Amongst the contemporary gap waveguide structures, both ridge gap waveguide (RGW) and groove gap waveguide (GGWG) display low losses and are resistant to signal leakage without the requirement of electrical contacts. In both scenarios, the concept is to allow the wave propagation through the guiding part and eliminating signal leakage in all other directions. Since, at present, millimeter-wave (mm-wave) has gained attention due to its versatile usability at high-frequency applications, it is quite obligatory to develop components with superior electrical features, like high stability, wider bandwidth, as well as high power handling capability at that frequency range. Considering the stated advantages, the proposed devices in this research work emphases on the mm-wave application that are mainly accountable for connecting standard waveguides and feeding antenna systems.
The research work can be summarized in three segments. The first segment aims at designing waveguide adaptors based on the gap waveguide technology that do not necessarily require perfect electrical contact. The contact-free adaptor has been designed for both standard rectangular and circular waveguides covering multiple mm-wave frequency bands within 50- 110 GHz. Additionally, while designing the adaptor, surface roughness has been considered to achieve the response of the structure close enough to the practical case. The same adapter can also be used with different standard waveguide dimensions operating within 50-110 GHz by changing the adapter’s waveguide parameters. The proposed contact-free adaptor exhibits an excellent return loss and insertion loss of better than 20 dB and 0.3 dB, respectively, for both standard circular and rectangular waveguides, regardless of a smooth or uneven surface.
The second segment focuses on a contact-free flangeless pipe connection for both circular and rectangular standard waveguides, covering multiple frequency bands amid 50 and 110 GHz. The contactless, low-loss, flange-free, and pluggable contact aims at joining two slightly modified standard waveguides, along with a 60% downscaling of the recommended structure compared to the traditional UG-387/U waveguide flange, hence demonstrating a reflection coefficient better than -20 dB in each scenario.
In addition, the third segment is introducing microwave devices that can combine and separate two propagating polarizations, such as orthomode transducers (OMT). Aiming for high power applications with compact structure, the proposed configuration introduces a new design procedure of combining the ridge gap and groove gap waveguides for the OMTs, validating an acceptable matching level of better than -18 dB along with isolation higher than 70 dB.
Finally, some valuable recommendations as an extension of this research work are suggested in the final chapter
