Coaxial Feed Research Articles

Compact triple‐mode bandpass filters based on single perturbed substrate integrated waveguide cavity using coaxial feed

AbstractA compact triple‐mode bandpass filter (BPF) based on a modified rectangular substrate integrated waveguide (SIW) cavity is presented. The perturbation of the dominant mode (TE101) and the third resonance mode (TE102) are realized by two metalized vias in order to keep the first three resonant modes evenly distributed in the passband. Using this strategy, we can control both bandwidth and finite‐transmission zero (FTZ). The bandwidth of BPF can be controlled by simply changing the diameter of the metalized vias. Coaxial excitation is used to achieve a parallel coupling with small external quality factor, resulting in a wideband response. The proposed triple‐mode SIW BPF also has an FTZ, which is decided by the angle between two feeds. In order to verify the proposed strategy, two samples with a center frequency of 5.5 GHz have been designed and manufactured.

Compact self decoupled MIMO antenna pairs covering 3.4–3.6 GHz band for 5G handheld device applications

A self-decoupled 4-port multiple-input multiple-output (MIMO) antenna pair working in the midband of the 5G spectrum (3.5 GHz) for handheld device application is presented in this paper. The antenna includes two vertically placed blocks printed exactly at the middle of the two lengthy frames of the handheld device. The self-decoupled antenna pair structure consists of two monopole antenna separated by a distance of 7 mm, a T-shaped parasitic structure, and a stub at the backside connecting the ground plane. The monopole antennas are excited by a simple coaxial feeding structure. The T-shaped element not only serves as a radiator but plays a vital role in providing port isolation between the two ports to obtain a self-isolated antenna pair. The self-decoupled antenna pair operates from 3.4 to 3.6 GHz with isolation higher than −16.5 dB in the entire utilization band. The parametric analysis of the optimal parameters and the evolution design of the antenna pair is studied for a better interpretation of the working principle of the MIMO system. The total efficiency and peak gain of all the antennas are more than 78% and 5 dB respectively in the whole utilization bandwidth. The worst-case envelope correlation coefficient (ECC) value among the elements of the antenna pair is less than 0.03, which is less than the ideal value of 0.5. Other MIMO diversity parameters such as Channel Capacity Loss (CCL), Mean Effective Gain (MEG), Total Active Reflection Coefficient (TARC), and Diversity Gain (DG) of the designed antenna are calculated and analyzed with the measured results. A model of the designed handheld device is fabricated and analyzed. The measured results indicate the suitability of the design for a capable candidate in 5G handheld device applications.

Thermal behavior and microstructure evolution mechanism of Ti6Al4V 80 mm thick plates jointed by laser melting deposition

The traditional welding processes are challenging to obtain an excellent jointed structure with a thickness of over 80 mm. Meanwhile, cyclic heating for large-scale manufacturing components worsens microstructure and mechanical properties after welding. Laser Melting Deposition (LMD) technology is put forward to break through the limit of large-scale jointing components widely used for manufacturing aerospace products. Therefore, the LMD experiment with coaxial powder feeding for joining a pair of X-groove Ti-6Al-4V thick plates (80 mm) with different thermal behaviors (including laser scanning speeds and cooling rates) is carried out in this paper. The morphology evolution of its microstructure at the equiaxed grain zone (EQZ) and the deposition area under different thermal behaviors are systematically investigated. Meanwhile, the relationship between microstructure evolution mechanism and tensile properties is further explored. The volume fraction and size of acicular α/α' phases at the EQZ or the deposition area keep a stable rising when the laser scanning speed increase from 10mm/s to 20mm/s. The α-Ti cluster phases are usually precipitate around the β grain boundary with a low scanning speed and cooling rate. By contrast, the orthogonal acicular martensitic α/α' phase can precipitate inside the β grain, forming a Basketweave structure with a high scanning speed and cooling rate. The Basketweave structure forming in β grains can coordinate the deformation and reduce the stacking effect of dislocations, which is beneficial for improving ductility. However, the α-Ti cluster phases precipitating around the β grain boundary usually cause local stress concentration at these locations, forming microcracks at this location and deteriorating the tensile properties.

