Band-pass Filtering Properties Research Articles

Single-Conductor Spoof Surface Plasmon Polaritons Transmission Line With Bandpass Feature Based on Embedded Cross-Shaped Resonators

In this brief, cross-shaped resonators (CSRs) are integrated in spoof surface plasmon polaritons (SSPPs) unit, and a novel compact single-conductor SSPPs transmission line (TL) with bandpass feature is proposed. In this design, a unit structure based on classical SSPPs structure embedded with a CSR is proposed. To analyze the proposed unit structure, scattering parameters and ABCD-matrix theories are used. After the theoretical analysis, a SSPPs TL with bandpass filtering property is designed. The simulated passband is from 7.9 to 12.2 GHz with a relative bandwidth of 42%. A prototype is fabricated and measured. The measured results are in agreement well with the simulated ones. This proposed structure is attractive and useful for the design of high integrated SSPPs circuits.

Intracavity filtering in SESAM mode-locked fiber lasers: soliton effects and noise performance.

We characterized and analyzed the effect of intracavity spectral filtering in the Er:fiber laser mode-locked with a semiconductor saturable absorber mirror (SESAM). We studied the dispersive properties of bandpass filters and their influence on the characteristics of generated soliton pulses. Our analysis showed that various sideband structures were induced by the filter dispersion profiles and shaped through the interaction of the soliton with the dispersive wave. In addition, intracavity filtering improved the intensity and phase noise of the laser significantly, and we showed optimal filtering conditions for both types of noise. By adding a 10 nm bandpass filter to the laser resonator, the intensity and phase noise were improved 2- and 2.6 times, respectively.

Селективные свойства двухрезонаторных структур и высокоизбирательные фильтры на их основе

An increase in the frequency selectivity of microstrip filters is traditionally achieved by forming transient response zeros at final frequencies. In this case, the specified requirements for the selectivity of filters are provided with a smaller number of resonators, and, consequently, lower loss es in the passband are achieved in more compact structures. Thus, the effectiveness of this approach to the synthesis of microstrip filters is determined by the number of transient response zeros that can potentially be formed in various structures. One way to form damping transient response zeros is to introduce additional cross-couplings between non-adjacent resonators. However, when synthesizing highly selective filters based on such widely used N-resonator structures, a limited number of transient response zeros equal to N-2 is formed. At the same time, two-resonator structures are known in which a much larger number of transient response zeros is formed, which is several times greater than the number of resonators in them. However, each of these structures has its own specific frequency-selective properties, which limits the scope of their wide application as universal links. The aim of this work is the synthesis of highly selective two-cavity structures with various types of frequency characteristics, which expands the scope of such structures. The frequency properties of microstrip two-resonator structures of a new type, which have broad functionality and increased frequency selectivity, are studied. It is shown that in multistage structures on two half-wave hairpin resonators, under certain conditions, a significant number of transient response zeros is formed, which is two to three times greater than the number of resonators in the filter, and parasitic transmission bands also degenerate. Depending on the ratio of the coefficients of electromagnetic interaction in different sections of the length of the coupled resonators, they acquire the properties of both single-band and multi-band bandpass filters, as well as low-pass filters. The noted features predetermine the possibility of wide application of these structures as both independent compact filters and basic units as part of higher-order filters with a significantly limited number of resonators. The results of electrodynamic 3D modeling and experimental studies of the proposed structures are presented, which are in good agreement.

An adaptive variational mode extraction method based on multi-domain and multi-objective optimization for bearing fault diagnosis

