Section Of Circular Waveguide Research Articles

Rectangular Waveguide Radial Combiners With Coaxial or Circular Intermediate Waveguide Sections Based on Stub Matching

Rectangular Waveguide Radial Combiners With Coaxial or Circular Intermediate Waveguide Sections Based on Stub Matching

Detection of defects in polyethylene pipes using open microwave coaxial line resonator sensor

A new method using a microwave coaxial line resonator sensor for the non-destructive evaluation of defects in polyethylene pipes is presented. The sensor consists of a coaxial line section and an extended section of circular waveguide. One end is short-circuited and the other end is open to free space. The sensor aperture is designed to conform to the curvature of the pipe outer surface, so that the common problem of the standoff distance effect by open-ended waveguide scanning is well circumvented. The presence of defects causes local permittivity and volume changes, leading to variations of the resonance frequency and quality factor due to material perturbation. The detection principle is confirmed by electromagnetic simulation. From the experiments, it is shown that the proposed sensor can perform both detection and classification of flat-bottom holes. The minimum diameter of the hole that can be detected is 1 mm, which is lower than that of a hole required in the standard practice. This method can also effectively detect axial defects and determine the lengths. In addition, an open-ended waveguide is used to detect axial holes, and the results were compared with those of coaxial line resonator. The sensor system presented here has the advantages of low cost, convenience for on-site detection and quantitative analysis.

ЗБУДЖЕННЯ ХВИЛІ TЕ01 У КРУГЛОМУ ХВИЛЕВОДІ ЗА ДОПОМОГОЮ ВИЩИХ ТИПІВ КОЛИВАНЬ ВІДКРИТОГО РЕЗОНАТОРА

Subject and Purpose. Peculiarities of the TE01 wave excitation in a circular waveguide located in the center of the flat mirror of a hemispherical open resonator (OR) are studied using the OR oscillation type TEM30q and the OR degenerate oscillation type TEM in the extremely high frequency (EHF) range. Methods and Methodology. The efficiency of the circular-waveguide TE01 wave excitation using the TEM30q and TEM11q types of OR oscillations is evaluated through the factor of antenna surface utilization. Amplitude distributions of the OR oscillation fields were measured by the trial body method. Results. It has been established that the efficiency, h, of the TE01 wave excitation in the circular waveguide is not high when it is by use of the OR oscillation ТЕМ30q. Things are different when the TE01 wave is excited with the inner ring of the TEM11q degenerate oscillation field whereby the h value shoots up to 95.5%, the circular waveguide section radius being a = 0.993w0, where w0 is the radius of the field spot of the main oscillation type TEM00q on the OR flat mirror. The experimental studies have confirmed that the TE01 wave excitation in the waveguide has high efficiency. The attachment of the circular oversized waveguide section worsens the OR loss by no more than 0.9 dB. The presence of the circular waveguide makes the TEM3012 oscillation type transform into the TEM1112 degenerate oscillation. Conclusions. The considered OR can be used as a storage resonator in the construction of electromagnetic pulse compressors in the EHF range, since the resonant system loss increases insignificantly, and the circular waveguide itself is oversized. It is easy to implement an interference switch in such a waveguide.

Direct Metal Laser Sintering Conformal Waveguide Array Antenna for Millimeter-Wave 5G Communications

An omnidirectional conformal array antenna has been implemented in air-filled waveguide technology for the 37–40 GHz band. The input port of the antenna is a standard WR28 rectangular waveguide. The TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode excited in the rectangular waveguide is used to generate the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode inside a circular waveguide by means of a TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> –TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode converter. The circular waveguide section is progressively widened, forming a radial waveguide structure, where the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode propagates radially through several radiating apertures. Due to the rotational symmetry of the structure, an omnidirectional radiating performance with low ripple can be achieved. This structure has been three-dimentional (3-D) manufactured using the direct metal laser sintering technology. A good agreement between simulations and measurements has been found. A reflection coefficient of below −15 dB, a low-ripple omnidirectional performance in a conical cut plane, a low cross-polar radiation, and a total efficiency higher than 83% are obtained. This conformal antenna design is proposed for fifth generation (5G) New Radio indoor applications.

