Robust sidelobe amplitude and phase modulation for dual‐function radar‐communications

In this paper, we address the topic of sidelobe modulation in dual‐function radar‐communication platforms, which consists in embedding communication messages into the radar emissions by varying the phase and/or amplitude values of the radar transmit beampattern at a receiver direction within the sidelobe. An advantage of this type of communication link is that it is inherently secure as the communication symbol is transmitted correctly only at a specific direction. However, this advantage may become a major problem, causing an expressive decrease in performance, if the real receiver position does not match exactly the predefined one. This scenario easily arises from the relative movement between the radar and the receiver. We propose 2 original methods for embedding the sidelobe amplitude/phase modulation into the radar transmit beampattern that have simple closed‐form equations and are robust to small angular errors in the receiver's direction. We also propose a noncoherent signaling strategy for sidelobe phase modulation and present its analytical bit error rate expression for the binary case. Simulation results and comparisons illustrate the advantages of the proposed techniques.