Microstructures and mechanical properties of reduced activation ferritic/martensitic steel fabricated by laser melting deposition

Laser melting deposition (LMD) is a promising way for the fabrication of complex reduced activation ferritic/martensitic (RAFM) steel components which provides an exceptional opportunity to improve the existing designs and move toward fabricating fine features and complex geometries with higher efficiencies. It is well known that if steel members are welded together, defects will be concentrated in the welded joint. We can control the scanning path of the laser to achieve a complex component molding, avoiding welding. Considering the LMD technology, the results of each layer of powder molding will affect the fineness of the final processed products, such as laser power, scanning speed, defocus and so on, which are all important factors affecting the products. We control the size of powder particle size as a variable to conduct a study on RAFM steel supplemented by LMD technology for the first time, and its microstructure and grain size were analyzed. In terms of mechanical properties, its hardness, Charpy impact, tensile strength and elongation were measured. The results show that compared with other processing processes including Selective Laser Melting (SLM), rolling, welding joints, the tensile strength of RAFM steel manufactured by laser coaxial powder feeding is up to 1057.75 MPa, and there are no pores and almost no defects when using small particle size powder. The microstructure of LMD RAFM steel contains a large amount of lath martensite and δ-ferrite, and some precipitates such as Mx, whose average grain size decreases with the increase of powder particle size (5–150 μm). In this study, the laser additive process was monitored by high-speed photography, and the average grain size of LMD RAFM steel was further analyzed, and a reasonable explanation of its mechanical properties was given.

Design a New Type of Laser Cladding Nozzle and Thermal Fluid Solid Multi-Field Simulation Analysis.

Coaxial powder feeding technology in the field of metal additive manufacturing is booming. In this paper, a new laser cladding nozzle with powder feeding channels of inner and outer rings is designed. The nozzle works with a new kind of laser, which is a new heat source with an inner beam and outer beams. The water-cooling channels are simulated in Ansys Workbench. The simulation results present the temperature distribution of the working nozzle and the velocity of the cooling water. The thermal dilation of the nozzle in the working environment is also simulated. The results show that the loop water cooling channel could effectively reduce the high temperature of the nozzle down to about 200 °C. In addition, it could well restrain the thermal deformation of the nozzle lower to 0.35 mm. The equivalent stress of most parts is controlled under 360 MPa. Then, the powder flows of the inner and outer rings of the multiple powder feeding channels are simulated in Ansys Fluent. The convergence effect of the powder flow could be assumed and some significant parameters, such as the velocity, are acquired. The results present that these multiple powder feeding channels could realize the generation and removal of removable supports of workpieces with highly complex shapes and achieve a large processing range and good processing efficiency. The velocity of the powder flow at the outlet is elevated to about 5 mm/s. Then, the thermal cladding states under the new laser heat source of the powder are simulated in Workbench. The temperature of the melting process and the thermal deformation and the equivalent stress/strain of the additive parts are obtained in the emulation. The results emerge that the powder melting range and the ascending temperature of the melting pool are improved with this effect. The greatest temperature of the melting pool is about 2900 °C in the machining process, and the maximum thermal equivalent stress is 1.1407 × 1010 Pa.

Evaluation of 8-Channel Radiative Antenna Arrays for Human Head Imaging at 10.5 Tesla.

For human head magnetic resonance imaging at 10.5 tesla (T), we built an 8-channel transceiver dipole antenna array and evaluated the influence of coaxial feed cables. The influence of coaxial feed cables was evaluated in simulation and compared against a physically constructed array in terms of transmit magnetic field (B1+) and specific absorption rate (SAR) efficiency. A substantial drop (23.1% in simulation and 20.7% in experiment) in B1+ efficiency was observed with a tight coaxial feed cable setup. For the investigation of the feed location, the center-fed dipole antenna array was compared to two 8-channel end-fed arrays: monopole and sleeve antenna arrays. The simulation results with a phantom indicate that these arrays achieved ~24% higher SAR efficiency compared to the dipole antenna array. For a human head model, we observed 30.8% lower SAR efficiency with the 8-channel monopole antenna array compared to the phantom. Importantly, our simulation with the human model indicates that the sleeve antenna arrays can achieve 23.8% and 21% higher SAR efficiency compared to the dipole and monopole antenna arrays, respectively. Finally, we obtained high-resolution human cadaver images at 10.5 T with the 8-channel sleeve antenna array.

