Design Of Global Clock Distribution And TDC Module Based On FPGA

For many advanced electronic systems, their performance is highly related to time resolution of the system and the system's global clock signal. Achieving a high time resolution, plus a high accuracy and high stability global clock signal can help improve the performance of an electronic system.In this thesis, the image quality of All-digital PET system is greatly related to the time resolution. By sending sampling time of the time-to-digital converter to the backend buffer and processing unit to process, can get time information of the pulses which come from the photomultiplier tube. Based on the summarization of commonly used time interval measurement methods and combined with the internal structure of FPGA, a design of Time-to-Digital converter in FPGA is analyzed and verified. The design can achieve high resolution in time measurement by using carry chain of FPGA as delay unit and verified through simulation by connecting multiple dedicated carry lines together as a carry chain.In the meantime, as other electronic systems, the front-end electronics module of the all-digital PET requires a global clock signal distribution module that can act as a timing signal benchmark of multiple data processed in the TDC module. In order to satisfy the demand, a new kind of global clock signal distribution module is designed using FPGA and AD9516-4. Based on the demand of the global clock signal distribution module, a method is proposed. In this method, a high frequency signal is generated by the phase-locked loop through a reference signal, in the meantime, the divider in the chip is used to divide the high frequency signal, and LVDS mode is used to transmit multiple synchronous clock signals, so that multiple clock signals have the same frequency, phase and amplitude. Compared to clock distribution module implemented by other method, this is a high accuracy, low power consumption and high stability method. This module is already used in All-Digital PET system, and verified that this module has the characteristics of high accuracy and high stability.