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In this letter, a compact circularly polarized (CP) microstrip patch filtenna designed by reusing dual‐mode substrate integrated waveguide (SIW) cavity is proposed. The dual‐mode SIW cavity, operating at its TE120 and TE210 modes, can be used not only as the first stage resonator of the filtering network but also feeds the four microstrip patches working at their TM10 and TM01 modes. A pair of asymmetric perturbed posts is inserted in the SIW cavity to perturb the electric field distributions of TE120 and TE210 modes so as to achieve one axial ratio (AR) minima. The other AR minima is realized by sequentially exciting the four orthogonal microstrip patches via the four rectangular slots that are etched on the top surface of the SIW cavity. In addition, four metal posts penetrated the SIW cavity is employed to improve the impedance matching. For verification, a CP filtenna prototype centered at 5.13 GHz is designed, manufactured, and tested. The measured results agree well with the simulated ones, demonstrating a fractional impedance bandwidth of 6.9% (4.95–5.3 GHz), a 3 dB AR bandwidth of 4.2% (5–5.21 GHz), and a maximum boresight realized gain of 8.4 dBic. [ABSTRACT FROM AUTHOR]

A novel third‐order tunable cross‐coupled trisection bandpass filter (BPF) based on dual‐mode resonators (DMRs) is presented in this letter. Electric and magnetic dominant coupling path can be constructed by using two coupled DMRs to meet the requirement of cross‐coupled tunable bandpass filter with constant bandwidth. Three resonating modes of the two DMRs are used to build the cross‐coupled trisection tunable bandpass filter topology. The coupling structure is analyzed and the coupling coefficients are calculated. The tunable BPF is designed, and a transmission zero (Tz) due to the cross‐coupled trisection topology is generated, so that frequency selectivity is enhanced. The prototype is fabricated and measured. The measured results show that the fabricated circuit realizes a tunable central frequency range from 1.64 to 2.16 GHz, maintaining a −3 dB bandwidth of 119.5 ± 3.5 MHz, and a Tz is generated at the lower side of the passband. [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]

ABSTRACT: A novel and compact microstrip dual-mode bandpass filter with multi-transmission zeros is designed, fabricated, and measured in this letter. The presented filter consists of a modified square-loop resonator (MSLR) with dual-mode resonant characteristic and an improved input/output defected microstrip structure with a dual-bandgap feature, which is overlapped with the MSLR at the input/output tapping location. Finally, a planar wideband filter with low insertion loss and high selectivity is simulated by the full-wave electromagnetism solver, and verified by our circuit experiment. The measured results of proposed filter have agreed well with the simulated ones, and have shown an excellent electric characteristic with −3 dB fractional bandwidth 33.9% at the mid-band frequency, minimum insertion loss 0.5 dB, maximum return loss better than −20 dB, and four transmission zeros nearby the lower and upper pass-band edges. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:618-621, 2017 [ABSTRACT FROM AUTHOR]

ABSTRACT Based on a single and uniform coupled-line section, a novel and simple dual-mode resonator with a wide range of external quality factor is proposed. The even- and odd-mode (dual-mode) resonance frequencies are created from unequal effective dielectric constants of a single coupled line. The operating principle is explained, and simulated examples are illustrated. Finally, a microstrip narrowband (14%) dual-mode high-selectivity bandpass filter operating at 2.6 GHz with two transmission zeros (2.02 and 2.97 GHz) is designed, fabricated, and measured. The good agreement between the simulated and measured results verifies this proposed idea. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2355-2358, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT In this letter, a novel high selectivity and common-mode (CM) suppression wideband balanced microstrip passband filter (BPF) is proposed using the short stub centrally loaded short-ended resonators (SSCLSR). The odd-mode resonant frequency of the SSCLSR can be flexibly controlled by the short stub, whereas the even-mode one is fixed. First, the wideband single-ended BPF are designed based on the microstrip SSCLSR with the parallel coupled microstrip line input/output (I/O). Two transmission zeros near the passband edges can be generated due to the main path signal counteraction and source-loaded coupling. Further, the CM equivalent half circuits of the balanced BPF based on the wideband single-ended BPF are investigated in detail. Thus, a wideband balanced BPF with high CM suppression within the passband is designed, fabricated, and measured. Good agreement between simulated and measured results is obtained. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2940-2944, 2014 [ABSTRACT FROM AUTHOR]

ABSTRACT A dual-mode microstrip resonator whose strip conductor is partially split from its one end by a longitudinal slot has been studied. The resonator has two fundamental modes, even and odd ones. The difference of their frequencies is controlled by varying the slot length. Based on such resonators, original structures of a diplexer and passband filters including dual-band have been designed. Measured performances of their fabricated prototypes prove applicability of designed devices in microwave engineering. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2186-2190, 2013 [ABSTRACT FROM AUTHOR]

