Cross-coupled microstrip bandpass filter using folded tapered-line resonators

The design of a cross-coupled microstrip bandpass filter using folded tapered-line resonators is presented. The network analysis model of a single folded tapered-line resonator is described. Its singly loaded quality factor and mutual couplings between two resonators are also discussed. A bandpass filter at 2.4 GHz and with a 60 MHz bandwidth is then designed and fabricated using this kind of resonators. Measurement results are given showing that two transmission zeros are created at both sides of the passband, and thus result in very high passband selectivity.