A Continuous-time Analog Circuit for Computing Time Delays between Signals

A Continuous-Time Analog Circuit for Computing Time Delays Between Signals Chiang-Jung Pu and John G. Harris University of Florida EE Dept., 446 CSE Bldg 42 Gainesville, FL 32611 Abstract| We describe an analog VLSI circuit that computes the time delay between an arbitrary input signal and its delayed version. Versions of this circuit will be used as the basic computational elements for human auditory localization models in both the horizontal and vertical directions. Since the circuit uses subthreshold CMOS circuitry, chip measurements show that delays ranging over ve orders of magnitude can be recovered. The circuit delays the rst input signal by two distinct time-constants and correlates each with the second input signal. The correlation values at the two points are then integrated and used to compute a nite-di erence derivative that dynamically adjusts the time constants until an optimal delay is found. This paper describes the rst continuous-time circuit for computing delays between arbitrary signals.