Tektronix 2715, User Manual

Page: 217 / 360

Spectrum Analyzer Menus
2715 User Manual
6–35
A
B
Note folded-over
signal peaks at
100 MHz, 200 MHz,
and 300 MHz.
Figure 6–7: B, C Minus A Offset to Center
You have offset the difference between the B and A register waveforms, which is
always greater than zero, to the top of the screen (zero difference is at the
reference level). However, values above the reference level appear at the bottom
of the screen. See Figure 6–8. The points labeled A and B in Figures 6–7 and
6–8 have exactly the same value in each figure. Imagine that the screen curves
backwards at the top and bottom until it joins itself, forming a cylinder.
All points of zero difference lie along the joint. Now cut the joint and uncurl the
cylinder, allowing it to become a flat screen again. Both the top and bottom of
the screen represent zero difference, with negative signal peaks descending from
the top of the screen and positive peaks rising from the bottom.
A
Note the signal
peaks are no
longer folded.
B
Figure 6–8: B, C Minus A Offset to Top