RAWCON January 2009

L.T.I. 609-584-8424 www.lintech.com

ALLEN KATZ

The College of New Jersey/Linearizer Technology, Inc.

WIDEBAND

ANALOG PREDISTORTION LINEARIZATION

FOR HIGH POWER AMPLIFIERS

RAWCON January 2009

Objective

TO DISCUSS THE STATE OF THE ART IN ACHIEVING

WIDEBAND LINEARIZATION OF HIGH POWER

AMPLIFIERS (HPAs)

USING ANALOG PREDISTORTION

NECESSARY FOR

MULTI GHz/MULTI OCTAVE OPERATION

CONSIDER SSPAs, TWTAs and KPAs

RAWCON January 2009

REVIEW THE BASIC PD LINEARIZATION CONCEPT

DISCUSS WAYS OF ACHIEVING WB PERFORMANCE

- SINGLE WIDEBAND (WB) LINEARIZER

- COMBINING MULTIPLE SINGLE BAND LINEARIZERS

SHOW CHARACTERISTICS OF SOME WB LINEARIZERS

DISCUSS MULTI-OCTAVE LINEARIZER PROBLEM

PROVIDE DATA FOR A QUAD-BAND LINEARIZED HPA

PRESENT CONCLUSIONS

Outline

RAWCON January 2009

PD Linearization Overview

+_ =

PoL PoA Pout

PiL PiA Pin

+

IN PREDISTORTIONLINEARIZER

H

PA

OUTPUT

FOR WB PERFORMANCE OVER FREQUENCY:

• MUST CORRECT BOTH GAIN AND PHASE

• MUST EQUALIZE LINEAR GAIN AND PHASE (DELAY)

• MUST MATCH NON-LINEAR CHARACTERISTICS OVER FREQUENCY

RAWCON January 2009

THERE IS INTEREST IN VERY WB LINEARIZATION

APPLICATIONS INCLUDE MULTI-FUNC COM, EW & RADAR

LINEARIZERS CAN BE MADE WITH > 3 OCTAVES OF BANDWIDTH

Very Wideband Linearizer

2 GHz 20 GHz

• USEFULL LINEARIZER

CHARACTERISTICS

< 3 GHz TO > 20 GHz.

• ~3 dB GAIN INCREASE

FROM 6 TO 16 GHz.

• INCREASING PHASE

CHANGE

RAWCON January 2009

BELOW IS SHOWN AN EXPERIMENTAL Ka-BAND WB LINEARIZER

FOR TWTA (ΔG > 4 dB & ΔPHASE 50°) APPLICATION

WITH BANDWIDTH > 10 GHz (26 TO 36 GHz)

Very Wideband Linearizer

START 26 GHz STOP 36 GHz

SMALL Signal

Large Signal

SMALL Signal

Large Signal

RAWCON January 2009

BELOW IS SHOWN AN EXPERIMENTAL K-BAND WB LINEARIZER

FOR TWTA APPLICATION (ΔG > 4 dB & ΔPHASE 40°)

WITH BANDWIDTH > 10 GHz (<20 TO >30 GHz)

Very Wideband Linearizer

RAWCON January 2009

ΔGain ~ 4 dB

Expansion

ΔPhase ~ 40º

Waveguide PD

84 GHz

Power Sweep

0.25 Volts

20º/div

2dB/div

ΔGain ~ 4 dB

Expansion

ΔPhase ~ 40º

Waveguide PD

84 GHz

Power Sweep

0.25 Volts

20º/div

2dB/div

E-band Linearizer

RAWCON January 2009

1 dB CP IS MOVED > 6 dB CLOSER TO SAT FROM 6 TO 16 GHz

PHASE SHIFT IS REDUCED FROM > 30° TO < 10 ° OVER THIS BAND

Very Wideband Results with GaN SSPA

RAWCON January 2009

2-TONE CARRIER TO INTERMOD (C/I) IS A COMMON MEASURE OF

DISTORTION REDUCTION.

C/I INCREASE OF 5-11 dB FOR OPBOs OF 5–8 dB

Very Wideband Results with GaN SSPA

Worst Case C/I at 6, 10, and 16 GHz

15.0

20.0

25.0

30.0

35.0

40.0

45.0

2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0

OPBO (in dB)

C/I r

ati

o (

in d

Bc)

6 GHz Non-lin 6 GHz Lin 10 GHz Non-lin 10 GHz Lin 16 GHz Non-lin 16 GHz Lin

AT 6, 10 & 16 GHz:

RAWCON January 2009

DYNAMIC BANDWIDTH IS A CONCERN AT MW.

