zvxplus application: power amplifier design
TRANSCRIPT
ZVxPlus Application
PA Design
April 2009
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Introduction
The power amplifier Figures of merit Concept of load line Tuning in Practice: Source and load pull Classes of operations Conclusion
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The power amplifier
PiP(f )
PDC
non-linear
Pdiss
o
PoP(f )o
oP(f ≠f )o
minimal input power
to control conversion
conversion of DC power, into RF power,at
PDCPoP(f )o
fo
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Figure of merit
Efficiency: quality factor for DC consumption
Power Added Efficiency (PAE): ratio between the RF power 'added' by the amplifier and the DC power required for this addition.
η=P(f )+P i o DC
P(f )Do o
PAE=P DC
P - PDo i
linearity: Class A: excellentClass AB: between A and BClass B: moderateClass C: poor
η: Class A: 50%Class AB: between A and BClass B: 78.5%Class C: >78.5%
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Concept of load line
i
idrain
vdrain
Z =R L L
vin
VDDVGG VDD
IDD
VMax
IMax
IDDD
DVDD
DVKnee
DD
R = L
V -Max VKnee
IDMax
R = L
V -Max VKnee
IDMax
LOADLINE
DC IV CurveVGG1
VGG2
VGG2
RL
bias point
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Classic Source / load pull
vin
VDDVGG
power meter
spectrum analyser
Power oriented
sourcetuner
loadtuner
Optimal load@ f0
vdrain
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Source / load pull with the ZVxPlus
loadtuner
Active injection@ 2f0Optimal load
@ f0DUT
VGG
VDD
VSG(control amplitudeand phase)
vdrain
idrain
50Ω
Optimal input match
No power meter neededNo spectrum analyser needed
This can be done using the ZVxPlusand we get the waveforms for free
sourcetuner
a b b a1 1 2 2
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Classes of operation
Classes of operations Class A
Class AB
Class B
→ Loadline?
→ Drain current and drain voltage waveforms?
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Classes of operation: Class A
IDD
VG
IDMax
2 A
VDD
IDD
VMax
IMax
IDMax
2
DVDD
DVKnee
t
VDD
DVD
VDdrain Idrain
IDMaxV
D Max
t
theoretical=50%
if V Knee=0V
RL=V DD
0.5 I Max
withV DD≈V Max−V Knee
2 V Knee
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Fundamental load tuning
Synchroniser
Port 1
Port 3ExcitationSource a1
20 dB
b1 a2b2 a3
Vg Vd
20 dB
Synchroniser
Optimal load@ f0
50Ω
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Class A in practice: Overrange
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Overrange SolutionAdding a characterised 6dB attenuator in a2 channel on the fly!
Synchroniser
Port 1
Port 3ExcitationSource a1
20 dB
b1 a2b2 a3
Vg Vd
20 dB
6 dB
Synchroniser
Optimal load@ f0
50Ω
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Class A in practice
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Classes of operation: From Class A to AB, the first step
IDD
V
D
G
A
VDD
IDD
VMax
IDMax
IDMax
2
DVDD
DVKnee
t
VDD
VD
VDdrain
t
AB
Clipping!! Idrain
IDMaxV
D Max
Change bias point
The drain voltage contains harmonics → goal is a sine wave drain voltage
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Class AB, first step in Practice
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Harmonic output termination: tuned load
i1
i , , ...1 i2 ,i3idrain
vdrain
Z =R @ fL L o
Z =0 @ 2f , 3f , ... L o o
vin
VDDVGG
R = L
V DD
ID
@f o
In case of :- a perfect harmonic short- maximum voltage swing of 2V- no knee region
the optimum value of load resistance will be:
DD
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Classes of operation: Class AB
IDD
VG
A
VDD
IDMax
DD
t
VDD
t
ABA
AB
DVD
VDdrain Idrain
IDMax
DNo clipping!!
theoreticalη >50% and < 78.5%
α/2
VD Max
due to:- termination at harmonics- increased input signal- shift of V
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Harmonic active tuning
Synchroniser
Port 1
Port 3ExcitationSource a1
20 dB
b1 a2b2 a3
Vg Vd
20 dB
20 dB
Synchroniser
Active injection@ 2f0Optimal load
@ f0
VSG(control amplitude
and phase)
50Ω
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Class AB in practice
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Classes of operation: Class B
IDD
VG
A
VDD
DD
IDMax
DD
t
VDD
t
AB AB
VD
VDdrain Idrain
IDMax
BAB
theoreticalη=78.5%
α/2
VD Max
Note: in case of a perfect short at all harmonics
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... to Class B
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Conclusion
Fast Power Amplifier Design using ZVxPlus has been demonstrated.
Using the ZVxPlus, a RF Design engineer can do on the fly a concrete application design, with one single tool. This tool gives all the information needed for the design.
It will surely open new domains and applications.
For more information [email protected]
www.nmdg.be