A novel cylindrical TE2,1 mode converter

A novel, compact arrangement for Ka-band mode couplers, which convert a rectangular waveguide TE1,0 to cylindrical waveguide TE2,1 mode, has been designed, constructed, and tested. The design features a set of longitudinal slots, positioned in regions of negligible current flow for the TE2,1 mode, allowing its propagation to be preferentially favored, by suppression of the fundamental TE1,1 mode. Numerical simulations and experimental measurements display good agreement, showing transmission of the intended TE2,1 mode at levels of better than -5 dB, from a frequency of similar to 37.5 to 41 GHz. Subsequent farfield measurements confirm the presence of the TE2,1 mode, demonstrating good agreement when compared with analytical expectations. Such a device would be an ideal candidate for an application where mode purity, bandwidth, and ease of construction are of primary importance and where the transmission efficiency is of limited concern. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3480994]