[第五课]HFSS边界条件类型

Perfect E boundary B'gk/^6$eg  
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A perfect E boundary is used to represent a perfectly conducting surface in a structure. p\]LEP\z,  

Perfect H boundary n6UU6t{  
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A perfect H boundary represents a surface on which the tangential component of the H-field is the same on both sides. For internal surfaces, this results in a natural boundary through which the field propagates. For surfaces on the outer surface of the model, this results in a boundary that simulates a perfect magnetic conductor in which the tangential component of the H-field is zero. ^5 =E`q".  

Radiation boundary Ayt!a+J  
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A radiation boundary is used to simulate an open problem that allows waves to radiate infinitely far into space, such as antenna designs. ANSYS Electronics Desktop absorbs the wave at the radiation boundary, essentially ballooning the boundary infinitely far away from the structure. In HFSS, these are sometimes described as Absorbing Boundary Condition, or ABC. T-i]O*u  
A radiation surface does not have to be spherical, but it must be exposed to the background, convex with regard to the radiation source, and located at least a quarter wavelength from the radiating source. In some cases the radiation boundary may be located closer than one-quarter wavelength, such as portions of the radiation boundary where little radiated energy is expected. tSa%ZkS  

Symmetry boundary ruVm8BO  
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A symmetry boundary represents a perfect E or perfect H plane of symmetry. Symmetry boundaries enable you to model only part of a structure, which reduces the size or complexity of your design. RIlPH~  

PML boundary P5Fm<f8\  
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A perfectly matched layer (PML) boundary is used to simulate materials that absorb outgoing waves. Setting up a PML boundary is similar to setting up a radiation boundary. You start by drawing a virtual object around the radiating structure. However, instead of placing a radiation boundary on its surfaces, you add PMLs to fully absorb the electromagnetic field. You can also assign PMLs to Region objects. PML objects on a region are updated when the region is updated by changing a region property or variable value. If you do assign PML objects to a region, you cannot perform geometry operations or copy and paste operations on that region. Region-dependent CS cannot be set as current CS. *l|CrUa  
ANSYS Electronics Desktop can create PMLs automatically, or you can create them manually. Create PMLs automatically if the base object touching the PML is planar and its material is homogeneous. HFSS creates a separate PML object for each covered face. The PML boundaries are grouped in the Project tree under the Boundaries icon. Within these groupings, you can edit the radiation parameters (for example, as Incident Wave Port) in order to set up the right total field excitation based on the physical optics approach. PML radiation boundaries are not generated in Eigenmode projects. #fwG~Q(  
In creating PMLs, you can select non rectangular sheet objects as long as they do not touch any other selected face. The underlying object does not have to be a box. If there are faces that touch, the touching faces must be locally box-like. You can assign variables to the dimension properties of the base object. Changing the variable values also changes the associated PMLs. *Owq_)_(|  
PML Compared to Radiation Boundaries 1iz\8R:0  
Compared to Radiation boundaries, which create absorbing boundary conditions (ABC), PMLs in general make it more difficult for the iterative solver to reach convergence compared to the same model with using ABCs. PMLs also require significantly more RAM. The advantages for PMLs are that they absorb a much wider range of waves in terms of frequency and direction. As a result, you can put PMLs much closer to the discontinuities. This gives a smaller model. ABCs efficiently absorb normal incident waves. You have to put ABCs far away enough from the discontinuities. ,Ti#g8j  

常用的BC有理想导体边界，用以代替理想金属表面。辐射边界和理想匹配层用于天线辐射模拟无限大开放空间。集总RLC边界用来模拟RLC器件。对称边界在场结构对称时用来降低模型复杂度。主从边界用在周期结构中。