  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{\deg},
45{\deg}, 90{\deg}, and 135{\deg}. 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.
