Compact tunable UHF bandstop resonator filter using varactor-loaded CPW bottom-side meander line

This paper presents a novel tunable coplanar waveguide bottom-side meander line bandstop resonator filter. The proposed topology consists of modifying the electrical length of the meander line by tuning loaded varactors. As the reverse bias voltage is changed from 0 to 20 V, the resonance frequency is tuned from 0.51 GHz to 1.76 GHz, resulting in a very high tuning of 245%. Additionally, the proposed ultra high frequency (UHF) filter features a compact size of 4 × 9 mm². Measurements of the fabricated filter are in very good agreement with simulated results.