Multiple-target frequency-modulated continuous-wave ranging by evaluation of the impulse response phase

A microwave frequency-modulated continuous wave (FMCW) radar for precision ranging of multiple targets is described. The evaluation of the FMCW raw data is based on a fast Fourier transform (FFT). In contrast to customary techniques, we additionally evaluate its phase. The phase ambiguity is resolved on the basis of the more approximate envelope evaluation. The FMCW system does not need separate phase measurements, however, the phase information is extracted from the FMCW data. In comparison with conventional FFT techniques the evaluation of "response phase" enhances measurement accuracy or, which is equivalent, allows one to reduce the sweeping bandwidth while maintaining accuracy. The phase processing implies a Hilbert transform, which leads to small phase errors. The algorithm can be extended, such that the phase measurement is essentially error-free. One makes use of the virtual range finder, where measurement data are compared with synthetically prepared data to achieve the best fit.