Departmental Seminar

Mitigating the effects of phase and Doppler frequency offsets in coherent random modulated LiDAR

Mr James Spollard

Light Detection And Ranging (LiDAR) is a remote sensing technology that can measure both range and relative radial velocity of a target with applications such as perception for autonomous vehicles and remote asset monitoring. In this talk, I will start by providing an overview of current LiDAR technologies and their applications, before moving onto the benefits and challenges of random modulated LiDAR. I will present a detailed analysis of techniques to mitigate the effects of phase noise and Doppler-induced frequency offsets in coherent random amplitude modulated continuous-wave (RAMCW) LiDAR. The analysis focuses specifically on a technique which uses coherent dual-quadrature detection to enable a sum of squares calculation which removes the input signal's dependence on carrier phase and frequency. A combination of simulations and experiments demonstrate the sum of squares technique's ability to measure distance with consistently high SNR, more than 15 dB better than alternative techniques whilst operating in the presence of otherwise catastrophic phase noise and large frequency offsets. In principle, the technique is able to mitigate any sources of phase noise and frequency offsets common to the two orthogonal outputs of a coherent dual-quadrature receiver including laser frequency noise, speckle-induced phase noise, and Doppler frequency shifts due to accelerations.

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