On an approach for improving the range resolution of pulsed coherent Doppler lidars

As a result of an analysis of the autocovariance of the complex heterodyne lidar signal, some general-enough inverse techniques (algorithms) are derived for recovering with high range resolution, below the sensing pulse length, of Doppler-velocity profiles in the atmosphere. Unlike our preceding works, it is assumed here that the laser pulses can have arbitrary fluctuating shape. The presence is also supposed of possible regular, arbitrary in form, intrapulse frequency deviations (chirp) and random frequency, phase and radial (Doppler)-velocity fluctuations. The algorithm performance and efficiency are studied and illustrated by computer simulations, taking into account the influence of the chirp and various random factors such as additive noise, pulse-shape fluctuations and radial-velocity fluctuations. It is shown that the algorithms developed allow the Doppler-velocity profiles to be determined with a considerably shorter resolution interval compared with the pulse length, at a reasonable number of signal realizations (laser shots) and appropriate data processing to reduce the statistical error due to the random factors.