Automatic Pole-Zero/Zero-Pole digital compensator for high-resolution spectroscopy: Design and experiments

In a high-resolution spectroscopy system the relatively long exponential de cay due to the charge preamplifier is customarily canceled in an analogue f ashion by means of a PZ (Pole-Zero) stage. The accurateness of such compens ation has a big impact on the energy resolution because it strongly affects the baseline-stability problems. We have automatically and on-line perform ed such a compensation in a digital way, while maintaining a spectroscopy p erformance and keeping at minimum both the ADC sampling frequency (thus pow er consumption) and its resolution (thus cost). This is done through an IIR filter, implemented within a FPGA by a DSP. The so-compensated waveform ha s, in excellent approximation, an all-pole shape. Starting from such a sign al, the minimum-noise filters for energy and/or time measurements are then promptly synthesized and implemented for real time operation through the sa me DSP.