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The Effects of Phase Errors on DEM Accuracy With reference to Equations (25), (26) and (28), we can derive the relationship between DEM accuracyσhand the above two types of phase error: σh=λRsp 4πΔz⎭parenleftBig⎭vextendsingle⎭vextendsingle⎭vextendsingleσps⎭vextendsingle⎭vextendsingle⎭vextendsingle+⎭vextendsingle⎭vextendsingle⎭vextendsingleσpd⎭vextendsingle⎭vextendsingle⎭vextendsingle⎭parenrightBig (34) According to Equation (34), Figures 13and 15,t h e h–σhcurve can be obtained, as shown in Figure 16. 144. Sensors 2019 ,19, 2921 Figure 16. |
Direction finder, reconnaissance and surveillance D. Pilotless carrier S. Special or combinationG. |
§ ©¨¶ ¸· |
Even so, the pulse-doppler radar has an advantaee over the CW radar in that the detection performance is not limited by transmitter leakage or by signals reflected from nearby clutter or from the radome. The pulse-doppler radar avoids this difficulty since its receiver is turned off during transmission, whereas the CW radar receiver 1s always on. On the other hand, the detection capability of the pulse-doppler radar is rcd~~~cd because of the blind spots in range resulting from the high prf. |
The 130 kW outputs of the two 56:1 combiners were combined in a single 2:1 isolated hybrid that was manufactured by using a coaxial transmission line. The advertised losses of the 2:1 and 56:1 combiners were 0.1 dB and 0.25 dB, respectively . RAMP (L-Band Air Traffic Control Transmitter). |
1352.- 1356, November, 1954. 27. Andreasen. |
SION LIKE #2) WHEREAS 3,# COMBATS THE CONTINUOUS .,) !S PREVIOUSLY STATED BOTH TECHNIQUES COMBAT THE INTERFERENCES IMPINGING ON THE MAIN ANTENNA SIDELOBES 4HE TWO TECHNIQUES CAN BE JOINTLY USED AGAINST THE SIMULTANEOUS PRESENCE OF #2) AND .,) !N APPROACH IS TO CASCADE THE 3,# AND 3," TECHNIQUES AS SHOWN I N &IGURE 4HE SCHEME DEPICTS THREE RECEIVING CHANNELS EACH ONE HAVING AN ANTENNA A RECEIVER AND AN !$# THEY PROVIDE THREE SIGNALS LABELED RESPECTIVELY AS 3,# -!). AND 3," 4HE LEFT |
The graph is normalized to radar beamwidth on both axes for convenient use with a wide vari - ety of radars. The dashed portions of the curves are regions of uncertainty because of significant variations of reflection for a given sea state. In the intermediate region, the error increases to a peak at target elevations of about 0.3 beamwidth. |
TERISTICS OVER TIME AND SPACE WHEREAS OTHERS HAVE A RANDOM POLARIZATION 4HIS OCCURS AS FOR SUNLIGHT WHEN THE POLARIZATION ELLIPSE CHANGES ITS PROPERTIES RANDOMLY AND RAPIDLY WITH TIME OR WITH SMALL DIFFERENCES IN ANGLE 7HEN BOTH THE PERSISTENT AND RANDOM PARTS &)'52% -EASUREMENT |
RANGE DETECTION OF BALLISTIC MISSILES THE RADAR WILL MOST LIKELY HAVE SUFFICIENT POWER TO DETECT OTHER TARGETS ! CLUSTER OF MULTIPLE SIMUL |
ANE-1, no. 2, pp. 3-7, June, 1954. |
Since all de-operated CFAs use cold cathodes, no current can flow until RF drive is applied. With linear-beam tubes, beam current must be well enough cut off to keep noise output (and amplified input signals) small enough. Despite the nearly 200 dB between typical RF peak power output and typical receiver noise levels, most RF tubes readily meet the interpulse-noise requirements. |
TRACK POSITION OF THE MINIMUM |
Wide-angle SAR imaging. Proc. SPIE 2004 ,5427 , 164–175. |
When a shaped beam is desired in a surveillance radar, such as a cosecant-squared pattern, again it is more important to achieve the overall pattern required rather than simply max'imize the directivity at the peak of the beam. Aperture efficiency is a measure of the radiation intensity only at the center of the beam. In a search radar, however, the radiation intensity throughout the entire beam is of interest, not just that at the beam center. |
