Left handed coplanar waveguide band pass filters based on bi-layer split ring resonators

A new type of compact band pass filters based on planar structures with three metal levels is proposed. The central layer consists on a coplanar waveguide (CPW) with periodic wire connections between the central strip and ground planes. In the upper and lower metal levels, split ring resonators (SRRs) are etched and aligned with the slots. The wires make the structure to behave as a microwave plasma, with a negative effective permittivity covering a wide frequency range. SRRs, which are magnetically coupled to the CPW, provide a negative magnetic permeability in a narrow frequency range above their resonant frequency. The result is a band pass structure which supports wave propagation in a frequency interval where negative permittivity and permeability coexist. The bandwidth of the structure can be controlled by tuning the resonant frequency of the upper and lower SRRs and the distance between SRRs. Fabricated prototype devices exhibit very low insertion losses in the pass band (<1.5 dB) and high frequency selectivity.     

Q-factor of tuned microstrip resonator

The paper presents research of quality factor in the micro-mechanically tunable microstrip resonator and its change in response to tuning. In the presented design unloaded quality factor increases about 10% during tuning due to reduction of dielectric loss in substrate’s medium and ohmic loss in metal electrodes. When total loss in the device is relatively small, loss mechanisms contribute additively, so complex effective permittivity can be used to account loss reduction and frequency tuning.     

Stripe delay filters

There are considered constructions of microsized stripe delay filters, which are realized on a basis of ceramic materials with high dielectric permittivity. Delay time of non-minimal phase filters is 7–12 ns at frequencies of 1900 MHz with relative bandwidth of 3.6–3.85%. Filters dimensions are comparable with ones used in portable communication devices. Dimensions of researched three-resonator filter at frequency of 1900 MHz are 8.4×5×2mmwith material dielectric permittivity ε_r = 92, and 5-resonator filter ones are 9.2×8.6×2 mm. Filters are different from traditional delay filters. Two filters of considered ones contain odd resonator number and the third one contains four resonators and it has two cross couplings. The basis of the filters is amount of step-impedance stripe resonators pairs located close to each others whose electromagnetic coupling behavior is capacitive. There are represented the results of frequency characteristics simulation for different delay filters.     

Design of High-Performance Millimeter Wave and Sub-Millimeter Wave Quasi-Optical Isolators and Circulators

Faraday rotators using permanently magnetized ferrite materials are used to make quasi-optical isolators and circulators at millimeter wave and sub-millimeter wave frequencies that have far higher performance than their waveguide equivalents. This paper demonstrates state-of-the-art performance for four-port quasi-optical circulators with 60-dB isolation, 0.2-dB insertion loss, and better than 80-dB return loss for devices centered at 94 GHz. A method is presented for the accurate characterization of the complex permeability and permittivity of permanently magnetized ferrites via a series of frequency and polarization dependent transmission and reflection measurements. The dielectric and magnetic parameters for the sample are determined by fitting theoretical curves to the measured data. These fitted parameters are then used in a model for a complete quasi-optical Faraday rotator, including matching layers, allowing the accurate design and fabrication of these devices for any specific operational frequency band in the millimeter wave and sub-millimeter wave regime. Examples are given showing typical results and demonstrating how temperature cycling can significantly improve the temperature stability of these devices, while allowing fine tuning of the center frequency. We also indicate the performance possible at higher frequencies to above 1 THz and outline performance of truly planar isolators where lossy polarizer material is built into the Faraday rotator matching structure     

Inorganic–Organic Hybrid Dielectrics for Energy Conversion: Mechanism,Strategy, and Applications

Dielectric materials with higher energy storage and electromagnetic (EM) energy conversion are in high demand to advance electronic devices, military stealth, and mitigate EM wave pollution. Existing dielectric materials for high-energy-storage electronics and dielectric loss electromagnetic wave absorbers are studied toward realizing these goals, each aligned with the current global grand challenges. Libraries of dielectric materials with desirable permittivity, dielectric loss, and/or dielectric breakdown strength potentially meeting the device requirements are reviewed here. Regardless, aimed at translating these into energy storage devices, the oft-encountered shortcomings can be caused by either of two confluences: a) low permittivity, high dielectric loss, and low breakdown strength; b) low permittivity, low dielectric loss, and process complexity. Contextualizing these aspects and the overarching objectives of enabling high-efficiency energy storage and EM energy conversion, recent advances in by-design inorganic–organic hybrid materials are reviewed here, with a focus on design approaches, preparation methods, and characterization techniques. In light of their strengths and weaknesses, potential strategies to foster their commercial adoption are critically interrogated.     

