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1
ANSYS Solutions for mmWave Antenna- ADAS, 5G, Military
Kihyun Kong, Ph. D.
Sr. Application Engineer
ANSYS Korea
2
Outline
• 안테나설계를위한 HFSS Tips
• Unit Antenna Design
• 좀더정확한해석을위해서 (흡수경계조건)
• Array Synthesis (Estimation to full array)
• 전기적으로큰구조해석을위한 HFSS Solutions
• Adaptive Beamforming
• 제조공정을고려한시뮬레이션
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Challenges of mmWave Antenna Engineering
• mmWave는아직범용화되지않아경험이부족
• 파장이짧아물리적크기가너무작음
‒ 정밀한가공공정이필요로함정확한 modeling & meshing 기반의시뮬레이션이필수
‒ 제작을고려한 Transition 구조에연구필요특히 Signal Via 등에대한고품질 Meshing 필요
• Propagation 손실이커서
‒ 고성능/고효율의안테나가필요
‒ 위상배열안테나뿐만아니라 Diversity 또는 MIMO 안테나시스템에대한고려도필요
• mmWave 이상의대역에서는 Radome Effect도고려해야함
• 안테나를포함하는제품은전기적으로큰구조물
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안테나설계를위한 HFSS Tip #1
Unit Antenna Design
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Array Antenna Design Procedure
Single Antenna Element
TRL Tool in 3D Layout Interfaceor
Antenna Tool Kit (ACT Wizard)
Synthesize Array
Unit Cell
Finite Array
Explicit SimulationWith Feed Network
Port1
Integrated Array with Module
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HFSS Antenna Toolkit
Antenna Toolkit Wizard
• R17부터기본설치에포함
• 약 66가지안테나모델(6가지 Array Model)
• Menu : View > ACT Wizard HFSS Antenna Toolkit 실행
‒ 입력 : Center FrequencyOuter BoundarySubstrate Dimensions
‒ Synthesis Antenna Dimension이자동계산
‒ Finish자동으로변수처리된안테나모델링및결과 Template이생성
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HFSS Antenna Toolkit
안테나모델의 Dimension이모두변수처리되어있으며, 변수에대한정의는Antenna Toolkit Wizard의 Help 그림에서참조할수있음
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Estimation in 3D Layout
Patch Dimension Estimation
‒ Define StackupMenu : Layout > Layers
‒ EstimationMenu : HFSS 3D Layout > Estimate
Layer 정보 (두께, 재질) 입력후Patch Length/Width 및 50ohm Impedance지점을미리계산해볼수있음
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2D MoM Solver in 3D Layout
• 3D Layout : 2D MoM
‒ 4 Element Aperture Coupled Feed Patch Array Example
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안테나설계를위한 HFSS Tip #2
좀더정확한해석을위해서( 흡수경개조건 )
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ABC or PML ?
• HFSS의해석대상바깥영역(Background)은 Perfect Conductor로가정하며대부분의경우 Air(또는 Vacuum) Box를만들고경계면에흡수역할을하는경계조건을설정
• 흡수경계조건의종류
• Radiation Boundary (ABC)
• Perfect Matched Layers (PML)
• FE-BI
• Antenna의경우흡수경계조건의특성을알고사용하는것이정확한해석에도움
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Guide-lines of Radiation BC (ABC)
• Distance from radiating structure
–Place at least /4 from strongly radiating structure
–Place at least /10 from weakly radiating structure
/4 and cases within 13 MHz of each other (0.1%)
0.2 dB variation
Distance Test : λ/20, λ/10, λ/8, λ/4, λ/2, 3 λ/4, λ
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Guide-lines of Perfect Matched Layer(PML)
• Distance from radiating structure
–Place at least /8 from radiating structure (Recommend)
Distance Test : λ/20, λ/10, λ/8, λ/4, λ/2, 3 λ/4, λ
λ /8 and 3 λ /4 cases within 28 MHz of each other (0.3%)
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Incident Angle DependenciesN
orm
al In
cid
en
ceLa
rge
Inci
de
nce
An
gle
ABC PML
Reflection Effect
PML functions well for
incident angles less than
65°-70°
ABC functions well for
incident angles less than
25°-30°
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FE-BI
FEM Solution
in Volume
IE Solution
on Outer Surface
Fields at outer surface
Iterate
FEM Only Solution
FE-BI
IE Region
Surface current on metal block
Hybrid FEM-IE Solution
• FE-BI 바깥영역은 IE Solver가적용되어Reflection이없는이상적조건해석가능
