Steered Conformal Array for the Rotating Airframe Missile

Abstract

Recent reallocation of L-Band spectrum that was heavily used to support Aeronautical Mobile Telemetry has led to a significant spectrum access shortfall. The DoD was authorized to use portions of C-Band to address this shortfall. One system directly affected by this is the Rotating Airframe Missile (RAM). An antenna system for the RAM is being developed that will switch between sections of a conformal antenna array, activating small subarrays at any given moment. This approach minimizes the variation in gain for any particular aspect angle as the RAM rotates, reducing the required transmit power. The antenna aperture is designed using GTRI’s fragmented aperture technology to provide a very efficient radiator in the space provided. Small subarrays of this conformal array are passively combined directly behind the aperture. Inside the RAM body there are two actively controlled switches that alternatingly switch which subarrays are fed, always ensuring that the two adjacent subarrays pointing in the desired beam direction are active. These switches are controlled by an on-board algorithm using data captured from the RAM’s Inertial Measurement Unit (IMU) and rate sensors to determine the attitude of the missile at all times and dictate which subarrays should be active.