描述的天線能工作嗎?


1

為接收業餘無線電衛星,經常使用旋轉天線(由兩個異相饋電的交叉偶極子組成)。

enter image description here


我最近有了一個主意-如果用同軸電纜(所謂的bazooka天線)製成兩個半波長偶極子,然後以如下的T形連接:

  ' 1/4 wl center
  '
  " 1/4 wl braid bent back
  "
  ."""""----
  # 1/4  1/4
  #
  #
  #
  # feed coax
  #

(垂直和水平天線電纜在中間點連接到饋線(用#表示)

編輯:這些元件通過1/4波長的相線連接90度,而不是我最初描述的180度。

這根天線會像旋轉門一樣工作嗎?

5

The purpose of a turnstyle antenna for satellite work is to generate a circularly polarized radiation pattern off of its axis. By adjusting the phasing of the feed to the two crossed dipoles, the circular polarization can be switched between left and right hand polarization.

In your diagram of the proposed antenna, one element is shown to meet at is end with the other element. This is essentially an inverted V antenna. Changing the phasing of the two legs will simply reduce the gain of the antenna. No circular polarization will be realized in this configuration. As a result, the antenna would not be effective as a satellite antenna.


0

You specify that

the vertical and the horizontal antenna cables are connected together at the middle point (in parallel, center-braid braid-center and to the feeder cable)

Swapping the two conductors of a transmission line (in the cases where it makes sense at all) produces a 180° phase shift, not a 90° one. Therefore, this antenna design will not produce circular polarization.

If your antenna design is based on identical perpendicular elements, one of those elements must have a 90° phase shift applied such as by a delay line (1/4 wave extra length of coax).

If you did add a 90° phase shift to one element it seems like it could work but I'm not sure what the effect of having the two ends of differing voltage meet at a corner would be. I think at that point you would be better off using antenna modeling software to get a simulated answer.


-1

There are 2 main ways to create the 180 degree phase shift required for circular polarization. A delay in the feed lint (1/4 wavelength longer to one than the other) or physical (antennas at right angles). It does not matter how the phase shift is achieved, the results are the same. So if the antenna matches one of these methods, circular polarization will be achieved. Even when minor errors are present the result is still "mostly" circular (think oval) polarization. If these conditions are not met you will get a different result.