High efficiency poweramplifiers for RF and
Microwaves.
Grupo de Ingeniería de Radio
2
INDEX
1. INTRODUCTION.
2. WIDEBAND CLASS-E HF POWER AMPLIFIER.
3. WIDEBAND VHF CLASS-E AMPLIFIER.
4. S and L BAND HEPAs BASED ON GaN TECH.
5. CONCLUSION.
High efficiency power amplifiers for RF and Microwaves
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INTRODUCTION.
• Communicatton circuits usually exhibit low
power efficiency. Efficiencies as low as 10%
are usual in communications hardware.
• These low efficiency figures cause important
technical problems: high power consumption,
low battery life, bulky cooling systems, etc.
• Comunication circuits are inneficient because
they use low efficiency power amplifiers (PAs)
in their amplification line-up.
• Several techniques have been proposed to
improve the efficiency of PAs, however they
have not benn extensively used.
High efficiency power amplifiers for RF and Microwaves
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• High efficiency power amplifiers use
transistors in switch mode, but switching
operation is difficultat RF & MW.
• High efficiency switch-mode power amplifiers
are nonlinear but nowadays communicattion
services require lineal amplification =>
challenging linearization techniques,
• The high efficiency amplification problem
requires a complex solution combining: high
frequency electronics + power electronics +
solid state technology + digital signal
processing.
Amplification classes
A, AB, B: No switching
Ƞ:↓
LIN: ↑
D, E, F: switching
Ƞ:↑
LIN:↓
INTRODUCTION.
High efficiency power amplifiers for RF and Microwaves
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WIDEBAND CLASS-E HF POWER AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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• Load impedance synthesis concept is specially useful for switchmode power amplifier design at RF & MW.
• The load required to operate into Class-E by this transistor was shynthesized over a one octave bandwidth
• The driver of this amplifier was also designed according to the load synthesis technique. The target was to produce proper waveforms at he gate of the power transistor (3 dB gain imrpovement).
• The amplifier exibited 60% fractional bandwith, 90% peak efficiency and 50W poeak power.
WIDEBAND CLASS-E HF POWER AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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6 MHz 7 MHz 8 MHz
2f0 → f0 12 dB 20 dB 25 dB
3f0 → f0 32 dB 42 dB 57 dB
Harmonicrejection
WIDEBAND CLASS-E HF POWER AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
AMPLIFIER MEASURED PERFORMANCE
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This PA is completely nonlinear => only useful to amplify constant enevelope communication signals: FM, FSK, GSM, etc,
Modern broadband communication services (WCDMA, DVB, WiFi, etc.) use very complex non constant envelopes.
Switchomde amplifers (such as this one) must be linearized to be used with new services.
Envelope Elimination and restoration (EER) and Envelope Tracking (ET) are some of the most effective linearization techniques for switchmode amplifiers.
WIDEBAND CLASS-E HF POWER AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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ET (Envelope Tracking) EER (Envelope Elimination Restoration)
• Efficiency is improved powering a LINEAR amplifer with an aproximate replica (sligthly higher) of the amplified signal envelope.
• A NONLINEAR amplifier is powered and simultaneously amplitude modulated by the envelope of the amplified signal.
WIDEBAND CLASS-E HF POWER AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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5.5 6 6.5 7 7.5 8 8.5 9 9.5 1038.5
39
39.5
40
40.5
41
41.5
42
42.5
Frecuencia (MHz)
Pote
ncia
(dBm
)
Potencia DC Potencia salida
5.5 6 6.5 7 7.5 8 8.5 9 9.5 1050
60
70
80
90
100
Frecuencia (MHz)
Rend
imie
nto
(%)
Average Power Drain Efficiency
7 7.5 8 8.5 9 9.5 1022
24
26
28
30
32
34
36
Frecuencia (MHz)
C/I (
dB)
EER LINEARIZATION PERFORMANCE (WITHOUT PREDISTORTION)
WIDEBAND CLASS-E HF POWER AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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WIDEBAND VHF CLASS-E AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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• This amplifier was esigned upon the load impedance shynthesis technique.