When a local fault in the rolling element bearing appears during operational running, the induced bearing vibration signal is essentially equivalent to a mixed multi-component signal, which usually includes multiple frequency components (e.g., periodic impulses, random impulses, discrete harmonics, and heavy environmental noise). This indicates that it is difficult to detect the weak periodic impulses related to bearing faults by traditional signal processing methods. Variational mode extraction (VME) as a new signal processing method with band-pass filtering properties can separate the desired periodic impulse component from the mixed multi-component signal due to its similar basis as the popular variational mode decomposition (VMD). However, the filtering performance of VME is significantly influenced by two parameters (i.e., penalty factor and center-frequency). To address this issue, all the previous work focused on single-domain and single-objective parameter optimization from the filtering signal or its envelope, whereas the objective function with a single-criterion cannot depict bearing fault signatures from the impulsiveness and cyclostationarity simultaneously in general cases. Therefore, to improve the bearing fault feature extraction ability and avoid the problem of artificial parameter selection of VME, this paper proposes an adaptive variational mode extraction method based on multi-domain and multi-objective optimization (AVME-MDMO), in which two key parameters of VME are automatically determined by multi-objective gray wolf optimizer (MOGWO) with a novel multi-objective function named integrated measure of sparsity-impact (IMSI) of square envelope (SE) and square envelope spectrum (SES). As a result, the optimal VME is employed to obtain the specific mode component and its corresponding SES for achieving bearing fault diagnosis. The effectiveness of the proposed method has been validated on simulation signal and experiment data of rolling element bearing. Besides, the comparison results demonstrate its superiority and robustness in excavating fault signatures over the VME or VMD with single-objective function, and the fast kurtogram.

Enhanced-Stopband Dual-Polarized Filtenna Without Extra Circuit for Tile Array Applications

In this communication, a dual polarized (DP) stacked patch filtenna (filtering antenna) with a wide stopband is developed for tile array applications. The bandpass filtering property is realized by improving the feeding network and patch without adding extra bandpass circuit or size. An elaborate feeding structure with complementary pair of a short-circuited stub and an open-circuited stub (CSSOS) is developed, which generates two transmission nulls effectively enhancing the selectivity and suppressing the harmonic. Moreover, CSSOS has a small size and broadens the impedance bandwidth apparently by introducing an in-band resonance. By properly etching four U-shaped slots on the driven patch, a radiation null in the upper stopband is also generated. The nulls generated by the two approaches can be adjusted independently in wide ranges. For further harmonic suppression, bandstop striplines (BSSs) with ultralow insertion loss are developed. Measured results show that the filtenna performs a wide operating band (3.10–3.95 GHz) and a wide stopband up to 8 GHz with a rejection level higher than 16 dB. Besides, a 32-element tile phased array employing the filtennas is also fabricated and measured. A compact configuration, high selectivity, and good beam steering capacity are exhibited.

Stellate cell computational modeling predicts signal filtering in the molecular layer circuit of cerebellum

The functional properties of cerebellar stellate cells and the way they regulate molecular layer activity are still unclear. We have measured stellate cells electroresponsiveness and their activation by parallel fiber bursts. Stellate cells showed intrinsic pacemaking, along with characteristic responses to depolarization and hyperpolarization, and showed a marked short-term facilitation during repetitive parallel fiber transmission. Spikes were emitted after a lag and only at high frequency, making stellate cells to operate as delay-high-pass filters. A detailed computational model summarizing these physiological properties allowed to explore different functional configurations of the parallel fiber—stellate cell—Purkinje cell circuit. Simulations showed that, following parallel fiber stimulation, Purkinje cells almost linearly increased their response with input frequency, but such an increase was inhibited by stellate cells, which leveled the Purkinje cell gain curve to its 4 Hz value. When reciprocal inhibitory connections between stellate cells were activated, the control of stellate cells over Purkinje cell discharge was maintained only at very high frequencies. These simulations thus predict a new role for stellate cells, which could endow the molecular layer with low-pass and band-pass filtering properties regulating Purkinje cell gain and, along with this, also burst delay and the burst-pause responses pattern.

Switchable Terahertz Band-Pass/Band-Stop Filter Enabled by Hybrid Vanadium Dioxide Metamaterial

To date, little research has been carried out on the integration of switchable and diversified functionalities into a single metamaterial in the terahertz (THz) range. Here, a hybrid vanadium dioxide (VO2) metamaterial was designed with switchable properties of band-pass filter and band-stop filter in the frequency range of 0.3–1.6 THz. Simulations demonstrated that under TE polarization, the proposed system acted as band-stop filter with the center frequency of 0.95 THz when VO2 is in the insulating state. Upon the transformation of VO2 into the metallic state, the proposed system behaved as a band-pass filter with a transmittance of >80%. The physical mechanism of the band-pass/band-stop conversion was examined by analyzing the surface current distribution of the designed device. The switchable characteristics of this structure can enable its wide application in tunable THz functional components such as amplitude modulators, polarization control, and intelligent switches.

