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1、,Modeling and Optimizing Photonic Bandgap (PBG) Structures,No Boundaries workshop,Richard Remski Application Engineer, Texas,Synopsis I,Statement of Problem and Possible Applications PBG Definition and Types Applications Pertinent HFSS/Optimetrics Features Modeling Methodologies Direct Transmission
2、Method Model Setup Results Obtained Example Project and ResultsSquare-rod dielectric lattice Dispersion Diagram Method Model Setup - Nominal Model Setup - OptimetricsTM Example Projects, with ResultsSquare-pad PBG SurfaceUC-PBG SurfaceSquare-rod dielectric lattice,Synopsis II,Reflection-Phase Analys
3、is Method Model Setup - Nominal Model Setup - OptimetricsTM Example Project with ResultsHexagonal pad PBG surface Optimization Analysis with PBGs General Considerations and Suggestions Case Study 1: Direct Transmission Method Retuning the Dielectric-rod lattice Case Study 2: Reflection Phase Method
4、Generating an overlapping Bluetooth Hexagonal pad PBG Surface References,What is a PBG?,A Photonic Bandgap (PBG) structure, or electromagnetic crystal, is a repeating construction which exhibits useful band rejection behavior for microwave or millimeter wave engineering. Behavior is analogous to the
5、 characteristics of atomic crystal structures in Optical and Solid-State physics, and therefore generally discussed using similar terms. PBGs may occur in bulk form (substrates) or surface form (circuits with or without ground planes) Characteristics of useful PBG constructs include: Inability to ca
6、rry a propagating electromagnetic wave within its forbidden frequency band (bulk and surface) DC conductance often maintained (surfaces w/ ground planes) Reflects incident waves in-phase rather than imaged (surfaces),What is a PBG?,A Photonic Bandgap (PBG) structure is a repeating construction which
7、 exhibits useful behavior for microwave or millimeter wave engineering. Behavior is analogous to the characteristics of atomic crystal structures in Solid-State physics, and therefore discussed using similar terms. Also sometimes called electromagnetic crystals. Physical Characteristics: repeating f
8、eatures (array symmetry), often much smaller than wavelength of interest Electrical Characteristics: Does not carry EM waves at certain frequencies (the forbidden frequency range or band gap).,Solid PBG: substrate with array of drilled holes, or substrate rods in air,Surface PBG: array of repeating
9、circuit elements, with or without vias and ground layer. Sometimes also called metallo-dielectric PBGs.,Potential Applications of PBGs,Array design applications could include: Novel TEM Mode waveguides for feed structures (Reference A) Reduced-loss antenna substrate materials (Reference B) Dielectri
10、c-filled waveguide feeds with built-in band rejection filtering Non-imaging ground planes which improve element performance (References D, E),NOTE: Included references are not offered as the seminal or original works discussing each application, but contain the specific designs used as examples for
11、this presentation.,HFSS Features Pertinent to PBG Analysis,Full-featured FEA Solver Robust Meshing, Convergence ALPS Fast-Frequency Sweep Linked Boundary Conditions Unit-cell modeling of infinitely repeating structure Unlimited master/slave wall pairs and orientations Eigenmode Solver Direct eigenmo
12、de extraction without excitation PML automation via macros Permits “open” termination for eigenmode solutions Field Calculator Complex, algebraic and calculus operations on any output field quantity OptimetricsTM Interface for parametric variable sweeps,Unique!,Unique!,Unique!,Unique!,Unique!,PBG Mo
13、deling Methodologies in HFSS,Direct-Transmission Method: (HFSS) “Waveguide Simulation” approach with finite number of periods Suitable for 3D PBGs (substrates) Transmission obtained directly from S-parameters Dispersion Diagram Method (HFSS+OptimetricsTM) Optimetrics-managed Eigensolution sweep with
14、 infinite array unit cell Suitable for surface PBG circuitry as well as substrates Dispersion diagram plotted from unified HFSS results Reflection-Phase Analysis Method (HFSS+OptimetricsTM) Optimetrics-managed incident wave frequency sweep with post-processor calculations, on infinite array unit cel
15、l Suitable for surface PBG circuitry as well as substrates Reflection-phase plotted from unified HFSS results,Basic PBG Modeling Methodologies in HFSS,Waveguide Simulator Approach: Uses HFSS only, provides only transmission vs. frequency data. Valid only for some symmetry cases and for finite period
16、s in propagation direction. This basic approach is possible in other FEA/FDTD packages,Unit Cell Approaches (2 types): Uses HFSS and OptimetricsTM both. Applicable for all symmetry cases and infinite arrays. Type 1: Dispersion Method solves Eigenmode problem for a variety of boundary conditions, provides dispersion diagram data identifying band gap. Type 2: Reflection-Phase Method solves reflected phase vs. frequency of an Optimetrics-managed sweep which also identifies band gap. ONLY ANSOFT
