Bandpass Filter Characteristics Research Articles

Second order triple band waveguide band-pass filter with adjustable centre frequency and 3-dB bandwidth

ABSTRACT This paper presents, a novel and simple resonator structure based second order triple band waveguide band-pass filter with adjustable centre frequency and 3-dB bandwidth. The planar insert consists of a circular shape etched part in which three stubs is placed. Three asymmetrical stub length and width are used to control three resonant frequency and 3-dB bandwidth independently. The insert is placed into the transverse plane of the WR-90 waveguide. To achieve second order band-pass filter response two symmetrical resonators is placed at an optimised distance of 8.99 mm. Simulation and optimisation analysis of the proposed filter is carried-out using CST Studio Suite (v23). To validate the 3D model, planar insert and WR-90 waveguide are fabricated individually and inserted manually. The measured results shows triple band bandpass filter characteristics having centre frequencies f 01 = 8.44 GHz, f 02 = 9.98 GHz and f 03 = 11.51 GHz with 3-dB bandwidth of 0.78, 0.12 and 0.3 GHz. The insertion loss of the measured filter is 0.35, 0.8 and 0.55 dB. The in band return loss of the proposed filter are better than 12 dB.

A new technique for improving performance of conventional CRLH resonators using IDC/UISs with enhanced harmonic suppression in balanced dual-band BPFs

Abstract The design of balanced filters based on composite right/left hand (CRLH) structure is well developed. Among those, few designs exist which although they provide some good responses, suffer from narrow stopbands and interdependent passbands. This paper proposes a new technique for improving the characteristics of dual-band balanced bandpass filters (B-BPFs) based on planar CRLH. Using unequal inductive stubs (UISs) attached to the interdigital capacitor (IDC) unit cell, we were able to achieve outstanding harmonic suppression and passband controllability. This structure offers higher degrees of freedom compared to conventional designs and provides better control over the filter specifications. Mathematical modeling, analysis, simulation, fabrication, and performance measurement of the proposed technique in a dual-band B-BPF are also provided. Our work resulted in an independent and controllable dual-band B-BPF with ultra-wide upper differential-mode (DM) stopband of 5.9f 1 and common-mode (CM) suppression of 40.4 and 32.6 dB for the first and second bands, respectively.

Sensitivity characteristics of a wave height sensor based on a MEMS piezoresistive cantilever and waterproof film

Abstract This paper presents the frequency characteristics of a barometric pressure-sensing wave height sensor employing a microelectromechanical system (MEMS) piezoresistive cantilever and a micromesh waterproof film. The proposed sensor exhibited mechanical bandpass filter characteristics owing to air leakage around the cantilever and film. Consequently, high robustness can be achieved if the frequency is designed to match the wave range. We theoretically and experimentally verified that the frequency response is influenced by the film's chamber volume and permeability constant. We demonstrated that the proposed frequency-response model helps design a waterproof wave height sensor using a cantilever-type differential pressure sensor.

Terahertz bandpass filter with Babinet complementary metamaterial mirrors and silicon subwavelength structure.

We fabricated a rigid bandpass filter with a broad far-infrared wavelength range of high transmission using a silicon subwavelength structure with a Babinet complementary metamaterial half-mirror pair, despite its apparent light-blocking structure. The rigid one-piece filter was produced by a simple process involving photolithography, dry etching, and deposition, each performed only once. The transmission principle relies on the Fabry-Perot resonance with a metamaterial half-mirror pair that exhibits extraordinary optical transmission due to spoof surface plasmon polaritons. The transmission center wavelength was successfully predicted by the basic equation of Fabry-Perot resonance with an effective medium approximation. In contrast, a narrower bandwidth and a lower minimum transmittance than those predicted from the basic equation were provided by the subwavelength Si structure between the metamaterial mirrors, resulting in enhanced bandpass filter characteristics.

