Circular Waveguide Structures Research Articles

CSRR-SICW High Sensitivity High Temperature Sensor Based on Si3N4 Ceramics.

A new type of wireless passive, high sensitivity, high temperature sensor was designed to meet the real-time temperature test in the harsh aero-engine environment. The sensor consists of a complementary split ring resonator and a substrate integrated circular waveguide (CSRR-SICW) structure and is based on high temperature resistant Si3N4 ceramic as the substrate material. Temperature is measured by real-time monitoring of the resonant frequency of the sensor. In addition, the ambient temperature affects the dielectric constant of the dielectric substrate, and the resonant frequency of the sensor is determined by the dielectric constant, so the function relationship between temperature and resonant frequency can be established. The experimental results show that the resonant frequency of the sensor decreases from 11.3392 GHz to 11.0648 GHz in the range of 50–1000 °C. The sensitivity is 123 kHz/°C and 417 kHz/°C at 50–450 °C and 450–1000 °C, respectively, and the average test sensitivity is 289 kHz/°C. Compared with previously reported high temperature sensors, the average test sensitivity is approximately doubled, and the test sensitivity at 450–1000 °C is approximately three times higher. Therefore, the proposed high sensitivity sensor has promising prospects for high temperature measurement.

Generation of Coherent terahertz radiation from two-section periodical circular waveguide structure

Generation of Coherent terahertz radiation from two-section periodical circular waveguide structure

Enhancement of output power in a two-section periodical circular waveguide structure using magnetized plasma and a relativistic electron beam

In the present paper, the excitation of electromagnetic wave by relativistic electron beam, as a radiation source, in a two-section periodical plasma waveguide is investigated. The dispersion relation of TM wave is derived and then solved numerically. Next, the effect of plasma, as an extra controlling parameter, on this radiation source is investigated. Results show that the presence of magnetized plasma can lead to significant increase in output power and it can be an extra parameter for tuning the frequency by varying the plasma density.

Propagation Characteristics of Anisotropic <italic>a</italic>-Axis Hollow Lithium Niobate Nanowire

We have investigated the propagation characteristics of anisotropic a-axis hollow lithium niobate nanowire based on a three-layer-dielectric circular waveguide structure by exactly solving Maxwell's equations. The modal characteristics, waveguide dispersion, and nonlinear parameters of the hollow nanowire have been numerically investigated. The numerical results show that the lithium niobate hollow nanowires have some excellent and unique properties, such as the enhanced evanescent field, large dispersion, and high nonlinearity, which are favorable for nonlinear optics applications, such as supercontinuum generation. The results may make inroad toward the miniaturized high-performance linear or nonlinear photonic devices.

Sensor System for Monitoring the Planar Tool Flange Contact on the Basis of Ceramic Resonators and Circular Waveguide Structures

The proposed sensor system based on ceramic resonators and circular waveguide structures offers a novel solution for controlling the quality of tool clamping in a tool-receiving socket interface. Compared to current solutions this sensor system enables both an easy, cost-effective production and a high-resolution passive distance measurement on a rotating system component. The basic element of the monitoring system are standard bores in combination with industrial ceramic pins as well as standard potting compound, through which an electromagnetic signal is transferred to the measurement location.

Учет особенности электромагнитного поля при проектировании цилиндрических волноводных структур для СВЧ-приборов

Учет особенности электромагнитного поля при проектировании цилиндрических волноводных структур для СВЧ-приборов

Propagation characteristic analysis of ridged circular waveguide using 2D finite-difference frequency-domain method

The propagation characteristics of ridged circular waveguides are analyzed by using 2D finite-difference frequency-domain (2D FDFD). Based on the 2D FDFD method in a cylindrical coordinate system, general difference formulas for the ridged circular waveguide are deduced, and modified difference formulas are built at some special points of the ridged circular waveguides. To verify the proposed method, three ridged circular waveguide structures are investigated and the numerical results are compared with available ones obtained by other research methods. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE 15, 2005.

MODAL METHOD ANALYSIS OF MULTILAYERED COATED CIRCULAR WAVEGUIDE USING A MODIFIED CHARACTERISTIC EQUATION

MODALMETHODANALYSISOFMULTILAYEREDCOATEDCIRCULARWAVEGUIDEUSINGAMODIFIEDCHARACTERISTICEQUATIONF.-G.Hu,C.-F.Wang,Y.Xu,andY.-B.GanTemasekLaboratoriesNationalUniversityofSingapore10KentRidgeCrescent,Singapore119260Abstract—In this paper, the modal method is applied to analyzecoated circular waveguide terminated by a perfect electric conductor(PEC) plate. The key to this method is the accurate calculationof the propagation constants of modes in coated circular waveguide.To overcome numerical difficulties, such as overflow, encountered insolvingcharacteristicequation,thecharacteristicequationismodifiedusing Hankel function of the second kind instead of Bessel functionof the first kind in the coated layers. The modified characteristicequationcanbeaccuratelysolvedtoobtainthepropagationconstantseven for very large circular waveguide with highly lossy coatings.To verify the modified characteristic equation, the attenuationand scattering property of circular waveguide structure have beensimulated. Simulationresultsagreewellwiththereferenceresults.1 Introduction2 CharacteristicEquationanditsModification3 ScatteringAnalysisofCircularCoatedWaveguide4 NumericalResults5 ConclusionsReferences