A Fifth-Order Single-Layer Dual-Band Half-Mode SIW Filtering Antenna With a Multifunctional Single Slot

A novel fifth-order dual-band half-mode substrate integrated waveguide filtering antenna with a multifunctional single slot and seven shorting pins of different sizes integrated into a single layer is presented in this letter. Initially, the fifth-order modes TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2,1</sub> , TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5/2,1</sub> , TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2,3</sub> , and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5/2,3</sub> have been excited successively by the coaxial feed. Then, seven shorting pins of different sizes have been loaded to reallocate these modes to form dual passband characteristics and generate three transmission zeros. In addition, a multifunctional slot has been etched to improve the out-of-band suppression, and the radiation gain of the second passband has increased approximately by 5.5 dB. Finally, a prototype has been fabricated and measured to validate the design. The measured results show that the proposed antenna has a $-$10 dB bandwidth from 2.49-2.56 GHz and 3.37-3.49 GHz. It has a peak gain of 7.9 and 8.55 dBi within passband, which are in good agreement with the simulated results.

Dual-Band Square Microstrip Patch Antenna for 4G/LTE and Wi-Fi Applications

Abstract: A dual-band, Square-shaped Microstrip Patch Antenna (SMPA) with two opposite corner cuts is proposed. The presented design is suitable for 4G/LTE and Wi-Fi applications as it resonates at 2.13GHz and 2.41GHz frequencies. The FR4 substrate with co-axial feed is used for fabrication and is simulated using CST software. The simulation result provides enhanced antenna specification of return loss (-42.64&amp;-20.13) dB, bandwidth (62.7&amp;89) MHz and percentage bandwidth (2.94&amp;3.69) % than the conventional antenna prototype. Furthermore, a comparative study of simulated and experimental findings is analyzed in this manuscript. Keywords: Dual-band, return Loss, Bandwidth, Percentage Bandwidth, 4G/LTE, Wi-Fi

Circularly Polarized Dielectric Resonator Antenna for mm- Wave Applications

This paper presents a circularly polarized (CP) dielectric resonator antenna (DRA) for mm-wave applications. The antenna consists of a cylindrical DRA excited with coaxial feed. To obtain CP, the DRA is loaded with another parasitic dielectric cylinder of different dielectric properties, overlapping the primary cylinder. The proposed antenna operates at 26.9 GHz having impedance bandwidth (BW) of 5 GHz and axial ratio (AR) BW of 40%. The antenna exhibits peak gain of 6.5 dB.

Compact combined antenna for high‐power ultrawideband radiation sources with subnanosecond pulse duration

AbstractThe paper presents the design of a combined antenna, optimized in numerical calculations to radiate high‐power bipolar pulses with a duration of 0.5 ns. According to the results of the calculations, a compact antenna with the dimensions of 60 × 65 × 55 mm3 (width × height × length) was made. The influence of a high‐voltage insulator position relative to the antenna input on the matching band of the antenna with the coaxial feeder is shown. In the absence of an isolator, the matching band is in the range of 0.98–9.33 GHz. The antenna efficiency by the peak electric field strength and the energy efficiency are equal to 0.75–0.8 and 0.9, respectively.

Mechanically strong, stiff, and yet ductile AlSi7Mg/graphene composites by laser metal deposition additive manufacturing

Laser metal deposition (LMD) with a coaxial powder feeding technology has been applied to fabricate pure aluminum alloy (AlSi7Mg) and low oxidation graphene aluminum matrix (LOG-Al) composites with low oxidation graphene (LOG) contents of 0.05 wt % and 0.1 wt % after the powder was prepared by wet ball milling. The LOG-Al composites showed improvements in all properties including hardness, tensile strength, ductility, modulus of elasticity and yield strength with the increase of LOG addition contents. The microstructures and fracture surfaces of the composites were observed and the results of TEM, HRTEM, optical microscope, EBSD, XRD spectra, Raman spectra, Vickers hardness, tensile properties were analyzed. The effects of wet ball milling, the addition of low oxidation graphene and its contents and LMD process on microstructure formation and resulting mechanical properties were discussed.

