Understanding and Ameliorating Non-Linear Phase and Amplitude Responses in AMCW Lidar

Abstract

Amplitude modulated continuous wave (AMCW) lidar systems commonly suffer from non-linear phase and amplitude responses due to a number of known factors such as aliasing and multipath inteference. In order to produce useful range and intensity information it is necessary to remove these perturbations from the measurements. We review the known causes of non-linearity, namely aliasing, temporal variation in correlation waveform shape and mixed pixels/multipath inteference. We also introduce other sources of non-linearity, including crosstalk, modulation waveform envelope decay and non-circularly symmetric noise statistics, that have been ignored in the literature. An experimental study is conducted to evaluate techniques for mitigation of non-linearity, and it is found that harmonic cancellation provides a significant improvement in phase and amplitude linearity.

Keywords

• phase linearity
• AMCW
• Lidar
• harmonic cancelation
• heterodyning
• irregular phase steps
• crosstalk
• multipath
• non-circularly-symmetric noise