FUZZY-LOGIC FOR DIGITAL PHASE-LOCKED LOOP FILTER DESIGN

The problem of robust phase-locked loop design has attracted attention for many years, particularly since the advent of the global positioni ng system. This paper proposes and demonstrates the use of a fuzzy PLL to estimate the time-varying phase of a sinusoidal signal. It is show n via simulation results that fuzzy PLL's offer performance comparable to analytically derived PLL's (e.g. Kalman filters and H-infinity est imators) when the phase exhibits high dynamics and high noise. The fuz zy PLL rules are optimized using a gradient descent method and a; gene tic algorithm.