A direct synthesis method of multi‐port filtering power divider with arbitrary phase shift, power division and reference impedances

AbstractIn this study, a direct synthesis approach is proposed to extract the coupling matrix of multi‐port filtering power divider (FPD) with arbitrary phase shift, power division as well as reference impedances, for the first time. This method provides an attractive technique to synthesise a multi‐functional device that combines the characteristics of bandpass filter, multi‐port power divider and ideal phase shifters as well as the impedance matching network, which can effectively diminish the overall size and improve the performance of the microwave front‐end network. A newly defined coupling matrix corresponding to arbitrary multi‐port topologies that introduces ideal phase shift by virtue of constant frequency‐independent reactance at the source and load is developed in FPD synthesis process. The coupling matrix is obtained directly by optimising the presented cost‐function in this paper, avoiding complex similar transformation process of coupling matrix. Finally, several numerical examples of multi‐port FPD with equal/unequal power division ratio, arbitrary phase shift and reference impedances are synthesised to well verify the proposed synthesis method, and a practical example is given to verify the validity of arbitrary phase shift and arbitrary reference impedance.

A triple‐band frequency selective surface for 5G millimeter‐wave communications

AbstractIn this letter, a new triple‐band millimeter‐wave frequency selective surface (FSS) is presented. The proposed FSS structure consists of three slot‐based resonance mechanisms on the single layer of Rogers Diclad880 dielectric. It shows a high compactness with a unit cell surface area of 5.4 × 5.4 mm2. The proposed FSS exhibits a triple‐band bandpass filter characteristics for the allocated 5G millimeter‐wave frequency regions with sufficient bandwidths corresponding to 23.5–24.6, 27–28.5, and 37.5–41 GHz, respectively. Simulation outcomes reveal that the FSS poses polarization insensitive behavior, and maintains high transmission skill for a wide range of incident angles up to 40°. A 40 × 40 FSS panel is fabricated, and the experimental verification is carried out. The outcomes prove that the proposed FSS is suitable for multiband 5G millimeter‐wave filtering applications.

Light Induced Synthesis of Ag Nanorods for Potential Application as Optical Filter Tailored to Visible Domain

Monodispersed Ag nanorods were synthesized using a one-pot synthesis method. These Ag nanorods normally manifest dual surface plasmon resonance (SPR) peaks. This work presents a study of the variation of SPR peaks with variation in the shape of Ag nanorods. Shape variation was achieved through the degradation of a shape-controlling agent (PVP in this work) under white light irradiance with silica passivation to halt further shape variations. This paper also reports the growth & characterization of thin films of the synthesized rod-shaped silver nanoparticles on glass slides along with studies on band pass filter characteristics of the as-synthesized nanoparticles.

Dissipation and amplification management in an electrical model of microtubules: Hybrid behavior network

The control of dissipation and amplification of solitary waves in an electrical model of a microtubule is demonstrated. This model consists of a shunt nonlinear resistance–capacitance (J(V)–C(V)) circuit and a series resistance–inductance (R–L) circuit. Through linear dispersion analysis, two features of the network are found, that is, low bandpass and bandpass filter characteristics. The effects of the conductance’s parameter λ on the linear dispersion curve are also analyzed. It appears that an increase of λ induces a decrease (an increase) of the width of the bandpass filter for positive (negative) values of λ. By applying the reductive perturbation method, we derive the equation governing the dynamics of the modulated waves in the system. This equation is the well-known nonlinear Schrödinger equation extended by a linear term proportional to a hybrid parameter σ, i.e., a dissipation or amplification coefficient. Based on this parameter, we successfully demonstrate the hybrid behavior (dissipation and amplification) of the system. The exact and approximate solitary wave solutions of the obtained equation are derived, and the effects of the coefficient σ on the characteristic parameters of these waves are investigated. Using the analytical solutions found, we show numerically that the waves that are propagated throughout the system can be dissipated, amplified, or remain stable depending on the network parameters. These results are not only in agreement with the analytical predictions, but also with the existing experimental results in the literature.

