HFSS:什么是floquet port？

2017-04-16 by:CAE仿真在線來源:互聯網

什么是floquet port?

先來看看官方的定義:

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 con-stants 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 radiat-ing structure. As in the case of a wave port, this information is cast in the form of an S-matrix inter-relating 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.

翻譯如下:

Floquet port 在HFSS中僅用于平面周期性結構(注意,這里的平面指的是端口是平坦的,而不是二維的意思),如平面相控陣和頻率選擇性表面的仿真,這種情況常常把他們理想化成無限大的平面,這時候使用使用Floquet端口的好處是可以只仿真無限大平面的的小單元即可。

Floquet port的方向必須沿著Z軸方向。

Floquet port是平面波,通過頻率、相位、周期性幾何結構,定義其發射方向。

與wave modes一樣,Floquet也有傳播常數(電磁波沿匹配的均勻通信回路傳輸時,表示每單位長度電壓或電流的衰減與相位變化的復常數)和低頻截止頻率。

當你定義一個Floquet port之后,HFSS要求輸入一組模式分量(TE、TM模)來額外定義輻射結構的性能。

下面是來自網絡的其他理解:

Floquet端口基于Floquet模式進行場求解,用于二維平面周期性結構的仿真設計,如平面相控陣列和頻率選擇表面等類型的問題。與波端口的求解方式類似,Floquet端口求解的反射和傳輸系數能夠以S參數的形式顯示;使用Floquet端口激勵并結合周期性邊界,能夠像傳統的波導端口激勵一樣輕松地分析周期性結構的電磁特性,從而避免了場求解器復雜的后處理過程。此外,Floquet端口允許用戶指定端口處入射波的斜入射角和極化方式,然后從求解結果中選擇所關心的極化分量。

平面周期性結構可以看做由一個個相同的單元(Unit Cell)組成,使用Floquet端口和主從邊界條件分析平面周期結構,用戶只需要提取其中一個單元,然后建模,如圖1所示。在設置Floquet端口激勵時需要指定端口的柵格坐標系統(Lattice Coordinate System),該坐標系統的a、b軸分別表示周期性結構單元的排列方向。

HFSS教程

這是另一種角度的理解:
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.

舉個例子:在一個只有一個端口的仿真中:如果你setup in the floquet port is TE00 TM00 TE01 and TM01, 4modes
那么S參數結果是個4x4的矩陣:
(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.

常見錯誤:

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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