Design and fabrication of meta-resonator based multifunctional waveguide filter using stereolithography (SLA) additive manufacturing method

Microwave filters are widely used in many fields due to their high power capability and low loss advantages. However, the large electrical size of conventional DC filters at certain frequencies poses a problem in terms of miniaturization. Recently, as an alternative to conventional methods, up to a 75% reduction in physical size can be achieved by embedding metamaterials in the waveguide. A review of the literature shows that DC filters are either bandpass or band-stop, have only a fixed operating frequency, and are configured to operate at a single frequency. In this thesis, the research topic and objective are to design a multi-functional DC filter using CSRR/SRR structures with switchable degrees that provide sufficient performance in C-band (4.90-7.05 GHz), are relatively smaller, lighter, and low-cost, and to present them comparatively with alternative fabrication methods. The DC structure proposed within the scope of the thesis was produced both with CNC milling technology and stereolithography (SLA), which is an additive manufacturing technology, and the DC structure produced with SLA was coated with metal material on the entire surface to guide the EM wave. The CSRR meta-resonator structures tested up to this stage were fabricated by LPFC using RT/Duroid 5880 substrate, and the CNC and SLA methods were compared with each other and with the simulation results. The frequency responses of the CNC fabricated DC filters are very close to the simulation results, while the frequency responses of the DC filters fabricated with SLA technology and then metal-coated are partially worse than the simulation results. In this study, a DK filter was designed, fabricated, and tested using CSRR bandpass, SRR bandstop filters with rectangular, ring, and crescent geometries, and a meta-resonator with a unique geometry not available in the literature.