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Report
WIWIC / WIWIC II
&
An Introduction to Power
Amplifier Efficiency
Morten Olavsbråten
Deptartment of Electronics & Telecommunications
Radio Systems Group
July 17, 2015
The WIWIC Project
radio design principles for low-cost terminals and base
stations of WIdeband WIreless Communications
♦ Project start: 01.01.2001
♦ 3 Dr.Ing students (Irene Jensen, Terje Mathiesen,
Karl Jacob Sand)
♦ 1 Post Doc. (Mikael Hammer)
♦ Research topics:
►
►
►
►
Antenna development adapted to plastic injection molding
and metallization manufacturing
Linearization and efficiency improvement of Power Amplifiers
Thermal effects on Power Amplifiers linearity and efficiency
Design of Oscillators, VCO’s and PLL
2
The WIWIC II Project
Topic: Linearized Power Amplifiers for radio frequencies
♦
♦
♦
♦
Project start: 01.01.2004
2 Dr.Ing students (Nima Safari Sirdani, Julia Prigara )
1 Post Doc. (NN)
Research topics:
►
►
►
►
Digital Predistortion
Power Amplifier Behavior modeling
Efficiency enhancements using adaptive dynamic biasing
PA Topologies for high efficiency and linearity
3
NoE ”TARGET”
Top Amplifier Research Groups in a European Team
8 Million € Grant from EC, 4 Years
► 47 Core Members, 11 Associate Members
► 168 Scientists, 67 Ph.D. Students, 16 Countries
►
Manufacturers
Academic Labs
Transmitter Design &
Systems
Amplifier Linearisation
Foundries
Amplifier Design
Modelling
Characterisation
Semiconductor Materials & Devices
(CMOS, Si, SiGe, LDMOS, GaN, SiC, InP, ...)
4
PA Basics – What people think
♦ Unlimited output
power
♦ Constant Gain
♦ 0 phase
distortion
♦ 100% efficiency
5
PA Basics – What we actually have
6
PA Basics – Memoryless model
Input signal : x(t )  A(t )  cos(ct   (t ))
f ( A) j g ( A)
Amplifier Gain : Gain 
e
A
f(A) – AM/AM function (Amplitude)
g(A) – AM/PM function (Phase)
Output signal : y(t )  f ( A)  cos(ct   (t )  g ( A))
7
PA Basics – Amplifier Classes
Class
ClassAB
C
A PA
B
PACurrent
Current
Ideal PA:
0.8
2
1
PA Current
0.7
1
0.8
1.5
0.6
0.8
0.5
0.6
0.6
0.4
1
0.4
0.3
0.4
0.2
0.5
0.2
0.2
0.1
0
0
100
200
300
400
500
600
700
800
900
1000
Degrees
Teoretical eff.:
Linearity:
Modulation:
Other:
Class A
Class AB
50%
50-78%
Very Good
Good
All types All types
Class B
78%
Good
All, no traj.
through zero
Crossover
distortion
Class C
100%
Fair
Constant
envelope
Low power
distortion
8
PA Basics – Amplifier Efficiency
Simple PA AM/AM model
PA Output power
Class A & B PA Efficiency %
6
50
Pmax
4
45
P1dB
40
0
35
Class B
-2
30
-4
25
-6
20
Class A
-8
15
10
-10
5
-12
-34
-32
-30
-28
-26
-24
-22
Input power dBW
-20
-18
-16
-14
-34
-32
-30
-28
-26
-24
-22
-20
-18
-16
-14
Input power dBW
P1dB : 1dB compression point
Pmax : Maximum output power
9
Efficiency %
Output power dBW
2
Modulation – UMTS
 Peak to Average ratio (HS) = 3.5-5 dB
(Peak to Average ratio (BS) = 12 dB (64 signals))
From spec.: Error Vector Magnitude: <17.5%
10
Example – Simple PA AM/AM model
17.5% EVM  Ppeak= 4dBW = 34dBm
Simple PA AM/AM model:
Class A & B PA Efficiency %
PA Output power
6
50
Peak Power
4
45
40
Average Power
0
35
Class B
-2
30
-4
25
-6
20
Class A
-8
15
10
-10
5
-12
-34
-32
-30
-28
-26
-24
-22
-20
-18
Input power dBW
At Po=30.5dBm (1.1W)
 PAE Class A=11%
 PAE Class B=35%
-16
-14
-34
-32
-30
-28
-26
-24
-22
-20
-18
-16
-14
Input power dBW
1Ah / 3V battery:
Class A: 18min talk time!!!
Class B: 55min talk time.
11
Efficiency %
Output power dBW
2
Example – Real PA (AM/AM AM/PM model)
Peak Power
Peak Power
♦
♦
♦
Average Power
17.5% EVM  PO = 34 dBm
At Po=31.5dBm (1.4W)
PAE = 11%
1Ah / 3V battery:
 15 min talk time!!!
12
Example – UMTS Base station
Typical Base Station Class A PA:
Pout = 30 W (45dBm), Efficiency ≈ 2 %
 PDissipated = 1470 W
Large cooling system and size!
Operator with 1000 base stations pay about
13 million NOK/year in electricity!
10 % efficiency  PDiss=270 W  2.6 MNOK/year
13
Other Properties/Requirements
Other PA properties:
♦ IMD – InterModulation Distortion
♦ Spectral Regrowth
♦ PA is NOT memoryless!!! ie. Thermal eff.
Other PA requirements:
♦ ACPR – Adjacent Channel Power Ratio
♦ NCPR – Noise Channel Power Ratio
♦ EVM – Error Vector Magnitude
♦ On/Off settling time
14
PA – What can we do to improve?
♦
♦
♦
♦
Other operating classes: E, F …
Other PA topologies: Doherty, EER …
Dynamic Biasing
Linearization techniques
► Predistortion
(Analog ,Digital)
► Feedback
► Feedforward
►…
15
Conclusion
The Power Amplifier: The next generation
communication system killer???
♦ The PA has a large impact on system
performance! (efficiency, nonlinearity)
♦ Choose a PA that is suitable for the
system and modulation type
♦ PA considerations must be a part of
system planning!
16

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