On the Synchronization of Uncoupled Multistatic PMCW Radars

Abstract

Radar networks and multistatic synthetic aperture radars (SARs) allow overcoming the limitations of single radar sensors. However, a good synchronization of the radar sensors is crucial to avoid performance loss due to phase noise and frequency offsets. While this is usually done via cables or dedicated synchronization signals, digital radars allow for new techniques. This work proposes a new concept for the synchronization of phase-modulated continuous wave (PMCW) radars. The synchronization is performed solely by digital signal processing on the receiver side, adapting techniques known from digital communications. It mitigates effects caused by incoherency, which are phase noise, carrier frequency offsets and phase deviations of the local oscillator (LO), and sampling frequency offsets. At first, the impact of these effects is mathematically derived and analyzed in detail. Then, the proposed synchronization concept is presented, and its performance is thoroughly evaluated. Very good results are obtained not only in simulations but also in measurements with a 77-GHz radar demonstrator.

Constellation Estimation, Coherent Signal Processing, and Multiperspective Imaging in an Uncoupled Bistatic Cooperative Radar Network

“…In the correction chain, the estimation of the frequency offset that causes the time drift δ t is estimated first. The linear drift of the beat frequency (see Section II) is applied to the LoS beat frequency models in (23) and (24). The frequencies are linear functions of the slow time index k with a slope…”

“…The results show that even for the strong scatter of 5 the phase noise skirt, which covers the weak target, is amply compensated for. A similar approach is proposed in [23] to compensate for the phase noise due to a reference link assumed to be considerably stronger than the target reflection. However, the scatterer's influence on performance is not discussed.…”

“…In the presence of strong phase noise, which is the case for bistatic radars with independent local oscillators (LOs), the noise skirt can be superimposed, concealing targets with low RCSs [22]. An uncoupled bistatic radar network with phase noise compensation is introduced in [23], achieving very good compensation performance in a SISO setup with antennas placed close together. However, a drawback of all these approaches is that they are suitable only for wireless locating or perform imaging in a bistatic constellation with the radar nodes fixed on a common frame and are thus not capable of multiperspective imaging.…”