Promax MO-180 Manual De Usuario página 103

USER'S MANUAL MO-180
Let's assume we have an RF amplifier with parameters α
1 and α
= 0.05. These curves are shown in Figure 5. The top plot shows in blue the
φ
AM-AM characteristic normalised with respect to the input power (i.e. A(r)/r squared)
for powers ranging from —12 to + 18 dB. The bottom plot shows in blue the AM-PM
characteristic.
Figure 5.- AM-AM, AM-PM curves based on a Saleh model (blue) and amplitude and phase of
On the same plots in red we show 16 logarithmically-spaced points. This
spacing provides more samples in the area where the two curves depart more from
linearity and thus where more density of points is needed. Given these 16 abscissae P
expressed in dB, the complex correcting gains can be obtained as follows:
P
n
p =
where . The correcting phases are given by:
10 10
n
The values computed used the two equations above are shown superimposed
on the red curves. The plotted correction gain for each point is G
abscissae and correction gains as calculated using Eqs. (1) to (3) are collected in
Table 1. The three right-most columns would be the ones to be programmed into the
modulator.
04/2008
the corresponding complex correcting gain (red).
2
α − α −
a a
=
g
n
β
2 p
a
− α
( )
φ = − Φ =
g
n n
+ β
1
= 1, β
a
β
4 p
a n
n
2
g
φ
n
2
g
φ
n
— P
n
= 0.017, α
=
φ
a
n
. These power
n
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