Optimised Multiport Amplifiers for Wideband Multi-Beam Satellites

Abstract

This paper provides an analysis of Multiport Amplifiers (MPAs), specifically 8 port MPAs that may have use in Wideband Multi-beam payloads operating at Ku or Ka-band. These typically use Single Feed per Beam (SFB) designs which provide a contiguous set of up to 100 narrow beams, or more over a defined area. MPAs are an attractive solution to SFBs, since they potentially offer a high degree of flexibility in allocating power to beam. MPAs have successfully been applied at L and S-band, but present highly challenging problems at Ku/ Ka-band at which wavelengths are an order of magnitude shorter. This paper examines the impacts of equipment phase/amplitude mismatches on MPA performance, primarily on isolation. Using a simulation model for a Ka-band broadband satellite system the paper then goes on to determine the impacts of MPA isolation on the systems performance, and establishes target phase/amplitude tracking requirements of an MPA for use within such systems. The simulation results indicate that an MPA isolation of ≥24dB should be targeted for maximum spectral efficiency. Beyond 24dB there are no further significant gains and efficiency equals that of an SFB with a conventional HPA scheme.