Agilent Technologies 8719D, User Manual

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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 will be much greater than the reverse isolation Therefore, the
power you apply to the input of the amplifier for the forward measurement should be
considerably lower than the power you apply to the output for the reverse measurement
By applying low power in the forward direction, you’ll prevent the amplifier from being
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,
Coupling the channels allows you to have the same frequency range and
to channel 1 and channel 2.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Uncoupling the port power allows you to apply different power levels at each port. In
Pigure the port 1 power is set to -25 for the gain measurement and the
port 2 power is set to 0 for the reverse isolation measurement
I’
i i ii . . .
port 1.
5. Perform an error-correction and connect
the
amplifier to the network analyzer. Refer to the
“Optimizing Measurement Results” chapter for error-correction procedures,
You can view both measurements simultaneously by using the dual channel display mode.
Refer to Pigure 2-50. If the port power levels are in different power ranges, one of the
displayed measurements will not be continually updated and the annotation will appear
on the left side of the display. Refer to “Source attenuator switch protection” in Chapter 6,
“Application and Operation Concepts,” for information on how to override this state.
M a k i n g M e a s u r e m e n t s