Analysis and Mitigation of the Reflected Power on an S-band Planar Phased Array Antenna Transmitting in a Wet Spherical Radome

An active S-band dual-polarized multifunction phased array radar, the Advanced Technology Demonstrator (ATD), has recently been developed for weather sensing and aircraft surveillance. The ATD is a 4-m diameter active electronically scanned array (AESA) with 4864 transmit/receive (T/R) modules was installed in a spherical radome. Simulations and a novel phased array measurement technique have been explored to assess the impact of high reflectivity from a wet radome during rain that can potentially induce voltages exceeding the transmit amplifier breakdown voltage. Simulations show that when the radome surface is wet and highly reflective due to lack of hydrophobicity, certain electronic steering angles sum to a large reflected signal focused on the array face. The measurement technique uses array elements radiating one at a time to illuminate the radome in dry and wet conditions, and uses superposition to quantify the received signal power in a reference antenna on the face of the array. This measurement technique is being used prior to high-power phased array radar operation to monitor the magnitude of reflections and help avoid element transmit amplifier failures.