Cut off frequency of Circular Waveguide

[ping-pong]

circular waveguide cutoff frequency

Hi,

Can somebody tell me the specific formula to calculate the cutoff frequency of circular waveguide. What will be the radius of circular waveguide if it is to operated at 8.2 GHz. Can u provide the literature or link from where I can get some useful information about this. Waiting an early reply.

 

[VSWR]

cutoff frequency circular waveguide

For these kind of questions it's very easy to do a search via Google (www.google.com). Enter keywords 'cutoff frequency circular waveguide' and press Enter.

You will get several hits, such as

https://www.rfcafe.com/references/electrical/waveguide.htm

 

[borich_03]

Very good book for you is a "Microwave Engineering" by Pozar,second edition, charter 3.

 

[willaceee]

I recently designed a coke can wave guide(cavity). Remember that the higher the frequency the smaller the wave guide will be! Here are the formulas I used to calculate it:
1) Use the link that is in the above post to get your p'nm and pnm values for the mode you want.
2) KC= (p'nm or pnm)/radius (in) Raduis must be in inches
3) lamda g = length of waveguide * wavelength (1/2 for 1/2 of a wave cycle)
4) B=((2*pi)/lamda g)
5) KC^2+B^2=K^2
Solve For K
6) f=(K*C(11.81 GHz-in))/(2*pi)

You should be able to calculate the size of your waveguide by going reverse. For a raduis of 1.3in and a length of 4.5in I calculated 3-5 GHz for the lowest modes (less interference if you calculate TE11 or TM01 modes) . So for your application you are going to need something smaller in diameter and the height you may want to play with. According to Pozar the cut off frequency is
fc=p'nm/(2*pi*raduis*sqrt(ue)). I hope that all this helps! Willaceee 8) 8)