Multilayer Resonator Research Articles

Compound piezoelectric cylindrical resonators as sensors of the rheological parameters of viscoelastic media

The electro-elastic behavior of a viscoelastically loaded layered cylindrical resonator (sensor) comprising two coupled hollow cylinders is presented. The inner cylinder is a piezoelectric ceramic tube. The outer cylinder is a non-piezoelectric (passive) metallic cylinder. An analytical formula for the electrical admittance of a compound layered cylindrical resonator loaded with a viscoelastic liquid is established. Admittance (conductance) diagrams were obtained using a continuum electromechanical model. The established analytical formulas enable the determination of the influence of the liquid viscosity, material, and geometrical parameters of a compound cylindrical resonator on the response characteristics of the compound sensor. In the paper, the sensor implications resulting from the performed analysis are described. Moreover, the algorithm of the method developed by the authors to evaluate the rheological parameters of a viscoelastic liquid is presented. Good agreement between the theoretical results and experimental data is shown. The analysis presented in this paper can be utilized for the design and construction of cylindrical piezoelectric viscosity sensors, annular accelerometers, filters, transducers, and multilayer resonators.

The role of dipolar interactions in magnetic nanoparticles: Ferromagnetic resonance in discontinuous magnetic multilayers

We have performed detailed ferromagnetic resonance (FMR) studies of [Co80Fe20(t)∕Al2O3(40 Å)]10 (t=7−13 Å) discontinuous multilayers, with measurements taken as a function of the angle of the applied static magnetic field with respect to the sample at room temperature. We outline an approach to FMR in granular systems by using the magnetic dipolar interaction between magnetic nanoparticles. This can be easily incorporated into the free energy of the system and provides a method for evaluating the average interaction strength in particulate media. Angular dependent measurements show how FMR can be used to evaluate interparticle interactions. Our measurements indicate that there is a change of coupling regime, going from superferromagnetic, for thicker samples (with larger average particle sizes and smaller separations), to superparamagnetic in thinner samples.

Multilayer Planar Resonators with Superconductive Patch on PBG Substrate

The rectangular discretized multilayer microstrip resonators, analyzed using the full wave TTL | Transverse Transmission Line method in the spectral domain, jointly with the moment method are presented. The homogenization theory is used to calculate the equivalent permittivity for the s and p polarizations of the structure composed of PBG (Photonic Band Gap) material. Numerical results of the resonance frequency for the rectangular multilayer, on isotropic and anisotropic PBG material substrate resonators are presented. DOI: 10.2529/PIERS060908155123 The microstrip antennas have received more attention due to the characteristics and advantages comparison with the conventional antennas. These antennas present small volume, reduced weight, planar conflguration, compatibility with integrated hybrid circuits and the possibility of acting with dual frequency (1). They can be used in several systems, such as: radars, wireless, mobile telephony and communication by satellites. However, they present disadvantages with relationship to the narrow band, losses due to the low gain and losses by irradiation due to the surface waves. These disadvantages can be eliminated, by using a screening to avoid losses by irradiation (2) and antennas with PBG substrate (Photonic Bandgap) (3). Some techniques to increase the band width are used among the: thicker substrate (4), multilayer antennas or stacked patches (5,6). Antennas with dielectric multilayer have advantages, such as, the ∞exibility in the operation frequency band, a smaller physical size, etc. The PBG materials are a new type of periodic substrates structure in which the propagation in certain bands of frequencies is prohibited (7). In this work the rectangular multilayer resonators on PBG substrate are analyzed, as illustrated in the Fig. 1.

Shape and Material Selection for Optimizing Flexural Vibrations in Multilayered Resonators

Flexural stiffness domains have been determined for optimizing the vibration frequency of a multilayered microresonator. It is demonstrated in an efficiency map that, for a given eigenvalue, the flexural properties of a two-materials system, including all possible symmetric and asymmetric multiple-layers arrangements, fall into a domain limited by two curves. These low and upper boundaries describe symmetric three-layers systems consisting of two dissimilar materials. The flexural response model adopted in this paper is based on the Euler-Bernoulli theory, and the results are obtained by extending a scheme for modeling efficiency of monolithic structures (see D. Pasini, transformers for material and shape selection of lightweight beams, J. Mater. Design, 2006). Shape parameters are introduced to explore the impact on the resonator vibrations of the cross-section shape, the arrangement, symmetry and number of layers, as well as the materials properties and their volume fraction. The application of the maps to a case study shows that the method can assist to exploit geometry and material potential of microstructures, especially at the concept stage of design

