Double-Split-Electrode Transversal Filter for Telecommunication Applications

A novel structure for on-chip tap weight implementation in CCD transversal filters is described. The new approach employs two splits in the CCD sensing electrodes to improve on the performance of the conventional single-split weighting technique. It is shown that the new approach greatly reduces the capacitance associated with the sensing nodes and consequently reduces the common-mode signal, gain sensitivity, coefficient error, and clock-noise pickup. Experimental results are presented which verify the improved performance of the double-split-electrode structure. The results achieved for a 3.4-kHz low-pass filter clocked at 32 kHz show a signal- signal-to-noise ratio of 86 dB with harmonic distortion of less than 0.3 percent.