Coaxial Feed Line Research Articles

Design and Optimization of a Mid-Field Wireless Power Transfer System for Enhanced Energy Transfer Efficiency

Mid-field wireless power transfer (WPT) offers a compelling solution for delivering power to miniature implantable medical devices deep within the human body. Despite its potential, the current power delivery levels remain constrained, and the design of a compact source structure to focus the transmitter field on such implants presents significant challenges. In this paper, a novel miniaturized transmitter antenna operating at 1.71 GHz is proposed. Leveraging the antenna proximity-coupled feeding technique, we achieve optimal current distribution for efficient power transfer. Additionally, a receiver integrated within the human body is proposed, comprising a slotted ground and a meandering slotted radiating element. This receiver is excited via a coaxial feedline with a truncated ground. Our findings demonstrate wireless power transfer of −23 dB (0.501%) at a distance of 30 mm between the transmitter and receiver, alongside a peak gain of −20 dB with an impedance bandwidth of 39.61%. These results highlight promising advancements in enhancing energy transfer efficiency for deep-implant applications.

Experimental investigation of a dual mode antenna using characteristic mode analysis with enhanced directivity for GSM/5G applications

In this article, a dual-mode, dual-polarized antenna designed using characteristic mode analysis (CMA) is described. An elliptical-shaped patch radiator is chosen with double slits on its minor axis. This design is based on mode separation from the circular patch into the elliptical patch. The suggested antenna geometry has a footprint of 60 mm × 60 mm × 1.6 mm. To design and fabricate the antenna, an FR-4 substrate with a relative permittivity of 4.3 is used, along with copper sheets 0.035 mm thick for the ground plane and the radiating plane. The circular patch has the resonating mode at 1.8 GHz, whereas the elliptical radiator gives different resonant modes at 1.8 GHz and 3.5 GHz. An orthogonal mode is excited with a 50-Ω coaxial feed line at 3.5 GHz by applying a full-wave approach. The antenna gives a −10dB bandwidth of 51 MHz (1.77–1.82 GHz) centered at 1.8 GHz and a bandwidth of 210 MHz (3.37–3.58 GHz) centered at 3.5 GHz. The working principle is explained through modal analysis and characteristic angles. This dual-band antenna covers a 1.8 GHz GSM band with horizontal polarization and a 3.5 GHz 5G service with vertical polarization. Peak gain attained with these bands is 5.9 dBi and 7.1 dBi, respectively. A CST full-wave simulator is used for the simulations. As a result of the antenna, radiation is stable and enhanced. Compared to measured results, simulation results are close to reality. The characteristic mode analysis (CMA) provides an in-depth look into different operating modes on the antenna in contrast with the conventional method, which relies on the simulated current distribution to verify functionality.

Design circular polarized antenna at ISM band for WBAN using parasitic elements

This work represents a single layer wide band circular polarized (CP) antenna with broadside high gain. The antenna configuration comprises an elliptical patch serving as the main radiating element, accompanied by eight parasitic components positioned on the same plane as the patch. This setup demonstrates an enhancement in the antenna's bandwidth and gain in the broadside direction compared to conventional antennas. A detailed analysis of the significant modes, using the characteristic mode analysis (CMA) approach, has been employed to optimize the antenna. This optimization has resulted in a notable increase in the 3-dB axial ratio (AR) bandwidth and radiation gain in the broadside direction, attributed to the presence of extra harmonics and the improved aperture efficiency of the parasitic elements. The significant modes are excited via a full-wave electromagnetic (EM) simulation, utilizing a 50 Ω coaxial feed line in the primary antenna. Furthermore, the proposed antenna's functionality is examined through an analysis based on an equivalent circuit model (ECM). To demonstrate the feasibility of the design approach, an antenna prototype is fabricated on a low-cost FR4 material, occupying an overall volume of 0.58λo×0.58λo×0.030λo (λo is the center operating. frequency). The measured results demonstrate that the suggested antenna operates within a frequency band ranging from 5485 to 6130 MHz for |S11| −10 dB, and the 3-dB axial ratio ranges from 5680 to 5900 MHz. Moreover, the fabricated antenna demonstrates a high gain radiation of 7–7.05 dBi cover the ISM band for biomedical applications.

