Test Procedures R&S SMU200A
1007.9845.82 1.46
E-12
Measurement on path B
Since path B has no wideband I/Q Input, measurement has to be
done using the internal baseband generator.
The measurement is done as described in chapter “Image Rejection
over the Complete Unit” (see below). Use offset frequency 10 kHz.
Instead of reading the suppressed sideband level, read the level of
the residual carrier on test frequency
.
The residual carrier in dBc is the level of the residual signal found at
test frequency referred to the shifted signal (dBc = referred to the
carrier).
I/Q Imbalance
Measurement of imbalance
Test equipment - Spectrum analyzer (Table 1-2, item 24)
- Adjustable DC voltage source (Table 1-1, item 12)
Test setup
Connect the spectrum analyzer to the RF output of the DUT.
Connect the DC voltage source to the I or the Q input.
Measurement Settings on DUT:
RF On
Frequency 900 MHz
Level 0 dBm
ALC State OFF, S&H
I/Q Settings menu:
Source Analog Wideband I/Q Input
State On
Settings on analyzer:
- Center frequency = test frequency, span 1 MHz
- Reference level = test level +3 dB
- Scale 1 dB/div
First measure the undistorted level as a reference. To this end, apply
a DC voltage of 0.500 V to the I and then to the Q input and note
down the corresponding RF levels as reference levels.
Select Impairments State On and Imbalance 10% on the DUT.
Repeat the level measurements.
The Q level should increase by the set imbalance, the I level
decrease by the inverse ratio. With 10%, the Q level should
increase to 1.1 times, the I level decrease to 1/1.1 times the
original value, i.e. the I level should be reduced to 0.909 times the
original value (corresponding to ±0.83 dB).
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