Complementary-sequence pulse radar with matched filtering following

Abstract

A radar generates first and second mutually complementary binary code sequences. The autocorrelation functions of the first and second pulse sequences are selected so that, in the sum of their autocorrelation functions, the main lobes add, and the sidelobes are of equal amplitude and opposite polarity, and therefore cancel. The radar sequentially transmits dispersed pulses in which the chips are phase modulated with the two codes. The received pulses are applied uncompressed to the input of a Doppler filter bank, which filters them into various Doppler channels, each representative of a particular radial velocity of the target. Within each channel, the received signals modulated by the first code are matched-filtered by a filter matched to the first code, to produce a first time-compressed pulse, and those modulated by the second code are matched-filtered by a filter matched to the second code, to produce a second time compressed pulse. The time-compressed pulses include a main lobe which represents the range of the target, and also include sidelobes which may introduce range ambiguity. The first and second time compressed pulses are added together in each Doppler channel, to produce, in each channel, range pulses in which the range sidelobes are suppressed. Thus, range sidelobe suppression is accomplished without the use of discrete range sidelobe suppressors.