HPA’s CAN HAVE A WIDE OPERATIONAL BANDWIDTH (corrects the distortion of a narrow, fractional, bandwidth signal across the full band.)

BUT ALSO NEED TO WORK WELL WITH A VERY WIDE BAND SIGNAL, OR MULTIPLE WIDELY SPACED SIGNALS.

NPR of two noise pedestals linearized simultaneously

Pedestal 1

2 GHz Spacing

Pedestal 2

Very Wide Dynamic Bandwidth

RAWCON January 2009

• IM AND HARMONIC DISTORTION A PROBLEM

• 2F1, F2-F1, 2F2-F1 AND 2F1-F2 PRODUCTS OF MOST CONCERN

• MOST PREDISTORTERS CORRECT ONLY ODD ORDER DISTORTION

F2-F1 2F1-F2 2F2-F1 2F1

THIRD ORDER

AM COMPRESSION TERMS

F1 F2

FREQUENCY

EMISSION LIMIT

FOR WB AMPLIFIERS (> OCTAVE BW) - EVEN AND ODD

ORDER DISTORTION MUST BE CONSIDERED

Multi-Octave Linearizer

RAWCON January 2009

• USE PRE-DISTORTION LINEARIZER TO MINIMIZE ODD ORDER

INTERMODULATION DISTORTION

• USE PUSH-PULL TO MINIMIZE 2ND HARMONIC & F2-F1 PRODUCTS

• PUSH-PULL PROVIDES > 25 dB OF SUPPRESSION

UTILIZE PUSH-PULL PA/LINEARIZER DESIGN

TO MINIMIZE EVEN ORDER DISTORTION

Multi-Octave Linearizer

RAWCON January 2009

PUSH-PULL EVEN HARMONIC SUPPRESSION

- PA SHOWED SIMILAR RESULTS

Linearizer Second Order Harmonics

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

-20 -15 -10 -5

Carrier Power (dBm)

Harm

on

ic P

ow

er

(dB

c)

Single Ended Ver 2 Push-Pull NLG

Multi-Octave Linearizer

RAWCON January 2009

+ ALLOWS OPERATION OVER A LARGE, CONTINUOUS AND UNRESTRICTED FREQUENCY BAND

+ ALLOWS USE OF VERY WIDEBAND MODULATIONS AND SPECTRAL SPREADING TECHNIQUES

+ CAN CORRECT FOR IN BAND HARMONIC (BOTH EVEN AND ODD ORDER) & F2-F1 PRODUCTS

+ MAY PROVIDE ENHANSED POWER BY CONTROL OF HARMONICS

− MORE DIFFICULT TO ALIGN

− REQUIRES EQUALIZING TWTA GAIN AND PHASE DELAY OVER FREQUENCY RANGE OF INTEREST

− GENERALLY, THE NARROWER THE BANDWIDTH THE BETTER THE PERFORMANCE THAT CAN BE ACHIEVED

Very Wideband Linearizers

RAWCON January 2009

Multi-band Linearizers

SWITCHING BETWEEN MULTIPLE SINGLE BAND LINEARIZERS IS

ANOTHER WAY TO OBTAIN WB PERFORMANCE

DAUL & TRI BAND LINEARIZERS

HAVE BEEN IN PRODUCTION

FOR SEVERAL YEARS

RAWCON January 2009

A 6 TO 18 GHz TWTA WAS CORRECTED FOR

DISTORTION OVER THE FULL C, X, KU, AND DBS

SATELLITE BANDS WITH A QUAD-BAND LINEARIZER.

THE L-TWTAs WERE FIRST POWER SWEPT USING A

NETWORK ANALYZER AND ADJUSTED FOR FLAT GAIN

AND PHASE VERSUS RF INPUT DRIVE.

TESTING WAS THEN CONDUCTED WITH DIFFERENT

SIGNAL SOURCES ON EACH BAND.

