Multiple return analysis for noncoherent pulse compression of periodic coded waveforms

Recently proposed direct-detection laser range finders transmit low power, periodic, unipolar (ON-OFF) coded signal, instead of the commonly used strong narrow single pulse. The combination of non-coherent pulse compression (NCPC) and appropriate binary sequences produces a sidelobe-free periodic delay response. The continuous wave (CW) nature of the signal results in overlaps between returns from multiple targets. When envelope detected, the overlaps can create intermodulation that may hurt the sidelobe-free range response. The paper studies the effect of different sequence types and different envelope detector response profiles and suggests measures to mitigate the influence of multiple targets by calibration of envelope detector.