Multi-band Radio Astronomy Receivers: A Concept Exploration

Concurrent multi-band observations are a cornerstone of future radio astronomy and very-long baseline interferometry (VLBI). While some telescopes can incorporate multiple independent receivers with a shared optical path (SOP) for concurrent observation, others require single feeds and separate RF front-ends to cover multiple bands. We examine the state-of-the-art in feeds, couplers, isolators, low-noise amplifiers (LNAs) and downconverters, to determine the relative value of wideband RF front-ends vs. receivers with multiple, discrete operating bands. It is found that the implementation of wideband feeds and isolators do not offer significant drawbacks to their multi-band equivalents, but that concurrent multi-band LNAs and noise couplers may offer some advantages over wideband LNAs. While broadband mixers are readily available, different downconversion and intermediate frequency (IF) processing approaches are highlighted, which may be customized to the specific bands of interest.