11
Amplifier measurement example
Step-by-step instructions for setting up and apply-
ing flatness corrections for the measurement of
an amplifier are shown in Table 7. Gain, absolute
output power, and gain compression measurements
procedures are covered. For more information on
measuring amplifiers, refer to Agilent product note
8510-18, literature number 5963-2352E.
Table 7. Absolute output power and 1 dB compression measurements of an amplifier
8510C Keystrokes Description
Perform the flatness-correction calibration as presented in Table 1
Set up the test port power level
STIMULUS [MENU] Set the test port power below the amplifier’s compression level (P
A
) and within the settable power range presented
{POWER MENU} in Table 4.
{POWER SOURCE 1}
P
A
[x1]
Set up a b
2
measurement and connect a thru
PARAMETER [MENU] Set up the analyzer for a b
2
measurement.
{USER 2 b
2
}
Perform a thru calibration
[CAL] Perform a thru calibration to eliminate the frequency response errors of the port 2 path in the measurement. Be sure to
{CAL#…} include any attenuators and/or adapters which are part of the measurement in the thru calibration. It may be necessary
{CALIBRATE:RESPONSE} to swap adapters for the thru calibration. Any cal set may be selected to access the response calibration in the calibration
{THRU} menu structure.
{DONE RESPONSE}
{CAL SET #}
Connect the amplifier and measure the absolute output power
RESPONSE [MENU] Display the absolute power by entering a magnitude offset (P
A
) equivalent to the test port power level during the thru
{MORE} calibration. Gain can be calculated for any measurement point by subtracting P
in
from P
out
(or P
measured
/P
A
). The gain
{MAGNITUDE OFFSET} can also be measured by performing an S
21
measurement.
P
A
[x1]
[AUTO]
Set up a 1 dB compression measurement and normalize the trace
[DISPLAY] By normalizing the measurement, the first frequency point to drop by 1 dB will be easy to identify.
{DATA AND MEMORIES}
{DISPLAY→ MEMORY 1}
{MATH(/)}
Adjust the display
[REF VALUE] Move the reference line near the bottom of the grid to allow full use of the display.
1 [x1]
[REF POSN]
USE DOWN ARROW
[SCALE]
1 [x1]
Increase power to find the 1 dB gain compression point
STIMULUS [MENU] Increase the test port power 1 dB at a time until the trace visibly drops. Then use the knob to adjust the power until
{POWER MENU} a 1 dB drop in the trace occurs. Note the test port power and use a marker to measure the frequency.
{POWER SOURCE 1}
USE UP ARROW
[MARKER]
Measure the absolute output power at the 1 dB compression point
[REF POSN] Move the reference level back to the center of the screen and display the absolute output power versus frequency.
[DISPLAY] The marker will indicate the amplifier's absolute output power for the1 dB compression point.
{DATA AND MEMORIES}
{DISPLAY:DATA}
[AUTO]
