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waveguide stairs - E-field proble

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mauloftin

mauloftin

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waveguide stairs

Hi,

I need do the stairs in waveguide - see the picture, it is model of "waveguide hole".

Can you tell me, how can I predict the design of stairs? Have you some theory or can you tell me, where can I find it?

Thank you!

 

Re: waveguide stairs

Is there an E-field probe that you did not draw?

Those "stairs" are quarter wave impedance transform sections. You choose the wave impedance to match the end impedance. Mathaie, Young, and Jones have a section on such transformers. Other older papers exist with titles like "chebychev impedance transformers", etc.
 

Re: waveguide stairs

biff44 said:
Is there an E-field probe that you did not draw?

Those "stairs" are quarter wave impedance transform sections. You choose the wave impedance to match the end impedance. Mathaie, Young, and Jones have a section on such transformers. Other older papers exist with titles like "chebychev impedance transformers", etc.
Click to expand...

Thank, but I can not find "chebysev impedance transformers", do you know, where can I find "good" theory? How can I calculate the dimensions of the stairs?
Are you sure, that is it QUATER wave impedance transform sections?
 

Re: waveguide stairs

Here are some links

**broken link removed**

**broken link removed**

http://www.ittc.ku.edu/~jstiles/723...Multisection_Matching_Transformer_package.pdf

**broken link removed**

http://www.ece.rutgers.edu/~orfanidi/ewa/ch12.pdf

Added after 8 minutes:

Be aware, they spell chebychev differently in different countries.

I would bet they are quarterwave steps. They could be other lengths, like 3/4 wave, but you would end up with 3X less bandwidth for the impedance transform(I think).

Rich
 
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Re: waveguide stairs

OK, thank, but, How can I change impedance of rectangular waveguide?

Exactly:

see the picture: Z = kη/β, η=η0=377 Ω; k=ω√µε, β=√k²-kc²

and kc = √(mπ/a)²+(nπ/b)²

but for TE10, m=1 and n=0, so the "(nπ/b)²" = 0 and » the impedance Z is independent of the dimension "b".

a - longer sides of the waveguide
b - shorter sides of the waveguide

I need to do stairs in the "b-plane"

Thank

 

Re: waveguide stairs

Yes, you are right, the wave impedance in the TE10 mode does not depend on b(height). Never the less, this is how it is done. I would refer you to Mathaei, Young, and Jones section 6.08 (pages 300 - 304) for an example of matching two equal width waveguides by means of stepped height quarter wave sections.

maybe you do not think of it as actual quarter wave impedance sections, but rather as a series of height discontinuities spaced by quarterwave? Theory of small reflections?

Some emag guy can jump right in here and comment!
 

waveguide stairs

Hi,

can you tell me, what do you think:

"Mathaei, Young, and Jones section 6.08 (pages 300 - 304)"

- what is it, it is book?

Thank
 

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