Realization of a Polarization Filter Based on the Association of Rectangular and Circular Waveguide Sections

An accurate design technique of dual-mode microwave dielectric or air-filled rectangular waveguide filters is described. Dual-mode coupling is realized by a section of rectangular waveguide with square-corner-cut. The unequal couplings between dual-mode pairs of the cavities is provided by a section of evanescent mode waveguide. Rigorous analyses are applied to characterize the microwave junctions and to obtain the design parameters for the filter. The design procedure used to determine the dimensions of the waveguide junctions with a minimum of computational effort is described. The design is demonstrated by four-pole and six-pole dual-mode rectangular waveguide elliptic function filters. Excellent agreement between computer simulation and experimental results with absolutely no tuning justifies the design.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The physical processes occurred in the waveguide-dielectric structure that has the form of a section of rectangular cut-off waveguide with dielectric insertion, which completely fills the cross section of the waveguide have been considered. The electromagnetic fields in the classic waveguide-dielectric resonator without devices for its excitation and a coupling element with two sections of the cut-off waveguide have been calculated. The expressions for the reflection and transmission coefficients of the structure under consideration are presented. The positions of poles and zeros of the reflection coefficient have been investigated with a fractional-rational approximation and they have been compared with the natural frequencies. The obtained results are useful for measuring the properties of dielectric materials with the aid of waveguide methods.

Axially symmetric transverse electric (TE) modes of a circular waveguide section are used to synthesize the vector TE Localized Wave (LW) field at the open end of the waveguide section. The necessary excitation coefficients of these modes are obtained by the method of matching, taking advantage of the modal power orthogonality relations. The necessary excitation of modes provided by a number of coaxial loop antennas inserted inside the waveguide section. The antennas currents are computed from the solution of the waveguide excitation inverse problem. The accuracy of the synthesized wave field (compared to the mathematical model) and the power efficiency of the generation technique are evaluated in order to practically realize a launcher for LWs in the microwave regime.

Rectangular waveguide section with two partial-height transversal inserts located side by side is examined. Such a section acts as a resonator providing two transmission zeros and one transmission resonance located between these zeros simultaneously. Thus, the number of transmission zeros is twice more than the number of waveguide sections. The broadband quarter-wavelength resonator filter using such sections provides two stopbands and one passband simultaneously. Their bandwidths and locations are controlled both by the section geometry and the distance between the sections. Two closely spaced sections providing two independent stopbands are proposed as a perspective block for a filter with complicated frequency response.

In this paper, a rectangular waveguide probe with a ridge-loaded straight slot (RLSS) is presented for a near-field scanning microwave microscope (NSMM). The RLSS is located laterally at the end wall of the cavity and is loaded on double ridges in a narrow straight slot to improve the spatial resolution compared with a straight slot. The probe consists of a rectangular cavity with an RLSS and a feed section of a WR-90 rectangular waveguide. When the proposed NSMM is located at distance of 0.1mm in front of a substrate without patches or strips, the simulated full width at half maximum (FWHM) of the probe improve by approximately 31.5 % compared with that of a straight slot without ridges. One dimensional scanning of the E-plane on a sample under test was conducted, and the reflection coefficient of the near-field scanning probe is presented.

This paper presents the design of a unique multimode extractor and converter of higher order modes of a circular waveguide. The multi-mode extractor couples first five circular waveguide propagation modes TE11, orthogonal TE11(o), TM01, TE21, and TE21(o) that includes the three tracking signals (i.e. sum signal, elevation signal, and azimuth signal) used in a high-frequency monopulse tracking system and two communication channels for transmitting and receiving signal at Ka band. This design is based on amplitude and phase characteristics of the higher-order modes TM01, TE21, and TE21(o) excited in circular waveguide. TE21 and TE21 (o) modes are extracted from circular waveguide to TE10 mode in rectangular waveguide by two longitudinal slots milled in the circular waveguide. TE11 mode is coupled using two coupling slots and H-plane power combiner. A turnstile junction is used to extract TM01 and TE11(o) mode. This multimode tracking system is designed both for linear or circular polarized ground earth station antennas to track orbiting satellites.

