Phase-locked loop design for flexible mode tracking

This paper describes the design of PLL to track sinusoid flexible mode signals in flexible satellites. The phase detector of the PLL is associated with a low pass filter which is usually not shown in literature. Specifications of the low pass filter are developed based on the frequency of the flexible modes. Subsequently, the filter order is designed with the desired suppression at high frequency. The control loop filter is designed to force the phase error to zero avoiding interaction with the phase detector. Simulation studies show tracking of frequency uncertainty up to ± 50% deviations with noisy signals with PLL designed for 30% uncertainty in frequency. A robust design has been achieved meeting the desired performance goals.