A Circularly Polarized Complementary Antenna with Substrate Integrated Coaxial Line Feed for X-Band Applications

This work presents a design for a complementary antenna with circular polarization that has a wide operating bandwidth, stable broadside radiation, and stable gain for X-band applications. The proposed antenna consists of an irregular loop and a parasitic electric dipole, which work together to produce equivalent radiation from the magnetic and electric dipoles. By arranging the dipole and the loop in a specific geometry, this antenna effectively generates circularly polarized wave propagation. A substrate integrated coaxial line (SICL) is applied to feed the antenna through an aperture cutting on the ground. The proposed antenna achieves a wide axial ratio (AR) and impedance bandwidths of 27.4% (from 8.5 to 11.22 GHz, for the AR ≤ 3 dB) and 39.6% (from 7.5 to 11.2 GHz, for the reflection coefficient ≤ −10 dB), respectively. Moreover, the antenna maintains a stable broadside radiation pattern across the operating bandwidth, with an average gain of 10 dBic. This proposed antenna design is competitive for X-band wireless communications.

Coaxial Line and Ground Separated Beam-Steering Yagi–Uda Antenna Controlled by Gravity

This letter presents a beam-steering antenna controlled by gravity. It provides a new beam-steering mechanism. The maximum radiation direction could be adjusted by assigning the center of gravity of the ground. The coaxial feed line and ground are separated, granting the ability for rotation between the two components. As the verification, based on the proposed structure, a prototype Yagi-Uda antenna working at 2.45GHz is manufactured and measured. The antenna realized 360° rotation, and the peak gain is 6.8dBi. Passive beam control could be achieved, and the variation of the gain in the desired direction is within 0.2dB during steering. The simulation results of the antenna prototype agree with the measured ones. This simple and practical structure provides a new solution for systems which demand adaptive antenna beam in certain directions.

A Compact Modified Two-Arm Rectangular Spiral Implantable Antenna Design for ISM Band Biosensing Applications

This paper presents a new microstrip implantable antenna (MIA) design based on the two-arm rectangular spiral (TARS) element for ISM band (Industrial, Scientific, and Medical 2.4–2.48 GHz) biotelemetric sensing applications. In the antenna design, the radiating element consists of a two-arm rectangular spiral placed on a ground-supported dielectric layer with a permittivity of ϵr = 10.2 and a metallic line surrounding this spiral. Considering the practical implementation, in the proposed TARS-MIA, a superstrate of the same material is used to prevent contact between the tissue and the metallic radiator element. The TARS-MIA has a compact size of 10 × 10 × 2.56 mm3 and is excited by a 50 Ω coaxial feed line. The impedance bandwidth of the TARS-MIA is from 2.39 to 2.51 GHz considering a 50 Ω system, and has a directional radiation pattern with directivity of 3.18 dBi. Numerical analysis of the proposed microstrip antenna design is carried out in an environment with dielectric properties of rat skin (Cole–Cole model ϵf (ω), ρ = 1050 kg/m3) via CST Microwave Studio. The proposed TARS-MIA is fabricated using Rogers 3210 laminate with dielectric permittivity of ϵr = 10.2. The in vitro input reflection coefficient measurements are realized in a rat skin-mimicking liquid reported in the literature. It is observed that the in vitro measurement and simulation results are compatible, except for some inconsistencies due to manufacturing and material tolerances. The novelty of this paper is that the proposed antenna has a unique two-armed square spiral geometry along with a compact size. Moreover, an important contribution of the paper is the consideration of the radiation performance of the proposed antenna design in a realistic homogeneous 3D rat model. Ultimately, the proposed TARS-MIA may be a good alternative for ISM-band biosensing operations with its miniature size and acceptable radiation performance compared to its counterparts.

A Wideband Compact Printed Dipole Antenna Array With SICL Feeding Network for 5G Application

A wideband compact printed dipole antenna array with an element size of 0.16 λ0 × 0.34 λ0 is proposed for millimeter-wave (mmW) applications, particularly for 5G applications. The two patches of the dipole are printed on two different layers to achieve a wide bandwidth of 50% (24–40 GHz) for SWR <2. Ground-signal-ground transmission line construction with a height difference between the feeding via and the two shorting vias is employed to achieve a relatively symmetrical radiation pattern. An antenna array consisting of the proposed antenna and a 1 to 8 substrate-integrated coaxial line feeding network is fabricated and measured. Simulations are also used to verify the beam scanning performance (up to ±50°). The proposed compact printed dipole antenna is a good contender for 5G mmW applications due to its wide band, compact size, and good beam scanning performance.

Reconfigurable planar inverted-F antenna for radio frequency identification tag and global positioning system applications

This paper presents the design of a reconfigurable planar inverted-F antenna (PIFA). The proposed antenna is designed and optimized to operate in two frequency bands. 2.4 GHz allocated to the industrial, scientific and medical (ISM) band for the identification of a set of vehicules within a given area, and 1.575 GHz allocated to the global positioning system (GPS) band to locate them outside. The ISM band is used for microwave frequencies for active radio frequency identification (RFID) tag, which is associated with the object to be identified. This antenna consists of two radiating elements connected by a positive-intrinsic-negative (PIN) diode to obtain the frequency reconfigurability. The first radiating element is connected to the ground plane by a shorting pin and excited by a 50 Ω coaxial feed line. Its total size is 30 mm × 50 mm × 7 mm. The substrate used is FR4 with constant dielectric relativity of 4.4 and a height of 1.6 mm. Computer simulation technology microwave studio (CST MWS) software is used to simulate and optimize the proposed reconfigurable PIFA antenna.

