Design Of Ultra Wide Band Digital Back-End System For Pulsar Observation

Pulsar observation is an important research field of radio astronomy.The research on pulsars is conducive to the development of astrochemistry,astrophysics and physics,time measurement and research.Pulsar digital back-end system is a terminal equipment for pulsar observation.Pulsar signals have the characteristics of weak amplitude,short period and dispersion effect when propagating in interstellar media.In order to accurately and effectively receive and process these signals,it is necessary to design a digital back-end system with multi input channels,high bandwidth,high time resolution,high frequency resolution and real-time data processing capability.Based on the independently designed RFSo C hardware platform,this paper presents a design of an ultra wideband and high time resolution pulsar observation digital back-end system.The system can simultaneously sample,process and transmit the input signals of 4 channels with 2GHz bandwidth.Each channel includes one input of left-handed polarization and one input of righthanded polarization signal.In order to achieve a high input bandwidth of 2GHz per channel,the ADC sampling frequency of each channel is up to 4GSps.When realizing the real-time processing of ADC high-speed sampling data stream on FPGA,the output data of each channel ADC is first converted into 16 parallel low-speed data streams,and then the combined FFT algorithm is used to channelize the data.In this paper,a Stokes parameter calculation module is designed to calculate the polarization parameters of the channelized data,and then the Bartlett periodogram method is used to estimate the power spectrum of the data and reduce the speed of the data.Finally,a 10 Gigabit Ethernet transmission module is designed to package and transmit the power spectrum data.In the case of the simultaneous output of I,Q,U,and V polarization data,the system can output4096 frequency channels at the same time,and the time resolution is better than 29μs.In order to facilitate the user to configure and monitor the work of the ultra-wideband digital back-end system,the PYNQ operating system based on the ARM processor system of the RFSo C hardware platform is built,and the hardware drivers and software graphical user interface in the PYNQ environment are developed.Users can connect to the PYNQ server through Ethernet to remotely control the RFSo C hardware platform.Since the control program runs completely in the PYNQ environment,there is no need to consider the development of client interactive software,and the compatibility of the software system is therefore stronger.A data storage software is also designed for the data storage host computer,which is used to capture and save the data transmitted by 10 Gigabit Ethernet.