一种壁厚渐变蜂窝宽带透波结构*

采用介电常数渐变结构是一种有效实现宽带透波的方法。为实现介电常数随厚度变化,本文提出了 一种壁厚渐变六边形蜂窝结构。根据蜂窝等效介电常数的近似计算公式和介质介电常数变化分布,计算出该渐变 结构的几何参数。基于渐变线宽带匹配理论,对空气和高介电常数介质进行宽带匹配设计,从而得到介质介电常数 随厚度渐变的分布规律。为验证该设计方法的有效性,采用CST 商用仿真软件,对该结构的周期单元透波性能进行 仿真。仿真结果表明该结构在垂直入射和大入射角情况下,具有良好的宽带透波特性。通过改变芯层材料厚度可 以进一步调整宽带透波特性的起始频率。     

A Comprehensive Technique to Determine the Broadband Physically Consistent Material Characteristics of Microstrip Lines

This paper describes a method to extract the relative complex dielectric permittivity from propagation coefficient measurements on microstrip lines. The material characteristics of microstrip lines fabricated on two different types of substrates commonly used in microwave circuit and printed circuit boards are investigated. The mechanisms that cause the effective permittivity of microstrip lines to be dispersive are explored. The technique includes creating closed-form effective permittivity equations to relate the effective permittivity of the microstrip lines to the real part of the dielectric permittivity of the substrate. Curve-fitting methods are used to create causal dielectric material models that relate the imaginary part of the dielectric permittivity to its real part. The methods developed in this paper can be used to characterize low-loss dielectric materials whose polarization is dominantly dipolar within the microwave frequency range in high-speed packaging applications.      

Frequency-dependent solution of suspended microstrip line with tuning septums

The frequency-dependent effective dielectric permittivity and equivalent characteristic impedances of the technically most relevant modes of the suspended microstrip line with tuning septums are derived using the conventional spectral domain approach. Normalised numerical results are presented in a very large frequency band.     

Lattice vibration, optical, and mechanical properties of aluminum phosphide (AlP) compound under the influence of temperature

<正>We have studied the lattice vibrations, optical and mechanical characteristics of the zinc-blende aluminum phosphide(Al P) compound. Investigations have been done into the effect of temperature on refractive index, optical dielectric constant, static dielectric constant, longitudinal and transversal sound velocities, reflectivity, susceptibility, phonon frequencies, micro-hardness, ionicity, and transverse effective charge. Al P is a wide-indirect band gap semiconductor and has a wide r...     

Microwave-signal generation in a planar Gunn diode with radiation exposure taken into account

Microwave-signal generation in planar Gunn diodes with a two-dimensional electron gas, in which we previously studied steady-state electron transport, is theoretically studied. The applicability of a control electrode similar to a field-effect transistor gate to control the parameters of the output diode microwave signal is considered. The results of physical-topological modeling of semiconductor structures with different diode active-region structures, i.e., without a quantum well, with one and two quantum wells separated by a potential barrier, are compared. The calculated results are compared with our previous experimental data on recording Gunn generation in a Schottky-gate field-effect transistor. It is theoretically and experimentally shown that the power of the signal generated by the planar Gunn diode with a quantum well and a control electrode is sufficient to implement monolithic integrated circuits of different functionalities. It is theoretically and experimentally shown that the use of a control electrode on account of the introduction of corrective feedback allows a significant increase in the radiation resistance of a microwave generator with Schottky-gate field-effect transistors.     

Methods of accounting for inclusion-shape randomness in calculating the effective dielectric characteristics of heterogeneous textured materials

Two methods of accounting for the inclusion-shape randomness, an analytical method and a method for simulating a medium with several inclusion types, are considered for calculating the effective permittivity tensor of a textured heterogeneous matrix-type medium with inclusions of a random ellipsoidal shape. The methods are based on the generalized Maxwell–Garnett model. The rotation group representations are used to consider the distribution of inclusion orientations. The results of calculations by these methods of the effective dielectric characteristics of porous silicon models in an alternating electromagnetic field in the frequency range of 10₃–10₈ Hz are compared.     

