is it easy to design a air stub combline filter at KU band?

[hakunamatata]

combline filter with iris

the stub is very short (nearly 3mm) at ku band. that means the filter is very sensitive to fabricate. did anyone design the combline filter at this band?
maybe we can talk about it.

 

[sergio mariotti]

air stub

The mechanical design is not easy.
take in consideration the cost of design, fabrication, test, step back and reverse eng. , manpower etc. and compare with the cost if you buy a filter from a higly experienced factory.

 

[sinatra]

Re: is it easy to design a air stub combline filter at KU ba

Hello hakunamatata.
Do you want to make a band-pass filter.
If so, I propose you to use microstrip technology. Depending on the substrate you should at those frequencies (Ku band = 12-18GHz) it is still possible to make good filter with microstrip.
I would propose that you build an end-coupled half-wavelengh microstrip band-pass filter.
S.

 

[biff44]

Re: is it easy to design a air stub combline filter at KU ba

Starting at perhaps 14 GHz and higher, the most economical filters are the waveguide λ/2-iris coupled filters. The iris can be a partial wall, or some rods from top to bottom, or whatever.

You can tell that these are the mose economical filters because all of the point to point communications vendors (Endwave, Harris, DMC-stratex, etc) use this technology, and if there were a cheaper acceptable technology they would be using it instead.

There are important processes required to fabricate these filters, related to brazing, plating, etc., and they are somewhat involved and easily screwed up. If you mess up the processes, the filter has an extra 3 dB loss that you can not get rid of.

 

[hakunamatata]

Re: is it easy to design a air stub combline filter at KU ba

biff44:
u are right, I am considering designing waveguide iris filter working at KU band. Microstrip filter can also be used but the insert loss is bigger than waveguide filter.
but I want take the SMA into the total structure . I donnt know how difficult to design the waveguide filter with SMA . could anyone tell me about this

 

[sinatra]

Re: is it easy to design a air stub combline filter at KU ba

Please guys.
Could you post a link or any information where I could see this type of filter: waveguide λ/2-iris coupled filters.

This is the first time that I hear about it. Maybe i know it but with another name....I would like to check it...

S.

 

[biff44]

Re: is it easy to design a air stub combline filter at KU ba

**broken link removed**

Added after 7 minutes:

Do yourself a favor, buy one of these, take it over to a bandsaw, and learn!

**broken link removed**

**broken link removed**

They are "diplexer" filters, ie two waveguide bandpasses fed from a common junction.