Dual Bandpass Filter Research Articles

Ultra-compact dual mode dual band filter based on separate electric and magnetic coupling paths

A pair of dual mode independent controllable resonators used to realize dual band pass filter with good frequency selectivity and isolation is presented. The resonators are directly connected to input/output and are coupled through electric and magnetic coupling in two different paths. Magnetic coupling between the resonators is achieved using a common grounded via-hole between the two set of quarter-wavelength resonators. Electric coupling is achieved through open edge coupling of the resonators. Two independent resonators with Separate Electric and Magnetic Coupling (SEMC) paths produce an independently controllable dual band filter response and also additional transmission zeros (TZs) at the edges of the pass bands. The TZs are introduced to improve the selectivity of the filter. Filter exhibits desired pass band response at the Universal Mobile Telecommunications System (UMTS) band (1.95-2.2 GHz) and Worldwide Interoperability for Microwave Access (WiMAX) band (3.4-3.6 GHz). Proposed compact filter is implemented on RT/Duroid 5880 (er = 2.2) substrate with thickness of 0.785 mm and surface area of 15 × 12 sq. mm.

Tunable Dual-Passband Microwave Photonic Filter Based on Stimulated Brillouin Scattering

A novel ultra-narrow dual-passband microwave photonic filter (MPF) with wide tunability based on stimulated Brillouin scattering (SBS) is presented. The proposed dual-passband MPF is implemented via the usage of carrier suppressed modulation of an electrooptic modulator (EOM). The passband separation of the dual-passband filter is determined by the oscillation radio frequency (RF) that is applied onto the EOM, where the frequency change of the RF oscillator results in two times the bandpass frequency shift with a central frequency that is symmetric with respect to the SBS frequency shift. A complete theoretical model based on the combined effects of the Brillouin gain and loss in a dual-wavelength Brillouin pump structure is presented to characterize the filter RF responses. Experimental results show a widely tunable dual-passband MPF that has an ultra-narrow bandwidth of 20.1MHz with over 35 dB out-of-band rejection ratio and a 20-3-dB bandwidth shape factor of 2.5.

Multiple band notch and Dual-Band filter using concentric and contiguous split ring resonators (CCSRR)

A novel, compact, multiple band notch filter and dual-band filters are presented. Contiguous and concentric split ring resonators (SRRs) and Ring resonator are used to achieve desired multiple narrow band notches. These band notches have been designed to avoid the undesired interference between co-existing wireless channels. The dual-band filter consists of a dual SRR having splits on the opposite sides with Inductive Short Stub Split Ring Resonator. Even- and odd-mode analyses have been performed to calculate the resonance frequencies. Three transmission zeros are achieved between the two passbands by both dominant electric or dominant magnetic coupling and also cancellation effect of electric and magnetic coupling. This results in high passband selectivity and improved band-to-band isolation. The proposed dual-band pass filter has the advantages of being compact with more degree of freedom to achieve desired passbands by controlling the electric and magnetic coupling independently. Proposed filter is implemented on RT/Duroid 5880 (εr = 2.2) substrate of thickness 0.785 mm and surface area of 0.27λg × 0.27λg. Insertion loss of the proposed filter at notch bands is high (>13 dB) and low (<0.8 dB) in pass band. Measured results correlate with the simulated results and thus ensure that the proposed filter is a suitable candidate to mitigate interference caused by the co-existing and emerging wireless technologies.

Compact dual-band filtering-response power divider with high in-band frequency selectivity

A novel compact dual-passband filtering-response power divider using modified stepped impedance resonators (SIRs) is presented. The quarter-wavelength transmission lines of conventional Wilkinson power divider are replaced by the dual-band bandpass filters to realize dual-passband bandpass response, and the phase shift of the proposed filters is tuned to be 90°. An isolation resistance R is placed at the center of the symmetric plane to realize good isolation between the two output ports. Two modified SIRs are adopted in the dual-passband filters to improve the return loss in both two passbands and control the resonant frequencies. The characteristic of the modified SIR is also analyzed. Meanwhile, the resonant frequencies can be tuned by changing impedance ratio of SIR. The source–load coupling is utilized to improve the frequency selectivity and achieve a high out-of-band rejection. A prototype of the proposed power divider is designed, fabricated, and measured. Reasonable agreement between the simulated results and measured ones is demonstrated.

