An Efficient Coarse-to-Fine Doppler Parameter Search Method for Moving Target Detection Using GNSS-Based Passive Bistatic Radar

The global navigation satellite systems (GNSS), as illuminators of opportunity, form passive bistatic radar (PBR) systems that offer advantages, such as wide coverage, low power consumption, and low cost, making them suitable for moving target detection. However, the low power budget and small Doppler tolerance of GNSS signals pose challenges for energy accumulation and detection for moving targets. Additionally, range migration and Doppler shift caused by target motion during long-time integration must be addressed. This letter proposes a coarse-to-fine Doppler parameter search method for long-time coherent integration of maneuvering targets. In the coarse parameter search stage, the first-order Doppler phase modulation is removed within and between pulses. Pulse compression and range migration correction are accomplished using a unified range compensation filter. In the fine parameter search stage, quadratic Doppler phase modulation is compensated, and the fast Fourier transform (FFT) is used to refine the Doppler search step size efficiently. An experiment using GPS L1 signal as the illuminator is conducted, successfully detecting a ship target. The comparison results indicate that the proposed method significantly improves implementation efficiency without the loss of coherent integration gain.