Two new polyphase pulse compression codes and efficient digital implementation techniques are presented that are very Doppler tolerant and that can provide large pulse compression ratios. One of these codes is tolerant of precompression bandwidth limitations.In previous publications [1,2], 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 paper to extend this class to include two new codes, one of which is tolerant of precompression bandwidth limitation that appears in radar receivers [2]. The availability of several different codes provides a radar designer with more flexibility.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. By Doppler tolerant, we mean that the compressed pulse does not degrade significantly with relatively large Doppler shifts on echoes. These new phase codes also have low range-time sidelobes without amplitude weighting. Also described is an efficient technique for implementing these new phase codes in a digital pulseexpander-compressor, and performance data is presented.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. NEW PHASE CODESThe two new phase codes will be called the P3 and P4 codes to distinguish them from the P1 and P2 codes discussed in [2]. The P3 code is not precompression bandwidth limitation tolerant but is much more Doppler tolerant than the Frank [31 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. P3 CODEThe P3 code is conceptually derived by converting a linear frequency modulation waveform to baseband using a local oscillator on one end of the frequency sweep and sampling the inphase I and quadrature Q video at the Nyquist rate. Letting the waveform to be coherently detected have a pulse length T and frequency f = fo + kt (1) Manuscript

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A new class of symmetric radar pulse compression polyphase codes is introduced which is compatible with digital signal processing. These codes share many of the useful properties of the Frank polyphase code. In contrast with the Frank code, the new codes are not subject to mainlobe to sidelobe ratio degradation caused by bandlimiting prior to sampling and digital pulse compression. It is shown that bandlimiting the new codes prior to pulse compression acts as a waveform amplitude weighting which has the effect of increasing the mainlobe to sidelobe ratios.

The open-loop GramSchmidt (GS) canceler is shown to be numerically identical with the sampled matrix inversion (SMI) algorithm in the transient stale if infinite numerical accuracy is assumed. n o f o r m of the GS canceler art discussed and analyzed: concurrent and noncurrent processing. Results for concurrent and nonconcurrent SMI cancelers have been obtained in the past by Reed, Mallet, and Brennan under the assumption that the inputs are Gaussian Many of those results are reproduced here using the GS structures as an analysis tool. In addition, new results are obtained when the input noises are not Gaussian. The delelerous effect of "over-matching the degrees of freedom" is discussed.