Non‐coherent pulse compression — aperiodic and periodic waveforms

Abstract

The growing interest in adopting pulse compression waveforms to non-coherent radar and radar-like systems (e.g. lidar) invites this update and review. The authors present different approaches of designing on-off {1, 0} coded envelopes of transmitted waveforms whose returns can be envelope detected and non-coherently processed. Two approaches are discussed for the aperiodic case: (a) Manchester encoding and (b) mismatched reference. For the periodic case, on-off sequences are described, which produce perfect periodic cross-correlation when cross-correlated with one or more integer number of periods of a two-valued reference sequence {1, −b}. This study provides comprehensive rules for designing periodic on-off waveforms and their references. The periodic waveform's highaverage duty cycle (over 50%) makes it a 'quasi continuous wave (CW) non-coherent waveform', which avoids the pulse-train conflict between average power and unambiguous range. Good experimental results with a laser range finder are presented. Reports on other uses are quoted.

Genetic-optimised aperiodic code for distributed optical fibre sensors

“…maximising the SNR improvement, so-called coding gain, whilst minimising the hardware overhead and extra measurement time); however, all currently existing code types present fundamental and/or practical limitations. For instance, although codes formed by a single sequence 40,[56][57][58][59][60][61][62]64 are ideal for minimising measurement time and data storage, they either exhibit an imperfect peak-tosidelobes ratio after the decoding 40,56,64 or are periodic/cyclic codes [57][58][59][60][61][62]64 that suffer from impairments induced by signaldependent noise 1 (resulting in a compromised coding gain that has not yet been quantified in literature). As more robust alternatives, distortion-free aperiodic codes constituted by several sequences, such as Golay [41][42][43][44][45][46][47] , Simplex codes [48][49][50][51][52]63 and their derivatives 54,55 , have been mostly used for DOFS.…”

Sequences with Perfect Periodic Auto and Cross Correlation Properties

“…The PACF clearly show that the magnitude of sidelobes other than peak is '1' which is constant. Levanon [13] and Jahangir [14] demonstrated the ideal periodic correlation properties of M-sequences and Legendre sequences by taking the crosscorrelation between the unipolar version {1, 0} of transmitted signal and the bipolar reference signal {±1}. It is shown that this method is advantageous in context of Non-coherent Pulse Compression (NCPC) radar.…”

“…The perfect periodic cross-correlation property is achieved at the cost of high energy loss. The energy efficiency of unipolar M-sequence (N=7) is nearly 57% and such signals are preferred in noncoherent processing [13,14]. For coherent processing, the reference signal must be same as the transmitted signal.…”

A new noncoherent radar pulse compression based on complementary sequences

“…Noncoherent pulse compression (NCPC) introduced in [7]- [9] employs the on-off keying (OOK) modulation. The OOK transmitted signal suggested for NCPC are based on Manchester coding well-known binary sequences, like Barker or minimum peak sidelobe (MPSL) codes.…”