05_边界与端口设置1

HFSS Boundary List




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 simulating „thin film resistor‟ materials, with user-provided resistance and reactance in /Square Layered Impedance
边界与端口设置
电子科技大学 贾宝富
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Boundary/Excitations - Overview

Why are They Critical?

For most practical problems, the solution to Maxwell‟s equations requires arigorous matrix approach such as the Finite Element Method (FEM) whichis used by Ansoft HFSS.
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Perfect H for 2D Aperture (II)

Small Hole Can be “Cut” in infinitely Thin Septum Between the Upper and Lower Guide Using a Perfect H Surface at the Hole Perfect H

*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!!


User inputs conductivity (in siemens/meter) and relative permeability (unitless) Used for non-ideal conductor analysis*
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HFSS Boundary Descriptions: Impedance
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HFSS Boundary Descriptions: Layered Impedance

Parameters: Surface Roughness; Layer; Thickness/Type; Materials

用于定义多层均匀材料组成的边界。如在某种涂敷吸波材料散 射特性的计算中，可以使用这种边界。

Parameters: Resistance and Reactance, ohms/square (/)

Impedance boundary is a direct, userdefined surface impedance

Use to represent thin film resistors Use to represent reactive loads Reactance will NOT vary with frequency, so does not represent a lumped „capacitor‟ or „inductor‟ over a frequency band.

E parallel
Perfect H Boundary
Forces E-field perpendicular to the surface Represent metal surfaces, ground planes, ideal cavity walls, etc. Forces H-field perpendicular to surface, Efield tangential Does not exist in the real world, but represents useful boundary constraint for modeling
Perfect H应用实例
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Perfect H for 2D Aperture (I)

Monopole Over a Ground plane
Perfect H
Perfect H Surface Interior to the Problem Space Behaves Like an Infinitely Thin 2D Aperture



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边界条件定义的覆盖
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HFSS Boundary Descriptions: Perfect E and Perfect H/Natural
E perpendicu lar
Perfect E Boundary*

Parameters: None

Perfect E is a perfect electrical conductor*

The wave equation solved by Ansoft HFSS is derived from thedifferential form of Maxwell‟s equations. For these expressions to be valid, it is assumed that the field vectors are: single-valued, bounded, and have a continuous distribution (along with their derivatives) Along boundaries of media or at sources, Field vectors are discontinuous Derivatives of the field vectors have no meaning

„Deletes‟ the Perfect E condition, permitting but not requiring tangential electrical fields. Opens a „hole‟ in the Perfect E plane
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Perfect E应用实例
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3 .5 0.875 4 Rlumped 35 Rsheet 40 / square N .875 N

Length (in direction of current flow) Width = number of „squares‟ Impedance per square = Desired Lumped Impedance number of squares

Finite Conductivity is a lossy electrical conductor

Finite Conductivity Boundary

E-field forced perpendicular, as with Perfect E However, surface impedance takes into account resistive and reactive surface losses
EXAMPLE: Resistor in Wilkenson Power Divider
Resistor is 3.5 mils long (in direction of flow) and 4 mils wide. Desired lumped value is 35 ohms.

Calculate required impedance from desired lumped value, width, and length

Boundary Conditions define the field behavior across discontinuous boundaries
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Boundary/Excitations - Overview
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Boundary/Excitations - Overview
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Layered Impedance Boundary
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HFSS Boundary Descriptions: Radiation

Parameters: None

Boundary is /4 away from horn aperture in all directions.
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Finite Conductivity

趋肤深度
1 = f
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DC versus AC
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HFSS Boundary Descriptions: Finite Conductivity
E perpendicu , attenuatin lar g

Parameters: Conductivity and Permeabilityes not follow „break‟ at tail end of horn. Doing so would result in a convex surface to interior radiation.