Compact Multi-Function Notch Filter Using λ/4 Microstrip Resonator with Embedded Varactor-Loaded Hybrid Microstrip/CPW Structure

In this paper, a multi-function dual-band notch filter using λ/4 microstrip resonator with embedded varactor-loaded hybrid microstrip and coplanar waveguide (CPW) structure is presented. λ/4 microstrip resonators and CPWs under them are utilized to allocate the lower and upper notches, respectively. Varactors, trimmer capacitors, and PIN diodes are added for tuning functions. To verify the mechanism mentioned above, a compact multi-function dual-band notch filter is fabricated and measured. The tuning range of the lower and upper bands are 1.2-1.9 GHz and 2.1-2.2 GHz, respectively. Meanwhile, maximum 30 dB attenuation range is measured.