A dual function radar-communications system using sidelobe control and waveform diversity

In this paper, we develop a new technique for dual-function radar-communications in a transmit multi-sensor array where information embedding is achieved using sidelobe control in tandem with waveform diversity. A set of Q orthogonal waveforms is exploited to embed a sequence of Q bits during each radar pulse. All waveforms are transmitted simultaneously where one bit is embedded in each waveform. We design two transmit weight vectors to achieve two distinct transmit power distribution patterns which share the same main radar beam but have different sidelobe levels towards the communication direction. The receiver interprets the bit associated with a certain waveform as binary information based on whether that waveform is radiated over the transmit beam associated with the first or the second weight vector. The proposed technique enables information delivering to a single or multiple communication directions located outside the mainlobe of the radar. The communication message has low probability of intercept from directions other than the preassigned communication directions. Additionally, the waveform diversity enables the radar to operate in multiple-input multiple-output (MIMO) mode. The performance of the proposed technique is investigated in terms of the bit error rate (BER).