Design of a rapidly acquiring and noise immune PLL for communication systems

Phase-locked loops (PLLs) are extensively used for carrier synchronization. For signals with slowly varying phase and frequency, the best performance is achieved with PLLs. However, PLLs cannot provide rapid acquisition with high probability when acquiring signals with high a priori phase and frequency uncertainty because of the hang-up phenomenon. This paper presents a new approach to the synthesis of PLLs employing the indirect nonlinear filtering theory. Through Monte Carlo simulations, the use of this approach is shown to allow the creation of a PLL devoid of the hang-up phenomenon. It also provides a wider pull-in range, more rapid acquisition without degrading the estimation accuracy in the tracking mode, and a lower probability of losing lock than the traditional algorithms of the PLL do.