Waveforms Search for Noncoherent Pulse Compression

Radar pulse compression is a prevalent radar technique that increases the bandwidth of a coherent radar pulse by intrapulse frequency modulation or phase coding. A matched filter (MF), used on receive, causes a long weak pulse to exhibit delay properties of a narrow strong pulse. Longer mismatched filters (MMF) are often used to lower the sidelobes of the delay response, with a penalty of a small loss in the signal-to-noise ratio. This article reviews techniques that extend this important concept to noncoherent sensors whose only emitted coding option is on-off (e.g., direct detection LIDAR). It shows that processing by a mismatched filter is obligatory rather than optional. It discusses merit measures and presents search results of medium-length, good, on-off sequences. The article covers also periodic on-off sequences, corresponding to continuous wave radar. Here the on receive MMF is replaced by a same period-length, real-valued, reference sequence, exhibiting perfect (sidelobe-free) periodic cross-correlation, with the emitted on-off periodic sequence. Detection in the presence of noise is demonstrated through Monte-Carlo simulations.