challenges for power amplifier testing with envelope tracking
DESCRIPTION
September 25th, 2014 Rainer Lenz, Product Manager Signal Generators, R&STRANSCRIPT
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Challenges for Power Amplifier
Testing with Envelope Tracking -
concepts, pit falls, state of the
art and trends
Cambridge Wireless Workshop
Advance Techniques for Radio Transmitters
September 25th, 2014
Rainer Lenz
Product Manager Signal Generators
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2Improving the Efficiency of Your Envelope Tracking Test Setup
Agenda
ı Envelope Tracking – Overview
ı Envelope Tracking - Test Challenges
ı Measurement Setup
ı Summary
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3Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Overview
Low battery. Connect charger.
ı Beside display and processor, a main contributor to the power consumption of a
modern smartphone is the TX power amplifier (PA)
ı Envelope tracking is a technique to improve the efficiency of PAs, thus
increasing battery lifetime
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4Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Overview
ı Modern communication standards, such as LTE, show a high peak-to-average
ratio (PAR), i.e. up to 7 dB for LTE uplink signals
ı PAs are most efficient when operating near its maximum output power
ı For signals with high crest factor, PAs operate in low efficiency regions most of
the time
typical power added efficiency (PAE)
signal amplitude probability
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5Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Overview
DC supply
BasebandUp -
converterI/Q RF
Constant supply voltageEnergy
dissipated
as heat
RF signal
Conventional approach
PA
ı With a constant supply voltage, high amount of
energy is dissipated as heat
PINPOUT
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6Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Overview
DC supply
BasebandUp -
converterI/Q RF
RF signal
DC modulator
Envelope tracking
PA
Modulated supply voltage
Envelope
ı Envelope is calculated from the baseband
signal with (𝐼2 + 𝑄2)
ı DC supply voltage is modulated according to
the envelope of the RF signal
ı As a result the PA is operated in high efficient
regions most of the time
PIN
VCC
POUT
Envelope
detector
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7Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Test Challenges
DC supply
BasebandUp -
converterI/Q RF
Envelope
detectorShaping
Delay
adjustmentDC modulator
PAPIN
VCC
POUT
Signal Generator
Envelope
RF
analysis
Signal Analyzer
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8Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Test Challenges
DC supply
BasebandUp -
converterI/Q RF
Envelope
detectorShaping
Delay
adjustmentDC modulator
PAPIN
VCC
POUT
Signal Generator
Synchronization
ı Synchronization between RF signal and modulated supply voltage VCC
RF
analysisRF
Envelope
Signal Analyzer
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9Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Test Challenges
DC supply
BasebandUp -
converterI/Q RF
Envelope
detectorShaping
Delay
adjustmentDC modulator
PAPIN
VCC
POUT
Signal Generator
RF
analysisRF
Envelope
Signal Analyzer
ı Synchronization between RF signal and modulated supply voltage VCC
ı Apply shaping curve
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10Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Test Challenges
DC supply
BasebandUp -
converterI/Q RF
Envelope
detectorShaping
Delay
adjustmentDC modulator
PAPIN
Voltage
POUT
Signal Generator
𝐏𝐀𝐄 in percentage =RF Power out − RF Power in
DC Power%
RF
analysis
DC power
analysis
RF
Envelope
Signal Analyzer
ı Synchronization between RF signal and modulated supply voltage VCC
ı Apply shaping curve
ı Instantaneous power added efficiency (PAE) calculation
Current
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11Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Test Challenges
DC supply
BasebandUp -
converterI/Q RF
Envelope
detectorShaping
Delay
adjustmentDC modulator
PA
Signal Generator
PIN
VCC
POUT
RF and
distortion
analysis
DC power
analysis
RF
Envelope
Signal Analyzer
ı Synchronization between RF signal and modulated supply voltage VCC
ı Apply shaping curve
ı Instantaneous power added efficiency (PAE) calculation
ı Optional: distortion analysis
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12Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Test Challenges
DC supply
Baseband
and
pre-
distortion
Up -
converterI/Q RF
Envelope
detectorShaping
Delay
adjustmentDC modulator
PA
Signal Generator
ı Synchronization between RF signal and modulated supply voltage VCC
ı Apply shaping curve
ı Instantaneous power added efficiency (PAE) calculation
ı Optional: distortion analysis
ı Optional: predistortion
PIN
VCC
POUT
RF and
distortion
analysisRF
Envelope
Signal Analyzer
DC power
analysis
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13Improving the Efficiency of Your Envelope Tracking Test Setup
Envelope Tracking – Measurement Setup
DC modulator
PIN
VCC
POUT
Signal Generator Signal Analyzer
R&S®SMW200AR&S®FSW
LAN
Generate RF and
envelope signalRF and
Voltage/current
analysis
PA
DUT
RF
Envelope
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14
Signal GenerationAvailable Options
R&S SMW200A
Vector Signal Generator
R&S SMW-K540
R&S SMW-K541
Improving the Efficiency of Your Envelope Tracking Test Setup
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Envelope Tracking - User Interface
15
eTrak
ı Preset configuration for envelope signal
ı Specific DC modulator parameters
like Gain, V CC Offset or Impedance are taken into account
Improving the Efficiency of Your Envelope Tracking Test Setup
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Envelope Settings - Synchronization
ı Envelope to RF synchronization below 1 ns is required
ı Can be adjusted in SMW with ps resolution in real time
RF Envelope
16Improving the Efficiency of Your Envelope Tracking Test Setup
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Different shaping modes
ı Table (Look-Up Table with up to 4000 comma separated value pairs)
ı Polynomial (up to 10 polynomial coefficients)
ı Detroughing (3 different functions)
Real time Shaping capabilities
Envelope
RF
Inv. Env.
