOUS WAS THAT PURSUED IN THE LATE S AT THE .AVAL 2ESEARCH ,ABORATORY .2, IN WHICH AN AIRBORNE FOUR |
Chen, W. C. Lee, R. |
Deng, Z.; Ke, Y.H.; Gong, H.L.; Li, X.J.; Li, Z.H. Land subsidence prediction in beijing based on ps-insar technique and improved grey-markov model. Giscience Remote Sens. |
NOISE RATIO NOT THE SIGNAL |
(8) Then, three pairs of sub-view images can be formed to get three position offsets. The system of equations is as follows. Δf=Tac/bracketleftBigg edr 3 2e3rd/bracketrightBigg , (9) where: Δf=[Δfd,12Δfd,13Δfd,23]T Tac=⎡ ⎢⎣tac,1−tac,2 t2 ac,1−t2 ac,2t3 ac,1−t3 ac,2 tac,1−tac,3 t2 ac,1−t2 ac,3t3 ac,1−t3 ac,3 tac,2−tac,3 t2 ac,2−t2 ac,3t3 ac,2−t3 ac,3⎤ ⎥⎦. |
It is used for a irborne missile approach tracking , air traffic c ontrol, and medical applications ( e.g. blood flow monitoring ). The RF pulse characteristics reveal a great deal about a radar's capability. |
DOPPLER PLANE WITH ZERO RELATIVE TIME DELAY AND ZERO DOPPLER FREQUENCY AND THE SECOND TARGET IS AT RELATIVE TIME DELAY S AND DOPPLER FREQUENCY F D 4HE RELATIVE TIME DELAY IS POSITIVE WHEN THE SECOND TARGET IS FARTHER IN RANGE THAN THE REFERENCE TARGET AND THE DOPPLER FREQUENCY IS POSITIVE FOR AN INCOMING TARGET 4HE MATCHED |
FREQUENCY RADAR &2 OPERATING WITH BOTH HORIZONTAL AND VERTICAL POLARIZATIONS AT 5(& -(Z , BAND -(Z # BAND -(Z AND 8 BAND -(Z MADE CLUTTER MEASUREMENTS UPWIND DOWNWIND AND CROSSWIND IN WINDS FROM TO KT FOR GRAZING ANGLES BETWEEN AND 4HE SYSTEM WAS CALIBRATED AGAINST STAN |
REFLECTOR ANTENNAS 12.376x9 Handbook / Radar Handbook / Skolnik / 148547-3 / Chapter 12 mass and volume constraints generally have a significant impact on the reflector system design. Furthermore, some sort of stowage and deployment of the reflector is some - times required, especially for larger reflectors. These considerations and constraints drive the choices of materials, structural designs, passive and active mechanisms, etc. |
This page has been reformatted by Knovel to provide easier navigation. xxvi Contents Phase-Comparison Monopulse .......................... 18.17 Monopulse Tracking with Ph ased Arrays ............ |
Int. J. Appl. |
This fluctuation is referred to as fading . Fading is significant for the radar engineer because one must account for the fact that a single sample of the radar return may vary widely from the mean described by s 0. Thus , the system must be able to handle the dynamic range of fading, which may exceed 20 dB. |
One of the attractions or the rigid radome is its ability to withstand the rigors of severe climate. Rime ice, I.he prevalent type or icing found in the Arctic region, has little or no effect on most radomes. Although it tends to collect on many types of structures and can obtain large thicknesses. |
Azimuth Resolution Factor of the Ambiguity Function. The azimuth resolu- tion capability of the system can be determined from an evaluation of the sum term written as the factor in Eq. (21.26). |
· t\ New Aprroach to I .inear Filtering and Prediction Problems. Trans. ASM E . |
29 -30, May 1, 19 58, AFCRC-TR-58- 145(1), ASTl A Document 152409. 58. Bacon, G. |
M. A. Sletten and D. |
and G.S.; Resources, Z.B.; Software, Y.W. Funding: This research was funded by the National Key R&D Program of China, grant number 2017YFC1405600. Conflicts of Interest: The authors declare no conflict of interest. |
