AN1714 Datasheet, PDF (37/46 Pages) STMicroelectronics – transceiver demonstration kit description

AN1714
Demonstration board characterization
3
Demonstration board characterization
This chapter includes a series of tests and measurements to characterize the demonstration
board. The characterization concerns the most critical aspects required by European
standards which are:
1. Electro-conducted disturbances
2. Immunity to narrowband conducted noise
3. Output impedance measurement
The results of these measures show a good match and a very close value to the measures
done according to the EN50065-1, EN50065-2-1 and EN50065-7 setup and procedures.
3.1
Conducted disturbance
The EN50065-1 standard describes the test setup and procedures for these kinds of tests.
The measures have been done with 220 V~ and 110 V~ mains voltages. The test pattern
consists of a continuous transmission of a fixed tone (symbol "0") or a repetition of random
bytes.
The output signal has a peak value of 118dBuV (output CISPR-16 measure of the not
modulated signal) that means a 1.6V_rms of signal on the mains.
The spectrum analyzer performs a peak measure instead of a quasi-peak measure. For
continuous sinusoidal signals the two types of measures give the same result.
Figure 29. Conducted disturbance setup
As shown by the spectrum plots the point that is usually the closest to the mask is the 2^nd
harmonic. The borderline condition is obtained with the 110 V~ mains supply and with the
110 kHz channel.
In the 110 kHz channel case the output board filter centered at the 132.5 kHz channel
produces lower attenuation of the harmonic.
The other critical condition is with the 110 V~ supply. In this case the switching regulator
gives a lower supply voltage. The effect is to compress the top of the output sinusoidal
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