# 125-211 GHz Low Noise MMIC Amplifier Design for Radio Astronomy

## TL;DR

This paper presents a novel 125-211 GHz low noise amplifier using advanced HEMT technology, achieving superior noise performance and bandwidth, potentially replacing traditional SIS mixers in radio astronomy receivers.

## Contribution

The design demonstrates a high-frequency, wide-bandwidth MMIC LNA with record low noise temperature, challenging the dominance of SIS mixers in sub-THz radio astronomy applications.

## Key findings

- Achieved noise temperature below 58 K across 125-211 GHz
- Average noise temperature of 38.8 K at 170 GHz
- Successful fabrication of a wide-bandwidth, high-performance LNA

## Abstract

To achieve the low noise and wide bandwidth required for millimeter wavelength astronomy applications, superconductor-insulator-superconductor (SIS) mixer based receiver systems have typically been used. This paper investigates the performance of high electron mobility transistor (HEMT) based low noise amplifiers (LNAs) as an alternative approach for systems operating in the 125 - 211 GHz frequency range. A four-stage, common-source, unconditionally stable monolithic microwave integrated circuit (MMIC) design is presented using the state-of-the-art 35 nm indium phosphide HEMT process from Northrop Grumman Corporation. The simulated MMIC achieves noise temperature (Te) lower than 58 K across the operational bandwidth, with average Te of 38.8 K (corresponding to less than 5 times the quantum limit (hf/k) at 170 GHz) and forward transmission of 20.5 +/- 0.85 dB. Input and output reflection coefficients are better than -6 and -12 dB, respectively, across the desired bandwidth. To the authors knowledge, no LNA currently operates across the entirety of this frequency range. Successful fabrication and implementation of this LNA would challenge the dominance SIS mixers have on sub-THz receivers.