A miniaturized electrically tunable dual‐mode bandpass filter based on liquid crystal technology for microwave applications

In this letter, a miniaturized electrically tunable bandpass filter, based on liquid crystal (LC) technology, has been designed, manufactured and characterized through particular configuration schemes, which include low cost inverted‐microstrip structures and a dual‐mode inverted‐microstrip square loop resonator with capacitively loaded open‐loop arms. In the filter, its transitions between inverted‐microstrip and microstrip are specifically designed at the I/O ports for the self‐packaged, and its central frequency tenability is induced by applying low AC voltages for low power consumption. By measuring, the filter has a relative central frequency tuning range of 11.7% from 4.01 GHz to 4.51 GHz, and has a relative bandwidth of 13% ± 0.5% over the tuning range, a size of 28 mm × 28 mm, and an insertion loss of 1.9 and 4.5 dB at 4.01 and 4.51 GHz, respectively. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1686–1689, 2016