Adaptive Notch Filter in Bandwidth as OSG for a PLL

Abstract

This paper presents a new structure of an Orthogonal Signal Generator for a Phase Locked Loop (OSG-PLL), utilizing an Adaptive Notch Filter (ANF) in bandwidth as the foundation. The ANF employed to generate the orthogonal system within the Phase Locked Loop (PLL), is implemented from the parallel configuration of several Bandpass Filters (BPF), starting from a lattice-structured All- Pass Filter (APF). This approach offers benefits such as simplicity and reduced sensitivity to coefficient rounding in fixed-point Digital Signal Processor (DSP) implementations. The bandwidth changes adaptively by adjusting and achieving the optimization of the filter coefficients. Two adaptation algorithms are proposed, studied, and analyzed, one utilizing Gradient Descent (GD) and another based on Proportional Control of Maximum Error (ME). A series of comparative simulations are conducted using MATLAB software to validate the most effective method among the two described algorithms. The simulation results from MATLAB and the experimental results from a fixed- point digital signal processor (DSP), specifically the TMS320F812, are showcased and examined to assess the effectiveness of the algorithm of proportional control of the ME, which has been selected as the superior alternative, thereby supporting its theoretical development.