An FPGA-Based Phase Measurement System

Phase measurement is required in electronic applications where a synchronous relationship between the signals needs to be preserved. Traditional electronic systems used for time measurement are designed using a classical mixed-signal approach. With the advent of reconfigurable hardware such as field-programmable gate arrays (FPGAs), it is more advantageous for designers to opt for all-digital architecture. Most highspeed serial transceivers of the FPGA circuitry do not ensure the same chip latency after each power cycle, reset cycle, or firmware upgrade. These cause uncertainty of phase relationship between the recovered signals. To address the need to register minute phase shift changes inside an FPGA, we propose a design for phase measurement logic core having resolution and precision in the range of a few picoseconds. The working principle is based on subsample accumulation using systematic sampling over the phase detector signal. The phase measurement logic can operate over a wide range of digital clock frequencies, ranging from a few kilohertz to the maximum frequency that is supported within the FPGA fabric. A mathematical model is developed to illustrate the operating principle of the design. The VLSI architecture is designed for the logic core. We also discussed the procedure of the phase measurement system, the calibration sequence involved, followed by the performance of the design in terms of accuracy, precision, and resolution.