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A novel dual-wideband bandpass filter with controllable bandwidths is presented in this article. Two passbands for the WLAN band are realised based on a multimode resonator with three open stubs. The bandwidth of the two-order passbands with even or odd mode can be adjusted by appropriately selecting the characteristic impedance of the multimode resonator. A planar microstrip dual-wideband bandpass filter prototype with a 3-dB fractional bandwidth of 16.7% and 9.2% is designed and fabricated. High selectivity and good in-band performance can be achieved in the dual-wideband bandpass filter. [ABSTRACT FROM AUTHOR]

Two high selectivity wideband filtering crossovers using stub-loaded ring resonators are proposed in this paper. Cascaded coupled lines and open stubs are used to generate two/four transmission zeros each near the crossover passbands. In addition, patterned grounded conductor in the ground plane can enlarge the coupling coefficient for the coupled lines with increasing the even-mode characteristic impedance, and the isolated conductor placed inside the slot can decrease the odd-mode characteristic impedance. Two filtering crossovers operated at 2.2 GHz with bandwidths of 27.5% from 1.945 to 2.55 GHz are designed and fabricated. They show good return loss more than 20 dB and nice insertion loss less than 1.7 dB in passband. [ABSTRACT FROM PUBLISHER]

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]

This study presents an low-temperature cofired ceramic (LTCC) V-band cross-coupled band-pass filter using substrate-integrated waveguide cavities. Two antisymmetric U-shaped slots connected by via is proposed to construct the negative coupling structure, which is simple and especially useful for 60 GHz applications. Moreover, the U-slot structure possesses a wide range of realizable coupling coefficients from −0.008 to −0.075. An experimental LTCC fourth-order filter was fabricated for demonstration, achieving a bandwidth of 12% (7.2 GHz) at 59.6 GHz with superior frequency selectivity. [ABSTRACT FROM AUTHOR]