HD3G7 HD 3 Gb/s SDI Video Generator module
How to use zone
plate signals on the HD3G7 module
Here is an example of how you can use zone plate signals to simplify a common
task.
One common task is measuring the horizontal frequency response of a system.
With a typical swept-frequency generator you would apply a signal such as a
1MHzto30MH
zsweepwithmarkersevery5MHz.Thenyoutrytoestimatethe
frequency of the 3 dB roll-off point by interpolating the position of the 3 dB point
between the markers.
The HD3G7 generator module's adjustable zone plate signal provides a better way:
The H Swee
p Zoneplate pattern control parameter is the H Sweep Frequency,
which controls the upper frequency limit of the sweep (the swept-to
frequency).
Simply adjust the H Sweep Frequency until the system roll-off is at –3 dB.
Read th
e frequency directly from the instrument display.
The H Sine Zoneplate, which provides a constant frequency horizontal sine
signa
l instead of a swept signal, can be used to reduce error in measuring
attenuation at a given frequency.
Set t
he Horz. Frequency parameter to a low value and measure the
amplitude of the entire line.
Nex
t, calculate the –3 dB point (0.707 × the low frequency amplitude).
Finally, increase the Horz. Frequency parameter until the system response
for
the whole line is at the calculated –3 dB level, and read the –3 dB
frequency directly from the instrument display.
Si
nce the ZP Amplitude parameter is adjustable for each of these signals, you
can measure the response at 100%, 60%, or any other level as needed.
T
hese same techniques can be used to measure vertical or diagonal response, by
selecting the appropriate zoneplate signal.
3–184 TG8000 Multiformat Test Signal Generator User Manual
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