Design and fabrication of a low-loss microstrip lowpass-bandpass diplexer for WiMAX applications

This work presents a compact low-pass-bandpass microstrip diplexer with a novel configuration. It consists of a lowpass filter integrated with a bandpass filter via a simple compact junction. The proposed bandpass filter consists of four rectangular patch cells and some thin strips. The step impedance structures, with a radial cell, are applied to achieve a lowpass frequency response. The lowpass channel of the introduced diplexer has 2.64 GHz cut-off frequency, whereas, the bandpass channel center frequency is 3.73 GHz for WiMAX applications and covers the frequencies 3.31 GHz to 4 GHz. In addition to having novel structures, both filters have other advantages in terms of high return loss, low insertion loss and high selectivity. The presented microstrip diplexer has the compact size of 29 mm × 13.8 mm × 0.762 mm, calculated at 2.64 GHz. The obtained insertion losses are 0.20 dB (for the first channel) and 0.25 dB (for the second channel), which make the proposed diplexer suitable for energy harvesting. The stopband properties of both bandpass and lowpass filters are improved by creating several transmission zeros. The comparison results show that the lowest insertion losses, the minimum gap between channels, good return losses, and good isolation are obtained.

Improvement and coordination of spectral and mechanical properties of bandpass filter on silicon substrate for the infrared range

Infrared (IR) film systems can accumulate considerable stress due to their large thickness. In addition, the thermal stress of the films will further increase due to a significant difference in thermal expansion coefficient between the film materials and the substrate. Stress accumulation limits the passband transmittance of the 2.76 to 3.04 μm traditional IR interference filter to about 80%. To increase the passband transmittance and guarantee the mechanical properties, four kinds of samples were designed, prepared, and measured. Through matching the film systems and proposing an alternative deposition method, high-performance IR bandpass filters with an average transmittance of 92.2% have been prepared. The improved transmittance provides a necessary study of developing IR systems and improving imaging quality.

In-Lens Band-Pass Filter for Secondary Electrons in Ultrahigh Resolution SEM.

Scanning electron microscopes come equipped with different types of detectors for the collection of signal electrons emitted from samples. In-lens detection systems mostly consist of several auxiliary electrodes that help electrons to travel in a direction towards the detector. This paper aims to show that a through-the-lens detector in a commercial electron microscope Magellan 400 FEG can, under specific conditions, work as an energy band-pass filter of secondary electrons that are excited by the primary beam electrons. The band-pass filter properties verify extensive simulations of secondary and backscattered electrons in a precision 3D model of a microscope. A unique test sample demonstrates the effects of the band-pass filter on final image and contrast with chromium and silver stripes on a silicon substrate, manufactured by a combination of e-beam lithography, wet etching, and lift-off technique. The ray tracing of signal electrons in a detector model predicate that the through-the-lens detector works as a band-pass filter of the secondary electrons with an energy window of about 3 eV. By moving the energy window along the secondary electron energy spectrum curve of the analyzed material, we select the energy of the secondary electrons to be detected. Energy filtration brings a change in contrast in the image as well as displaying details that are not otherwise visible.

