Bitstream Photon Counting Chirped AM Lidar with Digital I/Q Demodulation

Abstract

This paper is a follow-up to two previous papers, one introducing the new bitstream Photon Counting Chirped Amplitude Modulation (AM) Lidar (PC-CAML) with the unipolar Digital Logic Local Oscillator (DLLO) concept, and the other paper introducing the improvement thereof using the bipolar DLLO. In that previous work, there was only a single channel of digital mixing of the DLLO with the received photon counting signal. This paper introduces a new bitstream PC-CAML receiver architecture with an in-phase (I) digital mixing channel and a quadrature phase (Q) digital mixing channel for digital I/Q demodulation with the bipolar DLLO to improve the signal-to-noise ratio (SNR) by 3 dB compared to that for the single digital mixing channel with the bipolar DLLO and by 5.5 dB compared to that for the single digital mixing channel with the unipolar DLLO. (patent pending) The bipolar DLLO with digital I/Q demodulation architecture discussed in this paper retains the key advantages of the previous bitstream PC-CAML with a DLLO systems since it also replaces bulky, power-hungry, and expensive wideband RF analog electronics with digital components that can be implemented in inexpensive silicon complementary metal-oxide-semiconductor (CMOS) read-out integrated circuits (ROICs) to make the bitstream PC-CAML with a DLLO more suitable for compact lidar-on-a-chip systems and lidar array receivers than previous PC-CAML systems. This paper introduces the bipolar DLLO with digital I/Q demodulation receiver architecture for bitstream PC-CAML and presents the initial signal-to-noise ratio (SNR) theory with comparisons to Monte Carlo simulation results.