This paper presents for the first time a fully electronically reconfigurable waveguide filter tunable in bandwidth and center frequency based on liquid crystal (LC) technology. A continuously reconfigurable two pole bandpass filter is designed and characterized in the Ka-band at 30 GHz. To be able to tune both center frequency and bandwidth independently, the resonators and coupling structures are filled with LC as tunable material. Hence, the filter's center frequency and coupling strengths can be tuned and, furthermore, tuning with constant filter characteristic is possible. To tune the LC, a novel two-layer electrode design for waveguide structures is presented, which is simple to integrate and provides a high tuning efficiency with low insertion loss. By applying different bias configurations, the LC's effective permittivity can be varied, and therefore, also the resonators' electrical lengths. The presented two pole filter can adapt its center frequency from 29.8 GHz to 30.7 GHz with a maximum 3 dB bandwidth variation from 660 MHz to 870 MHz. The measurements are carried out with bias voltages up to ±250 V.INDEX TERMS Microwave filter, liquid crystals, millimeter wave communication, tunable circuits and devices, K-band.This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination.
This work presents the development of an X-band twisted metal-insert bandpass filter as a monolithic 3D-printed structure. The component serves as a compact solution for the incorporation of a fourth-order bandpass filter response while simultaneously rotating the polarization by 90 degrees as a twist-component. The structure is fabricated using lowcost stereolithography 3D-printing and metallized using a simple copper electroplating method. The measured results exhibit an unloaded Q-factor of approximately 2600 and have an insertion loss better then 0.44 dB throughout the passband, ultimately demonstrating a unique use of the metal-insert filter technique and providing a novel presentation on integrated monolithic structures.
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