A hybrid SDR-GPU receiver for a low-frequency array in radio astronomy

The Mauritius Deuterium Telescope (MDT) is an upcoming low-frequency array being built in Mauritius to observe the Deuterium hyperfine line at 327.4 MHz. This project is an opportunity to develop new techniques in radio astronomy considering the advent of the Square Kilometre Array in a few years time. The design of the MDT array targets a low-cost hybrid system consisting of Software Defined Radios (SDR) as the analogue receiver and digitiser, while a gaming Graphics Processing Unit (GPU) is used to implement the digital processing pipeline. We present the design and layout of the instrument. A polyphase filterbank (PFB) is implemented in parallel on the GPU. For an 11-station array, the PFB kernel has a computational throughput of 39.8 GiB/s. Since processing and copying can be overlapped, the latency of the processing kernels can be hidden behind the data copying to GPU memory; effectively establishing an input rate limit around 12 GiB/s due to the PCIe x16. Still, this will allow the hybrid SDR-GPU pipeline to perform real-time data acquisition and processing for the MDT. Finally, we present results from tests with real data from an FM antenna at 327 MHz.