Presentation%20for%20Introduction%20of%20FISC

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MURI Progress ReviewElectromagnetic Simulation
of Antennas and Arrays with Accurate Modeling
of AntennaFeeds and Feed Networks
PI J.-M. Jin Co-PIs A. Cangellaris, W. C. Chew,
E. Michielssen Center for Computational
Electromagnetics Department of Electrical and
Computer Engineering University of Illinois at
Urbana-Champaign Urbana, Illinois
61801-2991 Program Manager Dr. Arje Nachman
(AFOSR) May 17, 2005
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Problem Description
Problem characteristics
Problem configuration

• Very large structures
• Space/surface waves
• Conformal mounting

Antenna/platform interactions

• Complex structures
• Complex materials
• Active/nonlinear devices
• Antenna feeds

Antenna array elements

• Complex structures
• Complex materials
• Multi-layers
• Passive/active circuit elements

Distributed feed network
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Solution Strategy
Simulation techniques
Problem configuration
Antenna/platform interactions
MLFMA/PWTD coupled with ray tracing
FE-BI coupling
Antenna array elements
Time/frequency- domain FEM IE
Broadband macromodel
Distributed feed network
Time/frequency- domain FEM
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Accurate Antenna Feed Modeling Using the
Time-Domain Finite Element Method

• Z. Lou and J.-M. Jin
• Center for Computational Electromagnetics
• Department of Electrical and Computer Engineering
• University of Illinois at Urbana-Champaign
• Urbana, Illinois 61801-2991
• j-jin1_at_uiuc.edu

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Typical Feed Structures

• Antenna element (opened for visualization of
  interior structures)

• Details showing coaxial cable, microstrip line
  and radial stub.

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Feed Modeling
1. Probe model (Simple approximate)
2. Coaxial model (Accurate)
At the port
Mixed boundary condition
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Feed Modeling
Waveguide Port Boundary Condition
By mode decomposition
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Conversion to Time Domain
Frequency-domain operators
Time-domain operators
Inverse Laplacian Transform
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Time-Domain WPBC
Time-Domain Formulation
Assume dominant mode incidence
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Monopole Antennas
Measured data J. Maloney, G. Smith, and W.
Scott, Accurate computation of the radiation
from simple antennas using the finite difference
time-domain method, IEEE Trans. A.P., vol. 38,
July 1990.
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Five-Monopole Array (Geometry)

• Finite Ground Plane
• 12 X 12
• Thickness 0.125
• SMA Connector
• Inner radius 0.025
• Outer Radius 0.081
• Permittivity 2.0

unit inch
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Monopole Array (Impedance Matrix)
1 2 3
4 5
5 4 3 2
1
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Monopole Array (Gain Pattern)
Feeding mode Port V excited, Ports I-IV
terminated. Freq 4.7GHz
f 0o (x-z plane)
f 45o
f 135o
f 90o (y-z plane)
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2 X 2 Microstrip Patch Array

• Substrate
• 12 X 12
• Thickness 0.06
• Permittivity 3.38
• SMA Connector
• Inner radius 0.025
• Outer Radius 0.081
• Permittivity 2.0

unit inch
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Patch Array (Impedance Matrix)
1 2
3 4
4 3 2
1
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Impedance Matrix (FETD vs FE-BI)
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Patch Array (Gain Pattern at 3.0GHz)
x-z plane
Feeding mode
y-z plane
Phasing Pattern
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Antipodal Vivaldi Antenna
Reflection at the TEM port
The 2000 CAD benchmark unveiled, Microwave
Engineering Online, July 2001
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Antipodal Vivaldi Antenna
E-plane
Radiation patterns at 10 GHz
H-plane
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Layer-by-Layer Finite Element Modeling of
Multi-Layered Planar Circuits

• H. Wu and A. C. Cangellaris
• Center for Computational Electromagnetics
• Department of Electrical and Computer Engineering
• University of Illinois at Urbana-Champaign
• Urbana, Illinois 61801-2991
• cangella_at_uiuc.edu