Directivity and VSWR Enhancement of Microstrip Patch Antenna at 2.45GHz Using Novel Inset Fed Microstrip Line Feed for Bluetooth Communications in Comparison with Coaxial Probe Feed

Aim: The main objective of this project is to design a rectangular-shaped microstrip patch antenna at a frequency of 2.45GHz to enhance the Directivity and VSWR using Inset fed technique in Bluetooth Communications. Materials &amp; Methods: Microstrip patch antenna with microstrip line feed technique and Coaxial probe feed technique is used with a sample size of 40. Results: By using HFSS Simulation Software Gain, Directivity, VSWR and Return Loss of Microstrip patch antenna are improved and noted in comparison with Coaxial probe feed antenna. The Simulation Results obtained for the designed antenna are Gain is 2.91dB, Directivity is 6.04dB, Return loss for 2.45GHz, 3.7GHz and 4.5GHz frequencies are -17.1dB, -20.1dB, -17.2dB. VSWR for 2.45GHz, 3.7GHz, 4.5GHz frequencies are 1.3, 1.2, 1.3. Attained significance accuracy ratio p(&lt;0.05) for Gain and Directivity and p(&lt;0.04) for return loss and vswr in Statistical Analysis. Conclusion: Performance parameters of Microstrip Patch antenna with microstrip line feed technique appears to be improved when compared with Coaxial probe feed technique. From the results, the proposed antenna can be used for Bluetooth Communications and Tri-band applications.

Orthogonal mode dual band MIMO antenna system for 5G smartphone applications using characteristic mode analysis

PurposeThe purpose of this paper is to provide a miniaturized antenna design for a mobile phone. The second design is 2 × 4 elements multiple-input multiple-output (MIMO) antenna with 8 port having a substrate size is 20 × 40 mm2 which fits easier within smartphone handset devices for fifth generation technology.Design/methodology/approachIn this work, the first design is a conventional patch antenna, and its dual-band characteristics are obtained by characteristic mode analysis. In this method, orthogonal modes are carried out for 28 GHz and 38 GHz, and further, both orthogonal modes are excited by finite integration technique full-wave method with 50 Ohm single port coaxial feed line.FindingsIn this configuration, better return loss, high gain, larger bandwidths and low envelope correlation coefficient (ECC) are evaluated by the full-wave simulation computer simulation technology (CST) studio suite.Originality/valueIn this arrangement, the performance metrics of the antenna are analyzed using electromagnetic simulator CST Studio suite.

A wideband dual‐polarized magneto‐electric dipole antenna loaded with a disk

A novel wideband dual-polarized antenna with load of a disk is presented in this letter. The antenna is composed of two cross magneto-electric dipole antennas vertically fixed on an aluminum plate as ground plane, which are excited by two similar Γ-shaped coaxial feeder. Furthermore, in order to further broaden the impedance bandwidth, a disc-shaped resonator is loaded on the front end of the dipole. And a metal barrel reflector is loaded around the antenna to further improve the antenna's radiation characteristics. Measured results show that the proposed antenna achieves a 10 dB with bandwidth of 1.2–2.4 GHz, and its port isolation is higher than 28 dB. Moreover, stable radiation pattern with a peak gain of 7.7–9.2 dB is obtained within that band.

Effects of Defocus Distance on Three-Beam Laser Internal Coaxial Wire Cladding

Three-beam laser internal coaxial wire feeding cladding is regarded as a promising additive manufacturing technique because it is highly efficient and controllable. In this study, the effects of the defocus distance on cladding using a three-beam laser with internal wire feeding are experimentally and numerically studied. A process map indicating the surface characteristics at different defocus distances with various parameter combinations was developed. The transmission characteristics including laser intensity, beam size, and laser spot distance of the three-beam laser at different defocus distances were analyzed using TracePro software. Based on the TracePro results as heat source, a three-dimensional transient finite element (FE) thermal model was formulated to predict the thermal field, temperature history and molten pool shape at different defocus distances. A molten pool with a flat bottom and low melting depth is generated when the defocus distance is − 2.5 mm, whereas when this distance is − 1.5 mm, a pool with a valley-shaped bond and high melting depth is formed. The simulated results of the temperature cycle and clad geometry are both validated and found to well agree with experimental measurements. The influence of the defocus distance on the microstructure and microhardness are discussed based on the temperature history and cooling rate. With the increase in the absolute defocus distance, the height and dilution of the clad decreased, whereas the width increased. In addition, the effects of defocus distance with various parameter combinations on clad geometry were explored using the formulated FE model.

