Effect Analysis of Spatial Modulation on Clutter Mitigation for Joint RadCom Systems and Solutions

The increasing competition over the scarce spectrum has intensified the problem of spectrum congestion. Joint radar-communication (RadCom) systems, where radar and communication systems are integrated into one platform, have recently commanded significant attention for their ability to efficiently utilize the limited spectral resources. Major challenges of joint RadCom systems include shared waveform design, leading to the proposal of different signalling strategies. Among these, spatial modulation embeds random communication information into the complex beampattern of the shared waveform. The variation of transmit beampattern in a coherent processing interval adversely affects the Doppler coherency of clutter, in turn impacting the radar sensitivity. In this work, we analyse quantitatively the effect of beampattern variation on clutter modulation for joint RadCom systems. Then, we propose a calibrated matched filter based on subspace projection by fully utilizing the properties of spatial modulation. Simulation results demonstrate that the calibrated matched filter is effective at mitigating ground clutter without affecting the dual functions of joint RadCom systems.