WFM 1125 Option 0A/0B/0C/0D User Manual
3-1
Reference
This section presents detailed information on menus and functions of the
waveform monitor. The topics are organized alphabetically. Most topics are
named after the front panel labels and button names.
Bowtie Display
The Bowtie display evaluates the relative amplitude and timing among the three
video channels. This display requires a special test signal from the monitored
source. See Figure 3–1. The Tektronix TSG 1001 Programmable TV Generator
and PSC1125 Digital Television Parallel-to-Serial Converter can produce a
bowtie signal with 1 ns time marks, which aid in signal evaluation. The signal is
a 5 MHz sinewave on CH 1 (luminance) and 5.002 MHz (5.003126 MHz for
SMPTE 296M) sine waves on CH 2 (Pb) and CH 3 (Pr).
The display is made up of two separate waveforms as shown in Figure 3–1. The
left waveform always compares CH 1 to CH 2. The right waveform always
compares CH 1 to CH 3. Also, by the common reference of CH1, the CH2 to
CH3 timing is implicitly given.
Figure 3-1: Typical Bowtie display on the WFMĂ1125
The timing measurement is based on alignment of the center marker and the null
point at the center of the waveform. The generator provides a center marker,
which is centered on the null point when interchannel timing is correct. A shift of
the null to the left or right indicates a difference in the relative timing. If the null
shifts two full time markers, the relative timing error between channels would be
2 ns. If the null is to the left of the center marker, the color difference channel is
advanced relative to the luminance channel. When either of the nulls is shifted to
the right, that color difference signal is delayed relative to the luminance channel.
In Figure 3–2, the chrominance channel, CH 3 (Pr), is advanced relative to the
luminance channel by 1 ns.
Timing Measurement
To Next Page
Loading...
Need help?
General