A simple cavity method which increases bandwidth of cylindrical dipole antennas to almost 100%

A broadband dipole antenna and an integrated cavity section responsible for increasing bandwidth are introduced, designed, and successfully fabricated. This simple and highly effective cavity is added at the dipoles input, where the concentric coaxial feed line becomes its inner conductor, and the dipoles cylinder becomes its outer conductor. This coaxial-fed dipole antenna could be easily fabricated due to its simple mechanical structure. A version of this type of dipole antenna, with a total length of less than 38 cm (0.44λ) and a radius of about 5 cm, is designed once symmetrically and once with an asymmetrical down-tilted radiation pattern. The new proposed cavity part can increase the antenna's bandwidth up to 100%, which is highly superior compared to conventional counterparts. Furthermore, the antenna's radiation pattern is stable throughout the bandwidth. The minimum realized gain at the solid angle of θ (for instance, θ between 90 and 120°) is perfectly above zero within the frequency range. The antenna measurement results are in acceptable agreement with the simulations.

An RHCP and LHCP polarization reconfigurable microstrip antenna for ISM band smart city applications

Abstract In this article, a microstrip antenna having circular polarization switching capability is presented. This antenna consists of a circular-shaped radiating patch with a single co-axial probe feed line. The polarization reconfigurability is achieved by introducing four symmetrical U-shaped slots and silicon PIN diodes on the radiating patch. A prototype of the design is fabricated on an FR-4 substrate with overall dimension of 70 × 70 × 1.6 mm to verify the performances. The measured results of the antenna exhibit an impedance bandwidth (S 11 &lt; −10 dB) of 5% in the frequency range of 2.37–2.49 GHz. The maximum gain of the antenna is found to be 2.99 dBic at 2.43 GHz. The antenna shows stable radiation performances at 2.4 GHz with 4.1% of 3-dB axial ratio bandwidth, and more than 105° of 3-dB axial ratio beamwidth for both right-hand circular polarization and left -hand circular polarization which make it suitable for ISM band Smart city applications.

Open-Ended Transmission Coaxial Probes for Sarcopenia Assessment.

We developed a handheld, side-by-side transmission-based probe for interrogating tissue to diagnose sarcopenia—a condition largely characterized by muscle loss and replacement by fat. While commercial microwave reflection-based probes exist, they can only be used in a lab for a variety of applications. The penetration depth of these probes is only in the order of 0.3 mm, which does not even traverse the skin layer, and minor motion of the coaxial feedlines can completely dismantle the calibration. Our device builds primarily on the transmission-based concept that allows for substantially greater signal penetration depth operating over a very broad bandwidth. Additional features were integrated to further improve the penetration, optimize the geometry for a more focused planar excitation, and juxtapose the coaxial apertures for more controlled interrogation. The larger coaxial apertures further increased the penetration depth while retaining the broadband performance. Three-dimensional printing technology made it possible for the apertures to be compressed into ellipses for interrogation in a near-planar geometry. Finally, fixed side-by-side positioning provided repeatable and reliable performance. The probes were also not susceptible to multipath signal corruption due to the close proximity of the transmitting and receiving apertures. The new concept worked from 100 MHz to over 8 GHz and could sense property changes as deep as 2–3 cm. While the signal changes due to deeper feature aberrations were more subtle than for signals emanating from the skin and subcutaneous fat layers, the large property contrast between muscle and fat is a sarcopenic indication that helps to distinguish even the deepest objects. This device has the potential to provide needed specificity information about the relevant underlying tissue.

Design of High Gain Slotted Circular Microstrip Antenna for X-band Applications

In this study, new structures of circular microstrip antennas, which operating in X-band frequency using etched slots on the patch radiating, are designed and simulated. These slots are rectangular and crescent shapes in different sizes. The proposed structures are fed by a coaxial line feed. The antennas designed are simulated and studied in order to obtain the optimum performance of the proposed antenna using Ansoft High Frequency Structure Simulator. The simulated results were discussed in terms of reflection coefficient, input impedance, gain, radiation patterns and surface currents. It is found that the optimum antenna design has resonance frequency 9.346 GHz with a bandwidth of reflection coefficient of 705 MHz, which is required for X-band applications. Therefore, this optimum designed is helpful for many applications in the system of modern wireless communication.

