Development of digital BPM front-end conditioning circuit for BEPCII linac

Aiming to control the rising failure rate of electronics system for BEPC II linac’s beam position measurement, considering the physical design parameters of BEPC II and the requirements of band-pass sampling of BPM electronics ADC chip, a digital BPM RF front-end electronics with high isolation degree and good amplitude and phase consistency is designed. The digital BPM electronics system adopts MicroTCA 4.0 system architecture, takes FPGA as the main controller, and is designed based on EDA software. This paper mainly introduces RF power amplifier, digital adjustable attenuator and bandpass filter in RF front-end electronics module, as well as the laboratory and online test results. In the collision mode of BEPC II, positron beam was used to complete the electronic system online test, and the measurement accuracy of x-direction was about 38.46 μm, while that of y-direction was about 26.16 μm. The measurement accuracy and system stability of the proposed method are better than that of commercial analog BPM electronics module, and can meet the beam position measurement requirements of BEPC II linac.