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26 April 1999 New scheme of coherent array detection to cancel out phase fluctuations and Doppler frequency shift due to atmospheric turbulence and target movement for laser communications
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Abstract
A coherent array detection system, which uses multiple independent apertures/receivers whose IFs are electro- optically co-phased in real time and then added together, can mitigate the laser signal fluctuations and fading due to atmospheric turbulence for laser communications and radar. Thus the system performance greatly depends on the electo- optic phase-locked loops (EOPLL) used for the real time co- phase of signals from the independent aperture/receivers. But if the fast phase fluctuations due to atmospheric turbulence or a high Doppler frequency shift due to the target (satellite) movement are induced to the laser signal which is beyond the response speed of the EOPLL, the system can not mitigate the signal fluctuations and fading anymore. This paper presents a new scheme which can make the coherent array detection system get rid of the EOPLL. This scheme uses a reference laser beam as well as laser signal with different polarization as the transmitted beam. By separating the received laser reference beam and signal due to their polarization and through two stage mixing, the IF signals from the multiple independent aperture/receivers will be co-phased automatically.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jing Xu, Ronald L. Phillips, and Larry C. Andrews "New scheme of coherent array detection to cancel out phase fluctuations and Doppler frequency shift due to atmospheric turbulence and target movement for laser communications", Proc. SPIE 3615, Free-Space Laser Communication Technologies XI, (26 April 1999); https://doi.org/10.1117/12.346195
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