PENDENT -ONTE #ARLO SIMULATIONS 4HE TARGET 3.2 IS D" THE *.2 IS D" THE TARGET $O! IS ASSUMED TO BE EVENLY DISTRIBUTED IN THE MAIN |
Figure 10. Maps show subsidence rate in Region 1 ( a), and a subsidence profile passing through stations A and B ( b). Wuhan city’s urban construction has entered into a stage of rapid growth during our study period 2015 −2018. |
A line source such as a linear array, rather than a point source, must be used to feed the parabolic cylinder. The beam width in the plane containing the linear feed is Parabolic surface ,. Vertex 1-----------"----+---- or apex _.,,,,,.-· Focus 1 --------~ I I I Beam axis Figure 7.6 Parabolic-reflector antenna. |
A.: Computer Control of Array Radar, Sperrr Enqineeriny Reriew. vol. 18, No. |
) The usefulness ofbeacons was demonstrated with theearly radar sets that were operated atlong wavelengths. Alarge proportion ofthe beacons used inthe war operated atfrequencies about 200 Me/see. These included the beacons used with ASV Mark IIsearch radar, the transponders used foridentification, the portable Eureka beacons that were part ofthe independent Rebecca-Eureka beacon system, and a much-used system for precise bombing, the Oboe Mark I.Another system forprecise bombing, the Gee-H system, used beacons ofeven lower frequency. |
fa 1slfa+fc2d(aL¢ mixer mixer Delay TfcL¢ fcFigure8.19Schematic representation oftheHuggins phaseshifter. Fixed fo fo+fefrequency Mixer Delayline oscillator fe Variable fefrequency oscillator Figure8.20Huggins phaseshift ingappliedtoalineararrayfeed.. I 11E lil.FC1 RONI('AI.1.Y SFFERED t'llASED ARRAY ANTENNA IN RADAR 305 line, as illustrated in Fig. |
The entropies and IC values convergence of two sub-images versus the number of iterations. (a) Entropies change of the two sub-images during iteration; ( b) IC values change of the two sub-images during iteration. (a) (b) (c) Figure 19. |
#&!2 PROCESSOR FOLLOWING THE -4) FILTER WILL USUALLY PROVIDE GOOD SUPPRESSION OF THE CLUTTER RESIDUES 3PECIAL FEATURES ARE SOMETIMES ADDED TO THE #! |
- 7HEREAS PHASED ARRAY ANTENNAS ARE FREQUENTLY CHOSEN FOR RADAR SYSTEM DESIGNS REFLEC |
The swath Sw is often much smaller than the maximum range so that the prf can be increased to allow the umambiguous range Ru to encompass ft1e distance S,.. cos 1/1. where 1/1 is the grazing angle. |
SWATH 3CAN3!2 IMAGERY 4HE DIRECTION OF FLIGHT IS VERTICAL IN THIS PRESENTATION NEAR |
587–588, 2006. 55. D. |
. Radar System Engineering Chapter 10 – Characteristics of Radar Target s 111 Figure 11.18 Exam ple for the optimization of the shape. The requirements, which are similar to those of good aerodynamics, were particularly realized with reconnaissance airplanes. |
OE-Il, April 1986. 7. Kolosov, A. |
TO |
SEC. 13.9] ELECTRONIC SWITCHES 505 input ofthecircuit, thetime elapsing before anoutput signal appears is proportional tothebias applied tothediode, thus providing anaccurate and easily controllable time delay (see Sec. 13.12). |
(1)will beused only forthe relationships itestablishes among thesystem parameters. 15-5. Choice ofPulse Length.-The pulse length isconvenient for first consideration since itsrelations with the other parameters are relatively simple. |
2 was the average value of the power over the duration of a pulse of sine wave. The ratio R , is twice the average signal-to-noise power ratio when the input signal s(t) is a rectangular sine-wave pulse.] The output voltage of a filter with frequency-response function H( f) is where S(f) is the Fourier transform of the input (received) signal. The mean output noise power is where No is the input noise power per unit bandwidth. |
