两个导体可以形成一条传输线。要使用两根线制作效果传输线，最好创建双绞线。通常在使用电线时，如果没有密切注意，很容易创建大的返回路径环路。双绞线有助于在每单位长度的导线上产生更均匀的电感和电容，以通过使返回路径尽可能靠近信号来确保恒定的阻抗。

Two conductors can create a transmission line. To make an effect transmission line with two wires it is best to create a twisted pair. Often when working with wires it is easy to create large return path loops if one is not paying close attention. The twisted pair helps create a more uniform inductance and capacitance per unit length of wire to ensure a constant impedance, by keeping the return path as close to the signal as possible.

我们也应该密切关注的双绞线的几何形状是两个导体之间的距离（中心到中心）和导线的直径。两个导体之间材料的有效介电常数将介于电线绝缘层的介电常数和空气的相对介电常数 (1) 之间。

The geometries of the twisted pair that we should pay close attention too are the distance between the two conductors (center to center) and the diameter of the conductive wire. The effective permittivity of the material between the two conductors will be somewhere between the permittivity of the insulation on the wires and the relative permittivity of air (1).

双绞线的特性 Characteristic Properties of the Twisted Pair

• 特征阻抗 双绞线的特征阻抗是信号沿导体传播时所看到的阻抗。
• 传播延迟 信号的传播延迟是信号传播特定距离所需的时间。该工具以英寸/纳秒为单位计算时间延迟。
• 每单位长度 的电感 信号的电感很有价值。尤其是在仿真工具中为传输线创建模型时。该工具以每英寸纳亨利为单位计算电感
• 每单位长度 的电容 在仿真工具中为传输线创建模型时，通常需要信号的电容。该工具以皮法/英寸为单位计算电容

• Characteristic Impedance The characteristic impedance of the twisted pair is the impedance a signal will see as it travels down the conductor.
• Propagation Delay The propagation delay of the signal is the time it takes for the signal to travel a specific distance. This tool calculates the time delay in inches per nanosecond.
• Inductance Per Unit Length The inductance of the signal is valuable to know. Especially when creating a model for the transmission line in a simulation tool. This tool calculates the inductance in nano-henrys per inch
• Capacitance Per Unit Length The capacitance of the signal is often need when creating a model for the transmission line in a simulation tool. This tool calculates the capacitance in pico-farads per inch

双绞线传输线模型 Twisted Pair Transmission Line Models

已创建模型来近似微带传输线的特性。Models have been created to approximate the characteristics of the microstrip transmission line.

Reference

[1] Cable Impedance

[2] Omicalculator Home page

Related Products: Wire and Cable