The coherent lidar system for speed measurement and the characteristics of the echo signal are discussed. And the principle and the advantages of the digital quadrature transform are analyzed. A digital quadrature detection scheme based on polyphase filter for coherent lidar system for speed measurement is presented by using the idea of software radio. Firstly the amplified analog signal is sampled to digital signal, and then is re-sampled with parity, time-aligned by delay filtering, finally the signal is divided into in-phase component and quadrature component. The scheme can be used to decrease the hardware complexity of system to a large extent, to avoid aliasing between the positive and the negative spectrums, to improve the SNR, and to obtain the signal in the quadrature form so as to fit the follow-up processing. Simulations and experiments indicate that the scheme is capable of resisting the noise compared with the traditional methods and is prone to real-time implementation, which, in turn, makes a contribution to greatly improve the performance of coherent Doppler lidar system for speed measurement and to orient the direction of a moving target.

Date Published: 20 May 2009
PDF: 5 pages
Proc. SPIE 7283, 4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 728323 (20 May 2009); doi: 10.1117/12.828695

Published in SPIE Proceedings Vol. 7283:
4th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment
Yudong Zhang; James C. Wyant; Robert A. Smythe; Hexin Wang, Editor(s)