BEAM CLUTTER RETURN IS POSITIONED TO $# THROUGH CLUTTER POSITIONING VIA AN &)'52% 3IDELOBE CLUTTER |
PROPAGATION OF RADAR WAVES 443 assumes that h, ~ l,0. The phase difference .corresponding lo the path-length difference is (12.2) To this must be added the phase shift tjf, resulting from the reflection of the wave at M, which is assumed to be TC radians, or 180°. The total phase difference between the direct and the ground reflected signals as measured at the target is (12.3) Tile resultant of two signals, each of unity amplitude hut with phase difference t/1, is [ 2( I + cos 1/1 )J 111. |
CALLY FOCUSES THE MOVING TARGETS &IGURE A SHOWS A CONVENTIONALLY PROCESSED 3!2 IMAGE CONTAINING THREE MOVING TARGETSA MILITARY TRUCK TYPE - A TRACTOR |
Ó{°{{ 2!$!2 (!.$"//+ KM FROM THE RADAR 4HE TWO CIRCULAR TURNS ARE PERFORMED AT AN ACCELERATION OF G 4HE TRANSMITTED 3/* NOISE IMPACTS THE RADAR WITH POWER F NOT EXCEEDING EIGHT TIMES THE RECEIVER NOISE POWER 4HUS A 3/* WILL NOT COMPLETELY HIDE A TARGET AND IT CAN BE DEFEATED WITH A HIGHER ENERGY WAVEFORM )N 2'0/ THE TARGET UNDER TRACK REPEATS WITH DELAY AND AMPLIFICATION THE RADAR PULSE SO AS TO PULL THE RADAR RANGE GATE OFF THE TARGET 4HE TIME DELAY IS CONTROLLED SO THE FALSE TARGET IS SEPARATED FROM THE TRUE ONE WITH EITHER LINEAR OR QUADRATIC MOTION &OR THE LINEAR CASE THE RANGE OF THE FALSE TARGET 2 KFT IS RELATED TO THE RANGE OF THE TRUE TARGET 2KT VIA 22 V T TKKT KFT PO |
The am- plitude range for each plot is 60 dB. The peaks at zero-doppler frequency are due to land in an antenna sidelobe. The target doppler coincides with a resonant line at 4.93 Mhz; it is between the lines below that frequency and outside them for frequencies above. |
.. 25. Whelton, C. |
AVAVAVAVAVAVA FIG, 3 To summarize, therefore, the average radio circuit is handling wave~forms which can roughly be represented as in Fig. 3. The radar receiver and transmitter, how- ever, will be handling a square wave, such as is shawn . |
III, Fig. 21.41, p. 1856. |
Conf. HF Radio Systems and Techniques , July 1991, pp. 48–53. |
In addition, we can judge that the dihedral used in Gotcha experiment is set vertically because the RCS curve of it is the same as the curve of dihedral B in the simulation. The RCS curve of the vehicle is as expected. The four sides of the vehicle cause substantial scattering in four directions and barely any scattering in other directions. |
THE |
34!4% 42!.3-)44%23 ££°£Î -/#6$ FABRICATION TECHNIQUES TO ACHIEVE THE HIGH PERFORMANCE CHARACTERISTICS 4HESE ARE CAPITAL |
BIASED AMPLIFIER STAGE ARE AS FOLLOWS L .O QUIESCENT DC CURRENT IS DRAWN WHILE THE DEVICE IS NOT BEING DRIVEN SUCH AS IN THE RADAR RECEIVE MODE (ENCE THERE IS NO POWER DISSIPATION IN THE AMPLIFIER WHILE THE TRANSMITTER IS OPERATING IN THIS MODE L /NLY ONE POWER SUPPLY VOLTAGE IS NECESSARY FOR THE COLLECTOR TERMINAL OF THE TRANSIS |
(Available from DTI Internet site www.divtecs.com.) 53. K. J. |
