“Modeling Noise Effects in Time-to-digital Converters

In this work, the main sources of error affecting time interval measurements are analyzed and modeled. Time interpolation techniques utilizing both synchronous and asynchronous strategies to perform time measurements have been considered. Jitter on start and stop timing signals, interpolator nonlinearities, quantization error and jitter affecting the system clock driving the counter have been recognized as the main contributors to measurement uncertainty and their effects are analytically described. A deeper investigation on the cumulative effect of the clock jitter is discussed in order to determine mean values, variances and probability density functions of quantizer output and quantization error sequences. Simulations showing mean values and variances of the quantizer output are also presented, in order to validate theoretical results. The obtained model is useful both for design and testing purposes.