전력 증폭기
능동초고주파공학 2 2
Contents
• Introduction
• Devices
• Load-Pull
• Power Amplifier Classes (A,B,C,D,E,F)
• Example
• Linearity
• Composite PA
Linearity and Modulation
Contents
• Basics of Digitally Modulated Signals
• Envelope Simulation Concept
• Linearity Metrics
능동초고주파공학 2 4
Digital Baseband Signal
• Bit Rate=1/Tb
1 0 1 1 0 0
Tb
I-Q Modulation
• x(t)=I(t)cos
ω
ct+Q(t)sinω
ct– I(t): In-phase signal
– Q(t); Quadrature signal
• Symbol Rate=Bit Rate/2n
능동초고주파공학 2 6
1 0 1 1 0 0
Tb
Constellation Plot
QPSK(Quadrature Phase Shift Keying) 16QAM(Quadrature Amplitude Modulation)
EVM(Error Vector Magnitude)
능동초고주파공학 2 8
( ) ( )
{
2 2}
1
max
1 N
j j j j
j
I I Q Q
EVM N
v
=
− + −
= ∑
Raised Cosine Filter
1 0 1 1 0 0
Tb
0.0 0.2 0.4 0.6 0.8 1.0 1.2
Impulse Response h(t)
α=1 α=0.75
Frequency Response of RC Filter
능동초고주파공학 2 10
Envelope Signal
Envelope Simulation
능동초고주파공학 2 12
Example
Baseband Signal
능동초고주파공학 2 14
Constellation
-0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5
-0.6 0.6
-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4
-0.5 0.5
TrajConst
Spectrum
능동초고주파공학 2 16
-100 -50 0 50 100
-150 150
-120 -100 -80 -60 -40 -20
-140 0
freq, KHz
Spectrum
HW
• ADS의 examples/Tutorial/ModSources_prj 디 렉터리에서 QAM_16을 열고, 및 파형을 도시하 고, 이의 raised-cosine-filter를 통과한 파형을 도시하시오. 또한 성상도를 도시하고 변조된 파 형의 스펙트럼 및 출력 분포를 도시하시오.
능동초고주파공학 2 18
Linearity Problem
• Distortion in Power Amplifiers
• Various performance metrics
– IMD3(Third Order Inter-modulation Distortion)-FM – ACPR(Adjacent Channel Power Ratio)-CDMA
– EVM(Error Vector Magnitude)-Digital Modulation – BER(Bit Error Rate)
• Simulation Tool: Envelope simulation
2-tone Measurement
3
3rd Order Intermodulated Power Fundamental Power
Generally Used for Specifying Distortion in FDM/FDMA
• IM =
•
2 2 1 2 2 1
f f f f f
IMD3 and TOI
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1 3
1 3
IMD3 3
IMD3 2 TOI IMD3
2
o o
o
y P x
y P x
y y x
P
= +
= − +
→ = → =
= +
TOI: Third Order intercept
IMD3: 3rd Order Intermodulation
Example IMD3
Results
능동초고주파공학 2 22
3 1 3
3 1
2
(3 1 3)
40.35 dBm
2
IMD m m
TOI IMD m
m m
= −
= +
× −
= =
ACPR (Adjacent Channel Power Ratio) Measurements
;
ADS Measurement;
VloadFund = vload[1]
IloadFund = iload.i[1]
mainlimits = {-16.4 kHz, 16.4 kHz}
UpChlimits = {mainlimits + 30 kHz}
LoChlimits = {mainlimits - 30 kHz}
i i
B
i i
BW
P f ACPR P f
∆
∆
• =
∆
•
∑
∑
Example
능동초고주파공학 2 24
Results
ACPR Calculation
• ACPR(1)=-45.96dB
• ACPR(2)=-44.03 dB
능동초고주파공학 2 26
Eqn UpCh={885 kHz, 915 kHz}
Eqn LoCh={-915 kHz, -885 kHz}
Eqn ACPR=acpr_vr(V_fund, 50, mainCh, LoCh, UpCh,"Kaiser")
EVM (Error Vector Measurement)
• ESA-E Series Spectrum Analyzers
Modulation Analysis Measurement Personality
능동초고주파공학 2 28
Measurement Display
Agilent Technologies, User’s, Programming, and Measurement Guide,Feb, 2002 .
Composite Amplifiers
Contents
• Linearity Improvement
– PDA(Pre-Distorted PA) – Feed-Forward
– EER
• Efficiency Enhancement
– Doherty PA
능동초고주파공학 2 30
Pre-distortion Concept
Design
능동초고주파공학 2 32
Pre-Distorter Example
0 −90
RA RA
Input Output
Example 9.14
능동초고주파공학 2 34
3
1 3
L a p a p
υ = υ + υ
3 3
p i b i
υ = +υ υ
(PDA) 전력증폭기의 특성이 vL=a1vi-a3(vi)3로 표시될 때, 이것에 알맞은 소신호 이득이 1 인 전치왜곡기를 구현하시오. 여기서 a1=10, a3=0.109a1이다. 또한 전력증폭기와 설계된 전치왜곡기를 포함한 전력증폭기의 입출력 특성을 비교하고, Pin=10 dBm에서 2-tone 특 성을 비교하시오.
Results
능동초고주파공학 2 36
Feedforward Concept
Feedforward Amplifier
능동초고주파공학 2 38
EER (Envelop Elimination and Restoration)
• Kahn
Efficiency Boost
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Problem
• Efficiency drops as RF output Power decreases
• Generally Peak power usage is small portion of time
G. Hanington, et al, “High-Efficiency Power Amplifier Using Dynamic Power-Supply Voltage for CDMA Applications,”
IEEE Trans. Microwave Theory and Tech., Vol. 47, No. 8, August 1999
Reverse means Mobile to Base
Doherty Amplifier Efficiency
능동초고주파공학 2 42
Doherty amplifier
Small input power Peaking Amp OFF Main Amp sees High Impedance Larger Gain Better Efficiency
Large input power Peaking Amp ON Main Amp sees Low Impedance Main Amp Higher Power Results in Efficie
• → →
→ →
• → →
→ → ncy at High Power
Transfer Characteristics