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Single Element Examples
• Dipole Antenna
Ideal Dipole Antenna Gain = 2.15dBi
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Single Element Examples
• Patch Antenna Antenna
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Array Antenna Example
• 8x8 Patch Antenna Antenna
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Analysis Time & Memory
ABC PML FE-BI
Adaptive Pass # 10 11 11
Solved Elements 1,179,410 1,151,860 1,233,570
Adaptive Time 01:19:59 01:33:04 09:33:02
Used Memory 48.2GB 51.3GB 27.3GB
• Elapsed Time Comparison
ABC PML FE-BI
Adaptive Pass # 9 9 8
Solved Elements 21,554 17,338 15,355
Adaptive Time 00:01:09 00:00:42 00:01:09
Used Memory 765MB 654MB 366MB
< Single Patch Antenna Case >
< 8x8 Array Antenna Case >
Used H/W : 2.7GHz CPU with 8cores, 64GB RAM
ABC PML FE-BI
Adaptive Pass # 11 11 11
Solved Elements 260,787 269,511 213,308
Adaptive Time 00:12:18 00:13:46 00:23:47
Used Memory 8.2GB 51.3GB 4.0GB
< 2x8 Array Antenna Case >
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흡수경계조건사용 Guide
• 지향성단일안테나의경우는 Radiation BC로도무난함.
• Omni-Directional 또는 Array 안테나해석에 PML 또는 FE-BI 사용을권장
✓ 단, FE-BI의경우 R18.x부터모든 HFSS User가사용가능하지만, Domain Decomposition 사용이필수이므로 HPC가있어야만동작됨
• FE-BI에대한이해
✓ 전기적으로큰문제를해결하기위해 FEM과 IE를 Hybrid로사용하는방식이어서Domain Decomposition을사용함.
✓ 빠른해석을위한목적보다는한대의 H/W로해결하기어려운문제를여러대의PC로분산처리하는목적
✓ Large Array와같이 Port가많아질경우 Mesh를분할하고다시재조합하는시간이추가되어해석시간이길어질수있음.
✓ 그러나 PML에비해상대적으로 RAM 사용량이줄어들어효율적임.
✓ Port가적을경우전기적으로큰구조를적은 resource로빠르게해석가능.
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안테나설계를위한 HFSS Tip #3
Array Synthesis
(Estimation to full array)
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Array Performance Estimation with Single Element
< 간략한 Array 효과분석 >
• Single Antenna(Unit Cell)의결과만으로 Array를구성하여결과예상
Mutual coupling Effect가반영되지않아정확한예측은어려움
간단하고빠르게초기 Array 구성설계를할수있음
- Array 개수, 배열간격, 배열모양등
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Finite Array for Large Scale Array
< 정확하고빠른 Array 효과분석 >
• 해석된 Single Antenna의Mesh를복사하여 Array를정확하면서빠르게해석전체mesh를계산하므로Mutual coupling Effect가반영됨다양한 Array 구성이가능하며, 각 Port 조건도 Post-Processing으로조정가능
• Large Array인경우Memory Resource및해석시간단축가능
• HPC의 Domain Decomposition Method(FA-DDM) 기능으로병렬연산
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Finite Array – Domain Decomposition Method
• Port 수가많은 large array에서 DDM 기법을사용하여병렬처리로효율적으로해석
• 한네트워크에연결된여러대의Workstation들을사용할경우 H/W resource 조건을고려하여자동으로최적화하여분산처리
Array의각 Element들을 solution domain으로처리
각 element의 Mesh를 Core별로분산시켜병렬해석
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Estimation / Finite Array / Explicit Array
RAM : 115MBAdaptive : 53sec
Finite Array Explicit ArraySingle (Master/Slave)
RAM : 1.28GBAdaptive : 1m54sec
RAM : 9.61GBAdaptive : 13m46sec
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전기적으로큰구조해석을위한 HFSS solutions
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ANSYS Electromagnetic Solver Portfolio
Hybrid Solver and Domain Decomposition
Geometry and Material Complexity
Ele
ctri
cal
Siz
e
HFSS - Finite Elements
HFSS IE - Method of Moments
SBR+ - Asymptotic, Shooting Bouncing Ray
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HFSS의 Hybrid Solver
Hybrid Solver
Finite Element – Boundary Integral
+
IE / PO / SBR+
HPCDomain Decomposition
26 GHz RAM Elapsed Time
PML 259G (DDM) 840min
FE-BI 64G 205min
FE-BI: 4.1x speedup factor and 75% less RAM
• HFSS R18(2017)부터별도 HFSS-IE license 없이Hybrid Solver(FE-BI, IE Region) 사용가능
• R18부터 SBR+ Region 추가
• PO Region 및 SBR+ Region을사용하기위해서는 HFSS-SBR+ option license 필요
