Frequency Selective Surface Loaded Antenna for Direct Antenna Modulation

A reconfigurable antenna loaded with Frequency Selective Surfaces (FSS) to achieve direct antenna phase modulation is presented and simulated. Placing FSS with integrated varactor diodes into a monopole-fed cavity allows control of the transmitted phase of a carrier signal with a bias voltage. As such, Direct Antenna Modulation (DAM) can be achieved, producing a phase modulator that can be included in a low complexity transmitter. Simulation shows such an antenna can achieve QPSK modulation with between 3.5dB and 4.5dB magnitude variation between constellation points with acceptable phase stability with radiation angle in the antenna 3dB beamwidth.