In a valve it is customary to place the greatest positive potential on the plate, or anode—say, 150 or 100 volts, compared with only 100 or 120 on any intermediary grid—and the anode is relatively close to the cathode, so there is a heavier electron-flow, or, as we say, a-greater flow of anode current. By this we really mean a greater flow of electrons to the anode. In the CRT we use a considerably greater voltage on the electrodes corresponding to the valve anode, often as much as 3000 volts. |
= ^ P,,.G,,. An-(T0A A, Pr ~ 1 (*a*tf Here a° has been used to denote the average value of (j,/A A1-. In this formulation, we may pass in the limit from the finite sum to the integral given by __ i c PtGtArv*dA pr = -~ I -^-^-l 02.1)/4 \2 J r>4 ^ 7^ Illuminated area ^ The bar over Pr implies the average value. |
Airborne weather radars are constrained by size and weight limitations. Ground-based radars may be constrained by cost and siting considerations. Severe storm warning radars require long range and high unambigu - ous velocity and then must penetrate very heavy rain, thus dictating long wavelengths. |
It should be noted that radar cross sections of ships can be several thousand square meters, while those of tanks typ- ically range from 25 to 125 m2.17 For severe clutter and reduced target cross sections, coherent processing may be required. Although stationary or very slow-moving targets cannot be discrim- inated from clutter on the basis of doppler frequency, use of doppler beam sharp- ening or synthetic aperture techniques can reduce the effective size of the reso- lution cell and hence increase the signal-to-clutter ratio in the cell containing the target.18 Angle tracking can thus take place to provide the required data for guid- ance. Air Targets.4'16 Although some early systems were designed to use non- coherent pulse waveforms, they were not suitable for low-altitude (high-clutter) op- eration against small-cross-section aircraft targets. |
J. Farrell, J. Plaut, A. |
The setisfully described in Sec. 8“13ofVol. 2ofthis series.. |
The main operator controls included: Power-up push buttons (LT OFF, LT ON and HT ON) with associated indicator lamps; Lucero switch; Figure 3.8. Switch unit type 207 [ 4].Airborne Maritime Surveillance Radar, Volume 1 3-11. Scanner switch; Line of flight marker switch; 10 mile zero control; Range marker control; Height marker control; Range scale and range marker scale selection; Receiver gain. |
Rec., vol. 2, pt. 1, pp. |
62. pp 664 673. June, 1974. |
Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). 294. |
TIME FIG. 14.15 Schematic diagram for a sinusoidally modulated FM. FREQUENCY . |
E. O. Brigham, The Fast Fourier Transform , New York: Prentice Hall, 1974, pp. |
$ $ |
Then, when we turn the. aerial array towards an object giving an echo, we shall see the spike blip of light on the CRT standing out above the grass, and thus again we can measure the length of this echo. The two measure- ments can be compared as a ratio, and this ratio of signal deflection (echo-length) to the mean noise-level is called the S/N ratio, or the ‘Z factor.” Thus the limit of reception on any given radar set is when the Z factor = 1, for then the greatest echo is no longer than the average depth of grass. |
FICIENT FOR TARGET DETECTION EVEN THOUGH THE 3#6 OF THE RADAR BASED ON AVERAGE CLUTTER MAY BE RELATIVELY LOW 4O ACHIEVE )#6 A MECHANISM MUST BE FURNISHED TO PROVIDE #&!2 OPERATION AGAINST THE RESIDUE FROM STRONG CLUTTER 4HIS #&!2 IS PROVIDED IN OLDER -4) SYSTEM BY )& LIMITING AND IN THE -4$ IMPLEMENTATION THROUGH THE USE OF HIGH |