Design of dual‐bandpass filters using stepped‐impedance circular ring resonator

A stepped-impedance circular ring resonator (SICRR) with two pairs of stubs is proposed for the design of a dual-bandpass filter. This quad-mode resonator is applied to produce two passbands. It is found that the centre frequencies and bandwidths of the two passbands can be tuned by varying the lengths of the stubs. Simulation results show that the defined impedance ratio K and the electrical length ratio α of between the SICRR segments can affect the frequency separation between the two passbands. A prototype filter centred at 3.4 and 5.56 GHz is designed and fabricated. Good agreement between the simulated and measured results was achieved for the SICRR filter.

Compact tri to dual passband switchable bandpass filter using stub‐loaded split‐ring resonator with improved bandwidth

Stub-loaded split-ring resonators (SRRs) are presented for the design of a compact tri- to dual-band bandpass filter (BPF). The length of the two concentric split-rings having splits on the opposite sides, the gap between the two concentric split-rings and the length of the stub determine the positions of the three passbands. Switchability has been achieved by controlling the closing and opening of the inner ring of the SRRs using pin diodes. The responses of the BPF depend upon the condition of the switch. Moreover, lumped coupling capacitors are connected between the two SRRs to enhance the bandwidths of the passbands of the BPF. It also permit a greater coupling-gap between the SRRs which further reduces the challenges of fabrication.

Teeter-totter effect of terahertz dual modes in C-shaped complementary split-ring resonators

A teeter-totter effect of terahertz (THz) resonant modes in C-shaped complementary split-ring resonators (CSRRs) is observed. The dual resonant mode transmission enhancement was investigated using THz time-domain spectroscopy. The intensity of the lower-frequency resonance modes increases monotonically with the CSSR gap width, which is accompanied by a monotonic decrease in the intensity of the higher-frequency resonance modes. The origin of the dual resonant modes is numerically explained by the electromagnetic energy density distribution and surface current analysis. The inductive-capacitive resonance dominates the lower frequency mode, while the dipole oscillation dominates the higher frequency mode. By tuning the gap of the CSRR, an equilibrant transmittance of above dual resonance modes can be designed. This teeter-totter effect promises a possible application of CSSRs as potential dual-bandpass filters in the THz-region.

Transmission zero controllable bandpass filters with dual and quad‐band

Microstrip dual and quad-band bandpass filters with triangular stepped-impedance resonators are developed by using separate electric and magnetic coupling paths. Either the magnetic-dominant coupling or the electric-dominant coupling generates a transmission zero (TZ) but at different positions and the corresponding TZ can be controlled and adjusted by controlling the electric or magnetic coupling coefficient. Both the electric and the magnetic-dominant couplings generate a pair of TZs, but the additional coupling resonators are not required. The new designs have been demonstrated by measurement. Advantages of the new filters are not only their compact circuit topologies, miniature circuit sizes, independently controllable filter operation frequencies, but also their controllable TZs.

이중 급전 구조를 갖는 마이크로스트립 이중 모드 대역통과 필터

In this paper, a microstrip dual mode band pass filter with doubly fed line is proposed. The proposed filter consists of a corner truncated patch with right crossed slots and doubly fed lines. In general, the resonator with the right crossed slots simultaneously has size reduction and spurious response suppression. In order to improve the rejection performance in out of its higher stop band, the dual mode resonator is excited by using doubly fed line. Details of the filter characteristics are described, and both simulated and measured results of the designed filter are presented.