Dielectric properties of single crystals of Al2O3, LaAlO3, NdGaO3, SrTiO3, and MgOat cryogenic temperatures

A dielectric resonator technique has been used for measurements of the permittivity and dielectric loss tangent of single-crystal dielectric substrates in the temperature range 20-300 K at microwave frequencies. Application of superconducting films made it possible to determine dielectric loss tangents of about 5×10^-7 at 20 K. Two permittivity tensor components for uniaxially anisotropic samples were measured. Generally, single-crystal samples made of the same material by different manufacturers or by different processes save significantly different losses, although they have essentially the same permittivities. The permittivity of one crystalline ferroelectric substrate, SrTiO₃, strongly depends on temperature. This temperature dependence can affect the performance of ferroelectric thin-film microwave devices, such as electronically tunable phase shifters, mixers, delay lines and filters     

Millimeter wave twist reflector design aspects

A millimeter-wave twist reflector design procedure is described. An effective dielectric constant for capacitive susceptance correction for a unidirectional planar grating at the interface of free space and dielectric material in the twist reflector environment is introduced. The loss factor of the dielectric material is taken into account for the prediction of twist reflector performance. With the introduction of these corrections experimental results are found to be in close agreement with the theory. Normalized curves for the design of twist reflectors in terms of grating parameters, dielectric substrate relative permittivity, and dielectric material thickness are presented. Experimental results are given     

Frequency dispersion investigation of output reactance and capacitance in GaAs MESFETs by means of dielectric loss tangent consideration

The aim of this article is to investigate the effect of dielectric loss tangent on frequency dispersion of output reactance and capacitance in GaAs MESFETs. For this purpose, measurements of output impedance modulus and phase have been carried out within a frequency range of 10 Hz to 10 kHz, and various voltage values of gate-source (V_gs=0, -0.2, -0.3, -0.35, -0.4, -0.45, -0.5 and -0.6 V) and drain-source (V_ds=0.7, 0.9, 1, 1.5 and 2 V) Based on the concept of complex permittivity of semiconductor material, complex capacitance is used to analyze and simulate frequency dispersion of output reactance and capacitance of GaAs MESFETs. The results show that conductor losses which dominate the dielectric loss tangent are attributed to trapping mechanisms at the interface of devices; so they influence the frequency dispersion of output reactance and capacitance in particular at low frequencies. This reveals that frequency dispersion of these parameters is also related to dielectric loss tangent of semiconductor materials which affects the response of electronic devices according to frequency variation.     

A carrier-mobility model for high-k gate-dielectric Ge MOSFETs with metal gate electrode

A mobility model for high-k gate-dielectric Ge pMOSFET with metal gate electrode is proposed by considering the scattering of channel carriers by surface-optical phonons in the high-k gate dielectric. The effects of structural and physical parameters (e.g. gate dielectric thickness, electron density, effective electron mass and permittivity of gate electrode) on the carrier mobility are investigated. The carrier mobility of Ge pMOSFET with metal gate electrode is compared to that with poly-Si gate electrode. It is theoretically shown that the carrier mobility can be largely enhanced when poly-Si gate electrode is replaced by metal gate electrode. This is because metal gate electrode plays a significant role in screening the coupling between the optical phonons in the high-k gate dielectric and the charge carriers in the conduction channel.     

Lagrangian formulation of a linear microstrip resonator: theory andexperiment

A Lagrangian approach is used to formulate the electromagnetic scattering properties of a linear microstrip resonator. The resonator design includes a center microstrip separated from the source and output loads by dielectric gaps. The gaps of the resonator are represented by capacitively coupled π-networks whereas the Lagrangian is formulated in the discrete limit such that the equations of motion transform into two boundary conditions, relating the waves on the two sides of the gap in terms of two lumped capacitors. The effective capacitors expressed in the boundary conditions are actually the capacitances experienced by the even and odd excitation modes of the system, respectively. The calculations, therefore take into account the characteristic impedance, effective dielectric constant, conductivity of the metal strip and the ground plane, and dielectric loss tangent of the dielectric material. In addition, the two capacitor values representing the gaps are included in a consistent manner with the above parameters by the application of the Lagrangian formulation. Calculated and measured reflection coefficients of linear microstrip resonators are compared, and general agreement is found between theory and experiments     

