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Chapter 4 135
Making Measurements
Making the Channel Power Measurement
Changing the Display
The AMPLITUDE Y Scale key accesses the menu to set the desired vertical
scale and associated settings:
•
Scale/Div - Allows you to enter a numeric value to change the vertical
display sensitivity. The range is 0.10 to 20.00 dB with 0.01 dB
resolution. The default setting is 10.00 dB. However, since the
Scale
Coupling
is defaulted to On, this value is automatically determined by
the measurement result.
•
Ref Value - Allows you to set the absolute power reference value
ranging from
−250.00 to 250.00 dBm with 0.01 dB resolution. The
default setting is 10.00 dBm. However, since the
Scale Coupling is
defaulted to
On, this value is automatically determined by the
measurement result.
•
Ref Position - Allows you to set the display reference position to either
Top, Ctr (center), or Bot (bottom). The default setting is Top.
•
Scale Coupling - Allows you to toggle the scale coupling function
between
On and Off. The default setting is On. Upon pressing the
Restart front-panel key or Restart softkey under the Meas Control menu,
this function automatically determines the scale per division and
reference values based on the measurement results.
Using the Marker
The Marker key is not available for this measurement function.
Troubleshooting Hints
If an external attenuator is used, be sure to use the Ext RF Atten key to
include the attenuation value in the displayed measurement result.
The channel power measurement, along with the adjacent channel
power ratio measurement and spectrum measurements, can reveal the
effects of degraded or defective parts in the transmitter section of the
UUT. The following are areas of concern which can contribute to
performance degradation:
• DC power supply control of the transmitter power amplifier, RF
power control of the pre-power amplifier stage, and/or I/Q control of
the baseband stage.
• Gain and output power levels of the power amplifier, caused by
degraded gain control and/or increased distortion.
• Amplifier linearity.