Practical Limits in the Sensitivity-Linearity Trade-off for Radio Telescope Front Ends in the HF and VHF-low Bands

TL;DR

This paper analyzes the inherent trade-offs between sensitivity and linearity in radio telescope front ends operating in the HF and VHF-low bands, providing guidelines for optimizing amplifier design.

Contribution

It offers a detailed analysis of the sensitivity-linearity trade-off for MMIC amplifiers in low frequency radio telescopes, including practical design insights and experimental validation.

Findings

Trade-off curves for sensitivity and linearity in MMIC amplifiers

Validation of analysis with hardware measurements

Design recommendations for improved linearity in front ends

Abstract

Radio telescope front ends must have simultaneously low noise and sufficiently-high linearity to accommodate interfering signals. Typically these are opposing design goals. For modern radio telescopes operating in the HF (3-30 MHz) and VHF-low (30-88 MHz) bands, the problem is more nuanced in that front end noise temperature may be a relatively small component of the system temperature, and increased linearity may be required due to the particular interference problems associated with this spectrum. In this paper we present an analysis of the sensitivity-linearity trade off at these frequencies, applicable to existing commercially-available monolithic microwave integrated circuit (MMIC) amplifiers in single-ended, differential, and parallelized configurations. This analysis and associated findings should be useful in the design and upgrade of front ends for low frequency radio telescopes. The analysis is demonstrated explicitly for one of the better-performing amplifiers encountered in this study, the Mini-Circuits PGA-103, and is confirmed by hardware measurements. We also present a design based on the Mini-Circuits HELA-10 amplifier, which is better-suited for applications where linearity is a primary concern.