Multilayer Design Techniques for Extremely Miniaturized CMOS Microwave and Millimeter-Wave Distributed Passive Circuits

Multilayer design techniques are investigated for reducing the size and enhancing the performance of microwave and millimeter-wave distributed circuits in CMOS. Various distributed passive circuits are implemented in a standard 0.25-mum RF/mixed-signal process, including a novel broadside-coupled Lange coupler, a microstrip ring hybrid, and a hairpin resonator incorporating a complementary slow-wave structure. The broadside-coupled Lange coupler exhibits -3.3 to -3.35 dB through, -3.3 to -3.7 dB coupling, more than 12-dB isolation, and 15-dB return loss across 25-35 GHz while occupying only 217 times185 mum of chip area. The multilayer ring hybrid has -3.1 to -3.18 dB through, -5.1 to -5.7 dB coupling, and more than 17-dB isolation and 10-dB return loss from 25-35 GHz while occupying 282 times314 mum. A slow-wave structure based on multilayer complementary design principle is implemented for hairpin resonators. The measured quality factor of the multilayer complementary slow-wave hairpin resonator increases to about 14.5 from 11.3 for a similar sized resonator with a single-layer slow-wave structure, while retaining similar size-reduction properties as the latter

A Broadband Single-Stage Equivalent Circuit for Modeling LTCC Bandpass Filters

A single-stage equivalent circuit is proposed to model microwave bandpass filters (BPFs) fabricated in low-temperature co-fired ceramic (LTCC) technology up to several times its passband frequency. The equivalent circuit adopts a modified T topology with the expandable multilayer resonators to achieve an extremely large bandwidth. It can be efficiently established from the measured S-parameters using direct extraction or rational approximation. As a result, the modeled S-parameters for a 2.45-GHz wideband local area network (WLAN) LTCC BPF show good agreement with the measured results over a wide frequency range up to 8.5 GHz. Such a broadband model can be used to accurately predict the suppression of harmonics and interferences in system simulation of the WLAN front-end modules

Trapping of acoustic energy in composite resonators based on cubic crystals

An analytic solution is obtained for the problem of acoustic energy trapping in a microwave composite resonator containing a thick cubic-crystal plate with a deposited piezoelectric film and electrodes. It is found that rigorous account of the wave properties of the piezoelectric film and electrodes is of principal importance for such a structure. The problem is solved in the case when the operating frequency is a high-order harmonic of the fundamental frequency of the resonator and the resonator is much thicker than the other layers. The formulas obtained make it possible to analyze the feasibility of a multilayer resonator structure with a high Q-factor at a desired frequency.

Very low-refractive-index optical thin films consisting of an array of SiO_2 nanorods

The refractive-index contrast in dielectric multilayer structures, optical resonators, and photonic crystals is an important figure of merit that creates a strong demand for high-quality thin films with a low refractive index. A SiO2 nanorod layer with low refractive index of n = 1.08, to our knowledge the lowest ever reported in thin-film materials, is grown by oblique-angle electron-beam deposition of SiO2. A single-pair distributed Bragg reflector employing a SiO2 nanorod layer is demonstrated to have enhanced reflectivity, showing the great potential of low-refractive-index films for applications in photonic structures and devices.

Q-factor evaluation, design and accurate EM performance of multilayer dielectric filters

In this contribution we present the design of an optical dielectric multilayered filter by using a transmission-line prototype. Each resonator of the prototype is realized by means of a stack of dielectric layers by equating the Q-factor of the stack with that of the corresponding resonator of the prototype. We then compare the analytical results with numerical ones obtained by the finite element method (FEM). We extend the theory to a structure formed by periodic multilayer resonators. Copyright © 2006 John Wiley & Sons, Ltd.

