Design, characterisation, and digital linearisation of an ADC analogue front-end for gamma spectroscopy measurements

This work presents the design, experimental characterisation, and digital post-distortion (i.e., digital linearisation) of a MHz-range ADC analogue front-end prototype for a gamma radiation spectrometry system under development at the National Center for Nuclear Research (NCBJ) in Poland. The design accounts for the electrical response of the gamma particle detector in providing signal conditioning and ADC protection against high-voltage spikes due to occasional high-energy cosmic radiation, as well as proper ADC clocking. As the front-end inevitably introduces nonlinear distortion and dynamic effects, a characterisation is performed to quantify the actual performance in terms of Total Harmonic Distortion (THD) and Effective Number of Bits (ENOB). Thus, a digital linearisation based on both static and memory polynomial models is successfully applied by means of post-distortion processing, guaranteeing a substantial improvement in THD and ENOB, and demonstrating the effectiveness of the hardware/software method for gamma radiation spectrometers.