Context. The problem is to systematize and improve the models of a resonance ferrite isolator in the rectangular waveguide for the antenna-feeder devices, generating, receiving, measuring microwave equipment containing ferrite decoupling devices: ferrite isolators and circulators. Objective. The goal of the work is to verify the formula for the losses of the resonant ferrite isolator in the direct and reverse directions, as well as the isolator ratio. Method. The research method of the work is a critical analysis of literary sources, which was carried out, but did not bring the desired results, since it did not allow to verify the correctness of the derivation of the formula [17]. Therefore, a number of hypotheses were put forward, what the formula might mean. The difficulty lay in the presence in the formula of the product of trigonometric functions that can be attributed to frequency properties, which was taken as an initial hypothesis, which was not subsequently confirmed. The check included transformation of formulas using mathematical physics in terms of microwave electrodynamics, trigonometry and algebra. The beginning was the formula of the classics [16], similar to the formula of [18], accepted without proof. As it is known, for the main type of wave in a rectangular waveguide, the components of the magnetic field strength, obtained as a solution to the wave equation under the boundary conditions inherent in a rectangular waveguide. One component of the magnetic field strength is along the direction of wave propagation, and the second one is in the transverse direction in the section of the waveguide are proportional to the trigonometric functions cosine and sine with the same arguments. The equality of the two components of the strengths is traditionally uses to find the plane of circular polarization where to place the ferrite isolator, and so the authors use this proportionality to trigonometric functions in their derivation, namely the formulas of trigonometric functions of a double angle, the basic trigonometric identity sine squared plus cosine squared is equal to one for replacing the propagation constants with trigonometric functions, this allows to get rid of radicals in the formulas, these radicals in the formula are due to the phenomenon of dispersion in a rectangular waveguide. The rest of the manipulations with the formula are the reduction of similar terms. Results. There was obtained analytical expressions for the losses of the resonant ferrite isolator in the forward and reverse directions, as well as the isolator ratio by strict mathematical transformations. There was performed such transformations. The ratios of the longitudinal propagation constant to the transverse propagation constant are replaced by the ratios of the trigonometric functions sine and cosine, since they are continuous as opposed to tangents and cotangents. Such a transformation allows to avoid square roots in the formula for the losses of the ferrite isolator in the forward and reverse directions, which are associated with the presence of dispersion in the waveguide, as in the formula for wavelength in the waveguide. The conversion is based on microwave electrodynamics. The formulas are used for the distribution of fields in a rectangular waveguide for the main type of wave. Further transformations consist in taking the common factor out of brackets and other arithmetic transformations. Conclusions. Тhrer was obtained results partially coincide with the well-known [17], the derivation of the formula [17] was obtained for the first time, the studies carried out allowed us to reject the hypothesis that the product of cosines and sines in the loss formula of a ferrite isolator is a frequency characteristic, it appears as a result of arithmetic transformations. To take into account the frequency range, it is used that there is circular polarization at the middle frequency, there will also be circular polarization at the extreme frequency of the range, but the plane of circular polarization will shift in comparison with the position of the plane of circular polarization at the middle frequency. That is, a peculiar system of two equations is obtained with respect to two positions of the polarization plane relative to the wide side of the rectangular waveguide section. The scientific novelty consists in systematization and generalization of the formulas of the loss of the resonance ferrite isolator, the connection between the formulas from different literature sources, both foreign and domestic, is proved, which saves time for researchers of ferrite isolators for the verification of the formula. The practical significance. It may be useful for teaching purposes and in optimization of the ferrite isolator design.

&lt;div class="htmlview paragraph"&gt;In the Sabatier reactor, oxygen is recovered (as water) by hydrogenation of carbon dioxide. Half of the reacted hydrogen is contained within the product water, the other half forms methane (CH&lt;sub&gt;4&lt;/sub&gt;). To close the hydrogen loop, we are investigating methods for the efficient recovery of hydrogen from CH&lt;sub&gt;4&lt;/sub&gt;. This paper describes microwave plasma-based methods for the thermal decomposition (cracking) of methane to produce hydrogen, elemental carbon, and related carbonaceous substances. Two primary reactor configurations have been employed in this work: 1) a quartz tube vertically oriented within a section of rectangular waveguide, and 2) waveguide transmission through a quartz window into a cylindrical vacuum chamber based multimode cavity. Hydrogen recoveries of up to 98% have been obtained. Three primary mechanisms of methane decomposition have been identified: methane pyrolysis, methane oligomerization, and methane aromatization. In the multimode plasma chamber methane pyrolysis experiments, we have observed the formation of a highly dendritic form of elemental carbon which may be beneficial in the minimization of potential problems associated with carbon deposition. Alternatively, by optimization of the reactor to promote volatile oligomerization products, carbon formation is minimized.&lt;/div&gt;

The experimental investigation of a reflectometer for measuring return loss magnitude and phase at submillimeter wavelengths is presented. The reflectometer, which is designed as a proof-of-principle demonstration, is based on the sampled-transmission line architecture and its design and operation are described. The instrument is a relatively simple implementation of the six-port network analyzer introduced by Engen and consists of a section of rectangular waveguide and an ensemble of Schottky diode power detectors. Design considerations for the instrument are presented and measurements in the 270 GHz to 285 GHz range are discussed.

This paper investigates a novel waveguide component design with dual functionality of mode conversion and power splitting. Because of its complex internal geometry which conventional fabrication methods cannot realize, additive manufacturing was explored, specifically selective laser melting. The end-to-end process of design, simulation, fabrication, and measurement will be discussed in detail. The said waveguide component converts between 4 rectangular waveguide TE10 mode and 1 circular waveguide TM01 mode. The 1 to 4 splitter was done while achieving low power splitting losses and mode conversion losses with low return losses. This allows for waveguide connections to be made between circular waveguides and rectangular waveguides at X-Band, which can be used for radars or satellite communication applications. The novelty of this component design comes from impedance matching between 4 rectangular waveguides operating in the fundamental mode and 1 single highly over-moded circular waveguide by means of coaxial rod and matching fins. All these are done while keeping the overall size small, compact, and lightweight.

