雷达系统大作业题目.doc

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 look direction(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).2 The moon as a radar target may be describe as followings: average distance to the moon is m (about 208,000 nmi); experimentally measured radar cross section is (mean value over a range of radar frequencies); and its radius is m.(a) What is the round-trip time (seconds) of a radar pulse to the moon and back?(b) What should the pulse repetition frequency (prf) be in order to have no range ambiguities?(c) For the purpose of probing the nature of the moons surface, a much higher prf could be used than that found in (b). How high could the prf be if the purpose is to observe the echoes from the moons half?(d) If an antenna with a diameter of 60 ft and aperture efficiency of 0.6 were used at a frequency of 430MHz with a receiver having a minimum detectable signal of W, what peak power is required? Does your answer surprise you；and if so，why?(e) The radar cross section of a smooth perfectly conducting sphere of radius a is . What would be the radar cross section of the moon if it were a sphere with a perfectly smoothconducting 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 to a vehicle traveling directly in front of itThe radar operates at a frequency of 9375 MHz (Xband) with a pulse width of l0 ns(s)The maximum range is to be 500ft(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 resolution (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)?(e) Find the average power required to detect a 10radar cross section vehicle at a range of 500 ft , if the minimum detectable signal is 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 nonfluctuating 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 = Vertical beamwidth = Gain = 33dB Azimuth rotation rate = 20rpm Peak power : 25kW Pulse width : 0.15s Pulse repetition rate : 4000Hz Receiver noise figure : 5dB Receiver bandwidth : 15MHz System losses : 12dB Average 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 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 factor rather than try to find it as a function of (since the curve in the text does not 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 right, or too high for the job it has to perform here.(d) Why do you think this ship-mounted radar antenna has a elevation beamwidth when all the targets are located on the surface of the sea?6Consider the following air-surveillance radar : Frequency : 2.8GHz(S band) Peak power : 1.4MW Pulse width : 0.6s Pulse repetition rate : 1040Hz Receiver noise figure : 4dB Antenna rotation rate : 12.8rpm Antenna gain : 33 dB Antenna azimuth beamwidth : 1.35 deg System losses : 12dB Average false-alarm time : 20 min Target cross section :2Plot each of the following on the same coordinates (with range as the abscissa) :(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 factor rather than try to find it as a function of (since the curve in the text 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 of 2.(d) Repeat (b) for a Swerling Case 1 with average target cross section of 2.(e) Is the prf adequate for avoiding range ambiguities?(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 single-scan false-alarm probability is ?(c) What should be the single-scan false-alarm probability if the overall false-alarm probability with a detection criterion of 2 out 4 scans is ?(d) When the higher single-scan probability of false alarm of part (c) is employed rather than a single-scan probability of false alarm, what reduction 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.(a) What is the first blind speed (knots) if a constant prf is used which has a pulse repetition period equal to the average of the four periods of the staggered waveform?(b) What is the first blind speed (knots) of the staggered prf waveform? Note that the for these four frequencies are 27,32,29,33respectively.(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.)(b) Assume that TACCAR is applied so that the Doppler clutter frequency 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 problem you may assume that is the same as . (Draw approximately to scale along the frequency axis.)(c) What is the value of when the antenna is pointing broadside as it is in part (b), where = prf and = standard deviation of the clutter spectrum which can be approximated here by ?(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 the amplitude-comparison monopulse. Show that for small angular errors, the error signal is proportional to ,where is the angle of the target measured from the antenna pointing direction. The angular separation between the two squinted antenna beams is 2the one-way (voltage) pattern of the two antenna beams when not squinted can be approximated by the normalized gaussian function exp(); where , and is the half-power beamwidth. Note that the hyperbolic cosine can be expressed as cosh and the hyperbolic sine as sinh ; and for small values of x, sin x x and cosh x 1. Also, sinh 2x = 2sinh x cosh x.11 This 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 phase , 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)?12 There are two methods for finding the radial velocity of a target. One is based on the Doppler shift ; the other is based on the rate of change of range with time R/t. They give different measurement accuracies.(a) What is the expression for the radial velocity error, found by measuring the Doppler frequency shift of a long quasi-rectangular pulse of width and RF