High selectivity tunable filtering power divider based on liquid crystal technology for microwave applications

Abstract

A novel electrically tunable filtering power divider, based on liquid crystal (LC) technology, is designed and experimentally demonstrated in this paper. Using low-cost T-shaped inverted-microstrip structures integrated with two dual-mode open-loop resonators, the tunable power divider possesses bandpass-filtering frequency response. Moreover, transitions between inverted-microstrip and microstrip structures are specifically designed at the I/O ports for the self-packaged. The experimental results indicate that the central frequency can be tuned from 5.75 to 6.25 GHz, i.e. a relative tuning range of 8.3%, the 3-dB bandwidth is 6.8 ± 0.2% over the whole tuning range, and the maximum amplitude and phase imbalance are less than 0.8 dB and 2.5°, respectively. In addition, the proposed filtering power divider has three transmission zeros to improve the frequency selectivity.

Keywords:

• Liquid crystal
• bandpass-response
• tunable power divider
• high-frequency selectivity
• inverted-microstrip structures