launching the wave in rectangular waveguide

Dear all,

Can someone explain about the diference betwen cylinder wave guide and rectangular wave guide , when both are implemented or simulated. I mean the advantage and disadvantage.

Thanks in advance

One is circular and the other is rectangular.


Probably the biggest difference is that circular guide will support a greater range of propagation modes while in a rectangular guide the polarization stays in one plane, even for long runs.

I believe that the circular waveguide has much lower loss, in the right mode, than rectangular waveguide. Back before the earth cooled, there used to be telephone relay stations around, and they all used circular waveguide to get from the ground level up to the horn antenna at the top of the tower.

If you do not care about loss, most would use rectangular waveguide since it is easier to launch to.

however, there are some interesting properties of circular waveguide that are sometimes still used today. Many of the commercial satellite receivers use a antenna that feed a circular waveguide with a mode transducer that can separate the two different recieved polarizations. That way you can switch between two different satellite feeds with the same antenna.

Here is a picture, one antenna in but TWO sma outputs.

http://en.wikipedia.org/wiki/Low-noise_block_converter

And rectangular OR circular, they both hurt when you drop them on your foot.

I have seen circular guides characterized and having lower loss as well. When you make the loss comparison pay attention to the waveguide size as well. There is no free lunch.

Southworth is a good waveguide reference and it is amusing to pull out a really old technical reference.