Bandstop Structure Research Articles

Planar wideband band-stop filter with T-inverted shaped open stubs for wideband applications

This paper presents a wideband band-stop filter (BSF) structure designed by using planar technology. The proposed filter consists of a modified conventional band-stop structure with open stubs, inner T-inverted shape, and two input/output feed lines. Based on series of optimization and a specific design method, two compact filters with good electrical performance are obtained. In order to characterize the frequency response of the proposed filters, the performance is carried out numerically using two different solvers (Advanced Design System -Momentum and CST-MWS). Furthermore, in order to validate the conception approach, two circuits are designed, fabricated, and tested. Additionally, an equivalent circuit of the wideband BSF is built to estimate the electromagnetic simulation results for practical realization. The features of the design have a reduced size, wideband rejection, and higher insertion losses, which can be performed by adjusting the L-shaped stubs (23.25 × 2.2 mm2) toward the 50 Ω input and output ports. Two filters are designed, fabricated, and tested; one can be operated between an fractional bandwidth (FBW) of about 50% at a center frequency of 1.8 GHz, and the other can be switched from an FBW of 43.38% at a center frequency of 1.82 GHz. In addition, good agreement between the simulation and the measured results is achieved. The overall size of each filter is 43.4 × 34.5 mm2.

Characterization, Analysis, and Implementation of Integrated Bandstop Structures on Ultra-Wideband Archimedean Spiral Antenna

A subsection of the radiating spiral arm, placed in parallel, induces a bandstop response at a notch frequency proportional to the resonant length of the strip. Detailed parametric study on the effect of variation of design parameters for an Archimedean spiral antenna and the resonant parallel strip (RPS) is presented. Empirical analysis on phase velocity on the radiating spiral arms allows characterization of RPS in terms of its resonant length. Identified systematic relation between design parameters and filter response is applied to design an antenna for the 3.1–10.5 GHz operating band with the notch response over the IEEE 802.11a band, 5.15–5.95 GHz. Successful implementation is demonstrated through performance comparison between simulated and experimental results.

Multiband Bandstop Filter using an I-Stub-Loaded Meandered Defected Microstrip Structure

This paper presents a compact multiband band- stop filter (BSF) that utilizes I-stubs embedded within a meandered defected microstrip structure (MDMS). The proposed design for obtaining a single stopband is ana- lyzed by using a transmission line network model. On the basis of the single stopband structure, we designed and fabricated a dual- and tri-band bandstop filters operating at 2.5/6.78 GHz and 1.98/5.6/7.78 GHz, respectively, thereby exploring the concept of generating as many stop- bands by simply adding the same number of I-stubs. The proposed filter also features the possibility of tuning the resonance frequencies by varying the width of the I-stubs.

Two particle model for studying the effects of space-charge force on strong head-tail instabilities

In this paper, we present a new two particle model for studying the strong head-tail instabilities in the presence of the space-charge force. It is a simple expansion of the well-known two particle model for strong head-tail instability and is still analytically solvable. No chromaticity effect is included. It leads to a formula for the growth rate as a function of the two dimensionless parameters: the space-charge tune shift parameter (normalized by the synchrotron tune) and the wakefield strength, Upsilon. The three-dimensional contour plot of the growth rate as a function of those two dimensionless parameters reveals stopband structures. Many simulation results generally indicate that a strong head-tail instability can be damped by a weak space-charge force, but the beam becomes unstable again when the space-charge force is further increased. The new two particle model indicates a similar behavior. In weak space-charge regions, additional tune shifts by the space-charge force dissolve the mode coupling. As the space-charge force is increased, they conversely restore the mode coupling, but then a further increase of the space-charge force decouples the modes again. Lastly, this mode coupling/decoupling behavior creates the stopband structures.

Dual-band bandpass filters with high isolation using coupled lines

Two novel second-order dual-band bandpass filters (BPFs) with high isolation and high selectivity using coupled lines are realised with a T-shaped bandstop structure. The centre frequencies of the two dual-band BPFs can be adjusted to the desired values by changing the coupling coefficients and characteristic impedances of the two transmission paths. Two dual-band BPFs located at 1.87 and 2.53 GHz and 1.9 and 2.42 GHz are designed and fabricated for demonstration. Good agreements can be observed between simulated and measured performances.