Characterization of TlInS1.8Se0.2 as advanced functional crystals

In this work, selenium doped TlInS1.8Se0.2 crystals are used to fabricate multifunctional devices that can handle more than one duty at a time. After revealing the morphological, compositional, structural and optical properties of the doped crystal, it is sandwiched between Ag and carbon metals. The crystals are characterized by means of ultraviolet-visible light spectrophotometry, impedance spectroscopy and illumination dependent current-voltage characteristics techniques. While the optical spectroscopy allowed determining the energy band gap of the crystals as well as the optical conductivity in the terahertz frequency domain, the impedance spectroscopy allowed identifying the conductance and reflectance spectra in the gigahertz frequency domain. The two techniques reveal promising characteristics presented by optical switching at 2.20 eV and band pass filtering properties in mega/gigahertz frequency domains. On the other hand, the analysis of the current (I)- voltage (V) characteristics which are recorded in the dark and under photoexcitation of unfiltered tungsten light in the light power range of 25–130 mW, revealed light intensity dependent rectifying properties. Particularly, the modeling of the experimental I-V curves in accordance with the Richardson Schottky and Chueng's theoretical approaches have shown that the Schottky diode ideality factor, series resistance and barrier height decreases with increasing light power. Such behavior indicates wide tunability of the device when used as photosensors. With the features presented by small size, photosensitivity, gigahertz/terahertz spectral responses, the device can be promising element for use in visible light and microwave communications.

Investigation of frequency-selective properties of microwave wideband bandpass filters

A new approach allowing to improve frequency-selective properties for a fixed order of N filter is suggested. In all the studies, conducted with the help of numerical electrodynamic analysis of 3D models of microstrip filters based on a multimode resonator, the same substrate with dielectric constant ε=2.8 and thickness h=2 mm (material - FLAN) was used in calculations. The central bandpass frequency of microwave structures f0≈1.4 GHz was registered and as well as relative bandwidth Δf/fo≈80%. The strip conductor of central multimode resonator in six studied filters of the sixth and eighth orders has the shape of an irregular meander being electromagnetically connected with four single-mode resonators, a pair of which is located to the left of it, and the other pair is to the right. It is shown that in single-mode quarter-wave resonators building-up the number of portions of identical parallel strip conductors, connected to a screen at one end and connected with each other by a strip conductor jumper, can increase the power of suppression at low-frequency stop band by more than 15 dB, as well as near high-frequency slope of passband by more than 10 dB. Therefore, the level of maximums of return losses in the passband of wideband bandpass filter ranges within a few dB.

Free-standing double-layer terahertz band-pass filters fabricated by femtosecond laser micro-machining.

We report on the fabrication and transmission properties of free-standing single-layer and double-layer THz bandpass filters. These filters are fabricated on aluminum foils using femtosecond laser micro-machining. The aluminum foils are periodically patterned with cross apertures with a total area of 1.75×1.75 cm2, also known as frequency-selective surfaces. Their terahertz transmission properties were simulated using the FDTD method and measured using a time-domain terahertz spectroscopy system. The simulation results agree with the measurements results very well. The performance of single-layer bandpass filters is as good as the commercial equivalents on the market. The double-layer filters show extraordinary transmission peaks with changing spacing between the two layers. We show the contour map of the electric field distribution across the apertures, and ascribe the new transmission peaks to the interference and coupling of surface plasmon polaritons between the two layers.

Design and implementation of combline bandpass tunable filter using barium-strontium-titanate thin-film capacitors

ABSTRACTThe design, fabrication and microwave properties of tunable fifth-order combline bandpass filter using etched barium-strontium-titanate (BST) thin films on sapphire (0001) substrates were investigated. At 1 MHz and 1000 kV/cm electric field, the dielectric tunability, the remanent polarization (2Pr) and the coercive electric field (2EC) of BST films were 45.96%, 2.26 µC/cm2 and 81.83 kV/cm, respectively. The loss tangent was 1.36% at zero electric field. After the BST parallel plate capacitors characterization, BST capacitors were loaded at the end of parallel coupled resonators in the design of the tunable filter. With the application of 20 V DC voltage, the center frequency of the filter varied from 1.17 GHz to 1.34 GHz which corresponds to a relative shift of 13.5%.

Vias and Stubs Loaded Patch and Its Applications in Filter and Rectifier Designs

It is always advantageous to include additional bandpass filtering functionality within different circuits and components in the wireless communication system, and thus, a novel circular patch loaded with vias and stubs is proposed as the basic element to achieve this function integration, as well as the performance enhancement. Owing to the introduction of a new operation mode and flexibility of the proposed patch element in locating the frequencies of different operation modes, excellent bandpass characteristics can be implemented with simplicity in structure. First, the proposed patch element is used to implement a triple-mode bandpass filter with a very wide harmonic suppression. As an extension, a novel rectifying circuit with extended input power range and bandpass filtering property is implemented based on a bandpass filtering power divider, which is also implemented using the basic patch configuration. To verify the validity of the proposed patch configurations, three different kinds of circuits have been designed, fabricated, and measured. All measured results are found to be in good agreement with the simulation results.

