Dissipative Analysis of Liquid Crystal-loaded Passive Reconfigurable Transmission Line Components with Filled Vias at 60 GHz

Due to its distinct electromagnetic properties with dielectric anisotropy, liquid crystal technology is a viable option for reconfigurable microwave and millimeter-wave components. While 0-180° and 0-360° phase tuning have been evidenced in our past prototypes, this research focuses on the effect of vias' heights on the loss characteristics at 60 GHz. A reconfigurable passive inverted microstrip line loaded with liquid crystals is modelled, featuring interfaced with external connectors by top-launch microstrip lines and plated-through-hole copper-filled vias that connect the top and bottom metal layers. Power dissipative analysis reveals that as the vias' height increases from 0.04 guided wavelength to 0.25 guided wavelength, radiation loss rises from 22.12% to 45.74% of the input power, and return loss increases from 8.51% to 19.01%, i.e., jointly and negatively impact the forward transmission that declines from 34.67% to 9.46%. Interestingly, copper loss and liquid crystal loss are declining with the rise of the vias' height.