Non-reflective Odd Harmonic Band Pass Filter

This article presents a non-reflective strip filter (NPF) with two passbands corresponding to the first and third harmonics of the received or transmitted signal. The NPF consists of connected strip lines (LPL) and RLC circuits included into the diagonal ports of the SPL. The solution of the inverse problem of obtaining the frequency dependence of the RLC circuits is presented. The obtained ratios provide the synthesis of the frequency characteristics of the RLC circuit and, ultimately, the characteristics of a non-reflective bandpass filter. Experimental results of the study of the single- stage NPF of odd harmonics with frequencies of 0.96 GHz and 2.9 GHz with return losses of at least –10 dB in the frequency range up to 4.8 GHz are presented.

Development of Broken Rotor Bar Fault Diagnosis Method with Sum of Weighted Fourier Series Coefficients Square

This study proposes a broken rotor bar (BRB) fault diagnosis method for an induction motor using the sum of the weighted Fourier series coefficients squares of a complex current as a diagnosis signal. First, the sum of the squares of the Fourier series coefficients confirms the very narrow band-pass filter characteristics to derive a specific frequency component. This assists us in obtaining a BRB fault diagnosis signal that exists in a limited frequency range. Second, the magnitude of the Fourier series coefficients of the BRB fault signal is proportional to the slip frequency and load condition. A weighting factor is proposed to render the BRB fault signal irrelevant to the slip frequency and load condition. Consequently, the proposed fault diagnosis can be conducted without the slip frequency information or searching for the maximum coefficient component. Finally, the proposed fault diagnosis method is validated through experiments using a 55 kW induction motor with and without a BRB fault. It is implemented with a DSP controller at time intervals of 20, 10, 5, and 4 s for the Fourier series. The proposed diagnosis method performs well under various load conditions and shows that the derived fault signal exhibits a large difference between healthy and BRB faulty induction motors.

Wideband Highly-Selective Bandpass Filtering Branch-Line Coupler

This paper presents a novel design of a wideband highly-selective bandpass filtering branch-line coupler (FBLC). By integrating a coupled microstrip line, and an open-ended stub at each port of a single-section BLC, bandpass filtering characteristics with excellent selectivity and broad operating bandwidth have been achieved. The proposed circuit has been verified through EM simulations and physical measurements of the fabricated prototype. Experimental results demonstrate over 71-percent fractional bandwidth (2.25 GHz to 4.74 GHz) with a power imbalance lower than 0.5 dB. At the same time, the measured return loss and isolation are better than 15dB with the phase imbalance of 5 ± 5°. This level of performance, especially in terms of bandwidth and selectivity, has not been reported in the literature thus far.

Experimental Study of the Characteristics of Band-Passed Ultra-High Frequency Filters with Increased Protective Band in the Interest of Ensuring Electromagnetic Compatibility

The article presents the structure of the method for the synthesis of microwave bandpass filters (BPF) on non-uniform lines, which makes it possible to select the structure and parameters of the BPF that provide the maximum length of the stop band to meet the requirements of electromagnetic compatibility (EMC) with given restrictions on the attenuation characteristics in the passband and barrier bands. and the established design and technological limitations on the drop in wave resistance and manufacturing tolerances. The results of experimental studies of the characteristics of ultrahigh-frequency bandpass filters with an increased protective band in order to ensure EMC are presented

Photonic crystal bandpass filter exploiting the degenerate modes tunable with MEMS actuator for terahertz application

AbstractIn this study, the bandpass filter characteristics in standing wave resonator formed in a two‐dimensional (2D) photonic crystal (PC) is integrated with microelectromechanical systems (MEMS) actuator to tune degenerate mode split. A single and sequentially connected indirect coupling structure consisting of waveguide as well as cavity is placed to the 2D PC. It has been shown that the modes of the bands can be split by structural deformation of the PC via MEMS actuator. The modes frequencies can be changed with the bias voltage applied to MEMS structure, which allows to tune about 1 THz (λ = 35 nm). The designed PC and MEMS structures are analyzed with simulation programs using finite difference time domain method and finite element method, respectively. The proposed PC structures can be effectively used in new generation all optical THz communication applications.

