Why are rectangular cavities preferred for standard microwave ovens with a frequency of 2.45 Ghz? What is the reason that you can hardly find a circular cavity? What are the disadvantages of cylindrical cavities? Are there any advantages?

My assumption is that the radius of a cylindrical cavity would be bigger than the largest side of a rectangular cavity so that the dominant mode can propagate. Maybe the mode propagation in cylindrical ovens is not that good to get a more uniform field distribution and therefore even heating. Are there also reasons of manufacturing? Any reference to a paper or book is very appreciated.

Thank you very much in advance!

Best regards


================================================================== Update:

yesterday i found some advantages/disadvantages in literature of circular waveguides, but i dont know if i can translate these into cavity resonators:


  1. TE01 mode in circular waveguide has the lowest attenuation per unit length of waveguide hence suitable for distance waveguide transmission. --> since microwave ovens dont want to transfer anything over long distance i think this is negligible

  2. in circular waveguide, TM01 and TE01 modes are rotationally symmetrical and hence rotation of polarization could be overcome. --> why is this an advantage?

  3. the circular waveguides are easier to manufacture and join than rectangular waveguides.


  1. propagation in rectangular waveguide is easier compared to circular waveguide.

  2. circular waveguide occupies more space compared to rectangular waveguide system.

  3. due to infinite number of modes existing in a circular waveguide, it becomes very difficult to separate these modes.

  4. angle of polarization of wave changes because of discontinuities and even small irregularities, as a result of which coupling energy out of waveguide at receiving end becomes difficult. --> is this what you mean @CuriousOne? but why is this a bad thing?

  5. Fabrication of certain type components is more difficult for circular waveguide

Maybe someone with a better understanding of microwaves can briefly explain what (dis-) advantages would be relevant for microwave oven cavities.

Thank you very much in adance!

  • $\begingroup$ Good question. I would think that it has to do with the ability of a rectangular waveguide to keep the polarization of the wave well defined even when it is bent. $\endgroup$ – CuriousOne May 20 '16 at 22:26

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