HFSS:什么是floquet port？

2017-04-16 by:CAE仿真在线来源:互联网

什么是floquet port?

先来看看官方的定义:

The Floquet port in HFSS is used exclusively with planar-periodic structures. Chief examples are planar phased arrays and frequency selective surfaces when these may be idealized as infinitely large. The analysis of the infinite structure is then accomplished by analyzing a unit cell. Linked boundaries most often form the side walls of a unit cell, but in addition, a boundary condition is required to account for the infinite space above. Floquet ports must be placed along the Z axis. The Floquet port is closely related to a wave port in that a set of modes ("Floquet modes") represents the fields on the port boundary. Fundamentally, Floquet modes are plane waves with propagation direction set by the frequency, phasing, and the geometry of the periodic structure. Just like Wave modes, Floquet modes too have propagation constants and experience cut-off at low frequency. When a Floquet port is present, the HFSS solution includes a modal decomposition that gives additional information on the performance of the radiating structure. As in the case of a wave port, this information is cast in the form of an S-matrix interrelating the Floquet modes. In fact, if Floquet ports and wave ports are simultaneously present, the S-matrix will interrelate all Wave modes and all Floquet modes in the project.

翻译如下:

Floquet port 在HFSS中仅用于平面周期性结构(注意,这里的平面指的是端口是平坦的,而不是二维的意思),如平面相控阵和频率选择性表面的仿真,这种情况常常把他们理想化成无限大的平面,这时候使用使用Floquet端口的好处是可以只仿真无限大平面的的小单元即可。

Floquet port的方向必须沿着Z轴方向。

Floquet port是平面波,通过频率、相位、周期性几何结构,定义其发射方向。

与wave modes一样,Floquet也有传播常数(电磁波沿匹配的均匀通信回路传输时,表示每单位长度电压或电流的衰减与相位变化的复常数)和低频截止频率。

当你定义一个Floquet port之后,HFSS要求输入一组模式分量(TE、TM模)来额外定义辐射结构的性能。

下面是来自网络的其他理解:

Floquet端口基于Floquet模式进行场求解,用于二维平面周期性结构的仿真设计,如平面相控阵列和频率选择表面等类型的问题。与波端口的求解方式类似,Floquet端口求解的反射和传输系数能够以S参数的形式显示;使用Floquet端口激励并结合周期性边界,能够像传统的波导端口激励一样轻松地分析周期性结构的电磁特性,从而避免了场求解器复杂的后处理过程。此外,Floquet端口允许用户指定端口处入射波的斜入射角和极化方式,然后从求解结果中选择所关心的极化分量。

平面周期性结构可以看做由一个个相同的单元(Unit Cell)组成,使用Floquet端口和主从边界条件分析平面周期结构,用户只需要提取其中一个单元,然后建模,如图1所示。在设置Floquet端口激励时需要指定端口的栅格坐标系统(Lattice Coordinate System),该坐标系统的a、b轴分别表示周期性结构单元的排列方向。

HFSS教程

这是另一种角度的理解:
FloquetPortX:Z,FloquetPortY:Z means SXY for mode Z.
FloquetPortX:Z,FloquetPortY:W means SXY going from mode Z on the input to mode W on the output.

举个例子:在一个只有一个端口的仿真中:如果你setup in the floquet port is TE00 TM00 TE01 and TM01, 4modes
那么S参数结果是个4x4的矩阵:
(1,1)is S11 for TE00, which means the te00's reflection coefficient, (1,3) is S11 for TE00 and TE01,which means when ur input is TE00, it exciters TE01 mode, and this TE01 get back to the port. Similarily, (3,2) means s11 for TE01 and TM00, which means the reflection of TM00 exicted by the input TE01.

常见错误:

1、Error: slave boundary cannot be built!

Reason: the structure of the two face is not the same. check the axis of all the two face to see if the length is not the same.

附件1:HFSS Floquet Ports.pdf

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