AND THE ,UNAR 2ECONNAISSANCE /RBITER ,2/ INCLUDE IN EACH OF THEIR PAYLOADS A h-INI |
Usually the pulser canbemore easily modified than themagnetron ifmode-shifting ormode- jumping occurs. Inany event, many interacting adjustments must be made before full power output can beassured. Sometimes achange in ther-floading ofthemagnetron, injtsheater current, orintheshape of the magnetic field will succeed ~vhere altering thepulse shape has failed. |
Speckle Filtering in Satellite SAR Change Detection Imagery. Int. J. |
13ofthisseries.. 156 C-W RADAR SYSTEMS [SEC. 5.11 inaddition tothose atOand 1000 cps. |
Thinned Arrays. The number of radiating elements in an array may be reduced to a fraction of those needed completely to fill the aperture without suffering serious degradation in the shape of the main beam. However, average sidelobes are degraded in proportion to the number of elements removed. |
FLIGHT IS UNCHANGED BY THIS SUBSTITUTION $AVIES PROVIDES A CLEAR EXPLANATION OF THESE USEFUL THEOREMS. |
39. Wilson, J. D.: Probability of Detecting Aircraft Targets, IEEE Trans., vol. |
● The development of radars suitable for air-traffic control. ● Pulse compression. ● Monopulse tracking radar with good tracking accuracy and better resistance to elec - tronic countermeasures than prior tracking radars. |
FED REFLECTOR WITH TRIPOD STRUTS SIDE VIEW AND AXIAL VIEW. |
17 Examples of the variation with angle of incidence of the number of independent samples for a scatterometer ch16.indd 25 12/19/07 4:55:50 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. Ground Echo. |
ON ASPECT LIES AT n AT BOTH SIDES OF THE CHART !S SHOWN IN 4ABLE THE APPROXIMATE 2#3 OF A STRAIGHT EDGE OF LENGTH , PRE |
The photomixing receiver is more complicated than the direct photodetection receiver and it requires a stable transmitter and local oscillator. When the target is in motion relative to the radar a large doppler frequency shift occurs which can place the echo signal outside the receiver passband. For example, with a relative velocity of 5 m/s ( 10 kt) the doppler rrequency shift at l-1,m wavelength is 10 MHz. |
Equation (8.29) indicates an error of 0.22 x 10-4 radian ( -0.001°) for a 100-by-100-element uniformly illuminated array with a beam width of approximately 1 ° when a = 0.4. 320 INTRODUCTION TO RADAR SYSTEMS Leichter's analysis 111 of beam-pointing errors was performed for a continuous line source, but may be applied to a linear array. Both uniform distributions and modified Taylor distributions were considered. |
For most areas, little difference was found between vertical and horizontal polarizations, so the results were reported for data groups including both polarizations. Figure 16.48 shows the results, grouped by target class.FIGURE 16. 47 Phase differences for different surface classes in the Amazon basin at C band and L band179 CHH-CVV Phase Differences LHH-LVV Phase DifferencesWater Clearing Macrophyte Fores t Flooded forest Water Clearing Macrophyte Fores t Flooded forest0 90 270 180 0.20 90 270 180 0.20 90 270 180 0.20 90 270 180 0.20 90 270 180 0.2 0 90 270 180 0.20 90 270 180 0.20 90 270 180 0.20 90 270 180 0.20 90 270 180 0.2 ch16.indd 53 12/19/07 4:56:47 PMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2008 The McGraw-Hill Companies. |
