Figure 10.4: Relative magnitude of far-field radiation as a function of frequency.
When the spectral envelope of the digital signal (the input into the radiator) is combined with
the frequency dependence of the far-field radiation shown in
Figure 10.4
, we arrive at the
differential radiated emission envelope shown in
Figure 10.5
. Note that the frequency F =
1/T
r
will not necessarily occur at a higher frequency than F = c/2
, as shown in the figure.
The frequencies that will be most likely to radiate (differential mode) are contained between
the frequencies F = 1/P
W
and F = 1/T
r
or F = c/2
(whichever is highest).
Figure 10.5: Resultant differential radiation behavior when far-field characteristics are
combined with spectral input.
RULE OF THUMB: Minimizing Differential-Mode Radiation
Since the magnitudes of the fields are proportional to the loop area, smaller loops
produce less radiated emission. During design, minimize current loops whenever
possible.
Summary :
The frequencies that will be most likely to radiate (differential mode) are contained between the frequencies F = 1/P W and F = 1/T r or F = c/2 (whichever is highest).
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figure,radiation,frequency,farfield,differential,shown,frequencies,spectral,emission,radiated,enelope,104,105