ANSYS Simulation Advances for RF Microwave Antenna Applications

© 2011 ANSYS, Inc. October 24, 20111

Simulation Advances for RF, Microwave and Antenna Applications

Presented by Martin Vogel, PhDApplication Engineer


• Advanced Integrated Solver Technologies– Finite Arrays with Domain Decomposition– Hybrid solving: FEBI, IE Regions

• Physical Optics Solver in HFSS‐IE• Improved Multi‐Physics flow in Workbench

Overview


Advanced Solvers:Finite Arrays with DDM


Finite Arrays with Domain DecompositionEfficient solution for repeating geometries (array) with domain decomposition technique (DDM)


A Review: Domain Decomposition

Distributes mesh domains to network of processors

Significantly increases simulation capacity

Highly scalable to large numbers of processors

Automatic generation of domains by mesh partitioning

• User friendly• Load balance

Distributes mesh sub-domainsto networked processors and memory


Finite Antenna ArraysDefine unit cell and array

dimensions

Efficient Domain Decomposition solution

• Leverages repeating nature of array geometries

• Only mesh unit cell• Virtually repeat mesh throughout array

Post‐process full S‐parameter• Couplings included• Edge effects included

3D field visualization

Far field patterns for full array

Memory efficient Enabled with the HFSS HPC

product


Finite Arrays by Domain Decomposition• Each element in array treated as solution domain

• One compute engine can solve multiple elements/domains in series

Distributes element sub-domainsto networked processors and memory


Example: Skewed Waveguide Array

• 16X16 (256 elements and excitations)

• Skewed Rectangular Waveguide (WR90) Array– 1.3M Matrix Size

• Using 8 cores– 3 hrs. solution time– 0.4GB Memory total

• Using 16 cores– 2 hrs. solution time– 0.8GB Memory total

• Additional Cores– Faster solution time– More memory.

Unit cell shown with wireframe view of virtual array


Skewed Waveguide Array

• Patterns from 8X8 Array– Dashed is

idealized infinite array analysis

– Solid from finite array analysis

• Two simulations use identical mesh

• Note edge effects due to finite array size


Running Finite Array

Use Master/Slave unit cell design to adapt the mesh

• Called “Unit Cell for Adaptive Meshing” in image

Copy/Paste Design• Called “8X8 Array” in image

Create a single pass setup in finite array design

On “Advanced” tab use “Setup Link” to link mesh from unit cell design

Doing adaptive meshing in finite array design will be time consuming and not as efficient


Efficient: 8X8 Array Patch Array

Direct solver with 12 cores• 5:05:14• 60.8 GB RAM

Finite Array DDM with 12 cores

• 00:44:53• 1.8 GB

6.8X faster33.8X less memory


HPC: Faster with additional coresLinux cluster• 16X Dell PowerEdge R610

– Dual six‐core Xeon X5760, 8GB per core

Same 8X8 array of probe feed patch antennas

3M+ matrix size, 64 excitations

Study performed using 101, 51 ,26, 11, 6 and 3 engines.*• 101 simulation time = 17 min., 20X faster than direct solver• *Three engines used as baseline

1

2

3

4

5

6

7

0 50 100 150

speed factor

speed factor

Number of cores


Hybrid Solving: Finite Element‐Boundary Integral


• Antenna Placement Study: UHF Antenna on Apache UH64 airframe– Finite Elements with DDM– Boundary Integral (3D Method of Moments)– Hybrid Finite Element‐Boundary Integral (FE‐BI)

Finite Element‐Boundary IntegralSolving Larger Problems with Rigor


Hybrid Solving: Finite Element‐ Boundary Integral

Apache helicopter• UHF antenna placement study @ 900 MHz

Solution volume• 1,250 m3

• 33,750 λ3

Solution Specs• 72 engines• Matrix size = 47M• 6 adaptive passes• 300 GB RAM• 5 hr 30 min

Finite Elements with DDM




Solution surface• 173 m2

• 1557 λ2

Solution Specs• 12 core MP• 680k unknowns• 9 adaptive passes• 83 GB RAM• 5 hr 28 min

Boundary Integral, 3D MoM with HFSS‐IE




FEM solution volume• 69 m3

• 1863 λ3

IE solution surface• 236 m2

• 2124 λ2

Solution Specs• 12 cores total using DDM with MP

• Matrix Size = 2.9M• 6 adaptive passes• 21 GB RAM• 1 hr 3 min

Hybrid Finite Element – Boundary Integral

Compared to 72 core FEM solution 14X less memory, 5.5 times faster


Summary of FEBI performance

Type Time, Ratio Memory, Ratio

FEM + DDM 5hr 30min, 1 300GB, 1

IE 5hr 28min, 1 83GB, 3.6

FEBI 1hr 3min, 5.5 21 GB, 14.3


FE‐BI and Distributed Solving

HPC distributes mesh sub-domains, FEM and IE domains,to networked processors and memory

FEM Domain 1

FEM Domain 2

FEM Domain 3

FEM Domain 4

IE Domain

• Distributes mesh sub‐domains to network of processors• FEM volume can be sub‐divided into multiple domains

• IE Domain is distributed to second node in machine list

• Significantly increases simulation capacity

• Multi‐processor nodes can be utilized


Hybrid Solving: IE Regions


FEBI and Physically Separate “Domains”Reflector with multiple FE‐BI domains• Conducting reflector and feed horn each surrounded by air with FEBI applied to surface of air volumes

• But 3D MoM solution from integral equations could be applied directly to reflector’s conducting surface only


HFSS Hybrid Solving – IE Regions

• Parallelized– IE regions

solved in parallel.

– Analogous to FEM domains

• Rigorous– Multiple

reflections

• Automated


HFSS IE Regions ‐ Example


Physical Optics


HFSS‐IE POAsymptotic solver for very large

geometries• In HFSS‐IE• Currents are approximated in illuminated regions– Set to zero in shadow regions

• No ray tracing or multiple “bounces”

Target applications:• Large reflector antennas• RCS of large objects such as satellites

Option in solution setup for HFSS‐IESourced by incident wave excitations• Plane waves or linked HFSS designs as a source


Physical Optics Solver in HFSS-IE

• For illuminated surfaces Jsurf ≈2(n x Hinc ) if perfect conductor.

• For non-illuminated surfaces Jsurf ≈ 0.

• No need to solve a large matrix equation.

Where: JPO = 2(n x Hinc )

PEC


PO Examples

Notice the shadowing of the gun barrel on the tank and of the tank on the ground.


HFSS‐IE PO ‐ Example

Offset reflector 50 λ0 in diameter fed by a horn HFSS far field link

Simulated with 8 coresIE: 48.3min and 11.9GBPO: 23S and 286MBNote > 120x speedup


ANSYS Workbench• Geometry and material transfer


Ansoft to ANSYS Geometry Transfer

• Geometry and material assignment transfer from electromagnetic tools to ANSYS Thermal and Mechanical

CAD tool


Highlights• New technique for finite phased‐array antennas• IE Regions• Physical Optics Solver in HFSS‐IE

• Improved Multiphysics flow

ANSYS Simulation Advances for RF Microwave Antenna Applications

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