A Fabry-Perot–like interferometer with two microwaveguide adaptors as reflectors creates a passive dielectric medium with a negative group delay time due to polarization shift. In that case rectangular with circular waveguides are adapted. A rotational strain of the polarization vector by one of the adaptors is coupled with the excitation of a drastic negative group velocity. The adapted rectangular and circular waveguides have the same dispersion. The input rectangular waveguide mode is linearly polarized, whereas the basic mode of the adapted circular waveguide is circularly polarized. A 20 m long circular waveguide connects the input with the output adaptor. Experiments are reproduced in the frequency and in the time domain. A polarization turn of the two different handed reflected circular wave modes causes the observed negative group velocity.

In recent years, R&D for pulse compression and power distribution systems for the Next Linear Collider has led to the invention of many novel rf components, some of which must handle up to 600 MW of pulsed power at X‐band. These include passive waveguide components, active switch designs, and non‐reciprocal devices. Among the former is a class of multi‐moded, highly efficient rf components based on planar geometries with overmoded rectangular ports. Multi‐moding allows us, by means of input phasing, to direct power to different locations through the same waveguide. Planar symmetry allows the height to be increased to improve power handling capacity. Features that invite breakdown, such as coupling slots, irises and H‐plane septa, are avoided. This class includes hybrids, directional couplers, an eight‐port superhybrid/dual‐mode launcher, a mode‐selective extractor, mode‐preserving bends, a rectangular mode converter, and mode‐mixers. We are able to utilize such rectangular waveguide components in systems incorporating low‐loss, circular waveguide delay lines by means of specially designed tapers that efficiently transform multiple rectangular waveguide modes into their corresponding circular waveguide modes, specifically TE10 and TE20 into circular TE11 and TE01. These extremely compact tapers can replace well‐known mode converters such as the Marié type. Another component, a reflective TE01‐TE02 mode converter in circular waveguide, allows us to double the delay in reflective or resonant delay lines. Ideas for multi‐megawatt active components, such as switches, have also been pursued. Power‐handling capacity for these is increased by making them also highly overmoded. We present a design methodology for active rf magnetic components which are suitable for pulse compression systems of future X‐band linear colliders. We also present an active switch based on a PIN diode array. This component comprises an array of active elements arranged so that the electric fields are reduced and the power handling capability is increased. Novel designs allow these components to operate in the low‐loss circular waveguide TE01 mode. We describe the switching elements and circuits.

Oscillators in the microwave and millimeter-wave region were constructed wherein the resonators consisted of sections of rectangular dielectric waveguide. While adding thin blocks of dielectric to increase the mechanical length of the resonator, the power output and frequency were measured. Using this technique, the experimental value of the wavelength in the longitudinal direction, lambda/sub g/, was determined. These experimental data were then compared with calculations predicted by optical theory. Good agreement was found where the bulk wavelength was small compared with the cross-sectional dimensions of the dielectric. If the half-wavelength in the dielectric was comparable with the dielectric dimensions, the values of lambda/sub g/ were greater than the theoretical values. In the process of carrying out these experiments, a new type of oscillator is described which provides a power ontput comparable with diodes in metal-walled cavities. In addition, the new dielectric cavities are simple in construction and are compatible with dielectric waveguide, image line, or microstrip systems.

Intentional and controllable introduction of attenuation poles into the frequency responses of frequency-selective devices is in the great demand in the design of modern filters with complicated performance. Successful implementation of such an approach is possible using rectangular waveguide sections with metallic inserts. Here, the scattering characteristics of such sections with a pair of antipodal rectangular posts as waveguide units with rotational symmetry are studied. Comparative analysis with the characteristics of a section with a pair of unidirectional posts is performed. Spectral theory of open waveguide resonators is used in order to interpret the resonant phenomena. Within the frames of spectral theory the reflection resonances formed by such sections are the responses to the excitation of eigen oscillations of complex frequencies. It is shown that the spectral theory enables an order of magnitude more accurate (in comparison with the conventional modal analysis) evaluation for basic parameters of the resonance reflection, namely its frequency and the quality factor. The results obtained make preliminary synthesis of frequency selective devices based on such sections physically transparent and more accurate.

A new technique for the fabrication and integration of various waveguide components together with an integrated E-plane circuit to form a compact millimetre-wave subcomponent has been produced. These waveguide components were fabricated in two halves using SU-8 such that the circuits can be placed in the E-plane of the waveguide and accommodated in a specially designed metal block for measurement. This technique is sufficiently flexible and repeatable so as to permit complex 3-D waveguide components with low loss and excellent surface finish to be realised at low cost. Various rectangular waveguide sections with operating frequencies from 110 to 320 GHz have been fabricated and measured to evaluate this approach.