The Experts below are selected from a list of 7293 Experts worldwide ranked by ideXlab platform
Fuchang Chen - One of the best experts on this subject based on the ideXlab platform.
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compact dual band bandpass filter with controllable bandwidths using stub loaded multiple mode resonator
Iet Microwaves Antennas & Propagation, 2012Co-Authors: Fuchang Chen, Qingxin ChuAbstract:A compact microstrip-line dual-band bandpass filter using a stub-loaded multiple-mode resonator is presented. This multiple-mode resonator is formed by loading three stubs (one short-circuited and two open-circuited stubs) in shunt to a simple uniform impedance resonator in the centre and two symmetrical locations, respectively. By properly adjusting the lengths of the three stubs, the first two resonant modes of this multiple-mode resonator can be allocated within the first passband, whereas the third and fourth resonant modes can be allocated within the second passband of the dual-band filter. This results in the formulation of a novel dual-band filter with compact-size and high isolation between Passbands by incorporating this multiple-mode resonator with source-load coupling. Two coupling paths are used to control the bandwidth of each passband independently. To illustrate the concept, two dual-band filters of different frequency ratios are designed, fabricated and measured. Simulated and measured results are found to be in good agreement with each other, showing that a rejection level of 15 dB up to more than four times the first passband frequency can be obtained.
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a novel crossed resonator and its applications to bandpass filters
IEEE Transactions on Microwave Theory and Techniques, 2009Co-Authors: Fuchang Chen, Zhihong Tu, Huan WangAbstract:A novel open and short stubs loaded crossed resonator and its applications to cross-coupling filter and tri-band bandpass filters are presented in this paper. Based on the lossless transmission line model analysis, it is found that the first three resonance frequencies of the crossed resonator can be conveniently controlled. Benefiting from this feature, the resonator can be utilized to design not only a cascaded triplet (CT) filter, but also a tri-band bandpass filter. The tri-band filter offers two tunable Passbands and one fixed passband. The first and third passband frequencies can be tuned effectively by changing the lengths of the stubs. To demonstrate these applications, a CT filter and two tri-band bandpass filters using a crossed resonator are implemented. The experiments verify the theoretical predictions and simulations.
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design of compact tri band bandpass filters using assembled resonators
IEEE Transactions on Microwave Theory and Techniques, 2009Co-Authors: Fuchang ChenAbstract:A novel approach for designing tri-band bandpass filters with independently controllable center frequencies and improved stopband rejection characteristic is presented in this paper. The assembled resonator constructed by a stepped impedance resonator and a common half-wavelength resonator is employed to obtain tri-band response. The stepped impedance resonator is designed to operate at the first and third Passbands and the other resonator is designed to operate at the second passband. Two kinds of filter configurations with cascaded and pseudointerdigital formats are proposed. Based on lossless lumped-element equivalent circuit, it is found that both filter structures can introduce transmission zeros between Passbands. To verify the proposed approach, two filters are designed and fabricated, the measured results exhibit tri-band bandpass responses with high selectivity.
Jongsik Lim - One of the best experts on this subject based on the ideXlab platform.
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dual band bandpass filter with independently tunable center frequencies and bandwidths
IEEE Transactions on Microwave Theory and Techniques, 2013Co-Authors: G Chaudhary, Yongchae Jeong, Jongsik LimAbstract:This paper presents a novel approach to the design of tunable dual-band bandpass filter (BPF) with independently tunable passband center frequencies and bandwidths. The newly proposed dual-band filter principally comprises two dual-mode single band filters using common input/output lines. Each single BPF is realized using a varactor-loaded transmission-line dual-mode resonator. The proposed filter also offers switchable characteristics to select either of the Passbands (either the first or the second passband only). To suppress the harmonics over a broad bandwidth, defected ground structures are used at input/output feeding lines without degrading the Passbands characteristics. From the experimental results, it was found that the proposed filter exhibited the first passband center frequency tunable range from 1.48 to 1.8 GHz with a 3-dB fractional bandwidth (FBW) variation from 5.76% to 8.55% and the second passband center frequency tunable range from 2.40 to 2.88 GHz with the 3-dB FBW variation from 8.28% to 12.42%. The measured harmonic results of the proposed filters showed a rejection level of 19 dB, which is up to more than ten times of the highest center frequency of the first passband without degradation of the Passbands.
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harmonic suppressed dual band bandpass filters with tunable Passbands
IEEE Transactions on Microwave Theory and Techniques, 2012Co-Authors: G Chaudhary, Yongchae Jeong, Jongsik LimAbstract:This paper presents a novel approach to the design of tunable dual-band bandpass filter with broadband harmonic suppression characteristics. The proposed filter structure offers the possibility of two tunable Passbands, as well as a fixed first passband and controllable second passband. The tunable passband frequency usually causes a shift of the harmonics, which need to be suppressed to improve out-of the passband characteristics. In order to suppress the harmonics over a broad bandwidth, defected ground structures are used at input and output feeding lines without degrading the Passbands characteristics. Both theory and experiment are provided to validate the proposed filter. From the experimental results, it is found that the proposed filter exhibits a first passband center frequency tunable range of 34.14% from 0.85 to 1.2 GHz with the almost constant 3-dB fractional bandwidth (FBW) of 13% and second passband center frequency tunable range of 41.81% from 1.40 to 2.14 GHz with the 3-dB FBW of 11%. The measured results of the proposed filters show a rejection level of 20 dB up to more than ten times of second passband frequency can be obtained, thereby ensuring broad harmonics rejection characteristics without degradation of Passbands. The measurement data have good agreement with the simulation.
