combining fpgas and rf: a new sdr design & test …€“ mixed-signal design challenges ......
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© Agilent Technologies, Inc. 2008
Combining FPGAs and RF: A New SDR Design & Test Methodology
© Agilent Technologies, Inc. 2008 Page 2
A New SDR Design & Test Methodology
Presentation Overview
– Mixed-Signal Design Challenges • System Design Flow Challenges - several teams, disconnected
tools
– Algorithm Level Development• Algorithm Design and Exploration
– Transmitter Design and Circuit Co-Simulation• Mixed-Signal Simulation: HDL - RF Transmitter - RF Circuit Co-
Simulation
– Receiver Design and Mixed-Signal Verification• WiMax BER vs. Receiver LO Phase Noise & ADC Jitter
This presentation will be dealing primarily with the PHY (Physical Layer) of the radio. It will
present new design flow methods that will provide enhanced interaction and verification
between all areas of the SDR development team.
© Agilent Technologies, Inc. 2008 Page 3
A Brief Note About this Presentation• Note: This paper is a continuation of the Agilent SDR webinar
paper entitled “Simulation and Design of SDRs”, which covered the following topics:
• SDR Overview & Challenges
• Comparing RF interference susceptibility of FPGA 16 QAM waveform to a Mobile WiMAX™ COTS waveform
• FPGA Implementation and Test of an OFMDA Mobile WiMAX
Waveform
An archived version of this webinar can be viewed at:http://www.techonline.com/learning/webinar/202403894
Or contact your local Agilent representative for more details
© Agilent Technologies, Inc. 2008 Page 4
Mixed-Signal Challenges: System Design Tradeoffs
Tx RxCoding
Algorithms
D/A
Bits InDecoding
AlgorithmsBits Out
ChannelA/D
GainLinearity
PowerSpurs
GainNF
LinearityPhase Noise
Mixed-Signal Application Examples:
• PAs ( polar loop, DPD)
• Direct conversion receivers and A/D converters
Considerations:
• Sampling Rates and Bitwidth
• Key Algorithms
• RF Gain, Linearity, NF
• Channel Impairments and Interferers
Fixed-Point
Digital Filter
MultipathInterference
BitwidthSample Rate
AGCDynamic Range
Discretization
© Agilent Technologies, Inc. 2008 Page 5
System Design Tradeoffs- Performance BudgetingSystem Design Tradeoffs for EVM & BER/PER
PA
Nonlinearities
RF Upconverter/
Downconverter
Baseband HW
Bitwidth
LOs
(Phase Noise)
Tx RxCoding
Algorithms
D/A
Bits InDecoding
AlgorithmsBits Out
RF ChannelA/D
Channel
Compensation
• With SDR having such
high performance targets every part of
the transmit and
receive chain
becomes critical to the link budget
• So how to decide the
optimum balance?
© Agilent Technologies, Inc. 2008 Page 6
System Design Flow Challenges
...several teams, disconnected tools
RF
An
alo
g
Dig
ital
ConceptCritical algorithms, top-level behavior
ArchitectureHW/SW, digital/RFpartitioning
FunctionBlock behavioral design
ComponentCircuit design, layout
M1 C1 M2
H1(s
)
EN
CO
DE
System Architect
Algorithm Design
Algorithm and Circuit
Implementers
Implementation Handoff
© Agilent Technologies, Inc. 2008 Page 7
Agenda
• Mixed-Signal Design Challenges
• Algorithm Design
• Transmitter Design and Circuit Co-Simulation
• Receiver Design and Mixed-Signal Verification
• Summary
© Agilent Technologies, Inc. 2008 Page 8
Algorithm Design and Exploration- Agilent SystemVue
Production
Partition
Refine
Inte
grat
eVer
ify
SystemVue
AlgorithmDesign
SystemArchitecture
Functional Design
ComponentFirmwareDesign
ComponentVerification
SystemVerification
PrototypeVerification
Wireless Libraries
© Agilent Technologies, Inc. 2008 Page 9
SystemVue Algorithm Exploration • Probe
frequency and time domain characteristics throughout design stages
• Evaluate fixed-point effects
© Agilent Technologies, Inc. 2008 Page 10
HDL Code Generation
© Agilent Technologies, Inc. 2008 Page 11
SystemVue Example- WiMAX™ IQ ModulatorWiMAX IQ
Data from ADS
Wireless Library
HDL Code
Export HDL
with HDS
To ADS for
HDL Co-Simulation“WiMAX,” “Mobile WiMAX” and “WiMAX Forum” are trademarks of the WiMAX Forum®
© Agilent Technologies, Inc. 2008 Page 12
FPGA Implementation
and Test Flow Used
© Agilent Technologies, Inc. 2008 Page 13
Mobile WiMAX FPGA Implementation Test Setup
16900
Logic
Analyzer
with VSA
SW and
ADS
FPGA Board
(DUT)
ESG to
Clock
FPGA
Board
MXA
Signal
Analyzer
with VSA
SW and
ADS
© Agilent Technologies, Inc. 2008 Page 14
Agenda
• Mixed-Signal Design Challenges
• Algorithm Design
• Transmitter Design and Circuit Co-Simulation
• Receiver Design and Mixed-Signal Verification
• Summary
© Agilent Technologies, Inc. 2008 Page 15
RF Design and Verification
Agilent ADS and Wireless Libraries Production
Partition
