HFSS: Optimal Phased Array Modeling Using - · PDF file15. 0 Release Authors: Dane Thompson...
Transcript of HFSS: Optimal Phased Array Modeling Using - · PDF file15. 0 Release Authors: Dane Thompson...
15. 0 Release
Authors: Dane Thompson Nick Hirth Irina Gordion Sara Louie
HFSS: Optimal Phased Array Modeling Using Domain Decomposition
Presenter: Dane Thompson
February 23, 2009 Inventory #002593
© 2012 ANSYS, Inc. HFSS 15.0 2 November 14, 2012
Motivation
Electronically scannable antenna arrays often contain semi-arbitrary element layouts with hundreds or thousands of elements. HFSS V15 includes new enhancements to enable easy creation and accurate/fast simulation of such finite arrays.
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Overview
Finite Array DDM (FA-DDM) w/FEBI
New in v15
Goal: To demonstrate the superior accuracy, flexibility, and speed of finite antenna array modeling in HFSS V15.
Array Mask with Padding Cells
New in v15
MPI New in v15
Composite excitations v15
MagVector PhaseVector
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Outline
Part I: Finite Array Domain Decomposition Overview
Part II: Accuracy
Part III: Flexibility
Part IV: Speed/Capacity
Conclusion
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Part I: Finite Array Domain Decomposition Overview
Part I: Finite Array Domain Decomposition Overview
Part II: Accuracy
Part III: Flexibility
Part IV: Speed/Capacity
Conclusion
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• Utilizes Replicated DDM Unit Cell to Address Array Concerns • Geometry and Mesh copied directly from Unit Cell Model
• Unit Cell geometry expanded to finite array through a simple GUI • Adaptive Meshing Process imported from Unit Cell Simulation
– Dramatically reduces the meshing time associated with finite array analyses. – Mesh periodicity reinforces array’s periodicity.
Finite Array Domain Decomposition
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• Advantages of the new finite array tool in V14 of HFSS:
1. Solves much BIGGER arrays on the
same hardware
2. Obtains ACCURATE results that match HFSS explicit simulations
3. Enables EFFICIENT simulation of large finite arrays utilizing domain decomposition (DDM)
4. Makes it EASY to transform a master/slave unit cell into a finite array
Finite Array DDM Tool Advantages
256 element Vivaldi with metal thickness
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Part II: Accuracy
Part I: Finite Array Domain Decomposition Overview
Part II: Accuracy
Part III: Flexibility
Part IV: Speed/Capacity
Conclusion
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Accuracy
Radiation Boundary vs FEBI Primer FA-DDM Boundary Details Far-field Pattern Accuracy Comparisons
Goal: Demonstrate the pattern accuracy of finite array domain decomposition (DDM) Enabling feature: FEBI absorbing boundary with FA-DDM New V15
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Radiation Boundary: Incidence Angle Dependency
Radiation boundary functions well for incident angles less than 25°-30°
Radiation Boundary
Radiation Boundary
Poor absorption of radiation boundary affects radiation pattern
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PML Incidence Angle Dependency
PML functions well for incident angles less
than 65°-70° Better absorption leads to better consistency in the patterns
PML
PML
Blue Trace is with thicker PML
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FEBI Incident Angle Dependency FEBI Hybridization FEBI Hybridization
Pattern Results are Insensitive to
Incidence Angle
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FA-DDM Side Absorbing Boundaries with PML (V14 Setup)
Vacuum buffer region mimics FA-DDM
Radiation boundary on sides
PML
Radiation Boundary on HFSSv14 Side Walls Can Affect Pattern Results
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FA-DDM Side Absorbing Boundaries with FEBI V15
FEBI radiation boundary FEBI radiation boundary
surrounding the array on five sides
Improved Accuracy Through FEBI Enhancements • IE Solution Can to Touch the Array’s Ground Plane • No longer need Radiation Boundary on the Side Walls
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FA-DDM Boundary Setup
PerfE or finite cond. w/Inf Gnd option checked
FEBI radiation boundary
Infinite ground plane everywhere
FEBI radiation boundary surrounding the array on five sides
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Accuracy Comparison
Uniform 3x3 vivaldi array Test Cases:
1. Explicit with PML 2. Explicit with FEBI 3. FA-DDM with PML 4. FA-DDM with FEBI
All radiation surfaces are
seeded at Lambda/6 for highest pattern accuracy
Surrounding air cells are
not visualized with the FA-DDM display, but they are present for the solver
1 2
3 4
V14 suggested setup for FA-DDM
V15 improved accuracy for FA-DDM
PML Explicit
FEBI Explicit
FA-DDM w/PML
FA-DDM w/FEBI
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3x3 Vivaldi Array
Boresight
SideLobe
Horizon
The three setups expected to be the most accurate agree very well. Let’s zoom in to see more detail.
