A UHF Multimode Array Feed for the Westford Radio Telescope

Abstract

A novel UHF Multimode Array Feed (MMAF) has been created for MIT’s Westford Radio Telescope. The MMAF is a dual-linear focal plane array installed concentrically with the existing QRFH feed on the telescope, enabling a combined system capable of transmit or receive on UHF radar and satcom frequencies simultaneous with reception from 2 GHz to 14 GHz. To demonstrate the capabilities of the MMAF, real-time calibration and beamforming techniques are developed, and the MMAF is used to adaptively steer the beam of the Westford Telescope to follow the downlink signal from MITs DeMi cubesat while matching its received polarization and nulling interferers.

To the author’s knowledge, the MMAF represents the first demonstrated use of a concentric eleven style feed topology to extend the capabilities of a preexisting antenna feed system. The design approach is not specific to Westford, and similar designs can be created to add low frequency coverage to any microwave feed. This brings the possibility of extending the operating frequency range of many other large antenna systems currently in operation worldwide.

Further, the MMAF represents a first step towards a new class of ultra-wideband hybrid feed combining log-periodic elements with a multimodal waveguide feed such as a QRFH. To this end, a possible approach to design a UWB-MMAF using metamaterials is suggested.