Rectangular Coaxial Line Research Articles

A 0.22–26.5-GHz Ultra-Wideband Directional Coupler Based on Copper Additive Manufacturing

This brief presents a compact (5mm×56mm) and ultra-wideband directional coupler fabricated by copper additive manufacturing. The coupler is directly synthesized through the even/odd mode extraction algorithm and realized from a pair of coupled air-filled rectangular coaxial lines with working frequency of 0.22-26.5GHz (usable to 10MHz). Periodically loaded polymer strips are embedded with the air-filled coaxial lines to support the inner conductor but this strips also deteriorate the directivity of the coupler. To alleviate this, a special arrangement of the polymer strips is proposed to decrease the unwanted coupling through the strips. As an example, a 27th-order coupler is designed and fabricated, the simulated and measured results have good agreement, showing 20dB of return loss (RL) at all ports, 17dB of coupling, <1.33dB insertion loss (IL), >120 times of frequency ratio and 10-20dB of directivity.

A Novel Self-Excited Atmospheric Pressure Microwave Plasma Jet Using Rectangular Coaxial Line

A novel self-excited atmospheric pressure microwave plasma jet (APMPJ) based on a coaxial line is successfully proposed for the medical treatment. The finite-element method (FEM) is applied to obtain the optimal size of the APMPJ. The plasma parameters, such as electron density and electron temperature, are calculated within 0.1 ms. When the plasma reaches a stable state, the electron density is closed to 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{22}$</tex-math> </inline-formula> m <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-3}$</tex-math> </inline-formula> , and the electron temperature is calculated to be 1.3 eV. According to the experimental results, the argon plasma jet can be self-excited at an incident power of 20 W, and the gas temperature of the plasma jet is closed to 318 K at an incident power of 15 W. In addition, the air plasma jet can be self-excited at an incident power of 110 W. Finally, the change in the density ratio of hydroxyl (OH) radical to other particles when water vapor is added to the APMPJ at different flow rates is analyzed. It is found that a small amount of water vapor can greatly increase the relative content of OH which is tested by spectrometer.

A Circuit-Based Wave Port Boundary Condition for the Nodal Discontinuous Galerkin Time-Domain Method

Waveguide-like transmission line (WLTL) structures, including rectangular waveguides, circular waveguides, and coaxial lines, have been widely used in microwave engineering. Determining how to efficiently model WLTLs has become vital for the design of various WLTL-based devices. In this paper, a circuit-based wave port boundary condition (CWPBC) is developed and applied in the discontinuous Galerkin time-domain (DGTD) method to accurately simulate these structures for the first time. In the CWPBC, modal voltages and currents of a WLTL are defined, and circuits based on modal voltages and currents are introduced. By co-simulating the modal circuit and the WLTL modeled using the DGTD method, various modal fields can be excited in the WLTL, and at the same time, the WLTL can be terminated without reflections. No extra costs or approximations are used in the proposed CWPBC, and there is no requirement of either the extension of the computational domains widely used in perfectly matched layer (PML) termination or the longitudinal field continuity used in the reported DGTD method. The proposed method can easily obtain the postprocessing parameters, including S-parameters and port power. Numerical results, including rectangular waveguide filters, circular waveguide horns, and coaxial-fed electromagnetic bandgaps (EBG), are given to validate the effectiveness of the proposed CWPBC.

Design of several isolated power combiners based on multimode transmission lines.

In this paper, a series of compact power combiners are designed based on multimode transmission lines. Based on the multimode transmission lines, several multiport mode networks are constructed to achieve two-way, three-way, and four-way high-isolation power combinations. In detail, a four-port mode network based on a rectangular coaxial dual-mode transmission line and a five-port mode network based on a rectangular three-ridge three-mode transmission line are designed to achieve compact high-isolation two-way power combination. A six-port mode network based on a circular-coaxial three-mode transmission line is designed to achieve compact high-isolation three-way power combination. A nine-port mode network based on a four-ridge dual-coaxial six-mode transmission line is designed to achieve compact high-isolation four-way power combination. Based on a compact multimode transmission line, two-way, three-way, and four-way power combinations can be realized with single stages, high isolation, compact cross section sizes, low insertion loss, and high power capacity. The corresponding methods can be used to design several excellent power combiners.

