Filter
Top Products
Bird Model 4391A Power Analyst
14
Measuring
Amplitude
Modulation
Only a forward element is required for this mode. Point the
element in the direction of forward power and press % MOD.
Modulation is displayed directly in percent, provided the
average signal is above 10% and the PEP of the signal is
below 400% of the element’s nominal full scale. For specified
accuracy, the average CW power levels must be greater than
one-third of full scale. Modulation is calculated as follows:
and is therefore limited to the range of 0 to 99.9 percent.
Over-modulation will be indicated as 99.9 percent. Refer to
Table 3.
Table 3
Amplitude
Modulation
Because of the threshold of the RF diode, a modulated signal
which has a minimum power level below 0.3 percent of full
scale will result in high modulation reading with uncertain
accuracy.
MODULATION
Peak Power Minimum Power–
Peak Power Minumum Power+
-------------------------------------------------------------------------------------
⎝⎠
⎜⎟
⎛⎞
100×=
Peak /
CW Power
% Modulation Peak /
CW Power
% Modulation
1.00 0 2.40 55
1.10 5 2.56 60
1.21 10 2.72 65
1.32 15 2.89 70
1.44 20 3.06 75
1.56 25 3.24 80
1.69 30 3.42 85
1.82 35 3.61 90
1.96 40 3.80 95
2.10 45 4.00 100
2.25 50
Figure 10
Amplitude
Modulation
(%)