也许最常见的传输线类型是同轴电缆。同轴电缆是创建传输线的一种非常好的方法。使用同轴电缆时，了解同轴电缆会很有帮助。与大多数 pcb 传输线不同，同轴电缆的优点在于它可以弯曲且灵活。
Perhaps the most common type of transmission line is the coax. The coax is a very nice way to create a transmission line. Understanding coax can be helpful when working with it. The nice part about coax is that it can be bent and flexible unlike most pcb transmission lines.
基本同轴电缆由内部走线和由电介质隔开的屏蔽构成。同轴电缆的优点是横向电磁（TEM）模式，这意味着磁场和电场垂直于波的传播方向。特性阻抗主要由导体到屏蔽层的距离以及分隔它们的材料的介电常数决定。
The basic coax cable is constructed with an inner trace and a shield separated by dielectric. The property of coax that is nice is the transverse electric magnetic (TEM) mode, which means that the magnetic and electric fields are perpendicular to the direction of the wave propagation. The characteristic impedance is primarily determined by the distance from the conductor to the shield as well as the dielectric constant of material separating them.
同轴电缆传输线型号 Coax Cable Transmission Line Models
已创建模型来近似同轴电缆传输线的特性。Models have been created to approximate the characteristics of the coax cable transmission line.
The characteristic impedance of a coax is:
The time delay in ns/inch is:
The inductance in nH/inch is:
The capacitance in pF/inch is:
The cutoff frequency is:
Reference
[1] Cable Impedance
Related Products: Wire and Cable
