Basic Measurements
1760 SeriesComponent Waveform/Vector Monitor User Manu al
4-22
The Bowtie test signal consists of a 500 kHz sine wave on
Channel 1 and 502 kHz sine waves of the same amplitude on
Channels 2 and 3. The Channel 2 and 3 waveforms are gen-
erated to be exactly in phase with the Cha nnel 1 signal in the
center of the line. The 1760--Series subtracts Channel 2 from
Channel 1 to make the left half of the di splay,and Channel 3
from Channel 1 for the right half. The 2kHz frequency offset
between luminanceand the difference channels causes the
relative phase to change constantly. The subtraction process
is complete (resultingin zero) only when the two compo-
nents are exactly in phase.
Changesof relative timing change the point at which the null
occurs by changing relative phase between the t woc hannels.
If the amplitudes are not equal, the subtraction never yields
zero and the null is broadened.
The Lightning and Diamond displays provide a high resolu-
tion indicator ofproper timing when used with the Bowtie
signal. Aspiral ellipse is displayed and the width of the el-
lipse reaches its minimum as timing is adjustedto the opti-
mum setting. Itis not necessary to adjust the relative
amplitudes tosee the minimum ellipse.