A Design of Improved Circuits of the Auxiliary Electronic System of a Hydrogen Maser

The auxiliary electronic system of the first hydrogen maser in China has been working for many years. Nevertheless, the design of this system is outdated and the system has certain defects such as complicated peripheral circuits, many fault points, and occurrences of malfunctions not easily discernable. In this paper, we present a design of improved circuits of the auxiliary electronic system using the ARM+FPGA scheme. The design adopts 12-bit high-precision analog-to-digital conversion chips for wideband sampling, and incorporates a digital mode to improve the intelligent temperature control of the system. In the design we also use the DDS technology to generate signals for the frequency synthesizer. The design is simplified enough to realize communication of the system with the hydrogen maser. We have carried out tests of the design. The tests show that the design improves precisions of signal sampling, effective intelligent temperature adjustment has been realized with the digital temperature-control mode, circuit simplification has been achieved through the DDS technology, and the stability of the interface has been enhanced by the isolated RS-232 transceiver based on the iCoupler magnetic isolation technology. Overall, our design dramatically improves the capability and reliability of the system yet in the mean time simplifies the system.