Tektronix AWVG1, User Manual

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Appendix C: Zone Plates
AWVG1 Wideband Video Generator User Manual
C- 3
Signals window). In this example, circle frequency is the pattern control
parameter, and the dependent parameters are: K
X
, K
X2
, K
XY
, K
Y
, and K
Y2
.
Figure C- 2: Zone plate Parameters window
TG 2000 display: KX (H freq)
Units: c/aph (cycles per average picture height)
K
X
denotes the initial constant horizontal frequency of the pattern. To see the
effects of changing this coefficient, set a waveform monitor to view the video
lines. The units are cycles per active picture height. The number of cycles in a
line depends on the width-to-height aspect ratio of the active video standard. For
example, K
X
= 9.0 results in approximately 12 cycles per line in a standard with
a 4:3 aspect ratio; the same setting yields about 16 cycles per line when the ratio
is 16:9.
To estimate the equivalent absolute frequency of the sine wave (to convert from
c/aph to c/s, or Hz), use the formula
f
eq
≅
K
X
×
R
l : av
×
R
aspect
×
N
lines
×
f
frame
where
R
aspect
is the aspect ratio (width
÷
height),
N
lines
is the number of lines per frame,
f
frame
is the frame rate, and
R
l : av
is the ratio of line length to the length of the active video.
The maximum frequency is (
±
) half of the active video standard’s sampling
frequency. In standards that use a 72.0 MHz clock, for example, the maximum
value of K
X
will correspond to a sine frequency of 36.0 MHz.
The Horizontal Sine zone plate signal is a K
X
-only zone plate (see Figure C--3).
K
X
Parameter