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.
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Update:
yesterday i found some advantages/disadvantages in literature of circular waveguides, but i dont know if i can translate these into cavity resonators:
advantages:
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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 -
in circular waveguide, TM01 and TE01 modes are rotationally symmetrical and hence rotation of polarization could be overcome.
–> why is this an advantage? - the circular waveguides are easier to manufacture and join than rectangular waveguides.
disadvantages:
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propagation in rectangular waveguide is easier compared to circular waveguide.
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circular waveguide occupies more space compared to rectangular waveguide system.
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due to infinite number of modes existing in a circular waveguide, it becomes very difficult to separate these modes.
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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?
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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.
Best Answer
Maybe a rectangular microwave oven has the same simple advantage as rectangular furniture: rooms are usually rectangular, and any other shape of furniture would use the space less efficiently.