Admittance loci design method for multilayer surface plasmon resonance devices

Dielectric mirror types of multilayer structures have been applied to enhance the performance of surface plasmon resonance (SPR) devices. It demands a more robust design method than traditional Fresnel's equations. An admittance locus is a kind of optical thin film design method which has been extensively used for high performance optical coatings. We have applied this method for the design of multilayer SPR devices, including symmetric (glass|Au(40 nm)–[TiO 2(20 nm)–SiO 2(20 nm)] 4–Au(30 nm)) and asymmetric (glass|Ag(50 nm)–[TiO 2(20 nm)–SiO 2(20 nm)] 4–Au(20 nm)) structure. It provides a much necessary guidance for the choices of suitable optical materials, thickness, and number of layers for the intended SPR performance. With a 633 nm light source and a BK7 coupling prism under water, one can shift the resonant angle toward the critical angle and have smaller half maximum band widths (HMBW) at (64°, 2°) and (61.52°, 0.25°) for symmetric and asymmetric designs, respectively.

광학 어드미턴스 기법과 진화 알고리즘 기법을 이용한 다층 표면 플라즈몬 공명 센서의 설계

This paper describes the optimal design of a multi-layered surface plasmon resonance sensors to meet various specifications and improve some physical parameters. Dip 3 dB bandwidth and depth were chosen as design parameters and the objective function was the norm of the difference between design parameters and target values. The design variables are thicknesses of each layer and to obtain the design parameters, the optical admittance method was employed. The (1+1) evolution strategy was employed as an optimization tool. By applying the proposed optimization procedure to a 3-layered sensor, the optimized design variables considerably improved the 3 dB bandwidth by 4.8 nm and the dip depth by 1.1 dB.

Silica Nanorod-Array Films with Very Low Refractive Indices

The refractive-index contrast is an important figure of merit for dielectric multilayer structures, optical resonators, and photonic crystals. This represents a strong driving force for novel materials that have refractive indices lower than those of conventional optically transparent materials. Silica nanorod-array dielectric films with unprecedented low refractive indices of 1.08 are demonstrated and shown to have viable optical properties including enhanced reflectivity of a single-pair distributed Bragg reflector.

Study of cylindrical multilayered ceramic resonators with rectangular air cavity for low-phase noise K/Ka-band oscillators

This paper first presents cylindrical low-temperature co-fired ceramic (LTCC) resonator configurations as a means of achieving high-Q values at millimetric frequencies in a reduced-size structure. The resonator contains a rectangular air cavity that only partially fills its volume. Simple analytical expressions are derived, which relate the via waveguide (VWG) heterogeneous structures to their conventional cylindrical resonator counterparts through the use of effective radius and dielectric constant (a/sub eff/ and /spl epsiv//sub eff/). A parametric analysis is then carried out showing the effects of the available design parameters on resonant frequency and Q. Excellent agreement between measured and analytical results is obtained. Finally, a low-cost miniaturized low phase-noise free-running oscillator is proposed by employing the novel high-Q VWG resonator in the same LTCC package that houses the monolithic oscillator active circuit. A 24-GHz low phase-noise oscillator is then carried out with an output power of 13.3 dBm and a phase noise of -106 dBc/Hz at 100-kHz offset, which is among the best results ever published for a free-running K/Ka-band oscillator.

Observation on the Visibility Decrease in a VCN Spin Resonator Interferometry.

The present paper reports on the detailed studies concerning the neutron spin interference visibility observed after transmitting through multilayer magnetic resonators in a spin echo condition with very cold neutrons from a high flux reactor. The observed visibility of the interference between upward and downward spin components perpendicular to the Larmor precession plane of the neutron spin are compared with the numerical simulations in the plane wave theory and also in the Schrödinger wave-packet model. The comparison revealed the instructive characteristic features of obvious additional visibility decrease observed in the interference between the tunnelling and refractive transmissions of each spin components in a single as well as a couple of multilayer magnetic resonators.

Optical Thin Films with Very Low Refractive Index and Their Application in Photonics Devices

AbstractThe refractive index contrast in dielectric multilayer structures, optical resonators and photonic crystals is an important figure of merit, which creates a strong demand for high quality thin films with a very low refractive index. SiO2 nano-rod layers with low refractive indices n = 1.08, the lowest ever reported in thin-film materials, is grown by oblique-angle e-beam deposition of SiO2 with vapor incident angle 85 degree. Scanning electron micrographs reveal a highly porous columnar structure of the low-refractive-index (low-n) film. The gap between the SiO2 nano-rods is ≤50 nm, i.e. much smaller than the wavelength of visible light, and thus sufficiently small to make scattering very small. Optical micrographs of the low-n film deposited on a Si substrate reveal a uniform specular film with no apparent scattering. The unprecedented low index of the SiO2 nano-rod layer is confirmed by both ellipsometry measurements and thin film interference measurements. A single-pair distributed Bragg reflector (DBR) employing the SiO2 nano-rod layer is demonstrated to have enhanced reflectivity, showing the great potential of low-n films for applications in photonic structures and devices.

