Time-Mode analysis of Crosstalk interference in a FPGA-based TDC implementation

In modern electronic systems and telecommunication applications, crosstalk (XT) has become a serious problem, especially in very high-speed, multi-channel, and high-density circuits. Crosstalk interference is an unwanted electromagnetic energy sharing between a node (aggressor) and a signal carrying information (victim). If the interference is strong enough, the receiver reads a corrupted information. In Time-Mode (TM) circuits and in time-based experiments, where the information is represented as the time distance between signals, the induced electromagnetic energy is converted in a temporal shift of the edges of the waves degrading the information or the measurements respectively. In this sense, Time-to-Digital Converters (TDCs) are the building blocks of TM circuits and the principal actors in time-based experiments. In fact, a TDC has the role to convert into a digital code a time interval. Nowadays, market asks for higher and higher number of channels maintaining the performance of the systems. A limiting factor to achieve this result is exactly the XT, and therefore it is necessary to study the sources of interference to minimize electromagnetic sharing. In this contribution, we classify and investigate the effects and the causes of crosstalk in time measurements considering a multi-channel TDC implemented in Field Programmable Gate Array (FPGA) as case study, deriving design rules for minimizing the related effects.