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Hybrid Solver Example
PCB : IE Region
Antenna : FE-BI
Cover : FE-BI
Side View
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Hybrid Solver Example
Cover X Cover O
Radome Effect : 28GHz Array Antenna on Mobile Handset
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Hybrid Solver with Mesh Reuse
Cover 높이변수 DeltaZ
DeltaZ Adaptive Time
Initial Mesh
Last Mesh
0mm 00:25:55 12,950 32,238
0.2mm 00:05:32 32,238 32,238
0.4mm 00:06:11 32,238 32,238
Mesh를재사용하여해석시간단축
< DeltaZ Parameter Sweep >
Hybrid Solver를이용하여 Mesh를재사용한빠른 Parametric Sweep 가능
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Installation with Radome in E-Large Scale
Automotive Radar
Far field Pattern
In FREE SPACE
Far field Pattern
INSTALLED in Facia
Installation Analysis with SBR+
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Adaptive Beamforming
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Beamforming in Phased Array Antenna
Phased Array
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Phased Array Antenna System
MIMIC in HFSS 3D Layout
3D System with HFSS
Non-Linear Circuit with RF Option
Push-Excitations
Dynamic Link
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End-to-End System Example
SBR+ solver
FEM solver
Hybrid solver
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Adaptive Beamforming
Savant(SBR+ solver) & Python Script
Phased array tracking beacon antenna
PEC plates transitions across line of sight between array and beacon antenna
Line of Sight No Line of Sight
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< Post-Processing Variables >
• HFSS에서 Post-processing 값에도변수정의가가능하며,
변수조건에따른재해석이필요없이결과를확인할수있습니다.
Parametric Sweep, Optimization 활용시빠른시간에확인가능
Port 조건에따른 Far-field 및 Active S-parameter의실시간 Tuning 활용
Beam Forming Optimization
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Beam Forming Optimization
< Real Time Tuning >
Gain Pattern
Active S-parameter
Tuning Slide Bar
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Beam Forming Optimization
< Far-Field Pattern Optimization>
Theta=20deg일때Beam Peak 조건최적화
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Beamforming Area Consideration
Far-field Report with Sine Space
-1 < U=sin(θ)cos(φ) < 1-1 < V=sin(θ)sin(φ) < 1
구좌표계를 Normalize 된UV 평면으로표현
Phased Array의 Port 조건에따른 far-field pattern을 sine space로 export Port 조건에대한경우가많으므로 Script로자동화
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Sine Space Example
1x4 Array
Case #2
Conditions Case #1 Case #2
Total # of cell 31,417 31,417
Target # of cell 7,129 4,496
Coverage Area 22.69% 14.31%
< Gain 6dB 이상영역계산 >
Case #1
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제조공정을고려한시뮬레이션
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Coating & Plate Analysis
도금층또는 Radome의 coating layer를반영하고해석이필요한경우
3D 모델링대신 Layered Impedance 경계조건으로쉽게해석가능
< Layered Impedance Surface >< 3D Model >
45
Warpage Problems
• 공정상발생한열또는 Chip 소자에의한발열현상으로 PCB 변형이발생하고이에따른Antenna 영향도분석
• Thermal/Stress/Electromagnetics가복합된 Multi-Physics 문제
• ANSYS Mechanical을통해서열응력해석이가능
< 열응력해석에필요사항 >• 온도분포• 구속조건• 재질의열팽창계수(CTE) 또는탄성계수
< 열응력해석 Output>• Temperature distribution• Stress distribution• Deformation
Two-way coupled
EM Fields(HFSS)
Thermal(ANSYS Mechanical or Icepak)
Stress(ANSYS Mechanical)
Two-way coupled
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Simple Warpage Condition Analysis
1x4 Array @ 28GHz
Warpage Center Freq.HPBWphi=0
HPBWPhi-90
20um 27.34(Ref.) Ref. Ref.
40um 27.3(-0.15%) 0.03% 0.46%
60um 27.32(-0.07%) 0.43% 0.51%
80um 27.31(-0.11%) 0.42% 0.43%
100um 27.22(-0.07%) 0.24% 0.25%
