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why multiple modes in rectangular cavity when it is coupling?
Posted Feb 12, 2020, 5:14 a.m. EST 1 Reply
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When i am performing a simulation of 1 cm radius cylindrical cavity with comsol multiphysics, the obtained frequency eigen value for TM010 mode is 11.47GHz. But when I am adding the coupling structures ( coaxial cable) it get excited at two modes, one mode is around 10 GHz and other mode is around 12GHz.
Why this is happening?
simulation results are attached here: simulation results
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You changed the geometry by adding the structures and thus introduced new possible modes and/or new boundary conditions. The eigenmodes and eigenfrequencies of any system that exhibits oscillations, whether it is an RF cavity, an antenna, a swinging pendulum, a mass on a spring, a vibrating quartz cystal, etc., are not independent of the structures and/or environments that couple to them, unless those couplings are made weak enough that they can be neglected.
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