An Improved Research on Frequency-Fixed Cascaded SOGI Single-Phase PLL

The second-order generalized integrator (SOGI) with band-pass filtering characteristics is widely used in the design of advanced single-phase phase-locked loops (PLLs). But this type of PLL has insufficient ability to restrain dc biases, which limits their applications under certain conditions. Recently, a PLL adopting two cascade SOGI structures is called the cascaded generalized integrator PLL (CGI-PLL), which has perfect dc offsets blocking capability. However, the two output signals of the quadrature signal generator (QSG) formed by frequency-fixed CGI have different amplitudes, which makes the second harmonic oscillations appear in the estimated parameters of the PLL while the frequency deviates from the nominal frequency. Similarly, the in-phase output signal of CGI-based QSG is not synchronized with the fundamental frequency component of the grid voltage under frequency drifts, which is the reason for the phase offset error in the PLL outputs in the steady state. Some compensation strategies are added to correct the error that exists in the frequency-fixed CGI-PLL when the frequency deviates from the nominal value.

Design of Concurrent Dual-Band Band Pass Filter using Hybrid Metal insulator Metal for Nanoscale Applications

In this paper, investigation on Hybrid Metal Insulator Metal (HMIM) plasmonic waveguide (PWG) filters for dual-band applications. The filters are designed using circular ring resonator (CRR) and CRR with single as well as dual slits. The filters are connected using coupled line feed. The dual-band Band Pass Filter (BPF) characteristics can be realized by varying radius (r) and gap (g) between the feed and ring resonator. The proposed CRRs are operated at THz frequencies. The filters are designed and simulated using commercially available CST studio suite software under Perfect Matched Layer (PML) boundary conditions by keeping 5 nm x 5 nm mesh size. The transmission and reflection characteristics of the filters are explained by the resonance conditions, which agrees with theoretical calculations. The proposed work is best suitable for the plasmonic integrated optical circuits for nanoscale applications.

Real-Time Abnormal-Signal Detection Under a Noisy Environment Using a Resonance Filter

In this article, we present improved short-time Fourier transform for fault detection of field coils, among the most important parts in rotating machinery. It is generally difficult to detect a fault signal of a field coil due to the low signal-to-noise ratio (SNR) associated with these signals. To solve this problem, we constructed a parallel resonance circuit using the inductance of the field coil and improved the SNR of the fault detection signal by using the bandpass filter characteristics of the resonance circuit. The transfer function curve upon parameter changes of the proposed resonance circuit is presented, and the governing equation is derived so that the resonance frequency can be calculated. We also carried out a fault detection test to verify the feasibility of the proposed method. As a result, we demonstrated that the proposed method can enhance the SNR and enable fault detection using the extracted abnormal signal. Also, it was confirmed that the proposed system responds instantaneously to an abnormal signal for fault detection. Therefore, it is proved that the methodology presented in this article is efficient for fault detection in rotating machinery.

Wiener–Hopf approach for the coaxial waveguide with an impedance-coated groove on the inner wall

In the present work, the band-pass filter characteristics of a coaxial waveguide with an impedance coated groove on the inner wall and perfectly conducting outer wall is analyzed rigorously through the Wiener–Hopf technique. By using the direct Fourier transform, the related boundary value problem is reduced to the Wiener–Hopf equation whose solution contains infinitely many constants satisfying an infinite system of linear algebraic equations. These equations are solved numerically and the field terms, which depends on the solution obtained numerically, are derived explicitly. The problem is also analyzed by applying a mode-matching technique and the results are compared numerically. Besides, some computational results illustrating the effects of parameters such as depth of the groove, surface impedances and radii of the walls are also presented.

