The mode extractor converts a fundamental TE10 mode in a rectangular waveguide into a TE21 in a circular waveguide.
This example is based on "Polarization-controllable TE21 mode converter", in REVIEW OF SCIENTIFIC INSTRUMENTS 76, 074703 (2005), by T. H. Chang, C. F. Yu, and C. T. Fan.
The geometry (this is an advanced example and it may take too much time to describe all the steps required for this geometry) :
In pink :
rectangular TE10 to circular TE11 transition
In blue :
rectangular TE10 to circular TE21 transition
In yellow :
radiating horn antenna.
Half of the geometry was generated in order to take a H symmetry plane into account :
First case : the rectangular TE10 to circular TE11 transition is fed.
To activate this feed select "rectangular" in its description. Don't forget to deselect all the check boxes in the other feed to deactivate it.
The computed currents and electric near field show that most of the power goes to the radiating horn an not the other rectangular waveguide.
Surface currents :
Electric near field :
Far field :
Second case : the rectangular TE10 to circular TE21 transition is fed.
To activate this feed select "rectangular" in its description. Don't forget to deselect all the check boxes in the other feed to deactivate it.
As in the previous case, most of the power is directed to the radiating horn. In addition, the near field and the far field show that the radiated mode is a circular TE21 mode (a zero in the main axis and 4 lobes).
Surface currents :
Electric near field :
Far field :
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