雷达系统大作业一汉译英1.线性调频信号2.二相编码信号3.侦察和监视雷达4.杂波抑制5.恒虚警检测6.合成孔径雷达7.干涉合成孔径雷达8.匹配滤波9.脉冲压缩10.多普勒滤波器组二英译汉1.RCS2.DPCA3.GMTI4.GMTD5.Discrete Fourier Transform6. in-phase and quadrature components7.PRF8. Doppler frequency of ground return9.Pulse compression10. Detection probability and the false-alarm probability三12选31The velocity of the airborne radar is 100m/s, the beamwidth of the radar is 3 deg.(constant for different look direction), the wavelength of the transmitted signal is 0.03m, compute the clutter Doppler bandwidth of the main beam for the following look direction: (a) 0 deg(relative to the velocity direction);(b) 30 deg(relative to the velocity direction);(c) 60 deg(relative to the velocity direction);If the radar antenna is a phased-array antenna, and the broadside of the antenna is parallel to the velocity direction, then compute the clutter Doppler bandwidth of the main beam for the following lookdirection(Assume that the beamwidth of the phased-array at 0 deg is 3 deg ): (a) 0 deg(relative to the velocity direction);(b) 30 deg(relative to the velocity direction);(c) 60 deg(relative to the velocity direction).2The moon as a radar target may be describe as followings: average8108443.?m (about 208,000 nmi); experimentallydistance to the moon is1126.64?10m(mean value over a range ofmeasured radar cross section is610?7381.m.radar frequencies); and its radius isWhat is the round-trip time (seconds) of a radar pulse to the moon and (a) back?What should the pulse repetition frequency (prf) be in order to have (b)no range ambiguities?For the purpose of probing the nature of the moon's surface, a much (c)higher prf could be used than that found in (b). How high could the prf beurpose is to observe the echoes from the moon's half?if the pIf an antenna with a diameter of 60 ft and aperture efficiency of 0.6 (d)were used at a frequency of 430MHz with a receiver having a minimum16?10?1.5Does is detectable signal of required? peak W, what power why?so，and if your answer surprise you；of sphere smooth perfectly conducting The radar cross section of a (e)2?a. What would be the radar cross section of the moon if itradius a iswere a sphere with a perfectly smooth．conducting surface?Why might the measured cross section of the moon(given above) be different from this value?3A radar mounted on all automobile is to be used to determine the distance aat operates radar The ．itof front in directly traveling vehicle a to frequency of 9375 MHz (Xband) with a pulse width of l0 ns(s)．Themaximum range is to be 500ft．8?10(a) What is the pulse repetition frequency that corresponds to a range of 500 ft?(b) What is the range resolution(meters)?(c) If the antenna beamwidth were ．what would be the cross-range?6resolution (meters) at a range of 500 ft ? Do you think this value of cross-range resolution is sufficient?(d) If the antenna dimensions were 1 ft by 1 ft and the antenna efficiency were 0.6,what would be the antenna gain (dB)?2m radar cross section Find the average power required to detect a10(e)vehicle at a range of 500 ft , if the minimum detectable signal is?13105?W.4(a) What signal-to-noise ratio is required for a radar that makes a detection on the basis of a single pulse,when the probability of detection is 0.50 and the probability of false alarm is ? Assume a 6?10nonfluctuating target echo.(b) Repeat for a 0.99 probability of detection and the same probability of false alarm.(c) Repeat parts(a) and(b),but for a Swerling Case 1 fluctuating target.(d) Compare your results in a table.What conclusions can you obtain from this?5A civil marine radar is employed on boats and ships for observing navigation buoys, detecting land-sea boundaries,piloting,and avoiding collisions.Consider the following civil-marine radar:Frequency : 9400MHz(X band)Antenna : horizontal beamwidth = ?.80Vertical beamwidth = ?15Gain = 33dBAzimuth rotation rate = 20rpmPeak power : 25kWPulse width : 0.15μsPulse repetition rate : 4000HzReceiver noise figure : 5dBReceiver bandwidth : 15MHzSystem losses : 12dBAverage time between false alarms : 4 hours(a) Plot the single-scan probability of detection as function of range (nmi),assuming a constant cross-section target of 10(a navigation buoy)and free-space propagation.