Resolving closely spaced targets using linear FM envelope processing

A novel signal processing technique for increasing range resolution in a class of radars is presented and applied. This technique, linear frequency modulation envelope processing (LFMEP), allows range resolution for LFM waveforms that is not limited in the usual way by the bandwidth. The technique can resolve targets separated by just a few wavelengths of the carrier without requiring pulse-to-pulse coherency. This capability is achieved by estimating envelope magnitude and slope characteristics of several received LFM waveforms. By exploiting the noncoherence of these returns, target separation can be derived from the eccentricity of the envelope characteristics. X-band radar measurements are presented to demonstrate the method. The paper concludes with questions of practicality and applicability to be addressed by future research.