Digital Signal Processing Reference
In-Depth Information
Fig. 4.16
Measured 2-tone PAE at 5.2 GHz
supply. However, when we consider the
35 dBc limit adopted (
dashed line
), the
dynamic supply operation shows an extended linear range as already suggested by
Fig.
4.14
. The maximum linear output power is 16 dBm (40 mW) for the dynamic
supply and 14.3 dBm (27 mW) for the constant supply.
The PAE
6
isshowninFig.
4.16
, revealing that for all the output power levels
measured, the efficiency of the dynamic supply PA is higher than that of its constant
supply counterpart. In order to have a quantitative indication of the improvement
in efficiency, the ratio between the PAE with dynamic supply and constant supply
is also shown in the figure (
right y-axis
, with 100% meaning equal efficiencies).
For low output power levels, where the dynamic supply technique is more effec-
tive, a relative improvement of a factor of 1.7 (PAE ratio
−
170%) is achieved. For
an equal high linear output power, for example 13.7 dBm (23.5 mW), the absolute
improvement in efficiency is 2%. At the
=
35 dBc linearity limit, the dynamic sup-
ply PA presents a PAE equal to 12.5%, whereas under constant supply operation it
reaches 8.6%. It is worth emphasizing that the power consumption of the modulator
is included in the PAE calculation. Its measured efficiency is between 65% at low
input envelope amplitude levels and 86% at high levels.
−
6
For the calculation of the PAE, the DC power consumption was obtained by multiplying the 2.5 V
power supply voltage by the rms current delivered by it. The rms current was measured with a
true-rms multimeter. The power delivered by the 2.5 V supply includes the DC consumption of
both the modulator and the PA. The consumption of the envelope detection and processing blocks
was not considered in the PAE calculation. For a detailed illustration of the measurement setup,
refer to Chap. 9 (Appendix A).
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