Design and implementation of high linearity FPGA-TDCs and an integrated large scale TCSPC system for time-resolved applications

  • Haochang Chen

Student thesis: Doctoral Thesis


The time-correlated single-photon counting (TCSPC) technology is a vital, advanced measurement and analytical tool for time-resolved biomedical, physics research and many industry areas because of its high temporal resolution and sensitivity. Analogue-based conventional TCSPC systems have been commercialised and applied in scientific experiments widely. However, the complicated system of conventional TCSPC equipment causes the bulky size, high cost, low conversion rate and limited channel number. With the recent rapid development of semiconductor technology, Field Programmable Gate Arrays (FPGA) become the promising platforms for high-performance digital TCSPC systems.;The time-to-digital converter (TDC) is the core component of a TCSPC system as it provides the temporal measurements with extremely high-resolution. For the scientific experiments, prototyping and high-end instruments, FPGA-based TDCs or TCSPC systems can provide excellent flexibility and compatibility with the much lower design and implementation costs. However, compared with ASIC and analogue implementations, the reported FPGA-TDCs have poor linearity performances with severe non-linearity problems such as missing-codes, ultra-wide bins and the bubbles problems. As a result, this study focuses on to improve the linearity performance by exploring the sources of non-linearity in the tapped delay line (TDL)-based FPGA-TDCs;This thesis proposes two novel FPGA-TDC designs to address the linearity drawbacks. The first TDC design proposes a combination architecture innovatively to restrain the differential non-linearity (DNL) to < ±1LSB (LSB = 10.5ps) with the complete removal of missing-codes. By developing and using a hardware-friendly bin-width calibration, the DNL has been reduced to < ±0.1LSB. Furthermore, getting benefits from the direct-histogram architecture, the proposed FPGA-TDC/TCSPC design has the capability of multi-event measurement and ultra-low dead-time (24K independent TCSPC channels with both photon counting and time-correlated imaging mode and a tunable temporal resolution. For verification, this study applied the system in a typical fluorescence lifetime measurement. According to the CMM calculated results base on the measured data, the proposed system demonstrated the accurate and reliable measurement performances.
Date of Award19 Apr 2020
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde & EPSRC (Engineering and Physical Sciences Research Council)
SupervisorDavid Li (Supervisor) & Gail McConnell (Supervisor)

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