Systematic Design of Bandstop Power Distribution Network Using Resonant Vias

A systematic design method is proposed to achieve the optimal design of bandstop power delivery network (PDN) using resonant vias in a multilayered printed circuit board (PCB). With the proposed equivalent-circuit model, design equations, and design charts, the geometrical structure of a resonant via-type bandstop structure can be quickly designed according to the desired stopband bandwidth and isolation level. Wideband bandstop PDN designs using the resonant vias in standard four-layer PCB are fabricated and measured to demonstrate the effectiveness of proposed design method.

An analysis of a discontinuous spectral element method for elastic wave propagation in a heterogeneous material

The numerical dispersion and dissipation properties of a discontinuous spectral element method are investigated in the context of elastic waves in one dimensional periodic heterogeneous materials. Their frequency dependence and elastic band characteristics are studied. Dispersion relations representing both pass band and stop band structures are derived and used to assess the accuracy of the numerical results. A high-order discontinuous spectral Galerkin method is used to calculate the complex dispersion relations in heterogeneous materials. Floquet---Bloch theory is used to derive the elastic band structure. The accuracy of the dispersion relation is investigated with respect to the spectral polynomial orders for three different cases of materials. Numerical investigations illustrate a spectral convergence in numerical accuracy with respect to the polynomial order based on the elastic band structure and a discontinuous jump of the maximum resolvable frequency within the pass bands resulting in a step-like increase of it with respect to the polynomial order.

Novel N-band tunable resonator based on N-order dual-behavior resonator and tunable capacitors

An N-band resonator, particularly well-suited for reconfigurability, is presented in this paper together with its synthesis. The resonator is based on the association of an N-band dual-behavior resonator and tunable capacitors. Its topology consists of a parallel association of N + 1 different bandstop structures, each one composed of a stub terminated by a capacitor. N pass bands, separated from each other by a transmission zero, are then obtained. As each bandstop structure independently controls one transmission zero, the use of variable capacitors allows each of them to be tuned independently and then to reconfigure the resonator in terms of transmission zeros and resonant frequencies. After the presentation of the general synthesis, this principle is validated by the realization of a tri-band resonator in microstrip technology.

A Wideband Noise-Isolation Bandstop Power Distribution Network Using Quarter-Wavelength Line-Based Structure

This paper presents the design of wideband bandstop power distribution network using the quarter-wavelength $(\lambda/4)$ line-based bandstop structure. A simple synthesis method starting from the specification on stopband bandwidth is also proposed with detailed design flow and equations. The synthesized $\lambda/4$ -line bandstop structure has been implemented and verified with circuit simulation, electromagnetic simulation, and measurement. The test board is fabricated using the standard printed circuit board process, and the results show an extremely wide stopband from 1 GHz to more than 20 GHz with 70-dB isolation.

Reflection by absorbing periodically stratified media

Existing theory gives the optical properties of a periodically stratified medium in terms of a two by two matrix. This theory is valid also for absorbing media, because the matrix remains unimodular. The main effect of absorption is that the reflection (of either polarization) becomes independent of the number of periods N, and of the substrate properties, provided N exceeds a certain value which depends on the absorption. The s and p reflections are then given by simple formulae. The stop-band structure, which gives total reflection in bands of frequency and angle of incidence in the non-absorbing case, remains influential in weakly absorbing media, causing strong variations in reflectivity. The theory is applied to the frequency dependence of the normal-incidence reflectivity of a quarter-wave stack in which the high-index and low-index layers both absorb weakly. Analytical expressions are obtained for the frequency at which the reflectivity is maximum, the maximum reflectivity, and also for the reflectivity at the band edges of the stop band of the non-absorbing stack.

