Wall Of Waveguide Research Articles

Wake excitation by a powerful microwave pulse and its evolution in a plasma-filled waveguide

We present the results of an experimental, theoretical, and numerical study of short and long time wake, produced by a 0.6 ns, 0.5 GW, 9.6 GHz high power microwave (HPM) pulse propagating in a plasma-filled cylindrical waveguide. The perturbation of the plasma density caused by the ponderomotive force prevents not only the pulse from spreading due to dispersion, but also leads to pulse compression. The high power pulse leaves far behind it a long lived positively-charged plasma whose electrons oscillate in the Coulomb potential well and ionize the background neutral gas over several tens to hundreds of nanoseconds. This leads to long time light emission observed in the experiment. The density of this newly created plasma can exceed many-folds its initial value. The theoretical model shows that as a result of the wake excitation by the propagating HPM pulse, fast electrons are ejected and collected on the waveguide wall. These high energy electrons, pulse compression, and long time light emission are evidence of the wake formation. The results of the experiment, the analytical model, and the numerical simulations are in good agreement.

Strong enhancement and inhibition of the interatomic van der Waals interaction inside a cylindrical waveguide

We consider the van der Waals interaction between two ground-state atoms, placed inside a cylindrical waveguide. It is shown that the interaction can be enhanced or suppressed by several orders of magnitudes. Even though the effect is most spectacular for an ideal perfectly reflecting wall, it survives when realistic properties of the wall materials are taken into account. Different types of the waveguide wall, including perfectly reflecting wall, walls made of gold and silicon, and Bragg-distributed wall are compared. It is shown in particular that the van der Waals interaction is inhibited by material absorption.

Методика расчета на прочность волноводов для обеспечения улучшенных массогабаритных параметров

This paper presents a calculation procedure for designing waveguides with iproved mass-dimensional parameters, which ensures the required strength and stiffness characteristics under static, dynamic and deformational loads. The procedure is based on the analysis of methods for determining the stress-strain state of the waveguide-and-distribution systems of spacecraft. The first stage of the procedure involves modelling the waveguide-and-distribution systems in a general formulation by a rod structure with equivalent loading and fixing conditions and determining the stress-strain state of such a system. At the second stage, local areas with the maximum stress-strain state values are selected for a further refined analysis in the rod system. An evaluation of the influence of the waveguide wall thickness on the general stress-strain state is performed. It is shown that when the waveguide wall thickness varies in the range of 0.25 – 2.50 mm, the strength and stiffness of its sections under static loads basically follow the linear law. It is established that under dynamic loading the wall thickness has almost no effect on the resultant stress-strain state of the waveguide arising under the influence of forced fluctuations and quasi-static loading owing to its dependence on the ratios of mass, moments of inertia and resistance, which for some standard sizes of the waveguides will be almost constant. The equations obtained for the rod system cannot be used for evaluating the influence of the wall thickness on local stress-strain state in the form of wall deflection, local loss of stability, etc. In view of this, at the second stage of modelling local areas of interest are selected and transformed into 3D thin-walled structures, with translation into finite element method programs for a more exact analysis. In the future, the proposed technique can be used to solve connected problems of interrelation and the influence of cross-sectional deformations in local zones of the waveguide on the changes in electromagnetic fields with the formation of parasite waves. This will significantly improve the quality of radio engineering characteristics of the waveguide and distribution systems while ensuring their strength, stiffness and minimal mass-dimensional parameters.

Fully 3D time-dependent simulation of free electron laser within an overmoded rectangular waveguide

Numerical simulation codes are basic tools for designing Free Electron Lasers (FELs). This paper describes a numerical approach for the time-dependent, three-dimensional simulation of the free electron laser (FEL) using a rectangular waveguide within overmoded configuration when the radiation wavelength is much shorter than the waveguide cut-off wavelength. Instead of developing a new code, the Genesis simulation code is modified for our purpose. This approach presented here can be used for extending the capacity of Genesis code to cover this special configuration. The major modification is to apply the boundary conditions on the waveguide walls to the steady-state radiation field equations in a limited rectangular region and the full Cartesian mesh using the Alternating Direction Implicit (ADI) integration scheme to solve the field equation remains adopted.

