A Heterodyne Double-Phase-Locked Loop for Secondary Time and Frequency Standards

Abstract

This paper considers a novel phase-locked loop structure for the generation of secondary time and frequency standards from a transmitter signal. It consists of two voltage-controlled oscillators, a mixer and a phase detector. The present study, which takes into consideration the effect of the internal noise of the oscillator as well as the unwanted disturbances accompanying the transmitter signal, clearly indicates that the heterodyne double-phase-locked loop is superior to the existing types of phase-locked loops for at least three reasons, viz., (i) by a proper choice of the system parameters, the long-term frequency stability of the local oscillators can be improved to a large extent without affecting the short-term stability, (ii) the system is highly immune to the external noises that may corrupt the transmitter signal, and (iii) the system can be used to generate three standard frequency signals in the ratio of 1: 2: 3.