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Abstract-In this paper, a miniature ultrawideband (UWB) bandpass filter with dual notch bands and wide upper stopband is presented. The ultrawide passband characteristic is achieved using a microstrip to slot line transition, and a wide upper stop band is realized using an elliptical lowpass filter. The dual band notches at 5.46 GHz and 8.04 GHz are obtained by incorporating defected microstrip structure in the input and output sections. A prototype of the proposed UWB bandpass filter is fabricated and measured. The equivalent circuit of the proposed filter is also presented. A good agreement between the measured, EM simulated and circuit simulated responses is obtained.

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A new class of switchable bandpass filter using PIN diodes is presented in this paper. The design aims at achieving a multistate switchable bandpass filtering characteristics between the passbands centered at 2.4, 3.5, and 5.2 GHz. The proposed filter is designed by assembling two λg/2 open-ended and four short-ended λg/4 uniform impedance resonators. The open-ended resonator generates a fixed passband at 3.5 GHz, whereas the short-ended resonators loaded with PIN diodes are independently controlling the ON and OFF characteristics of the passband centered at 2.4 and 5.2 GHz. The transmission zeros around each passband are produced without employing any additional circuit. The filter sample is fabricated and tested for experimental verification. A good agreement has been observed between EM-simulated and measured results. The designed filter has a compact size of 0.20 λg × 0.15 λg at 2.4 GHz.

In this article, a dual‐band bandpass filter is proposed using two half wave length open loop resonators integrated in concentric topology. The outer set of resonators are realized to operate at lower pass band of 2.4 GHz which is coupled directly to input and output ports where as the inner set of resonators are designed at 3.5 GHz which is electromagnetically coupled to the outer resonator. To obtain wide passbands, enhanced coupling between the outer resonators is realized using ground slots just below the open loop sections of the resonators. The measured passband bandwidth at 2.45 and 3.5 GHz is 187 and 155 MHz respectively. Four transmission zeros, created due to source load coupling, are located close to the passband edges at 2.18, 2.68, 3.38, and 3.72 GHz to increase skirt selectivity. Over all filter dimension is 20 mm by 32 mm. An equivalent circuit model is developed that is in close agreement with full wave simulation and measured results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2049–2052, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26991