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Waveguide to microstrip Transition?

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odyseus

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Hi All,
I have an HFSS simulation for a Ka-Band waveguide to microstrip transition, that I need to scale for Ku-band. The design uses a stepped ridge to transform the 50 ohm microstrip up to the 300ohm freespace.
Can anyone point me to any notes/papers/articles etc that will tell me what parts of the design are frequency depenadent, so that I can frequency scale them.
I've had a search on this forum and google and can't find anything that gives me practical design data.
All the best
Ody
 

Azulykit

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This isn't exactly what you were looking for but it may be helpful:

h**p://register.itfind.or.kr/Report01/200401/IITA/IITA-0400-026/IITA-0400-026.pdf

I had book on the subject years ago but it got away from me and I have not been able to recover it. I will poke around and see what I can find.

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odyseus

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Thanks for that but the design I was given uses a stepped ridge instead of a probe - as shown in the attached drawing. I was told to just frequency scale it? but which dimensions. I did try frequency scaling the step lengths with limited sucess??
All the best
Ody

 

Azulykit

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It looks like you are after an end-feed launch. Are you feeding the transition with a coax?

I would create a parametric model where the step length and heights are variables and just play around a bit. You might get lucky with minimal effort. The next step would be to try an optimizer. the size of the gap at the back of the waveguide is another dimension to vary. I have usually seen more than three steps but if this works don't mess with it.

You might also look into a technique called "mode matching".

Good luck.
 

odyseus

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Yep, I'm feeding from microstrip. I'll give optimetrics a go, but I suspect it will take a long while, as I'll have to vary many dimensions. I was hoping for a paper so that I could get reasonable starting values at KU-band, using the optimised values at KA-band..
All the best Ody
 

Azulykit

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I saw several citations on the ieee site (Xplore) on the subject of microstrip to waveguide transitions. You might see if any of them are helpful.

I happen to be sitting in an airport waiting lounge. There is a sparrow flying around and chrping at the passengers. That is a little more amusing than usual. I hope he/she gets out ok.

Added after 40 minutes:

I saw several citations on the ieee site (Xplore) on the subject of microstrip to waveguide transitions. You might see if any of them are helpful.

I happen to be sitting in an airport waiting lounge. There is a sparrow flying around and chrping at the passengers. That is a little more amusing than usual. I hope he/she gets out ok.
 

Azulykit

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Ody,

Take a look at this article:

h**p://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19870007525_1987007525.pdf

It looked interesting.

Azulykit
 

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