Linear FM chirp pulse compression ladar receiver operating characteristic: 'maximum of M Rayleighs' statistics

摘要

Abstract: The linear frequency-modulation chirp pulse compression technique of classical microwave radar is examined in the context of coherent laser radar. A coherent CO$-2$/ laser radar may operate near 9.115 $mu@m and 33,000 GHz. Because of this short wavelength, a large target Doppler-spread is realizable in a single ladar measurement. In addition, target surface roughness with respect to wavelength causes the target backscatter points to be uniformly distributed over 2$pi radians in phase resulting in Gaussian/Rayleighegative-exponential receiver statistics. Target Doppler spread and speckle as well as target down- range extent affect the linear-FM-chirp pulse compression efficiency thereby degrading the peak compressed-pulse carrier-to-noise. This degradation in carrier-to-noise is quantified using a 'maximum of M Rayleighs' detector model which allows a simple scale factor degradation for other coherent ladar wavelengths, chirp magnitudes, and pulse lengths. The receiver-operating-characteristic of the sum of many Rayleigh distributed random variables is also developed for comparison to the classical sum of many negative- exponential statistics. !11