Influence of biophysical properties on temporal filters in a sensory neuron

Sensory pathways implement filters that extract relevant information from the environment [1]. These filtering properties depend in intricate ways on the biophysical parameters of the underlying neuronal architecture. Understanding the link between computational aspects, such as response properties or spike statistics, and the underlying biophysics is a question that can be addressed with theoretical methods. Many primary sensory neurons operate in a mean-driven regime, where mean intensity is represented by the average firing rate, while the temporal structure of the stimulus around its mean is encoded into the particular structure of the spike train in analogy to an irregular sampler [2]. Examples of neurons applying this strategy include the paddlefish's electrosensory system [3], grasshopper auditory receptors [4], or the vestibular system of the turtle [5]. Spikes are generated from the dynamics of voltage-dependent ion channels. Different sensory neurons, however, may use different compositions of spike-generating channel types. These do not only render the cell excitable in the first place, they also have a large influence on a neuron's transfer function. In addition, some ion channels shape the subthreshold dynamics of neurons, but it is less clear, how they affect the temporal structure of spike trains when the neurons are driven tonically. Several channel types, including HCN channels, are known to cause subthreshold resonance. This property results in largest subthreshold response amplitudes of a neuron at a particular frequency, hence termed the resonance frequency. The resulting band-pass like filter properties have a strong effect on fluctuation-driven neurons. Their influence on tonic spiking, however, has been less explored. Accordingly, the influence of channels that cause subthreshold resonance, such as HCN, on sensory systems like the hair cells of the mouse inner ear is still under debate [6]. Here, we use phase-response-curve-based methods within the framework of numerical continuation to resolve whether and how the effects of these channels carry over into the suprathreshold, mean-driven dynamics. To this end, we use computational models of hair-cell mechanoreceptors [7]. Our approach is to, first, derive the phase oscillator that is input-output equivalent to the full biophysical model. Then, applying linear response theory, the transfer function can be estimated in the regime of weak-amplitude stimulation [8]. This transfer function maps time-dependent stimuli to the instantaneous firing rate. We show that the poles and zeros of the transfer spectrum are related to the Fourier components of the systems phase response curve (PRC) as well as the average intrinsic noise level, which is due to a finite ensemble of stochastic ion channels. We find that both properties (1) the PRC - a consequence of the deterministic part of the dynamical system - and (2) the intrinsic stochasticity, are affected by the presence of HCN channels. Further, we use an overall measure of information transmission, the stimulus-response information, to approximate the contribution of HCN channels to information transfer in given frequency bands.

Sound envelope extraction in cochlear nucleus neurons: modulation filterbank and cellular mechanism