ENCES INCLUDE ADAPTATION TO ENVIRONMENT FREQUENCY AND WAVEFORM SELECTION RADAR CROSS SECTION PATH LOSSES MULTIPATH EFFECTS NOISE INTERFERENCE ANTENNA GAIN SPATIAL RESOLUTION AND CLUTTER &OR THE CASE OF NOISE |
Thesering-angels areassociated withbirdsflyingawayfromroostingareas.Angelscanalsobe causedbysecond-time-around echoesorlargesignalsthatentertheradarviatheantenna sidelobes. REFERENCES 1.Skolnik, M.I.:SeaEcho,chap.26of"Radar Handbook," M.I.Skolnik (ed.)McGraw-Hili Book Company, NewYork,1970. 2.Guinard, N.W.,J.T.Ransone, Jr.,andJ.C.Daley:Variation oftheNRCSoftheSeawithIncreasing Roughness, J.Geophys. |
ING LESS LINES OF CODE THE *6# ALGORITHM GENERALLY REQUIRES LESS COMPUTATION TIME 0ROBABILISTIC $ATA !SSOCIATION 0$! !NOTHER ALTERNATIVE IS THE PROBABILISTIC DATA ASSOCIATION 0$! ALGORITHM WHERE NO ATTEMPT IS MADE TO ASSIGN TRACKS TO DETECTIONS BUT INSTEAD TRACKS ARE UPDATED WITH ALL THE NEARBY DETECTIONSWEIGHTED BY THE PERCEIVED PROBABILITY OF THE TRACK BEING THE CORRECT ASSOCIATION "ECAUSE 0$! RELIES ON ERRONEOUS ASSOCIATIONS ESSENTIALLY hAVERAGING OUT v IT IS MOST EFFECTIVE WHEN TRACKS ARE FAR ENOUGH APART THAT NEARBY DETECTIONS ORIGINATE FROM SPATIALLY RANDOM NOISE OR CLUTTER EXCLUSIVELY AND WHEN THE TRACKING GAINS ARE SMALL IE WHEN THE TRACKING INDEX F TRACK IS SMALL 4HE *OINT 0ROBABILISTIC $ATA 4RACK .O $ETECTION .O $ETECTION .O $ETECTION .O c cc FROM ' 6 4RUNK 4!",% !SSOCIATION 4ABLE FOR %XAMPLE 3HOWN IN &IGURE . Ç°{ä 2!$!2 (!.$"//+ !SSOCIATION *0$! IS AN EXTENSION OF 0$! THAT HANDLES MORE CLOSELY SPACED TARGETS )N *0$! DETECTIONS ARE WEIGHTED LESS WHEN THEY ARE NEAR ANOTHER TRACK -ULTIPLE (YPOTHESIS !LGORITHMS 4HE MOST SOPHISTICATED ALGORITHMS ARE MULTIPLE HYPOTHESIS ALGORITHMS IN WHICH ALL OR MANY POSSIBLE TRACKS ARE FORMED AND UPDATED WITH EACH POSSIBLE DETECTION )N 4ABLE TRACK NO WOULD BECOME THREE TRACKS OR HYPOTHESES CORRESPONDING TO UPDATING WITH DETECTION NO DETECTION NO AND NO DETECTION %ACH OF THESE TRACKS WOULD UNDERGO A +ALMAN FILTER UPDATE AND BE ELIGIBLE FOR ASSOCIATION WITH THE NEXT SET OF DETECTIONS 4RACKS ARE PRUNED AWAY IN A SYSTEMATIC MANNER LEAVING ONLY THE MOST PROBABLE &IGURE ILLUS |
D" WINDOW OF 2& INPUT DRIVE 4HIS BECOMES STRIKINGLY CRITICAL WHEN SEVERAL #LASS |
40. 130 ._____e• ,,-I~--c=- till 100Figure13.14Radarcrosssectionorbirds (withclosedwings)atSband.Vertical polarization. Solidcirclesapplytoaverage values*20°aroundbroadside, x'sapplyto theaVl"rap.{' orthe±20°sectoraboutthe headandthe±20°sectoraboutthetail. |
J. P. Hansen, “High resolution radar backscatter from a rain disturbed sea surface,” presented at ISNR-84 Rec., Tokyo, October 22–24, 1984. |
Equation 8.3 applies to isotropic radiating elements, but practical antenna elements that are designed to maximize the radiation at O = 0°, generally have negligible radiation in the direc tion O = ± 90°. Thus the effect of a realistic element patt~rn is to suppress the grating lobes at ± 90',. It is for this reason that an element spacing equal to one wavelength can be tolerated for a nonscanning array. |
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