# CHIME FRB: An application of FFT beamforming for a radio telescope

## TL;DR

This paper presents FFT beamforming techniques implemented on GPU for the CHIME radio telescope, enabling wide-field, high-resolution searches for Fast Radio Bursts with improved localization capabilities.

## Contribution

The paper introduces a hybrid FFT beamforming pipeline for CHIME, achieving large sky coverage and high angular resolution for FRB detection and localization.

## Key findings

- Synthesized 256 FFT beams covering ~250 sq. degrees.
- Achieved spectral resolution of 24 kHz and time cadence of 0.983 ms.
- Implemented zero-padding for chromatic beam alignment across 400-800 MHz.

## Abstract

We have developed FFT beamforming techniques for the CHIME radio telescope, to search for and localize the astrophysical signals from Fast Radio Bursts (FRBs) over a large instantaneous field-of-view (FOV) while maintaining the full angular resolution of CHIME. We implement a hybrid beamforming pipeline in a GPU correlator, synthesizing 256 FFT-formed beams in the North-South direction by four formed beams along East-West via exact phasing, tiling a sky area of ~250 square degrees. A zero-padding approximation is employed to improve chromatic beam alignment across the wide bandwidth of 400 to 800 MHz. We up-channelize the data in order to achieve fine spectral resolution of $\Delta\nu$=24 kHz and time cadence of 0.983 ms, desirable for detecting transient and dispersed signals such as those from FRBs.