Coaxial Feed Research Articles

Enhancement of polarization purity in square dielectric resonator antenna using coaxial feed with metal strip loading for point-to-point communication applications

In this paper, a simple technique to enhance the polarization purity in a square dielectric resonator antenna (SDRA) using metal strip loading on the probe feed is presented for point-to-point communication applications. Coaxial feed placed at the commonly used offset location adjacent to the DRA has been studied in this regard. Cross polarized (XP) fields scattered from the feed into the air are found to be one of the reasons behind the deterioration of polarization purity in SDRA. When a thin metal strip is loaded on the probe feed using liquid solder to control these XP fields, the measured result shows an XP isolation of 47 dB at the boresight, 42 dB and 29 dB at the angular region of ±30°in the E-plane and H-plane, respectively. The proposed technique helps to overcome many unavoidable fabrication errors associated with complex machining and drilling processes involved in contemporary DRA designs for XP suppression. The proposed SDRA design offering good XP isolation performance and simple fabrication technique is highly suitable for low cost and high precision applications.

Optimal design of structure parameters of coaxial powder feeding nozzle for laser cladding

Aiming at the problems of large powder gathering diameter, low powder utilization rate, easy clogging of the nozzle, poor cooling water system effect and unstable powder feeding effect existing in the existing nozzles, an improved laser cladding coaxial powder feeding nozzle with external shielding gas structure is optimally designed. The response surface method and the BP neural network optimized by genetic algorithm are used to optimize the nozzle structure parameter combination. After the nozzle structure parameter combination is determined, the external shielding gas structure parameter range is determined according to the nozzle structure parameter combination. The unsupported laser cladding coaxial powder feeding nozzle is made of photosensitive resin material, and the powder feeding effect is verified. The optimized nozzle is measured for the powder converging point, powder converging diameter and powder utilization rate, which verifies the validity of the simulation results.

Effects of Nano-WC on Microstructure and Wear Resistance of Laser Cladding Ni-based Coating on 42CrMoA Alloy Steel

In the paper, Ni45 coating was manufactured by laser cladding on 42CrMoA alloy steel using the 5 kW CO2 laser, four-axis CNC machines and the coaxial powder feeding system. It was investigated that the effects of nano-WC on microstructure and wear resistance of the Ni-based coating. The macromorphology and microstructures were analyzed by SEM, XRD and microhardness tester. The wear tests were conducted on the Friction and Wear tester. The microstructure was first refined and then coarsened as the increase of nano-WC addition. When the nano-WC addition is 3.0 wt.%, the coating showed the finest microstructure. The clad layers including γ-Ni, N3B, M23C6 and WC, W2C. Meanwhlie, the wear rates of coating were gradually decreased.

Design and Analysis of Coax-Fed U-Slot Antenna for Wireless Applications

In this paper a multi frequency U-slot patch antenna for wireless applications is presented. The proposed antenna operates at four frequencies of 1.4GHz, 5.3GHz, 6GHz and 6.9GHz with return loss of -19dB, -22.50dB, -21.05dB, -19.37dB respectively. The antenna is designed with Rogers R04232 substrate with dielectric constant of 3.2 and dielectric loss 0.043 with dimensions of 47 × 54 × 1.5 mm3. Coaxial feed technique is used as a feed to the antenna which is having characteristic impedance 50 ohm. The simulation studies were carried out using Ansys HFSS 15.0 Software.

A Multiband Antenna Stacked with Novel Metamaterial SCSRR and CSSRR for WiMAX/WLAN Applications.

This paper presents an innovative method for the design of a triple band meta-mode antenna. This unique design of antenna finds application in a particular frequency band of WLAN and WiMAX. This antenna comprises of a square complimentary split ring resonator (SCSRR), a coaxial feed, and two symmetrical comb shaped split ring resonators (CSSRR). The metamaterial unit cell SCSRR independently gains control in the band range 3.15–3.25 GHz (WiMAX), whereas two symmetrical CSSRR unit cell controls the band in the ranges 3.91–4.01 GHz and 5.79–5.94 GHz (WLAN). This design methodology and the study of the suggested unit cells structure are reviewed in classical waveguide medium theory. The antenna has a miniaturized size of only 0.213 × 0.192 × 0.0271 (20 × 18 × 2.54 mm3, where is the free space wavelength at 3.2 GHz). The detailed dimension analysis of the proposed antenna and its radiation efficiency are also presented in this paper. All the necessary simulations are carried out in High Frequency Structure Simulator (HFSS) 13.0 tool.

