Jitter measurement apparatus, jitter measurement method, recording media, communication system and test apparatus
Provided is a jitter measurement apparatus, including a sampling section that samples a signal under measurement having a cycle T, a waveform reconfiguring section that shapes a reconfigured waveform having the cycle T by rearranging ordinal ranks of sample values sampled by the sampling section, a distribution generating section that generates a timing distribution of edges in the reconfigured waveform, and a statistical value calculating section that calculates a statistical value of the timing distribution. The sampling section may sample the signal under measurement having the cycle T a certain number of times N while the signal under measurement repeats for M cycles, where M and N are coprime.
1. A jitter measurement apparatus, comprising:
a sampling section that samples a signal under measurement having a cycle T;
a waveform reconfiguring section that shapes a reconfigured waveform having the cycle T by rearranging ordinal ranks of sample values sampled by the sampling section;
a distribution generating section that generates a timing distribution of edges in the reconfigured waveform; and
a statistical value calculating section that calculates a statistical value of the timing distribution.
2. The jitter measurement apparatus according to claim 1 , wherein the sampling section samples the signal under measurement having the cycle T a certain number of times N while the signal under measurement repeats for M cycles, where M and N are coprime.
3. The jitter measurement apparatus according to claim 2 , wherein the waveform reconfiguring section rearranges initial ordinal ranks k of the sample values sampled by the sampling section to have reconfigured ordinal ranks i by inputting the initial ordinal ranks k into an expression i=k·M mod N, where k is expressed by integers from 0 to N−1, and uses these rearranged sample values to shape the reconfigured waveform having the cycle T.
4. The jitter measurement apparatus according to claim 1 , wherein the statistical value calculating section calculates an expected value of the timing distribution as the statistical value.
5. The jitter measurement apparatus according to claim 1 , wherein the statistical value calculating section calculates a distribution width of the timing distribution as the statistical value.
6. The jitter measurement apparatus according to claim 1 , wherein the distribution generating section includes:
a unit-interval waveform generating section that generates a plurality of unit-interval waveforms by dividing the reconfigured waveform into a plurality of unit intervals;
an aggregate value calculating section that calculates an aggregate value at each phase in each of the plurality of unit-interval waveforms by adding together the sample values at the same phase of each unit-interval waveform; and
a difference calculating section that calculates a difference between each pair of aggregate values at adjacent phases, and
the distribution generating section generates the timing distribution based on the differences calculated by the difference calculating section.
7. The jitter measurement apparatus according to claim 6 , wherein
the distribution generating section further includes a waveform inverting section that inverts the unit-interval waveforms generated by the unit-interval waveform generating section, and
the aggregate value calculating section adds the sample values of the unit-interval waveforms having rising edges to the inverted sample values of the unit-interval waveforms having falling edges that are inverted by the waveform inverting section, or
adds the sample values of the unit-interval waveforms having falling edges to the inverted sample values of the unit-interval waveforms having rising edges that are inverted by the waveform inverting section.
8. The jitter measurement apparatus according to claim 7 , further comprising a prescribed bit unit-interval waveform group selecting section that selects the unit-interval waveforms generated by the unit-interval waveform generating section at prescribed bit intervals in the signal under measurement, wherein
the aggregate value calculating section adds the sample values of the unit-interval waveforms having rising edges to the inverted sample values of the unit-interval waveforms having falling edges that are inverted by the waveform inverting section in the group of unit-interval waveforms selected by the prescribed bit unit-interval waveform group selecting section.
9. The jitter measurement apparatus according to claim 6 , wherein the aggregate value calculating section adds together the sample values of the unit-interval waveforms having rising edges or the sample values of the unit-interval waveforms having falling edges.
10. The jitter measurement apparatus according to claim 6 , further comprising an identical data sequence unit-interval waveform group selecting section that selects, from among the unit-interval waveforms generated by the unit-interval waveform generating section, a group of unit-interval waveforms having identical data sequences in the signal under measurement immediately prior thereto, wherein
the aggregate value calculating section adds together the sample values of each unit-interval waveform in the group selected by the identical data sequence unit-interval waveform group selecting section.
11. The jitter measurement apparatus according to claim 6 , further comprising a prescribed bit unit-interval waveform group selecting section that selects the unit-interval waveforms generated by the unit-interval waveform generating section at prescribed bit intervals in the signal under measurement, wherein
the aggregate value calculating section adds together the sample values of each unit-interval waveform in the group selected by the prescribed bit unit-interval waveform group selecting section.
