How do Tektronix waveform monitors measure jitter and why does it disagree with an oscilloscope?
The WFM700, WFM7000 and WVR7000 series instruments measure jitter using a phase demodulation method whereby the clock is extracted from the SDI deserializer and is compared against an internally generated stable clock signal. A peak detector is then used to measure the actual jitter value.
Most oscilloscopes use a method where the serial signal is sampled and measurements of jitter are made directly from that samples eye pattern. These two approaches can sometimes result in slightly different jitter measurements however the SMPTE standards for measuring jitter in SDI signals specify the use of the phase demodulation method described above and implemented in our waveform monitors.
We have an application note available for free download from our website that goes into much greater detail about jitter in serial digital video and some of the Tektronix tools for measuring it.
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