System-Level Time-Domain Behavioral Modeling for a Mobile ...
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System-Level Time-Domain Behavioral Modeling for
a Mobile WiMax Transceiver
2006. 9. 15
Brian Y. Kim, Ph. D.
Telecomm. R&D Centre
Samsung Electronics
System-Level Time-Domain Behavioral Modeling for
a Mobile WiMax Transceiver
2006. 9. 15
Brian Y. Kim, Ph. D.
Telecomm. R&D Centre
Samsung Electronics
© SAMSUNG Electronics Co., Ltd. 2/19
• Background• RF Time-domain Behavioral Modeling• Modeling Methods• Simulation Results• Conclusion
AgendaAgenda
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Industry Trend - Highly Integrated SoC/SiPRF Ckt, ADC/DAC & Digital baseband
Design MethodologyTop-down vs. Bottom-upTop-down methodology becomes necessary for SoC/SiP
Simulation & Verification System-level vs. Transistor-levelSystem-level simulation & verification play a key role in Top-down methodology
Background
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Time-domain vs. Frequency-domain System-level Specification <-> Time-domain
Constellation, EVM, BER, FER,…
RF Performance <-> Frequency-domainNonlinearity, Noise Figure, Phase noise, …
System-level simulationFull signal path and time-consuming simulationTime-domain behavioral models are required Frequency-domain model -> Time-domain mode
Application ExampleMobile WiMax IEEE 802.16e (WiBro) in Simulink
Background
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RF TimeRF Time--domain Behavioral Modelingdomain Behavioral Modeling
Passband vs. Baseband Real signal processing -> passband modelComplex signal processing -> baseband equivalent model
( ) ( ) cos( ) ( )sin( )1 {[ ( ) ( )] [ ( ) ( )] } 2
c c
c c
j t j t
rf t I t t Q t t
I t jQ t e I t jQ t eω ω
ω ω−
= +
= + + − 2
{[ ( ) ( )] [ ( ) ( )] }
[ ( ) ( )] [ ( ) ( )]
c c c
c
j t j t j t
j t
I t jQ t e I t jQ t e e
I t jQ t I t jQ t e
ω ω ω
ω
−+ + − ×
= + + −
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RF TimeRF Time--domain Behavioral Modelingdomain Behavioral Modeling
Nonlinearity Polynomial memoryless modelPassband expression
x(t) is the passband signal, and able to expressed as x(t) = C(t)e-jωct + C*(t)ejωct,
C(t) is the complex baseband equivalent signal.
Baseband equivalent expression
the polynomial coefficients changed in baseband model
2 3 51 2 3 5( ) ( ) ( ) ( ) ( )y t k x t k x t k x t k x t= + + +
2 41 3 5
3 5( ) [ ( ) ( ) ] ( )4 8BBy t k k C t k C t C t= + + ⋅
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RF TimeRF Time--domain Behavioral Modelingdomain Behavioral Modeling
NoiseNoise figure (NF) – Frequency-domainRMS noise power (Pn) – Time-domain
Where k is the Boltzmann constant, T is the noise temperature,
R is the source impedance and fs is the sampling frequency.
Other Noise sourceFlicker noisePhase noiseQuantization noise
2 /104 (10 1)NFn n sP kRT fσ= = ⋅ ⋅ +
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Modeling Methods
AmplifierLNA
Polynomial nonlinearity model with hard saturationNoise model
Power AmplifierPolynomial nonlinearity model with hard saturationPhase distortion model by AM-PM conversion
3 51 3 5
3 54 8
+ +k x k x k x3 5
1 3 53 54 8
+ +k x k x k x
LNA PA
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Modeling Methods
Amplifier Model Verification
LNA PA
More Nonlinearity is in PA
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Modeling Methods
MixerSame nonlinearity and noise model as LNANonlinearity
Equivalent to the RF input
Noise Equivalent to the output port
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Modeling Methods
LOPhase noise
1/f3, 1/f2, and Noise floorNoise floor is modeled as AWGN1/f2 is modeled as AWGN with transfer function
1/f3 is modeled as AWGN with transfer function
PLL loop Second -order high pass filter
21/ 11( )
1fH zz−=
−
31/ 1 3/ 21( )
(1 )fH zz−=
−31/ 1 2
0 1 2
1( )...fH z
a a z a z− −=+ + +
IIR
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Modeling Methods
LO Model VerificationPhase noise: -50dBc/Hz @10kHz, -80dBc/Hz @100kHz ,&
-120 dBc/Hz @Noise Floor.Loop bandwidth: 100kHz
PLL Disabled PLL Enabled
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Modeling Methods
ADC/DACNonlinearity:
INL and DNL: Modeled as non-uniform quantization levelDNL is generated by Gaussian random noise INL is the integration of DNL
, ,1
k
INL k DNL ii
v v=
=∑ , , 2q k INL k ref offsetnkv v v v= + +
Non-uniform Quantization level
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System Simulation in MATLAB SimulinkSystem-level Diagram
Simulation Results
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Simulation Results
Mobile WiMax Signal SourceSignal Source generation by m-codingDownlink modulation :
64QAM/ 16QAM/ QPSKUplink modulation : 16QAM/ QPSKCell ID : 2Segment number : 0DL/ UL ratio : 27/15 symbols
Modulation Scrambling RearrangementPilot Insertion
IFFTCyclic Prefix InsertionRF Input
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System Performance Constellation and Spectrum for 16QAM
Simulation Results
A B C
ACPR SNR for 1e-6 BER
Signal source TX RX
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Simulation Results
80dB55dB
45dB
35dB
TxSource
Rx
Constellation and Spectrum for 64 QAM
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Simulation Results
System Performance for Various Cases
Simulation EfficiencyThe whole simulation for one frame OFDM signals takes about 4 minutes
on a Pentium 4 3.0GHz PC with 1GB memory.
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Conclusion
Behavioral Mobile WiMax Transceiver design has been implemented on Matlab/Simulink platform.
Overall Functionality and block specification could be validated based on 802.11e standard.
The impact of nonlinearity and noise from RF/Mixed-signal building blocks is addressed by the time-domain system simulation.
The proposed baseband equivalent model technique is able to be applied by wide range of the system-level simulation covering RF nonlinearity and noise effects
© SAMSUNG Electronics Co., Ltd.