Dual-band bandpass filters with high isolation using coupled lines

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.