Board description
AN2451
26/55
Doc ID 12791 Rev 3
The spectrum analyzer performs a peak measurement instead of a quasi-peak
measurement, as specified by EN50065-1. For continuous sinusoidal signals the two types
of measurement give the same result.
Figure 18.
Conducted emissions test setup
shows the results for the output spectrum measurement. The EN50065-1
disturbance limits mask (traced in red) may be compared to the typical output spectrum of
the ST7540 reference design board.
Figure 19.
Output spectrum (typical) at 72 kHz, 2400 baud, deviation 1, mains 220V
ac
5.2.2 Noise
immunity
The tests on immunity against white noise and narrow
-
band conducted interferences are
based on two ST7540 reference design boards performing a simplex (unidirectional)
communication. The first board transmits a given bit sequence, while the receiving board
passes the received bit stream to a BER tester software on a PC, which evaluates the
percentage of correctly received bits.
EVALST7540-2
