Showing papers on "Stopband published in 2015"

Broadband elastic metamaterial with single negativity by mimicking lattice systems

Abstract: The narrow bandwidth is a significant limitation of elastic metamaterials for practical engineering applications In this paper, a broadband elastic metamaterial with single negativity (negative mass density or Young's modulus) is proposed by mimicking lattice systems It has two stop bands and the bandwidth of the second one is infinite theoretically The effect of the relevant parameters on band gaps is discussed A continuum model is proposed and the selection of materials is discussed in detail It shows that continuum metamaterials can be described accurately by using the lattice model, and the second stopband can be ultra-broad but not infinite This discrepancy is investigated and a method is provided to calculate the upper limit of the second stopband for a continuum metamaterial As a verification, the proposed metamaterial is used for wave mitigation over broadband frequency ranges Moreover, the present method is extended to design 2D anisotropic elastic metamaterials, and a device to control the direction of elastic wave transmission is proposed as an example

Magnetically tunable wideband microwave filter using ferrite-based metamaterials

Abstract: Magnetically tunable wideband microwave filters have been designed and prepared by using ferrite-based metamaterial structures. The microwave properties of the filters have been investigated by experiments and simulations. The negative permeability appears around the ferromagnetic resonance frequency, which leads to a remarkable stopband for the bandstop filter. The bandpass filter is composed of two kinds of ferrite rods with different saturation magnetization. The bandwidth of the passband can be tuned by adjusting the saturation magnetization of the ferrite rods. Both the experimental and the simulated results show that those filters possess magnetically tunable property. This approach opens a way for designing tunable wideband microwave filters.

Reflectionless Filter Structures

Abstract: This paper expands on the previously described reflectionless filters—i.e., filters having, in principle, identically zero reflection coefficient at all frequencies—by introducing a wide variety of new reflectionless structures that were not part of the original publication. In addition to extending the lumped-element derivation to include transmission line filters, this is achieved by the introduction of a novel method wherein the left- and right-hand-side stopband terminations are coupled to each other using a two-port sub-network. Specific examples of the sub-network are given, which increase the stopband attenuation per filter cell and steepen the cutoff response without disrupting the reflectionless property or increasing the insertion loss in the passband. It is noteworthy that a common feature of all the structures derived by these methods is that most, if not all, of the reactive elements are of equal normalized value. This greatly simplifies the tuning requirements, and has facilitated their implementation as monolithic microwave integrated circuits (MMICs). A number of examples of MMIC reflectionless filters constructed in this way are presented and their results compared to the theory.

A Tri-Band Bandpass Filter With Wide Stopband Using Asymmetric Stub-Loaded Resonators

Abstract: This letter presents a tri-band bandpass filter (BPF) with a wide stopband using asymmetric stub-loaded resonators (ASLR). A tri-band filter sample was fabricated by using two ASLRs with coupled I/O ports. By properly tuning the electrical length ratios of the ASLRs ( $\alpha$ and $\gamma$ ), three passbands can be designed at 1.4, 2.4, and 3.5 GHz. The harmonic responses are suppressed effectively by forming an uncoupled section at the end of the ASLRs, and the stopband region is formed from 3.7 to 7 GHz with a rejection level of 30 dB. The measured results of the fabricated tri-band BPF exhibit good agreement with simulated results.

A visual and organic vapor sensitive photonic crystal sensor consisting of polymer-infiltrated SiO2 inverse opal.

Abstract: A photonic crystal (PC) sensor that can selectively detect organic vapors through visual color changes has been proposed. The sensor was fabricated by infiltrating a tetraphenylethene polymer (TPEP) into the voids of SiO2 inverse opal photonic crystal. When the sensor was exposed to tetrahydrofuran or acetone vapor, a red shift of the stopband of more than 50 nm could be clearly observed; meanwhile, the film's color changed from violet to cyan. Subsequently, when exposed to air, the stopband underwent a blue shift and the color returned to violet. The reason for the observed change is that a reversible adsorption–desorption process occurs on alternate exposure of the sensor to organic vapor and air, due to the high specific surface area of the inverse opal macroporous structure and the high affinity of TPEP to tetrahydrofuran and acetone. The adsorption of vapor analyte can increase the PC's effective refractive index, which will induce the stopband red shift and the resulting color change according to Bragg's Law. The reversible adsorption–desorption of organic vapors varied the effective refractive index of the sensor repeatedly, causing the reversible stopband shift and color change, and providing a general method for the design of visual vapor sensors.

