JUNE, 2012
Power Amplifier Linearization using RF Pre-Distortion
1
Semiconductors for Wireless Communications
General principles
Overview/Block Diagram of DPD and RFPD
RFPAL System architecture & Implementation
PA Linearization Overview
Semiconductors for Wireless Communications
Predistortion Principle
3
No predistorion
With predistorion
5-10 x BW expansion
Semiconductors for Wireless Communications
Digital Pre-Distortion (DPD)
4
Without PA/DUC/CFR : Power consumption ~5.4W
Up-ConverterDPDDUC
CFR
Driver & PA
PwrDet
PwrDet
LO
DSP
5xCLK
f
Wanted Signal + Predistortion
= ~ 5 x Wanted Signal
f
Wanted Signal
f
0 LO0
0.3W1.5W
0.1W
0.8W0.6W
0.1W
ADC
DAC
DAC
0.8W
Clock Generator
Down-Converter
0.4W
0.8W
ADC
f
LO
Wanted SignalWanted Signal +
Predistortion= ~ 5 x Wanted Signal
Filter / Duplexor
Semiconductors for Wireless Communications
RFPAL (RF PA Linearization)
5
Without PA/DUC/CFR Power consumption ~1.4W
Driver & PA
Filter / Duplexor
LO1xCLK
ScinteraRFPAL
ff f f
0 LO LO LO
0.1W 0.4W
Clock Generator
Up-Converter
0.1W
0.8W
DUCCFR
DAC
DAC
Optional digital link
to BB
Wanted Signal + Predistortion
= ~5 x Wanted SignalWanted Signal
Wanted Signal
Wanted Signal
Semiconductors for Wireless Communications
RFPAL System Architecture & Implementation
Semiconductors for Wireless Communications
RFPAL Application
7
Semiconductors for Wireless Communications
RFPAL System Architecture
8
DIGITAL SIGNAL PROCESSOR (DSP)FFT, error metric, etc.
Digital Controller
RF VGAQPS
0o
90o
Voltage & Timing references, LO Generation, etc.
CORRECTION PROCESSOR
Memory
MONITOR
RFIN RFOUTCorrection Signal
RFFBFeedback Signal
Input Monitor Path
Feedback Monitor Path
RF PA Linearizer
ADC
ADC
OptionalDigital Interface
I
Q
DAC
VOLTERRASERIES
IQ
DAC
VGA
VGA
POWER DETECTOR
CoefficientDACs
Volterra SeriesGenerator
PDET AGC
Semiconductors for Wireless Communications
2.54 cm
9
Scintera Advantages
Single chip CMOS linearization solution Easy to evaluate and design in Simplifies TX chain
High system efficiency Very low power consumption
Low system cost Small footprint Future proof
In-system & in-field reprogrammable RFin/RFout supports stand-alone PAs Waveform & modulation independent Power Amp Independent
Linearize even lowest power PAs Robust & field-proven solution
2.54 cm
Semiconductors for Wireless Communications
More Complete Information on Theory of Operation and Datasheets Available on Line at www.scintera.com or Richardson RFPD website Please Visit Us at Booth # 208
Semiconductors for Wireless Communications
Additional Slides
Semiconductors for Wireless Communications 12
Analog Volterra Series
∑∑==
=5
1mp
2.mp,2.m
4
1pOUT )-(trc(t)V τ~(t)r(t)V 2
IN =
C1,2
C1,4
C1,6
C1,8
C1,10
X2
X4
X6
X8
X10
Delay 1= τ1 Coefficient DAC’s
Delay 2= τ2
Delay 3= τ3
Delay 4= τ4
Vout(t)
Vin(t)
Semiconductors for Wireless Communications 13
RFPAL Key Architectural Attributes Analog (RF & BB), Digital (high & low-speed) and SW partitioning minimize power & area
Computation of correction terms in digital (software and hardware) domain Application of correction in the analog domain
RF and most of baseband analog circuitry is unclocked enables robustness and flexibility for various modulation schemes & carrier frequencies.
Flexible Work Function Synthesizes wide range of PA AM/AM and AM/PM compensation and memory compensation (1ns - 300ns) Enables robust adaptation (orthogonal basis terms of work function)
Robust performance with process, voltage, aging and temperature variations Extensive digital/analog compensation loops for analog cells, with process/temp sensing, calibration routines, etc. Optimized calibration algorithms using a low-power, on-chip spectral estimator. Software-driven analog circuit design that can be conveniently tuned /optimized.
Software-driven correction enables flexibility With respect to waveforms, PA, power consumption (duty-cycle), etc. Allows customization of solutions by application and customer
Semiconductors for Wireless Communications 14
RFPAL Reference PCB
25 mm
Output coupler
RFPAL Linearizer SoC • 9 x 9 x 0.9 mm standard QFN package
Input coupler
Ceramic resonator
RFIN
RFOUT
RFFB
Other: Decoupling + matching networks