A high precision TDC based on a multi-phase clock
The design of a high-precision time-to-digital converter (TDC) based on a multiphase clock implemented using a single field-programmable gate array is discussed in this paper. The TDC can increase the resolution of the measurement by using time interpolation. A phase-locked loop is used to generate four multiphase clocks whose frequencies are the same and whose phases are 0°, 45°, 90°, and 135°. In addition, the duty ratios of the four clocks are 50%. By utilizing four multiphase clocks to make up the interpolation clock, one clock period can be divided into eight uniform parts. The resolution of the TDC can be improved to 1/8 of a clock period. Furthermore, we have also designed a discriminator circuit for identifying the start and stop signals. On the basis of this circuit, the TDC can still measure the time interval of two signals when the start and stop signals are uncertain. The experimental results indicate that the time resolution of the TDC can achieve the theoretical value, and the linearity is very good. The architecture consumes fewer logic cells and is more stable.