A Novel Design Method for Compact UWB Bandpass Filters

Abstract: In this letter, a new design method of ultra wideband bandpass filter (UWB BPF) is proposed. Based on a symmetrical structure of a simple uniform line loaded by a stepped-impedance open stub (SIS) connected at its center, the proposed design method employs simultaneously the optimization of a defined objective function in the range of frequency 3.1–10.6 GHz and the transmission zeros at cut-off frequencies for a rapid convergence. Obtaining different filter sizes with good performance, the compact UWB BPF is simulated, fabricated, and measured. A good agreement between simulation and measurement is obtained while achieving good performances such as a return loss better than 10 dB, an upper stopband attenuation higher than 20 dB up to 17.6 GHz, and a sharp selectivity.

Tunable 1.25–2.1-GHz 4-Pole Bandpass Filter With Intrinsic Transmission Zero Tuning

Abstract: A new concept of tuning transmission zeros (TZs) in 4-pole tunable bandpass filters is demonstrated. In this work, the tuning elements that were conventionally used for bandwidth control are also utilized for adjusting the TZs at the same time. As a result, the selectivity of the tunable filter can be controlled without increasing the filter order and complexity. A 4-pole stripline filter is used to demonstrate this concept. The filter can be continuously tuned from 1.25 to 2.1 GHz and two TZs are employed to improve the stopband suppression to $> {\hbox{60 dB}}$ at 200 MHz from the passband. These TZs can also be moved from the upper stopband to the lower stopband without any auxiliary tuning elements to significantly change the stopband suppression. The high rejection filter is useful in wireless systems and cognitive radios with large interferers.

Compact lowpass filter with wide stopband using stepped impedance hairpin units

Abstract: A novel microstrip lowpass filter (LPF) with a wide stopband is presented. The basic resonator is composed of two stepped impedance hairpin units with one embedded in another, which can obtain two more transmission zeros and extend a wide stopband. Based on the proposed resonator, a demonstration LPF of compact size, sharp transition and wide stopband has been designed, fabricated and measured. The proposed filter exhibits a small size of 0.081λg × 0.113λg, where λg is the waveguide length at the cutoff frequency of 1.6 GHz. Results show good agreement with simulations and the 20 dB rejection stopband can be extended to more than 15 GHz.

Compact Filtering Rat-Race Hybrid With Wide Stopband

Abstract: This paper presents a novel method to design filtering rat-race hybrids with wide-stopband bandpass responses. Four ${\pm}\ K$ -inverters with bandpass functions are utilized to replace the one or three quarter-wavelength transmission lines in the conventional rat-race hybrid. The ${\pm} K$ -inverters consist of transmission lines and capacitors, which can reduce the area occupied and suppress the high-order harmonics. Furthermore, the isolation performance is enhanced by embedding the ${\pm} K$ -inverters. Theoretical analysis is carried out and design equations are derived. For demonstration, a filtering rat-race hybrid with bandpass responses is implemented. The center frequency is located at 470 MHz with the insertion loss of 1.2 dB. Good in-phase and out-of-phase characteristics are observed. Comparisons between the measured and simulated results are also presented to verify the theoretical analysis. The overall size is only 4.6% of the conventional hybrid and stopband is extended to $5f_{0}$ .

