Design of the radio front end of a UHF phased array system

Abstract

In recent years, there has been a growing interest in the deployment of satellite constellations in low Earth orbits. These groups of satellites orbit the Earth in a synchronised manner, providing vastly improved coverage over what could be achieved with a single satellite. These constellations provide a unique challenge, as the base station communicating with them must be able to track the satellites as they pass overhead. Typically this was achieved by using actuators to physically move the base station’s antenna, which presents numerous issues with cost and reliability. In contrast, phased array antennas provide a faster, more reliable method to steer the radio wave beam. Each antenna element within the array is connected to its own independent phase shifter, altering the phase relationship of the radio waves such that those exiting from different element interfere constructively with each other, strengthening them and thus vastly improving the antenna array’s gain. By carefully altering the phase relationship of the individual antenna elements, the beam can also be steered to any direction. This project involves the design, manufacturing and characterisation of a radio front-end prototype for use in a multichannel UHF phased array system. The array’s main aim is to communicate with the University of Malta’s satellite constellation, consisting of a number of UOMBSat-1 PicoSatellites. As a result, the prototype must adhere to the strict requirements presented by this application. The design end includes an in-depth analysis of current phased array systems, from which a suitable architecture was identified. After carefully selecting and characterising the appropriate components that would be used to construct the prototype through the use of custom evaluation boards, the finalised prototype was designed, constructed and tested to obtain its performance characteristics. The finalised design presents a highly scalable, accurate and flexible prototype that is not only limited to operation within the UHF band, but can be used over a wide range of frequencies.