Continuous transmission FM sonar with one octave bandwidth and no blind time

Despite the advantage of high average power output, traditional continuous transmission FM (CTFM) sonars suffer from two major defects: separate transmit and receive transducers are required, and the demodulated signal is unavailable for a proportion of the sweep period. The paper shows how, by using a dual-demodulation system, the demodulated signal can be made continuous, resulting in the complete elimination of the blind time and in a range resolution as good as two wavelengths of the mean frequency. Experimental results using a CTFM air sonar justify both these claims.