Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
; Chinese Acad Sci, Shanghai Inst Appl Phys, Shanghai 201800, Peoples R China
Phase detection performs a crucial role in the phase control loop of RF signals in accelerators. This paper presents two methods that apply I/Q technique to phase detection of RF signals. The content includes the study of arithmetic and the setup of systems. The methods are as follows: 1. adopting I/Q demodulator, AD card and the technique of digital processing to detect the phase; 2. direct digital I/Q method. In the former, feasible calibration arithmetic against the inherent error of I/Q demodulators is suggested. In the latter, I and Q signals are generated by modulating the LO signal with a step of (2 pi/N). The phase detection error is below 0.5 degrees by using either of them.