Coaxial probe to rectangular waveguide

[yasine79]

Hi!
I have a question about the Transition:coaxial probe to rectangular waveguide.

I saw some waveguide with acoaxial probe. zhis coaxial probe is loaded with a small cylinder or disc. i dont know the rason. mybe you could help me! i thought about the matching!

how long (in wave length) should the probe be?

Is it the same coupling way with coaxial- cylindrical wave guide?

thank you!

 

[chameleon]

They have effects on impedance matching, but they are not crucial. Just sticking the inner conductor of the coax into the rectangular waveguide can still provide you less than -10dB S11. According to my experiences the center pin should go slightly more than half the height of the rectangular waveguide. The distance to back wall is also important. You can do a parameter sweep for both dimensions to have a good matching.

 

[yasine79]

thank you for reply.
do you have or know some literature about this?
do you have any idea where i could buy such a probe? (TE01 rectangular wG in (2-5GHz))

Thank you

 

[chameleon]

There are standard waveguide sizes coded with WR prefixes (for instance WR90 for xband, i.e. 8.2-12.4GHz). I don't know if you already have a fixed waveguide dimension. If not, you can go with WR340 (it is given as 2.2GHz to 3.3GHz (for single mode operation), but is has a margin on the low end and can support above frequencies (note that single mode operation is not guaranteed for above frequencies). The following link has coax to waveguide adapters:

**broken link removed**

If you search for coax to waveguide adapters you can find many vendors like this one. For this one VSWR is given as 1.25 in the frequency of operation and you should check the performance for other frequencies.

You can refer to Collin's Field Theory and Guided Waves for more information about waveguide excitation etc.