Novel Dual-Band Bandpass Filter and Reconfigurable Filters Using Lumped-Element Dual-Resonance Resonators

In this paper, a lumped-element dual-resonance resonator (LE-DRR) is proposed to design dual-band bandpass filter (DB-BPF) and reconfigurable filters. Two resonant modes of proposed LE-DRR are controlled by two diverse branches. The mixed electric and magnetic coupling (MEMC) implemented by two capacitors to provide electric coupling and one inductor to provide magnetic coupling is employed in the LE-DRR filters design. As an example, a 0.9/1.57-GHz DB-BPF with 3-dB fractional bandwidth (FBW) of 22.2%/11.8% is designed firstly. A reconfigurable DB-BPF with two independently controlled passbands is then designed. The measured results show that the central frequency (CF) of the 1st passband can be tuned from 0.617 to 0.817 GHz, and the CF of the 2nd passband can be tuned from 1.386 to 2.02 GHz. Finally, a multi-function reconfigurable filter is proposed by introducing two pairs of p-i-n diodes in the reconfigurable DB-BPF. The proposed multi-function reconfigurable filter has four operating modes, i.e., a reconfigurable DB-BPF operating mode, an all-stop filter operating mode, and two single-band tunable BPF operating modes. The all-stop filter operating mode has a 10.2-dB rejection within the interested frequency range. The CFs of two single-band tunable BPF operating modes can cover a continuous frequency range from 0.56 to 1.619 GHz. The proposed LE-DRR filters are compatible with an integrated circuit process.