Design of dual‐band bandpass filter with improved upper stopband using novel stepped‐impedance resonator

AbstractIn this letter, a new dual‐band bandpass filter with multispurious suppression is proposed using novel stepped‐impedance resonators (SIRs). The proposed resonator is composed of a SIR with embedded bandstop structure. A third‐order filter is designed and fabricated that shows a rejection level of 30 dB up to 20 GHz (8.33f1). © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:603–606, 2014

High-frequency homogenization of zero-frequency stop band photonic and phononic crystals

We present an accurate methodology for representing the physics of waves, in periodic structures, through effective properties for a replacement bulk medium: this is valid even for media with zero-frequency stop bands and where high-frequency phenomena dominate. Since the work of Lord Rayleigh in 1892, low-frequency (or quasi-static) behaviour has been neatly encapsulated in effective anisotropic media; the various parameters come from asymptotic analysis relying upon the ratio of the array pitch to the wavelength being sufficiently small. However, such classical homogenization theories break down in the high-frequency or stop band regime whereby the wavelength to pitch ratio is of order one. Furthermore, arrays of inclusions with Dirichlet data lead to a zero-frequency stop band, with the salient consequence that classical homogenization is invalid. Higher-frequency phenomena are of significant importance in photonics (transverse magnetic waves propagating in infinite conducting parallel fibres), phononics (anti-plane shear waves propagating in isotropic elastic materials with inclusions) and platonics (flexural waves propagating in thin-elastic plates with holes). Fortunately, the recently proposed high-frequency homogenization (HFH) theory is only constrained by the knowledge of standing waves in order to asymptotically reconstruct dispersion curves and associated Floquet–Bloch eigenfields: it is capable of accurately representing zero-frequency stop band structures. The homogenized equations are partial differential equations with a dispersive anisotropic homogenized tensor that characterizes the effective medium. We apply HFH to metamaterials, exploiting the subtle features of Bloch dispersion curves such as Dirac-like cones, as well as zero and negative group velocity near stop bands in order to achieve exciting physical phenomena such as cloaking, lensing and endoscope effects. These are simulated numerically using finite elements and compared to predictions from HFH. An extension of HFH to periodic supercells enabling complete reconstruction of dispersion curves through an unfolding technique is also introduced.

Loop filters as resonant elements for acoustic metamaterials and stop band structures

Two geometries of acoustic loop filters side-loaded onto waveguides are explored using audio-frequency impulse response measurements. Finite element modeling is used to elucidate the interference mechanisms in each loop filter configuration. These simulations also yield transmission amplitude results, which are in good agreement with those determined experimentally. The ability to create broad forbidden transmission regions is demonstrated by the use of a sub-wavelength spaced series of slightly detuned filters. Finally, the phase information from the impulse response measurements is analyzed to show that regions of negative bulk modulus exist at frequencies in the vicinity of the loop interference minima.

A SIMPLE SYNTHESIS TECHNIQUE OF SINGLE-SQUARE-LOOP FREQUENCY SELECTIVE SURFACE

In this manuscript, a simple synthesis method of single square loop frequency selective surface (SSLFSS) is discussed, which may flnd the suitable application in the fast analysis and fabrication of the frequency-selective surface. The presented technique is used to design SSLFSS at 3GHz, 15GHz, 22GHz and 26GHz. At every frequency of interest, the analytical result is very close to the required result. Moreover, a way to control the re∞ection at any frequency is discussed, which may flnd an application in controlling the re∞ection level at any frequency. However, we have proposed two simple, cheaper and lightweight structures at 3GHz and 22GHz for the application in various satellite communications. The proposed process has been extended to the analysis of bandpass structure and desired results have been achieved, which indicates the utility of the method of synthesis of both the bandpass and bandstop structures.

Design of Multilayer Dual-Band BPF and Diplexer with Zeros Implantation Using Suspended Stripline

In this paper, a dual-band bandpass filter (BPF) of multilayer suspended stripline (SSL) structure and an SSL diplexer composed of a low-pass filter (LPF) and a high-pass filter (HPF) are proposed. Bandstop structure creating transmission zeros is adopted in the BPF and diplexer, enhancing the signal selectivity of the former and increasing the isolation between the diverting ports of the latter. The dual-band BPF possesses two distinct bandpass structures and a bandstop circuit, all laid on different metallic layers. The metallic layers together with the supporting substrates are vertically stacked up to save the circuit dimension. The LPF and HPF used in the diplexer structure are designed by a quasi-lumped approach, which the LC lumped-elements circuit models are developed to analyze filters' characteristics and to emulate their frequency responses. Half-wavelength resonating slots are employed in the diplexer's structure to increase the isolation between its two signal diverting ports. Experiments are conducted to verify the multilayer dual-band BPF and the diplexer design. Agreements are observed between the simulation and the measurement.

