MWA tied-array processing III: Microsecond time resolution via a polyphase synthesis filter

TL;DR

This paper introduces a high time resolution observing mode for the Murchison Widefield Array using a polyphase synthesis filter, enabling microsecond-scale polarimetric observations with minimal signal loss.

Contribution

It presents a novel high time resolution mode utilizing a polyphase synthesis filter to improve temporal resolution in MWA observations.

Findings

Achieves ~0.8 μs time resolution with up to 30.72 MHz bandwidth.

Quantifies S/N loss, not exceeding -0.65 dB in typical conditions.

Validates system by observing pulsars with microsecond structures.

Abstract

A new high time resolution observing mode for the Murchison Widefield Array (MWA) is described, enabling full polarimetric observations with up to 30.72 MHz of bandwidth and a time resolution of ~0.8 $\mu$s. This mode makes use of a polyphase synthesis filter to "undo" the polyphase analysis filter stage of the standard MWA's Voltage Capture System (VCS) observing mode. Sources of potential error in the reconstruction of the high time resolution data are identified and quantified, with the S/N loss induced by the back-to-back system not exceeding -0.65 dB for typical noise-dominated samples. The system is further verified by observing three pulsars with known structure on microsecond timescales.