Design of a Slotted Waveguide Antenna by Means of VBScript Scripting Language Macros in CAD Ansys HFSS

Introduction. Modern antenna devices contain a large number of repeating elements. The process of development of CAD models of such devices requires repeatedly performed operations that is a routine task for an engineer. Therefore, the problem of repeating operations automation arises when constructing antenna models with periodic structures.Aim. To demonstrate the automation of slotted waveguide antennas design process in CAD Ansys HFSS.Materials and methods. In order to determine the dimensions of the slotted waveguide antenna the energy method was used. Automation procedure of the design of the slotted waveguide antennas in CAD Ansys HFSS using the Visual Basic Scripting Edition macros was presented.Results. In order to design and edit slotted waveguide antennas in CAD Ansys HFSS four macros in the VBScript language were established: for slot subtraction from a broad wall of a rectangular waveguide at given coordinates; for removing the original slots created using the previous macro; for drawing a polyline passing through the centers of the slots, in order to verify the antenna’s near field realized distribution; for inclined slot subtraction from a narrow wall of a rectangular waveguide at given coordinates. Results of the macros usage were presented.Conclusion. The above mentioned macros allow one to automate the routine steps during the process of creating and deleting objects while designing an antenna model with periodic structures in CAD Ansys HFSS. Specified procedures for creating macros could be extended to a wide class of tasks related to the studies of characteristics of electromagnetic structures including repeating objects (phased antenna arrays, reflective arrays, slotted waveguide antennas, fractal antennas, log-periodic antennas, multi-layer lens antennas, ladder-type microwave filters).

A Compact $Q$ -Band Rectangular Waveguide Thermal Isolator

We present a new waveguide thermal isolator, based on a simple gap in a standard rectangular waveguide, developed for the $Q$ -band cryogenic receiver of the Sardinia Radio Telescope. The proposed component is very compact and consists of a single module, including both the horizontal and vertical polarization channels and the noise injection channel. The electromagnetic and thermal characteristics of this isolator have been fully investigated. High return loss and low insertion loss are obtained solely by a proper selection of the waveguide wall thickness, thus resulting in a very simple design, easily scalable in the whole microwave range. High robustness to misalignment and excellent thermal performance are achieved. A prototype of the proposed isolator has been manufactured and tested at room temperature, showing a very good agreement with predicted performance.

SLA-Printed 3-D Waveguide Paths for E-Band Using Electroless Silver Plating

This paper proposes a fabrication approach for 3-D printed waveguide paths based on a combination of an optimized electroless silver plating process with a waveguide-specific design rule for general metal plating by introducing large-scale non-radiating slots into the broad and narrow waveguide walls with a periodicity shorter than a quarter of the guided wavelength. Experimental fabrication of straight sections of the proposed slotted waveguide with various gap dimensions yields an optimum gap size as a result of a tradeoff between silver plating quality and leakage losses through the sidewall gaps. Moreover, a successful practical application of the proposed approach is presented in terms of a 3-D printed multiple bend waveguide interconnect in three different space dimensions, which imposes a complex task for conventional manufacturing techniques due to the need of multiple cutting planes for split block assembly. The proposed approach has the benefits of low cost, moderate handling effort, and independence of the concrete geometry to manufacture, making it, therefore, especially interesting for distribution and feeding networks in the context of rapid prototyping, automotive, and space-related applications.

X-ray LIGA Microfabricated Circuits for a Sub-THz Wave Folded Waveguide Traveling-Wave-Tube Amplifier

We report experimental results on the microfabrication of three types of folded waveguide circuits with a high aspect ratio by using a high-energy X-ray LIGA technique. A W-band folded waveguide with a total of 80 periods was designed for a traveling-wave-tube (TWT) amplifier operating at 90 GHz–100 GHz. The measured return loss and insertion loss of the W-band fabricated circuit were–10 dB and 0.42 dB/cm, respectively. A G-band circuit showed a higher insertion loss of 1.57 dB/cm. An additional circuit fabrication for a 850-GHz folded waveguide TWT was also successfully carried out. The broad-wall angle measured with respect to the narrow wall of the rectangular waveguide was very close to 90◦, indicating an excellent resolution compared to that of other microfabrication techniques, such as deep reactive ion etching (DRIE) and ultraviolet (UV) lithography, electroplating, and polymer replication (LIGA).

