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1、2-1Hg!0S/vI pVHFSS Boundary List2-2 Perfect E and Perfect H/Natural Ideal Electrically or Magnetically Conducting Boundaries Natural denotes Perfect E cancellation behavior Finite Conductivity Lossy Electrically Conducting Boundary, with user-provided conductivity and permeability Impedance Used for
2、 simulating thin film resistor materials, with user-provided resistance and reactance in /Square Radiation An absorbing boundary condition, used at the periphery of a project in which radiation is expected such as an antenna structure Symmetry A boundary which enables modeling of only a sub-section
3、of a structure in which field symmetry behavior is assured. “Perfect E” and “Perfect H” subcategories Master and Slave Linked boundary conditions for unit-cell studies of infinitely replicating geometry (e.g. a slow wave circuit & an antenna array)2-3HFSS Boundary Descriptions: Perfect E and Perfect
4、 H/Natural Parameters: None Perfect E is a perfect electrical conductor* Forces E-field perpendicular to the surface Represent metal surfaces, ground planes, ideal cavity walls, etc. Perfect H is a perfect magnetic conductor Forces H-field perpendicular to surface, E-field tangential Does not exist
5、in the real world, but represents useful boundary constraint for modeling Natural denotes effect of Perfect H applied on top of some other (e.g. Perfect E)boundary Deletes the Perfect E condition, permitting but not requiring tangential electrical fields. Opens a hole in the Perfect E planePerfect E
6、 Boundary*Perfect H BoundaryNatural BoundarylarperpendicuErcontinuousErparallelEr*NOTE: When you define a solid object as a perf_conductor in the Material Setup, a Perfect E boundary condition is applied to its exterior surfaces!Perfect H for 2D Aperture (I)2-4 Monopole Over a Ground planePerfect HP
7、erfect H Surface Interior to the Problem Space Behaves Like an Infinitely Thin 2D AperturePerfect H for 2D Aperture (II)2-5 Small Hole Can be “Cut” in infinitely Thin Septum Between the Upper and Lower Guide Using a Perfect H Surface at the HolePerfect HHFSS Boundary Descriptions: Finite Conductivit
8、y2-6 Parameters: Conductivity and Permeability Finite Conductivity is a lossy electrical conductor E-field forced perpendicular, as with Perfect E However, surface impedance takes into account resistive and reactive surface losses User inputs conductivity (in siemens/meter) and relative permeability
9、 (unitless) Used for non-ideal conductor analysis*Finite Conductivity BoundarygattenuatinlarperpendicuE ,r*NOTE: When you define a solid object as a non-ideal metal (e.g. copper, aluminum) in the Material Setup module, and it is set to Solve Surface, a Finite Conductivity boundary is automatically a
10、pplied to its exterior faces!HFSS Boundary Descriptions: Impedance2-7 Parameters: Resistance and Reactance, ohms/square ( /) Impedance boundary is a direct, user-defined surface impedance Use to represent thin film resistors Use to represent reactive loads Reactance will NOT vary with frequency, so
11、does not represent a lumped capacitor or inductorover a frequency band. Calculate required impedance from desired lumped value, width, and length Length (in direction of current flow) Width = number of squares Impedance per square = Desired Lumped Impedance number of squaresEXAMPLE: Resistor in Wilk
12、enson Power DividerResistor is 3.5 mils long 4 m(in direction of flow) andils wide. Desired lumped value is 35 ohms.squareNRRNlumpedsheet/40875.35875.045.3=HFSS Boundary Descriptions: Radiation2-8 Parameters: None A Radiation boundary is an absorbing boundary condition, used to mimic continued propa
13、gation beyond the boundary plane Absorption is achieved via a second-order impedance calculation Boundary should be constructed correctly for proper absorption Distance: For strong radiators (e.g. antennas) no closer than /4 to any structure. For weak radiators (e.g. a bent circuit trace) no closer
14、than /10to any structure Orientation: The radiation boundary absorbs best when incident energy flow is normal to its surface Shape: The boundary must be concave to all incident fields from within the modeled spaceNote boundary does not follow break at tail end of horn. Doing so would result in a con
15、vex surface to interior radiation.Boundary is /4 away from horn aperture in all directions.HFSS Boundary Descriptions: Radiation, cont.2-9 Radiation boundary absorption profile vs. incidence angle is shown at left Note that absorption falls off significantly as incidence exceeds 40 degrees from normal Any incident energy not absorbed is reflected back into the model, altering the resulting field solution! Implication: For steered-beam arrays, the standard radiation boundary may be insufficient for proper analysis. Solution: Use a Perfectly Matched Layer (PML) const