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Layer-by-Layer Decomposition

• 3D global meshing replaced by much simpler
• layer-by-layer meshing
• 2D-meshing used as footprint for 3D mesh in each
  
• layer
• 3D mesh developed from its 2D footprint through
• vertical extrusion
• If ground planes are present, they serve as
• physical boundaries between the layers
• Otherwise mathematical planar surfaces are used
  to
• define boundaries between adjacent layers

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Example of Layer-by-Layer Mesh Generation
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Layer-by-Layer FEM Solution

• FEM models developed for each layer
• Overall solution obtained is developed through
  enforcement of tangential electromagnetic field
  continuity at layer boundaries
• Assuming solid ground plane boundaries, layers
  interact through via holes and any other
  apertures present in the model
• Direct Domain Decomposition-Assisted Model Order
  Reduction (D3AMORe)
• Reduced-order multi-port macromodels developed
  for each layer with tangential electric and
  magnetic fields at the via holes and apertures in
  the ground planes as port parameters
• On-the-fly Krylov subspace-based broadband
  multi-port reduced-order macromodel generation
• Overall multi-port macromodel constructed through
  the interconnection of the individual multi-ports
  

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Demonstration
Tunable bandpass filter with surface-mounted caps
Via hole
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Two Signal Layers
Pins used to strap together top and bottom ground
planes
Input/output ports
Connecting ports
Connecting ports
microstrip layer (top)
stripline layer (bottom)
The filter is decomposed into a microstrip layer
and stripline layer. Ground planes are solid
hence, coupling between layers occurs through the
via holes.
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Tunable band-pass filter (cont.)
D3AMORe FEM Solution (w/o surface-mounted cap)
Reference Solution Transmission line model with
ideal 10 fF caps for modeling the gaps. Impact of
vias is neglected.
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Tunable band-pass filter (cont.)
Use of surface-mounted caps help alter the
pass-band characteristics of the filter
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Hybrid Antenna/Platform Modeling Using Fast TDIE
Techniques

• E. Michielssen, J.-M. Jin, A. Cangellaris,
• H. Bagci, A. Yilmaz
• Center for Computational Electromagnetics
• Department of Electrical and Computer Engineering
• University of Illinois at Urbana-Champaign
• Urbana, Illinois 61801-2991
• emichiel_at_uiuc.edu

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Progress in TDIE SchemesResulting from this
MURI Effort

• Higher-order TDIE solvers
• TDIE solvers for material scatterers
• TDIE solvers for surface-impedance scatterers
• TDIE solvers for periodic applications
• TDIE solvers for low-frequency applications
• Parallel TDIE solvers
• PWTD based accelerators
• TD-AIM based accelerators
• More accurate (nonlinear) antenna feed models
• More complex nonlinear feeds
• More accurate S- / Z- parameter extraction
  schemes
• Symmetric coupling schemes between different
  solvers (including cable EM interactions)

Previous code
Added
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Code Characteristics

1. A higher-order MOT algorithm for solving a hybrid
   surface/volume time domain integral equation
   pertinent to the analysis of conducting/inhomogene
   ous dielectric bodies has been developed
2. This solver is stable when applied to the study
   of mixed-scale geometries/low frequency phenomena
3. This algorithm was accelerated using PWTD and
   TDAIM technology that rigorously reduces the
   computational complexity of the MOT solver from
   to
4. H1 Linear/Nonlinear circuits/feeds in the system
   are modeled by coupling modified nodal analysis
   equations of circuits to MOT equations
5. H2 A ROM capability was added to model small
   feed details
6. H3 Cable feeds are modeled in a fully consistent
   fashion by wires (outside) and 1-D IE or FDTD
   solvers (inside)

