Varicap-tuned narrowband filters with extended rejection band based on U-shaped microstrip Resonators

A resonance equation for the first unwanted resonant frequency of tunable microwave U-shaped loop-type resonator with variable capacitance has been derived. This frequency does not depend on the variable capacitance value; it is invariable and proportional to λ-type oscillations. The ascertained feature makes it possible to determine the ratio of the first unwanted resonant frequency to the frequency of the main resonance and control the rejection bandwidth of tunable filters with U-shaped resonators. A narrowband (2%) varicap-tuned filter with extended rejection band has been built and its experimental data are presented. The experimental four-resonator filter could be tuned in the frequency range 225–400 MHz. The filter rejection band in terms of the attenuation level of –40 dB was located in the frequency range 420–1290 MHz, i.e., f _max /f _min = 3.07. Varicap-tuned filters with microstrip U-shaped resonators are shown to have a good potential for their practical use.     

Analysis of a novel (LCR)trap-LC-RC filter with improved performance for standalone inverters

ABSTRACT

This work introduces a new passive filter structure for a pulse width modulated inverter used in standalone applications. The proposed structure consists of an additional capacitor connected across the resistance-capacitance branch of the traditional LCR filter and an additional resistor connected across the trap filter capacitor in the traditional (LC)_trap-LCR filter configuration which helps to reduce damping power loss and increase harmonic attenuation while maintaining the same overall filter size of conventional filters. A comprehensive parameter design procedure of the proposed filter is introduced which considers inverter switching frequency and choice of damping components. Further, particle swarm optimisation algorithm is newly employed in this work to minimise resonant peaking on the premise of allowable values of overall filter inductance, capacitance and resistance. Simulation and experimental results are presented to analyse the performance of the proposed filter and a comparison is established with other passive filter topologies. A five-level inverter with the proposed filter is implemented using a SPARTAN- 6 XC6SLX25 processor on an experimental set-up. The experimental results show an attractive performance of the proposed filter in providing improved inverter output waveforms, significant harmonic reduction in the high-frequency band, reduced resonant peaking, lesser harmonic distortion and lower damping power loss.     

Multi‐harmonic Suppression Band‐Pass Filter for Communication System

For the purpose of decreasing intermodulation distortion, a new multi‐harmonic suppression band‐pass filter based on a microstrip radial stub is studied. Compared with traditional resonator filters, the new filter can suppress the second, third, and even fourth harmonics directly. The dimension of the filter is about 0.3 λ_g0 × 0.13 λ_g0 (λ_g0 is the guiding wavelength at the resonant frequency). Only one gap was introduced, so lower insertion loss can be obtained. Basic agreement between the measured and simulated results has been achieved.     

Interaction of electrical active intrinsic defects in Sn-doping Bi2Te3

Impure Sn produces the resonant states on the background of the allowed spectrum of states of the valence band in Bi₂Te₃. A high density of the resonant states stabilizes the Fermi level _F. Stabilization of _F leads to an enhancement of the volume homogeneity of the distribution of electrically active components.We report the results of an experimental study on the influence of doping Sn atoms on hole concentrations of Bi₂Te₃ and replace the part of Te atoms on Se atoms and the part of Bi atoms on Sb atoms. The estimation of the influence of resonant states on the process of crystal defects formation has been attempted theoretically.     

Cascaded resonant-grating filters: experimental results on lowered sidebands and narrowed lines

Cascaded resonant grating filters are experimentally characterized. The levels to which cascaded resonant filters yield lowered sidebands and narrowed linewidths, as compared with individual filters, are measured. For example, four cascaded filters provide experimental sideband levels at -47 dB over a 50-nm wavelength range, a spectral linewidth of 0.43 nm, with an insertion loss of 3.7 dB.     

Substrate integrated waveguide (SIW) asymmetric dual-mode filter and diplexer

Substrate integrated waveguide (SIW) can be used to implement high Q waveguide components with the same easy and low-cost fabrication process as planar circuits. In this paper two inline three-pole dual-mode filters with asymmetric transmission response based on SIW are presented. These two filters, consisting of a TE₁₀₂-TE₃₀₁ dual-mode SIW cavity and a TE₁₀₁ mode SIW cavity, are centred at around 10?GHz with a transmission zero on the left of the passband and the right of the passband, respectively. Based on the two kinds of three-pole deal-mode filters, a diplexer with isolation better than 35?dB is developed. A linear microstrip taper is used to implement the transition between microstrip and SIW. The measured results agree with simulated results.     