Light amplification from Cantor and asymmetric multilayer resonators

The light amplification properties of fractal and asymmetric multilayer resonator structures which contain a light amplifying medium in the middle layer are studied theoretically. The amplitude gain of transmitted light is analyzed by use of two-dimensional plots which we denote gain maps. The gain map, which is plotted against two different structural parameters, illustrates some regularities in the location of gain peaks and bandgaps. Cantor structures exhibit gain peaks at the edges of multiple bandgaps, and those peaks are higher and sharper than those of periodic structures. Asymmetric resonator structures are found to provide more gain than symmetric ones when the gain length is short. A comparison between the gain and the group velocity of light is also presented, together with the electromagnetic energy distributions in the multilayers.

Sensitivity evaluation of a multi-layered surface plasmon resonance-based fiber optic sensor: a theoretical study

A multi-layered surface plasmon resonance (SPR)-based fiber optic absorption sensor has been studied theoretically. The sensitivity is evaluated for the p-polarized light launched in the fiber using ray approximation. Four-layers configuration is used to excite the surface plasmon wave. The first layer or the medium considered is the core of the fiber. Second and third layers are metallic (silver and gold). The fourth layer or medium is absorbing medium. The effect of the ratio of the thickness of the metallic layers (silver:gold) on the sensitivity of the sensor has been investigated. The sensitivity increases as the silver to gold thickness ratio increases. The gold should be used only to protect silver layer. In addition, the influences of various parameters like numerical aperture (NA), ratio of sensing region length to fiber core diameter, total bimetallic thickness, maximum absorption wavelength, and half maximum width of the sensing medium on the sensitivity of the sensor have been studied. It has been found that the sensitivity is better for the lower off-resonance excitation frequency. Replacing gold by self-assembled monolayers like thiol does not improve sensitivity much. Further, adding ZrO 2 as the fourth layer does not improve the sensitivity of the four layers configuration.

Optimization of MgTiO 3–CaTiO 3 based LTCC tapes containing B 2O 3 for use in microwave applications

Optimization of MgTiO 3–CaTiO 3 based LTCC tapes to be used for microwave purposes was investigated. Three kinds of MgTiO 3–CaTiO 3 based powders containing B 2O 3 in different forms, and two different slurry systems (PVB and PM) were prepared for tape casting. The results clearly demonstrated that if the powder contained ‘free’ B 2O 3, no proper tape could be fabricated regardless of the slurry system. With other powders containing pre-reacted B 2O 3, dense tapes as well as multilayer strip line resonators could be fabricated. Difficulties to prepare proper tape from the powder containing ‘free’ B 2O 3 and different tape properties with different slurry systems are studied and discussed.

Multilayer Ceramic Resonators Using a Flexural Vibration Mode and their Application to Filters

Multilayer ceramic resonators using a piezoelectric longitudinal-effect flexural vibration mode have been developed. The resonators are able to be designed in a much smaller format while maintaining high performance than the multilayer longitudinal resonators which we previously presented. Utilizing internal divided electrodes and floating electrodes makes it possible to generate a flexural vibration mode without complicating the process of connecting electrodes or polarizing. The relationship between the ratio of piezoelectric area in the length direction and the bandwidth, and the effects of the gap and distance from the internal electrodes on the resonator characteristics, are analyzed by the finite element method. Resonators and ladder filters are investigated and their superior characteristics and small size have been demonstrated.

Multilayer microwave resonators with Bi-based dielectric ceramics

Multilayer microwave resonators were fabricated using low temperature (∼950 °C) sintered Bi-Based dielectric ceramics with high permittivity (>80). A simple structure with input/output terminals was designed with stripline to couple the resonators to external circuit. In this structure, gap-coupling capacitors were used to couple the input/output terminals to external circuit. Effect of coupling gap, the length of input/output pads and other sizes of the resonators on the resonant frequency and Q-value of the resonators was studied. The Q-value of one-port resonator is higher than 200 at 1.887 GHz and that of two-port resonators is higher than 80 at 960 MHz.