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A new type of dual‐wideband bandpass filter using composite series and shunt resonators is proposed in conjunction with its direct synthesis and design theory. By making use of the transmission pole (TP) and the transmission zero of the composite resonators flexibly, a dual‐wideband filter with a wide range of frequency and bandwidth ratios as well as a wide stopband can be realised. With a shunt capacitor introduced at each I/O port, extra TPs either in the low passband or in the high passband can be created, leading to more filter design options. To give a direct design procedure, a lumped‐element prototype is first synthesised based on a target filtering function and a dedicated circuit extraction process. The filter layout can be realised using semi‐distributed circuits and chip capacitors. Two practical schemes are introduced to suppress spurious resonances for a wide high‐rejection stopband. Two filter examples are designed with a small and a large frequency ratio and a wide band suppressed spurious resonances. The unique filter response and good agreement between the designed and measured results demonstrate the superior performance of the proposed filter structure and the effectiveness of the synthesis and design theory. [ABSTRACT FROM AUTHOR]

In this work, we present a bilateral reflectionless filter topology. A low‐pass filter prototype and its theoretical frequency responses are given. The frequency responses are obtained by means of ABCD matrices, thereby showing that the proposed prototype is reciprocal, symmetrical, and reflectionless at both ports. A first‐order bandpass filter with the reflectionless characteristic has been designed by applying the conventional low‐pass‐to‐bandpass transformation to the proposed low‐pass filter topology. It is verified by measurement results that the proposed bandpass filter can have less than −20 dB reflection coefficient over the passband and stopband at both ports with the same transmission response of a conventional first‐order bandpass filter. [ABSTRACT FROM AUTHOR]

This article proposed a miniaturized bandpass filter implemented with the substrate integrated coaxial line (SICL).A four-pole quasi-elliptic SICL bandpass filter with two symmetric transmission zeros is designed, fabricated, and measured with a minimal size of 0.168 λ0 by 0.088 λ0, where λ0 is the wavelength of free space at the central operating frequency. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:131-133, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27249 [ABSTRACT FROM AUTHOR]

ABSTRACT A frequency reconfigurable bandpass filter using an electronically tunable dual-mode Substrate Integrated Waveguide (SIW) resonator is presented. Four lumped capacitors as electric tuning elements are loaded near the regions of strongest electric field of TE102 and TE201 modes. The resonant frequency of these two orthogonal modes is tuned by different capacitance values of four lumped capacitors coupled to the SIW resonator. Measured results show that the proposed filter exhibits a tuning range of about 37% from 3.44 to 5 GHz with the total insertion loss variation of 1.85-5.2 dB. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:934-937, 2017 [ABSTRACT FROM AUTHOR]