Stopband Range Research Articles

A Wide Stopband Dual-notched Bands UWB Filter Based on A Novel Composite Right/left Handed Transmission Line

Background:: As one of the key components of ultra-wideband (UWB) system, UWB filter has important research significance. However, the current UWB filter still has the problem of a narrow stopband and cannot suppress the interference signals in the passband Objective:: In this paper, a novel UWB bandpass filter is proposed, which has wide stopband characteristics and good out-of-band rejection performance and implements a notch function for the WLAN band and the X satellite communication band in the passband to improve the antiinterference performance. Method:: The filter adopts a novel composite right/left handed transmission line (CRLH-TL) structure to realize the passband characteristics with low insertion loss (< 0.8dB). The anticoupled line structures generate two transmission zeros (TZs) in the upper stopband, which improves the upper stopband performance of the filter. The short circuit step impedance resonators (SIRs) and the asymmetric coupling structure generate a notched band in the passband respectively. Results:: The simulated and measured results show that the 3dB passband range is 3.4-11.0 GHz, the out-of-band rejection is more than 20 dB in the stopband range of 12.8-28 GHz, and the dualnotched bands are located at 5.86 GHz and 8.0 GHz respectively. The measured results are basically consistent with the simulated results. Conclusion:: Compared with the existing filters, the proposed filter has outstanding advantages and has a wide range of application prospects in the field of indoor UWB positioning system.

Narrow bandpass filter with ultra-wide stopband in a hybrid metal-optical Tamm state structure

Narrow bandpass filters (NBPF) play an important role in quantum communications, optical biometrics and other fields. However, traditional narrow bandpass filters have limited stopband capabilities. Here, an ultrawide stopband narrow bandpass filter is realized by combining a metal layer with a distributed Bragg reflector (DBR) structure to simultaneously excite the upper and lower Tamm plasma polarization (TP) modes. Numerical simulations show that the transmittance of the filter exceeds 94 % at a wavelength of 1.55 μm with a full width at half maximum (FWHM) of 8 nm. In addition, the addition of metal layer Ge reduces the electric field intensity of the lower DBR structure, effectively reducing the side peak, making the filter stopband range reach 1 μm–20 μm, which is 32 times that of traditional NBPF. Our research results provide a method to obtain narrow-band optical signals from ultra-broad and strong background noise, which facilitates the field of quantum communication.

Compact lowpass filter with vast out-of-band rejection utilizing DGS

A unique low-profile microstrip lowpass filter (LPF) is introduced. It features a broad range of stopband and sharp roll-off. The suggested LPF is built utilizig a T-shaped configuration which includes a stub for resonance and utilizes open stubs as attenuator cells. To further improve the stopband, a double circular ring is engraved into the ground plane. The developed filter features a cut-off frequency of 3 dB at 3.4 GHz, a roll-off rate of 108 dB/GHz, and a stopband range from 3.7 to 22.8 GHz. The attenuation is less than −20 dB. The prospective LPF is designed using a lumped LC circuit model and validated using Keysight Advanced Design System (ADS) simulation and theory. The final design is realized using RT/Duroid 4003C, which boasts a small footprint of 12.4mm×8.69mm×0.8mm. The modelling findings and measurements of the suggested LPF are in fairly good agreement.

Realization of a Wide Stopband Filter Using the Weakest Electric Field Method and Electromagnetic Hybrid Coupling Method

To enhance filter performance in terms of stopband, we propose a wide-stopband substrate-integrated waveguide filter based on the rejection of higher-order modes. The filter establishes the inner and outer coupling windows at the mode’s weakest electric field to achieve mode suppression. Simultaneously, we employ the electromagnetic hybrid coupling theory to analyze the electromagnetic distribution of the particular modes and determine the dimensions of the coupling circular apertures and slits based on the extracted coupling coefficients to attain suppression of the specific modes. The filter successfully suppresses all higher-order modes having resonant frequencies below that of the TE150 mode, as demonstrated by simulation results. We conducted measurements and found that the filter has a center frequency of 4.78 GHz, a bandwidth of 100 MHz with a -3 dB attenuation, and a stopband of -25 dB that extends up to 16.62 GHz (i.e., 3.48 times the center frequency). Simulation and measurement results demonstrate a good correlation. This method, compared to other SIW filters, is easy to design, has a wider stopband range, can be readily applied to practical microwave communication systems, and has potential applications.

