Tektronix AWVG1, User Manual, Page: 97 / 116

Appendix C: Zone Plates
AWVG1 Wideband Video Generator User Manual
C- 9
Standard Zone Plate Signals
The following standard zoneplate signals are generated by the AWVG1
Generator module:
The circle frequency is actually the equivalent of the maximum vertical sinusoid
frequency at the very top and bottom of the screen (see the discussion of the K
Y2
parameter earlier in this section). Adjusting the circle frequency has the simple
effect of increasing or decreasing the maximum frequency at the outer edges of
the pattern. However, this adjustment actually changes the coefficients of five of
the ten zone plate parameters in order to keep the pattern round and centered on
the screen.
The diagonal frequency is
2
Ꭹ
times the vertical and horizontal frequencies
(c/aph). Adjusting the diagonal sine frequency changes both the K
X
and K
Y
coefficients.
The horizontal frequency reported on the display is the real time frequency of the
sine wave that causes the vertical bar pattern. The maximum frequency is half of
the clock frequency used by the generator for the active video standard (for
example, 72.0 MHz/2 = 36.0 MHz).
For horizontal sweep frequencies up to half of the video standard’s sampling
frequency,
f
s
, the displayed value is the maximum (or swept to) frequency of the
sine wave. For numbers greater than f
s
/2, dividing the displayed value by the
sampling frequency will give the number of complete DC--( f
s
/2)--DC cycles per
line. For example, in a standard with sampling frequency of 72.0 MHz, a
horizontal sweep frequency of 144 MHz will result in approximately two
complete frequency sweeps across the picture.
The vertical frequency is actually the K
Y
coefficient. The maximum frequency
(c/aph) corresponds to the number of active video lines in a field of the active
video standard. For example, when a 525/59.94/1:1 standard, which has 484
active lines per field, is output, K
Y
can be any value between --484 and 484.
The vertical sweep frequency is actually the K
Y2
coefficient. For numbers greater
than maximum, dividing the displayed value by that maximum will give twice
the number of complete DC-max-DC sweeps per field (sweeps = (K
Y2
/K
Y
)/2).
For example, in a standard with 484 lines per field, a vertical sweep frequency of
968 c/aph
2
would result in one complete frequency sweep down the picture.
Circle (Bullseye)
Diagonal Sine
Horizontal Sine
Horizontal Sweep
Vertical Sine
Vertical Sweep