12. The jitter measurement apparatus according to claim 1 , further comprising:
an ideal edge timing calculating section that calculates an ideal edge timing of the signal under measurement; and
an error sequence statistical value calculating section that calculates a statistical value of an error sequence obtained by arranging, in a time-series, differences between expected values of the timing distribution calculated by the statistical value calculating section and the ideal edge timing calculated by the ideal edge timing calculating section.
13. The jitter measurement apparatus according to claim 1 , further comprising:
an ideal edge timing calculating section that calculates an ideal edge timing of the signal under measurement; and
an error sequence statistical value calculating section that calculates a frequency component of an error sequence obtained by arranging, in a time-series, differences between expected values of the timing distribution calculated by the statistical value calculating section and the ideal edge timing calculated by the ideal edge timing calculating section.
14. A communication system provided with a transmitter and a receiver, wherein the receiver includes the jitter measurement apparatus of claim 1 .
15. The communication system according to claim 14 , wherein
the receiver further includes a jitter value notification section that notifies the transmitter concerning the statistical value calculated by the statistical value calculating section, which is a jitter value of the transmission signal, and
the transmitter includes a frequency characteristic adjusting section that adjusts a frequency characteristic of the transmission signal to decrease jitter value of the transmission signal in the receiver according to the jitter value as notified by the jitter value notification section.
16. A jitter measurement method, comprising the steps of:
sampling, by a sampling section of a jitter measurement apparatus, a signal under measurement having a cycle T;
shaping, by a waveform reconfiguring section of the jitter measurement apparatus, a reconfigured waveform having the cycle T by rearranging ordinal ranks of sample values obtained at the sampling step;
generating, by a distribution generation section of the jitter measurement apparatus, a timing distribution of edges in the reconfigured waveform; and
calculating, by a statistical value calculating section of the jitter measurement apparatus, a statistical value of the timing distribution.
17. The jitter measurement method according to claim 16 , wherein the sampling step includes sampling the signal under measurement having the cycle T a certain number of times N while the signal under measurement repeats for M cycles, where M and N are coprime.
18. The jitter measurement method according to claim 17 , wherein the reconfiguring step includes rearranging initial ordinal ranks k of the sample values obtained at the sampling step to have reconfigured ordinal ranks i by inputting the initial ordinal ranks k into an expression i=k·M mod N, where k is expressed by integers from 0 to N−1, and using these rearranged sample values to shape the reconfigured waveform having the cycle T.
19. A non-transitory recording medium storing thereon a program that, when used by a jitter measurement apparatus, causes the jitter measurement apparatus to function as:
a sampling section that samples a signal under measurement having a cycle T a certain number of times N while the signal under measurement repeats for M cycles, where M and N are coprime;
a waveform reconfiguring section that rearranges initial ordinal ranks k of the sample values sampled by the sampling section to have reconfigured ordinal ranks i by inputting the initial ordinal ranks k into an expression i=k·M mod N, where k is expressed by integers from 0 to N−1, and uses these rearranged sample values to shape a reconfigured waveform having the cycle T;
a distribution generating section that generates a timing distribution of edges in the reconfigured waveform; and
a statistical value calculating section that calculates a statistical value of the timing distribution.
20. A test apparatus that provides a test signal to a device under test to test the device under test, comprising:
a signal generating section that generates the test signal; and
a signal measuring section that measures an output signal of the device under test, wherein the signal measuring section includes:
a sampling section that samples the output signal having a cycle T a certain number of times N while the output signal repeats for M cycles, where M and N are coprime;
a waveform reconfiguring section that rearranges initial ordinal ranks k of the sample values sampled by the sampling section to have reconfigured ordinal ranks i by inputting the initial ordinal ranks k into an expression i=k·M mod N, where k is expressed by integers from 0 to N−1, and uses these rearranged sample values to shape the reconfigured waveform having the cycle T;
a distribution generating section that generates a timing distribution of edges in the reconfigured waveform; and
a statistical value calculating section that calculates a statistical value of the timing distribution.
21. The test apparatus according to claim 20 , wherein
the signal measuring section further includes a jitter value notification section that notifies the signal generating section concerning the statistical value calculated by the statistical value calculating section, which is a jitter value of the output signal, and
the signal generating section includes a frequency characteristic adjusting section that adjusts a frequency characteristic of the test signal to decrease jitter value of the output signal according to the jitter value as notified by the jitter value notification section.