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3x3 Vivaldi Array Boresight Accuracy
0.01 dB
Boresight gain is within 0.01dB for the three setups expected to be most accurate, including the FA-DDM w/FEBI solution in HFSS V15.
0.028 dB Most accurate setups
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3x3 Vivaldi Array Sidelobe Accuracy
0.05 dB
Sidelobe gain is within 0.05dB for the three setups expected to be most accurate, including the FA-DDM w/FEBI solution in HFSS V15.
0.67 dB
Most accurate setups
FA-DDM setup available in HFSS V14
FA-DDM setup available in HFSS V15
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3x3 Vivaldi Array Horizon Accuracy
FA-DDM setup available in HFSS V15
0.12 dB
Most accurate setups
0.79 dB
FA-DDM setup available in HFSS V14
Horizon gain is within 0.12dB for the three setups expected to be most accurate, including the FA-DDM w/FEBI solution in HFSS V15.
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Accuracy Example #2 - FA-DDM vs. Explicit array
• 547 element hexagonal array composed of circular waveguide elements
– Both arrays with Lambda/6 seeding operation on radiation surfaces
Solid: FA-DDM Circles: Explicit Solid: FA-DDM
Circles: Explicit
The explicitly solved array and FA-DDM solved array patterns are in agreement over a dynamic range of ~60dB.
Phi = 0deg Cut Plane Phi = 90deg Cut Plane
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Part III: Flexibility
Part I: Finite Array Domain Decomposition Overview
Part II: Accuracy
Part III: Flexibility
Part IV: Speed/Capacity
Conclusion
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Flexibility
Goal: Enable quick/easy generation of shaped or sparse finite arrays. Enabling feature: Array mask with padding cells New V15
Array Masks Shaped/Sparse Arrays HFSS Toolkits for Arbitrary Array Generation
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Array Mask in HFSS V14 vs HFSS V15
HFSS V14 Uniform cartesian grid Active or Passive
HFSS V15 Padding cells enable
array shaping
Note the small changes in the selection dialogue
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Array Mask Cell Types
• Each “element” in the array mask can be set to one of the three following types:
New in V15
1. ACTIVE (blue cells): Element is present and has ports. 2. PASSIVE (white cells): Element is present and is terminated in a matched load (no ports). 3. PADDING (gray cells): No element present. Options: a) Air only b) Air with infinite ground
Active elements
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Array Mask Setup
'A' vector direction
'B' vector direction
The array element distribution is dependent on the master/slave A and B vector directions.
The array mask 'A' vector direction is down.
1
2
The array mask 'B' vector direction is to the right.
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Array Mask Setup (cont.)
M1
S1
M2 S2
The master/slave pairs should be along the X and Y axes as shown to create an array that visually maps to the array mask.
Default top-down view.
'A' vector (red-solid) 'B' vector (blue-dotted)
3
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Flexibility – Shaped Arrays Diamond Circular Oval
Square/Rectangular Hexagonal Triangular/Trapezoidal
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Flexibility – Sparse Arrays Randomized Hex Asymmetric Spiral/Hex Small Spiral
Thinned Snowflake Hex Panels
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HFSS Toolkits New in V15
• Iron Python programmable “Toolkits” are now available in HFSS V15
• Toolkits enable users to create custom GUIs inside of HFSS with “wizard” like functionality
Navigation to Toolkits is under HFSS > Toolkit
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HFSS Toolkit for Array Shape Generation
The Array Toolkit makes array shape generation easy!
In this example Toolkit, the following arrays may be generated:
Hexagonal Hexagonal Random Snowflake
Also included in the toolkit is the ability to import an array mask from a .csv file
1
2
3
However, the toolkit is modifiable by the user to generate ANY array type desired!
0 = Active 1 = Passive 2 = Padding
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Part IV: Speed/Capacity
Part I: Finite Array Domain Decomposition Overview
Part II: Accuracy
Part III: Flexibility
Part IV: Speed/Capacity
Conclusion
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Speed
Goal: Simulate large arrays faster and larger than ever before! Enabling features: 1) MPI data transfer New V15
2) Composite Excitations New V15
Composite Excitations Message Passing Interface (MPI)
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What is it? A new solution type in HFSS.
Composite Excitations
Traditional Iterative*:
Composite:
What are the benefits? – Solve a subset of the scan volume MUCH more quickly than running all
excitations in the array independently (but have to run again for each Edit Sources state change)
How does it work? Solves a high port count iterative solver problem (such as FA-DDM) with a defined
magnitude/phase excitation vector that can be treated as a single excitation.
MagPort1: 1 AllOthers: 0
MagPort2: 1 AllOthers: 0
MagPortN: 1 AllOthers: 0
MagVector = [1 2 3 5 3 2 1] PhaseVector = [0 0 0 0 0 0 0]
Solve
Solve
Solve
Solve
*Multi-port iterative solves are multi-threaded with HPC. Only N simultaneous ports can be solved with N cores.
