Abstract:

The fast Fourier transform (FFT) is directly used after the nonlinear transforming of the sampled data of multiple phase shift keying (MPSK) signals in the traditional frequency measurement algorithm, which is simple to structure and easy to implement, but is hardly adapted to the application environment of large frequency dynamic and low signal-to-noise ratio (SNR) of MPSK signals resulting from target high-speed maneuvering and long-range communication due to poor accuracy and small scale of frequency measurement. A high-accuracy frequency measurement algorithm based on the process structure of the coarse and fine state is proposed in order to resolve the problem above. The power spectrum windowing method is used to roughly achieve the Doppler frequency shift in the coarse state. The method combining the rate-slotting correction with the sliding grouping and average compression is used to accurately measure the Doppler frequency shift and its range rate in the fine state. The experiment and analysis result verify that the proposed algorithm can achieve the Doppler frequency shift measurement precision up to Hz level with the Doppler change rate measurement precision up to Hz/s level in large frequency dynamic and low SNR environment, which effectively increase the frequency measurement accuracy and detection sensitivity of MPSK signals in large frequency dynamic and low SNR environment.

Key words: weak multiple phase shift keying (MPSK) signal, large frequency dynamic, low signal to noise ratio (SNR), high-accuracy frequency measurement, fast Fourier transform (FFT)