Theoretical Analysis of Astronomical Phased Arrays

TL;DR

This paper provides a theoretical framework for analyzing low-noise astronomical phased arrays using frame theory, enabling assessment of their imaging capabilities, noise characteristics, and image reconstruction methods without assuming orthogonality.

Contribution

It introduces a novel application of frame theory to phased array analysis, allowing comprehensive evaluation of their imaging and noise properties without orthogonality assumptions.

Findings

Frame theory unambiguously assesses array observation capabilities.

Analysis of noise and fluctuations for any spatial coherence state.

Framework supports classical and photon-counting statistics.

Abstract

Low-noise phased arrays are essential for the next generation of microwave and submillimetre wave astronomy. We analyze their behaviour from a functional perspective, and show that their operation is intimately related to the mathematical theory of frames. No assumptions are made about the orthogonality or linear independence of the synthesised beams. Frame theory allows an unambiguous assessment of whether the outputs of an array can be used to observe a field or brightness distribution within a given class. Image reconstruction is carried out using dual beams. We identify the natural modes of phased arrays, and carry out an analysis of noise. The scheme allows the expectation values, the mean-square fluctuations, and the correlations between fluctuations at the output ports of a phased array to be determined for a source in any state of spatial coherence. Both classical and photon-counting statistics are included. Our model is conceptually powerful, and suggests many simulation and image recovery techniques.