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Nonlinear Feed Active Patch Antennas
B. Toland, J. Lin, B. Houshmand, and T. Itoh,
Electromagnetic simulation of mode control of a
two element active antenna, IEEE MTT-S Symp.
Dig. pp. 883-886, 1994.
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Nonlinear Feed Reflection-Grid Amplifier
Amplifier built at University of Hawaii,
supported through ARO Quasi-Optic MURI
program. Pictures from A. Guyette, et. al. A
16-element reflection grid amplifier with
improved heat sinking, IEEE MTT-S Int. Microwave
Symp., pp. 1839-1842, May 2001.
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Nonlinear Feed Reflection-Grid Amplifier
A. Guyette, et. al. A 16-element reflection
grid amplifier with improved heat sinking, IEEE
MTT-S Int. Microwave Symp., pp. 1839-1842, May
2001.
Each chip is a 6-terminal differential-amplifier
that is 0.4 mm on a side
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Interfacing with ROMsMixed Signal PCB with
Antenna
1
3
2
4
4 mm
6
7
10
9
12 cm
8.0 cm
11
5
8
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Interfacing with ROMsMixed Signal PCB with
Antenna

• Full-wave solution only at the top layer
• Dimension of the 11-port macro-model 623
• Bandwidth of macro-model validity 8 GHz
• Plane wave incidence digital switching currents

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Interfacing with ROMsMixed Signal PCB with
Antenna
3 m
8 cm
1.5 m
1.3 m
12 cm
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Interfacing with ROMsMixed Signal PCB with
Antenna
Received at port 8
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Cable Feeds TD LPMA Analysis
King Air 200
13.3 m
3.4 m
16.6 m
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Cable Feeds TD LPMA Analysis
Antenna feed-point
Antenna feed-network
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Cable Feeds TD LPMA Analysis
Dielectrics not shown
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Using Loop Basis to Solve VIE, Wide-Band FMA for
Modeling Fine Details, and a Novel Higher-Order
Nystrom Method

• W. C. Chew
• Center for Computational Electromagnetics
• Department of Electrical and Computer Engineering
• University of Illinois at Urbana-Champaign
• Urbana, Illinois 61801-2991
• w-chew_at_uiuc.edu

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Volume Loop Basis

• Advantages
• Divergence free
• Less number of unknowns (A reduction of 30-40)
• Reduction in computation time
• Easier to construct and use than other
  solenoidal
• basis, e.g. surface loop basis no special
  search
• algorithm is needed.
• Stable in convergence of iterative solvers even
  with the
• existence of a null space

RWG Basis
Loop Basis
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Volume Loop Basis
Example
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Volume Loop Basis
Bistatic RCS
Incident Wave 1 GHz, z to z Relative
permittivity 4.0 No of tetrahedrons 3331 No of
RWG basis 7356 (11.5) No of loop basis 4965
(10.05) Basis reduction 32.5 No of iterations
RWG 159 Loop 390
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Full-Band MLFMA
Incident Wave 1 MHz ? 45deg, F 45deg No
of triangles 487,354 No of unknowns 731,031
7 x 7 fork structure
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Novel Nystrom Method
Scattering by a pencil target
a0.1 m d3 m t0.173 m f1.0 GHz
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Novel Nystrom Method
Scattering by an ogive
a1 inch d5 inchs f1.18 GHz
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Novel Nystrom Method
Scattering by a very thin diamond
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Novel Nystrom Method
Higher-order convergence for ogive scattering
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Novel Nystrom Method
Higher-order convergence for pencil scattering
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Conclusion
Past progresses

• FEM ROM modeling of multilayer, distributed
  feed network (Cangellaris)
• Accurate, broadband antenna/array modeling with
  frequency- and time-domain FEM (Jin)
• Linear/nonlinear feeds, cable feeds,
  antenna/platform interaction, TDIE/ROM
  integration (Michielssen)
• Full-band MLFMA, loop-basis for VIE, and
  higher-order Nystrom method (Chew)

Future work

• Hybridization of FEM and ROM to interface antenna
  feeds and feed network
• Hybridization of FEM and TDIE (TD-AIM PWTD) or
  MLFMA to model antenna/platform interaction
• Parallelization to increase modeling capability