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Composite Excitations Solve Time for Varying Array Sizes
Sim
ulat
ion
Tim
e [m
inut
es]
Number of Antenna Elements
Array Size
Full Array FA-DDM
Composite Excitations FA-DDM
Speedup
3x3 1:10 0:08* 9x* 4x4 1:28 0:09* 10x* 8x8 6:51 0:27* 15x* 12x12 28:39 0:42* 41x* 16x16 - 0:53* - 20x20 - 1:14* -
Solve Time [hh:mm]
*Provides active s-parameters and pattern data at one scan angle
0
500
1000
1500
2000
0 200 400
Full Array Composite …
Vivaldi element. Relaxed settings. Radiation boundary w/Lambda/6 seeding.
As port counts rise into the hundreds, simulation time slows. Composite excitations allows quick extraction of one custom excitation vector to observe active s-parameters, and near-field/far-field results.
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1. Diamond tapered vivaldi array 2. Asymmetric hex spiral array 3. Small spiral array 4. Snowflake array 5. Large hex array
Composite Excitations Examples
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Diamond Tapered Vivaldi Array
Tapered Vivaldi array
15 x 16 array mask 240 total cells 128 active cells 512 excitations Boresight angle
2hr3 min 148GB distributed RAM
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Asymmetric Hex Spiral Array Spiral shaped 27X27 array (13 rings)
– 2 HPC Packs – FA-DDM Composite Excitations
• RAM: 11.4GB • Time: 8 minutes
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Small Spiral Array Spiral shaped 9X9 array, 25 ports, 50 modes
– 1HPC Pack – FA-DDM Full Array Analysis
• RAM: 1.4GB • Time: 18 minutes
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Spiral shaped 9X9 array, 25 ports, 50 modes – Control of Sidelobe Level: Tapered feed
A post-processing variable is used to sweep the magnitude taper of the array and to animate the pattern result in real time.
Small Spiral Array
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Spiral shaped 9X9 array, 25 ports, 50 modes – Control of Sidebobe Level: Tapered feed
Plot the tradeoff between beamwidth and sidelobe levels
Small Spiral Array
Plain lines = tapered magnitudes Symbol lines = uniform magnitudes
Phi = 0, Phi = 90
Tapering the magnitudes yields minimal sidelobes, but a wider beamwidth and lower gain.
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Snowflake Array Snowflake shaped array, 529 circular WG elements, 1058 modes
– 2 HPC Packs – FA-DDM Composite Excitations
• RAM: 62 GB (distributed) • Time: 27 minutes
The goals of this sparse array are to: 1) Reduce side lobe levels 2) Reduce element count for the
same electrical aperture (cost)
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Snowflake Array Snowflake shaped array, composite excitations
Sidelobes >22dB below peak
Active S-parameters are available for the given excitation vector.
22.3dB
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Snowflake Array - Animated E-field
E-field 5mm above aperture Circularly polarized elements
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Large Hex Array
Circular waveguide element, hexagonal arrays
18 rings 1027 elements 2054 modes
Can HFSS solve over 1,000 elements?
38 min 105GB distributed RAM*
*Solved with “accurate” settings
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MPI
• Simulation statistics for an 8x8 vivaldi array on V14 (with RSM) vs. V15 (with MPI)
• The RAM reduction is due to changes with the mesh in the air cells in V15
• The solve time improvement is attributable to MPI and updated algorithmic changes.
RAM [GB]
Time [hh:mm] Speedup vs. V14
V14 FiniteArrayDDM 91 28:10 - V15 FiniteArrayDDM 65 8:37 3.3x V15 Composite Excitations*
63 0:29 58x*
Steered beam
*For a single scan angle
Using 2 HPC Packs
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Capacity – Save Radiated Fields Only
Save Radiated Fields Only Option enables running large array simulations without filling up the hard disk.
8x8 Vivaldi Array 64 unit cells 4 excitations per unit cell 256 total excitations Full array simulation (not composite excitations) Saves fields for each excitation
Setup Disk Space Used
Disk Space Savings
Save all fields (default)
589GB reference
Save radiated fields only
2.98GB 198x
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Conclusion
Part I: Accuracy
Part II: Flexibility
Part III: Speed/Capacity
Conclusion
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• Array masks with padding cells enable great flexibility for easily creating semi-arbitrary shaped arrays • MPI and algorithmic changes have made FA-DDM simulations several times faster in HFSS V15 • Composite excitations allows simulating specific scan angles of huge port count finite arrays quickly and efficiently
Conclusion
• The new FEBI touching ground plane option enables highest accuracy far-field calculations
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Acronyms/Terms
Acronyms DDM - Domain decomposition method FA-DDM - Finite array domain decomposition method FEBI - Finite element boundary integral PML - Perfectly matched layer MPI - Message passing interface Terms Explicit - Means the array is drawn manually without the finite
array tool. Or the array is “explicitly” created.