Fully Tunable Bandpass Filter With Wide Bandwidth Tuning Range and Switchable Single/Dual Band

In this paper, a fully tunable bandpass filter (BPF) with three states of filtering (single passband state, dual passband state and all-off state) is proposed, the proposed fully tunable BPF is cascaded by a tunable low pass filter section (LP) and a tunable high pass filter section(HP). By introducing a switchable dual-mode notch in the passband, the proposed BPF is capable of operating in single, dual passband and all-off state, demonstrating high flexibility in working mode. Tunable LP and HP filters with 7-order generalized Chebyshev response are designed to improve the roll-off rate and out-of-band rejection level of the BPF. The measured results show that the bandwidth of the BPF can be tuned from 0.25GHz to 2.69GHz (10.8:1), and the center frequency can be tuned from 2.9GHz to 4.6GHz with constant absolute bandwidth of 1GHz. Besides, high rejection level of out-of-band is realized in all working mode. The high flexibility in working mode makes the proposed fully tunable BPF very attractive in carrier aggregation scenarios.