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.