Efficiently encoding sound features, e.g. temporal fine structure or envelope, is critical for perception tasks such as sound localization and identification. Whereas the auditory nerve (AN) fibers convey all information transduced at the cochlea, the pathway bifurcates in the cochlear nucleus, the first station after AN. The auditory system of the barn owl is a good example of such functional differentiation, where one subdivision of the cochlear nucleus (Nucleus Angularis, NA) is thought to encode sound intensity information used for interaural intensity difference processing whereas the other (Nucleus Magnocellularis) encodes temporal fine-structure information necessary for interaural time difference processing [1]. The fact that NA responses to frozen broadband sounds are very reproducible on a slow time-scale [2] led to think that this center is also involved in the encoding of the slow-time-varying sound envelope. By using coherence and phase-locking analysis of NA responses to amplitude-modulated broadband sounds, we show that NA indeed encodes the envelope better than AN at the cost of losing the fine -structure information. A detailed analysis of the modulation filters estimated using reverse correlation on the envelope signal shows that NA neurons low-pass or band-pass filter the envelope with time constants of an order of magnitude faster than in higher centers (e.g. [3]). Population-wide there is a heterogeneous distribution of the center frequencies of those filters that does not depend on the best frequency of the neurons. This suggests that NA could implement a bank of modulation filters, each with different center frequencies (up to 600 Hz) and bandwidths. Because the AN encodes sounds through frequency-selective channels that exhibit low-pass modulation sensitivity the question then arises as to how NA cells, receiving a few (around 5 [4]) AN inputs, can implement band-pass modulation filtering. While most existing models of such temporal modulation rely on delayed inhibition (e.g. [5]), there is no evidence of time-locked GABAergic input to NA. We therefore hypothesize this function can be based on cellular mechanisms. Using a model fitting approach [6] we show that a spiking neuron model including an adaptive threshold based on sodium inactivation [7] can predict the spike timing and the response statistics of NA neurons. In particular we hypothesize that the high-pass filtering effect of the dynamic threshold on the membrane potential, in conjunction with the low-pass filtering properties of the cell, serve as a neural substrate for implementing the observed band-pass filtering properties of AN neurons. Population heterogeneity in the model parameters, especially in the time constant of the threshold dynamics, would ensure to have a bank of filters with different frequency responses. This finding indicates that a basic cellular mechanism, in our case spike threshold adaptation, is sufficient to implement neural band-pass filtering.

Novel band-pass filters using E-shape resonators

A class of band-pass filters using E-shape resonators is proposed in this paper. The transmission and reflection property of the E-shaped resonators are analyzed with the transmission line theory. In order to verify the E-shaped resonators circuit structure and its corresponding filter design theory, the single, two-, and three-cascaded band-pass filters using E-shaped resonators are designed and simulated. The resonant characteristics of the cascaded band-pass filters show their advantages of compact size, excellent pass-band performance, and high out-band suppression. Finally, the two- and three-cascaded band-pass filters are fabricated and measured. The measured results show excellent band-pass filtering property and low insertion loss. The measured results also prove to be generally consistent with the simulated results.

Regulation of mammalian cell cycle progression in the regenerating liver

The process of cell division in mammalian cells is orchestrated by cell-cycle-dependent oscillations of cyclin protein levels. Cyclin levels are controlled by redundant transcriptional, post-translational and degradation feedback loops. How each of these separate loops contributes to the regulation of the key cell cycle events and to the connection between the G1-S transition and the subsequent mitotic events is under investigation. Here, we present an integrated computational model of the mammalian cell cycle based on the sequential activation of cyclins. We validate the model against experimental data on liver cells (hepatocytes), which undergo one or two rounds of synchronous circadian-clock gated cell divisions during liver regeneration, after partial hepatectomy (PH). The model exhibits bandpass filter properties that allow the system to ignore strong but transient, or sustained but weak damages after PH. Bifurcation analysis of the model suggests two different threshold mechanisms for the progression of the cell through mitosis. These results are coherent with the notion that the mitotic exit in mammalian cells is bistable, and suggests that Cdc20 homologue 1 (Cdh1) is an important regulator of mitosis. Regulation by Cdh1 also explains the observed G2/M phase prolongation after hepatocyte growth factor (HGF) stimulation during S phase.

A Simple Microstrip Bandpass Filter with Analytical Design Theory and Sharp Skirt Selectivity

A simple coupled-line circuit configuration is proposed to design microstrip bandpass filter with sharp skirt selectivity in this paper. This novel circuit consists of two-section coupled lines with a common connected point. An equivalent odd-mode and even-mode analysis is applied to analyze transmission and reflection property, and the effective analytical scattering parameters' expressions are achieved. Design curves for this novel bandpass filter are given while six typical numerical examples are presented. The presented simulation results show that the reflection zeros in pass band and transmission zeros in stop band can be tuned by changing the even- and odd-mode characteristic impedances of these coupled lines. Finally, two microstrip bandpass filters with different transmission and reflection zeros are fabricated, measured and compared. The experimental results show excellent bandpass filtering property with sharpened rejection skirts and low insertion loss.