Hybrid Lidar-radar Receiver for Underwater Imaging Applications

The objective of this program is to develop a hybrid Lidar-radar receiver to efficiently recover and process the radar sub-carrier from a modulated pulsed optical signal in the presence of high levels of optical clutter reaching the receiver just prior to the signal of interest. The receiver will ultimately be used with modulated (0.5 – 1.0 GHz) blue-green pulsed lasers and is required to have an active detection area of at least 8 mm, as well as high QE in that wavelength region. The main challenges are to design a compatible receiver module that has a fast response time combined with high sensitivity, low noise characteristics and a high enough dynamic range. High dynamic range is required to accommodate weak returns from low reflectance targets at multiple attenuation lengths, as well as higher energy returns from stronger reflectors closer to the receiver. Utilizing high speed digitization, the design allows for flexible digital processing and demodulation.