Low-Profile Millimeter-Wave Broadband Metasurface Antenna With Four Resonances

A millimeter-wave (mmWave) broadband metasurface antenna with low profile is proposed. The radiator composed of four groups of coplanar patches with different dimensions has four adjacent broadside characteristic modes. Coaxial probe feeding is selected carefully to excite the four modes to broaden impedance bandwidth. Dual slots are etched on the patch fed by the coaxial probe to reduce H-plane cross-polarization levels. Characteristic mode analysis (CMA) and input impedance analysis are performed to characterize its resonance behaviors. The proposed antenna with dimension of 1.03 × 1.03 × 0.023 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is wavelength at 28 GHz in free space) realizes 16% (26.1 GHz-30.7 GHz) impedance bandwidth for |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | ≤ -10 dB. Realized peak gain is up to 10.1 dBi and 3 dB gain bandwidth is 22% (24.4 GHz-30.5 GHz). H-plane cross-polarization levels are less than -16 dB.

Effect of wire feeder force control on laser metal deposition process using coaxial laser head

Laser based Direct Energy Deposition (DED), also called Laser Metal Deposition (LMD), is a process that is widely used for cladding and repair applications and increasingly for additive manufacturing processes [Chen Hong, Dongdong Gu, Donghua Dai, Andres Gasser, Andreas Weisheit, Ingomar Kelbassa, Minlin Zhong, and Reinhart Poprawe, Opt. Laser Technol. 54, 98–109 (2013)]. Its controlled energy input and its ability to control the dilution allow the use of less material and the production of thin and precise layers increasing productivity and reducing costs [Erwin Werner Teichmann, “Analysis of welding process variants aiming cladding with Inconel 625 of API X46 steel pipes,” Ph.D. thesis in Mechanical Engineering, Post-Graduation Program in Mechanical Engineering, Federal University of Santa Catarina—UFSC, Florianópolis, 2016, p. 213, see https://repositorio.ufsc.br/handle/123456789/17223 (accessed 12 May 2020); Thomas Schopphoven, Andres Gasser, and Gerhard Backes, “EHLA: Extreme high-speed laser material deposition,” Laser Tech. J. 14, 26–29 (2017)]. Associated with those characteristics is the ability to operate using both powder and wire additives. The last one presents a series of advantages, as lower price per kilogram, lower porosity on the deposited material, and lower health risks for users. The use of a coaxial wire feeding laser head allows an omnidirectional operation for the laser head, presenting a great advantage when compared to lateral feeding systems. For soldering applications, some suppliers offer wire feeding systems that allow one to control the force applied by the wire on the substrate. This system measures the contact between the wire and the bottom of the melt pool, enabling a bridge metal transfer mode. The bridge transfer mode is essential, since the surface tension plays the main influence and, on the other hand, gravity plays only a minor role in the metal transfer. The results of using a force control system with different settings and a comparison between samples produced with and without this control are discussed. The material for both, samples and wire, is the stainless steel 316L. To assist the analysis, high-speed videos, process data acquisition, and macrographs are made.

Wheel-shaped miniature assembly of circularly polarized wideband microstrip antenna for 5G mmWave terminals

A simple arrangement of wheel-shaped copper microstrip antenna is presented for operation in the 24 GHz frequency band. In this structure, a coaxial feed probe was utilized to generate vertical polarization, and a wheel-shaped microstrip with four coupling arms was used to produce horizontal polarization. An antenna comprising of two copper sheets assembled between the air-substrate was manufactured and characterized experimentally. The measured and simulated values are in close compliance with each other. A stable in-band omnidirectional radiation patterns were achieved thereby ensuring a proper combination of the field vectors from the feed probe and the radiating arms. The antenna occupied an overall footprint of 8 mm to fruitfully realize −10 dB impedance bandwidth >3 GHz and radiation efficiency of ~100%. In the operating frequency band from 22.5 to 25.7 GHz, axial ratio <2.7 dB, gain <6 dBic and specific absorption rate (SAR) <0.06 W/kg was maintained. Furthermore, the integration of simple geometry and air-substrate significantly reduced the fabrication cost of the antenna system. Hence, the antenna is a promising candidate for 5G millimeter (mmWave) wireless communications.

