A smart DPLL for robust carrier tracking systems using uncertain rule-based IT2 fuzzy controllers

Abstract

The carrier tracking synchronizes the receiver and transmitter oscillators with each other’s and is adopted as a closed-loop structure known as the phase-locked loop (PLL). Fading, abrupt phase and frequency changes and relative speed between receiver and transmitter (user dynamics resultant from receiver vibrations) are some bottlenecks of robust carrier tracking. In tracking schemes that are used in a noisy environment and high user dynamics, bandwidth considerations are challenging. In this paper, uncertain rule-based interval type-2 (IT2) fuzzy controllers are utilized to handle the existence bandwidth contradiction in carrier tracking schemes in harsh applications. The proposed digital PLL (DPLL) is designed using a modified numerically-controlled oscillator (NCO) for better noise immunity. The designed IT2 fuzzy controllers determine optimal DPLL loop filter coefficients and consequently bandwidth to reject noise, handle user dynamics, and sustain locked. The suggested DPLL is simulated with Xilinx System Generator and indicates effective responses to various test signals such as phase and frequency steps, frequency ramp and added sinusoidal jitter stimuli with fast acquisition and improved pull-in range.