Abstract
The MeerKAT radio telescope consists of 64 Gregorian-offset antennas located in the Karoo in the Northern Cape in South Africa. The antenna system consists of multiple subsystems working collaboratively to form a cohesive instrument capable of operating in multiple modes for defined science cases. We focus on the channelizing subsystem (F-engine), the correlation subsystem (X-engine), and the beamforming subsystem (B-engine). In the wideband instrument mode, the channelizing can produce 1024, 4096, or 32,768 channels with correlation up to 64 antennas. Narrowband mode decomposes sampled bandwidth into 32,768 channels. The F-engine also performs delay compensation, equalization, quantization, and grouping and ordering. The X-engine provides both correlation and beamforming computations (independently). This document is intended to be a stand-alone entity covering the channelizing, correlation, and beamforming processes for the MeerKAT radio telescope. This includes data reception, pre- and post-processing, and data transmission.
Highlights
The MeerKAT radio telescope is a Square Kilometre Array (SKA) precursor instrument, a 64-element interferometer using Gregorian-offset antennas, built by South African Radio Astronomy Observatory (SARAO) in South Africa’s Karoo Desert.[1]The MeerKAT digital back-end uses an FX-style correlation process
The RF signal will have undergone a phase change of 2πfRFτi where τi 1⁄4 τr;i þ τg;i by the time it reaches the F-engine input. If both coarse and fractional delay were applied at an intermediate frequency (IF), we are left with a remaining local oscillator (LO) fringe rotational phase φfringe 1⁄4 2πfLOτi, where a constant term has been omitted since it is fixed per frequency and will be removed by baseline calibration
The direct digital synthesizer (DDS) is constructed around multiple cos–sin look up tables (LUTs), stored in BRAM on the field programmable gate array (FPGA)
Summary
The MeerKAT radio telescope is a Square Kilometre Array (SKA) precursor instrument, a 64-element interferometer using Gregorian-offset antennas, built by SARAO in South Africa’s Karoo Desert.[1]. The MeerKAT digital back-end uses an FX-style correlation process. The F in FX represents the channelization process and is performed by a logical device known as an F-engine. The X represents cross-correlation performed in the frequency domain. The B-engine performs beamforming and is colocated within the processing silicon of the X-engine but logically distinct from it. The B-engine receives a duplicate data feed from the X-engine and processes independently from the X-engine correlation process. Both the B-engine and the X-engine share common networking logic. This paper will cover both the F-engine and X-engine systems in logical processing order collectively known as a correlator-beamformer (CBF)
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