# The Design and Implementation of a ROACH2+GPU based Correlator on the Tianlai Dish Array

## TL;DR

This paper presents a scalable, FPGA-GPU based digital correlator system for the Tianlai Dish Array, enabling efficient 21cm intensity mapping with tested laboratory and real-world performance.

## Contribution

It introduces a novel FX correlator design combining ROACH2 FPGA boards and GPUs for radio astronomy applications.

## Key findings

- Successful laboratory testing of the correlator system.
- Effective real-world deployment during observations.
- Demonstrated scalability and performance in 21cm surveys.

## Abstract

The digital correlator is a crucial element in a modern radio telescope. In this paper we describe a scalable design of the correlator system for the Tianlai pathfinder array, which is an experiment dedicated to test the key technologies for conducting 21cm intensity mapping survey. The correlator is of the FX design, which firstly performs Fast Fourier Transform (FFT) including Polyphase Filter Bank (PFB) computation using a Collaboration for Astronomy Signal Processing and Electronics Research (CASPER) Reconfigurable Open Architecture Computing Hardware-2 (ROACH2) board, then computes cross-correlations using Graphical Processing Units (GPUs). The design has been tested both in laboratory and in actual observation.