Experimental Results for Phase-Lock Loop Systems Having a Modified nth-Order Tanlock Phase Detector

Two parameters which are important in the theory and design of phase-lock loop systems are lock range and threshold. In this paper these parameters are carefully defined and the results of an experimental study to determine the effects of the modified thorder tanlock class of phase detector characteristics upon these parameters are presented. Lock range as a function of signal-to-noise ratio (SNR) is of particular interest. It is shown that when the SNR is high, the lock range of phase-lock systems with modified th-order tanlock phase detector characteristics exceeds that of systems employing a sinusoidal phase detector. However, as threshold is approached, the lock range of the tanlock systems falls off faster than the lock range of conventional sinusoidal systems. When compared to systems with sinusoidal phase detectors and normalized with respect to equivalent noise bandwidth the tanlock systems are shown to exhibit a higher threshold, but when normalized to lock range the tanlock systems have a slightly lower threshold. The series of curves which summarize the study may be used as an aid in the design of phase-lock loop systems.