Quad-BAND Linearized HPA Performance

RAWCON January 2009

1 dB COMPRESSION POINT MOVED FROM ~ 5 dB FROM SAT TO < 2 dB

ΔPHASE from SMALL SIGNAL TO SAT REDUCED FROM > 45° TO < 1°

TWTA

L-TWTA-

TWTA f

TWTA

Gain 1dB/

Pout

L-TWTA f

L-TWTA

Quad-Band L-TWTA @ C-Band

MAGNITUDE & PHASE ARE

IMPORTANT INDICATORS OF

PERFORMANCE

RAWCON January 2009

1 dB COMPRESSION POINT MOVED FROM ~ 6.5 dB FROM SAT TO < 2.5 dB

ΔPHASE FROM SMALL SIGNAL TO SAT REDUCED FROM > 45° TO < 2°

Quad-Band L-TWTA @ X-Band

TWTAL-TWTA

TWTA Ø

L-TWTA Ø

L-TWTA

TWTA

MAGNITUDE & PHASE ARE

IMPORTANT INDICATORS OF

PERFORMANCE

RAWCON January 2009

Quad-Band L-TWTA @ K-Band (DBS)

Power Out

TWTA

Gain 1dB/

L-TWTA f

L-TWTA

TWTA f

TWTA

L-TWTA

Phase 5º/

MAGNITUDE & PHASE ARE

IMPORTANT INDICATORS OF

PERFORMANCE

1 dB COMPRESSION POINT MOVED FROM ~ 4 dB FROM SAT TO < 0.5 dB

ΔPHASE FROM SMALL SIGNAL TO SAT REDUCED FROM > 60° TO < 5°

RAWCON January 2009

AT X-BAND THE LINEARIZER PROVIDES A 15 dB IMPROVEMENT

AT 4 dB OPBO WHEN OPTIMIZED

TWTA

L-TWTA

Quad-Band: Reduction of 2-Tone IMD

RAWCON January 2009

MPM Linearity @ C, X, Ku, and K Band

10

15

20

25

30

35

40

45

50

2 3 4 5 6 7 8 9 10OPBO in dB

C/I in d

B

C, X, Ku, and

K Band

Ku

C, X

K

>15 dB IMPROVEMENT IN C/I OBTAINED @ 5 dB OPBO BY LINEARIZING

ALSO A >6 dB POWER INCREASE FOR C/IS > 30 dB

6dB

Quad-Band: Reduction of 2-Tone IMD

TWTA

RAWCON January 2009

SPECTRAL REGROWTH IS REDUCED BY > 20 dB AT 6 dB OPBO

BPSK SHOULD YIELD ~ 1 dB POORER PERFORMANCE

8-PSK SHOULD YIELD ~ 1 dB BETTER PERFORMANCE

L-TWTA Spectral Regrowth

Linearized MPM SR for QPSK

15

20

25

30

35

40

45

50

0 1 2 3 4 5 6 7

OPBO (dB)

SR

in d

B

MPM

L-MPM

Linearized TWTA SR for QPSK

TWTA

LTWTA

RAWCON January 2009

A 40 MHz NOISE PEDESTAL AT X-BAND WAS USED FOR THE NPRMEASUREMENT

THIS IS A TYPICAL BW OF MOST SATELLITE TRANSPONDER CHANNELS

THE RESULT: FOR AN NPR OF 20 dB, THE LINEARIZER ACHIEVES A 4.5dB INCREASE IN EFFECTIVE OUTPUT POWER

L-TWTA NPR/WCDMA Performance

Linerized MPM at X-Band

5

10

15

20

25

30

35

1 2 3 4 5 6 7 8 9 10 11

OPBO in dB

NP

R in

dB

MPM

L-MPM

Linearized TWTA at X-Band

TWTA

L-TWTA

RAWCON January 2009

THE ABILITY TO LINEARIZE HPAs OVER VERY WIDE BANDWIDTH

(> 10 GHz) IS CLEARLY ILLUSTRATED.

THE ABILITY TO PRODUCE LINEARIZERS WITH DESIRED NON-

LINEAR CHARACTERISTICS OVER A CONTINUIOUS MULTI-OCTAVE

BANDWIDTH IS SHOWN.

IMPROVEMENT OF BOTH IMD AND HARMONIC DISTORTION CAN BE

OBTAINED.

GREAT IMPROVEMENT OF C/I, SR AND NPR CAN BE ACHIEVED AT

SELECT BANDS OVER A VERY LARGE BANDWIDTH (C TO K) BY

COMBINING MULTIPLE LINEARIZERS.

IN GENERAL THE NARROWER THE BANDWIDTH THE HIGHER THE

IMPROVEMENT, BUT SUBSTANCIAL IMPROVEMENT OVER LARGE

CONTINUOUS BANDWIDTHS OF MORE THAN AN OCTAVE CAN BE

ACHIEVED.

Conclusions