Investigation on dual‐band equilateral triangular shaped dielectric resonator antennas for WLAN applications

In this article, two configurations of dual-band equilateral triangular dielectric resonator antennas (ETDRAs) for WLAN applications are proposed namely, configuration-I and configuration-II. The configuration-I uses single ETDRA for dual-band operation; whereas, configuration-II includes two ETDRAs to operate as a dual-band antenna. Both the antenna configurations, which uses 99.7% alumina material having a dielectric constant of εr = 9.9, are excited to operate in the bands of 2.4 to 2.5 GHz and 5.75 to 5.85 GHz. The antennas are excited using a conventional coaxial feed to have a simple feeding mechanism. Prototypes of both the antenna configurations are fabricated and measured. The radiation characteristics of the antennas are discussed. The circuit analysis for the proposed configurations of the dual-band ETDRA is also performed and an appropriate equivalent circuit for each dual-band ETDRA is presented. Further, the performance of the proposed configurations of the dual-band antennas are also compared with other dual-band DRAs reported in the literature.

A miniaturized 2-itertion rectangular slotted Sierpinski Fractal Bowtie antenna for multiband applications

Recent advancements in the field of Telecommunications and wireless technology services need compact, multiband antennas with reduced system complexity. In this paper a novel Rectangular slotted Sierpinski Fractal Bowtie antenna is illustrated and is further expanded up to 2-iterations to obtain multi frequency bands with increased percentage of Miniaturization. The overall volume of the proposed 2-iteration SPK Bowtie antenna is (50 × 50 × 1.6) mm3 and the substrate is FR-4 epoxy with 4.4 dielectric constant. All the 0th, 1st and 2nd iterations of Rectangular slotted SPK Fractal Bowtie antenna are exited with coaxial probe feed and are simulated using ANSYS HFSS software for 100 MHz to 14 GHz frequency range. The radiation parameters like return loss, Bandwidth, VSWR, and Gain are evaluated and compared. The simulation results shows that proposed 2nd iteration Rectangular slotted SPK Fractal Bowtie antenna exhibits more number of frequency bands as compared to the 0th and 1st iterations. The proposed design is able to resonate at frequencies 0.2 GHz, 3.5 GHz, 6.3 GHz, 8.6 GHz, 10.9 GHz, 11.7 GHz with a gain of 0.529 dB, 5.074 dB, 4.518 dB, 5.335 dB, 9.18 dB, 21.17 dB respectively. The percentage of Miniaturization is also increased to 58.2% in the case of 2-iteraion. A prototype of the final proposed antenna is fabricated and tested using VNA network analyzer. The fabricated prototype of proposed antenna is also capable of resonating in L, C, S, and X bands. The simulated results of the proposed antenna have a great matching with the measured results.

The Design of A Ku-K Band Single-Fed Wideband Circular-Polarized Patch Antenna

In this paper, a Ku-K band single-fed broadband circularly polarized microstrip antenna is designed. The antenna is composed of rectangular dielectric substrate and corner patch. The cut-angle patch makes the microstrip antenna work in circular polarization. The impedance bandwidth of 28.7% and the axial ratio bandwidth of 15.6% are obtained by using coaxial line feeding, tangential angle feeding and multi-patch resonance. The overall thickness of the antenna structure is 1.524mm, which meets the requirements of low profile.

Ultra-low-vibration closed-cycle cryogenic surface-electrode ion trap apparatus.

We describe the design, commissioning, and operation of an ultra-low-vibration closed-cycle cryogenic ion trap apparatus. One hundred lines for low-frequency signals and eight microwave/radio frequency coaxial feed-lines offer the possibility of implementing a small-scale ion-trap quantum processor or simulator. With all supply cables attached, more than 1.3W of cooling power at 5K is still available for absorbing energy from electrical pulses introduced to control ions. The trap itself is isolated from vibrations induced by the cold head using a helium exchange gas interface. The performance of the vibration isolation system has been characterized using a Michelson interferometer, finding residual vibration amplitudes on the order of 10nm rms. Trapping of 9Be+ ions has been demonstrated using a combination of laser ablation and photoionization.

Research on surface finish of thin-wall parts by laser with coaxial inside-beam powder feeding

Surface quality is an important performance indicator of laser metal deposition. Based on annular laser beam internal powder feeding technology, the effect of higher energy of the outer side of the annular beam on the surface roughness and waviness of thin-wall parts is studied in this paper. The influences of laser power, scanning speed, and powder feeding rate on the surface finish of thin-wall parts are investigated. The results show that the laser power has a significant effect on surface finish. With the increase in laser power, the roughness decreases and the waviness increases first and then decreases. High laser power can improve surface finish. As the scanning speed increases, the roughness decreases first and then increases, and the waviness decreases. The scanning speed has a significant influence on surface waviness. Increasing the powder feeding rate is not beneficial to surface quality because the value of the roughness and the surface waviness will add with its rising.