Coherent Integration for Passive Continuous Wave Radar Using Cross Ambiguity Function

The cross ambiguity function enables coherent phase accumulation in passive continuous wave radar systems by correlating reference and surveillance signals. This method employs a two-dimensional signal processing technique that computes the correlation between time-delayed and Doppler-shifted versions of the transmitted and received signals. The implementation typically involves: - Generating complex signal representations for both reference and target echo paths - Applying sliding window correlation algorithms across time and frequency domains - Calculating the ambiguity surface using Fourier-based processing for efficient computation Key algorithm components include: - Reference signal reconstruction from opportunistic illuminators (e.g., FM radio, digital TV signals) - Adaptive filtering to mitigate direct path interference - Phase coherence maintenance through Doppler compensation techniques This approach enhances target detection sensitivity by integrating weak echoes over extended periods while maintaining phase relationships. The cross ambiguity function processing effectively resolves target range and velocity parameters simultaneously, making it particularly valuable for passive radar applications where transmitter parameters cannot be controlled. Practical implementations often utilize optimized FFT operations and parallel processing architectures to handle the computational complexity of real-time ambiguity function calculations.