Technical data

Calibration 3
U2761A Service Guide 37
Amplitude Flatness (–20 dB Range) Adjustment
This procedure calibrates the AC amplitude flatness for high
frequency using –20 dB attenuator. This calibration is
performed using Sine wave at nominal amplitude of
30 mVrms across 50
Ω load.
1 Connect the power meter to measure the output
amplitude of the U2761A as shown in Figure 3- 4.
2 Set the power meter Filter Mode to Manual and Averaging
Length to 500, to improve the measurement stability. Allow
a minimum of 30 s between setting time and collecting
the measurement reading.
3 Use the power meter to perform a 100 kHz AC power
measurement at the output terminal for setup 35 shown
in Table 3- 17. Setup 35 establishes the power reference
for all the remaining setups in Table 3- 17. You must
always perform setup 35 before any of the following
setups.
4 On the power meter, use the Relative Power function to set
the current reading as the reference value. This will allow
you to make future measurement result in dB.
5 Set the power meter Offset to Offset
–20dB
value previously
calculated in Table 3- 14. The power meter will directly
read the flatness error specification relative to 1 kHz.
6 Enter the measured value to the U2761A as described in
“Calibration Procedure” on page 30.
7 Proceed to AC amplitude flatness (0 dB range) adjustment
or exit the calibration mode when necessary.