New class of rectangular and circular evanescent-mode waveguide filter

In this paper, a complete design procedure is presented for an original structure of evanescent-mode filters which does not require special tuning techniques or subsequent optimization procedures beyond the design method itself. The method covers the cases of both rectangular and circular waveguide structures. The structure is composed of an air-filled waveguide containing a number of dielectric inserts. It is designed such that the air-filled sections are evanescent, while those with dielectric inserts operate in the normal propagative mode. Furthermore, the interfaces with the external source and load are achieved via a pair of air-filled guides of a propagative nature. The technique consists in finding a scattering description of all the filter sections and junctions relying on an exhaustive electromagnetic study of the field quantities and implying modal analysis methods. This leads to a scattering description of the entire structure and, subsequently, to an approximate lumped equivalent circuit model. This, in turn, is identified with a bandpass filter prototype and the parameters of the waveguide filter (cross section, lengths of sections, and permittivity) are evaluated such that they lead to a close agreement with the response of the prototype. The bandwidth over which the quality of approximation is acceptable is studied in detail and several examples are given for both rectangular and circular filters. Experimental results are also presented indicating that the approach proposed is at the same time accurate and very efficient. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 161–192, 1998.

Radial mode matching analysis of ridged circular waveguides

In this paper a radial mode matching analysis is presented to calculate rigorously the TE and TM mode propagation in single- double-, triple-, and quadruple-ridged circular waveguide structures. The ridges have been cut radially in all the cases. Results are presented for variations of the ridge depth and ridge thickness and are compared to results from finite element analysis. Furthermore, for the first time, the characteristic impedance of the double and quadruple-ridged circular waveguides have been calculated using the power-voltage definition.

Thermal pump saturation in CW optically pumped far infrared lasers

Vibrational-translationally relaxing far infrared (FIR) laser gases are heated by relaxation from the first vibrational state containing the lasing levels to the ground state. This reduces the molecule density, thus leading to a lower effective pump absorption compared with a cold gas. This phenomenon is investigated theoretically by solving the appropriate heat diffusion equation, considering both the traditional circular symmetric waveguide structure and the sandwich (or parallel slab) structure. The most important results are discussed and compared with previously reported experiments. A method is given for an estimation of the effective pump absorption and the excess temperature.

Longitudinal- and transverse-wake-field effects in dielectric structures.

A dielectric-loaded circular waveguide structure is a potential high-gradient linear wake-field accelerator. A complete solution is given for the longitudinal electric and magnetic fields excited by a $\ensuremath{\delta}$ function and a Gaussian charge distribution moving parallel to the guide axis. The fields are then given in the limit of particle velocity equal to the speed of light. Example calculations are given for a structure with inner radius of 2 mm, outer radius of 5 mm, dielectric constant of 3, and total charge of 100 nC. Peak wake fields in excess of 200 MV/m are found. Azimuthal modes 0 and 1 are investigated for the particular interest of acceleration and deflection problems.

Time-domain electromagnetic scattering by open ended circular waveguide and related structure

The axial electromagnetic backscattering by four objects characterized in part by either a circular aperture or circular conducting surface is studied. Impulse response waveforms for finite and open circular waveguides, a circular loop and a thin circular disc are synthesized from exact and/or approximate frequency domain scattering data. Complex natural resonances of the four objects are compared to illustrate similar and dissimilar features. For the open circular waveguide it is demonstrated that approximate scattering solutions for loaded guides in the resonance region can be obtained by properly combining low and high frequency estimates.

Broadbanding of corrugated conical horns by means of the ring-loaded corrugated waveguide structure

Broadbanding of corrugated conical horns is investigated with the ring-loaded corrugated circular waveguide (RCWG) structure devised by the authors. The useful frequency bandwidth in which the corrugated horn is effective for the improvement of antenna properties is limited by the frequency characteristics of the horn-aperture field and input VSWR of the horn. By the precise analysis of the RCWG, the maximum frequency range in which the desirable field is obtained is much wider than that in the conventional corrugated circular waveguide, and is achieved almost independent of ring thickness, when ring width is about 20 percent of slot depth. The characteristic impedance of the RCWG is nearly equal to that of the homogeneous circular waveguide when ring thickness becomes large. Therefore, a good transformer between the RCWG and the homogeneous circular waveguide is achieved by increasing ring thickness from the RCWG toward the homogeneous waveguide. From the above investigations, it is found that in the ring-loaded corrugated horn, the useful bandwidth is 1.35 times broader than that in the conventional corrugated horn. The theoretical results are verified by the experimental results.

Prototype Characteristics for a Class of Dual-Mode Filters (Short Papers)

Selected prototype characteristics of nonequiripple antimetric elliptic-function filters which can be realized in orthogonal cascaded dual-mode circular or square waveguide structures are presented. Cavity-coupling data for 4-, 6-, and S-section 0.01- and 0.05-dB-ripple passband designs with variable stopband levels are tabulated. Quantitative comparisons of elliptic and Chebyshev filter designs are also discussed, indicating the superior characteristics of elliptic networks.

Propagation behaviour of periodically loaded waveguides containing dielectric and ferrimagnetic materials

The propagation behaviour is described of a number of periodically loaded circular waveguide structures containing either dielectric or axially magnetised ferrimagnetic material. The structures include the disc-loaded axial rod and tube. Dispersion characteristics are theoretically determined and the dependence of the lower and upper cutoff frequencies upon various structural and material parameters is studied. For the ferrite structure, two passbands are observed for each mode, one occurring below ferrimagnetic resonance, the other occurring above resonance. The centre frequency of the passband can be varied by changing the strength of the axial applied magnetic field. Experimental dispersion characteristics are shown for both dielectric and ferrite structures, and these are found to agree well with those predicted theoretically.