Patent ID: 7783452

Claim:
A signal measuring apparatus that measures a first input signal and a second input signal, comprising: a first measuring section that measures the first input signal at a plurality of strobe timings arranged in each cycle of a measurement cycle; a second measuring section that measures the second input signal at a plurality of strobe timings arranged in each cycle of a measurement cycle; a phase difference calculating section that calculates phase differences between the first input signal and the second input signal in each measurement cycle based on measurement results from the first measuring section and the second measuring section; and a distribution generating section that generates distribution information of the phase differences calculated in each measurement cycle by the phase difference calculating section; wherein the distribution generating section generates a histogram that indicates a frequency of occurrence of each value concerning the phase differences calculated by the phase difference calculating section, the distribution generating section includes a plurality of counters that are disposed to correspond to each value of the phase differences and count a number of occurrences of the value of the corresponding phase difference, the first measuring section outputs a measurement result that indicates at what number strobe timing a change in the value of the first input signal is detected in each cycle, the second measuring section outputs measurement result that indicates at what number strobe timing a change in the value of the second input signal is detected in each cycle, and the phase difference calculating section outputs as the phase difference the difference between strobe timing numbers in the measurement results output by the first measuring section and the second measuring section.