Query: Coaxial Cavity Resonator

title: Computational approach for resonant frequency calculation of coaxial cavity resonator using cylindrical coordinate system based FDTD method
abstract: A computational approach for resonant frequency calculation of coaxial cavity resonator using a cylindrical coordinate system based finite difference time domain (FDTD) method is presented. Due to the geometry shape of analyzed structure, i.e. coaxial cavity resonator, the use of FDTD method with cylindrical coordinate system is chosen instead of Cartesian coordinate system. A coaxial cavity resonator made of perfect conductor with outer diameter of 100mm, inner diameter of 40mm and length of 150mm is modeled and discretized based on FDTD notation and then numerically computed to determine its resonant frequencies in the frequency range of 1 5GHz. Moreover, a simulation using finite element method (FEM) commercialized software is also conducted to determine resonant frequencies of the resonator for comparison. From the results, it shows that the proposed FDTD approach demonstrates the capability to determine resonant frequencies of coaxial cavity resonator with an acceptable accuracy compared to the FEM commercialized software in the maximum discrepancy around than 3%

title: Dual signal coaxial cavity resonator plasma generation
abstract: The plasma generator comprises a radio frequency power supply source, a coaxial cavity resonator assembly, a DC power supply. Radio frequency power source provides a voltage supply of the radio frequency power having a first ratio of the power with respect to the voltage. Resonator assembly includes an intermediate conductor which is coupled to a radio frequency power source, also including a virtual short circuit. DC power supply source is connected to the intermediate conductor at a virtual short circuit, to provide a voltage supply of the DC power having a second ratio of power to a voltage less than the first ratio.

title: Dielectric characterization of powdery substances using an indirectly coupled open ended coaxial cavity resonator
abstract: The main objective of this thesis was to research and develop a sensitive characterization method for dielectric powdery substances which could be utilized in various industrial and research fields. With modern electromagnetic simulation tools and the presented experimental measurements, the characterization of dielectric powders using an indirectly coupled open ended coaxial cavity resonator operating in TEM mode at 4.5 GHz was found to have potential. The modelling and the experimental measurement results of commonly used dielectric powders revealed that, from the nine classical mixing rules, it was possible to derive reliable inclusion permittivity values when using the properties of the perturbed resonator and the Bruggeman symmetric and the Looyenga mixing theories. In addition, the determination accuracy of the inclusion permittivity was found to be greatly improved with the correction factor included into the previously presented permittivity equation of the quarter wave coaxial resonator. Determination of the dielectric losses was found to be reliable when using the differences between the perturbed and unperturbed resonator and the general mixing model equation. The sensitivity of the characterization method was researched with both humidity exposed and surfactant treated modified SiO2, Al2O3 and ZrO2 powders. Experimental results showed that the effect of adsorbed water on the particles was most pronounced when measuring the dielectric losses of the inclusions. Furthermore, a clear correlation with the theory of the general mixing model was found. Thus, in addition to the changed dielectric properties between dry and humidity exposed powders, it was also possible to determine the moisture content with reasonable accuracy. This correlated well with the traditional, mass based, determination. Stearic acid coating of the particles induced only a small change in inclusion permittivity but a notable change in dielectric losses. Unlike the cases with the larger particle sized SiO2 and Al2O3, the dielectric loss of ZrO2 inclusions, with stearic acid coating, was decreased significantly from 6.2 x 10 3 to 3.8 x 10 3. When characterizing magnesium and calcium titanate composite powders, with CaTiO3 molar ratios of 0.0, 0.02, 0.05 and 0.1, the method was found to have good sensitivity and accuracy. Additions of CaTiO3 exhibited a clear increase in net inclusion permittivities from 13.4 up to 14.9 and in dielectric loss tangents from 7.1 x 10 3 up to 8.5 x 10 3. In addition, a good correlation was found in the theoretical determination of the CaTiO3 molar ratios using the resonator measurement results and the general mixing model. The characterization method was proved to be capable of measuring the dielectric properties and detecting even very slight changes in the powders. Thus, the method could be utilized in various types of powdery material characterization, for example, in the analysis and quality control of different composite powders.

