Front end concept development for a next generation Very Large Array

Abstract

The ngVLA Front End concept has six separate cryogenically-cooled, dual polarization receiver bands, each with an integral feed horn. The upper five bands (2–5) are co-located within a single compact cryostat, while the lowestfrequency band (1) occupies a second cryostat of similar volume and mass. For optimum performance at higher frequencies, waveguide-bandwidth (~1.66:1) receivers are used above 12 GHz, with axially-corrugated feed horns for high aperture efficiency and low spillover. Below 12 GHz, wideband (~3.5:1) receivers and feed horns are used to reduce receiver count, total mass, and cost, with modest trades in sensitivity. Ongoing work includes development of wideband feed horns, windows, low-noise amplifiers (LNAs) and couplers for Bands 1–2, design or procurement of orthomode transducers (OMTs) and LNAs for Bands 3–6, and detailed mechanical design of the conceptual Front End cryostats and receiver/feed/window subassemblies. Accurate simulations of sensitivity (AEFF/TSYS) versus frequency and antenna elevation will be shown, based on modeled or measured component data and the simulated performance of the antenna optics.