Compact filtering power divider with high frequency selectivity and wide stopband using embedded dual-mode resonator

Abstract: A novel compact filtering power divider with high frequency selectivity and a wide stopband is proposed. The bandpass filtering response is implemented by using embedded dual-mode resonators. Source/load cross-coupling is used to improve the frequency selectivity of the passband. In addition, the even- and odd-mode method can be applied to analyse the proposed power divider. The presented filtering power divider has been designed, fabricated and measured. The measured results show reasonable agreement with the simulated ones.

Periodic Collinear-Slotted Leaky Wave Antenna With Open Stopband Elimination

Abstract: A low cross-polarization periodic-slotted ridged substrate-integrated waveguide (RSIW) leaky wave antenna (LWA) array is presented. Parametric constraints of the structure were investigated to realize a periodic leaky wave antenna (PLWA) with the ability of scanning from backward endfire into the forward quadrant. An appropriate multimode transverse equivalent network (TEN) is presented for the proposed antenna and values of leakage rate and phase constant for different parameters of the structure were extracted using the transverse resonance technique (TRT). The obtained results were compared to those achieved from HFSS software simulations. The open stopband in the broadside is eliminated using certain dimensions for the structure. By simultaneously manipulating a number of parameters, a variable ${\alpha}$ and constant ${\beta}$ are resulted so that the desired sidelobe level (SLL) can be realized. The proposed structure was simulated and then manufactured. Simulation results show good agreement with measurement results.

An Ultra-Compact Common-Mode Bandstop Filter With Modified-T Circuits in Integrated Passive Device (IPD) Process

Abstract: Based on multi-cell modified-T circuits, this paper proposes a novel circuit topology to realize a common-mode bandstop filter with differential-mode all-pass characteristics for high-speed digital differential circuits. The circuit behaviors for both differential and common modes are analyzed based on symmetrical network analysis techniques. Two transmission zeros at common mode can be synthesized by the derived formulas. The proposed design flow is used to realize a test sample in the integrated passive device process. Simulated and measured results are in good agreement. The common-mode suppression band $(\vert S_{{ cc}21}\vert is from 1.6 to 4.7 GHz, whose fractional bandwidth is nearly 100%. The cutoff frequency of the differential mode can maintain up to 10 GHz with a constant group delay. Moreover, eye diagrams under different signaling rates all perform well. Compared with the other literature, the proposed common-mode filter has a very wide common-mode stopband, the highest differential-mode cutoff frequency up to 10 GHz, and the most compact circuit size of $0.017~\lambda_{g}\times 0.016~\lambda_{g}$ .

Design of two-channel filter bank using nature inspired optimization based fractional derivative constraints.

Abstract: In this article, a novel approach for 2-channel linear phase quadrature mirror filter (QMF) bank design based on a hybrid of gradient based optimization and optimization of fractional derivative constraints is introduced. For the purpose of this work, recently proposed nature inspired optimization techniques such as cuckoo search (CS), modified cuckoo search (MCS) and wind driven optimization (WDO) are explored for the design of QMF bank. 2-Channel QMF is also designed with particle swarm optimization (PSO) and artificial bee colony (ABC) nature inspired optimization techniques. The design problem is formulated in frequency domain as sum of L2 norm of error in passband, stopband and transition band at quadrature frequency. The contribution of this work is the novel hybrid combination of gradient based optimization (Lagrange multiplier method) and nature inspired optimization (CS, MCS, WDO, PSO and ABC) and its usage for optimizing the design problem. Performance of the proposed method is evaluated by passband error (ϕp), stopband error (ϕs), transition band error (ϕt), peak reconstruction error (PRE), stopband attenuation (As) and computational time. The design examples illustrate the ingenuity of the proposed method. Results are also compared with the other existing algorithms, and it was found that the proposed method gives best result in terms of peak reconstruction error and transition band error while it is comparable in terms of passband and stopband error. Results show that the proposed method is successful for both lower and higher order 2-channel QMF bank design. A comparative study of various nature inspired optimization techniques is also presented, and the study singles out CS as a best QMF optimization technique.

