High speed digital signal processing electronics for the TLS longitudinal feedback system

A high-speed digital signal processing system is being built for feedback control of the bunch phase in the TLS storage ring. It consists of (1) an analog-to-digital converter plus demultiplexer (ADC/DEMUX) unit (2) a digital filters (DIFI) array and (3) a digital-to-analog converter plus multiplexer (DAC/MUX) unit. The ADC/DEMUX unit has a fast ADC that digitizes the discrete signal of bunch phases. The data are then down-sampled and distributed to the slower DSP chips in the DIFI array via communication ports. The DIFI array performs digital filtering such that phase error of each bunch is extracted. In the DAC/MUX, processed data from DIFI array are collected and organized in a proper sequence (there is a buffer that hold the output data for number of turns if higher loop gain is required). This stream of data is then converted back to analog signal for bunch phase correction. Design and construction issues of this system are reported.