Design of a New Solar Radio Observing System Working in 3–6 GHz

Abstract Solar radio bursts from decimeter to centimeter wavelength originate from radiations from coherent to incoherent mechanism. This spectral domain hosts a rich variety of fine structures that encode critical information about energetic electron beams, coronal magnetic fields, and ambient plasma conditions—key elements for understanding particle acceleration and energy release during solar flares. To exploit this diagnostic potential, a broadband observing system with high time and frequency resolution is essential. In this study, we designed and developed the Chashan Broadband Solar Decimetric Spectrometer (CBSdm), which enables high-precision observation of solar radio bursts in the 3–6 GHz frequency band. The system employs a 6 m parabolic antenna with a log-periodic dipole array feed, and utilizes nanosecond-level microwave switching technology to construct a dual-channel analog receiving chain (3.1–4.4 GHz/4.6–5.9 GHz). Real-time spectral processing is achieved via a 14-bit 3 GSPS analog-to-digital converter and an Field Programmable Gate Array-based digital backend. Key performance metrics include a noise figure of 2 dB, sensitivity of −77.9 dBm@2.6 GHz, and system linearity better than 0.998. Relative calibration was performed and cross-validated with data from the Learmonth Observatory. Since its deployment in 2023 October, the system has successfully captured X-class flare events, with dynamic spectra exhibiting typical continuum features and multi-frequency synchronous evolution. The coordinated observations of CBSdm (3–6 GHz) and CBScm (6–15 GHz) provide continuous gyrosynchrotron spectra covering the optically thick to thin transition, enabling diagnostics of flare magnetic fields and nonthermal electron distributions.