Building a PA Design Framework for 5G Applications

Building a PA Design Framework for 5G Applications

© 2020 Cadence Design Systems, Inc. All rights reserved.2

Focus Areas

• Cadence® AWR® Visual System Simulator™ (VSS) software brief introduction

• Amplifier modeling capabilities in VSS software

• Overview of 5G and unique challenges to power amplifier (PA) design

• Phased arrays for 5G systems

• VSS 5G testbenches for PA design and analysis


VSS Software

• Toolset for designing and analyzing from simple RF links to complete RF systems

o Part of Cadence® AWR Design Environment® software

o Powerful RF link design and analysis capabilities

o Modeling and evaluation of complete communications and radar systems

• VSS top-level capabilities:

o RF budget analysis, RF spur heritage

o Time-domain simulations: spectrum, error vector magnitude (EVM), adjacent channel power ratio (ACPR), bit error rate (BER), throughput, etc.

o Phased array design, standard communication libraries

Channel and EnvironmentalRF (Analog)Baseband(Digital)

TX RF Link

RX RF Link

TX Signal

Generation

RX Signal

Processing

Antenna Channel

VSS includes

models for every

component in such

systems!


VSS Software for RF System Simulation

The most complete RF system

simulation functionality in one

integrated tool

RF Budget (RFB)Cascaded gain,input/output IP3,noise figure, etc.

RF Inspector (RFI)Heritage tone inspector to identify the cause of an

inter-modulation product of an RF link

Time DomainEnd-to-end analysis

C/N, BER, ACPR, EVM, etc.

Circuit co-simulationMATLAB/LabVIEW co-sim,Communication standardsWiMAX, WCDMA, LTE, GSM EDGE,

DVB, 802.11a/b/g/n/ac

HW-in-loop simulations

RFB, RFI, and time-domain simulators

use the same RF link design!


BPFBID=F1LOSS=0 dBN=3FP1=900 MHzFP2=1100 MHzAP=0.1 dBNOISE=Auto

AMP_BID=A2GAIN=10 dBP1DB=10 dBmIP3= IP2=

MEASREF= OPSAT= NF=3 dBNOISE=AutoRFIFRQ=

BPFBID=F2LOSS=0 dBN=N1FP1=900 MHzFP2=1100 MHzAP=0.1 dBNOISE=Auto

ISOLATORID=S1LOSS=0 dBISOL=30 dBNOISE=AutoZINP=_Z0 OhmZOUTP=_Z0 Ohm

IN OUT

LO

MIXER_BID=A3MODE=ModeLOMULT=1FCOUT= RFIFRQ={ 100,1200 } MHzGCONV=-6 dBP1DB=10 dBm

IP3=30 dBmLO2OUT=-25 dBIN2OUT=-20 dBLO2IN=-25 dBOUT2IN=-25 dBPLO= PLOUSE=Spur reference onlyPIN=

PINUSE=IN2OUTH OnlyNF=6 dBNOISE=Auto

LPFBID=F3LOSS=0 dBN=4FP=500 MHzNOISE=Auto

TONEID=A4FRQ=1200 MHzPWR=10 dBmPHS=0 DegCTRFRQ=

SMPFRQ= ZS=_Z0 OhmTN=_TAMB DegKNOISE=AutoPNMASK= PNOISE=No phase noise

TPID=Start

TPID=Stop

M_PROBEID=MP1

PORT_SRCP=1ZS=_Z0 OhmSignal=SinusoidSpecType=Use doc freqSpecBW=Specify freq spanSweep=NoneSpan=1000 MHzPwr=-10 dBmAng=0 Deg

PORTP=2Z=_Z0 Ohm

Effect of filter order on NF or gain at

image frequency measurements?

How can I reduce my spur levels?

RFB and RFI

RFB and RFI support:

• Optimization and yield analysis

• Impedance mismatch

• Frequency and temperature dependency

Xo Xn. . .

