Abstract: A radar transmission, reception and signal processing system generates high esolution synthetic aperture radar ground maps from air or space platforms using waveforms in which frequency is changed pulse-to-pulse. The transmitted radar signal is comprised of a series N bursts with n pulses per burst wherein each of the pulses is a fixed frequency step, .DELTA.f, either above or below one or the other of the n pulses, i.e. the n pulses comprises an ordered set and further, preferably, wherein the set of n pulses is arranged in time as a random permutation of the ordered set. In each of the k sample gates for each burst the n complex samples of reflectivity are inverse Fourier transformed from frequency domain samples of reflectivity to synthetic range domain profiles to result in an array of aligned range profiles in each of k coarse range delay positions.

Abstract: A radar transmitter illuminates an unidentified remote radar target with pped or swept frequency pulses of microwave energy. The broad band of the frequencies of the reflected signal is received and divided into a large number of adjacent narrow-band segments. The amplitude of each segment is detected. The uniqueness of the set of amplitudes effectively "finger-prints" the target.

Abstract: A system is disclosed for utilizing frequency agile magnetron radars to porm one, two and three dimensional target imaging using coherent frequency agile radar waveforms. The pulses from a frequency agile magnetron are controlled so that their frequencies are approximately those of a highly coherent stepped frequency source. Means are provided for monitoring the magnetron's tuning piston position read-out voltage and for triggering the pulse forming network associated with the magnetron at the occurrence of each one of a set of predetermined read-out voltage levels. A feedback loop is utilized to determine the difference between the frequencies of the actual output pulses of the magnetron and a set of precise, stepped reference frequencies. Correction values are generated and are utilized to generate a new set of magnetron read-out voltage levels at which the pulse forming network is to be triggered. The phase of the echo pulse is measured for each frequency step of each burst from the magnetron.

Abstract: A system is disclosed for utilizing frequency agile magnetron radars to porm one, two and three dimensional target imaging using coherent frequency agile radar waveforms. The pulses from a frequency agile magnetron are controlled so that their frequencies are approximately those of a highly coherent stepped frequency source. Means are provided for monitoring the magnetron's tuning piston position read-out voltage and for triggering the pulse forming network associated with the magnetron at the occurrence of each one of a set at a predetermined read-out voltage levels. A feedback loop is utilized to determine the difference between the frequencies of the actual output pulses of the magnetron and a set of precise, stepped reference frequencies. Correction values are generated and are utilized to generate a new set of magnetron read-out voltage levels at which the pulse forming network is to be triggered. The phase of the echo pulse is measured for each frequency step of each burst from the magnetron.

Abstract: A radar is disclosed that obtains three-dimensional radar images of targets for target identification at tactically useful ranges. Images are generated with the radar in a target angle and range tracking mode. The image is a plot, display or recording of position of target scatterers in range and two orthogonal cross-range dimensions. Range resolution is obtained by generating synthetic range profiles from the monopulse sum channel echo voltages which results from transmitting a stepped frequency waveform. Cross-range resolution is obtained by similarly processing differential cross-range error voltages of the echoes seen at the output of two orthogonal channels of a wideband monopulse receiver.

Abstract: An apparatus is disclosed by which radar targets can be imaged in two dimions for identification at full radar range using relatively moderate speed data processing. Images of targets are found in range and cross-range dimensions from the time history of the targets' wideband spectral response obtained by a frequency stepping radar. A frequency synthesizer generates a series of N identical signal bursts, each burst comprising n pulses and each of said n pulses being a different frequency. The radar echos from this series of bursts is separated into n-phase and quadrature phase components. These components are processed to calculate and store the relative amplitude of each echo signal and to determine the phase of each echo signal relative to the phase of the corresponding transmitted pulse. Further, the echo signals are inverse Fourier Transformed to generate an n.times.N Fourier Transform array representing a synthetic target range profile.

Abstract: A low probability of intercept radar apparatus and technique involving operation at the lower water vapor absorption resonance frequency of 22.2 GHz wherein the radar beam is shaped such that it is restricted to low altitude and short range coverage. The system is implemented by conventional radar techniques with the exception of the technique disclosed herein of operating at the lower water vapor absorption frequency in combination with utilizing a rotating shaped beam antenna system that restricts the radar beam to low altitude and short range coverage.