Design and Optimization of a Wideband Rectangular TEM Device for Cell Experiments

The influence of electromagnetic waves on living things has been of great concern in recent years. Traditionally, electromagnetic radiation device for cell experiments has a narrow frequency range and small radiation space. In this paper, a DC to 5.2-GHz rectangular transverse electromagnetic (TEM) device for cell experiments is proposed. The novelty of this research lies in the wide frequency range and sufficient radiation space under the condition of ensuring the transmission performance. The rectangular device is composed of a closed rectangular coaxial transmission line, tapered transition regions, inner plate structure, and dielectric supports. After simulation, optimization, and measurement, both the results of the simulated and measured studies indicate that reflection coefficient S11 is below −10 dB and transmission coefficient S21 is nearly 0 dB. It is demonstrated that the device has a good transmission performance from DC to 5.2 GHz, which meets the requirement for wideband cell radiation experiments. The proposed rectangular device is a good candidate for cell radiation experiment device.

Design of rectangular coaxial slot antenna for ultra‐high‐field magnetic resonance imaging

AbstractRectangular coaxial slot arrays (RCSAs) are antennas designed to ensure superior field penetration depth with a high signal‐to‐noise ratio (S/N) in the deeper imaging region of ultra‐high magnetic resonance imaging (MRI). The RCSA consists of a transmission line of λ/4 length surrounded by a dielectric material, and a ground plate that resembles a rectangular coaxial line. We extended this antenna to eight elements. The simulation indicates that a single RCSA has a distribution similar to that of the generally used dipole antenna for traveling RF waves. However, the of the RCSA in an array configuration was stronger in the deep brain region of the human brain model and its specific absorption rate was lower compared to the dipole and monopole antenna arrays. The proposed RSCA array can be adapted to acquire MR signals with high sensitivity in a deeper imaging region in an ultra‐high field MRI scanner.

W-Band Bandpass Filter Using Rectangular Microcoaxial Structure

This letter presents a second-order and a third-order W-band bandpass filter (BPF) based on rectangular microcoaxial structures. Rectangular microcoaxial line has the advantages of low dielectric and radiation loss, small size, and easy integration, which is conducive to the design of passive devices. The resonant unit based on rectangular microcoaxial structure consists of a metal cavity, a rectangular metal block suspended inside, and a grounded cylinder. It is used to design two Chebyshev filters. In order to facilitate the interconnection with other devices, ports of the filter are added with rectangular coaxial line to coplanar waveguide (CPW) transitions. The center frequencies of two filters are 93.3 and 94.3 GHz, respectively. Finally, the two filters are fabricated and measured to verify the design method. The minimum insertion loss in passband is 1.3 and 1.5 dB. Good agreements between the simulated and measured results are achieved.

Power dividing systems based on a rectangular coaxial line

L- and S-band phased array antennas are widely used in modern radiolocation systems. Existing power dividers for L- and S-band phased array antennas have several disadvantages. Waveguide based systems are sophisticated and have a large mass. Optical and conventional coaxial line based systems have a large size. Microstrip based systems are compact and have a low mass, but the maximum input power level is quite low. In this paper, the design of microwave devices based on a multilayer rectangular dielectric filled coaxial line is presented and the recommendations on its use in design of multichannel power dividers are given. The paper demonstrates that this type of power divider design results in lower mass, is compact and has high maximum input power level. Thus, multichannel power dividers based on a multilayer rectangular dielectric filled coaxial line are the most suitable for use in modern L- and Sband radiolocation systems.

A 3-D Printed $E$ -Plane Waveguide Magic-T Using Air-Filled Coax-to-Waveguide Transitions

This article reports on a new class of broadband and fully 3-D printed $E$ -plane coax-to-waveguide transition and a monolithically 3-D printed waveguide magic-T based on the transition. The transition is constructed by a section of air-filled rectangular coaxial transmission line (TL) that is placed between two broadband coax-to-waveguide probe transitions. It is used to interconnect the magic-T’s sum port and the waveguide T-junction. The incorporation of the transition reorients all the waveguide arms of the magic-T into the $E$ -plane. Some $X$ -band prototypes of the proposed transition and the magic-T are designed and implemented. Polymer-based additive manufacturing and copper electroplating techniques are employed to monolithically fabricate each prototype. The transition and the magic-T exhibit broadband and low-loss characteristics from 8.2 to 12.4 GHz with the measured performance well matched with the simulations. In addition, the power handling capability (PHC), including the peak PHC (PPHC) and the average PHC (APHC), of the magic-T is evaluated by simulations, showing that the proposed magic-T could handle 100 W of APHC.