Peculiarities of Eu3+ Photoluminescence in Opal Photonic Crystal Films and Heterostructures Based of Them

Single opal films and heterostructures based on them grown by the method of vertically moving meniscus are characterized by the reflection spectroscopy technique and then impregnated with the Eu(CH3COO)3 × H2O salt. The suppression of the Eu3+ ion emission in single opal films is clearly detected within the photonic stop-band range. The weaker manifestation of this effect in heterostructures is more likely due to interface defects causing both the appearance of permitted states in the photonic stop band and the scattering of radiation in the direction of observation. With the further impregnation of opal films with glycerol to reduce the dielectric contrast from 1.85 to 1.13, the emission spectrum is mainly determined by the Eu3+ coordination environment effects accompanied with the broadening of bands and the spectral intensity redistribution.

Reflective nonlinear optical limiter design based on coupled Tamm plasmon polaritons and optical Kerr effect

With the increasing applications of high-power lasers in fields such as laser fabrication, laser measurement, laser therapy and scientific research, there is an increasing demand for high-performance nonlinear optical limiters (NOLs) to protect human eyes and optical sensitive elements. Here we propose a brand-new approach to design a reflective NOL with an ultra-wide stop band based on coupled Tamm plasmon polaritons (TPPs) and optical Kerr effect. The NOL permits the transmission of weak signal light at the desired wavelength while effectively blocking potentially harmful or accidentally intense lasers at the same wavelength to avoid damage to sensitive optical elements or human eyes. The design can be optimized for the desired operating wavelength and threshold intensity by using different dielectric layers. In a proof-of-concept design, taking the 1064 nm laser as an example, we design a NOL capable of dynamically adjusting its transmission in response to laser intensity. The NOL has a high transmission of 85.21 % at weak light (intensity less than 0.20 MW/cm2), and the transmission can be rapidly reduced to 1.39 % when the incident light intensity increases to 60.37 MW/cm2. Furthermore, the broad stop band effectively safeguards the limiter from potential damage caused by intense light at different wavelengths. Our proposed limiter exhibits an exceptionally wide stop band range spanning from 0.5 ∼ 20 µm, nearly 30 times broader than conventional reflective NOLs. The proposed NOL design scheme provides a new promising method to design an excellent reflective NOL at the desired wavelength.

A Power-Based Framework for Quantifying Parameter Uncertainties in Finite Vibroacoustic Metamaterial Plates.

Vibroacoustic metamaterials (VAMMs) are artificial materials that are specifically designed to control, direct, and manipulate sound waves by creating a frequency gap, known as the stop band, which blocks free wave propagation. In this paper, a new power-based approach that relies on the active structural intensity (STI) for predicting the stop band behavior of finite VAMM structures is presented. The proposed method quantifies the power loss in a locally resonant finite VAMM plate in terms of percentage, such as STI99% and STI90%, for stop band prediction. This allows for the quantitative analysis of the vibration attenuation capabilities of a VAMM structure. This study is presented in the context of a two-dimensional VAMM plate with 25 resonators mounted in the middle section of the plate. It has been demonstrated that this method can predict the stop band limits of a finite VAMM plate more accurately than using negative effective mass, unit cell dispersion analysis, or the frequency response function methods. The proposed approach is then implemented to establish a framework for investigating the influence of parameter uncertainties on the stop band behavior of the VAMM plate. Based on the STI99% method, which aims for significant vibration reduction, stricter tolerances in the mass fabrication process are required to ensure the robustness of VAMM. Conversely, the STI90% method suggests that larger fabrication tolerances can be leveraged to achieve a broader stop band range while still meeting the desired performance level, leading to cost savings in manufacturing.