Design of dual‐bandpass filter using zeroth‐order resonance and Bragg frequency

This study presents a novel compact dual-bandpass filter using zeroth-order resonance and Bragg frequency of the composite right/left handed transmission line (CRLH-TL) resonator. By taking advantage of the Bragg frequency, two resonance modes are obtained with only one CRLH-TL unit cell. The equivalent circuit for the novel resonator is proposed and analysed. The resonance frequencies are given by using the circuit model and the input impedance is calculated. Dimensions of the resonator can be obtained based on the values of the lumped elements in the equivalent circuit. Compared with the conventional half-wavelength resonator, the size of the presented resonator is only about one-tenth of it. Then, the zeroth-order resonance and Bragg frequency modes are demonstrated using the dispersion curve. A dual-bandpass filter is designed to verify the resonator analysis. The source–load coupling is involved to improve the frequency selectivity of the filter. The fabricated filter is compact with a size of only 0.09 λg × 0.16 λg. The two central frequencies are located at 2.4/3.3 GHz and the filter has a wide upper stopband of over 4 GHz. Moreover, the fabricated filter has five transmission zeros and good frequency selectivity is observed.

Dual-bandpass filter built on rectangular dielectric resonators

A new technique of implementing dual-bandpass filters built on rectangular dielectric resonators has been proposed. The possibility of simultaneous tuning of two passbands on one structure of coupled dielectric resonators using their intrinsic high-mode oscillations was investigated for the sake of reducing the size of design. The proposed analytical solution was compared with the results of simulation by the finite element method. Coupling coefficients of rectangular resonators were calculated and investigated by a numeric technique for the low dipole TE 01δ and high quadruple TE 02δ magnetic modes depending on the parameters of filter design. The proposed dual-bandpass filter built on dielectric resonators can be used in base stations and wireless access points of communication networks.

A novel dual bandpass filter incorporating left-handed transmission line based dual-band resonator

This paper presents a left-handed transmission line (LH TL) based dual-band resonator to implement the dual-band filter. The proposed resonator consists of one uniform LH TL and one right-handed transmission line (RH TL) to produce three transmission zeros at 52 GHz, 267 GHz, and 531 GHz. The perforated ground plane is applied to extend the operating bandwidth of the LH TL for covering the full bandwidth of the dual-band filter. A CMOS prototype is designed based on the proposed resonator, and measured through the on-wafer measurements. Both simulated and the measured results confirm the insertion-losses of 1.8 dB and 2.4 dB of two passbands at 186 GHz and 420 GHz. The statistic shows the total length of the proposed resonator is about 0.038 λg at 52 GHz.

High-selectivity Dual-bandpass Filter Using Coupled Lines

In this paper, a microstrip dual-band bandpass filter is presented. The mechanism of the dual-band operation is shown as follows. Resonator modes are located to two passband by adjusting the even- and odd-mode impedance. Transmission zeros are then appear on both sides of two passband skirts and in the rejection bands by adjusting the coupling coefficient of the shorted quarter-wavelength microstrip line. Additional transmission zeros can be obtained to improve the passband selectivity. For demonstration, a dual-band bandpass filter working at 0.8 and 2.2 GHz is designed and fabricated. The theoretical analysis and measurement are presented. The good agreement verifies the proposed method.

Microwave Photonic Filter With Two Independently Tunable Passbands Using a Phase Modulator and an Equivalent Phase-Shifted Fiber Bragg Grating

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.

粮食筛选系统中双通道带通滤光膜的研制

Optical sorting of grain,is using different characteristics of near infrared absorption spectra of impurity inferior food and high quality food,and based on the difference of feature band which reflects the test components in the spectrum to do the sieving grain.Before the light beam into the sensor,it needs to pass through the optical filter,filtering the multiple test band and reducing the noise effect.A dual bandpass optical filter was developed which is the core parts in the system,it is based on the film system design theory,adopt Smith method and the film system design software basing on the combination of period and non period multilayer coatings to design the dual band-pass filter coating,.Utilize electron beam evaporation and ion assisted deposition method to prepare and mathematical modeling to analyze,which has reduced the influence of experimental error to the spectrum and prepared the filter coating.The average transmittance of which is more than 97%in 1 200 nm and 1 450 nm band and less than 1%in 1 000~1 130 nm and 1 130~2 000 nm band.The film meets the use requirements through the test system and evaluation.

