LAUSR

The range resolution of radar is inversely proportional to the swept bandwidth. However, this bandwidth may not be available due to a variety of reasons, including spectrum congestion and lack of instantaneous bandwidth despite access to a larger tunable bandwidth. Existing approaches to achieving high-range resolution include bandwidth extrapolation, ultrawideband coherent processing, and spectral splicing of narrowband stepped-frequency pulses. In this article, we achieve high-range resolution of a wideband chirp from a sequence of narrowband pulses using coherent-phase extension of the beat tones of an FMCW dechirper. By phase matching the beat tones across pulse boundaries, the algorithm trades a longer observation interval for a smaller swept bandwidth. Phase matching of the short beat tones is applied in two steps to first obtain the coarse estimate of the beat frequencies which are then used as the starting point in the formation of the range-Doppler map that now enjoys the two-dimensional fast-Fourier transform (2-D-FFT) gain. With this approach, a fraction of the total bandwidth to obtain a range resolution of a wideband chirp is used. Using both simulations and experimental data, the proposed high-resolution algorithm is applied to a narrowband chirp sequence with bandwidth $B$ to generate range-Doppler maps with range resolution corresponding to a wideband chirp sequence of bandwidth $NB$.