Coherent Doppler LIDAR with long-duration frequency-modulated pulses for wind sensing.

A coherent Doppler LIDAR (CDL) with long-duration frequency-modulated pulses was demonstrated and validated by analyzing the data observed by a prototype. In traditional CDL using short-duration single-frequency pulses (PCDL; pulsed CDL), there exists a trade-off relationship between distance and velocity resolution. Meanwhile, in earlier work, a theoretical framework of CDL using long-duration frequency-modulated pulses (FMCDL; frequency-modulated CDL) was put forth to eliminate the trade-off. We developed the prototype to be operated as both a PCDL and FMCDL. Analyses of data observed by the PCDL and FMCDL modes showed that the FMCDL worked in good agreement with the PCDL for wind ranging and velocimetry. Furthermore, the performance of the FMCDL in terms of received power and resolution of distance and velocity was quantitatively consistent with ones theoretically expected.

Wind ranging and velocimetry with low peak power and long-duration modulated laser.

A novel approach to simultaneous wind ranging and velocimetry using low peak power, long-duration modulated laser pulse transmissions is proposed. Received signals backscattered by aerosol particles are processed by a multi-reference matched-filter (MRMF) which performs matched filter processing between the received signal and several reference signals in parallel and outputs a range-velocity profile of received power. Ranging and velocimetry are performed simultaneously by estimating received power, radial velocity, and velocity dispersion from a velocity profile at an arbitrary range in the range-velocity profile. The accuracies of the three estimates improve in proportion to the square root of pulse duration; that is, a 100 times longer pulse is equivalent to a 10-dB amplification.