Preliminary Specifications for the DSPU to be used in the PS Transverse Damping System

The Digital Signal Processing Unit (DSPU) [CERN-SL-2002-047-HRF, V. Rossi] has been successfully used for the SPS dampers since 2001. It is now foreseen for use in the new PS transverse dampers for both ions coming from LEIR and protons coming from the Booster. The core of this unit being based on programmable logic, it appeared that after some minor hardware and more software changes, the circuit would meet the PS needs. Initially it included a notch filter, a PPM (cycle-by-cycle) variable delay, programmable in clock period, and a fine delay (1 ns resolution and 24 ns range). The circuit was clocked at a revolution frequency multiple (1848) with about 0.2% frequency increase for protons and 1.6% for ions (not tested yet). The architecture to be used in the PS is a bit more complex; it also includes a notch at the revolution bands, but adds a Hilbert filter (for betatron phase shift) with dynamic phase control and an automatic (and dynamic) delay compensation circuit. The clock should now be a multiple of the revolution frequency (160) that spans from 175 kHz to 480 kHz (+274%).