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In this work, the feasibility of microwave liquid crystal based dielectric waveguide phased shifters is investigated in a phased rod antenna array for the first time. For this, a 1 × 4 rod antenna array is designed including the phase shifters as well as a cascaded E-plane power divider network. As core elements, the phase shifter are designed as continuously tunable subwavelength fibers, partially filled with a newly specifically synthesized microwave liquid crystal, exhibiting a maximum FoM 145 • /dB at 102.5 GHz. As proof-of-concept, a simplified electric biasing network is developed, demonstrating its beam steering capability by changing the scanning angle between 0 • , −25 • and +15 • with three different voltage distributions. The antenna array is well matched throughout the complete W-band with a input reflection below −10 dB. The measured antenna gain is between 11.5 to 9.1 dBi at 85 GHz accompanied with a side lobe level between −12 to −7 dB, depending on the steering configuration.INDEX TERMS Phased array, millimeter wave devices, microwave liquid crystal, dielectric waveguide.

In the field of oxide electronics, there has been tremendous progress in the recent years in atomic engineering of functional oxide thin films with controlled interfaces at the unit cell level. However, some relevant devices such as tunable ferroelectric microwave capacitors (varactors) based on BaxSr1−xTiO3 are stymied by the absence of suited compatible, very low resistive oxide electrode materials on the micrometer scale. Therefore, we start with the epitaxial growth of the exceptionally highly conducting isostructural perovskite SrMoO3 having a higher room-temperature conductivity than Pt. In high-frequency applications such as tunable filters and antennas, the desired electrode thickness is determined by the electromagnetic skin depth, which is of the order of several micrometers in the frequency range of a few gigahertz. Here, we report the pulsed laser deposition of a fully layer-by-layer grown epitaxial device stack, combining a several micrometers thick electrode of SrMoO3 with atomically engineered sharp interfaces to the substrate and to the subsequently grown functional dielectric layer. The difficult to achieve epitaxial thick film growth makes use of the extraordinary ability of perovskites to accommodate strain well beyond the critical thickness limit by adjusting their lattice constant with small shifts in the cation ratio, tuned by deposition parameters. We show that our approach, encompassing several orders of magnitude in film thickness scale whilst maintaining atomic layer control, enables the fabrication of metal-insulator-metal (MIM) varactors based on 50–100 nm thin BaxSr1−xTiO3 layers with high tunability above three at the Li-ion battery voltage level (3.7 V).

Tunable Liquid Crystal (LC)-based microwave components are of increasing interest in academia and industry. Based on these components, numerous applications can be targeted such as tunable microwave filters and beam-steering antenna systems. With the commercialization of first LC-steered antennas for Ku-band e.g., by Kymeta and Alcan Systems, LC-based microwave components left early research stages behind. With the introduction of terrestrial 5G communications systems, moving to millimeter-wave communication, these systems can benefit from the unique properties of LC in terms of material quality. In this paper, we show recent developments in millimeter wave phase shifters for antenna arrays. The limits of classical high-performance metallic rectangular waveguides are clearly identified. A new implementation with dielectric waveguides is presented and compared to classic approaches.

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