A Real-time, Pipelined Incoherent Dedispersion Method and Implementation in FPGA

Abstract

In pulsar observation, dispersion occurs due to the interstellar medium. The dispersion significantly affects the detection of pulsar signals. To overcome the dispersion effect, incoherent dedispersion methods are often applied. The tranditional inchoherent dedispersion methods are computationally expensive and troublesome. To deal with this problem, in this paper, we developed a Real-Time, Pipelined Incoherent Dedispersion Method (RT-PIDM). RT-PIMD only caches the summed-up time series, instead of all the frequency spectra, so the memory consumption is determined by the number of DM trails, whereas the traditional method’s memory consumption is determined by the number of frequency channels. In most of the situations, the number of frequency channels is several times more than that of DM trails, which means the memory consumption of traditional methods is more than that of RT-PIDM. With RT-PIDM, we designed a 1.2 GHz bandwidth prototype digital backend, and we finished pulsar observation with the 40 m radio telescope at Yunnan Observatory. The results demonstrate that the RT-PIDM can be implemented inside a single FPGA chip with less Block RAM, and the proposed RT-PIDM dedisperses the pulsar signal in real time and achieves the same result as compared to traditional incoherent dedispersion.

A Digital Backend with Pulse Detection for Radar Astronomy

“…Ahammed et al (2020) proposed a Block Adaptive Quantization method implemented in field-programmable gate array (FPGA) to reduce data rates of small satellite synthetic aperture radar data. In the realm of pulsar digital backends, the technique of spectral accumulation is frequently employed to achieve a significant reduction in data volume (Chennamangalam et al 2017;Liu et al 2022). Additionally, methods such as undersampling and digital down-conversion are employed to decrease data volume, particularly in cases of large bandwidth and high frequencies (Dong et al 2013;Zhu et al 2018).…”

Research on a Coherent Dedispersion Algorithm for Pulsar Baseband Data

“…The phenomenon is called dispersion. At present, there are two kinds of dedispersion techniques used in pulsar data processing: incoherent dedispersion (Liu et al 2022) and coherent dedispersion (Luo et al 2017). Incoherent dedispersion algorithm realizes channel division through filter banks, and then calculates the delay in each sub-channel separately.…”