Time-Optimal PLL Using the High-Speed Null Method

Abstract

A new configuration of phase-lock(ed) loop achieving a peerlessly rapid performance is presented in comparison with the conventional PLL's having limited responsiveness. The principle proposed in this paper makes a step further than an improvement on the existing structure; namely, a time-optimal condition is considered in terms of the input/output relationship regarding the circuit as a black box, and a PLL is devised anew realizing the condition and being free from the traditional arrangement. The outcome PLL features two distinctive properties in operation; i. e., the employment of period rather than frequency as the control variable by the use of a voltageto-period converter, and the replacement of the loop filter by time-discrete elements. A prototype comprising 10 IC's demonstrates that the time-optimal PLL can track in 2 cycles any abrupt frequency shift smaller than 1 octave and it provides an FM demodulation output free of ripples in a frequency range of 0.01Hz to 100kHz.