cc £ #OMB OPERATOR COMB& N8F 8N & F N &; = |
B. Colegrove and J. K. |
Figure 16.1 lib shows a method of correcting for the phase advance -n. An ide- alized correction signal Ec is applied, leading the received signal by 90° and lag- ging the next received signal by 90°. For exact compensation the following rela- tion would hold: 2^7; sin 0Ec = E1 tan -q = 22(0) tan (16.9)A This assumes a two-lobe antenna pattern similar to that in a monopulse tracking radar. |
TICS OF THE WEATHER TARGETS 4RANSMITTING THE TWO ORTHOGONAL POLARIZATIONS EITHER SIMULTANEOUSLY 3(6 OR TRANSMITTING THEM SEPARATELY IN A PREDETERMINED SEQUENCE AND USING DUAL PARALLEL DIGITAL RECEIVERS ONE ON EACH POLARIZATION CHANNEL ALLOW ESTI |
Thetransistor amplifier canbeappliedovermostoftheentirerangeoffrequencies ofinter esttoradar.,o.'9.2o Thesiliconbipolar-transistor hasbeenusedatthelowerradarfrequencies (helowLhand)andthegaliumarsenide field-elTect transistor (GaAsFET)ispreferred atthe 60 CD "0<'10 ~ ::>0' <1J30-- 1/1 <5z 20 10- 5000 10,000 Frequency -MHz30,000 Figure9.4Noisefiguresoftypicalmicrowave receiverfront-ends asafunctionoffrequency-. higher frequencies. The transistor is generally used in a multistage config~~ration with a typical gain per stage decreasing from 12 dB at VHF to 6 dB at K, band." In the GaAs FET, the thermal noise contribution is greater than the shot noise. |
G. Morris, Airborne Pulse Doppler Radar , Norwood, MA: Artech House, 1988. 66. |
Technol ., vol. 24, pp. 791–805, 2007. |
SCAN USING -(Z CENTER FREQUENCY #OURTESY )%% |
Theuniquecharacteristics ofanarrayantenna offertheradarsystems designer capabili tiesnotavailable withothertechniques. Aswithanyotherdevice,thearraywillseemajor application whenitcanperform someradarfunction cheaper thananyotherantenna typeor whenitcandosomething nOlpractical byothermeans. REFERENCES I.Southworth, G.c.:"Forty YearsofRadioResearch," Gordon andBreach. |
87, pp. 717–737, May 1999. 25. |
Turner “An ‘entraining plume’ model of a spilling breaker,” J. Fluid Mech ., vol. 63, pp. |
78. P. Vincent, N. |
and J.W.; Resources, Y.L. (Yanfang Liu); Data Curation, M.J., Y.L. (Yanfang Liu) and J.W.; Writing—Original Draft Preparation, Y.Z.; Writing—Review & Editing, Y.J., Y.L. |
ALARM |
5.11 abalanced one — ---ml FIG. 5.13.—The AN/APN-l frequency-modulated radar altimeter, (Reprinted from Electronic-s.) (see Vol. 24) with the result that, ifthe balance isgood, amplitude modulation from the transmitter balances out inthe detector output. |
Note that for a rectan - gular pulse, Pt is either zero or the peak transmitter power; but for other pulse shapes, the variation with t (or R) is significant. Actual pulses are often approximated by rectangular pulses with widths equal to their half-power widths. Real pulses cannot be rectangular after passing through real transmitter, antenna, and receiver bandwidths. |
CLEAR DETECTION REQUIREMENTS FOR SUCH RADARS ARE NOT PARTICULARLY DEMANDING !N PROBABILITY OF DETECTION AND A PROBABILITY OF FALSE ALARM OF n IS SPECIFIED BY )-/ AS SHOWN IN 4ABLE 4AKING INTO ACCOUNT ALL PERFORMANCE REQUIREMENTS TYPICAL COMPLIANT SYSTEMS FOR COMMERCIAL VESSELS HAVE PEAK TRANSMIT POWERS OF n K7 THE LOWER POWERS BEING CONFINED TO '(Z SYSTEMS !NTENNA GAINS FROM TO D" ARE TYPICAL WITH ASSOCI |
,*, |
MS DELAY ARE THE NOISE POWERS IN DECIBELS BELOW 7(Z &OR THIS PLOT THE 54# TIME IS 33. 0 AV K7 'T'R D" 4 S AND R D"SM &IGURE GIVES THE CORRESPONDING NIGHT PLOT 4HE SHAPE OF THESE DISPLAYS IS QUITE SIMILAR TO WHAT WOULD BE SEEN WITH A DIAGNOSTIC OBLIQUE SOUNDING THE LEVELS WOULD GENERALLY BE GREATER BECAUSE THE RESOLUTION CELL AREA TIMES THE SURFACE SCATTERING COEFFICIENT IS GENERALLY MUCH LARGER THAN D"SM 3OME OF THE NIGHT |
