Manual Test Procedure R&S SM300
Version 04 76
Service Manual SM300: 1147.1652.00 Instrument Part No SM300: 1147.1498.03
Measurement
1.
Set the levels of two signal generators according to the specifications of
the used mixer.
2. For calibration purposes reduce level of EUT by 40 dB and detune a
signal generator by 20 kHz. Test signal for harmonics, the 2nd and 3rd
harmonic should be more than 30 dB below the fundamental. Measure
and note reference value at 20 kHz on analyzer.
3. Revoke detuning and establish phase quadrature. To do this, set level of
EUT again and detune phase offset on auxiliary generator. Observe
mixer output voltage on oscilloscope until the voltage becomes 0.
4. Read noise voltage on analyzer that is normalized to a bandwidth of 1
Hz (noise level).
Evaluation
Example
Form the difference to the reference level and add 6 dB for the measured
(correlated) second sideband and 40 dB to level switching. If the noise level
of the second signal generator is not at least 10 dB better than that of the
EUT, the noise component of the reference transmitter too has to be
determined and calculated.
The value found gives the correct noise level.
The reference level is to be measured at 12 dBm. At 20 kHz a noise level of -
78 dBm (1 Hz) is determined. The difference is 90 dB. In addition to the
correction for the second sideband (6 dB) and the level switching (40 dB) a
noise level of -136 dB or of -136 dBc (dB with reference to the carrier power)
is obtained. If two identical signal generators are used, the result has to be
reduced by 3 dB for the (uncorrelated) noise power of the reference
transmitter.
The final result is then -139 dBc.
2.4.5.4 I/Q Modulation Frequency Response
Test equipment
Spectrum analyzer (Table 2-1, item 2)
Signal generator (
Table 2-1, item 3).
Test setup
Connect the Rf output of the SM300 to the spectrum analyzer,
connect the signal generator to the I input of SM300.
Test method
By applying a sinewave AC voltage to the I (or Q) input, an amplitude
modulation with a suppressed carrier is generated. The modulation frequency
response is determined by measuring the sidebands as a function of the
frequency of the applied AC voltage.
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