SWPVARID=SWP1VARNAME="N1"VALUES=swpstp(3,7,1)VALTYPE=ScalarUNITUSE=Project UnitsSWPDUR= SWPCNT=

• Frequency domain circuit solver

• Use RFB to surpass capabilities of common spread sheet and provide greater insight on RF architecture

• Use RFI to identify and mitigate unwanted spurs


Time-Domain System Simulation

• Use the same RF link design as RFB and RFI

• Drive it with modulated signals and perform a wide variety of measurements

QAM_SRCID=A1MOD=16-QAM (Gray)OUTLVL=-10OLVLTYP=Avg. Power (dBm)RATE=2e6

CTRFRQ=1000 MHzPLSTYP=Root Raised CosineALPHA=0.35PLSLN= SMPSYM=_SMPSYM

TPID=DUT_IN

TPID=DUT_OUT

R D

IQ

1 2

3

45

RCVRID=A3

R D

IQ

1 2

3

45

QAM_RXID=A2

TPID=DEM

TPID=REF

DUT

SUBCKTID=S2NET="RF Link"Mode=DIFF

Modulated Signal Test Bench






IN OUT

LO







TPID=Start

TPID=Stop

M_PROBEID=MP1


PORTP=2Z=_Z0 Ohm


Communication Standard Testbenches






IN OUT

LO







TPID=Start

TPID=Stop

M_PROBEID=MP1


PORTP=2Z=_Z0 Ohm


VSS RF Models

• Behavioral ( _B )o Configured via gain, P1dB, IP3, noise figure (NF), etc.

o Amp, mixer, OSC, switch, filters, VGA, VVA…

• File based ( _F )o Use measured data

o AM–to–AM/PM, P2D, S-parameters, MDIF

• Circuit simulation based ( _S )o Extract simulation results from AWR® Microwave Office® software, circuit schematics

o LNA, PA, mixer, OSC, filters

RF blocks account for VSWR effects, frequency and temperature

dependency, support yield analysis, and optimization!


Co-Simulating with Circuit Models

• VSS software offers seamless co-simulation with AWR® Microwave Office®

software, circuit models may be easily included in VSS testbenches


Special Amplifier Models

• Time-delay neural network (TDNN) (file-based):o Trained with measured data: AM to AM/PM and input/output IQ at various power levels

o Can model short- and long-term memory effects

o Created with amplifier model generator wizard


Special Amplifier Models (cont.)

• Load-pull amplifier models in VSS softwareo Simulate load-pull for EVM and ACPR, build contours for various loading conditions


DPD Design in VSS Software

• Various digital predistortion (DPD) algorithms supported in VSS software:

o Theoretical algorithms include lookup table (LUT), memory polynomial, generalized memory polynomial, dynamic deviation reduction second order


5G Overview: Enabling Technologies

• Advanced coding and modulation schemes (part of 5G New Radio [NR] standard)o Improves spectral efficiency

o Requires efficient, linear PAs that can address wider bandwidth and high PAPR

• Use of mmWave spectrumo Provides bandwidth for high data rates

o Requires front-end components (including antennas) that can overcome higher losses at mm-wave frequencies

• Massive multiple-in-multiple-out (MIMO) and beam steering o Enables spatial efficiency, densification

o Requires commercialized phased array antenna systems


* https://www.ericsson.com/research-blog/in-race-to-5g-cp-ofdm-triumphs/

*

5G Radio Access Evolution


5G NR Signal Design

• Frequency band options (RAN4)o LTE re-farming bands: 1, 3, 7, 8, 20, 28, 41, 66, 70, 71

o New sub-6GHz bands: 3.3 – 4.2GHz and 4.4 – 4.9GHz

o mmWave bands: 24.25 – 29.5GHz, 31.8 – 33.4GHz, and 37 – 40GHz

• New modulation featureso CP-OFDM modulation scheme with variable subcarrier spacing (SCS): 3.75 – 480kHz

o Component carrier BW:

