Broadband Dielectric-to-Half-Mode Air-Filled Substrate Integrated Waveguide Transition

This letter reports a broadband transition from dielectric-filled substrate integrated waveguide (DFSIW) to half mode air-filled substrate integrated waveguide (HM-AFSIW). The HM-AFSIW, demonstrated for the first time, is based on a multilayer printed circuit board (PCB) topology. Its fabrication involves three layers. The top and bottom substrates can make use of a low-cost standard substrate such as FR4. For our demonstration purpose, a back-to-back transition implementing a 10 mm-long HM-AFSIW operating over the entire
$Ka$
-band is fabricated. It achieves measured return loss of better than
$-$
15.9 dB and insertion loss of 0.79
$\pm$
0.25 dB (0.3
$\pm$
0.15 dB for the transition) from 26 to 40 GHz. This transition is of interest for interconnecting dielectric-loss-free components based on HM-AFSIW including, for example, leaky wave antennas.