Simultaneous Processing of Time-Shifted Orthogonal LFMCW Waveforms

Abstract

There is a requirement for waveform orthogonality on dual or multiple channel radars to avoid cross-channel interferences. It is additionally favored that dual-channel polarization-orthogonal radars are capable of estimating target Polarization Scattering Matrix (PSM) elements simultaneously, that is within one Pulse/sweep/frame Repetition Interval (PRI). The current solution for simultaneity in Linear Frequency Modulated Continuous Wave (LFMCW) radars is to use a pair of nearly-orthogonal waveforms within the same frequency band with opposite frequency excursion slopes. This solution does not provide full orthogonality because of its susceptibility to some cross-channel interferences, where their mitigation result in difficult-to-suppress unwanted artifacts after range compression, in addition to opposite sign residual video phases which are difficult to compensate for. We propose a new pair of independent waveforms - along with their required processing steps - which satisfy both the orthogonality and simultaneity requirements, but with less undesirable artifacts than the opposite slope chirps. In this paper we present results from experimentation with simulated and radar-measured data for the new waveform. We found closely comparable results with the baseline of standard LFMCW processing. We aim to operationally use the new waveform-pair on the TuDelft PARSAX polarimetric radar.