Tektronix WFM5200 User Manual page 156

Application Example
140
To time the inputs to a router.
1. Perform steps 1 through 5 of the previous procedure.
2. Route the signal you want as the master to the appropriate input, SDI or
Composite, and terminate properly.
3. Route the reference signal to the reference input and terminate appropriately.
4. Save the timing offset for the master input (MEAS > Save Offset > SEL) and
select the Relative to: Saved Offset mode from the pop-up menu.
NOTE.
You cannot save the timing offset if either the input or reference is missing
or unlocked. You also cannot save a reference when in internal mode. Saving an
offset in these conditions would lead to misleading results so it is not allowed by
the instrument. A warning message will appear on the screen if you attempt to
save the offset when it is not allowed.
5. Now select other inputs to the router to be connected to the instrument. For
each input, the relative timing will be displayed.
6. Adjust the timing offset at the master sync source to time down the inputs to
the router to match the master.
Usage notes.
The resolution of the timing display for SD signals is one 27 MHz clock cycle
or 37 ns. For HD signals, it is one clock at 74.25 MHz, which equates to about
13.5 ns. To get the greater accuracy needed for a composite signal, first use
the timing display to get close, then use a vector display for the final burst
phase alignment. Since the instrument can display both the timing display
and a vector display simultaneously (each in its own tile), this process can
still be easy and quick.
For an SDI input relative to an analog reference, the situation is more
complex. For the timing display, three definitions of "zero offset" on an SDI
input are supported, Analog (DAC) and Serial (0H) and Saved Offset.
The Analog (DAC) setting uses the methodology illustrated in appendix B of
SMPTE RP168. This method shows the SDI signal being converted to analog.
The converted analog signal is then compared to the analog reference. For
this mode the nominal delay of the D to A converter is assumed to be 4.6
microseconds for SD, 1.3 μs for HD and 0.0 us for 3 Gb. The 0.0 μs delay
for 3 Gb means the Analog (DAC) and Serial (0H) modes are equivalent
for 3 Gb signals.
WFM5200 Waveform Monitor User Manual