Nanopatterned evanescent-field fiber-optic interferometer as a versatile platform for gas sensing

We introduced a nanopatterned fiber-optic interferometer (FOI) based on an optical fiber line embedded with a short capillary which excites the evanescent field by total reflection of light in the wall waveguide interacting with the fluid and causing the optical signal change. As modal interference was generated with near-infrared light in the tube wall, we detected a reversible wavelength shifts of the proposed FOI in the interference fringe upon water vapor exposure by using an optical fiber interrogator. We also deposited a patterned palladium (Pd) nanoparticle film on the outer surface of the FOI by using self-assembly microspheres as a template and detected the reaction of the Pd membrane with hydrogen through monitoring the wavelength shifts of interference fringes. The Pd nanoparticle restrained the fiber stress response caused by hydrogen-induced expansion of the Pd film, and theoretically helped to improve the evaluation accuracy of the Pd permittivity in hydrogen. In addition, the nanoparticle-coated FOI with asymmetric structure could serve as a Mach-Zehnder interferometer (MZI) for fast hydrogen sensing and air refractive index measurement. Considering sensitivity and detector parameters, the FOI could provide a high resolution up to 7.57 × 10−7 RIU.

Рассеяние звуковых волн цилиндром с радиально-неоднородным упругим покрытием в плоском волноводе

В статье рассматривается задача рассеяния звуковых волн абсолютно жестким цилиндром с радиально-неоднородным изотропным упругим покрытием в плоском волноводе. Полагается, что волновод заполнен однородной идеальной жидкостью, одна его граница является абсолютно жесткой, а другая - акустически мягкой, законы неоднородности материала покрытия цилиндра описываются дифференцируемыми функциями, гармоническая звуковая волна возбуждается заданным распределением источников на сечении волновода. В случае установившихся колебаний распространение малых возмущений в идеальной жидкости описывается уравнением Гельмгольца. Колебания неоднородного изотропного упругого цилиндрического слоя описываются общими уравнениями движения сплошной среды. Для нахождения поля смещений в неоднородном покрытии построена краевая задача для системы обыкновенных дифференциальных уравнений второго порядка. Первичное поле возмущений представлено совокупностью собственных волн волновода. Давление рассеянного цилиндрическим телом поля ищется в виде потенциала простого слоя. Построена функция Грина для уравнения Гельмгольца, удовлетворяющая заданным граничным условиям на стенках волновода и условиям излучения на бесконечности. Функция плотности распределения источников ищется в виде разложения в ряд Фурье. Для нахождения коэффициентов этого разложения получена бесконечная линейная система уравнений. Проведено усечение бесконечной системы и ее решение найдено методом обратной матрицы. Получены аналитические выражения для рассеянного акустического поля в разных областях волновода.

Electromagnetic Compatibility Parameters of an Airborne Slot Antenna System

For the purpose of building extended surfaces in the long and short wave sections of the wavelength spectrum, it is deemed relevant to know the parameters of electromagnetic compatibility of airborne slot radiator antenna systems operating in the multi-wave receiving mode. One of the efficient research methods is to solve the problem of electromagnetic wave propagation in an infinitely extended slot radiator. The research purpose is to study the electromagnetic compatibility parameters of airborne slot radiator antenna systems operating in the multi-wave receiving mode. The main research methods were the statistical processing of the experimental data of tests in situ and mathematical description of the electromagnetic radar setting, as well as its computer simulation. The main result of the study can be formulated as the development of analytical and software methods for calculating the internal, external and equivalent conductivities of longitudinal and transverse slots on a wide wall of a rectangular waveguide of an antenna system at main frequency harmonics and at frequencies exceeding the main one, with account of slot width. We calculated the radiation characteristics of a slotted-waveguide antenna system at harmonics. The results of the study were used in the development of a universal technique for designing and developing radar systems capable of adequate functioning in the conditions of the electromagnetic setting under consideration. The results of the study will enable a more complete description of the electrodynamic pattern of wave propagation, making it possible to increase their generation and propagation.

Internal admittance elements of a rectangular waveguide longitudinal slot using the image method

ABSTRACTThe internal admittance matrix elements that are needed during the Method of Moments analysis of a longitudinal slot in a rectangular waveguide have been evaluated by considering the slot images in waveguide walls. The contribution from all the sources (real and virtual) has been evaluated by adopting the technique of Fast Matrix Generation (FMG). The contribution from all the image terms has finally been evaluated using a simple closed-form expression and a rapidly converging series. This leads to a faster, intuitive and more efficient analysis. The results calculated using this simple method are shown to be in excellent agreement with measured results and with other theoretical results. This method is useful in the efficient design of waveguide fed slot arrays.