[You will find it easier to select the2mprobability of detection and find the corresponding single-to-noise ratio,rather than the reverse.You need only consider probabilities of detection from 0.30 to 0.99.You may, for purposes of this problem, select a single (average) value of the integration improvement factor rather than P(since the curve in the text it find as a function of does not try to d permit otherwise).](b) Repeat (a) for a Swerling Case 1 target fluctuation model with average cross section of 10. Plot on the same diagram as (a).(c) Comment on whether the average power of this radar is too low, just 2mright, or too high for the job it has to perform here.(d) Why do you think this ship-mounted radar antenna has a15elevation beamwidth when all the targets are located on the surface of thesea?6Consider the following air-surveillance radar :Frequency : 2.8GHz(S band)Peak power : 1.4MWPulse width : 0.6μsPulse repetition rate : 1040HzReceiver noise figure : 4dBAntenna rotation rate : 12.8rpmAntenna gain : 33 dBAntenna azimuth beamwidth : 1.35 degSystem losses : 12dBAverage false-alarm time : 20 minTarget cross section :2 2m Plot each of the following on the samecoordinates (with range as theabscissa) :(a) The free-space single-scan probability of detection as a function of range (in nautical miles) for a constant cross-section target.[You will find it easier to select the probability of detection and find the corresponding single-to-noise ratio, rather than the reverse. You need only consider probabilities of detection from 0.30 to 0.99.You may, for purposes of this problem, select a single (average) value of the integration improvement P(since the curve in thefactor rather than try to find it as a function of dtext does not permit otherwise).](b) The probability of detection as a function of range for the same situation as part (a) but with the detection criterion that the target must be found on at least 2 out of 3 scans of the rotating antenna. [You may assume that the range and the received signal power do not change appreciably over the three scans. For convenience of this calculation, you may assume that the single-scan false-alarm probability is the same as used in part (a).](c) Repeat (a) for a Swerling Case 1 with average target cross section of2.(d) Repeat (b) for a Swerling Case 1 with average target cross section 2mof2.(e) Is the prf adequate for avoiding range ambiguities?2m(The radar in this problem is similar to the airport surveillance radar known as the ASR.)7(a) What is the probability of detecting a target on at least 2 out 4 scans when the single-scan probability of detection is 0.8?(b) What is the corresponding probability of false alarm in this case when 8?10?single-scan false-alarm probability isWhat should be the single-scan false-alarm probability if the overall (c)8?10? false-alarm probability with a detection criterion of 2 out 4 scans isWhen the higher single-scan probability of false alarm of part (c) is (d) 8?10single-scan probability of false alarm, what employed rather than areduction in the single-to-noise ratio can be obtained?8An S-band (3.1 GHz) air-surveillance radar utilizes a staggered waveform with four different prfs, which are 1222,1031,1138, and 1000Hz.What is the first blind speed (knots) if a constant prf is used which has (a)a pulse repetition period equal to the average of the four periods of the staggered waveform?What is the first blind speed (knots) of the staggered prf waveform? (b)n for these four frequencies are 27,32,29,33respectively. Note that the i(c) What is the maximum unambiguous range of the staggered prf waveform?(d) What is the depth (dB) of the first null of the staggered prf waveform?(e) What is the maximum MTI improvement factor for the staggered prf waveform, assuming a gaussian clutter spectrum with a standard deviation of 10Hz?9Consider an MTI radar with a frequency of 440MHz flying in an aircraft at a speed of 320kt. Its azimuth beamwidth is 6 degrees and its prf is 330Hz.