Bunch-by-bunch feedback systems for KEKB rings

The bunch-by-bunch feedback systems to cure coupled bunch instabilities in KEKB are now under development. The minimum bunch space of only 2 ns requires the band-width of the feedback systems wider than 255 MHz. The huge number of stored bunches which amounts to 5000 per ring demands the high speed and large memory digital signal processing for both signal delay and phase shift. The pickup electrodes and position detection systems are designed to satisfy the requirements of time response. The signal process part consists of high speed two tap FIR filters enables us the functions of DC rejection, phase shifts and simple delay. The waveguide overloaded cavities will be used as the longitudinal kickers. All the components are now under fabrication and will be installed until the commissioning of the rings. (author)