Abstract-In this paper, a simple method and structure to design a dual-band bandpass filter (BPF) by using a dual feeding structure and embedded uniform impedance resonator (UIR) is presented. In this structure, two passbands can be designed individually and several transmission zeros can be created to improve the band selectivity and stopband performance. The first passband is determined by the dual feeding structure and the second passband is determined by the UIR. Moreover, by using the inter coupling in the UIR, the performance of the second passband can be easily tuned without degrading the first passband. In order to verify the design concept, two filter

Abstract-In this paper, design and fabrication of a quadband microstrip bandpass filter (BPF) using multi-layered stepped impedance resonators (SIRs) structure is proposed. One pair of SIR on the top layer is designed to operate at the 1st and 3rd passbands (1.56/3.57 GHz), and the other pair is at 2nd and 4th passbands (2.42/5.23 GHz) by tuning the impedance and length ratios of the SIRs. In order to find the desired coupling location between the SIRs located on different layers and the input/output (I/O) lines, the voltage, current and power wave on the I/O lines are analyzed. It is verified that the proposed quad-band filter has good passband performances with an excellent isolation between adjacent bands for GPS, WLAN, and WiMAX applications.

Abstract-This paper proposes a novel compact dual-band bandpass filter (BPF) using four spiral resonators for application in GSM and IEEE 802.11b WLANs for the first time. Since the two passbands can be tuned individually, the filter has more design freedoms. The symmetry coupling structure is realized to achieve a isolation higher than 30 dB between the lower and higher passbands. The full-wave simulator IE3D is used to design the spiral resonators and calculate the coupling coefficients of the basic coupling structures. The designed BPF is fabricated and measured. Good agreement between the simulated and measured results verifies our design concept.

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This article presents a new design of wideband spurious suppression of dual‐mode band‐pass filter (BPF) using defected cascaded resonators (DCRs).The pattern of the DCRs is similar with that of the conventional low‐pass stepped impedance resonator, whereas it is etched in the ground. It is verified that adding DCRs in planar BPF can effectively provide a very wideband range for spurious suppression. The dual‐mode BPF is designed at center frequency (f0) of 5.2 GHz, and has a very wideband spurious suppression below 30 dB as far as over 5f0 when using the DCRs. The measured results have a good agreement with the EM simulated results. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1694–1697, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25332