The outputs of the two feeds are combined using a hybrid junction to produce a sum pattern C and a difference pattern A. By taking C Ifl jkA, the effective phase center can be shifted depending on the value of k. (The factor j multiplying the difference pattern signifies a 90" phase shift added to the difference signal relative to the sum signal.) The use of this technique in an AMTI radar to compensate for the effects of platform motion is called DPCA, which stands for Displaced Phase Center Anter~nn. |
As a result, the calculated tracking accuracy is (at least to third order) uncontaminated (or “unscented”) by the nonlinearity . Adapting Filter to Deal with Changes in Target Motion. The Kalman filter assumes linear target motion perturbed by a random maneuver model as a mathemati - cal convenience in calculating tracking gains. |
Kilowatts of CW power can be obtained in the vicinity of I-rnnl wavelength and several tens of kilowatts at 3-mm wa~elength.~~ Over a megawatt of pulse power is clairiled at 3-~nrn wavelength. Millimeter-wave gyrotrolls require extremely high voltages (the electrons travel at relativistic velocities) and superconducting magnets. Receivers with mixer front-ends using Schottky-barrier diodes at room temperature have den~onstrhted respectable noise figures. |
For example, the database cannot contain the height of wires strung between towers or structures erected since the database was prepared. For the lowest possible flight profiles with less than 10–6 probability of crash per mission, the prestored data is merged and verified with active radar measurements. Low crash probabilities may also require some hardware and software redundancy. |
(1), but theperformance figure remains ofvital importance in determining what fraction ofthe maximum radar range canberealized byagiven system against agiven type oftarget, regardless ofthe existing propagation conditions. TheInadequacy ofGuessing Per- formance.—It hasoften been wrongly assumed that over-all radar perform- ance can beadequately judged with- out using test equipment bymeans ofone ofthe following “rule-of- thumb” criteria: (1) the general appearance ofthe picture seen on the radar indicator, (2)the maxi-oo- Dechisbelowratedperformance FIG. 15.1.—Relation between radar performance deficit and available radar range for various types oftarget. |
Mitchell et al.52 describe basic performance limitations of the AN/FPQ-6 high precision tracking radar measured under ideal Component Bias Noise Radar-dependent tracking errors (deviation of antenna from target)Boresight axis collimation Axis shift with RF and IF tuning Receiver phase shift Target amplitude Temperature Wind force Antenna unbalance Servo unbalance Receiver thermal noise Multipath (elevation only) Wind gusts Servo electrical noise Servo mechanical noise Radar-dependent translation errors (errors in converting antenna position to angular coordinates)Leveling of pedestal North alignment Static flexure of pedestal and antenna Orthogonality of axes solar heatingDynamic deflection of pedestal and antenna Bearing wobble Data gear nonlinearity and backlash Data takeoff nonlinearity and granularity Target-dependent tracking errorsDynamic lag Glint Dynamic lag variation Scintillation Beacon modulation Propagation errors Average refraction of troposphere Average refraction of ionosphereIrregularities in tropospheric refraction Irregularities in ionospheric refraction Apparent or instrumentation errors (for optical reference)Telescope or reference instrument stability Film emulsion and base stability Optical parallaxTelescope, camera, or reference instrument vibration Film-transport jitter Reading error Granularity error Variation in optical parallax * From D. K. Barton in “Modern Radar,” R. |
