A delay line calibration mechanism includes a delay line, a phase detector, and a controller. The delay line receives an input pulse, a calibration pulse, a first delay selection signal, and a second delay selection signal, delays the input pulse for a delay period according to the first delay selection signal to output a delayed pulse, and delays the calibration pulse for a calibration delay period according to the second delay selection signal to output a delayed calibration pulse. The controller is for generating the input pulse, the calibration pulse, and a reference pulse. The controller also generates the first delay selection signal, and generates the second delay selection signal according to a phase difference signal. The phase detector is for generating the phase difference signal indicating the difference between the delayed calibration pulse and the reference pulse by comparing the delayed calibration pulse and the reference pulse.