An improved non-uniform fast Fourier transform method for radio imaging of coronal mass ejections

Radioheliographs can obtain solar images at high temporal and spatial resolution,with a high dynamic range.These are among the most important instruments for studying solar radio bursts,understanding solar eruption events,and conducting space weather forecasting.This study aims to explore the effective use of radioheliographs for solar observations,specifically for imaging coronal mass ejections(CME),to track their evolution and provide space weather warnings.We have developed an imaging simulation program based on the principle of aperture synthesis imaging,covering the entire data processing flow from antenna configuration to dirty map generation.For grid processing,we propose an improved non-uniform fast Fourier transform(NUFFT)method to provide superior image quality.Using simulated imaging of radio coronal mass ejections,we provide practical recommendations for the performance of radioheliographs.This study provides important support for the validation and calibration of radioheliograph data processing,and is expected to profoundly enhance our understanding of solar activities.

A 3 Giga Sample Per Second 14-bit Digital Receiver with 9 GHz Input Bandwidth for Solar Radio Observation

A new digital receiver with excellent performances has been designed and developed for solar radio observation,which can receive the radio signal from direct current(DC)to 9 GHz in the direct acquisition way.On the digital receiver,the analog-to-digital converter(ADC)with 14-bit,two input channels and 3 Giga Samples per second(Gsps)are used to acquire observed signal,and the field-programmable-gate-array chip XCKU115 acts as the processing module.The new digital receiver can be used to directly sample the solar radio signals of frequency under 9 GHz.When receiving the solar radio signal above 9 GHz,the new digital receiver can save 1–2 stages of frequency down-conversion,and effectively improve many indexes of the solar radio observation system,i.e.,the time resolution,analog front-end circuit,weight and volume of the analog circuit system.Compared with the digital receiver with sampling rate below 1 Gsps used in existing solar radio telescope,the new digital receiver reduces the frequency switching times of large bandwidth,which is beneficial to improving the frequency and time resolutions.The ADC sampling resolution of 14 bits,providing a large dynamic range,is very beneficial to observing smaller solar eruptions.This receiver,which would be used in the solar radio observation system,well meets the latest requirements with the resolutions of time(≤1 ms)and frequency(≤0.5 MHz)for fine observation of radio signals.