An Adaptive Tracking Algorithm for Burst OQPSK Modulation DSSS Systems
摘要
In the context of low frequency, low speed, and bandwidth limited Internet of Things (IOT) communication scenarios, an adaptive tracking algorithm research is proposed for communication system that combines burst direct sequence spread spectrum (DSSS) technology and offset quadrature phase shift keying (OQPSK) modulation technology. By jointly designing frequency locked loop and phase locked loop, the frequency and phase of the carrier are tracked and compensated during receiving. A code loop is also been designed to track and compensate for time error deviation. Meanwhile, considering various noise environments, a control mechanism for adaptive switching has been designed. According to adjusting the loop coherent integration time, noise bandwidth, and the control of loop mutual assistance updates, stable and excellent performance can be achieved. Furthermore, a Kalman filter is designed to estimate and compensate system state parameters and errors to reduce error jitter and smooth the statistical deviation error of system state. Through simulation and statistics of self-excited noise in loop, it serves as the initial value of the noise parameters in the Kalman state equation and measurement equation. For Kalman filtering requirement, an adaptive mechanism has also been designed and simplified to balance the performance and computation. Through modeling and simulation comparison, it was verified that this algorithm has better performance and adaptability.