Superdirective mode selective OTHR with time-division MIMO beamforming

This paper proposes superdirective adaptive mode-selective processing in oversampled 2D transmitting (Tx) and receiving (Rx) antenna arrays, enabled by MIMO radar technology, for skywave OTHR applications. The actual reactive power in Tx antenna arrays is controlled by considering two main principles: (1) avoiding extreme steering angles in conventionally beamformed (for a single waveform) sub-arrays and (2) using time-division MIMO waveform sets with no simultaneous transmissions of different (orthogonal) MIMO waveforms from TX array phase centers separated by less than half the radar wavelength. We consider the propagation modes as per [1] to demonstrate the utility of the proposed technique for Tx and Rx antenna arrays with apertures significantly smaller than those introduced in [1].