The relationships among heterodyne efficiency γ, number of speckle cells M, and the ratio of receiver area to coherence area S R/S C for a pulsed coherent laser radar (CLR) are written through the use of mutual coherence functions. It is shown that numerical values for S R/S C that follow Goodman’s definition [J. W. Goodman, in Laser Speckles and Related Phenomena, J. C. Dainty, ed. (Springer-Verlag, Berlin, 1975), pp. 9–75] or that are obtained through the use of a transverse-field coherence length agree. In the frame of the Gaussian model proposed by Frehlich and Kavaya [Appl. Opt. 30, 5325 (1991)] a new equation is derived: M = (1 + S R/S C). This equation agrees with our experimental results. Our theoretical analysis shows that the number of speckle cells for an optimal monostatic CLR system is M ~ 4. An experiment has been conducted with a ground-based pulsed CO2 LIDAR and remote hard targets to study the probability density function of LIDAR returns as a function of M and to study the dependence of M on S R/S C. An assessment of CLR performance through the use of M or the collecting aperture S R is discussed.
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