Performance of the Microstrip Patch Antenna Model Design for 900 MHz and 2.4 GHz Working Frequency

The development of communication systems for several processes at this time makes the use of the frequency spectrum of cellular communication more and more. Antenna system which is an important component in a communication system that works on more than one frequency, such as a mobile phone that works with a working frequency of GSM frequency of 900 MHz and Bluetooth frequency of 2.4 GHz. The two antennas with different frequencies are expected to have optimal power in active conditions. This study shows the performance and design analysis of the prototype circular microstrip patch antenna using the coaxial probe feeding method at a frequency of 900 MHz, the dipole microstrip patch antenna using the coaxial probe feeding method at a frequency of 2.4 GHz, and the rectangular microstrip antenna operating at two frequencies, 900 MHz and 2, 4 GHz. The type of substrate used is PCB FR4 with a dielectric of 4.4 and h=1.6. The design of this microstrip antenna uses a mathematical approach. The results obtained from measurements at frequencies of 900 MHz and 2.4 GHz have a loss of less than -58.4897 dB and the two microstrip antennas do not interfere with each other, when the microstrip antenna is in a vertical position the transmit power is optimum and there is no interference when the microstrip antenna is in the vertical position. The loop patch and the dipole microstrip patch antenna are activated simultaneously.

The Analysis and Design of Circular Microstrip Moisture Sensor for Rice Grains

Two proposed design is analysed for determining the rice grains at different frequencies as well as it will be worked on triple frequency. The circular microstrip moisture sensor is designed with slotted in the ground plane at 2.2GHz and get the good return loss -25dB. The other circular microstrip antenna moisture is designed without slotted in the ground plane with the good return loss at different frequencies i.e., 3GHz, 4.7GHz, 4.8GHz and return loss is -27dB, -15.5dB, -15dB. The coaxial feed is used in this design because this is easy to minimize the spurious radiation as well as direct contact to patch. The proposed design will be fabricated on FR4 substrate with the thickness 1.676, εr = 4.3, and the loss tangent tanδ = 0.001.The proposed design parameters of the ground is 30mm. The oven drying technique will be used to determine the moisture content and measured the proposed design with the help of vector network analyser.

A circular microstrip patch antenna to operate in dual band for wireless communications

A dual band circular micro-strip patch antenna is designed and simulated to obtain electronic circuit miniaturization of an antenna in high speed wireless local area networks (IEEE 802.11a standard). The proposed antenna contains a substrate layer (FR-4 lossy) with a dielectric constant of 4.9 and there is a circular patch on the upper layer of the substrate. The coaxial probe feed is used to excite the desired antenna which reduces the spurious radiation and hence obtained good efficiency. Also the cavity model is used for larger bandwidth while maintaining the lower size of the antenna. An ‘E’ shaped slot is introduced in the radiating patch to obtain dual band resonance frequency with maximum current distribution on the surface. Finally the simulated results using Computer Simulation Technology (CST) microwave studio 2009 in this design are compared with manual computation results and are found to be suitable for WLAN applications.

Antenna Aperture Synthesis Using Mode-Converting Metasurfaces

Mode-converting metasurfaces are passive, lossless devices that can be designed to transform a set of incident modes to a desired set of transmitted modes. In this paper, mode-converting metasurfaces are utilized to synthesize arbitrary, azimuthally-invariant TM apertures. The methods presented in this work can be used to design antennas that can meet specific near-field and far-field criteria unlike most metasurfaces which solely manipulate the far field. The proposed antennas consist of a coaxially-excited, radial cavity topped by the mode-converting metasurface. The main role of the mode-converting metasurface is to establish the desired aperture by converting the modal distribution of the excitation to that of desired aperture. Its secondary role is to impedance match the coaxial feed to the radial cavity. Using modal network theory, an optimization-based design procedure is developed to synthesize the proposed metasurface antennas. The admittance profiles of the electric sheets that comprise the metasurface are optimized to establish the desired aperture profile. To illustrate the design procedure, a radial Gaussian beam antenna is synthesized at 10 GHz and its performance is verified using a full wave electromagnetic solver. The proposed antenna has a height and weight advantage over Gaussian beam horn antennas.

Surface-Mounted Ka-Band Vivaldi Antenna Array

The first electrically steerable dual-polarized Ka-band Vivaldi antenna array with connector-less, surface-mount interface is developed. The antenna interface includes integrated coaxial feed lines within the antenna element structure and contact pads on the PCB. The antenna array covers the frequency range from 26 to 40 GHz with a beam steering range of approximately ±60° in the elementary planes and ±50° in the diagonal plane, having less than 3 dB of scan loss. The 8×8 antenna array is manufactured with a feeding network for one polarization, and the operation of the interface and the electrical beam steering is demonstrated. Measurements are used to characterize the manufactured feed network, the gain of the antenna array and the steering range. The measured gain is between 19 and 22 dB, agreeing very well with the simulation and implying that the antenna interface operates properly. Furthermore, the antenna scan measurements agree with the simulation results.

