Via-Hole Arrangement for Bandwidth Extension of Planar Microstrip-to-Waveguide Transition

A novel design technique for bandwidth extension of microstrip-to-waveguide transition with a simple via-hole arrangement surrounding waveguide is proposed. The proposed transition can be operated over a quite broad frequency bandwidth of
$\mathbf{10, GHz}, (\pmb{S}_{11} < -15, \mathbf{dB})$
due to its double resonance.