title: Determination of complex permittivity of surfactant treated powders using an open ended coaxial cavity resonator
abstract: An indirectly coupled open ended coaxial cavity resonator was used to detect the effect of stearic acid surface treatments on the dielectric properties of powders in the frequency range 2.17 3.79 GHz. The Bruggeman symmetric and Looyenga classical mixing rules and a general mixing model were used to determine changes in permittivity and loss tangent of the inclusions. Surfactant processed powders with stearic acid 0.05 1.36 vol. induced only a small change in inclusion permittivity but caused a notable change in dielectric losses. The dielectric loss tangents of SiO2 and Al2O3 increased from 2 x 10 4 to 4 x 10 4 and 5 x 10 3 to 6.1 x 10 3, respectively. However, a significant decrease in dielectric loss tangent, from 6.2 x 10 3 to 3.8 x 10 3, was noted with surfactant treated ZrO2. The investigated novel characterization method proved to be able to detect even very slight changes in dielectric properties to be utilized in various types of powdery material characterization, e.g. in composite applications and material quality monitoring.

title: Study on the empirical design of open ended coaxial cavity resonator
abstract: This article is a study of an empirical design of an open ended coaxial cavity resonator. The coaxial cavity resonator can be designed using the coaxial transmission line theory. It can be done by using the radius of the inner conductor, the inner radius, and the length of the resonator. However, the basic coaxial transmission line theory can be seen that the characteristics of the resonant frequency and the Q value are varied by the change of length, regardless of the value of radius of the inner conductor and inner radius of the resonator. We find out the impact of radius of the inner conductor, inner radius of the resonator, and the length of the resonator parameter and propose the optimized empirical resonator design method by reducing the error between the theoretical value and the design value. High frequency structure simulator was used for simulation and the material of the resonator was designed with a copper. Based on the simulation, several resonators are fabricated by the size of 14 mm for the radius of inner conductor, 2, 5, and 10 mm, respectively, for the inner radius of resonator, and 8.5 mm for the length of the resonator. The resonant frequencies of the produced resonators were measured at 6.1, 5.7, and 6.5 GHz, respectively. According to the result of simulation and measurement, we know that we can design the relatively exact open ended coaxial cavity resonator by applying the basic coaxial transmission line theory directly when the length of the resonator is less than 10 mm, and adding the correction factor of 0.5 GHz to the calculated resonant frequency in case of more than 10 mm of the length of the resonator.

title: Electromagnetic oscillations in a coaxial cavity resonator filled with a nonlinear nondispersive medium
abstract: Nonlinear resonators are interesting models of physical systems and have been studied extensively in many theoretical and experimental works. A variety of existing electronic devices and materials with nonlinear electromagnetic properties makes it possible to create electrical resonators with different types of nonlinearity. It is well known that fairly complex, e.g. chaotic, oscillations can be excited in nonlinear resonators. Much previous theoretical work on the subject deals with the analysis of nonlinear resonators as lumped systems or merely as a collection of coupled oscillators or modes. Within the framework of such an approach, the problem of oscillations in a nonlinear resonator is reduced to solving a system of ordinary differential equations. Although such a simplified approach is justified in many cases, it is clear that electromagnetic systems should generally be described by the Maxwell equations. In this work, the problem of free oscillations in a nonlinear electrical resonator is considered using a full set of the Maxwell equations. To solve this problem, we apply the method for constructing exact axisymmetric solutions of the Maxwell equations in a nonlinear nondispersive medium, which has been developed in our recent work (E. Yu. Petrov and A. V. Kudrin, Physical Review Letters, 104, 2010, p. 190404) to the oscillations in a bounded coaxial volume.