Design of Circular Polarized Patch Antenna for NaviC Receiver Applications

In this paper, a circular polarized patch antenna at NaviC and S-band is presented for Indian Regional Navigational Satellite System (IRNSS) receiver applications. For this application proposed antenna is satisfying the criteria of circular polarisation with a bandwidth of 2477 MHz to 2508 MHz. The shape of proposed antenna exhibits good gain which is required for the good operation of communication systems for IRNSS. Antenna is operating at frequency of 2492.08 MHz (S-band) with a return loss better than -15 dB and has the stable radiation pattern. For designing of this antenna a conducting patch of 27.5 mm x 27.5 mm and a FR-4 material with thickness of 1.6 mm and dielectric constant of 4.3 is used as a substrate material. In addition to this, the antenna is fed with a coaxial feed technique and matched with 50 Ω input impedance of antenna. The parameters like radiation pattern, VSWR, E field, gain and axial ratio are analysed and achieved by CST studio Suite.

Millimeter-Wave End-Fire Magneto-Electric Dipole Antenna and Arrays With Asymmetrical Substrate Integrated Coaxial Line Feed

A wideband vertically-polarized end-fire magneto-electric (ME) dipole antenna fed by an asymmetrical substrate integrated coaxial line (ASICL) is proposed for millimeter-wave (mm-wave) applications. The proposed ME dipole antenna has an impedance bandwidth of 60% and produces an end-fire radiation with a stable gain between 5.8 and 6.9 dBi in simulation. To verify the design concept and its application in arrays, a $1 \times 8$ linear array with a fixed beam and a $1 \times 4$ linear array with multiple beams are designed, fabricated and measured. The fabricated fixed-beam array prototype exhibits an impedance bandwidth of 62%, a peak gain of 15.9 dBi and a radiation efficiency of 79%. The multi-beam array is fed by a $4 \times 4$ ASICL Butler matrix. Experimentally, excellent beam-scanning radiation patterns with reasonably low side lobes and low cross polarizations are demonstrated at 24, 30 and 36 GHz. And an overlapped operating bandwidth of 28.6% is achieved by the fabricated prototype.

Mechanism and dynamics of picosecond radial breakdown of a gas-filled coaxial line

High-voltage picosecond breakdown of an atmospheric-pressure air-filled coaxial line in the radial electric field of a propagating transverse electromagnetic wave has been studied both experimentally and theoretically. On the one hand, we demonstrate that gas preionization by runaway electrons (RAEs) plays a decisive role in the breakdown development process: the breakdown delay time drastically increases in the absence of RAEs. On the other hand, it is established that, for sufficiently short pulses, the radial gap switching process does not have enough time to develop even in a situation where the RAE flow is effectively generated. Fundamental limitations on the breakdown strength of gas coaxial feeders imposed by this effect are discussed.

Selection of modes for laser cladding of PR-08Kh17N8S6G powder

A brief analysis of powders used in the industry for surfacing on the work surfaces of critical parts is given in order to increase their wear resistance. The results of experimental studies on the choice of parameters of gas-powder cladding modes are presented. The cladding process was carried out by a laser robotic complex with a coaxial feed of powder to the surfacing zone. The substrate used steel grade 08H18N10T, which was applied to the melt of wear-resistant powder grade PR-08H17N8S6G. The use of ytterbium fiber laser allowed to reduce the heat supply to the surfaces, which significantly reduced the residual stresses in the workpiece. Variable parameters of the laser cladding process were the output power of laser radiation, processing speed, and powder mass flow rate. During visual inspection, the absence of pores and cracks were used as the estimated indicators of the cladding. The study of macro geometry single clad track was conducted on cross section of the clad. During measurements, the quality of a single clad track was determined by its geometric dimensions: clad height, clad width, contact angle between the tangent to the cladding surface and the substrate plane, as well the depth of the mixing layer of the surfaced and substrate materials. According to the results of experimental studies of the selected optimal mode, providing a cladding track with a clad height above 1 mm; clad width 2.5 mm; the depth of the mixing layer – 0.2 mm; contact angle between the tangent to the clad surface and the substrate more than 50º. This work was financially supported by the Ministry of Science and Higher Education of the Russian Federation. Agreement on the provision of subsidies No. 075-15-2019-1833 dated December 03, 2019. Unique identifier PNI RFMEFI60419Kh0245.