Polarization-independent thermooptic phase shifters in silicon-oxynitride waveguides

The effective refractive index of dielectric waveguides can be tuned using the thermooptic effect. In general, the tuning efficiency is polarization-dependent owing to temperature-induced stress in the layers, which causes polarization-dependent loss in optical devices. These stress issues are analyzed and tested for a high-index-contrast waveguide structure based on a silicon-oxynitride core. Experimental results are in agreement with simulations. The relative difference in tuning efficiency for transverse electric and transverse magnetic polarized light can be tuned from -3% to +3% by appropriate waveguide technology control. The optimized thermooptic phase shifters show tuning efficiency differences below 0.25%, which are reproducible from wafer to wafer.     

Practical aspects of complex permittivity reconstruction with neural-network-controlled FDTD modeling of a two-port fixture.

The paper discusses characteristics of a new modeling-based technique for determining dielectric properties of materials. Complex permittivity is found with an optimization algorithm designed to match complex S-parameters obtained from measurements and from 3D FDTD simulation. The method is developed on a two-port (waveguide-type) fixture and deals with complex reflection and transmission characteristics at the frequency of interest. A computational part is constructed as an inverse-RBF-network-based procedure that reconstructs dielectric constant and the loss factor of the sample from the FDTD modeling data sets and the measured reflection and transmission coefficients.As such, it is applicable to samples and cavities of arbitrary configurations provided that the geometry of the experimental setup is adequately represented by the FDTD model. The practical implementation of the method considered in this paper is a section of a WR975 waveguide containing a sample of a liquid in a cylindrical cutout of a rectangular Teflon cup. The method is run in two stages and employs two databases--first, built for a sparse grid on the complex permittivity plane, in order to locate a domain with an anticipated solution and, second, made as a denser grid covering the determined domain, for finding an exact location of the complex permittivity point. Numerical tests demonstrate that the computational part of the method is highly accurate even when the modeling data is represented by relatively small data sets. When working with reflection and transmission coefficients measured in an actual experimental fixture and reconstructing a low dielectric constant and the loss factor the technique may be less accurate. It is shown that the employed neural network is capable of finding complex permittivity of the sample when experimental data on the reflection and transmission coefficients are numerically dispersive (noise-contaminated). A special modeling test is proposed for validating the results; it confirms that the values of complex permittivity for several liquids (including salt water acetone and three types of alcohol) at 915 MHz are reconstructed with satisfactory accuracy.     

Dielectric Loss in the Polymer–Semiconductor–Composite System with Allowance for Nonlinear Dependence of Electric Characteristics on Temperature Resulting from Microwave Irradiation

An electrothermophysical model that makes it possible to estimate dielectric loss and predict energy-dissipation characteristics in dielectric materials is proposed. Heat and mass transfer is numerically simulated in the presence of microwave irradiation of an electronic device (polymer–semiconductor–composite system) with allowance for local heat liberation and nonlinear dependence of dielectric characteristics on temperature. Distributions of permittivity and tangent of dielectric loss with respect to thickness of the system under study are presented for a typical interval of variations in the parameters of electromagnetic radiation. It is demonstrated that dissipation of electromagnetic energy leads to a significant (by a factor of 1.6) increase in the tangent of dielectric loss.     

X波段介质振荡器的设计

研究了一种具有较宽机械调频范围和较低相位噪声的x波段介质振荡器设计方法.利用介质谐振器法对三种型号的介质谐振器(DR)材料进行了精确的测试,得到了其介电常数εr和损耗角正切值tanδ以及DR的谐振频率.利用仿真软件建立微带线与谐振器耦合模型,通过仿真提取其S2P文件.选用GaAs FET ATF26884作为电路中的放大器件,使用生成的S2P文件建立介质振荡器(DRO)电路模型,调整耦合段和输出匹配微带线的长度,得到较低的相位噪声.测试证明输出信号的相位噪声在偏离中心频率100 kHz处小于-100 dBc/Hz.