Wideband filtering power divider with high selectivity

Abstract: A wideband filtering power divider (PD) with high selectivity is introduced, based on a terminated coupled line structure. The bandwidth tuning, isolation and impedance matching performances optimisation are presented and explained. Finally, the filtering PD is designed and implemented with a centre frequency (f 0) of 3.0 GHz and a fractional bandwidth of 70%. The upper stopband is achieved up to 2.6 f 0, with a rejection of better than 13 dB. The measured minimum in-band insertion loss is 0.3 dB (not including the splitting loss). Isolation of higher than 16.7 dB between the output ports is observed up to 2.7 f 0.

K-Band Substrate-Integrated Waveguide Resonator Filter With Suppressed Higher-Order Mode

Abstract: In this letter, we present a design method for K-band substrate-integrated waveguide (SIW) resonator filters utilizing ${\rm TM}_{02}$ mode. More importantly, a methodology for suppressing an unwanted higher-order mode ( ${\rm TM}_{11}$ ) close to the passband is demonstrated. It is shown that suppressing the unwanted mode give rise to the improved stopband performance. In addition, the resonator used in this filter design has capability of adjusting the resonant frequency, and this allows for compensating the fabrication error. Verification of the presented design method has been carried out by fabricating and measuring the filter.

High-Selectivity Low-Pass Filters With Ultrawide Stopband Based on Defected Ground Structures

Abstract: 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 ( $>15 f_{c}$ or $20~f_{c}$ ), low passband insertion loss (<0.3 dB), compact size, and sharp skirt characteristic.

Design of microstrip lowpass filter with wide stopband and sharp roll-off using hexangular shaped resonator

Abstract: A compact lowpass filter using a hexangular shaped resonator is presented. The designed lowpass filter has a −3 dB cutoff frequency of 2.97 GHz. The stopband bandwidth for the attenuation level of −20 dB is from 3.32 GHz up to 21 GHz, and the circuit only occupies 10.04 × 10.92 mm2. The structure is simulated, fabricated and measured. Both simulation and measured results are presented and compared and there is good agreement between them. The insertion loss in the passband is <0.06 dB and the fabricated filter presents a sharp transition band from 2.97 to 3.32 GHz for the attenuation level of −3 and −20 dB, respectively.

60-nm-thick basic photonic components and Bragg gratings on the silicon-on-insulator platform.

Abstract: We demonstrate integrated basic photonic components and Bragg gratings using 60-nm-thick silicon-on-insulator strip waveguides. The ultra-thin waveguides exhibit a propagation loss of 0.61 dB/cm and a bending loss of approximately 0.015 dB/180° with a 30 μm bending radius (including two straight-bend waveguide junctions). Basic structures based on the ultra-thin waveguides, including micro-ring resonators, 1 × 2 MMI couplers, and Mach-Zehnder interferometers are realized. Upon thinning-down, the waveguide effective refractive index is reduced, making the fabrication of Bragg gratings possible using the standard 248-nm deep ultra-violet (DUV) photolithography process. The Bragg grating exhibits a stopband width of 1 nm and an extinction ratio of 35 dB, which is practically applicable as an optical filter or a delay line. The transmission spectrum can be thermally tuned via an integrated resistive micro-heater formed by a heavily doped silicon slab beside the waveguide.

Synthesis of Inline Mixed Coupled Quasi-Elliptic Bandpass Filters Based on $\lambda/4$ Resonators

Abstract: This paper proposes a general synthesis method for inline mixed coupled quasi-elliptic bandpass filters based on $\lambda/4$ resonators. Different from the conventional modeling with lumped and mixed inductive and capacitive coupling, the proposed mixed-coupling model here includes not only the coupling magnitudes, but also their paths’ phases inside the mixed coupling. According to the presented formulation, there exists one lower side transmission zero for the capacitive-dominant mixed coupling. However, there are two transmission zeros in the upper stopband for the inductive-dominant case, and these two transmission zeros can be analytically synthesized with different coupling path ratios. The proposed synthesis method is then applied to design two second-order bandpass filters based on inductive-dominant coupled $\lambda/4$ resonators, resulting in two upper stopband transmission zeros. Furthermore, this synthesis method is extended to design two fourth-order quasi-elliptic bandpass filters with both inline capacitive- and inductive-dominant mixed couplings. Finally, the designed filters are fabricated and measured to provide successful verification on the proposed mixed coupling model approach.

