SME Test Procedure
1038.6002.02 5.13 E-13
Measurement
À Set the levels of the two signal generators according to the
specifications of the mixer used (unmodulated)
À For calibration, set the preamplifier to 0 dB and detune a signal
generator by 20 kHz. Measure and note down the reference value
at 20 kHz at the analyzer.
À Cancel the detuning and make the phase quadrature. Call menu
UTILITIES/PHASE to this effect. Observe the output voltage of the
mixer at the oscilloscope and vary the phase until the voltage
becomes 0.
À Set the preamplifier to 40 dB and read the noise voltage at the
analyzer, normalized to a bandwidth of 1 Hz (noise level).
Evaluation
À Subtract from the reference value and add 6 dB for the second side
band measured (correlated) and 40 dB for the amplification
switchover to the ratio found. If the signal-to-noise ratio of the
second signal generator is not better than the one of the test object
by at least 10dB, the noise component of the reference transmitter
must be determined and subtracted as well.
Example:
Let the reference level be measured to be 12dBm. A noise level of
-78dBm (1Hz) is determined at 20kHz. The difference is 90dB, in
addition to the correction for the second side band (6dB) and the
amplification switchover (40dB) there is a signal-to-noise ratio of
136dB or a noise level of -136dBc (dB with respect to the carrier
power). If two identical signal transmitters have been used, the result
must be decreased by 3dB for the (uncorrelated) noise power of the
reference transmitter.
The final result is then -139dBc.
The following noise levels should be measured and/or not be
exceeded:
Test frequency Noise in 20-kHz ratio
6000 MHz -110 dBc (only SME06)
3000 MHz -116 dBc (only SME03/06)
2000 MHz -120 dBc (only SME03E/03/06)
1000 MHz -126 dBc
500 MHz -132 dBc
250 MHz -137 dBc
125 MHz -140 dBc
< 93.75 MHz -129 dBc
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