Effect of Y2O3 Addition on Microstructural Characteristics and Microhardness of Laser-Cladded Ti-6Al-4V Alloy Coating

In this study, the effect of Y2O3 addition on the quality, microstructure, and microhardness of multi-track laser-cladded Ti-6Al-4V coating using coaxial powder feeding was investigated. These parameters were characterised via dye penetration, x-ray diffractometry, scanning electron microscopy, energy dispersive spectrometry, electron probe microanalysis, microhardness measurements, and ball-on-disc tribometer. It is observed that Y2O3 addition improved the coating quality by completely eliminating the formation of pores in multi-tracked Ti-6Al-4V coatings. The microstructure of the coating without and with Y2O3 primarily consists of acicular martensite (α′-Ti). Furthermore, the continuity of original β-Ti grain boundary is broken by the introduction of Y2O3. In addition, the Y2O3 is adsorbed and pinned at the original β-Ti grain boundaries resulting in the refinement of the β-Ti grains. It is believed that the refinement in the original β-Ti grains occurs via inhibition of the movement of the grain solid–liquid interface through dragging action. This phenomenon hinders grain growth by acting as a heterogeneous nucleus rather than increasing nucleation rate because it exhibits high lattice misfit degree. Compared with the coating without the Y2O3, the microhardness and wear stability of the Y2O3-supplemented coating was improved because of grain boundary strengthening, fine-grained strengthening, addition of high hardness Y2O3, and elimination of pores.

Selection of rational modes of laser powder cladding

A brief overview of the surfacing used on the working surfaces of industrial equipment parts is given. The most universal method of laser surfacing is considered laser powder cladding. The results of experimental studies on the choice of parameters of surfacing modes for a single track are presented: laser power, mass flow rate of powder for deposition, and surfacing speed. Samples made of 08H18N10T steel were used as a substrate for testing. Laser powder cladding was performed on a robotic complex with an ytterbium fiber laser and a coaxial powder feed. When measuring macrogeometry, the quality of a single track was evaluated by its geometric dimensions: height, width, and depth of the layer mixing of the surfaced and base materials (substrate). Variable parameters of the surfacing process were the output power of laser radiation, processing speed, and mass flow rate of the powder. The quality of a single clad track was evaluated by its geometric dimensions: height, width, and depth of the layer mixing of the surfaced and base materials (substrate). it is Shown that the value of d depends on the mass flow rate and the power of the laser radiation: when increasing mass flow rate, it is necessary to increase power of the laser radiation to ensure a constant value of depth of the layer mixing. The shape of the deposited clad track is close to a half-ellipse only when the laser power not more than 1000 W and mass flow rate 15 g/min. The height of depends on the value of mass flow rate and the laser power: when increasing mass flow rate, an increase in laser power is required in approximately the same ratio. The width of the surfacing with increasing mass flow rate at a constant power of laser radiation decreases due to the fact that the cooling rate of the liquid phase of the metal melt is very high and only superheated melt can increase the width of the clad track.

Plasma Etching Behavior of YOF Coating Deposited by Suspension Plasma Spraying in Inductively Coupled CHF3/Ar Plasma

Dense yttrium oxyfluoride (YOF) coating was successfully deposited by suspension plasma spraying (SPS) with coaxial feeding. After deposition for 6 min at a plasma power of 105 kW, the thickness of the YOF coating was 55 ± 3.2 µm with a porosity of 0.15% ± 0.01% and the coating rate was ~9.2 µm/min. The crystalline structure of trigonal YOF was confirmed by X-ray diffractometry (XRD). The etching behavior of the YOF coating was studied using inductively coupled CHF3/Ar plasma in comparison with those of the Al2O3 bulk and Y2O3 coating. Crater-like erosion sites and cavities were formed on the whole surface of the Al2O3 bulk and Y2O3 coating. In contrast, the surface of the YOF coating showed no noticeable difference before and after exposure to the CHF3/Ar plasma. Such high resistance of the YOF coating to fluorocarbon plasma comes from the strongly fluorinated layer on the surface. The fluorination on the surface of materials was confirmed by X-ray photoelectron spectrum analysis (XPS). Depth profiles of the compositions of Al2O3, Y2O3, and YOF samples by XPS revealed that the fluorination layer of the YOF coating was much thicker than those of Al2O3 and Y2O3. These results indicate that if the inner wall of the semiconductor process chamber is coated by YOF using SPS, the generation of contamination particles would be minimized during the fluorocarbon plasma etching process.