Waveguide components for space applications manufactured by additive manufacturing technology

This study investigates the use of novel manufacturing technologies for space antenna feed chain systems. A comparison between conventional and advanced manufacturing technologies concerning the radio-frequency (RF) performance was made, in order to derive design rules for the novel manufacturing technology. Waveguide runs as well as feed chain components were redesigned by using these design rules. Therefore, mainly elliptical and circular waveguide sections were used. Different components were combined to save mass and power losses. Additive layer manufacturing (ALM) was chosen to build feed chain components in order to investigate the advantages of ALM compared to conventional technologies. This study concludes with an outlook on future opportunities of advanced manufacturing technologies for RF space applications as well as ongoing development activities.

Size-Limited Q-Band Circular Switched Parasitic Array Antenna With Small Elevation Beamwidth

A novel circular switched parasitic array (CSPA) antenna operating in the Q-band and capable of electronically switching its main beam over a large field of view of 360° in the horizontal plane is presented. The core component facilitating the beam switching consists of a circular parallel plate waveguide (PPW) section containing a printed circuit board with a central parallel plate mode (PPM) launcher surrounded by 12 electronically switchable PPM reflectors with increased bandwidth. The circular PPW section is flared into a radial waveguide whose diameter is reduced by shaping a foam filling material, originally incorporated for mechanical stability reasons, into a circumferential elliptical lens. By doing so, a small elevation half-power beamwidth is achieved with a size-limited geometry. A tube-like radome protects the circumferential aperture and further increases mechanical stability. Details on antenna design, manufacturing, and measurement results are given, successfully demonstrating the functionality of the concept. The antenna represents a step toward a cost-effective solution for future small-cell mobile networks millimeter-wave wireless backhauls.

Circular TE11-based waveguide polarizer for efficient coupling to electron Bernstein wave

A circular waveguide polarizer for 2.45 GHz microwaves has been designed and produced for electron Bernstein (EB) wave heating and current drive experiments on the low aspect ratio Torus experiment (LATE) device. In the experiments the microwaves are injected obliquely to the toroidal field to drive current carrying fast electrons. In the LATE case of the oblique injection of long free space wavelength waves onto a small plasma the coupling to the EB waves from the injected electromagnetic waves is improved when the injected waves have appropriate elliptical polarizations depending on the injection angle and the density gradient at the upper hybrid resonance layer (Igami et al 2006 Plasma Phys. Control. Fusion 48 573). Any elliptically polarized mode can be generated from a circular TE11 mode by the combination of a half wave section and a quarter wave section of circular waveguide. The transformation of polarization arises from the difference in axial wave numbers between an orthogonal pair of modified circular TE11 modes, which is realized by the insertion of a Teflon plate in a circular waveguide made of aluminum. Such a polarized wave is launched from the open end of a circular waveguide toward the plasma. An elliptically polarized mode adjusted to a steep density gradient and injected obliquely to the toroidal field has been found to be effective to sustain a highly over-dense plasma.

Radar Cross Section Modeling and Measurements of Inlets and Cylinders With Skew Blades

Ray based methods give useful scattered field predictions from the skin of the aircraft illuminated by an incident plane wave. They can also be used to predict the returns from simple inlets and cavities but fail when complex terminations such as skewed blades are encountered. As a possible enhancement to the ray-tracing procedure, an auxiliary program based on the modal method was developed to predict the scattering of electrically large and complex jet inlets with engines. For the present development, it is assumed here that these structures can be approximated by a series of rectangular, circular, coaxial and sectoral waveguide sections. The field matching technique is used to give the generalized scattering matrices of the junctions between these waveguide sections. By combining the scattering matrices of the waveguide sections representing the inlet and engine, an overall S-matrix is obtained. Knowing the modes induced at the inlet aperture by the incident plane wave, the scattered fields from the inlet and engine can be readily predicted in all directions. Monostatic RCS measurements of a 0.706 m diameter test cylinder containing 30 skewed blades mounted on a center shaft with a conical hub have been performed at X-band. The dimensions of the structure, the number and orientation of the blades are consistent with those of existing jet engines. Fair to good agreement between predictions and measurements verify the developed software and analytical method used

