Linear Frequency Modulation Derived Polyphase Pulse-Compression Codes and an Efficient Digital Implementation.

In previous publications, the authors introduced a new class of polyphase pulse-compression codes and techniques for use in digitally coded radars. Such codes and compressors can be employed to obtain much larger time-bandwidth products pulse compression ratios than are feasible with analog dispersive delay lines. It is the purpose of this report to extend this class to include two new codes, one of which is tolerant of precompression bandwidth limitation. These new phase codes are conceptually derived from a linear frequency modulation waveform LFMW and are more doppler tolerant than other phase codes derived from a step approximation to a LFMW. This report will also describe an efficient technique for implementing these new phase codes in a digital pulse-expander-compressor and will present performance data. It should be noted that these phase codes are designed to be used both on transmission and reception to insure that the receive filter matches the transmitted waveform independent of time differences between the leading edge of the echo and a sampling pulse, i.e., independent of target range. The two new phase codes will be called the P3 and P4 codes to distinguish them from the P1 and P2 codes. The P3 code is not precompression bandwidth limitation tolerant, but is much more doppler tolerant than the Frank or P1 and P2 codes. The P4 code is a rearranged P3 code with the same doppler tolerance and with better precompression bandwidth limitation tolerance.