T-junction Circular to Sidecoupled Rectangular Waveguide

Model

The geometry of a T-junction circular to sidecoupled rectangular waveguide with large aperture is shown in the first figure. It is another important waveguide key-building block which can be found in many applications such as turnstile junctions, filters, couplers, and orthomode transducers. The input and output ports are modeled using Rectangular Waveguide and Circular Waveguide tools respectively.

Simulation

The fundamental modes (rectangular TE₁₀ and circular TE₁₁) are excited at the input and output ports respectively. Two broadband simulations which are automatically built by using the template simulation are run to cover the frequency range between 13.0 GHz and 17.0 GHz. The UPML absorbing and PEC boundary conditions are used to truncate the computational domain.

Results

The three-port S-matrix of the junction is obtained with the help of S-parameter Evaluation tool. Figure in the middle presents the computed scattering parameters in the frequency range of interest. E-field patterns on different cross-sections are shown in the last figure which illustrates the transition between rectangular and circular waveguide modes.