Reconfigurable 4-Arm Spiral Antenna for Dual Polarization

4-arm spiral antennas have a wide bandwidth and circular polarization when operating in mode 1 (fundamental mode). Switching to mode 3 (to obtain opposite circular polarization) dramatically reduces the antenna bandwidth compared to mode 1. In this work we reduce the arm sizes of the spiral (for example with RF switches) to increase the bandwidth of mode 3 at the higher mode 1 frequencies. In this way the antenna has the same wide bandwidth for both polarizations (modes).