Measuring Gain And Reverse Isolation Simultaneously - HP 8753E User Manual

Measuring Gain and Reverse Isolation Simultaneously

Since an amplifier will have high gain in the forward direction and high isolation in the reverse
direction, the gain (E&l) will be much greater than the reverse isolation (SH.). Therefore, the
power you apply to the input of the amplifier for the forward measurement (SZl) should be
considerably lower than the power you apply to the output for the reverse measurement
saturated. A higher power in the reverse direction keeps noise from being a factor in the
measurement and accounts for any losses caused by attenuators or couplers on the amplifier's
output needed to lower the output power into the analyzer. The following steps demonstrate
the features that best accomplish these measurements.
1 . Press @J '~~~~~~.~~~~~:~~::.
Coupling the channels allows you to have the same frequency range and calibration applied
to channel 1 and channel 2.
Uncoupling the port power allows you to apply different power levels at each port. In
port 2 power is set to 0 dBm for the reverse isolation measurement (S12).
port 1.
Press (-2) (Meas] ;:f&m$@.;:;~ -~~~~:~~~~~~ (Menu) ~~~~, and set the power level for
port 2.
5. Perform an error-correction and connect the amplifier to the network analyzer. Refer to the
You can view both measurements simultaneously by using the dual channel display mode.
Refer to Figure 2-49. If the port power levels are in different power ranges, one of the
displayed measurements will not be continually updated and the annotation tsll will appear
on the left side of the display. Refer to "Source Attenuator Switch Protection"section in
Chapter 6, "Application and Operation Concepts," for information on how to override this
state.
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Making Measurements 248