Wen Wu - One of the best experts on this subject based on the ideXlab platform.
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tunable dual band filter based on stub capacitor loaded half mode substrate integrated waveguide
IEEE Transactions on Microwave Theory and Techniques, 2017Co-Authors: Chunxia Zhou, Wen WuAbstract:This paper presents an original and simple approach to the design of dual-band bandpass filters (BPFs) using the proposed stub-capacitor-loaded half-mode substrate-integrated waveguide (HMSIW) structure. The stub-capacitor-loaded HMSIW structure is investigated and a set of analytical equations is provided for the determination of center frequency, transmission zero, coupling coefficient, and external quality factor. Dual-band BPFs can be achieved by loading stub capacitor on the two sides of the HMSIW structure. The two Passbands can be designed separately and controlled independently. To validate this method, a class of dual-band filters with a wide range of fractional bandwidth ratios of the two Passbands is designed. Finally, a dual-band filter, with each passband tuned only by one control voltage, is fabricated and measured. The results show that the first passband can be tuned in a frequency range from 1.85 to 2.67 GHz (36.4%) without any effect on the second passband. In the meantime, the second passband varies from 3.84 to 5.34 GHz (32.7%) without any effect on the first passband. Good return loss is observed within a wide tuning range.
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compact multi band bandpass filters with mixed electric and magnetic coupling using multiple mode resonator
IEEE Transactions on Microwave Theory and Techniques, 2015Co-Authors: Jin Xu, Wen WuAbstract:In this paper, a multiple stubs loaded ring resonator (MSLRR) is proposed to design directly coupled multi-band bandpass filters (BPFs) with mixed electric and magnetic coupling (MEMC). The proposed MSLRR exhibits multiple-mode resonant behavior. The increased number of loaded stubs excite many more useful resonant modes, but these resonant modes can be still independently controlled. As examples, a dual-band BPF, a tri-band BPF, a quad-band BPF, and a quint-band BPF using different types of MSLRRs are designed and fabricated. The passband frequencies and return losses (RLs) of these multi-band BPFs can be independently controlled. A dual-mode open loop resonator is then introduced in the quint-band BPF to enhance the sixth resonant mode of the MSLRR to produce the sixth passband so that a sext-band BPF is also presented. Multiple transmission zeros due to the cancelling effect of MEMC and virtual grounds in the MSLRR can be observed around the Passbands resulting in sharp passband selectivity and high band-to-band isolation. Moreover, all of the fabricated multi-band BPFs have compact sizes, good RLs, and low insertion losses. Good agreements are observed between the simulated and measured results.
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dual band siw differential bandpass filter with improved common mode suppression
IEEE Microwave and Wireless Components Letters, 2015Co-Authors: Yijin Shen, Hui Wang, Wei Kang, Wen WuAbstract:A dual-band differential bandpass filter with controllable differential-mode (DM) center frequencies, and high common-mode (CM) suppression as well as band-to-band isolation, is proposed in this letter. The presented filter is implemented based on the substrate integrated waveguide (SIW) technology. The first DM passband can be derived by the dominant modes, while the second DM passband response can be obtained by employing the higher order modes. The center frequencies of two DM Passbands can be tuned by changing the dimension parameters. To improve the CM suppression, four slotlines with different locations are etched on the top metal plane. The measured and simulated results are in good agreement.
Xiangfei Chen - One of the best experts on this subject based on the ideXlab platform.
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microwave photonic filter with multiple independently tunable Passbands based on a broadband optical source
Optics Express, 2015Co-Authors: Long Huang, Dalei Chen, Fangzheng Zhang, Peng Xiang, Tingting Zhang, Peng Wang, Xiangfei ChenAbstract:In this paper, a novel microwave photonic filter (MPF) with multiple independently tunable Passbands is proposed. A broadband optical source (BOS) is employed and split by a 1:N coupler into several branches. One branch is directed to a phase modulator which is modulated by a radio frequency signal and the other branches are delayed by optical delay lines (ODLs), respectively. All of these branches are combined by another 1:N coupler and sent to a dispersion compensation fiber which is used to introduce group delay dispersion to the optical signal. At a photodetector, each time-delayed broadband lightwave beating with the sidebands produced by the phase modulator forms a passband of the MPF. By tuning the delay of each broadband lightwave, the center frequency of the passband can be independently tuned. An MPF with two independently tunable Passbands is experimentally demonstrated. The two Passbands can be tuned from DC to 30 GHz with a 3-dB bandwidth of about 250 MHz. The stability and dynamic range of the MPF are also evaluated. By employing more branches delayed by ODLs, more Passbands can be generated.