Narrowband Coupled-Line Bandstop Filter With Absorptive Stopband

Abstract: This paper presents a new type of absorptive bandstop filter (ABSF) design that is targeted for absorbing the local-oscillator-to-RF leakage of mixer in a heterodyne receiver The proposed ABSF is designed to absorb the input power at its Port 1, and it is achieved by introducing one lossy resonator to a conventional narrowband coupled-line bandstop filter Suitable equivalent circuit models and closed-form design equations are established to enable the direct synthesis of proposed ABSFs Specifically, a proposed microstrip ABSF with a stopband center frequency $f_{0}$ of 2 GHz is demonstrated The maximal stopband rejection is 348 dB with an input return loss of 277 dB, which implies that 998% of the input power is dissipated by the proposed ABSF

A Novel Compact $E$ -Plane Waveguide Filter With Multiple Transmission Zeroes

Abstract: This paper presents a novel compact $E$ -plane waveguide filter using multiple resonators, which lead to multiple transmission zeroes The proposed filter is less than $015~\lambda_{ g}$ in length of a waveguide The key of the proposed method is to design the locations of transmission zeroes Four transmission zeroes, of which two are located in the upper stopband, while the other two are in the lower stopband, are produced by four resonators The couplings between the resonators and locations of the transmission zeroes are carefully analyzed and designed, which enhance the selectivity as well as the out-of-band performance Theoretical studies and experimental investigations are conducted to demonstrate the proposed design The good agreement between the simulation results and measurement results is achieved Moreover, this kind of filter can be implanted well in $E$ -plane structures

A Planar Dual-Band Periodic Leaky-Wave Antenna Based on a Mu-Negative (MNG) Transmission Line

Abstract: In this study, a planar periodic leaky-wave antenna (LWA) that provides a dual-band full-space scanning property is presented. The LWA is based on a mu-negative (MNG) transmission line that offers a nonlinear dispersion characteristic with a very simple structure. The dual-band beam scanning property is achieved by utilizing the $n = -1$ and $n = -2$ space harmonics to overcome the limitation of the MNG line that provides forward scanning only in the $n = 0$ space harmonic. Microstrip bends are introduced to achieve proper matching and thereby suppress the open stopband effect at both broadside radiation frequencies, to avoid interference between two space harmonics, and to ensure efficient radiation. The proposed design method is validated by good agreement between the simulated and experimental results for the dual-band LWA that is designed to provide full-space scanning with the first and second broadside radiation frequencies at 4.3 and 8 GHz. The demonstrated total scan angle range of 279° is the widest range reported for the dual-band LWA.

Tunable band-notched coplanar waveguide based on localized spoof surface plasmons.

Abstract: This Letter proposes a simple band-notched coplanar waveguide (BNCPW), which consists of a coplanar waveguide (CPW) and an ultra-thin periodic corrugated metallic strip that supports spoof surface plasmon polaritons (SSPPs) with defect units on the back of the substrate. By introducing a defect unit or multiple defect units into the strip, a narrow stopband or multiple narrow stopbands would be generated flexibly and conveniently. The band-notch function is based on the idea that a defect mode, which exists in the bandgap between the fundamental and the first higher mode of the SSPPs, can be introduced to form a stopband. Thus, the SSPPs field is localized around the defect units, which is another form of localized spoof surface plasmons (LSSPs). By properly tuning the dimensions of each defect unit, the absorption level and center frequency of the stopband could be adjusted independently. We offer theoretical analysis and experimental results to validate our idea and design. In this framework, a variety of band-notched devices and antennas in the microwave and terahertz (THz) frequencies can be easily designed without additional band-stop filters.

