Operating Manual R&S SMIQ - Volume 1 - Rohde & Schwarz

SMIQTest Procedures5.3.8.6 I/Q ImbalanceMeasurement of imbalanceTest equipment - Spectrum analyzer (Table 5-1, item 2)- Adjustable DC voltage source (Table 5-1, item 12)Test setupMeasurement Connect the spectrum analyzer to the RF output of the SMIQ. Connect the DC voltage source to the I or the Q input. Settings on SMIQ:- Test frequency 900 MHz- Test level 0 dBm- Select STATE ON in the menu VECTOR MOD. 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 andnote down the corresponding RF levels as reference levels.In the menu VECTOR MOD/IMPAIRMENT STATE, select ON andIMBALANCE 10%. Repeat the level measurements. The I level should increase by the set imbalance, the Q leveldecrease by the inverse ratio. With 10%, the I level shouldincrease to 1.1 times, the Q level decrease to 1/1.1 times theoriginal value, i.e. the Q level should be reduced to 0.909 timesthe original value (corresponding to ±0.83 dB).Measurement quadrature errorTest assemblyMeasurementSee section "Test Assemblies", vector modulation Settings on SMIQ:- Level 0 dBm- Test frequency 900 MHz- In the menu VECTOR MOD, select STATE ON,IMPAIRMENT STATE OFF, QUADRATURE ERROR 10°. Generate a modulation signal using the controller and the simulationprogram:- Modulation 16QAM- No coding- SQR filter with α = 0.5- PRBS-9 data sequence- Pulse width and oversampling 32- Length 100 symbols- Symbol clock 10 kHz Make the corresponding settings on the demodulator. Synchronizeto a bit sequence, starting with the 9th symbol, 12 bits long, resultlength 80 symbols. Caution: the mapping of DUT anddemodulator must be in agreement! Select the vector representation on the demodulator. The symbols should be located in a square grid. Select IMPAIRMENT STATE ON on the SMIQ. The symbols must no longer be arranged at right angles; theY axis should be inclined towards the left by 10°, with a setting of-10° it should be inclined towards the right.1125.5555.03 5.29E-9