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microwave photonic filter with two independently tunable Passbands using a phase modulator and an equivalent phase shifted fiber bragg grating
IEEE Transactions on Microwave Theory and Techniques, 2014Co-Authors: Jiejun Zhang, Xiangfei ChenAbstract:A dual-passband microwave photonic filter (MPF) implemented based on phase-modulation to intensity-modulation (PM-IM) conversion using a phase modulator and an equivalent phase-shifted fiber Bragg grating (EPS-FBG) is proposed and experimentally demonstrated. The key component in the system is the EPS-FBG, which is designed and fabricated based on the equivalent phase-shift technique. The unique feature of the EPS-FBG is that equivalent phase shifts are introduced to both of the ±1st channels, leading to a notch in each of the two channels. Thus, by implementing PM-IM conversion in the two channels, two Passbands are produced. The central frequency of each passband is determined by the wavelength different between the notch and the optical carrier. In the design and fabrication, two phase shifts are introduced to the EPS-FBG to decrease the shape factor, which is defined as the ratio between the 20- and 3-dB bandwidths. In addition, a stimulated Brillouin scattering (SBS) assisted filter is incorporated in the system for carrier suppression to increase the spurious-free dynamic range (SFDR) and decrease the noise figure (NF) of the MPF. An experiment is performed. A dual passband filter with a 3-dB bandwidth and a shape factor of 167.3 MHz and 3.8, and 143.3 MHz and 3.3 for the 1st and 2nd passband is achieved. The frequency tunable ranges of the 1st and 2nd Passbands are 5.4 and 7.4 GHz, respectively, with the magnitude variations of about ±0.5 dB during the turning. Due to the SBS-assisted filter, the SFDRs are increased by 7 dB and the NFs are decreased by 10 dB.
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microwave photonic filter with two independently tunable Passbands using a phase modulator and an equivalent phase shifted fiber bragg grating
IEEE Transactions on Microwave Theory and Techniques, 2014Co-Authors: Liang Gao, Xiangfei Chen, Jiejun Zhang, Jianping YaoAbstract:A dual-passband microwave photonic filter (MPF) implemented based on phase-modulation to intensity-modulation (PM-IM) conversion using a phase modulator and an equivalent phase-shifted fiber Bragg grating (EPS-FBG) is proposed and experimentally demonstrated. The key component in the system is the EPS-FBG, which is designed and fabricated based on the equivalent phase-shift technique. The unique feature of the EPS-FBG is that equivalent phase shifts are introduced to both of the ±1st channels, leading to a notch in each of the two channels. Thus, by implementing PM-IM conversion in the two channels, two Passbands are produced. The central frequency of each passband is determined by the wavelength different between the notch and the optical carrier. In the design and fabrication, two phase shifts are introduced to the EPS-FBG to decrease the shape factor, which is defined as the ratio between the 20- and 3-dB bandwidths. In addition, a stimulated Brillouin scattering (SBS) assisted filter is incorporated in the system for carrier suppression to increase the spurious-free dynamic range (SFDR) and decrease the noise figure (NF) of the MPF. An experiment is performed. A dual passband filter with a 3-dB bandwidth and a shape factor of 167.3 MHz and 3.8, and 143.3 MHz and 3.3 for the 1st and 2nd passband is achieved. The frequency tunable ranges of the 1st and 2nd Passbands are 5.4 and 7.4 GHz, respectively, with the magnitude variations of about ±0.5 dB during the turning. Due to the SBS-assisted filter, the SFDRs are increased by 7 dB and the NFs are decreased by 10 dB.
Jay A Bookbinder - One of the best experts on this subject based on the ideXlab platform.
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temperature and emission measure profiles along long lived solar coronal loops observed with the transition region and coronal explorer
The Astrophysical Journal, 1999Co-Authors: Dawn D Lenz, E E Deluca, Leon Golub, R Rosner, Jay A BookbinderAbstract:We report an initial study of temperature and emission-measure distributions along four steady loops observed with the Transition Region and Coronal Explorer at the limb of the Sun. The temperature diagnostic is the filter ratio of the extreme-ultraviolet 171 and 195 A Passbands. The emission-measure diagnostic is the count rate in the 171 A passband. We find essentially no temperature variation along the loops. We compare the observed loop structure with theoretical isothermal and nonisothermal static loop structure.
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temperature and emission measure profiles along long lived solar coronal loops observed with trace
arXiv: Astrophysics, 1999Co-Authors: Dawn D Lenz, E E Deluca, Leon Golub, R Rosner, Jay A BookbinderAbstract:We report an initial study of temperature and emission measure distributions along four steady loops observed with the Transition Region and Coronal Explorer (TRACE) at the limb of the Sun. The temperature diagnostic is the filter ratio of the extreme-ultraviolet 171-angstrom and 195-angstrom Passbands. The emission measure diagnostic is the count rate in the 171-angstrom passband. We find essentially no temperature variation along the loops. We compare the observed loop structure with theoretical isothermal and nonisothermal static loop structure.