title: A short ended CRLH coaxial cavity resonator with zeroth order resonance
abstract: This paper introduces a coaxial cavity resonator structure with a new configuration based on the composite right/left handed transmission line (CRLH TL) In order to create the CRLH TL, the shunt inductance coils and the series capacitance gaps are added to a conventional half wavelength short ended coaxial cavity resonator. The final resonator is composed of three periodically connected CRLH unit cells. Through the adjustment of the diameter of the inserted coils and the gaps of created capacitances, the proposed resonator was able to support the desired zeroth order resonance (ZOR) in the balanced mode. In order to verify the applicability of the proposed resonator to the CRLH metamaterial, a dispersion diagram and the constitutive parameters of a unit cell were determined using three dimensional EM simulation. The resonant frequencies and quality factors associated with each resonance modes were then computed through eigenmode analysis for the overall resonator formation. In addition, the electromagnetic field distributions of the resonator at the ZOR frequency have been described and discussed. These results enable us to validate that the proposed CRLH coaxial cavity resonator can be utilized as a zeroth order resonator based on the CRLH TL structure. As a result the proposed resonator has a 69% reduction in size compared to traditional short ended coaxial cavity resonators.

title: Design of Miniaturized Coaxial Feed Patch Antennas with Air Cavity or Surface Integrated Resonator for UWB/WiFi/ Wireless /GPS
abstract: Antenna miniaturization, which is a requirement of modern wireless communication systems, is usually concomitant with the reduction of impedance bandwidth. On the other hand, small antennas should also possess stable radiation patterns across a broad frequency band, such as in the UWB systems. In this paper, we propose a UWB antenna structure with a novel feeding system composed of an open cavity resonator. It has a wide relative bandwidth (of about 120% particularly at the lower frequency limits. proposed antenna with the novel feed system is smaller and has a wider frequency bandwidth, as compared with other available UWB antennas in the literature. Furthermore, another antenna is proposed, which has a feeding system composed of a surface integrated resonator cavity, fabricated on a two layer microstrip structure. It has achieved better miniaturization and bandwidth enhancement, albeit somewhat lower gain. Three prototype models of the proposed antennas are fabricated and measured, of which the frequency response are in excellent agreement with computer simulation results.  Antenna Miniaturization, UWB, GPS, WiFi, Wireless, Surface Integrated Resonators, Patch Antenna.

title: A Multi Evanescent Mode Coaxial Cavity Resonator
abstract: This paper presents a novel miniaturized multi evanescent mode resonator. The resonator is achieved with a coaxial cavity. This coaxial cavity essentially has a direct short connection at one end and is connected with several lumped capacitances at the other end. The key technology of the resonator is the usage of multiple evanescent modes of TM (transverse magnetic wave) modes. Due to the combined efiects of the evanescent mode and multiple modes, the size of the resonator is greatly reduced. In this paper, the theory of resonator is discussed in detail. To verify the correctness of operation, the resonator is used in experimental measurements conducted to realize a third order band pass fllter based on SIW (substrate integrated waveguide) technology. The measured results are found to agree with the theoretical values.

title: Frequency dependence of the microwave surface resistance of MgB2 by coaxial cavity resonator
abstract: We report on the microwave (mw) properties of a cylindrical MgB2 rod prepared by the reactive liquid Mg infiltration technology. The MgB2 rod, 94.3 mm long, is used as inner conductor of a coaxial cavity having a Cu tube as external conductor. By analyzing the resonance curves of the cavity in the different resonant modes and at different temperatures, we have determined the temperature dependence of the mw surface resistance, R s of the MgB2 material, at fixed frequencies, and the frequency dependence of R s at fixed temperatures. Our results show that the R s f curves follow a f n law, where n decreases on increasing the temperature, starting from n 2 at T 4.2 K down to n 0.7 at T T c The double gap nature of MgB2 manifests itself in the presence of a wide low T tail in the R s T curves, which can be ascribed to the quasiparticles thermally excited through the p gap even at relatively low temperatures.