U-Shape Slots Structure on Substrate Integrated Waveguide for 40-GHz Bandpass Filter Using LTCC Technology

Abstract: Millimeter-wave (mmW) bandpass filter using substrate integrated waveguide (SIW) is proposed in this paper The propagation constants of three different types of electromagnetic bandgap (EBG) units are discussed and compared with their passbands and stopbands performance The slotted-SIW unit shows a very good lower stopband and upper stopband performance The mmW bandpass filter with three cascaded uniform slotted-SIW-based EBG units is constructed and designed at 40 GHz The extracted coupling coefficient ( ${K}$ ) and quality factor ( ${Q}$ ) are used to determine the filter circuit dimensions To prove the validity, the previous proposed structure is fabricated in a single circuit layer using low-temperature co-fired ceramic technology and measured at 40 GHz, respectively The measured results are in good agreement with simulated results in such frequency and the measured insertion losses at 40 GHz is 142 dB, respectively

Compact lowpass filter with wide stopband using coupled rhombic stubs

Abstract: A compact and high selective lowpass filter (LPF) with wide stopband is presented using coupled rhombic stubs. The proposed LPF unit is constructed by loading a rhombic stub on a transmission line. Then, a folded three-element LPF is proposed to achieve compact size and high selectivity by introducing coupling between adjacent rhombic stubs. The operating mechanism of the filter is investigated and explained, by adopting the physically-based LC-equivalent circuit model. The implemented final LPF exhibits a wide stopband of up to 11.5 f c with a rejection level of better than 35 dB. Furthermore, the final LPF features a compact size of 0.12λ g × 0.10λ g, where λ g is the guide wavelength of f c, and a very high figure-of-merit (FOM) of 27 142.

Compact ultra-wide stopband low pass filter using multimode resonators

Abstract: A compact microstrip ultra-wide stopband low pass filter using multimode resonators is presented. It consists of a narrow width microstrip line with high impedance and three multimode resonators. The characteristics and equivalent circuits of the multimode resonator are investigated. Owing to the strong slow-wave and bandstop effects, the multimode resonator can be implemented to achieve an ultra-wide stopband and size reduction. At the 3 dB cut off frequency of 1.8 GHz, the measured stopband of the low pass filter with 15 dB suppression is from 2.83 to 24 GHz. The physical size of the proposed low pass filter is 0.09λ g × 0.11λ g. The presented simulation and measurement results are in good agreement.

Compact Quasi-Elliptic Response Wideband Bandpass Filter With Four Transmission Zeros

Abstract: This letter presents a novel quasi-elliptic response bandpass filter (BPF) with 3 dB fractional bandwidth of 39.8% for 2.4 GHz WLAN application. Four resonant modes from two stepped-impedance stub loaded shorted stepped-impedance resonators (SISLSSIRs) and one dual-mode shorted stub loaded stepped-impedance resonator (SSLSIR) can constitute an asynchronously tuned coupled-resonator circuit which support a wideband performance. Four transmission zeros (TZs), i.e., one TZ due to the mixed electric and magnetic coupling, one TZ due to the harmonic effects, and another two TZs owing to the cross-couplings, are realized on both sides of the passband, resulting in its quasi-elliptic response performance. The radial stubs and high-impedance open stubs are loaded at the middle position of SISLSSIRs to improve the in-band return loss of BPF. The fabricated filter has a compact size of $0.22\lambda_{\bf g}\times 0.22\lambda_{\bf g}$ and wide upper stopband from 2.62 to 7.69 GHz. Good agreement is shown between the simulated and measured results.

Compact lowpass filter with wide stopband bandwidth

Abstract: A compact microstrip lowpass filter (LPF) which consists of a meander line, a coupled line and two open stubs is proposed. The mechanism for reallocating filter transmission zeros and the design procedure are explained. The simulated and measured results demonstrate that this LPF provides compact size, low insertion loss, and wide stopband. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:367–371, 2015