手机天线的电长度是什么意思，它和天线的物理长度有关系吗？

electrical length:
1. Of a transmission medium, its length expressed as a multiple or submultiple of the wavelength of a periodic electromagnetic or electrical signal propagating within the medium.
Note 1: The wavelength may be expressed in radians or in artificial UNITS of angular measure, such as degrees.
Note 2 : In both coaxial CABLES and OPTICAL fibers, the velocity of propagation is approximately two-thirds that of free space. Consequently, the wavelength will be approximately two-thirds that in free space, and the electrical length, approximately 1.5 times the physical length.
2. Of a transmission medium, its physical length multiplied by the ratio of (a) the propagation time of an electrical or electromagnetic signal through the medium to (b) the propagation time of an electromagnetic wave in free space over a distance equal to the physical length of the medium in question. Note: The electrical length of a physical medium will always be greater than its physical length. For example, in coaxial CABLES, distributed resistances, capacitances and inductances impede the propagation of the signal. In an OPTICAL fiber, interaction of the lightwave with the materials of which the fiber is made, and fiber geometry, affect the velocity of propagation of the signal.
3. Of an antenna, the effective length of an element, usually expressed in wavelengths.
Note 1: The electrical length is in general different from the physical length.
Note 2: By the addition of an appropriate reactive element (capacitive or inductive), the electrical length may be made significantly shorter or longer than the physical length.
电长度
电长度：
1.对于传输媒介，它的长度被表示为一个在媒介中传波的电或者电磁信号波长的倍数。
注释 1：波长可能用弧度来表示，或者其它的角度单位来表示，如角度。
注释 2：在同轴电缆和光纤中，传输速率大约为自由空间中的2/3。因此，波长
        大约为自由空间中波长的2/3，而电长度则大约为物理长度的1.5 倍。
2.对于传输媒介，（电长度）用 它的物理长乘以 电或电磁信号在媒介中的传输
  时间（时间为a）与 这信号在自由空间中通过跟媒介物理长度一样的距离时所
  需的时间（时间为b）的比（即电长度=物理长度*a/b） 来考虑。
注释：对于一个物理媒介来说，它的电长度总是大于它的物理长度。例如，在同
      轴电缆中，分布电阻、电容、电感阻碍了信号的传输；在光纤中，光波与
      光纤材料之间的相互作用，以及光纤的几何结构，影响了信号的传输速率。
3.对于天线，天线的有效长度常表示为波长的倍数。
注释 1.电长度跟物理长度通常是不一样的。
注释 2.通过增加一个适当的电抗元件（电容或电感），电长度可以显著的短于或者长于物理长度。

那900和1800哪个电长度大些?

简单这样比 貌似量纲不对

电长度就是物理长度比上波长

我去看看

呵呵 我也看到那个帖子啦 找本微波理论的书 仔细瞅瞅

电长度是微波里的基础性概念

我是因为看了关于天线的高频为什么方向性强的帖子里面提到的，不过还是没看懂哦，提到了电长度这个概念。

谢谢指点！

看一下这个网址 有相关的解释 希望有帮助
http://www.dzsc.com/dzbbs/20050724/2007652199937267.html

就是说：我这个长度，用在某个频率下到底是长还是短啊。

    低频比高频长啊，比较简单的理解，电长度要求长的频段，一般物理长度要长；但是像FICA天线这种通过耦合走出来的就不清楚了；