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Two novel second-order dual-band bandpass filters (BPFs) with high isolation and high selectivity using coupled lines are realised with a T-shaped bandstop structure. The centre frequencies of the two dual-band BPFs can be adjusted to the desired values by changing the coupling coefficients and characteristic impedances of the two transmission paths. Two dual-band BPFs located at 1.87 and 2.53 GHz and 1.9 and 2.42 GHz are designed and fabricated for demonstration. Good agreements can be observed between simulated and measured performances. [ABSTRACT FROM PUBLISHER]

A compact tri-band bandpass filter using input/output cross coupling is proposed. Three passbands can be adjusted by changing the characteristic impedance of the T-shaped structure with a shorted stub. The three passbands are designed to operate at 1.85, 3.5 and 5.2 GHz based on the T-shaped structure. Four transmission zeros are used to realise high selectivity for the passbands. Good agreement can be observed between the measured and simulated results. [ABSTRACT FROM AUTHOR]