High-Order Quasi-Elliptic-Type Wideband Bandpass Filter With Ultrabroad Input-Reflectionless Stopband Range

A two-layer wideband bandpass filter (BPF) with ultrabroad input-reflectionless stopband range is reported. It consists of a two-port-reflectionless high-order quasi-elliptic-type (QET) wideband BPF and two similar input-reflectionless low-pass filter (LPF) stages. The constituent 2-GHz BPF is shaped by two vertical transitions with shunt resistively terminated T-junctions, which are connected through a microstrip T-junction. It features a two-port-absorptive ninth-order in-band quasi-equiripple BPF response with two close-to-passband transmission zeros (TZs). The building LPF is made up of two in-series-cascaded input-reflectionless LPF units with their first TZs at 6 and 12 GHz, which results in an extended upper stopband beyond 18 GHz. Through this LPF-BPF-LPF approach, an extremely wide input-reflectionless stopband range with increased power attenuation levels in the overall BPF is attained. Its theoretical RF operational principles are detailed. Furthermore, for experimental validation purposes, a two-layer microstrip wideband BPF prototype is simulated, manufactured, and measured. It exhibits a minimum stopband power attenuation level of 29.57 dB, along with minimum input-power-matching levels of 10 and 6.7 dB from dc to 9.85 GHz and from dc to 20 GHz, respectively.

A low profile cylindrical cavity dual-band bandpass filter with short-circuited metal pillars

This paper presents a low profile cylindrical cavity quadruple-mode dual-band bandpass filter. Five short-circuited metal pillars are loaded in a cylindrical cavity to change the electric field distributions of the original resonant modes. The changed TM010 mode and TM110+ mode form the first passband, and the changed TM110- mode and TM210+ mode form the second passband. The center frequencies of the two passbands are 3.05 GHz and 3.59 GHz, with relative bandwidths of 1.72% and 2.5%, respectively. The first passband can be adjusted independently, and the stopband range of the proposed bandpass filter is relatively wide. By using the degenerate modes, two transmission zeros are introduced to improve the selectivity of the proposed bandpass filter. The use of TMmn0 mode effectively reduces the height of the cavity. The fabricated cavity bandpass filter is measured, and the measured results are accordance with the simulated ones.

Effects of randomness and piezomagnetic coupling on the appearance of stop-bands in heterogeneous magnetorheological elastomers

Phononic crystals (PCs) consist of a periodic arrangement of inclusions in a matrix material, and have garnered a great deal of interest owing to a phenomenon known as band gap frequencies in which particular frequency ranges are not able to propagate through the PCs. The aim of this work is to study the effects of magneto-elastic coupling and other parameters such as randomness in geometrical properties, volume fraction and size of inclusions on longitudinal wave propagation and, in particular, on the appearance of stop-band frequencies. The results indicate that the most important parameters deciding whether a frequency is in a stop-band or a pass-band are the randomness in geometrical properties and piezomagnetic coupling. It was observed that piezomagnetic coupling can lead to a widening of the first stop-band range for a periodic microstructure. Moreover, while randomness in particle size leads to a stop-band range and reduced wave transmission in the second pass region, randomness in particle position leads to removal of the pass band ranges compared to periodic structures. Additionally, the influence of piezomagnetic coupling becomes insignificant in fully random structures.

Patterned dielectric mirrors for uniformly high reflection in polarized light

Two types of multilayered dielectric mirrors with high reflection in the visible range are fabricated on line-patterned substrates using a suitable combination of cost-effective soft lithography and RF magnetron sputtering. They are characterized at different visible wavelengths lying outside and inside their stopband range. Their response to linearly polarized incident light depends on the wavelength, angle of incidence, and the direction of orientation of the patterned lines on the substrate with respect to the direction of polarization. A comparison of these broadband high reflectors on patterned substrates with that of equivalent high reflectors on planar substrates confirmed that the patterned high reflectors have a much higher uniformity in their reflectance value when the polarization direction of incident light is changed, both within and outside their stopband range, even at oblique angles of incidence. These broadband high reflectors are useful in applications that require uniformly high reflection even while there are changes in wavelength, polarization and the angle of incidence.

