Directional Radar-Embedded Communications Based on Hybrid MIMO and Frequency Diverse Arrays

In this paper, we explore directional radar-embedded communications where the embedded information symbols is transmitted to the desired receiver located in pre-specified direction(s) while simultaneously lowering the probability of interception by undesired receiver(s). We devise a two-dimensional (i.e., range and angle) directional modulation (DM) scheme for information symbols embedded into the radiation of frequency diverse multiple-input multiple-output (FD-MIMO) radar. In FD-MIMO array, orthogonal waveforms are adopted for radar functionality. We implement the communication operation by using Bat optimization algorithm for DM which optimized the phase shifters continuously with time. Thus, each pair of symbols is designed and embedded in each orthogonal waveform. When the phase shifters are altered, the steering vector of the FD-MIMO radar is also changed according to the angle and range values specified. The hybrid FD-MIMO enjoys the advantages of MIMO in spatial diversity and the frequency diverse array in range-dependent coherent directional gain. Moreover, satisfactory bit error rate for communication operation is achieved.