Multifrequency waveguide orthomode transducer

This paper presents the design and development of a multifrequency probe-coupled orthomode transducer (OMT) using a circular waveguide as the primary waveguide and a rectangular waveguide as the secondary waveguide. Design is presented for a common OMT operating at 6.6, 10.65, 18, and 21 GHz using four cascaded circular waveguide sections with different cross-sectional dimensions. An innovative design technique is used to minimize the inter-port coupling and to maximize the power in the dominant mode to get the required radiation performance at all the frequency bands using a common radiating aperture. The simulated and measured parameters of the OMT and the horn fed by this OMT have been presented.

A microwave broadband technique to measure the complex resistivity of HTS thin films

We propose a new broadband swept frequency technique to measure the complex resistivity of high T/sub c/ superconducting thin films in the microwave range (from a few GHz up to 50 GHz). A coaxial cable connects the sample to a vector network analyzer which performs reflection measurements; the film and the coaxial end are separated by a short section of circular waveguide. The absence of direct electrical contact between the sample and the coaxial core simplifies realization and avoids contact instability with large temperature variations. We provide an electromagnetic analysis of the coaxial to cylindrical transition (CCT) and find a closed form relation between the measured quantities and the film resistivity. Finally, we present some experimental results obtained for an YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// thin film using the described method.

Characterization of chiral materials at Ku-band using a circular cylindrical waveguide

The permittivity and the chiral admittance of a chiral material are determined from the measurements of field rotations obtained for the left and right circularly polarized waves and the guide wavelength in a section of Ku band circular cylindrical waveguide with an internal chiral coating. The results obtained from the automatic network analyser measurements in the frequency range 14.5–17.5 GHz demonstrate the usefulness of the proposed technique and results are presented for some commercially available chiral materials like 3 hydroxy butyrite- co -3 hydroxy valerate (PHB-PHV) and cellulose butyrate. Limitations of the proposed technique are also discussed.

Design of compact waveguide twists

A new geometry for compact twist components composed of rectangular and circular waveguide sections is presented. The proposed twist geometry presents several advantages: 1) It can be designed for any rotation angle; 2) it is extremely short and, therefore, well suited for satellite communication applications; 3) its electrical behaviour is excellent for either narrow or broad frequency bands; and 4) a very accurate and efficient full-wave mode-matching method can be used to analyze these twists. A software package has been developed to design the proposed compact twist structure in a full-wave method.

Measurements of the impressed electric field inside a coaxial electron cyclotron resonance plasma source

The magnitude and spatial variation of the impressed electric-field patterns inside a compact electron cyclotron resonance ion/plasma source are experimentally measured for argon and nitrogen feed gases. This ECR plasma source consists of several components: a resonant coaxial coupling section, an evanescent circular waveguide section, coupling loop, and the ECR discharge load itself. The electric fields inside the coaxial and circular waveguide sections are measured as the operating pressure and input power and are varied from 0.2 to 2.0 mTorr and 100 to 170 W, respectively. The measured fields verify that a standing wave with a maximum of 20–40 kV/m exists inside the coaxial section of length l. For matched conditions the length of this section varies only slightly between 0.6 and 0.7λ as pressure, power, and gas type vary. However, the evanescent impedance-matching circular waveguide section of length d changes from 2.5 for argon to 3.2 cm for nitrogen, indicating that the gas type influences the plasma impedance. Field pattern measurements in the ECR section of the source demonstrate the presence of nonevanescent fields in the discharge region. Measured plasma loaded and unloaded quality factors varied from 220 to 1800, respectively, indicating that 87% of the net input power is coupled into the discharge load. Additional calculations of conductive wall losses show that about 6% of the input power is lost in the cavity walls, and the remaining 7% is lost in the coupling loop.

