This article presents a prototype of beam position and phase measurement(BPPM)electronics designed for the LINAC in China Accelerator Driven Sub-critical system(ADS).The signals received from the Beam Position Monitor(BPM)detectors are narrow pulses with a repetition frequency of 162.5 MHz and a dynamic range more than40 dB.Based on the high-speed high-resolution Analog-to-Digital conversion technique,the input RF signals are directly converted to In-phase and Quadrature-phase(IQ)streams through under-sampling,which simplifies both the analog and digital processing circuits.All signal processing is integrated in one single FPGA,in which real-time beam position,phase and current can be obtained.A series of simulations and tests have been conducted to evaluate the performance.Initial test results indicate that this prototype achieves a phase resolution better than 0.1 degree and a position resolution better than 20μm over a 40 dB dynamic range with the bandwidth of 780 kHz,which is well beyond the application requirements.
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