Recent results in MIMO over-the-horizon radar

A demonstration of multiple-input multiple-output over-the-horizon radar is presented. Transmitter signal beam- forming on a multi-element array has been created, not conventionally before transmission at the transmitter facility, but, after radar signal transmission, skywave propagation, target scattering, return signal propagation, and reception using an over-the-horizon radar receiver. Transmitter beam-patterns have been created simultaneously from the signal received at two widely separated locations. The first is within line-of-sight propagation of the end-point of the one-hop ionospheric transmitter to target path, and the second from the signal received at the end-point of the two-hop ionospheric transmitter to target to receiver propagation path. These beampatterns are shown to be practically identical. They reveal the target radar return signal direction-of-departure at the transmitter. This example of a-posteriori transmitter beamforming suggests that it will be possible to create multiple simultaneous adaptive range dependent transmitter beams with an appropriately designed over-the-horizon radar. This has several applications including for the mitigation of Doppler-spread clutter.