J. McLaughlin, E. Boltniew, Y . |
VERTER FOR DISPLAY ON A 00) 4HE DIGITAL SIGNAL MAY ALSO BE SENT TO AUTOMATIC TARGET DETECTION CIRCUITRY 4HE DYNAMIC RANGE PEAK SIGNAL TO RMS NOISE IS LIMITED TO ABOUT D" FOR A 00) DISPLAY ! KEY DISTINCTION SOMETIMES LOST IN THE COMPLEXITIES OF THE SYSTEMS THAT FOLLOW IS THAT AN -4) RADAR SYSTEM ELIMINATES FIXED CLUTTER BECAUSE THE PHASE OF SIGNALS RETURNED FROM CONSECUTIVE TRANSMITTED PULSES DO NOT APPRECIABLY CHANGE 4HE FIXED CLUTTER IS REMOVED AFTER AS FEW AS TWO TRANSMITTED PULSES BY THE SUBTRACTION PROCESS DESCRIBED &)'52% "IPOLAR VIDEO RETURN FROM SINGLE TRANSMITTER PULSE &)'52% "IPOLAR VIDEO FROM CONSECUTIVE TRANSMITTED PULSES . |
INGS OIL FILLING OR ENCAPSULATION #OMPARED WITH A HIGH |
November, 1960. 276 INTRODUCTION TO RADAR SYSTEMS 83. van der Maas, G. |
C O S |
Inaspeechdelivered beforetheInstitute ofRadio Engineers, hesaid:3 AswasfirstshownbyHertz,electricwavescanbecompletely reflected byconducting bodies.In someofinytestsJhavenoticedtheeffectsofreflection anddetection ofthesewavesbymetallic objectsmilesaway. It~eemstomethatitshouldbepossibletodesignapparatus bymeansofwhichashipcould. THE NATURE OF RADAR 9 radiate or project a divergent beam of these rays in any desired direction, which rays, if coming across a metallic object, such as another steamer or ship, would be reflected back to a receiver screened from the local transmitter on the sending ship, and thereby, immediately reveal the presence and bearing of the other ship in fog or thick weather. |
Lewis, F. F. Kretschmer, and W. |
Theenergyscattered inthedirection oftheradarisof primeinterest. Therelative phasesandamplitudes oftheechosignalsfromtheindividual scattering objectsasmeasured attheradarreceiver determine thetotalcrosssection.The phasesandamplitudes oftheindividual signalsmightaddtogivealargetotalcrosssection,or therelationships withoneanothermightresultintotalcancellation. Ingeneral, thebehavior is somewhere b~tween totalreinforcement andtotalcancellation. |
(Yun Lin) and Y.S. performed the experiments and analysis. Y.W. |
TARGET NO.LOST TARGETS Ts (s) Tave (s) PM (W)POS ERR (m)VEL ERR (m/s) 1 0 1.958 0.5106 10–3 5.7985 116.8 65.26 5 1 0.6772 1.477 10–368.898 95.39 61.29 6 1 1.112 0.899 10–310.774 82.94 58.43TABLE 24.2 Simulation Results Without ECM TABLE 24.3 Simulation Results With SOJ and Without A-SOJ TARGET NO.LOST TARGETS Ts (s) Tave (s) PM (W)POS ERR (m)VEL ERR (m/s) 1 34 1.919 0.521 10–3 6.6179 127.5 71.09 5 15 0.6923 1.444 10–368.411 103 66.78 6 50 ch24.indd 47 12/19/07 6:01:11 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. Electronic Counter-Countermeasures. |
3.Whether the signals areadded atradio frequency orintermediate frequency.. 636 MOVING-TARGET INDICATION [SEC. 16.4 EEl EEl1 ITransmitter TR ‘Echosignal Reference signal Locking IStabler.f oscillatortrlMixer At tITransmitter TR( Echosignal -%=LO Mixer Receiver (a) (b) FIG. |
SHAPED SPECTRA AND SEPARATES THESE TWO COMPONENTS OF THE DOPPLER SPECTRUM USING DIGITAL SEARCH ALGORITHMS AND THEN REMOVES THESE CLUTTER COMPONENTS WHILE LEAV |
SION OF (ALL AND 3HRADER THAT USING AN - OUT OF . BINARY DETECTOR AT THE OUTPUT OF AN -4) FILTER WILL PRECLUDE FALSE ALARMS FROM THE CLUTTER RESIDUES CAUSED BY LIMITING &IGURE SHOWS IN ADDITION TO CLUTTER RESIDUE THE RETURNS FROM A TARGET THAT WAS SUPERIMPOSED ON THE DISTRIBUTED CLUTTER PRIOR TO THE CLUTTER |
2. Concept of Aspect Entropy Because the scattering of a target is aspect dependent, CSAR is helpful in detecting the anisotropic scattering behavior of a target. Radar cross section (RCS) is a measure representing the scattering ability of the incident electromagnetic wave [ 16]. |