Broad-Band E-plane Filters With Improved Stop-Band Performance

In this letter, a novel broad-band E-plane filter with improved stop-band performance is proposed. The spurious pass bands commonly encountered with standard E-plane filters are suppressed by integrating band-stop structures into the coupling elements of the filter and are realized by fin-line post structures. By optimizing the geometry of fin-line post structure, the proposed filter achieves improved stop-band performance and wide bandwidth simultaneously without any associated increase in the manufacturing complexity. The simulated and experimental results are presented to validate the proposed filter.

Tunable coplanar waveguide band-stop and band-pass filters based on open split ring resonators and open complementary split ring resonators

In this study, the authors show that open split ring resonators (OSRRs) and open complementary split ring resonators (OCSRRs) can be loaded with varactor diodes in order to implement tunable filters in coplanar waveguide (CPW) technology. By loading a CPW with shunt-connected varactor-loaded OSRRs, a band-stop filter with tunable central frequency results. The electronically tunable band stop can be switched to a pass band by replacing the shunt resonators with varactor-loaded OCSRRs. To illustrate the possibilities of the approach, a tunable band-stop filter and a tunable band-pass filter have been designed and fabricated. The measured characteristics are in good agreement with the co-simulations (electric and electromagnetic) and with the circuit simulations of the electric model. The measured tuning range is roughly 120% for the stop-band structure (for varying voltages between 0 and 28 V) and over 30% for the band-pass filter (for varying voltages between 5 and 25 V).

A Novel Low-Pass Filter With an Embedded Band-Stop Structure for Improved Stop-Band Characteristics

This letter presents a novel design of a microstrip low- pass filter (LPF) with an embedded band-stop structure, which is constructed from a simple two transmission line band-stop filter. The band-stop structure is ingeniously embedded into a classical step-impedance microstrip LPF. The stop-band of the proposed LPF is more than two times broader than the original design, while its cut-off frequency remains at 1.8 GHz. The embedded structure does not increase the physical dimension of the LPF, but improves the performance significantly. Measured results agree with simuAcircnot lation well, and validate the dual-frequency design method.

Varactor-tuned quarter-wavelength dual-bandpass filter

A tunable dual-band bandpass microstrip filter is proposed and presented. It is composed of two pairs of quarter-wavelength transmission line resonators and two bandstop structures made of open stubs. Each operation bandpass frequency, denoted by f 1 and f 2 , is generated by a pair of coupled resonators. The first coupled resonator is fed via a tap-coupled structure, while the second is fed through a coupling structure. The tunability of each bandpass and harmonic suppression is achieved by modifying the electrical length of the resonators and the electrical length of the open stubs by using varactor-diode capacitors. Finally, a 2.5 and 4.25 GHz dual band bandpass filter is designed, fabricated and measured as one example and a tunability of 22.2% and 19.6%, respectively, is obtained for the first and second bands. These excellent experimental results validate the proposed structure and design technique for dual-band bandpass filters.

Design of Band-Notched UWB BPF with Very Wide Upper Stopband Using Combined λ/4 TSSIR

In this paper, a new band-notched UWB BPF with a very wide upper stopband is designed using a λ/4-type multi-mode resonator (MMR). The proposed MMR, being formed by combining two identical λ/4 tri-section stepped-impedance resonators (TSSIRs) in a structure-shared fashion, exhibits both λ/4 and embedded λ/2 types of resonance with a relatively smaller circuit size. By properly locating the first four resonant modes of the MMR and the coupling peaks of the input/output parallel-coupled lines, a five-transmission-pole UWB BPF is realized with a favorable uniform in-band UWB response. Besides the good UWB performance, a 5-GHz notched band is created by embedding in the output feed line a T-shape lumped-element bandstop structure to reject the influence from WLAN signals. Also, a very wide upper stopband is achieved by implementing a compact bandstop filter structure in the input feed line together with the properly located transmission zeros generated by the input/output interdigital-coupled lines and the second harmonic of the T-shape bandstop structure. A prototype of the proposed UWB BPF was fabricated and measured for performance verification. The measured results show a return loss of higher than 10 dB, a minimum insertion loss of 0.41 dB, and a group delay variation of less than 0.11 ns in the UWB passband except the notch. The notched band has a 3-dB bandwidth of 18%. The measured upper-end –20-dB stopband ranges from 11.94 to 30.56 GHz, with a bandwidth of 18.62 GHz.