A new digital auto-tracking pole-zero compensation technique for high-resolution spectroscopy

Abstract

In order to obtain high-energy resolution in both analogue and digital spectroscopy systems, it is mandatory to guarantee the stability of the baseline signal reference. The precision of the compensation of the long exponential decay due to the charge preamplifier, especially in case of high rate of events, has a direct influence on the baseline reference value. We have developed a new technique, which automatically performs such a compensation on-line in a digital way. It allows obtaining spectroscopic performance and keeps at minimum both the A/D converter sampling frequency (thus power consumption) and its resolution (thus cost). This is done through a fixed-point processing architecture, which is implemented within a FPGA device. During operation, the compensator automatically tracks variations of the value of the preamplifier time constant also at high event rate.