Design of Broadband W-Band Waveguide Package and Application to Low Noise Amplifier Module

In this paper, the broadband millimeter-wave waveguide package, which can cover the entire W-band (75–110 GHz) is presented and applied to build a low noise amplifier module. For this purpose, a broadband waveguide-to-microstrip transition was designed using an extended E-plane probe in a low-loss and thin dielectric substrate. The end of the probe substrate was firmly fixed on to the waveguide wall in order to minimize the performance degradation caused by the probable bending of the substrate. In addition, we predicted and analyzed in-band resonances by the simulations that are caused by the empty spaces in the waveguide package to accommodate integrated circuits (ICs) and external bias circuits. These resonances are removed by designing an asymmetrical bias space structure with a radiation boundary at an external bias connection plane. The bond-wires, which are used to connect the ICs with the transition, can generate impedance mismatches and limit the bandwidth performance of the waveguide package. Their effect is carefully compensated for by designing the broadband two-section matching circuits in the transition substrate. Finally, the broadband waveguide package is designed using a commercial three-dimensional electromagnetic structure simulator and applied to build a W-band low noise amplifier module. The measurement of the back-to-back connected waveguide-to-microstrip transition including the empty spaces for the ICs and bias circuits showed the insertion loss less than 3.5 dB and return loss higher than 13.3 dB across the entire W-band without any in-band resonances. The measured insertion loss includes the losses of 8.7 mm-long microstrip line and 41.8 mm-long waveguide section. The designed waveguide package was utilized to build the low noise amplifier module that had a measured gain greater than 14.9 dB from 75 GHz to 105 GHz (>12.9 dB at the entire W-band) and noise figure less than 4.4 dB from 93.5 GHz to 94.5 GHz.

45 GHz Wideband Circularly Polarized Planar Antenna Array Using Inclined Slots in Modified Short-Circuited SIW

This paper presents a $Q$ -band planar circularly polarized (CP) antenna array with a wide bandwidth, in terms of both impedance matching and axial ratio (AR). A centered 45°-inclined slot in the broad wall of a substrate-integrated waveguide (SIW) with a modified short-circuited termination is first introduced to realize a wideband 45° linearly polarized radiation, incorporated with a pair of inductive vias for impedance matching. Then, orthogonally integrating two proposed slots with an SIW 90° directional coupler, a wideband CP element is designed and its beam exhibits a good AR over a relatively wide angular region in one direction. Following this, a two-layer SIW is employed to design a CP antenna array. Four CP elements are arranged in a rotational manner in the top layer, and they are sequentially fed by a four-way power divider in the bottom layer with an incremental phase delay of 90° to achieve a conical CP beam and higher gain. The performances of the power divider and cross-layer coupling slot are examined in the wide operating band. The proposed CP array antenna is prototyped at $Q$ -band, and measured results show that the antenna has $\vert S_{11}\vert dB, AR $\times \,\, 30$ mm $\times \,\, 1$ mm.

A new technique and results of measurements of dielectric and magnetic properties of loss dielectrics for vacuum tubes

A technique for measuring dielectric and magnetic properties of materials by the waveguide method is proposed in which the error, associated with the presence of gaps between the sample and the waveguide wall is eliminated by comparison with the results of numerical analysis of a 3D model the dielectric characteristics of which are optimized in order to achieve the best agreement between the calculated and experimental data.

Beam Steerable Array Antenna Based on Rectangular Waveguide for High-Power Microwave Applications

A high power, high gain, and beam-steerable array antenna for high-power microwave applications is presented in this paper, which is fed by rectangular waveguides. A C-shaped slot on the narrow wall of the rectangular waveguide is applied to couple energy from the waveguide to the helical unit, which is used to radiate circularly polarized microwave. 2-D beam scanning is achieved through fewer control units. Simulation results indicate that a 2-m-long linear array achieves a gain of 26.3 dB, an aperture efficiency of 90.43%, and a power-handling capacity of 96.5 MW. A prototype of 20 × 15 array shows the beam scanning range is about ±35° in both typical vertical planes, while the gain decreases by less than 2.0 dB.

