Patent ID: 7573564

Claim:
A laser detection and ranging (LADAR) system comprising: a waveform generator for generating an arbitrary waveform; a laser for transmitting a light signal toward a target, wherein a first optical modulator receives the arbitrary waveform; wherein the first optical modulator generates a modulated light signal; a second optical modulator generates a second modulated light signal that is fed into an optical coupling element to recover a light signal modulated by a Doppler frequency related to the wavelength of light; and a Doppler tracking loop, wherein the Doppler tracking loop comprises a phase lock loop; wherein the phase lock loop comprises a photonic mixing detector, wherein the photonic mixing detector is configured to receive said reflected Doppler modulated light signal; wherein the photonic mixing detector is further configured to receive a signal from the waveform generator, the photonic mixing detector comprises a metal-semiconductor-metal configuration; the Doppler tracking loop further comprises a first amplifier, wherein the first amplifier receives a signal from the photonic mixing detector, the Doppler tracking loop further comprises a low-pass filter, wherein the low-pass filter receives the amplified signal from the first amplifier, and wherein the Doppler tracking loop further comprises a voltage-controlled oscillator (VCO) with operating frequency commensurate with the expected range of Doppler frequencies related to the wavelength of light, wherein the voltage-controlled oscillator is configured to receive a signal from the low-pass filter, and wherein the voltage-controlled oscillator is further configured to transmit an output signal to the photonic mixing detector.