Universal Millimeter-Wave Radar Front End

A quasi-optical front end allows any arbitrary polarization to be transmitted by controlling the timing, amplitude, and phase of the two input ports. The front end consists of two independent channels — horizontal and vertical. Each channel has two ports — transmit and receive. The transmit signal is linearly polarized so as to pass through a periodic wire grid. It is then propagated through a ferrite Faraday rotator, which rotates the polarization state 45°. The received signal is propagated through the Faraday rotator in the opposite direction, undergoing a further 45° of polarization rotation due to the nonreciprocal action of the ferrite under magnetic bias. The received signal is now polarized at 90° relative to the transmit signal. This signal is now reflected from the wire grid and propagated to the receive port.