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ABSTRACT Compact microstrip triband bandpass filters are proposed and designed based on asymmetrically loaded resonators in this letter. By attaching single open-circuited stub or short-circuited stub at the proper position of the microstrip line and adjusting their lengths, the first three resonant modes of the proposed resonators can be usefully allocated within the three passbands of the triband filter. Two alternative triband filters with compact size are designed and measured. The measured results provide successful verification for the theoretical analysis. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:1862-1865, 2014 [ABSTRACT FROM AUTHOR]

ABSTRACT Tri-band bandpass filter using centrally loaded resonators is presented in this article. The triple-passband characteristics are realized by properly controlling the lengths and impedances of the uniform impedance resonator and the stub. To illustrate the concept, two tri-band filters are designed, fabricated, and measured. Simulated and measured results are found to be in good agreement with each other. The prototype of the tri-band filters achieve insertion loss of 1.6, 1.9, and 1.9 dB at 2.4, 3.5, 5.8 GHz, 1.2, 1.3, and 1.3 dB at 1.57, 2.45, 5.2 GHz, respectively. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2695-2699, 2013 [ABSTRACT FROM AUTHOR]

A modified wideband bandpass filter based on a bandstop filter is realised using half‐wavelength and one‐wavelength open‐circuited resonators. Six transmission zeros are utilised to obtain the sharp rejection characteristics over a broad stopband. The passband bandwidth can be varied by changing the impedance of the configuration. A compact prototype filter with 27% bandwidth is demonstrated. Without coupling gaps between resonators, the new filter shows low insertion loss and is easy for fabrication. To illustrate the concept, a bandpass filter is designed, fabricated and measured. Simulated and measured results are found in good agreement with each other. [ABSTRACT FROM AUTHOR]

Dual‐band bandstop filters using open‐circuited stub‐loaded resonators are presented. The first and second resonant frequencies of the open‐circuited stub‐loaded resonator can be flexibly controlled by tuning the length and position of the open‐circuited stub. To illustrate the concept, a dual‐band bandstop filter has been designed, fabricated and measured. The prototype of the dual‐band bandstop filter achieved attenuation of 42 and 44 dB at 2.4 and 5.2 GHz. [ABSTRACT FROM AUTHOR]

A novel wideband bandstop filter is proposed in this paper. Using one uniform impedance resonator and two stepped impedance resonators, five transmission zeros are introduced in the stopband. Appropriate positioning of these zeros ensures the high selectivity and flat rejection level of the stopband. The bandwidth of the filter can be conveniently controlled by the characteristic impedances of the connecting lines and resonators. A complete analytic analysis is proposed to fully control the positions of transmission zeros, and the design equations and design rules for the bandstop filter are given in detail by using the lossless transmission line model. To illustrate the concept, a wideband bandstop filter with center frequency at 2 GHz and rejection level below 20 dB is fabricated. Theoretical, simulated, and measured results are found in good agreement with each other, and the measured 20-dB rejection bandwidth is as wide as 150%. [ABSTRACT FROM PUBLISHER]

Compact microstrip low-pass filters (LPFs) with ultrawide stopband based on a defected ground structure (DGS) and their design procedures are presented in this paper. A key merit of the filter configuration is that the selectivity of the LPFs can be conveniently controlled, whereas the bandwidth is fixed. The LPFs are realized using open-circuited uniform impedance stubs and stepped-impedance stubs (SISs). The position of the transmission zeros can be freely controlled by tuning the impedance ratio of the SISs. To expand the stopband, the dumbbell DGS is used to suppress the spurious passbands of the LPFs. Two demonstration filters with a cutoff frequency at 1 GHz have been designed, fabricated, and measured. The measured results indicate good performance: broad stopband ( >15 fc or 20~fc ), low passband insertion loss (<0.3 dB), compact size, and sharp skirt characteristic. [ABSTRACT FROM PUBLISHER]

ABSTRACT This article proposes a novel type of microstrip cascaded triplet filter with controllable electric and magnetic coupling. The electric coupling can be tuned by adjusting the gap between the resonators, while the magnetic coupling is dominated by the diameter of the via-hole. A transmission zero on the upper stopband is produced by the inductive cross-coupling. To further improve the selectivity of the filter, the source-load coupling is also proposed to introduce two tunable transmission zeros. To expand the stopband, proper feeding position is selected to suppress the third and fifth harmonics. Based on the proposed structure, a third-order filter are designed and fabricated. Good agreement between the measured and simulated data is obtained. Measured results indicate that a rejection level of 20 dB up to more than six times the passband frequency can be obtained. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2937-2940, 2014 [ABSTRACT FROM AUTHOR]