Transcript The Design of Linearezed PA for Wireless Communications

A Mirror Predistortion Linear
Power Amplifier
Presented By: Khaled Fayed1
Co-Authors: Amir Zaghloul2,3 , Amin Ezzeddine1,
and Ho Huang1
1. AMCOM Communications Inc., Gaithersburg, MD
2. Virginia Polytechnic Institute & State University
3. U.S. Army Research Laboratory
Presentation Outline
 Introduction
 Linearization Techniques
 Mirror Predistortion Technique
– What is it?
– Implementation
– Results
 Conclusion
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Introduction
 PA is the most Power Hungry component in
wireless communication systems
 WiMax, LTE and other new technologies use
high data rates:
 Need higher linearity
 BO not recommended where Efficiency will
suffer
 Solution?
Use Linearization Techniques
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Introduction (Cont…)
 Power: 1 dB Compression Point (P1dB)
Pout
.100%
Pdc
 Efficiency:

 Linearity:
 IM 3@ Pout 
IMD 3  10 log 

P
out


f1 f2
f2-f1
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2f1-f2
3f1-2f2
2f2-f1
3f2-2f1
f1+f2
2f1
2f2
3f1
3f2
Introduction (Cont…)
AM-PM (Deg)
AM-AM (dB)
 PA Linearity Characterization:
AM-AM & AM-PM curves
1 dB
i/p P1dB x
Pin (dBm)
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Pin (dBm)
Linearization Techniques
 Three Major Categories
– Feedback
– Feedforward
– Predistortion
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Linearization Techniques (Cont…)
AM-AM
AM-AM
AM-AM
 Predistortion

+
AM-PM

+
Pin
i/p
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Pin
Pin
AM-PM
AM-PM
Pin
Predistorter
Pin
PA
Pin
Linearized o/p
Linearization Techniques (Cont…)
 Predistortion (Diode PD)
RFC
Vd
DC Block
DC Block
i/p
o/p
Cp
Rd
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RFC
Linearization Techniques (Cont…)
 Predistortion (Diode PD)
– Advantages
 Simple
 Easy to be integrated with PA in a Chip
– Disadvantages
 Very limited linearization
 No tracking with Power or Temperature
 Requires Measurement of both PD and PA nonlinear
performance
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Linearization Techniques (Cont…)
 Predistortion (Cubic PD)
i/p
Predistorter
Linearized o/p
PA
Fundamental tone

+
f
IM3 from Predistorter
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f
IM3 from PA
f
IM3 free output
Linearization Techniques (Cont…)
 Predistortion (Cubic PD)
Atten
Delay
o/p
i/p
Vector Modulator
Cubic Predistorter
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Linearization Techniques (Cont…)
 Predistortion (Cubic PD)
– Advantages
 Relatively simple
 Very good improvement in IMD3 reported (>20dB)
– Disadvantages
 IMD5 and higher degrades
 Vulnerable to Process & Temp variations
 No power tracking
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Linearization Techniques (Cont…)
 Predistortion (Modified Cubic PD)
– Use one more CPD to cancel IM5 independently
IM3 Generating
AMP
IM3 Vector Modulator
IM5 Generating
AMP
i/p
IM5 Vector Modulator
IM3 Cancellation
Signal Cancellation
Delay
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o/p
Mirror PD Linearization
 What is Mirror PD?
– A new Linearization Technique!
– Mitigates deficiencies of both Feedforward & PD by
using a PD that uses a smaller copy or mirror of
the main PA
– This mirror feeds out of phase IM’s to PA input to
get IM free output
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Mirror PD Linearization (Cont…)
Mirror Predistorter
Mirror PA
Att1
D
F
H
B
Pin
Delay1
A
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EA
I
Vector Modulator 1
Delay2
Main PA
K
G
E
C
Vector Modulator 2
J
Pout
Mirror PD Linearization (Cont…)
 This leads to improvement in both IMD3 and
IMD5 with:
– Higher Efficiency than Feedforward (Note that EA
output power and gain requirements are reduced
by the gain of the main PA)
– Generally has better power and temperature
tracking than other PD technique (The mirror
tracks the main PA)
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Mirror PD Linearization (Cont…)
 The copy is realized by using multiple cells of
the mirror PA to build the main PA
 For the shown case Power overhead is 25%
Power Divider
Power Combiner
PA
PA
PA
Mirror PA
PA
PA
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Main PA
Mirror PD Linearization (Cont…)
 Implementation (Hybrid Module)
AMCOM Part # AM204437
AMCOM Part # AM304031
Mirror PA
Att_2
Cplr_6
PA
PA
Att_3
PS_A
Pin
Delay1
Cplr_3
Att_B
Cplr_4
EA
Cplr_5
Cplr_10
PA
Cplr_1
PS_B
Delay2
Cplr_7
Cplr_9
PA
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Cplr_8
Att_A
Att_1
Cplr_2
PA
Pout
Mirror PD Linearization (Cont…)
 Hybrid Module (Picture)
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Mirror PD Linearization (Cont…)
 Hybrid Module (Test Setup)
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Mirror PD Linearization (Cont…)
 Hybrid Module (Test Setup Picture)
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Mirror PD Linearization (Cont…)
 Hybrid Module Results (IMD3 vs. Pout)
Module Measurement
-20
Without linearization
-30
IMD3 (dBc)
With linearization
5 dB
-40
-50
23 dB
-60
-70
-80
26
28
30
32
34
Pout (dBm)
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36
38
40
Mirror PD Linearization (Cont…)
 Hybrid Module Results (IMD5 vs. Pout)
Module Measurement
-30
Without linearization
-40
With linearization
IMD5 (dBc)
-50
-60
5 dB
-70
-80
-90
-100
26
28
30
32
34
Pout (dBm)
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36
38
40
Mirror PD Linearization (Cont…)
 Hybrid Module Results (Efficiency vs. IMD3)
Module Measurement
16.0
Without linearization
14.0
With linearization
Efficiency (%)
12.0
10.0
8.0
4.5 times
6.0
4.0
2.0
0.0
-80
-70
-60
-50
IMD3 (dBc)
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-40
-30
-20
Mirror PD Linearization (Cont…)
 Hybrid Module Results (Bandwidth)
Module Measurement
-20
Without Linearization
WIth Linearization @ 1 MHz spacing
WIth Linearization @ 10 MHz spacing
WIth Linearization @ 20 MHz spacing
IMD3 (dBc)
-30
-40
-50
-60
-70
-80
26
28
30
32
34
Pout (dBm)
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36
38
40
Mirror PD Linearization (Cont…)
 Hybrid Module Results (Temperature)
Module Measurement
-20
Without Linearization
With Linearization @ 38 Deg C
IMD3 (dBc)
-30
With Linearization @ 48 Deg C
-40
-50
-60
-70
-80
26
28
30
32
34
Pout (dBm)
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36
38
40
Conclusion
 A new Linearization technique “Mirror PD”
was presented
 A Hybrid module was built with a P1dB of 41.5
dBm at 3.5 GHz
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Conclusion (Cont…)
 Results Summary
–
–
–
–
–
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IMD3 improved by 23 dB @ 7.5 dB BO
IMD3 improved by 5 dB @ 3.5 dB BO
IMD5 improved by 5 dB @ 8.5 dB BO
Efficiency Improved four times @ IMD3 of -60 dBc
BW > 20 MHz  Sufficient for WiMax channel
Khaled Fayed
Questions?
[email protected]
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