• A Silicon LDMOS transistor was chosen to build it.
• The relatively high output power of this amplifier combined with a relatively low drain voltage yielded a low and difficult to shynthesize load impedance.
• The parasitics of the package made the design even more difficult. A special high frequency transformer was designed to overcome this problem.
• The amplifier exhibited a 40% fractional bandwidth, 90% peak efficiency and 145 W peak output power.
WIDEBAND VHF CLASS-E AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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Gain and harmonic rejection
Frequency (MHz) 88 100 114
IDC (A) @ 28V 6.13 5.86 4.97
Gain @ 28V 14.5 14.5 15.3
2f harmonicrejection (dBc)
14.6 19 21
AMPLIFIER PERFORMANCE
WIDEBAND VHF CLASS-E AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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LINEARIZATION BY MEANS OF EER TECHNIQUE AND PREDISTORTION
WIDEBAND VHF CLASS-E AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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LINEARIZATION RESULTS, TWO TONES TEST.
88 MHz 100 MHz 114 MHz
Carrier frequency (MHz)IMD3 (dBc)
Improvement (dB)Withoutpredistortion With predistorstion
88 23 47 24100 24 47 23114 20 45 25
WIDEBAND VHF CLASS-E AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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OFDM LINEARITY
512 carriers--- Without predistortion--- With predistortion--- Feedthrough
2048 portadoras
--- Without predistortion--- With predistortion--- Feedthrough
WIDEBAND VHF CLASS-E AMPLIFIER.
High efficiency power amplifiers for RF and Microwaves
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EFFICIENCY COMPARATIVE AGAINST NON SWITCHMODE AMPLIFIERS
High efficiency power amplifiers for RF and Microwaves
WIDEBAND VHF CLASS-E AMPLIFIER.
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S and L BAND HEPAs BASED ON GaN TECH.
High efficiency power amplifiers for RF and Microwaves
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High Breakdown Voltage
High Power Density
Low Capacitances
High Load impedance
Compact design High efficiency capability at MW
GaN
S and L BAND HEPAs BASED ON GaN TECH.
High efficiency power amplifiers for RF and Microwaves
GaN advantages at RF and MW
20Linealización de amplificadores de alto rendimiento mediante EER
DRIVER
•NPTB00004•SOIC-8•4W@ 28V •μ = 70%•G = 18 dB•Subopt. Class-E
HEPA
•RF3931•Flanged - ceramic•30W@ 48V •μ = 75%•G = 14 dB• F-1, B, B-E
IN OUT
S and L BAND HEPAs BASED ON GaN TECH.AMPLIFIER ARCHITECTURE
21Linealización de amplificadores de alto rendimiento mediante EER
AMPLIFIER DESIGN
S and L BAND HEPAs BASED ON GaN TECH.
• Designed upon the load impedance shynthesis technique.
• GaN HEMTs solid state devices.
• Non linear HB simulation.
• Measuring waveforms is impossible => simulation + load impedance measurements.
• Pacakaged devices used (no packaged in near future). The package parasitics preclude correct implementation of some amplification classes.
• Load-pull technique used to test and trim the amplifier both simulated an real.
22Linealización de amplificadores de alto rendimiento mediante EER
S and L BAND HEPAs BASED ON GaN TECH.LOAD-PULL SIMULATION
23Linealización de amplificadores de alto rendimiento mediante EER
CONCLUSION.
1. High efficiency power amplifiers (HEPAs) have been researched for
one century but only recent advances in solid state technology, circuit
theory and DSP have made it possible in a practical way.
2. At this moment there are HEPAs examples in scientific literature from
HF to W bands exhibiting effiencies ranging from 90% to 20% .
3. Linearity is an extra requirement for modern HEPAs that demnads the
combination of RF electronics, power electronics and DSP knowledge.
4. Three examples of HEPAs have been shown from HF to S band. They
were designed to be part of linear HEPAs for modern digital
communication services.