Noise Temperature of Phased Array Radio Telescope: The Murchison Widefield Array and the Engineering Development Array

Abstract

This article presents a framework to compute the receiver noise temperature ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm {rcv}}$ </tex-math></inline-formula> ) of two low-frequency radio telescopes, the Murchison Widefield Array (MWA), and the Engineering Development Array (EDA). The MWA was selected because it is the only operational low-frequency square kilometer array (SKA) precursor at the Murchison Radio astronomy Observatory, while the EDA was selected because it mimics the proposed SKA-low station size and configuration. It will be demonstrated that the use of an existing power wave-based framework for noise characterization of multiport amplifiers is sufficiently general to evaluate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm {rcv}}$ </tex-math></inline-formula> of phased arrays. The calculation of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{\mathrm {rcv}}$ </tex-math></inline-formula> was done using a combination of measured noise parameters of the low-noise amplifier (LNA) and simulated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameters of the arrays. The calculated values were compared to measured results obtained via astronomical observation and both results are found to be in agreement. Such verification is lacking in current literature. It was shown that the receiver noise temperatures of both arrays are lower when compared to a single isolated element. This is caused by the increase in mutual coupling within the array which is discussed in depth in this article.