ch11.indd 3 12/17/07 2:25:23 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. Solid-State Transmitters. |
Skaggs, and J. Lloyd, “A global ionospheric model,” Naval Res. Lab. |
OR HIGH |
38. M. Cicolani, A. |
8.4b does not have this problem. In the parallel-fed array of Fig. 8.2, the energy to be radiated is divided between the elements by a power splitter. |
Manasse, R., R. Price, and R. .M. |
Schultz, B. H. Gere, and F. |
Moisture in the atmosphere at altitudes where the temperature is below freezing takes the form of ice crystals, snow, or hail. As these parlicks fall to the ground they melt and change to rain in the warmer environment of the lower altitudes. When this occurs, there is an increase in the radar backscatter since water particles reflect more strongly than ice. |
FIELD POWER DENSITY OF A CURRENT ELEMENT RADIATING INTO A LOSSLESS MATERIAL OF DIELECTRIC CONSTANT OF |
The received echo is processed in the receiver by a compression filter. The compression filter readjusts the relative phases of the frequency components so that a narrow or compressed pulse is again produced. The pulse compression ratio is the ratio of the width of the ex- panded pulse to that of the compressed pulse. |
Figure 12.1 illustrates that energy radiated from the radar antenna arrives at the target via two separate paths. One is the direct path from radar to the target; the other is the path reflected from the surface of the earth. The echo signal reradiated by the target arrives back at the radar via the same two paths. |
t 13. pp. 405-412, March, 1966. |
13.26, and broader-band operation is possible. ch13.indd 39 12/17/07 2:40:42 PMDownloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2008 The McGraw-Hill Companies. All rights reserved. |
ABSORBENT MATERIAL ABOUT THE ANTENNA STRUCTURE THE USE OF A FENCE ON GROUND INSTALLATIONS AND THE USE OF POLARIZATION SCREENS AND REFLECTORS 4HIS MEANS THAT VERY LOW SIDELOBE ANTENNAS ARE COSTLY IN TERMS OF SIZE AND COMPLEXITY WHEN COMPARED WITH CONVENTIONAL ANTENNAS OF SIMILAR GAIN AND BEAMWIDTH CHARACTERISTICS 3ECOND AS THE DESIGN SIDELOBES ARE PUSHED LOWER AND LOWER A POINT IS REACHED WHERE . %,%#42/.)# #/5.4%2 |
&)'52% 3AMPLED PHASE NOISE SPECTRUM DUE TO PHASE NOISE ALIASING |
Transmitters are generally in the form of high-powered, coherent transmitting tubes or solid-state amplifiers. At the University of Kyoto, Japan, the antenna-transmitter system consists of 475 crossed Yagi radiating elements, each with its own solid-state transmitter.185 This approach allows for very flexible electronic scanning of the beam. NOAA operates a net - work of over thirty 404 and 449 MHz wind profilers in the central United States using solid-state transmitters that supply continuous wind profiles up to 20 km for improved weather forecasts and current upper air wind information for aviation applications.186 It is important to recognize that three-beam doppler systems can accurately measure horizontal winds in all three velocity components if the wind is uniform. |
BORNE 3!2S BECAUSE IT LEADS TO AZIMUTH AMBI |
FREE DYNAMIC RANGE 3&$2 AND 3.2 OVER CONVENTIONAL .YQUIST CONVERTERS WHERE TIGHT TOLERANCES ARE REQUIRED TO ACHIEVE VERY LOW SPURIOUS PERFORMANCE $IGITAL FILTERING AND DECIMATION IS REQUIRED TO PRODUCE DATA RATES THAT CAN BE HANDLED BY CONVENTIONAL PROCESSORS 4HIS FUNCTION IS EITHER PERFORMED AS AN INTEGRAL PART OF THE !$ CONVERTER FUNCTION OR CAN BE INTEGRATED INTO THE DIGITAL DOWNCONVERSION FUNCTION USED TO GENERATE DIGITAL ) AND 1 DATA AS DESCRIBED IN 3ECTION 0ERFORMANCE #HARACTERISTICS 4HE PRIMARY PERFORMANCE CHARACTERISTICS OF !$ CONVERTERS ARE THE SAMPLE RATE OR USABLE BANDWIDTH AND RESOLUTION THE RANGE OVER WHICH THE SIGNALS CAN BE ACCURATELY DIGITIZED 4HE RESOLUTION I S LIMITED BY BOTH NOISE AND DISTORTION AND CAN BE DESCRIBED BY A VARIETY OF PARAMETERS 3AMPLE 2ATE 3AMPLING OF BAND |