Surface-acoustic-wave resonator filters

This paper presents an overview of surface-acoustic-wave (SAW) resonator filter technology. Given the current state of the art, these filters promise reproducible low-loss (≲6 dB) narrow-bandwidth (500 ≲ f/Δf ≲ 50 000) responses in the VHF and UHF ranges. Devices that contain one or a number of sections, each consisting of a resonant cavity between two grating reflectors and an input and output coupling mechanism, are considered. The initial discussion describes the layout, theoretical characteristics, and typical experimental responses of singlesection two-port filters. The subsequent discussion focuses on multisection devices using any of various intercavity coupling techniques. A generalized analysis and design formalism based on wave-scattering theory is reviewed, and experimental results from a number of device prototypes are given. Finally, practical design and fabrication trade-offs and performance ranges are summarized for a number of configurations.     

Track-Following Control Using Resonant Filter in Hard Disk Drives

A design method to suppress the disturbances by using a resonant filter for track-following control has been developed. The resonant filter can realize a stable resonant mode by a filter to obtain a circular vector locus that recedes from the critical point on the Nyquist diagram. With this method, the control engineers can easily design and implement a controller to suppress the disturbances in head-positioning systems at a specific frequency by adding digital filters. Our experimental results show that the proposed method can greatly suppress the nonrepeatable runout and repeatable runout above the servo bandwidth.     

基于固定频率激光器的低成本闭环谐振陀螺系统仿真

提出了一种使用固定频率窄线宽激光器作为干涉光源的闭环谐振式光纤陀螺系统.该系统利用相位调制器对干涉光进行移频控制,完成对谐振腔逆时针方向谐振频率的跟踪和锁定.建立了陀螺系统Simulink模型并仿真研究了不同速率点下的陀螺输出特性,结果表明,±200(°)/s速率范围内逆时针谐振频率锁定时间小于15 ms,陀螺标度因数非线性为2.41×10-4.与采用传统频率可调谐窄线宽激光器的闭环谐振式光纤陀螺系统相比,两者锁频时间和标度因数非线性基本一致.该研究为低成本闭环谐振式光纤陀螺系统的实现提供了理论和数据支撑.     

Propagation in a Rectangular Waveguide Periodically Loaded with Resonant Irises

In this contribution we treat the problem of an infinite rectangular waveguide periodically loaded by means of infinitely thin resonant irises. The method of solution breaks down the problem into two separate steps: 1) the multiport network characterizstion of the resonant iris; 2) the network analysis of the equivalent periodic network. The results for the resonant iris can be used for various applications, such as the design of waveguide filters and matching networks. In the limiting cases of purely capacitive or inductive irises, the results agree exactly with existing experimental and numerical values. The size of the eigenvalue equation to be solved for the periodic structure equals half the number of ports of the network chracterization of the iris and is generally small (typically five to seven). The eigenvalues have good convergence properties with resect to the size of the matrix.     

Thin stripline bandpass filters for the centimeter band

This article considers the design of thin stripline (1 mm) bandpass filters in the centimeter band, which contain dielectrics with different relative permittivity ε _r . This includes the choice of the resonators, the dielectric material, the preliminary assessment of resonators’ unloaded quality factors and taking into account the features of the frequency response curve of the filter. It was found, that the passband width of the thin comb filters with λ/4 resonators and array-type filters with λ/2 resonators cannot exceed 6% for any values of ε _r and the length of resonators of at least 2 mm. The array-type filters with resonators of half-wave type and with alternating signs of the coupling factors between resonators were proposed. Under certain additional conditions, the attenuation poles appear in such filters, resulting in improved selectivity. The results of computer modelling of the frequency response curve of thin filters of cm band are presented. They are compared to the frequency response of other filters. The data obtained from computer modelling showed good correspondence with the experimental data.     

Research on orotron oscillator with dispersive open resonant system

Theoretical and experimental results of an investigation into a new resonant system have been obtained. This system is named the sphere-corner-echelette open resonator (SCEOR) due to the employment of a mirror that was formed by two echelettes at the angles of 45° to the resonator axis. It turns ont that this resonator is excited on the specific modes not unique to others oscillating systems. There are presented the results of the experimental research of the orotron oscillator with the SCEOR. The spectrum of this device contains only the fundamental modes such as theT E M ₀₀₆,T E M ₀₀₇,T E M ₀₀₈. The efficiency of the orotron is improved, when all other factors are the same the orotron with a much used sphere-cylindrical open resonator.     

