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Half-mode substrate integrated waveguide (HMSIW) switchable unit, built by HMSIW section with loaded single or multi-microstrip shunt stub(s), was proposed in this work. Both shorted and opened stubs were studied, investigated and compared, bandwidth enhancement method for proposed switchable units was proposed and demonstrated. Based on these switchable units, narrowband and broadband HMSIW single-pole-single-through (SPST) switches, SIW SPST switch and SIW/HMSIW-based single-pole-double-through (SPDT) switch were designed, fabricated and measured. Good performances were observed experimentally for these proposed circuits, showing the advantages of proposed concept and an excellent candidate for switchable or reconfigurable SIW/HMSIW circuits or systems. [ABSTRACT FROM AUTHOR]

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]

This article presents a compact microstrip dual-band bandstop filter (BSF), in which one λg/4 defected ground structure (DGS) pair is utilised to realise one stopband while two stepped impedance resonators (SIRs) help obtain another stopband and suppress the spurious harmonics. The design strategies and the equivalent circuits are introduced in detail. The measured results indicate 43.8% and 18.7% fractional bandwidth in the two stopbands (2.4 GHZ and 5.2 GHz) respectively, and the return loss is greater than 15 dB in the whole passband. In addition, size reduction can be conveniently achieved by adjusting the length of the SIRs and DGS. [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]