In this letter, a novel compact and high selectivity dual-mode dual-band microstrip bandpass filter (BPF) with quarter-wavelength resonator and stub-loaded resonator is proposed using extended feed lines.Either of the SIRs cannot only separately generate one passband but also mainly control the passband performance. Due to the extended feed lines, parasitic coupling and intrinsic characteristics of the resonators, multiple transmission zeros can be created to improve the selectivity. Meanwhile, the BPF can obtain compact size due to the folded resonators and feed lines. A dual-mode dual-band BPF with the fractional bandwidth 15.6 and 6.4% is designed and fabricated. The simulated and measured results show a better agreement and validate the proposed theory. The size is only 0.185λg × 0.130λg in which λgis the guided wavelength at the first passband center frequency. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 2702:2705, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27211 [ABSTRACT FROM AUTHOR]

Two novel microstrip band-pass filters using dual-mode patch resonators with slot structures are proposed and optimized in this article. By using etched slot defected structures in the circle patch resonator and the regular hexagon patch resonator, the filters have remarkable advantages, such as compact size, high selectivity, and simple structure. The proposed band-pass filters are simulated, fabricated, and measured. Each of the band-pass filters has two transmission zeros. The measured results prove to be largely consistent with the simulated results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2130-2133, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27002 [ABSTRACT FROM AUTHOR]

In this article, a dual-mode microstrip bandpass filter (BPF) with compact size, sharp skirt, and wide upper-stopband performance is proposed using the short-stub-loaded open loop stepped-impedance resonator and source-load coupling structure. The advantageous features of the resonator are that the even-mode resonant frequencies can be controlled exclusively by the short stub, and two transmission zeros are created near the passband by the short stub and the folded arms. Meanwhile, two transmission zeros generated by the source-load coupling structure can be applied to suppress the first and second spurious harmonics. Finally, a microstrip BPF located at 2.4 GHz with a fractional bandwidth 4% is designed, fabricated, and measured. The upper stopband in experiment is extended up to 20 GHz with an insertion loss lower than −21.2 dB. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1618-1621, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26881 [ABSTRACT FROM AUTHOR]

A novel compact bandpass filter (BPF) with good in band and wide upper-stopband performances is realized using open stub loaded dual-mode resonator.The resonator generates two operating modes in the desired band and the even-mode resonance frequency can be flexibly controlled by the disc-shaped open stub at central plane, whereas the odd-mode one is fixed. By simply adjusting the dimension of the disc-shaped open stub, the even resonant mode falls down and works together with the odd mode to form a BPF. Two other pairs of open stubs are mainly applied to suppress the high harmonic resonant modes and obtain good match, respectively. Experimental results of the fabricated filter show good agreement with the simulated results. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2185–2188, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.25453 [ABSTRACT FROM AUTHOR]

ABSTRACT In this work, a microwave tunable filter of inverted microstrip with dual-mode resonator using liquid crystal (LC) technology has been designed, manufactured, and characterized. It comprises a thin LC layer between a ground plane and a directly coupled and inverted microstrip line. Central frequency tunability was realised by applying low ac voltages, thus involving low power consumption. The transmission characters of the filter were specifically designed for working at C-band microwave frequency range, which are allocated for many communication applications such as satellite, cordless telephone or weather radar systems. Additionally, its compact structure allows the device to be integrated on circuit board to adapt with other MW components for expanded applications. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1626-1628, 2016 [ABSTRACT FROM AUTHOR]

This paper presents a dual-band bandpass filter by introducing transmission zeroes in the passband of a broadband bandpass filter using square-loop dual-mode resonators. The transmission zeroes are achieved by using a dual-mode resonator. The dual-mode resonator is attached to two transmission lines of same length. These lines are coupled to similar transmission lines that are attached to the I/O ports. The filter has a compact size, low losses, and good rejection between the two bands. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1567–1570, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23427 [ABSTRACT FROM AUTHOR]

One novel compact ultra-wideband filter having high-frequency selectivity and wide stopband is developed by using microstrip stub-loaded dual-mode resonator couples. Open stub-loaded and short stub-loaded are used to widen the passband of filter without aperture-enhanced coupled line structure. Five transmission poles in the passband are shown. Two sharp attenuation poles can be located close to either side of the desired pass band. And the other two attenuation poles can be located in the stopband of upper frequencies, so as to reject the third resonant modes of stub-loaded resonators. The passband of filter and the locations of attenuation poles can be controlled by the sizes of the open stub and short stub. The measured results demonstrate that the insertion loss is lower than 1.0 dB in the passband (3.9–11.6 GHz), higher than 15.0 dB in the upper-stopband (12.0–19.5 GHz), whereas the group delay variation in the passband is less than 0.5 ns. The measured result agrees well with the EM simulation. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 53–55, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24014 [ABSTRACT FROM AUTHOR]

A differential bandpass filter based on double-sided parallel-strip line (DSPSL) dual-mode resonator is proposed in this article. This differential bandpass filter makes use of the inherent differential feature of DSPSL to construct feeding ports and resonating unit. This filter has the advantages of low-profile structure, low-insertion loss for differential-mode signal, and high suppression for common-mode signal. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1733–1735, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23493 [ABSTRACT FROM AUTHOR]

A novel dual-mode microstrip filter operating at 900 MHz is proposed using degenerate modes of a microstrip-loop resonator. The resonator structure that is formed of meandered microstrip-line elements has a smaller size than the other dual-mode microstrip resonators in the literature. The dual-mode filter is verified by both simulation and measurement. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 376–377, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20828 [ABSTRACT FROM AUTHOR]