The Influence of ISI and an Improved Algorithm of Channel Estimation in the Chirp System

Chirp signal is widely used in communication, radar, sonar and ultrasonic systems. The impulse response of channel must be estimated in PSK chirp spread spectrum modulation systems which is a chirp signal multiplied by the PSK modulated signal. Due to the influence of filters and multipath channel, the received signal of current symbol will be affected by the interference of the previous symbol and the next symbol, the interference which is called inter-symbol interference (ISI) can degrade the performance of channel estimation and demodulation. In this paper, based on BPSK chirp spread spectrum modulation system, we describe the received model, the channel estimation based on FFT and channel estimation of matched filtering, analyze the impacts of ISI on channel estimation. And we simulate the MSE of channel estimation and the simulation results are consistent with the analysis, then an improved method of channel estimation is proposed based on the analysis of the impact of ISI on channel estimation.