Analog circuit for sound localization applications

We describe an analog CMOS circuit that computes the time (phase) delay between two 10 kHz sinusoids. This circuit can be used in sound localization applications. We realize a locking range of 10-170 degrees in less than 1 ms that is robust over process variations. Two receivers placed at a distance from one another intercept a sinusoidal waveform emanating from a sound source. The phase difference between the two signals is detected by the circuit, which gives an estimation of the distance of the source from the receivers. This solution is simpler and more elegant than current digital techniques that require specialized DSP hardware to be implemented in real time.