Q2D实操指导书

1. Q2D简单好用，又快又准。适用于均匀传输线特性阻抗和寄生参数分析，对于长度很短的不连续结构，个人认为Q2D也适合，因为长度太短，TDR分辨率不足难易区分该处阻抗。各种电流分布、电磁场分布亦可有Q2D直观显示。

材料设定（assigning materials）

边界条件设置（assigning boundary）

Q2D中只有Finite Conductivity这一种边界条件，Finite Conductivity Boundaries 其实是一种隐形的 Impedance Boundary ，因为PCB上的任何导体，不管是信号线、还是GND plane or power plane，导体表面肯定是有起伏粗糙的（表面粗糙度），而且导体的电导率是一定的（默认的pec是1e30 siemens/m）。

具体操作：

1. Select an edge.（only edge）

Note Finite conductivity boundary can only be assigned to the following conductor types: Signal Line, Non-Ideal Ground, Reference Ground or Floating Line.（surface Ground就不能设置finite conductivity，同轴线的外导体就是surface Ground）

2. Click 2D Extractor>Boundary>Assign>Finite Conductivity.

注意：Q2D中object设置为导体时，默认设置如下的阻抗边界：

The following are the implicit IBC parameters:

•  Surface Roughness - this is taken to be equal to zero.

• lCoating Thickness - this is taken to be equal to zero. For implicit processes, the solution is solved using the conductor thickness specified.

• lCoating Material - the same material is used as the base object.

指定导体类型（Conductors in Q2D）

软件自己不能区分哪些是信号线，哪些是参考GND，哪些是对性能有影响而不想关注的导体（不看其寄生参数），需要在仿真前先制定，Q2D可定义如下5种导体类型：

• Signal Line

• Non-Ideal Ground

•  Reference Ground 

•  Floating Line

• Surface Ground.

注意：Surface Ground conductors are only allowed in a closed solution type, can only be assigned to the bounding box, and can only be assigned to a non-conducting object.

1. signal line-信号线，最好定义的线，简单明了；

   
   

2. non-ideal Ground，Non-ideal grounds are nonzero impedance grounded conductors whose voltages are allowed to fluctuate during a circuit simulation.（non-ideal是非零阻抗的地平面，如果有电流流经该非零阻抗平面，当电流变化时（开关），会引起地弹噪声）
   

   注意：只有signal line和non-ideal ground 才能看其寄生参数，其他导体均看不到，软件并不计算。

   
   

3. reference Ground-直观明了；

   
   

4. surface Ground-You must declare a closed dielectric object whose surface is connected to a common ground as a “surface ground”. Surface grounds are zero impedance grounded conductors that serve as a return path for all conductors within the ring.（surface ground只能定义在包含同轴内芯的介质上，唯一定义在非导体上的导体类型）

   

   注意：as a surface ground, only the outer surface of the object is assumed to be conductive.（只有介质的外表面是conductive）

5. floating line-Identify floating conductors as floating lines. Floating lines can have a charge applied to them but have no current flowing through them.

   
   

   大概就是如下图所示的，在模型中存在感不是很强的conductor

   
   

   

具体操作：

1. Automatically Assigning Signals；

   
   

   

2. 再按需求划分conductor类型，其中reference ground是一定要定义的
   

求解设置（Specifying Solution Settings）

general下看CG参数勾选admittance，看RL参数勾选Impedance，对应设计remesh次数和求解精度设置。

在CG/RL Advance下，可对应设置收敛次数（收敛次数优先级更高，即使当前已经达到了设定的求解精度）。

运行仿真（run simulation）

先check下有没有错误，同HFSS，略..........

reduce martrix

Reducing a model 's capacitance, inductance, and resistance matrices enables you to quickly and easily vary the excitations and connections of the conductors in your model without having to modify the conductor and source assignments and generate a new solution.

五种reduce martrix操作，大概就是重新定义导体类型，定义net属性，重新计算寄生参数矩阵，不必重新求解，方便快捷。

1. add ground：改变网络属性，改变传输线类型

   
   

   
   

   
   

   
   

   

2. set refenrence ground:改变信号回流路径，慎用。

   
   

   This type of reduction basically replaces the existing return path or reference ground in the design with the newly selected conductor.

   
   

   

3. Parallel Reduction Type:将物体并联
   

   
   

   This type of reduction lets you connect two or more source terminals in parallel, which are then treated as if they were a single object.

   
   

4. 其他两种-略-直观明了

over....就这些东西了，Q2D同样支持变量设置和参数扫描