Quasi‐elliptical band‐pass filters based on compact spiral resonators for C‐band applications

This letter proposes a quasi-elliptical passband filter invia-less microstrip technology. The filter is based on theArchimedean spiral, enabling a compact and low-lossresponse with sharp transitions to stop bands. The developedfilters fabricated on a commercial substrate, present lossesbelow 2 dB within a 3 dB bandwidth of 500 MHz, and iso-lation exceeding 20 dB. Its extremely compact dimension,about 0,018λ^2, and the low-cost of fabrication, permitsthe integration within compact front-end PCB.