high efficiency power amplifiers for rf and …...1. high efficiency power amplifiers (hepas) have...

High efficiency poweramplifiers for RF and

Microwaves.

Grupo de Ingeniería de Radio

[email protected]

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

3

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.


4

• 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.


5

WIDEBAND CLASS-E HF POWER AMPLIFIER.


6

• 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.



7

6 MHz 7 MHz 8 MHz

2f0 → f0 12 dB 20 dB 25 dB

3f0 → f0 32 dB 42 dB 57 dB

Harmonicrejection



AMPLIFIER MEASURED PERFORMANCE

8

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.



9

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.



10

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)



1111

WIDEBAND VHF CLASS-E AMPLIFIER.


12

• 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.



13

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



14

LINEARIZATION BY MEANS OF EER TECHNIQUE AND PREDISTORTION



1515

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



1616

OFDM LINEARITY

512 carriers--- Without predistortion--- With predistortion--- Feedthrough

2048 portadoras

--- Without predistortion--- With predistortion--- Feedthrough



1717

EFFICIENCY COMPARATIVE AGAINST NON SWITCHMODE AMPLIFIERS



18

S and L BAND HEPAs BASED ON GaN TECH.


19

High Breakdown Voltage

High Power Density

Low Capacitances

High Load impedance

Compact design High efficiency capability at MW

GaN



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


AMPLIFIER DESIGN


• 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.


S and L BAND HEPAs BASED ON GaN TECH.LOAD-PULL SIMULATION


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.

high efficiency power amplifiers for rf and …...1. high efficiency power amplifiers (hepas) have...

Documents