A Time-to-Digital Converter-Based Correction Method for Charge Measurement Through Area Integration

A high-precision charge measurement can be achieved by the area integration of a digitized quasi-Gaussian signal after the signal passes through the shaper and analog-to-digital converter. The charge measurement contains an error due to the uncertainty of the first sampled point of a signal waveform. To reduce the error, we employ a time-to-digital converter to measure the uncertainty precisely, and we design correction algorithms to improve the resolution of the charge measurement. This paper includes analysis and simulations of the proposed algorithms and implementation of them in a field-programmable gate array device. In addition, the tests are also conducted to evaluate the performance of the correction method. Test results indicate that the resolution of the charge measurement is successfully improved from 2.31 to 1.26 by using a signal from the shaping circuit (with the amplitude of 2 V, and leading and trailing edges of about 80 and 280 ns, respectively) digitized at the sampling rate of 62.5 Msps.