Calculating Characteristic Impedance Without Using Symmetricity of Rectangular Coaxial Line

Calculating Characteristic Impedance Without Using Symmetricity of Rectangular Coaxial Line

Full Ka Band Waveguide-to-Microstrip Inline Transition Design

In this paper, a compact and broadband inline waveguide-to-microstrip transition is proposed to cover the full Ka band. The transition can be segmented from the electric point of view into three building blocks, comprising a microstrip line to rectangular coaxial line, a wedged rectangular coaxial line to ridged waveguide, and a final tapered ridged waveguide impedance transformer to standard waveguide. Both good electrical performance and simple modular assembly without any soldering have been simultaneously obtained. The validation of the design concept has been conducted by numerical simulations and experimental measurements. The experimental results of a fabricated back-to-back transition prototype coincide with the simulated results. It shows that the proposed transition achieves good return loss of lower than 15.5 dB and low insertion loss with a fluctuation between 0.23 to 0.60 dB across the entire Ka band. Details of design considerations and operation mechanism as well as simulation and measurement results are presented.

On‐line passive intermodulation test method for conductive coatings

An on-line passive intermodulation test method for conductive coating is presented. A split-type rectangular coaxial line is working as test fixture. As the standing wave of this test fixture can stay small in the replacement of coating samples, passive intermodulation test can always continue. By using this test method, several coatings are rapidly distinguished from their different passive intermodulation performance. A fast passive intermodulation test method for coatings is demonstrated.

Mode Composite Waveguide

In this paper, mode composite waveguide (MCW) is proposed, which consists of inner and outer wave-guiding duo structures. The outer structure acts as a rectangular coaxial line suitable for lower frequency operation for its compact size, while the inner structure works as a rectangular waveguide suitable for higher frequency operation thanks to its simple structure and low loss. The MCW can propagate signals in the inner waveguide with TE10 mode and/or the outer waveguide with TEM mode depending on frequency to achieve optimal performance for both low- and high-frequency operations. In this paper, the fundamental waveguide parameters and higher order modes of the duo waveguides are examined. The proposed MCW prototypes are fabricated on a triple-layer PCB structure using the emerging substrate integration techniques. The MCW is fabricated and measured through the proposed microstrip line to the inner and outer waveguide transitions, and an MCW simultaneous feeding circuit is also presented. For this simultaneous feeding circuit, the good matching is achieved from 7.5 to 10.5 GHz for the low-frequency operation and from 25 to 39 GHz for the high-frequency operation, respectively.

Single-Layer Corporate-Feed Slot Array in the 60-GHz Band Using Hollow Rectangular Coaxial Lines

A single-layer corporate-feed slot array antenna is presented. The single-layer structure is realized by adopting hollow rectangular coaxial lines for the corporate-feed circuit and placing the feeding circuit and the radiating elements in the same layer. Based on this, a 16 × 16-element slot array for the 60-GHz band is designed and fabricated by diffusion bonding of laminated thin copper plates. A 32.3 dBi gain and 72.2% antenna efficiency are confirmed at the design frequency of 61.5 GHz in the measurements. The 1-dB down gain bandwidth is 8.8%. The conductor loss of the antenna is estimated to be 0.85 dB at 61.5 GHz.

Wideband micromachined broadside coupled Schiffman phase shifter

A 15–45 GHz broadside coupled rectangular coaxial line based phase shifter is demonstrated. An analysis, the design, fabrication, measurements and a sensitivity study are conducted and discussed. Amplitude and phase imbalances of <0.25 dB and <2.5°, respectively, are measured. Input port reflection coefficients < −10 dB and an insertion loss below 0.6 dB are also obtained. A conducted sensitivity study shows the small dependence of the device performance on the process variations. The presented results may pave the way for multi-octave analogue phase shifters and beamformers throughout the millimetre-wave range.

Wideband Millimeter-Wave Surface Micromachined Tapered Slot Antenna

A millimeter-wave surface micromachined tapered slot antenna (TSA) fed by an air-filled rectangular coaxial line is proposed. Detailed parametric study is conducted to determine the effects of the TSA's key structural features on its VSWR and gain. Selected exponential taper with determined growth rate and corrugation length resulted in an antenna with VSWR <; 2.5, gain > 2.75 dBi, and stable patterns over a 43-140-GHz range. The TSA is fabricated, and good correlation between modeling and W-band measurements confirms its wideband performance.

