# Gain Stabilization for Radio Intensity Mapping using a Continuous-Wave Reference Signal

## TL;DR

This paper presents a gain stabilization method for radio astronomy receivers using a continuous-wave reference signal, significantly reducing noise and improving sensitivity in radio intensity mapping.

## Contribution

The paper introduces a gain stabilization technique employing a continuous-wave reference signal tracked in a single spectrometer channel, effective for digital back-end receivers with high spectral resolution.

## Key findings

- Significant reduction of 1/f noise and knee frequency.
- Effective gain stabilization with minimal impact on sensitivity.
- Method suitable for high-resolution digital radio receivers.

## Abstract

Stabilizing the gain of a radio astronomy receiver is of great importance for sensitive radio intensity mapping. In this paper we discuss a stabilization method using a continuous-wave reference signal injected into the signal chain and tracked in a single channel of the spectrometer to correct for the gain variations of the receiver. This method depends on the fact that gain fluctuations of the receiver are strongly correlated across the frequency band, which we can show is the case for our experimental setup. This method is especially suited for receivers with a digital back-end with high spectral resolution and moderate dynamic range. The sensitivity of the receiver is unaltered except for one lost frequency channel. We present experimental results using a new 4-8.5 GHz receiver with a digital back-end that shows substantial reduction of the 1/ f noise and the 1/ f knee frequency.