Projects:2018s1-177 Radio astronomy with software-defined radio

Project name

Radio astronomy with software-defined radio

Project introduction

Background

Radio astronomy is a combination of electronic field and astronomy. Because the light wave cannot penetrate interstellar dust, optical astronomy has its limitation on the galaxy level observation. However, from 1932, scientists started to use radio frequency system to catch the signal from celestial bodies. Some frequency bands are able to penetrate across the whole galaxy. Therefore, antennas can be used in astronomy observation as radio telescopes.

Software defined radio (SDR) devices has been developed in the last ten years. It provides convenience for students or electronics enthusiasts to build RF receiving system. Graphics processing unit (GPU) is a professional parallel structure processor which becomes more and more popular in recent years, for some algorithm with redundant computations. This project shows a promising application in radio astronomy which combines SDR and GPU.

Due to the atomic transition of electrons, the "spin-flip" line of hydrogen emits from the universe. The frequency of these hydrogen lines is 1420. 406 MHz and they were firstly discovered by Ewen and Purcell in 1951. In recent years, as the emergence of SDR --- a new and relatively inexpensive device, amateurs can re-explore the spectrum of the hydrogen line with a small budget.

System overview

This project aims to design and build up a system to observe the spectrum of hydrogen line from the universe. The system consists of two parts --- radio frequency (RF) and signal processing.

The RF part consists of a dish antenna, a low-noise amplifier, a band-pass filter, and a SDR device.

For signal processing part, a new signal processing method, PFB algorithm, is used to replace Welch’s method for a lower spectral leakage in power spectrum estimation. A mathematical analysis from plain DFT to PFB algorithm is shown. The spectral leakage of plain DFT, windowed DFT and PFB is compared, which shows a huge improvement of the PFB result. Then, we gives an answer that when the frequency of the sinusoid interference is close to the hydrogen line frequency band, the anti-interference performance of PFB algorithm is definitely better than Welch’s method. This algorithm is implemented on GPU, with a parallel computing structure.

Motivation

This is a follow-up project. The experiment results from last year have some drawbacks that need to be improved in this year. Four major drawbacks are listed as follows. 1) Spurs exist in the power spectrum density plots. 2) Weak signals could be swamped. 3) The resolution is not high enough. 4) The system cannot process data in real time.

Objectives

According to the limitations of last year's project, the objective of this year's project is to improve the performance of the system which has been built by the students in last year. The first goal is to reduce the spectral leakage in power spectrum estimation, so as to to improve signal resolution and reduce the effects of radio interference. The second goal is to accelerate the calculation, so as to estimate power spectrum in real time. As a solution, the PFB algorithm is proposed with parallel computing acceleration.

Team members

Hongwen Qu, Hanwen Chang

Supervisors

Dr Withawat Withayachumnankul, Dr Brian Ng