# How to design a 915 MHz waveguide circulator?

I would like to design a waveguide circulator. I tried to design one but, my attempt was not successful. My design used a cylindrical cavity with ferrite as region. I then connected 3 waveguides in 0,120 and -120 directions. Upon applying the excitation, I got a pathetic result. I have referred to some more resources but can not resolve this problem. Has anybody tried this before?

My design and its parameters are shown below

• Frequency of operation: 915 MHz
• Dielectric permittivity of material(ferrite): 14.2
• The height of cylinder: 5.5 mm
• Radius of cylinder 30 mm
• The waveguide cross section a = 20 mm
• The waveguide cross section b = 2.5 mm
• The length of waveguide l = 50 mm
• Hi Sumith, to assist those who might be able to answer your question it would be helpful if you could provide links to the references you mention in your question
– Fred
Apr 20 '15 at 6:05
• They are some whitepapers. I can't disclose them. Sorry for that. But I can add my design with parameters I have used. Could you please wait for little time? Apr 20 '15 at 6:22
• A waveguide with such tiny dimensions is going to have a lower cutoff frequency on the order of 10 GHz or so. See this table. Why do you think it would be effective at 915 MHz? In any case, you'd probably get a more thorough answer on this on EE.SE. Apr 20 '15 at 11:35
• @DaveTweed, Sir, you are right. I calculated the same again. For 915MHz, the cross section 'a' should be more than 16cm. However I like to know how I can construct circulator with waveguides. Thank you. Apr 21 '15 at 6:22