A Hollow Rectangular Coaxial Line for Slot Array Applications Fabricated by Diffusion Bonding of Laminated Thin Metal Plates

A hollow rectangular coaxial line is designed for the 60-GHz band and fabricated by diffusion bonding of laminated thin metal plates. A low transmission loss of 0.036 dB/cm is confirmed at 60 GHz by measurement in a designed rectangular coaxial line. The suspended inner conductor is supported by a thin plate. A longitudinal slot excited by the metal support and its linear array are presented. The proposed structures are verified by comparing the measured results with the designed ones. The 1.5% bandwidth of the linear array for reflection below -14 dB is obtained by the measurement.

Influence of the blanket shield modules geometry on the operation of the ITER ICRF antenna

Three-dimensional electromagnetic simulations of the ITER ICRF antenna have been recently performed with the commercial code CST Microwave Studio® (MWS) [1]. A detailed model imported from the CATIA® file has been considered: it includes the 24 straps array (CY3.1 geometry [2]) and the surrounding blanket shield modules. The transient solver in MWS has detected the presence of a very localized peak in the input impedance matrix at a frequency of approximately 51MHz in vacuum conditions. The presence of such a resonance in the ITER operating range of frequency is of concern and should be understood as previous analysis reported in [3] concluded that TEM and non-TEM modes are not expected in this frequency band as long as the antenna is grounded to the port at 1m back from the antenna front face. By using a simplified model of the geometry we demonstrate that the resonance is a consequence of the considered geometry of the blanket shield modules and in particular of the cavity at the back of the modules made of the module attachment and the port plug outer face. We show that the presence of such a cavity locally increases the coaxial line impedance and allows for a TEM mode in the band. This physical analysis is supported by a transmission line model where the system made of the antenna and its surrounding port is approximated by a rectangular coaxial line.

Wideband 18–40 GHz Surface Micromachined Branchline Quadrature Hybrid

This letter demonstrates two 18-40 GHz rectangular coaxial branchline quadrature hybrids designed using circuit and full-wave simulations. The chosen topologies are fabricated in a surface micromachining technology PolyStrata. Measured in-band performance of baseline wideband branchline hybrid shows |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> |<;-10dB, |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> | = -4.1 ± 1dB, and |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> | = -4.3 ± 0.7 dB. This hybrid is miniaturized by meandering the rectangular coaxial lines to obtain 57% reduction in surface area and in-band performance with |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10dB, |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> |= -4.2±1.2dB, and |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> | = -4.1 ± 0.7 dB.

Effect of Electromagnetic Pulses (EMP) on associative learning in mice and a preliminary study of mechanism

Purpose: To investigate the effects of electromagnetic pulses (EMP) on associative learning in mice and test a preliminary mechanism for these effects.Materials and methods: A tapered parallel plate gigahertz transverse electromagnetic (GTEM) cell with a flared rectangular coaxial transmission line was used to expose male BALB/c mice to EMP (peak-intensity 400 kV/m, rise-time 10 ns, pulse-width 350 ns, 0.5 Hz and total 200 pulses). Concurrent sham-exposed mice were used as a control. Associative learning, oxidative stress in the brain, serum chemistry and the protective action of tocopherol monoglucoside (TMG) in mice were measured, respectively.Results: (1) Twelve hour and 1 day post EMP exposure associative learning was reduced significantly compared with sham control (p < 0.05) but recovered at 2 d post EMP exposure. (2) Compared with the sham control, lipid peroxidation of brain tissue and chemiluminescence (CL) intensity increased significantly (p < 0.05), while the activity of the antioxidant enzymes Superoxide Dismutase [SOD], Glutathione [GSH], Glutathione Peroxidase [GSH-Px], Catalase [CAT]) decreased significantly (p < 0.05) at 3 h, 6 h, 12 h and 1 d post EMP exposure. All these parameters recovered at 2 d post EMP exposure. (3) No significant differences between the sham control group and EMP exposed group were observed in serum cholesterol and triglycerides. (4) Pretreatment of mice with TMG showed protective effects to EMP exposure.Conclusions: EMP exposure significantly decreased associative learning in mice and TMG acted as an effective protective agent from EMP exposure. This mechanism could involve an increase of oxidative stress in brain by EMP exposure.