A broadband digital receiving system with large dynamic range for solar radio observation

Solar radio spectra and their temporal evolution provide important clues to understand the energy release and electron acceleration process in the corona, and are commonly used to diagnose critical parameters such as the magnetic field strength. However, previous solar radio telescopes cannot provide high-quality data with complete frequency coverage. Aiming to develop a generalized solar radio observing system, in this study, we designed a digital receiving system that could capture solar radio bursts with a broad bandwidth and a large dynamic range. A dual-channel analog-to-digital converter (ADC) printed circuit board assembly (PCBA) with a sampling rate of 14-bit, 1.25 Giga samples per second (GSPS) cooperates with the field-programmable-gate-array (FPGA) chip XC7K410T in the design. This receiver could realize the real-time acquisition and preprocessing of high-speed data of up to 5 GB s(-1), which ensures high time and spectral resolutions in observations. This receiver has been used in the solar radio spectrometer working in the frequency range of 35 to 40 GHz in Chashan Solar Observatory (CSO) established by Shandong University, and will be further developed and used in the solar radio interferometers. The full-power bandwidth of the PCBA in this receiving system could reach up to 1.5 GHz, and the performance parameters (DC-1.5 GHz) are obtained as follows: spur free dynamic range (SFDR) of 64.7-78.4 dB, signal-to-noise and distortion (SINAD) of 49.1-57.2 dB, and effective number of bits (ENOB) of > 7.86 bit. Based on the receiver that we designed, real-time solar microwave dynamic spectra have been acquired and more solar microwave bursts with fine spectral structures are hopeful to be detected in the coming solar maximum.