Development of a Digital Signal Processing System for the X-ray Microcalorimeter onboard ASTRO-H

摘要

A digital signal processing system for the X-ray microcalorimeter array (SXS) is being developed for the next Japanese X-ray astronomy satellite, ASTRO-H. The SXS digital signal processing system evaluates each pulse by an optimal filtering process. For the ASTRO-H project, we decided to employ digital electronics hardware, which includes a digital I/O board based upon FPGAs, and a separate CPU board. It is crucially important for the FPGA to be able to detect the presence of an "secondary" pulses on the tail of an initial pulse. In order to detect the contaminating pulses, we have developed a new finite impulse response filter, to compensate for the undershoot in the derivative. By employing the filter it is possible for FPGA to detect the secondary pulse very close the first pulse, and to reduce the load of the CPU in the secondary pulse searching process.