Self-compensated coherent integration method for coherent lidar system

Shumpei Kameyama; Takahiko Fujisaka; Kimio Asaka; Toshiyuki Ando; Yasuharu Koyata; Yoshihito Hirano; Shusou Wadaka; Toru Tajime

doi:10.1117/12.417064

13 February 2001 Self-compensated coherent integration method for coherent lidar system

Shumpei Kameyama, Takahiko Fujisaka, Kimio Asaka, Toshiyuki Ando, Yasuharu Koyata, Yoshihito Hirano, Shusou Wadaka, Toru Tajime

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Proceedings Volume 4153, Lidar Remote Sensing for Industry and Environment Monitoring; (2001) https://doi.org/10.1117/12.417064
Event: Second International Asia-Pacific Symposium on Remote Sensing of the Atmosphere, Environment, and Space, 2000, Sendai, Japan

Abstract

In this paper, a new signal processing method named SCCI (Self- Compensated Coherent Integration) which enables a coherent integration over a longer time, compared to a coherence time of a back-scattered signal, is proposed. A back-scattered signal is gated by a constant time gate of which a gate time is set to be shorter than a coherence time. Each gated signal is sampled as a former and a latter part. A gated signal in each part is integrated coherently by FFT. A cross spectrum of two parts is calculated in each time gate. Since a phase of a cross spectrum in each time gate is constant, this process is identified to a self-phase-compensation. A cross spectrum is integrated over all time gates. This process is identified to a coherent integration of a back-scattered signal over a signal length which is longer than a coherence time, since a phase of a cross spectrum in each time gate is constant. The signal to noise ratio (SNR) for SCCI is theoretically higher than that for PDI (Post Detection Integration) in the case of N>16/SNRP2 (N: Gate number, SNRp: SNR of a time gate for PDI) at low SNR. SCCI is superior to PDI in every case at low SNR if a required SNR in a system is up to 6dB and a Doppler frequency of a back-scattered signal is constant in a signal length. Furthermore, if SNRP becomes lower and lower, and a required SNR is higher and higher compared to 6dB, the effect of using SCCI appears more and more distinctly. We confirm the effect experimentally using a 1.5-µm wind sensing lidar system. Keywords: Coherent lidar, Coherent integration, Coherence time, Signal division, Self-compensation, Doppler frequency, Wind sensing, SNR, SCCI, PDI

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Shumpei Kameyama, Takahiko Fujisaka, Kimio Asaka, Toshiyuki Ando, Yasuharu Koyata, Yoshihito Hirano, Shusou Wadaka, and Toru Tajime "Self-compensated coherent integration method for coherent lidar system", Proc. SPIE 4153, Lidar Remote Sensing for Industry and Environment Monitoring, (13 February 2001); https://doi.org/10.1117/12.417064

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KEYWORDS

Signal to noise ratio

Doppler effect

Signal processing

LIDAR

Signal detection

Interference (communication)

Sensing systems

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