A technique for resolving range-Doppler ambiguities at microwave, millimeter, or optical wavelengths

A novel method of suppressing range-Doppler ambiguities and investigating properties of echoes involving high radial velocities and/or substantial ranges is presented. This is a recurring problem with radar, lidar, and other surface, airborne, and satellite sensors. The simplest problem is that of range-Doppler ambiguity resolution of quasi-point targets. Here, a dual-wavelength signal can be transmitted and processed to decouple the range/velocity ambiguity. For range-spread targets (such as clutter or precipitation), the difference wavelength must be chosen with regard to the decorrelation properties of the echo. A nonlinear operation is discussed which allows separating difference-frequencies that are comparable to the spectral expanse of the signal. Laboratory results are discussed along with the information available from returns involving extended, or continuum returns, using dual-frequency autocorrelation methods