A Wideband Balun Filter Based on Folded Ring Slotline Resonator and Dual-Feedback Stubs With >17.8 f 0 Stopband Rejection

This brief proposes a wideband balun filter with ultrawide stopband utilizing a shunt slotline coupled with a folded ring slotline resonator (FRSR) and dual-feedback stubs (DFS). Utilizing the FRSR, there are four transmission poles (TPs) within the passband and ten transmission zeros (TZs) in the range of < 20 GHz generated, which contribute to large bandwidth, high selectivity, and >10-dB harmonic suppression. In addition, the two additional TZs generated by the DFS can improve the harmonic suppression to >18 dB. In the meantime, the folded slotline design effectively reduces the size of the proposed balun filter to 33.2% of the conventional round slotline ring. The fabricated balun filter demonstrates a 111% fractional bandwidth (FBW) centering around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{0}$ </tex-math></inline-formula> of 2.25 GHz, a measured stopband up to 40 GHz (17.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{0}$ </tex-math></inline-formula> ) with a minimum rejection level of 18 dB, and a shape factor of 1.3. To the best of the authors’ knowledge, both the fractional bandwidth and stopband range achieved by the balun filter are among the best.

A bandwidth enhanced multilayer electromagnetic bandgap structure to reduce the simultaneous switching noise

&lt;abstract&gt; &lt;p&gt;A bandwidth enhanced multilayer Electromagnetic Band Gap (EBG) structure to reduce the simultaneous switching noise (SSN) in high frequency operating circuits, which useful for the satellite communication application, is presented in this paper. A proposed stack structure is mathematically analyzed by the dispersion method and transmission matrix method. Simulation results show good mitigation of SSN in scattering parameters and signal integrity in terms of eye diagrams. We have also checked for power integrity analysis using self-impedance. The proposed structure gives a good SSN suppression at -30 dB from 817 MHz to 26.32 GHz, around 25.50 GHz bandwidth and also reduces the cavity mode resonance within the stopband range. The proposed multilayer structure is compared with planar EBG plane and reference board. It is also compared with published results.&lt;/p&gt; &lt;/abstract&gt;

High-Order Balanced Superconducting Filter With High Selectivity, Low Insertion Loss, and Wide Stopband Range For Radio Astronomy

In this paper, a newly shunted-line stepped-impedance resonator (SLSIR) is studied and applied to realize high-order balanced filter design for radio astronomy application. The proposed SLSIR not only has more flexible control of the internal coupling between adjacent units but also provides more design freedom for the cascade connection of high-order filter. Then, the operating theory of three kinds of electrically, magnetically, and electromagnetically coupled SLSIR pairs has been discussed and utilized to high-performance filter design. Hence, fourth-order balanced filter using electromagnetically coupled SLSIR pairs is investigated and designed, which exhibits an excellent filtering performance under differential-mode (DM) operation as well as a high common-mode (CM) suppression level. In addition, the production mechanism of DM transmission zero is modeled and analyzed. Based on the analysis above, two dissimilar types of coupled SLSIR pairs with the same fundamental frequency but different harmonics are adopted to design an eighth-order balanced filter. Finally, the high-order balanced filter is fabricated on 0.5-mm-thick MgO wafer with double-sided YBCO thin films. Measured results show that the eighth-order balanced filter operates at 2.53 GHz with the corresponding in-band insertion loss of 0.1 dB. Results well verify the proposed structure with high selectivity, low insertion loss, and wide stopband performances.

Slotline-Based Balanced Filter With Ultra-Wide Stopband and High Selectivity

Slotline-based balanced filter with ultra-wide stopband is proposed in this brief. The proposed balanced filter integrates split-ring slotline resonators (SRSRs) and $\pi $ -type slotline structures, which not only increase the selectivity, but also enhance suppression in a stopband range of 7.1 times as large as center frequency. The SRSRs are implemented by two symmetrically folded stepped-impedance resonators and used as a second-order resonant circuit to obtain high-selectivity bandpass response. Moreover, the $\pi $ -type slotline structure enhances harmonic rejection significantly. The fabricated balanced filter demonstrates an insertion loss of 1.07 dB @ ${f} _{0}$ (3.5 GHz), a differential-mode (DM) stopband suppression of 20 dB @ up to 7.1 ${f} _{0}$ , a common-mode (CM) suppression of 40.5 dB over the passband. To the best of the authors’ knowledge, with maintaining competitive in-band performances, the proposed balanced filter achieves the widest stopband suppression.