Basic Characteristics of a-Si:H by dc Sputtering and Application to Bandpass Filter for Shortwave Near Infrared, and Durability Evaluation

In this study, short-wave near-infrared (SWNIR) band pass filters (BPF) using hydrogenated amorphous silicon (a-Si:H) were fabricated by reactive sputtering method at 200℃, and their optical performance and thermal durability were evaluated. The sample of the lowest extinction coefficient (k＜1×10－3) and the highest durability was obtained at H2 partial pressure ratio of 30% for a-Si:H. The transmittance of the BPF with stacked a-Si:H (H2＝30%) and SiO2 was more than 90%. Its optical characteristics were consistent well with the simulation. It was found that the characteristics of BPF correlated with the optical properties of a-Si:H stemmed from structural relaxation and hydrogen composition. It was also suggested that the stable performance of the BPF could be expected below 250℃.

Real-Time Resting-State Functional Magnetic Resonance Imaging Using Averaged Sliding Windows with Partial Correlations and Regression of Confounding Signals.

Background/Introduction: There is considerable interest in using real-time functional magnetic resonance imaging (fMRI) for monitoring functional connectivity dynamics. To date, the majority of real-time resting-state fMRI studies have examined a limited number of brain regions. This is, in part, due to the computational demands of traditional seed- and independent component analysis-based methods, in particular when using increasingly available high-speed fMRI methods. Methods: This study describes a computationally efficient, real-time, seed-based, resting-state fMRI analysis pipeline using moving averaged sliding-windows (ASW) with partial correlations and regression of motion parameters and signals from white matter and cerebrospinal fluid. Results: Analytical and numerical analyses of ASW correlation and sliding-window regression as a function of window width show selectable bandpass filter characteristics and effective suppression of artifactual correlations resulting from signal drifts and transients. The analysis pipeline is compatible with multislab echo-volumar imaging and simultaneous multislice echo-planar imaging with repetition times as short as 136 msec. High-speed, resting-state fMRI data in healthy controls demonstrate the effectiveness of this approach for minimizing artifactual correlations in white and gray matter, which was comparable to conventional regression across the entire scan. Integrating sliding-window averaging (width: W1) within a second-level sliding-window (width: W2) enabled monitoring of intra- and internetwork correlation dynamics of up to 12 resting-state networks with bandpass filter characteristics determined by the first-level sliding-window and temporal resolution W1 + W2. Conclusions: The computational performance and confound tolerance make this seed-based, resting-state fMRI approach suitable for real-time monitoring of data quality and resting-state connectivity dynamics in neuroscience and clinical research studies. Impact statement Using averaged sliding-windows for seed-based correlation and regression of confounding signals provides a powerful model-free approach to increase tolerance to artifactual signal transients in resting-state analysis. The algorithmic efficiency of this sliding-window approach enables real-time, seed-based, resting-state functional magnetic resonance imaging (fMRI) of multiple networks with computation of connectivity matrices and online monitoring of data quality. Integration of a second-level sliding-window enables mapping of resting-state connectivity dynamics. Sensitivity and tolerance to confounding signals compare favorably with conventional correlation and confound regression across the entire scan. This methodological advance has the potential to enhance the clinical utility of resting-state fMRI and facilitate neuroscience applications.

Microwave Signal Detection Based on the Nonpolarimetric Frequency Down-Conversion Technique

We report a method for electro-optic (EO) microwave detection based on a nonpolarimetric frequency down-conversion technique. The detection principle is based on the coherent detection of the modulation sideband generated based on the interaction between the optical frequency comb and the microwave signal in the EO crystal. We theoretically analyzed the frequency characteristics of this technique. The theoretical calculation showed that the negative interference of the beat signals between the comb component and the modulation sidebands generated from the higher order comb components decreases the EO detection sensitivity, suggesting that the steeper roll-off characteristics of the optical bandpass filter will increase the sensitivity at the lower frequency side. We further demonstrate that the calculated frequency characteristic agrees well with the experimental measurements from 1 MHz to 10 GHz. Finally, we demonstrate the electric field visualization between the signal line and ground plane of the microstrip line. The proposed method is applicable to antenna measurements and measurements for electromagnetic compatibility.