FREQUENCY SPECTRUM ANALYZER AND RADAR SYSTEM EMBLOYING THE SAME

摘要

1524633 Radar systems RAYTHEON CO 28 July 1976 [14 Aug 1975] 31506/76 Heading H4D The Doppler frequency of stored timed compressed echo signals in a digital radar receiver is detected by mixing the stored signals with an internally generated frequency swept "chirp" pulse signal and measuring the time of occurrence of an output from a pulse compressor circuit fed with this mixed signal. Received echo signal trains from a conventional coherent radar trans/ceiver 10 are fed separately in phase quarature at the radar p.r.f. f. to their respective stores 26 in time compressor section 24 which stores 64 returns from previous p.r.p.'s in each of 8 analogue (or C.C.D.) delay lines corresponding to 8 range bins. Under control of unit 15, a "chirp" pulse is produced in generator 28 including dispersive surface wave acoustic device 35 and is fed in quadrature to mixers 98 and where it is mixed with the complete contents of one quadrature pair of stores 26 which are read out by respective multiplexer 27 and 29. The readout video signals appear as single sidebands on the chirp pulse. Summer 104 combines the quadrature signals and is connected to pulse compressor 32 which also includes a surface wave acoustic device having appropriate time delay and compressive bandwidth, with respect to the dispersive bandwidth of the chirp pulse. The time delay between the occurrence of chirp pulse trigger P from unit 15 and the occurrence of the compressed pulse at the output of compressor 32 is a measure of the Doppler frequency and may be measured in utilization device 31.