Wideband filtering power divider with wide rejection bandwidth and isolation

A wideband filtering power divider (FPD) with wide rejection bandwidth and good isolation is presented, based on conventional Wilkinson structure. Parallel coupled lines and two pairs of open-circuit stubs are used for achieving bandpass filtering response and enhancing the performance of the rejection bandwidth. Furthermore, by properly choosing two resistors between two pairs of open-circuit stubs allows good isolation performance. Measured results indicate that the FPD operates at 2.35 GHz ( f 0 ) with a − 20 dB bandwidth of 55.3%. In the upper stopband range from 3.7 to 8.8 GHz (3.74 f 0 ), the minimum rejection is 20 dB. Within working band, the isolation between the output ports is higher than 24 dB. In addition, ultra-wide isolation better than 20 dB from DC to 10 GHz is obtained.

Band-pass Filter with Harmonics Suppression Capability

&lt;span&gt;This paper presents a Band-pass Filter (BPF) with a very wide suppressions band. The filter design is based on a modified U-shaped slot. Two pair of U-shaped slots is used to ensure that the filter can suppress the unwanted frequencies up to 4&lt;sup&gt;th&lt;/sup&gt; harmonics. In order to achieve sharp skirt, two transmission zeroes are created near the passband area. Additional transmission zeroes are introduced to deepen the stopband area. Therefore, the passband range starts from 1.3 to 3.3 GHz and the stopband range from 3.3 GHz up to 9 GHz are achieved. The filter performances are verified through simulated and measured results.&lt;/span&gt;

Compact continuous tunable low-pass filter with high selectivity and wide stopband

This letter presented a novel compact continuously tunable low-pass filter (LPF) using varactor-loaded coupled rhombic stubs. The proposed LPF demonstrated excellent roll-off selectivity, wide stopband range as well as good cut-off frequency tunability. This LPF consisted of three varactor-tuned coupled rhombic stubs loaded on a section of high-impedance microstrip line symmetrically and two coupled line LPFs which could further improve the stopband performance. A detailed explanation of the tuning mechanism was illustrated by adopting lumped-element equivalent circuit model. The measured results showed not only a wide cut-off frequency tuning range of 56% from 350 to 800 MHz, but also an excellent steepness factor of less than 1.14. Additionally, a rejection level of greater than 20 dB up to 8 GHz (>10 fc) was observed in the stopband. The proposed ideas were verified by the measured results. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1641–1644, 2016

Sunlight-like white organic light-emitting diodes with inorganic/organic nanolaminate distributed Bragg reflector (DBR) anode microcavity by using atomic layer deposition

White organic light-emitting diodes (WOLED) with inorganic/organic/hybrid nanolaminate distributed Bragg reflector (DBR) prepared by atomic layer deposition (ALD) has been firstly developed, and the improved structural, optical, and electrical properties have been observed. The functional layer consists of periodically alternating layers of ZrO2/Zircone (zirconium alkoxides with carbon-containing backbones) films fabricated using ALD. By well adjusting the thickness and emissive dyes of the emission layer, three white light diodes were realized based on three cavity modes with different resonance wavelength and intensity. The narrowed lectroluminescent (EL) spectra from the microcavity organic light emitting diodes (MOLEDs) are of high-purity, and the off-resonant optical mode is highly suppressed due to the excellent optical properties of the DBR layers with high reflectivity in a wide stop-band range. The CIE chromaticity coordinates of devices are tuned from (0.33, 0.34), (0.43, 0.40) to (0.57, 0.40), which are all on the planckian locus, and the color temperature is adjusted from 5783 K, 3842 K to 2245 K. This work exhibits a simple and novel approach to achieve a sunlight-like WOLED by constructing the inorganic/organic nanolaminate DBR using ALD, which will be very important for healthy display and lighting.

Research and Validation of Pipe Acoustic Transmission Mechanism

During oil production an acoustic communication mode with downhole oil pipe as channel is one of feasible downhole control method. Based on a mechanism analysis, this paper presents a pipe acoustic transmission mechanism model. The model is derived to obtain a pipe dispersive equation. The simulation of phase velocity, group velocity and dispersion curves of three common oil pipes indicates that spectral distribution of longitudinal wave transmission in pipe presents a comb filter structure, and the passband/stopband distribution approximates periodicity and symmetry on spectrogram. The passband range, stopband range and amplitude value changes with length, cross area, density of oil pipe and joint. And the influence rule is given. Then the optimal frequency is suggested through simulation for downhole wireless communication tools design.