Design and measurement of signal processing system for cavity beam position monitor

In this paper, in order to achieve the output signal processing of cavity beam position monitor （CBPM）, we develop a digital intermediate frequency receiver architecture based signal processing system, which consists of radio frequency （RF） front end and high speed data acquisition board. The beam position resolution in the CBPM signal processing system is superior to 1 ktm. Two signal processing algorithms, fast Fourier transform （FFT） and digital down converter （DDC）, are evaluated offiine using MATLAB platform, and both can be used to achieve, the CW input signal, position resolutions of 0.31 μm and 0.10 μm at -16 dBm. The DDC algorithm for its good compatibility is downloaded into the FPGA to realize online measurement, reaching the position resolution of 0.49 lain due to truncation error. The whole system works well and the performance meets design target.