Stripline combline filters on substrates designed on high-permittivity ceramic materials

Stripline bandpass combline filters designed on high-permittivity ceramic materials are analyzed. In order to form coupling between codirectional quarter-wave resonators, they are connected in the regions of their short-circuited ends by a stripline conductor. Features of the characteristics of such filters are revealed and compared with the parameters of other ceramic microwave filters. Experimental characteristics of a stripline filter designed on a ceramics with permittivity ?_r = 38 are presented. The experimental results are in good agreement with results of computer simulation.     

Design of microstrip quadruplet filters with source-load coupling

Quadruplet microstrip filters with source-load coupling are proposed to achieve similar skirt selectivity and/or in-band flat group delay as that of a sixth-order canonical form or an extracted pole microstrip filter. The diagnosis method of unwanted effects such as asynchronous resonant frequencies and unwanted couplings, which often occurs in the microstrip's open environment, is described in detail. A systematic design flow to implement a quadruplet microstrip source-load coupled filter with proper filter response is also provided. Two trial filters exhibited quasi-elliptical and flat group-delay response are designed and fabricated. Both theoretical and experimental results are presented.     

Generalized multilayer anisotropic dielectric resonators

Modeling of the generalized multilayer cylindrical anisotropic dielectric loaded resonator by a rigorous mode-matching method is presented in this paper. Eigenmodes of the multilayer two parallel-plate waveguides are obtained. By cascading the radial discontinuities of the structure, resonant frequency, field distribution, unloaded Q, and the frequency sensitivity of the resonator are obtained. The method can be used to analyze and design resonators and filters of multilayer structure. The computed results are compared with measured results and with experimental data, and shown to be in good agreement     

基于齿状缺陷地的宽阻带交叉耦合SIW滤波器

提出了一种齿状缺陷地低通传输线结构,该低通传输线由多级齿状缺陷地构成,通过调节齿状缺陷地枝节长度,可以有效调节低通和阻带频率范围。利用该齿状缺陷地结构,级联交叉耦合扇形基片集成波导(SIW)滤波器,该文设计了一款高带外抑制的宽阻带滤波器,与传统SIW带通滤波器相比,其矩形系数K_{40 dB}=2,阻带范围大于2倍的中心频率,具有较好的通带和阻带选择特性。测试结果表明,滤波器的中心频率为10.35 GHz,3 dB和40 dB带宽分别为507 MHz和1.05 GHz,插入损耗优于1.47 dB,与仿真结果基本一致。     

Thin bandpass filters containing sections of symmetric strip transmission line

Thin (1-mm thick or thinner) combline bandpass filters based on sections of symmetric strip transmission lines and containing closely spaced (0.1–0.2 mm apart) stepped-impedance resonators are described. It has been found that, if these filters are made on high-permittivity ceramic substrates, their dimensions prove to be smaller than the dimensions of other ceramic-based filters. Various frequency characteristics of these filters—symmetric, with increased one-sided selectivity, and with a constant delay time—have been analyzed. The experimental results obtained for a 1-mm-thick bandpass filter with ? _r = 9.7 are in good agreement with the computer-simulation data.     

Microstrip U-shaped resonators

Influence analysis of U-shaped microstrip resonators?? parameters and parameters of dielectric substrate on resonant frequencies and unloaded quality-factor of resonators is conducted. Three kinds of U-shaped resonators are considered which differ in operation modes at the resonator??s ends: short-circuit or no-load. It is revealed that in cases of small spacing between the arms of U-shaped resonators distribution of their resonant frequencies significantly differs from the corresponding quarter-wavelength or half-wavelength resonators and leads to decreased stop-band in pass-band filters based on them. Experimental research shows that decreasing the spacing between the arms of U-shaped resonators leads to decrease in quality-factor by 20?C30%. Experimental samples were manufactured on substrates with ? _r = 92 and ? _r = 38.     

Synthesis of the lead,arsenic, and bismuth chalcogenides with liquid encapsulation

The possibility of synthesis of the lead, arsenic, and bismuth chalcogenides with liquid encapsulation has been investigated. The conditions and results of the synthesis of PbSe, PbS, PbTe, Bi2Te3, and As₂Te₃, as well as solid solutions in the systems PbSe-CdSe and Bi₂Te₃-Bi₂Se₃ are reported. The obtained materials have been used for fabrication of thin-film photodetectors and interference filters for infrared radiation. Recommendations concerning the choice of fluxes for liquid encapsulation and the temperature conditions of synthesis are given.     

Optical properties of F.I.R. metallic grids: Reflection phase shift measurements

Utilization of metallic grids stacks for F.I.R filters needs a good knowledge of optical properties of each grid. We study here an experimental method in order to determine the wave's change of phase by reflection on a wire grid. We use a Perot-Fabry interferometer constituted by these grids.