A Technique for Calibrating the Phase Detector of Wideband Radars Using a Phase Modulation and Demodulation Scheme

Abstract : A signal processing method is presented for correcting imbalances in the phase-detection channels of a coherent, wideband radar. Several papers have addressed this problem by the use of the fast Fourier transform (FFT) as a narrowband filter (see F. E. Churchill, G. W. Ogar, and B. J. Thompson, The Correction of I and Q Errors in a Coherent Processor, IEEE Trans. Aerosp. and Electron. Syst., AES-17 (January 1981), pp 131-137, and H. Bruce Wallace and Thomas J. Pizzillo, A Technique for Calibrating the Phase Detector of a Wideband Radar Using an External Target, Army Research Laboratory, ARL-TR-1521 (March 1998)). The present technique relies upon phase modulation of the transmitted waveform, then demodulation of the phase of the received waveform, and finally the integration and normalization of the waveform. There is one constraint; the number of phase-modulation/demodulation steps is restricted to 4 k, where k is an integer greater than 0. The technique is not dependent upon the target or the phase and gain flatness of the radar waveform. Errors remaining after application of this technique depend on the signal-to-noise ratio and errors in the phase modulator.