– Sub-6GHz: min. 5MHz, max. 100MHz

– > 6GHz: min. 50MHz, max. 400MHz

o Carrier aggregation: max. 16 carriers (RAN1), max. 32 carriers (RAN2)

o Modulation: QPSK, 16QAM, 64QAM, 256QAM, 1024QAM; UL support /2-BPSK


mmWave 5G

• Why cmWave and mmWave?o Large amount of spectrum available

o Support for ultra-fast communications

o Initially used for fixed-wireless/indoor applications

• Increased design challengeso Initial focus on 28GHz and 39GHz bands

o MIMO operation, much larger channel bandwidths, carrier aggregation

o High propagation loss, low signal penetration


Phased Array Design and Analysis in AWR Software

• Phased arrays have become an integral part of mmWave 5G systems

• AWR Design Environment® software offers a full range of tools to facilitate phased array system design

o VSS software used as a top-level integration platform

o Phased array generator wizard for interactive array design

o VSS software for advanced system analysis

o Circuit simulator for extracting active impedance vs array scan angle

o EM simulator for initial element analysis, as well as full array verification


• Phased array generator can be used to interactively design a phased array antenna system

o Configure phased array architecture

o Define RF links, antenna elements, gain tapers

o Monitor 3D array response

o Investigate effect of configuration parameters

o Generate full system, circuit, and/or EM designs

Phased Array Generator Wizard

Monitor 3D array

radiation pattern

Sweep frequency, power,

steering angles, and monitor 3D

radiation pattern

To assist in the design process, simulation of the array radiation pattern is

automatically performed in the background and displayed in 3D

Define array

geometry


Front-End Module Design

• Design and analyze low-noise amplifier (LNA) or PA paths for operation in TX and/or RX mode

o RFB and RFI can be used for RF link analysis and specification definition

o Front-end modules can be analyzed and included in phased array definition

o Full system-level simulations can be used to evaluate the performance of the phased array system when it is driven with modulated signals

SUBCKTID=S2NET="PHASE"PH=0SW_MODE=SW_MODE PORT

P=2Z=_Z0 Ohm

PORTP=1Z=_Z0 Ohm

AMP_B2ID=HMC565_2GAIN=23P1DB=10IP3=20IP2= MEASREF= OSAT=12NF=2.3NOISE=AutoRFIFRQ=

VAR

1

23

RFSW_DIRID=S1ON_POS=SW_MODE+1LOSS=0 dBISOL=30 dBNOISE=Auto

AMP_B2ID=HMC565_1GAIN=23P1DB=10IP3=20IP2= MEASREF= OSAT=12NF=2.3NOISE=AutoRFIFRQ=

AMP_FID=TGA2521DATA="AMP_F_TGA2521_SM"NOISE=AutoRFIFRQ=

To Antenna

To Baseband

1

2 3

SUBCKTID=S3NET="HMC547"SW_MODE=SW_MODE


Initial Element Design and EM Analysis

• Single element design

• 3x3 phased array for calculating effects of 1st and 2nd order mutual coupling


System-Level Models of Phased Array

• The wizard can generate a full system-level model and test bench

o Perform a rigorous analysis in VSS software

o Use the phased array as part of a complete communications or radar system


Phased Array Full Schematic and Layout

• A full schematic and layout can be generated by the wizard

o EM simulator may be used for full array verification

o Circuit simulator may be used for calculation and modeling of active impedances


NR 5G VSS TX Testbenches

• Set up with most common TX measurements, customized according to specification requirements

• Allows users to place their own DUT and start performing measurements in no time


NR 5G VSS RX Testbenches

• Reference sensitivity analysis, according to specification requirements

• Users can add their own DUT and analyze its impact on system performance


mmWave 5G VSS Carrier Aggregation Testbenches

• Up to 8 adjacent component carriers, can be spaced as desired and individually enabled or disabled

• 2x2 MIMO implementation available, receiver can demodulate any or all the component carriers


mmWave 5G Testbench with TX and RX Phased Arrays

• 5G mmWave TX and RX testbenches available in VSS software

o Incorporate baseband signal generation/processing, RF links, phased arrays, and channel propagation

o Phased arrays designed with the phased array generator


Conclusion

• 5G systems introduce new challenges to amplifier design

• Phased array systems will require much more detailed models and simulations

• VSS software offers a wide range of capabilities to support such challenges:o Accurate amplifier models

o Phased array modeling and design capabilities

o Numerous testbenches to kick-start any design

o Powerful framework for system design and analysis!

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Documents

Building a PA Design Framework for 5G Applications