Dual-band (28/38 GHz) Yagi–Uda Antenna with Corrugated Radiator and Triangular Reflectors for 5G Mobile Phones

A novel printed design of a Yagi-Uda antenna is introduced for dual-band operation at 28/38 GHz. A corrugated strip dipole with a capacitively end-coupled extension strip is employed as the driven element. The proposed antenna has two triangular-shape reflectors and one director. The driven dipole is fed through a coaxial feed line constructed as three unequal length transition strips. A four-port MIMO antenna system constructed using the proposed Yagi-Uda is suggested for mobile phones. CST® simulator is used to study the effect of the different design parameters on the antenna gain and the operating bands. Numerical and experimental investigations are achieved to assess the performance of both the single-element antenna and the four-port MIMO antenna system. It is shown that the simulation results agree with the experimental measurements and both show good performance of the single antenna as well as the MIMO antenna system. The bandwidths achieved around 28 GHz and 38 GHz are about 4G Hz and 1.4 GHz, respectively. The gain of the antenna is about 9 and 10 dB at 28 and 38 GHz, respectively. The four antenna configuration shows radiation pattern diversity required for MIMO system. The envelope correlation coefficient (ECC) and the diversity gain (DG) are calculated and the results show that the proposed MIMO antenna system is suitable for the forthcoming 5G mobile communications.

Nearly spherical ablation zone with minimally invasive microwave ablation: Analysis and experimental characterization of a tapered-tip symmetric dipole antenna

Microwave ablation (MWA) is a widely used technology for tumors treatments. The reported asymmetric dipole antennas were not ideal in ablation zone. Although some methods were proposed to improve the ablation performance, other important characteristics were still not satisfactory enough, such as poor impedance matching, increased invasion diameter, or additional insertion devices. In this paper, a minimally invasive antenna with a nearly spherical ablation zone for microwave ablation is presented by a tapered-tip symmetric dipole structure with a sleeve. The tapered-tip symmetric dipole, fed by a coaxial line, are composed of a tapered-tip cylinder arm and a hollow cylinder arm. Both of the lengths of the two arms are approximately equal to a quarter of wavelength. The proposed antenna provides good matching at resonating frequency without any extra impedance matching network. Moreover, the tapered-tip structure enables the proposed MWA antenna be inserted into the tissues directly without an additional needle-shape catheter. Furthermore, the sleeve structure, electrically isolated from the dipole and the coaxial feed line, is employed to prevent the current and thermal from flowing along the feed line. A minimally invasive antenna with a diameter of only 1.9 mm working at 2.45 GHz is designed and fabricated for verification, in which different input power and heating time are taken into account. The temperature evolution in four locations of the liver tissue is recorded by using a 4-channel temperature monitoring system. The comparison with a commercial MWA antenna of the same diameter is also included. Simulation and experiment results show that the proposed MWA antenna create nearly spherical ablation zones. The proposed MWA antenna would be promising for minimally invasive medical applications.

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.

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.

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.

Improving the Gain Performance of 2 × 2 U-Slot Air Substrate Patch Antenna Array Operated at 28 GHz Wideband Resonance for 5G Application

In this paper, a 28-GHz dual 2 × 2 U-slot air substrate patch antenna array for 5G application is proposed. The idea of the U-slot antenna was applied in the patch antenna design which intended to decrease the antenna size. The structure of the U-slot patch antenna comprises a patch, two slots of U-shape, a ground plane, and coaxial feed lines. The proposed configuration of 2 x 2 U-slot array shows a high gain. With an extra U-slot, the proposed antenna yielded a bandwidth of about 3.93 GHz, the maximum gain of 14.5 dBi in the yz-plane, and performance efficiency of 85.82 %

Symmetry Versus Balance in Balancing Networks for Dipolar Antennas

Imperfect balancing networks (baluns) have been identified as a source of error in emission and site attenuation measurements. For this reason, performance tests have been developed to characterize the symmetry of baluns. We draw a distinction between symmetry and balance as they relate to baluns and describe both quantitatively in terms of three-port network parameters. It is shown that a symmetric balun alone does not necessarily eliminate common-mode (CM) current on the feed transmission line. CM current on the feed transmission line is minimized by use of a current balun. However, for a given implementation, such as a transmission-line transformer, some types of baluns are more difficult to implement than others and an imperfect, asymmetric current balun may perform worse than another type of balun (e.g., voltage), which is more symmetric. The case of a vertically polarized biconical antenna situated over a ground plane and driven from a coaxial feed line via a balun is examined for three symmetric baluns: a voltage balun, a current balun, and a $180^{\circ }$ power divider. It is shown that although all three baluns are symmetric, only the current balun maintains the dipolar pattern under the asymmetrical influence of the ground plane.