Shaping setting Resulting Envelope
17Improving the Efficiency of Your Envelope Tracking Test Setup
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18
Signal Analysis
R&S FSW
Signal- and Spectrum-Analyzer FSW-K18 (Amplifier Measurements)
Improving the Efficiency of Your Envelope Tracking Test Setup
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FSW-K18 PAE measurement (1)
PAE calculation:
DC modulator
PIN
VCC
POUT
Signal Generator Signal Analyzer
R&S®SMW200AR&S®FSW
LAN
Generates RF and
envelope signalRF and
Voltage/current
analysis
PA
DUT
RF
Envelope
ı RF power in -> from SMW
ı RF power out -> measured at RF port from FSW
ı DC power in -> measured at Baseband ports
(2 ports for 2 independent voltages)
DC Power
PAE calculation requires synchronous information of:
Improving the Efficiency of Your Envelope Tracking Test Setup
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FSW-K18 PAE measurement (2)
ı Oscilloscope probes for easy connection
ı Usage of shunt resistor for supply current
measurement
RF Output
(to FSW)
RF Input
(from SMW)
ı PAE graphical display
Improving the Efficiency of Your Envelope Tracking Test Setup
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FSW-K18 Digital Predistortion
21
Measure
AM/AM AM/PM
with FSW-K18
Generate
DPD Tables
Transfer
Tables to
SMW-K541
Activate DPD
on
SMW-K541
Activate DPD
in
SMW-K541
Generate DPD
Tables
(automatically)
Transfer Tables
from FSW-K18
to SMW-K541
Maximum Output
Power of the PA
Improving the Efficiency of Your Envelope Tracking Test Setup
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22
FSW-K18
SMW-K541
Automatic Transfer
and configuration via
LAN
FSW-K18 Digital Predistortion
Interface to SMW-K541
Improving the Efficiency of Your Envelope Tracking Test Setup
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23Improving the Efficiency of Your Envelope Tracking Test Setup
SMW Digital Predistortion implementation
ı DPD applies amplitude and phase offset on every IQ sample in real time
ı DPD alters the signal statistics and the signal level
ı PEP, Level and Crest Factor before and after DPD are shown
ı Adjustable mean Level Reference Mode (Before or After DPD)
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24
Envelope Tracking – Summary and Status
R&S®SMW200A
SMW-K540 Envelope tracking Available
SMW-K541 Digital
Predistortion
Available
R&S®FSW
FSW-B71 Synchronous analog
baseband inputs
Available
i.e. RT-
ZP10
Oscilloscope probe
connection to FSW
Available
FSW-K18 Amplifier Measurements Available
ı RF and envelope signals out of
one box
ı Realtime shaping and delay
adjustment
ı Power sweeps with automatic
recalculation of the envelope signal
ı Realtime Digital predistortion
ı RF and envelope signal analysis
in one box
ı Fastest measurement speed for
EVM/ACLR, Distortion Analysis
and PAE calculation
ı Highest dynamic range,
simplifying the test setup
Improving the Efficiency of Your Envelope Tracking Test Setup
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Thank you
for your attention!
Improving the Efficiency of Your Envelope Tracking Test Setup