INTERNAL PARTIAL CONDUCTANCES OF A LONGITUDINAL SLOT WITH PARTIAL DIELECTRIC FILLING

Among the ways of enhancement of functional capabilities of antenna-feeder devices on the basis of slot coupling elements one is partial filling of the slot cavity by a dielectric medium. Solution of the scattering problem with the use of the continuity condition for the tangential component of the magnetic field on the slot surfaces is reduced to a set of linear algebraic equations of the Galerkin method whose matrix elements represent partial conductions of the slot. In the present paper, analytical expressions have first been derived for partial internal conductions of a longitudinal slot with a layered dielectric filling cut in the wider wall of a rectangular waveguide. The LEq0 eigenmodes of a rectangular waveguide partially filled with a dielectric material are used in the capacity of the basis functions in the Galerkin procedure. Frequency dependences of the intrinsic and transfer conductances of the slot are analyzed. It is shown that by changing the dielectric layer parameters in the slot it is possible to control the active and reactive components of the intrinsic conductivity of the slot which effect can be used for controlling the characteristics of slotted waveguide antenna arrays.

Comparative studies of various types of transmission lines in the frequency range 70 GHz 1 THz for ITER ECE diagnostic

In ITER, an Electron Cyclotron Emission (ECE) diagnostic is planned to measure the electron temperature by measuring the cyclotron radiation in the frequency range of 70-1000 GHz. The cyclotron radiation is usually of low power and needs to be transported with low attenuation over a long distance of ~ 43 m, through a suitable transmission system. Pertaining to long distance, the transmission system will consist of straight waveguide sections, miter bends and waveguide joints. Low power, low loss transmission in a broadband frequency range over long distance makes the design of the transmission system challenging. To arrive at a suitable transmission system, attenuation measurements of three types of transmission lines (TLs) have been performed i.e. circular smooth walled, corrugated and dielectric coated waveguide. A polarizing Michelson interferometer based on Martin-Puplett design has been used to measure the spectrum from waveguide set ups and liquid nitrogen has been used as the black body radiation source. The measured spectrum shows atmospheric water vapour absorption lines in all types of TLs. The preliminary measurement shows that the attenuation of smooth walled waveguide is found to be comparable to corrugated waveguide up to ~ 600GHz and better than corrugated waveguide above 600 GHz for the chosen set of experimental conditions. Further, to avoid water absorption lines, a smooth walled TL is evacuated up to rough vacuum (~10-2mbar) and it was observed that the attenuation is decreased and overall transmission is improved.

Development of Waveguide Loads for High-Power SHF Devices Based on Composite Materials

Researches in the field of development of new waveguide super-high-frequency (SHF) loads based on composite materials for SHF devices and accelerator facilities have been carried out at the Budker Institute of Nuclear Physics in partnership with the Bolid company (Novosibirsk). Absorbing properties of the composite material, which cover the walls of the rectangular waveguide, are measured. Based on the data, the waveguide load prototype has been developed and tested with klystron and peak SHF power up to 25 MW. In this paper, the device is described and the results of measurements with low SHF power and benchmark tests of the load prototype and S-band klystron are presented.

A Sub-THz Rectangular Waveguide Phase Shifter Using Piezoelectric-Based Tunable Artificial Magnetic Conductor

An analog phase shifter operating at 240 GHz and implemented within a rectangular waveguide is presented in this paper. The phase shifter relies on mechanically actuating a tunable perfect magnetic conductor (PMC) inside an upright rectangular waveguide supporting a modified TE10 mode. The PMC boundary condition is realized using a metallic strip suspended slightly above the short wall of the rectangular waveguide. It is shown analytically and numerically that vertically actuating the metallic strip changes the dispersion relation of the modified TE10 mode leading to a controllable phase shift. The proposed structure is designed using full-wave simulations and optimized for minimal losses. It is then fabricated using standard silicon microfabrication techniques including photolithography, deep reactive ion etching, and metal sputtering. The actuation is done through an external piezoelectric actuator that is assembled with the microfabricated structure to form a single unit. The phase shifter shows a measured phase shift of 380° with worst case insertion loss of 3 dB leading to an excellent figure of merit (FoM) of 127°/dB. To the best of our knowledge, this is the best reported FoM for all passive phase shifters operating beyond 60 GHz.