What are the parameters needed for an appropriate waveguide?

[gundam]

return loss recommended vaweguide installation

Hi everyone,

Can I ask what are the parameters to choose for an appropriate waveguide? Is reflection coefficent part of these parameters? If so, how does this come into the picture? Thanks.

 

[saryee]

Re: Question on Waveguide

What kind of waveguide do you plan to use, rectangular, coaxial, mistrip, etc?

 

[flatulent]

Re: Question on Waveguide

Waveguides are very old technology. They come is steps of size for different frequency ranges. You first select the frequency and then you have a choice of one or two sizes at the most. The main advantage of waveguide is low attenuation and high power handling. Select the guide with the lowest attenuation at your frequency.

 

[gundam]

Re: Question on Waveguide

Waveguides are very old technology. They come is steps of size for different frequency ranges. You first select the frequency and then you have a choice of one or two sizes at the most. The main advantage of waveguide is low attenuation and high power handling. Select the guide with the lowest attenuation at your frequency.

Hi Flatulent,

I'm using a rectangular waveguide and I'm using the frequency from 26GHz to 32GHz. With regards to the attenuation, why is it that the attenuation is low? How do I compute to compute to get the lowest attenuation since my frequency is in range instead of a single frequency?

Thanks a lot

 

[flatulent]

Re: Question on Waveguide

Check the data sheet for the waveguides. The magnetic field at the walls induce currents in the walls and this is the main source of loss. Also at your frequency the wall smoothness and dimensional uniformity down the direction of wave travel will be a big factor.

http://www.swissatv.ch/academie/Waveguide Attenuation.pdf is a graph of standard sizes and their attenuations.

 

[sergio mariotti]

Re: Question on Waveguide

The requested WG type for your needs is the WR28.
The choiche for a waveguide istead other type of tx lines, due to the very low attenuation, call for high power too.

Generally, if you carry high power a vaweguide is a must. Often, for very high power, to reduce the risk of arc spark inside, special gas filled waveguide are used.

The attenuation is due to metal conductivity, surface roughness, and the mode.
Usual rectangular waveguide are exited on TE10 mode, but for exoctic application, where loss is important, surmoded (read larger) waveguide are used.

VSWR is generally lower in waveguide rather coax. For coax domain a 20 dB Return Loss is generally accepted as "good", in waveguide domain, 30 dB is "common" and 40 dB is "good".

 

[gundam]

Re: Question on Waveguide

Check the data sheet for the waveguides. The magnetic field at the walls induce currents in the walls and this is the main source of loss. Also at your frequency the wall smoothness and dimensional uniformity down the direction of wave travel will be a big factor.

h**p://www.swissatv.ch/academie/Waveguide%20Attenuation.pdf is a graph of standard sizes and their attenuations.

Hi Flatulent,
Thanks but the graph that you gave do not have frequency higher than 30GHz, is there another graph that have frequency higher than 30GHz?

Thank you

 

[sergio mariotti]

Re: Question on Waveguide

Find the attached MS Excel file.
It contains attenuation data collect from many data sheets coming from Continental Waveguide, Hewlett Packard, Millitech, Hughes.
All data are referred to "theoretical attenuation" that is a calculated attenuation. In real case, surface roughness, dirty, oxidation, water vapour, temperature etc. plays a role that increase sligly the attenuation.