Analog Phase-locked Loop Research Articles

Phase-locked loops

An attempt to systematically outline the work done in the area of phase-locked loops which are now used in modern communication system design is presented. The analog phase-locked loops are well documented in several books but discrete, analog-digital, and digital. phase-locked loop work is scattered. Apart from discussing the various analysis, design, and application aspects of phase-locked loops, a number of references are given in the bibliography.

On the Performance of Digital Phase Locked Loops in the Threshold Region

Extended Kalman filter algorithms are used to obtain a digital phase lock loop structure for demodulation of angle modulated signals. It is shown that the error variance equations obtained directly from this structure enable one to predict threshold if one retains higher frequency terms. This is in sharp contrast to the similar analysis of the analog phase lock loop, where the higher frequency terms are filtered out because of the low pass filter in the loop. Results are compared to actual simulation results and threshold region results obtained previously.

Digital Phase Control Techniques

An analysis of a partially digitized phase-locked loop using Z -transform sampled data theory is presented. Responses are obtained at various junctions of the loop for both a step frequency input and for a sinusoidal frequency input. These responses are compared with the corresponding responses for an analog phaselocked loop. Stability criterion and root locus are determined. Effects of quantization are studied. It is concluded that over most of the range of operation the behavior of the digital phase-locked loop is nearly identical to the corresponding analog phase-locked loop, but that in addition, certain possible advantages may occur as a result of the digitization.