On the Electrical Design of Pill-Box Type High Power Microwave Window

In this paper, a detailed design procedure for designing a thin disc pill-box type microwave window, operating in narrow frequency range at S-band and at a power level of 5 MW, has been given. The design criteria and a generalised design flow chart have been presented and discussed in detail. A method has been suggested for quicker experimental optimisation of the length of the circular waveguide section, which results in substantial saving of time and material. This design methodology can easily be adopted for designing practical pill-box type high power microwave windows.

Field theoretical computer-aided design of rectangular and circular iris coupled rectangular or circular waveguide cavity filters

The rigorous CAD of a class of rectangular and circular waveguide cavity filters which are coupled by rectangular and/or circular irises is described. The design theory is based on the full-wave mode-matching method for three key building block elements (asymmetric rectangular double-step, asymmetric rectangular-to-circular and circular-to-circular waveguide junctions) associated with the generalized S-matrix technique for composite structures. The waveguide filters may be arbitrarily composed of the key building block elements and the rectangular or circular waveguide sections between them. Finite iris thicknesses, higher-order mode interactions, and asymmetric structures are rigorously taken into account. The theory is verified by measurements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Excitation of a cylindrical retarding system of finite length by a modulated flux of charge particles

In the approximation of a given flux, the magnetic field arising with the motion of a modulated flux of charged particles along the axis of a spirally conducting section of circular waveguide is studied. Primary attention is allotted to the analysis of singularities caused by the finite size of the retarding structure.

WT4 Millimeter Waveguide System: Waveguide Design and Fabrication

The WT4 transmission line is a 60 mm diameter string of circular waveguide sections composed of 9 m long dielectric-lined and 4.4 m long helix waveguide sections, with dielectric-lined waveguide comprising approximately 99 percent of the transmission line. The dielectric-lined waveguide is manufactured from steel tubing whose geometric distortions are controlled on a power spectral density basis. The steel tubing is processed into waveguide by the application of copper and dielectric layers along its inner bore and by the attachment of flanges at its ends. The materials system and processes were chosen for extremely low ohmic losses, minimum geometric distortions, and high long-term reliability. The helix waveguide is formed from a closely spaced array of helically wound wires cast into an epoxy system, which is in turn enclosed in a steel jacket. The key design features of this helix waveguide are (i) the specially prepared iron-loaded epoxy which provides ohmic dissipation to spurious mode energy and (ii) the precision temperature control applied to the curing of the epoxy to assure minimum geometry distortion.

Millimetre-wave s.s.b. mixer with integrated local-oscillator injection

A description of a mixer mount with integrated image filter and l.o. injection filter is presented. The image filter is a high-pass filter using the cut-off properties of a circular waveguide section. The l.o. power is coupled selectively via a TE111-mode filter into the mixer waveguide. The i.f. matching transformer has been designed by a microstrip technique.

A Microwave Open-Ended Cavity as a Void Fraction Monitor for Organic Coolants

A novel application of an open-ended microwave cavity in the field of on-line nuclear instrumentation, specifically to the determination of the void fraction in organic coolants used for cooling nuclear reactors, is presented. The sensor consists of a section of circular waveguide inserted in series with the piping system transporting the coolant. For the selected frequency of operation, the sensor section forms a resonant cavity whose resonant frequency, being a measure of the void fraction, can be automatically and continuously monitored by an electronic system.

Microwave Measurements of the Loss in Low Loss Dielectrics

A technique has been developed which offers a significant improvement in the measurement of the loss in low loss materials having dielectric constants ≥4. The device consists of a cutoff section of circular waveguide concentrically loaded with a rod of the dielectric to be measured. The principal advantage of the technique is that by proper choice of sample and waveguide dimensions one can minimize the effect of resistive losses due to the metal walls. This is achieved by using the sample rod essentially as a section of dielectric waveguide in which the major fraction of the energy is confined to the rod. Both the reduction in wall losses and the simplicity of the design make the use of the waveguides fabricated from lower conductivity, high melting point metals much more attractive for measurement of low loss ceramic dielectrics at high temperatures. Results are reported for single crystal sapphire.