[問題] David K. Cheng的一段文字
David K. Cheng第二版電磁學的第632~633頁，為了證明天線的reciprocity property，
將天線A和天線B的發送及接收電路化，化為線性的two-port network
V1 = Z11* I1 + Z12*I2
V2 = Z21* I1 + Z22*I2
而之後有段文字如下：
When the medium in the transmission path between antennas A and B is bilateral
such that reciprocity relations hold, the transfer or coupling impedances Z12
and Z21 are equal. Under normal circumstances, transmitting and receiving
antennas are separated by very large distances, and the coupling impedances
are negligibly small as far as the reaction on the transmitting antenna owing
to scattering by the receiving antenna is concerned. In the limit r→∞,
lim Z12 = 0
r→∞
我的問題是...這邊寫道，當兩個天線距離很遠時，兩者間的阻抗趨近於零??
why?
不是應該因為距離變遠的關係而更大嗎？
煩請版上高手為小弟解惑，謝謝
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