| 摘要 |
A delay time measurement apparatus of delay circuit is configured to minimize the influence of periodic noises for accurately measuring the delay time. The delay time measurement apparatus includes: a voltage controlled oscillator (VCO) whose oscillation frequency is controlled by a given voltage; a phase comparator having two inputs for comparing a phases difference between signals at the two inputs where one of the inputs receives an output of the VCO through a delay circuit whose delay time is to be measured and the other input directly receives the output of the voltage controlled oscillator; a phase lock loop having the VCO and the phase comparator therein to return an output voltage of the phase comparator to the VCO to control an oscillation frequency such that the phase difference between the two inputs of the phase comparator becomes zero; a signal adder for introducing an external signal into the phase lock loop for fluctuating the oscillation frequency, where the external signal is a signal whose average voltage level for an integer multiple of one cycle is zero; and a counter for counting the oscillation frequency of the VCO. |
