Phase-Code-Based Modulation for Coherent Lidar

Lidar is considered to play an essential role on the road towards fully autonomous driving. In this context, coherent lidar systems hold the potential for lean, efficient and inexpensive sensors, but their performance depends significantly on suitable modulation and signal processing methods that can handle high Doppler shifts and enable high measurement rates at low computational complexities. This paper presents four novel phase-modulation-based approaches that utilize pseudo-random binary sequences to estimate target distances up to 180 m and the absolute value of target velocities up to 80 m/s. The corresponding system setup is lean, as it is based on only one phase modulator and one non-quadrature demodulator. The proposed methods are assessed analytically and by simulations and are compared in terms of computational complexity, detection performance, measurement rate and accuracy. The results demonstrate that while each approach has individual advantages and limitations, the proposed methods offer essential advancements in terms of measurement rate, multiplexing potential and multi-target capability, compared to already known methods. The feasibility of all presented approaches is validated by measurements.