不对称带状线传输线最常见于印刷电路板中，其中从迹线到平面的距离上下不同。对这种阻抗进行建模的能力很好，因为它经常可以在设计中找到。建模近似可用于设计非对称带状线迹线。通过了解非对称带状线传输线，设计人员可以正确构建这些结构以满足他们的需求。
The asymmetric stripline transmission line is most commonly found in a pcb where the distance from trace to planes is not the same distance above and below. The ability to model this impedance is nice because it can often be found in designs. Modeling approximation can be used to design the asymmetric stripline trace. By understanding the asymmetric stripline transmission line, designers can properly build these structures to meet their needs.
Description
带状线由悬在两个接地层之间的扁平导体构成。导体和接地层由电介质隔开。对于两个参考平面，导体和平面之间的距离不同。这种结构很可能是用印刷电路板工艺制造的。
A stripline is constructed with a flat conductor suspended between two ground planes. The conductor and ground planes are separated by a dielectric. The distance between the conductor and the planes is not the same for both reference planes. This structure will most likely be manufactured with the printed circuit board process.
Example
非对称带状线的一个示例是 4 层 pcb，第 3 层上的走线同时参考第 1 层和第 4 层。走线最接近第 4 层，第 4 层对传输线阻抗具有主要影响，但第 1 层仍然会影响该走线的特性阻抗。
An example of an asymmetric stripline is a 4 layer pcb were a trace on layer 3 is referenced to both layer 1 and layer 4. The trace is closest to layer 4 and layer 4 has the dominant effect on the transmission line impedance, but layer 1 would still affect the characteristic impedance of this trace.
非对称带状线传输线模型 Asymmetric Stripline Transmission Line Models
非对称带状线的阻抗 Z 0,AS 可以根据文件 IPC-2141A [1] 中包含的公式计算，特别是第 4.2.5 段。特性阻抗由下式给出：
The impedance Z0,AS for an asymmetric stripline can be computed according to the formulas contained in the document IPC-2141A [1], in particular paragraph 4.2.5. The characteristic impedance is given by:
![Z_{0,AS}=\frac{1}{\sqrt{\varepsilon_r}}\left [ Z_{0,SS}(\varepsilon_r=1, b=h_1+h_2+t)-\Delta Z_{0,air} \right ]](https://www.eeweb.com/wp-content/uploads/CodeCogsEqn-3.png)
Eq. 1
where:
Z 0,SS 是根据公式计算的对称带状线阻抗。1或等式。3 的 对称带状线阻抗工具，提供以下输入值：Ɛ r =1, b=h1+h2+t。Z 0,SS 是以空气为电介质的阻抗，总厚度 b 等于 h1+h2+t。
ΔZ 0,air 由下式给出：
Z0,SS is the symmetric stripline impedance computed according to Eq. 1 or Eq. 3 of the Symmetric Stripline Impedance tool, providing the following input values: Ɛr=1, b=h1+h2+t. Z0,SS is the impedance with air as the dielectric and having total thickness, b, equal to h1+h2+t.
ΔZ0,air is given by the following equation:
Eq. 2
其中，h1 为信号线与下参考平面的距离，h2 为信号线与上参考平面的距离，Z 0,air由下式 给出：
Where h1 is the distance between the signal line and the lower reference plane, h2 is the distance between the signal line and the upper reference plane, and Z0,air is given by:
Eq. 3
Z 0,SS 是根据公式计算的对称带状线阻抗。1或等式。3 对称带状线阻抗工具，依次提供以下输入值：
- Ɛ r =1，b=h1。它是以空气为电介质的阻抗，总厚度 b 等于 h1
- Ɛ r =1，b=h2。它是以空气为电介质的阻抗，总厚度 b 等于 h2
Z0,SS is the symmetric stripline impedance computed according to Eq. 1 or Eq. 3 of the Symmetric Stripline Impedance tool, providing, in turn, the following input values:
- Ɛr=1, b=h1. It is the impedance with air as the dielectric and having total thickness, b, equal to h1
- Ɛr=1, b=h2. It is the impedance with air as the dielectric and having total thickness, b, equal to h2
