Research on Channelization Techniques of Radio Astronomical Wideband Signal with Oversampled Polyphase Filter Banks

Abstract

Digital channelization decomposes a wideband signal into multiple adjacent sub-bands using Parallel Technology. Channelization can effectively reduce the pressure on the radio astronomy digital backends system and make wideband signal processing possible. Aiming at the problems of signal attenuation at sub-band edge, spectral leakage and aliasing encountered in wideband signal channelization, algorithms to reduce the problems are studied. We design a Critically Sampled Polyphase Filter Bank (CS-PFB) based on the Finite Impulse Response (FIR) digital filter with a Hamming Window and systematically analyse the frequency response characteristics of the CS-PFB. Based on the channelized structure of the CS-PFB, an oversampled polyphase filter bank (OS-PFB) is designed by data reuse, and the filtering frequency response characteristics of CS-PFB and OS-PFB are compared and analyzed. Using the wideband baseband data generated by the CASPSR backends of Parkes, we implement sub-band division and 16-band output of these data based on the 2× oversampling OS-PFB, and the problem of spectrum inversion in the sub-bands is corrected. After removing 25% of redundant data in the head and tail of each sub-band, we recombine the sub-bands into a wideband. The wideband signal is almost identical to the original observed signal. Therefore, the experimental results show that OS-PFB can eliminate signal attenuation at the sub-band edge, spectrum leakage and aliasing caused by channelization. For the 400MHz baseband data of J0437-4715, we compare the pulse profile obtained from the original baseband data with the pulse profile obtained after the channelization and recombination. The phase and amplitude information of the pulse profiles are consistent, which verifies the correctness of our channelization algorithm.

UWLPIPE: Ultra-wide Bandwidth Low-frequency Pulsar Data Processing Pipeline

“…During the FPGA preprocessing stage, the wideband signal is divided into multiple narrowband signals using PFB/ Oversampled Polyphase Filter Banks (OPFB; Zhang et al 2023b), which are then transmitted to various nodes of the GPU cluster for processing. UWLPIPE is capable of handling subband data from both PFB and OPFB channel division modes.…”

PSRDP: A Parallel Processing Method for Pulsar Baseband Data

“…It divides the 704-4032 MHz signal into three analog RF bands for sampling. In the FPGA preprocessing stage, it further divides the data into 26 continuous subbands, each with a bandwidth of 128 MHz, using PFB (polyphase filter bank) technology (Zhang et al 2023b). The FPGA packages the data into VDIF format 7 and transfers it to GPU nodes using the UDP protocol.…”

A sub-band division algorithm for ultra-wide bandwidth pulsar signals based on RFSoC

“…Zhang et al designed a signal division scheme for QTT ultra-wide bandwidth signals and verified the effectiveness of the channel division algorithm using ultra-wide bandwidth pulsar baseband simulation data (Zhang et al, 2023a). Zhang et al give the details and simulation of ultra-wide bandwidth sub-band division algorithm based on critical sampling polyphase filter banks and oversampling polyphase filter banks, respectively (Zhang et al, 2023b).…”