Compact electronically tunable microstrip dual-band filter using stub-loaded SIRs

A compact electronically tunable dual-bandpass filter (BPF) with harmonic suppression is investigated in this paper. The BPF is composed of a step-impedance resonator, a T-stub with a varactor diode and a filtering network. The second passband can be independently tuned by varying the bias voltage across the varactor, whereas the first passband is fixed. The proposed filter exhibits wide stopband due to the introduction of the filtering network suppressing harmonics. A prototype of a tunable dual-band BPF, in which the second passband is tuned from 1.58 to 2.21 GHz and the first passband is fixed at 0.98 GHz, is designed and fabricated. The simulated and measured results are in good agreement with each other.

A tunable dual-passband filter based on improved ring resonator

A miniaturized varactor-tuned microstrip bandpass filter (BPF) based on an improved ring resonator is presented in this paper. The proposed BPF is comprised of a ring as 1/2 λ resonator with two varactors in the middle section and a coupling scheme. The variation of coupling coefficient can be controlled by using a capacitor. The center frequency of the lower passband can be tuned from 3.2 to 3.9 GHz, while the center frequency of the upper passband is at 4.9 GHz and it is fixed during the process. Theoretical analysis and design approach are demonstrated. Finally, the predicted results are compared with measured data and good agreement is reported.

A 3.8-mW 3.5–4-GHz Regenerative FM-UWB Receiver With Enhanced Linearity by Utilizing a Wideband LNA and Dual Bandpass Filters

A low-power regenerative frequency-modulated ultra-wideband (FM-UWB) receiver with wideband signal reception and linear FM-AM conversion is implemented in 65-nm CMOS for short-range communication systems. Different from the conventional regenerative FM-UWB receiver having the narrowband low-noise amplifier (LNA), the proposed receiver employs a wideband LNA and dual bandpass filters (BPFs) to improve the robustness against narrowband interference and frequency shift-keying demodulation with a relaxed Q requirement of the BPF. A 3.5-4-GHz FM-UWB receiver consisting of a stacked LNA, dual BPFs, two envelop detectors, and a subtractor successfully performs FM demodulation through wireless transmission from a 100-kb/s FM-UWB transmitter, consuming the total power of 3.8 mW.

AMP-Activated Protein Kinase Signaling Protects Oligodendrocytes that Restore Central Nervous System Functions in an Experimental Autoimmune Encephalomyelitis Model

AMP-activated protein kinase (AMPK) signaling is reported to protect neurons under pathologic conditions; however, its effect on oligodendrocytes (OLs) remains to be elucidated. We investigated whether AMPK signaling protects OLs to restore central nervous system (CNS) functions in an experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis. Increased inflammation and demyelination in the CNS and peripheral immune responses were consistent with the observed clinical impairments in EAE animals, which were attenuated by treatment with metformin compared with vehicle. In addition, expressions of neurotrophic factors and of signatory genes of OL lineages were increased in the CNS of metformin-treated EAE animals. Likewise, metformin attenuated inflammatory response and enhanced expressions of neurotrophic factors, thereby protecting OLs via AMPK activation in mixed glial cultures stimulated with lipopolysaccharide/interferon γ invitro, as evidenced by analysis of the expression of signatory genes of O1(+)/MBP(+) OLs and their cellular populations. Metformin also attenuated oxidative stress and malondialdehyde-containing protein levels, with corresponding induction of antioxidative defenses in OLs exposed to cytokines via AMPK activation. These effects of metformin were evident in the CNS of EAE animals. These data provide evidence that AMPK signaling is crucial to protect OLs and, thus, CNS functions in EAE animals. We conclude that AMPK activators, including metformin, have the potential to limit neurologic deficits in multiple sclerosis and related neurodegenerative disorders.

Dual and tri-band bandpass filters based on novel Π-shaped resonator

A novel Π-shaped resonator is proposed, and compact dual-band and tri-band bandpass filters that meet IEEE 802.11 application requirements by using the new resonator are designed. The dual-band bandpass filter centres at 2.45 and 5.6 GHz with a simulated passband insertion loss of no more than 0.8 dB, and the tri-band bandpass filter which is got by two-path coupling achieves simulated passband insertion loss of no more than 1.1 dB. The new designs are demonstrated by experiment. The new filters have advantages of simple and compact structures, low passband insertion losses, good frequency selectivity and miniature circuit sizes. All these have prospect to be applied in future wireless communication systems.