Space-Time Array Radar Based on Direction Modulation: Concept and Analysis

Direction modulation is a modulation technique where the beam direction changes with the transmission time, providing beam scanning within the pulse transmission time for array antennas. For array radars, intra-pulse beam scanning is a degree of freedom that has not been fully utilized but can be exploited. Based on this degree of freedom, this paper proposes the concept of space-time array (STA) radar, which refers to a radar where the transmit beam in the spatial dimension varies flexibly in the temporal dimension (including intra-pulse and inter-pulse). The STA radar achieves coverage of the region of interest through intra-pulse beam scanning during transmission and covers the same region through multi-beam reception. Both transmission and reception use high-gain beams, sharing a single array antenna through the T/R components. A significant advantage of STA radar is that it enables array radars to perform multiple radar functions simultaneously, without being constrained by the limitation of traditional phased array radars that require multiple functions to be executed sequentially in time. This paper presents the concept, principles, simulations, and potential advantages of STA radar. STA radar represents an approach to achieving important radar capabilities that are not easily achievable with current array radar architectures.