请问Eigenmode solver 设置的一个问题
The eigenmode solver calculates a finite number of modal field distributions in a closed
device. CST MICROWAVE STUDIO® provides two different eigenmode solvers: AKS
(Advanced Krylow Subspace) and JDM (Jacoby Davidson Method).
These methods work on a completely different mathematical foundation. The JDM solver
can be considered as a more robust solver technology, but the AKS solver may be faster
if many modes are to be calculated. Therefore we recommend the JDM solver only if a
small number of modes (e.g. 1-5) has to be calculated. Otherwise the AKS solver should
be used.
Since the eigenmode analysis does not require the definition of excitation ports, this step
can be omitted. The definition of monitors is also not necessary because the modes
themselves contain all available information about the device.
The solution of lossy eigenmode problems is a challenging task which implies that the
proper consideration of losses will significantly slow down the simulation. Even if the
JDM solver is able to directly solve the lossy eigenmode problem, it may sometimes be
advisable (especially for very small losses) to first calculate the loss free eigenmode
problem and then obtain losses and Q-factors of the device using a perturbation method
in the post processing.
The perturbation method requires material losses to be defined before the eigenmode
simulation is started. Running the AKS solver will always calculate the loss free problem
by simply ignoring the loss definition. The JDM solver can be advised to do so by
activating the Use perturbation method box as shown below:
In the eigenmode solver control dialog box, the most important controls are the Method
(as discussed above) and the number of Modes.
The typical simulation procedure is as follows:
1. Depending on the number of modes, choose the proper solver method:
􀂆 For the direct solution of lossy problems choose JDM.
􀂆 For loss free problems with a small number of modes (e.g. 1-5) choose
JDM.
􀂆 For loss free problems with many modes (e.g. >5) choose AKS.
2. Enter the desired number of Modes (N). The solver will then compute the first N
modes of the device. For the AKS solver, it is often advantageous to specify more
modes to be calculated than you actually need, e.g. enter 20 modes to be
calculated if you actually need 15. In most cases it is a good choice to calculate at
least the first 10 modes of the device.
3. Click the Start button
When using the AKS solver, sometimes a few of the higher modes will not be calculated
with sufficient accuracy and thus be marked with “*”. However, this does not affect the
accuracy of the lower modes and is the reason you should specify more modes to
calculate than you actually need.
The AKS eigenmode solver internally needs an estimation for the frequency of the
highest mode of interest. Usually this frequency is estimated automatically and improved
by refinement passes if necessary.
Performing estimation refinement passes reduces the performance of the AKS
eigenmode calculation. To speed up the AKS eigenmode calculation in these cases, you
can manually enter a guess for the frequency of the highest mode you are looking for.
The AKS eigenmode solver automatically derives such a guess from previously
calculated results and prints this value in the message window.
其实帮助文档里就有的，在cst2006的getting start 的page115
能不能用中文给解释一下?这个我看了，但是究竟什么时候用AKS，什么时候用JD?弄不太明白啊，我现在一般就是用CST仿一下谐振频率和耦合窗的大小，最近才注意到这个，不知道有什么区别:L :L
一般1～5个模式的采用jdm求解，其他的采用aks求解
qi ta de fan yi yixia jiu keyi le ,bushi hen nan de ,shizai bu xing ,natian wo geini fanyi yixia ,huo zhe gei ni zhao ge yingwen de jieshi
Thanks:hi
本征模求解器用来计算封闭器件内有限个模式的场分布，cst里有两种不同的本征模求解器：AKS和JD.lossy
JD.loss free
这两种求解器的数学基础完全不同。JD求解器更稳定，但在算多个模式时，使用aks求解器会更快。
如果只计算少量模式如1～5个模式，最好使用jd求解器，否则使用aks求解器求解
因为严格的考虑损耗会显著的降低仿真速度，故有耗本征模问题的求解是非常具有挑战性的任务，即使
专用的JD。lossy 算法能够直接求解有耗本征模问题，但在损耗非常小的时候，我们也建议你先计算无
耗本征模问题，即使用jd。lossfree 或者aks求解器。然后在后处理中采用微扰法求出器件的损耗和Q值
既然本征模分析无需定义激励端口，这一步就可以忽略掉了。由于模式本身就已经包含了器件的所有有用
信息，故监视器也不用定义了
因此建模完成后便可以记入本征模求解对话框
一般采用下面的原则：
1.依据模式数量，选择适当的求解器算法
直接求解有耗问题，选择Jd lossy
少量模式 如1～5个 选用jd loss free
较多模式，多于5个，的无耗问题，选择aks
2.输入求解的模式数量，求解器将要算出器件的前n个模式，对aks求解器，一般指定比您实际需要的
模式数量多的会比较好，比如你需要15个模式，可以输入20，在大多数情况下，至少要计算器件的头10
个模式
十分感谢呆呆！明白了！:happy