Abstract:
It was impossible to directly estimate the Doppler frequency difference of the frequency-hopping observation signal containing multiple pulses in the passive positioning scenario of moving multi-station because the wideband frequency-hopping communication signal’s carrier frequency hopping results in a changing Doppler frequency shift. If only the single-hop signal’s time-frequency difference is evaluated, the estimation precision won’t be sufficient for locating. This study suggested a joint time difference and Doppler velocity difference estimation approach for coherent accumulation of multi-pulse coherent accumulation of frequency hopping signals in order to address this issue. Firstly, a time difference-Doppler velocity difference model was established for the wideband frequency hopping observation signal. Then, each pulse pair’s frequency domain conjugate product was phase-compensated and accumulated. Finally, by looking for the two-dimensional peak value of the cost function, the predicted time difference and Doppler velocity difference of the multi-pulse frequency hopping signal were discovered. The simulation results demonstrated that the method proposed in this paper had a significant improvement in estimation accuracy compared to the single-hop method and the multi-pulse non-coherent accumulation method, and can be close to CRLB under the condition of medium and high signal-to-noise ratio. This demonstrates the correctness and precision advantages of the proposed method.