Quadriphase code-a radar pulse compression signal with unique characteristics

A description is given of a class of radar signals called quadriphase codes. The quadriphase code described is derived from a prototype biphase code by a biphase-to-quadriphase (BTQ) transformation. These codes feature subpulses with a half-cosine shape and a phase change between the adjacent subpulses restricted to either +90 degrees or -90 degrees . This feature results in the spectrum falloff of 12 dB/octave compared with the biphase code spectrum falloff of 6 dB/octave. After a discussion of biphase codes with low autocorrelation sidelobes and tabulating selected biphase codes, the authors show the synthesis of the quadriphase code from the prototype biphase code. Quadriphase-code characteristics, including the autocorrelation function, the compressed pulse shape, the spectral characteristics, the energy pulsewidth, the pulse compression ratio, the range sampling loss, the Doppler effect, and the tabulation of selected quadriphase-code properties are presented. Digital decoding of the quadriphase codes is discussed, including the linear decoder and the coded pulse anticlutter system (CPACS) decoder, one form of phase discrimination constant false alarm rate. >

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