Design Of Radio Astronomy Digital Backend For Pulsar Observation

The formation of a pulsar originates from the high-speed rotation of magnetized neutron stars formed by supernova in the late stage of life.The discovery of the pulsar is of great significance to the exploration of radio astronomy.The pulsar digital backend is a terminal device for observing and exploring pulsars,due to the existence of millisecond pulsars and pulsars with large dispersion values,it is necessary to design a high time resolution system and a high frequency resolution system.Accoding to the study of millisecond pulsars,more information about general relativity,interstellar magnetic fields,interstellar mediums,planetary physics and cosmology will be discovered.There are a large number of millisecond pulsars.The pulse radiation duty cycle is only 5-10%,the pulse width of some millisecond pulsars can even reach 0.1ms.In order to observe it,pulsar observation equipment with high time resolution was needed.The difficulty of high time resolution system design is how to complete high-speed data processing under the premise of wide bandwidth.A solution was presented,the collected high-speed data was divided into eight groups to reduce the data rate and process the data in parallel,achieve channelization processing.Besides,some pulsars have larger dispersion coefficient values,in order to observe these pulsars,frequency resolution of the observing system must be improved.The difficulty of high frequency resolution system design is how to complete high-speed data processing under the premise of wide bandwidth and how to accomplish 128 K points Fourier transform under limited system resources.In terms of the first difficulty,high frequency resolution system still divide the collected high-speed data into eight groups to reduce the data rate.In terms of the second difficulty,four innovation points were proposed.Firstly,uses N-point complex sequence to calculate two N-point real sequence's Fourier transform.Secondly,uses the Bit / Digit Reverse Order mode of the FFT IP core.Thirdly,uses the CORDIC algorithm to generate the twiddle factor.Lastly,uses a new algorithm instead of the old storage algorithm and finally completes high frequency resolution system design.Pulsar digital backend as a system needs human-computer interaction interface to realize the initialization of hardware device,parameter setting and store the data,so pulsar digital backend software system was needed.The pulsar digital backend software system completed by this article includes client program in upper computer,server program in ARM and data storage program in storage computer.The advantage of pulsar digital backend software system is that the server program is designed as a general communication control program.When the system version of the pulsar receiver changes,the server software program does not need to be changed,which reduces the workload.