Phase Synchronization of Bistatic Radar by Exploiting the Urban Scene

This paper proposes a technique to synchronize networked radar in a typical urban environment using low cost commercial-off-the-shelf (COTS) oscillators, augmented by signal processing. A method, termed Multiple Reference Phase Correction (MRPC), is presented that extracts oscillator phase from a collection of reference targets simultaneously, including the direct line-of sight signal and scattering from large stationary objects. Significant improvement in the coherency of the bistatic radar via background measurements and target measurements is demonstrated. The paper uses and develops various approaches to measure and quantify radar coherence. The methods used to demonstrate coherence are: (i) single side-band (SSB) phase power spectral density (PSD) plots, (ii) Time/range error estimates via unwrapped bistatic phase measurements and (iii) coherent integration loss. Phase error measurements have demonstrated a synchronization accuracy to within 7.2 degrees over 140 s, resulting in a range drift of only 2 mm. The radar noise floor is also measured and the phase noise is shown to be reduced by 20 dB at a 10 Hz offset frequency. An analysis of real-world target detectability, using controlled drones as targets, demonstrates an average signal-to-noise ratio (SNR) improvement of more than 4.5 dB within the obtained data set.