Refine
Inte
grat
eVer
ify
AlgorithmDesign
SystemArchitecture
Functional Design
ComponentFirmwareDesign
ComponentVerification
SystemVerification
PrototypeVerification
ADSWireless Libraries
© Agilent Technologies, Inc. 2008 Page 16
Agilent ADS for RF Design & Verification
Desig
n
Veri
ficati
on
Simulated and real
world analysis
Simulated and
real world signal
inputs
Implementation
RF/Analog Subsystem
Transistor-levelRF sub-System Designer
RF Circuit Designer
DUT ESG / MXG MXA PSA Infiniium Logic Analyzer
ADS Ptolemy Top Level
© Agilent Technologies, Inc. 2008 Page 17
Multiple Methods to Simulate FPGA Effects along with RF
Transfer captured FPGA signal to ADS
EVM @ Receiver Output is ~ 1.2%
orMATLAB®
Co-Sim
orHDL Co-Sim Analog Devices
AD9433_105
© Agilent Technologies, Inc. 2008 Page 18
Mobile WiMAX Source: Co-Simulate FPGA HDL
Bring FPGA HDL into
ADS to Co-Simulate
FPGA Source EVM 0.74%
Analog Devices
AD9433_105
© Agilent Technologies, Inc. 2008 Page 19
HDL
Co_sim
Numeric
controlled
Oscillator
Circuit Level
Co-Sim
RF Transmitter Co-Simulation
NCO Bit-Width Effects
on Transmit Spectrum
© Agilent Technologies, Inc. 2008 Page 20
Mixed-Signal Simulation: Add RF Circuit to RF
Transmitter and FPGA HDL Co-SimulationCircuit Level
Non-Linear
Co-Simulation
Circuit Envelope
System Level
Co-Simulation
Synthesized
Bandpass Filter
Behavioral
Mixer
Analog Devices
AD9433_105
© Agilent Technologies, Inc. 2008 Page 21
Mixed-Signal Simulation: Circuit Co-Simulation
Note the
Gain
Expansion
and AM to
PM from
the Power
Amp
1x1LOxRF
1x21x0LO
1x-1
1x-21x-3
Just a few of
the close-in
mixer products
are displayed
Decoded
WiMax
Data
© Agilent Technologies, Inc. 2008 Page 22
Mixed-Signal Simulation:
Peak to Average Power Measurements
Preamble Data Transmitter running in the Linear
Region
Running in Saturation
OFDM signals
have a very high Peak to
Average Ratio
© Agilent Technologies, Inc. 2008 Page 23
Agenda
• Mixed-Signal Design Challenges
• Algorithm Design
• Transmitter Design and Circuit Co-Simulation
• Receiver Design and Mixed-Signal Verification
• Summary
© Agilent Technologies, Inc. 2008 Page 24
Receiver Design: WiMAX BER vs. EbNo
Analog to Digital
Converter ModelsPhase Noise vs.
Freq. OffsetSwept EbNo
© Agilent Technologies, Inc. 2008 Page 25
WiMAX BER vs. EbNo vs. Phase Noise (64 QAM)
© Agilent Technologies, Inc. 2008 Page 26
WiMAX BER vs. EbNo vs. Phase Noise (QPSK, 16 QAM, 64 QAM)
64 QAM16 QAMQPSK
© Agilent Technologies, Inc. 2008 Page 27
WiMAX BER vs. EbNo vs. ADC Jitter (64 QAM)
© Agilent Technologies, Inc. 2008 Page 28
WiMAX BER vs. EbNo vs. ADC Jitter (QPSK, 16 QAM, 64 QAM)
64 QAM16 QAMQPSK
© Agilent Technologies, Inc. 2008 Page 29
• Interoperability
– One radio with ability to communicate with everyone.
SDR’s Flexibility
© Agilent Technologies, Inc. 2008 Page 30
Other ADS COTS Wireless Libraries
• CDMA• GSM• DTV• 3GPP WCDMA• CDMA2000
• EDGE• WLAN• CDMA2000 1XEV • TDSDMA• HSPA
http://eesof.tm.agilent.com/products/wireless_libraries.html
• Fixed WiMAX• Mobile WiMAX• 802.11n• WiMedia• 3GPP LTE
Signal SourcesReceivers
Channel Models
Measurements
© Agilent Technologies, Inc. 2008 Page 31
End-to-End System BER:Upconverter, Transmitter, Signal Path, Receiver, ADCs
FPGA Target RF Amplifier
HDL Generated withSystemVue HDS3
Sweep Jitter on
Analog to Digital
Converter Models
© Agilent Technologies, Inc. 2008 Page 32
End-to-End System BER Simulation ResultsUpconverter, Transmitter, Signal Path, Receiver, ADCs
© Agilent Technologies, Inc. 2008 Page 33
A New SDR Design & Test Methodology Summary:
– Mixed-Signal Design Challenges • The various SDR component development teams need to work
together
– Algorithm Level Development• Using Agilent‘s SystemVue as an HDL development tool
– Transmitter Design and Circuit Co-Simulation• Mixed-Signal Simulation: HDL - RF Transmitter - RF Circuit Co-
Simulation
– Receiver Design and Mixed-Signal Verification• Evaluating WiMax BER vs. Receiver LO Phase Noise & ADC
Jitter
© Agilent Technologies, Inc. 2008 Page 34
Additional SDR References
• Archived Webinar “Simulation and Design of Software-Defined Radios” http://www.techonline.com/learning/webinar/202403894
• Agilent EEsof EDA Applications: SDRhttp://eesof.tm.agilent.com/applications/sdr.html
• Agilent SDR Measurements Solutions: http://cp.literature.agilent.com/litweb/pdf/5989-6931EN.pdf
• Connected Solutions Application Notes: http://literature.agilent.com/litweb/pdf/5988-6044EN.pdfhttp://literature.agilent.com/litweb/pdf/5989-0024EN.pdf
Contact your local Agilent representative for more details
© Agilent Technologies, Inc. 2008 Page 35
Thank You !