Removal of crossbar-switch interference from multi-rate beam position signals with wavelet packet transform

Abstract Electron beam position measurement of storage rings is a typical multi-channel signal acquisition system that suffers from crossbar-switch (CS) interference consisting of massive harmonics and artifacts when CS-based channel disequilibrium compensation is used. However, it is not an effective method for removing the interference from the turn-by-turn (TBT) beam position signal in CS working. In this paper, a method that combines wavelet packet transform and coefficient baseline shift techniques is proposed to remove the CS interference without distorting the actual TBT signal. This method starts with wavelet packet decomposition of the contaminated TBT signal, then wavelet coefficients are further processed by the baseline shift and finally the processed coefficients of whole subbands are reconstructed through filter banks to obtain a clean TBT signal. As a result, a clean and undistorted fast acquisition signal is obtained at a relatively slow rate through partial reconstruction without using a decimation filter and a notch filter. Results with synthetic and real TBT signals demonstrate the effectiveness of the proposed method. Moreover, the relative root mean square error and normalized correlation coefficient criteria are measured, which also show that the proposed method does not distort the actual TBT signal while removing the CS interference.