(a) What is the Doppler frequency of the clutter echo and the spread in the clutter Doppler at azimuth angles of 0,45,and 90 degrees, where 0 is the head-on and 90 is the broadside? (You may assume that the elevation angle is zero, which is unrealistic of course, but it makes the problem simpler.)Assume that TACCAR is applied so that the Doppler clutter frequency (b)．is fully compensated along the center of the main beam (that is, the center frequency of the clutter Doppler spectrum is at zero Doppler frequency). DPCA is not applied. Sketch the Doppler space (the resulting clutter spectrum as a function of Doppler frequency) for the case where the radar antenna is pointing broadside at 90 degrees azimuth angle. For this?/2fΔis the same as . that(Drawassume problem you may c c approximately to scale along the frequency axis.)?/f when the antenna is pointing broadside(c) What is the value of pc?f= standard deviation of theas it is in part (b), where = prf andc p/2f clutter spectrum which can be approximated here by Δ?c(d) How well do you think a radar of this type detects moving aircraft targets in clutter?10Derive the error signal in one angle coordinate for theamplitude-comparison monopulse. Show that for small angular errors, the ??is the angle ,where of the target error signal is proportional to??measured from the antenna pointing direction. The angular separation ?[the one-way (voltage) squinted antenna beams is 2between the two?pattern of the two antenna beams when not squinted can be approximated22); where by the normalized gaussian function exp(,?2?a/22?/2.a776?B and is the half-power beamwidth. Note that the hyperbolic cosine can ?Bx?x)/e?e2x?( and the hyperbolic sine as be expressed as cosh sinhx?x; and for small values of x, sin x ≈x and cosh x ≈1. Also,2(e)?e/?x sinh 2x = 2sinh x cosh x.].11This problem involves range glint.(a) A dumbbell target at a long range from the radar has its two unresolved equal cross-section isotropic scatterers located in line in the radial (range) direction and separated by 10m. What is the phase different between the echoes from these two scatterers when viewed by a radar at a frequency of 3GHz ? What is the range glint error in this case ?(b) What change in aspect angle(such as might be caused by a rotation of target about its center) will cause the two echoes to be by out of?180phase , resulting is a severe glint error in range?(c) What change in frequency is needed to decorrelate the echo when the target is oriented as in (b) ?(d) What must be the pulse width [in (a)] in order to resolve the two scatterers (so that glint may be avoided)?12There are two methods for finding the radial velocity of a target. One is ?/vf?2; the other is based on the rate of based on the Doppler shiftrd change of range with time ΔR/Δt. They give different measurement accuracies.?v, found radial the velocity error,by for the What (a) is expressiond measuring the Doppler frequency shift of a long quasi-rectangular pulse of width and RF frequency ??f0．?v, found from (b) What is the expression for the radial velocity error,r RR and the rate of change of range based on two range measurements21separated by a time , so that the velocity is , and is ???/R)v?(R?12r the same as the pulse width of the Doppler measurements ? The pulses inthis range-rate measurement are of Gaussian shape with a half-power bandwidthB[use right-hand side of equation?1.18]. Assume the total value of ?NE/2?T?0R1/1/22?B(2E/NN.18(2E/))100in each of these two methods for radial velocity measurement [(a) and (b)]is the same.(c) What is the value of ???vv/rd(d) Based on your answer in (c), which is the more accurate method ofvelocity measurement, the Doppler method or the range-rate method ? (e) Under what conditions will these two methods give comparable accuracies (assuming the same total ) ?N/2E0(f) Why do you think the Doppler method has not been used very oftenfor a velocity measurement ?1 6 7 42 4 5 23 5 8 34 9 4 85 12 9 16 6 11 77 4 5 8 1211 1 89 1 2 610 6 7 411 5 10 1112 9 3 613 5 2 914 7 1 215 5 9 616 9 3 717 8 7 118 1 5 10 2 5 19 111 6 20 921 3 6 712 22 3 29 23 10 63 24 10 1 9 4 10 255 26 10 97 27 3 19 8 28 1110 5 29 44 3 11 3031 2 11 43 32 9 89 4 2 337 3 34 5 2 3 12 359 11 4 366 37 375 8 38 1239 4 10 8 610 5 40。