A delay locked loop for instantaneous time-of-flight sensing based on a CMOS demodulation detector

A Delay-Locked Loop (DLL) is presented that can track the phase of a continuous-wave modulated light signal. Using it in a time-of-flight set-up allows tracking of an object´s distance in a fast and reliable way. The CMOS detector is built around a current-assisted photonic demodulator (CAPD) with an additional common-mode feedback (CMFB) avoiding detector saturation. The DLL control loop is implemented in an external FPGA, enabling flexibility and tuning of the control parameters. The system is a good candidate for industrial time-of-flight applications, where reaction time is important and outliers are unwanted. This novel DLL implementation has a phase noise below 1° and a settling time of 1 ms at a modulation frequency of 20 MHz.