Digital Signal Processing Reference
In-Depth Information
Table 4.6
OFDM
measurement results at
2.4 GHz and 3% EVM
OFDM
Constant
Dynamic
Output power (dBm)
12
.
4
11
.
1
PA E ( % )
6
.
9
8
.
3
Gain (dB)
7
.
9
8
.
6
Table 4.7
Comparison of the results with other works on dynamic supply PAs
Reference
[
4
]
[
9
]
[
29
]
[
30
]
[
31
]
This
work
This
work
Technique
Dyn.
Dyn.
Dyn.
Dyn.
Switched
Dyn.
Dyn.
Dyn.
Technol. PA
Discr.
GaAs
Discr. Bip.
Discr. GaAs
Discr. Bip.
CMOS
CMOS
Technol. Mod.
Discr. GaAs
GaAs
CMOS
Discr. MOS
Discr. MOS
CMOS
CMOS
Supply (V)
-
3.6
3.3
6
5.5
2.5
2.5
f
c
(GHz)
4
0.95
1.9
2.4
2.4
5.2
2.4
P
out
(dBm)
36
20
20.5
15.1
19
16
16.9
PAE (%)
11.7
14
32
25
28
12.5
22.5
ACPR (dBc)
-
−
26
−
45
-
-
-
-
EVM (%)
-
-
4.9
3.2
2.8
-
-
IMD (dBc)
−
50
-
−
30
-
-
−
35
−
35
Mod. Eff. (%)
-
74
85
75
60
86
86
f
s
(MHz)
-
10
16
7
6
24
24
Linearization
-
-
-
DPD
DPD
-
-
Application
TCM
CDMA
CDMA
WLAN
WLAN
-
-
Note: Technol.
=
Technology; Mod.
=
Modulator; Eff.
=
Efficiency; Discr.
=
Discrete; Bip.
=
Bipolar
We can say that there are two main causes for the degradation in linearity with
an OFDM signal input: the difference in the phase between the signals at the supply
and at the output of the PA introduced mainly by the envelope detector, and the
imperfect reproduction of the envelope signal at the PA supply due to the LC filter
(low cutoff and switching frequencies). Nevertheless, Figs.
4.21
and
4.22
show that
the dynamic supply technique provides a relatively large improvement in efficiency
also for OFDM signals. This indicates that the dynamic supply PA can be considered
for use in WLAN applications.
4.6 Conclusion
This chapter presented the measurement results obtained in the characterization of
the dynamic supply RF power amplifier. The high-efficiency, fast modulator and
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