Not many years ago the possibility of such a stop-watch would have been scoffed at by all serious thinkers. In a period of about fifty years radio, as we know it to-day, was developed; in various stages came the valve, the pulse transmitter, the cathode-ray tube CG . 34 HOW RADAR WORKS (which is now the basis of our electric stop-watch), and, finally, the radar system, which would have been just a piece of neat mathematics in Sir Robert Watson-Watt’s notebook, quite undemonstrable because we had no apparatus for measuring millionths of a second, but for the fact that when we discovered the precious secret of radar there was the electronic ‘stop-watch,’ ready for a whole new series of discoveries. |
and S. Weintraub: Tile Constants in tlie Equation for Atmospheric Refractive Index at Radio Frequencies. Pro(*. |
However, the notches are significantly wider than those of the elliptic filters; thus, they will have greater bias for measurement of weather intensity when the weather radial velocity is zero. For phased array radars, FIR filters similar to those described for the ASR-11 are applicable. The filters can be designed, if the time budget of the phased array radar allows, to utilize more than the five pulses per coherent processing interval (CPI) used by the ASR-11 radar. |
Atmos. Ocean. Technol ., vol. |
ITED TO THE CAPABILITY OF A SINGLE CHANNEL )N A DIGITAL BEAMFORMING SYSTEM THERE ARE MULTIPLE RECEIVERS AND !$#S AND THE NUMBER OF !$#S THAT ARE COMBINED DETERMINES THE SYSTEM DYNAMIC RANGE &OR EXAMPLE IF THE OUTPUTS OF !$#S WERE COMBINED TO FORM A BEAM ASSUMING THAT EACH !$# INDUCES NOISE THAT IS OF EQUAL AMPLITUDE AND UNCORRELATED WITH THE OTHERS THERE WOULD BE A D" INCREASE IN SYSTEM DYNAMIC RANGE COMPARED TO A SINGLE |
however, to operate withtheantenna beampointedeitherforward oraftofbroadside. Thi':iscalledthe sqliilltmode.Thesignalprocessor mustbemodified toaccount fortheaveragedoppler fre quencynotbeingzero.Recorders anddisplays mustbeldesigned toaccount fort11'.'geometry oftheoffsetbeam.Compensation mightalsobenecessary for"rangewalk,.whichistheresult ofthetarget,.walking" through oneormorerange-resolution cellsduringthetimeorobserva tion.Theachievable cross-range. oralong-track, resolution worsens asthesquintanglein creasesfrombroadside (c)cr~I/sin0,where0=anglebetween aircraftheading andsquinted antenna beamdirection). |
TER CANCELLATION OF MODERN RADAR SYSTEMS )N THIS CASE TRADITIONAL STATIC MEASURES SUCH AS DETECTION RANGE AGAINST A GIVEN TARGET WILL NO LONGER ADEQUATELY DEFINE THE CAPABILITIES OF RADAR SYSTEMS -EASURES OF RADAR DYNAMIC CHARACTERISTICS SUCH AS THE SUSCEPTIBILITY TO PROCESSOR OVERLOAD OR THE TIME TO ADAPT IN CHANGING CONDITIONS ARE MORE IMPORTANT -ODELING AND SIMULATIONS TO EVALUATE THE RADAR RESPONSE TO STANDARD |
A two-frequency MTI transmits a pair of pulses, either simultarieously or in close sequence, at two separate carrier frequencies. The two received signals are mixed in a nonlinear device and the difference frequency is extracted for normal MTI signal processing. Ttie advantage of tlle greater first blind speed obtained with the two-frequency MTI is accorrlpanied by several disadvat~tages.~~ If the ratio of the two frequencies is r < 1, the standard deviatiori of the clutter doppler spectrum a, for a single-frequency MTI is increased to n,(l t r.Z)"Z it1 a two-freqi~ency MTI. |
TO |