Antenna In Proximity Research Articles

Compact conformal metasurface antenna for hyperthermia applications

In this paper, the design, analysis and evaluation of a new compact conformal metasurface (MTS)-based bow-tie slot antenna is presented for hyperthermia treatment of cancer. A bow-tie slot antenna in close proximity with tissue designed at 2.45 GHz was used to excite the MTS layer, which is made of a 4 × 4 uniform array of square unit cells. The proposed MTS-based antenna is compact and provides enhanced penetration depth in the tissue medium as compared to the bow-tie antenna only. To verify the design concept, both the proposed MTS-based antenna and bow-tie antenna were fabricated, and the measured results are well anticipated. Finally, the MTS applicator is terminated with water bolus and tissue to characterize its hyperthermia performance in a real scenario. The key features of the proposed MTS applicator include wide impedance bandwidth (stable hyperthermia performance), enhanced penetration depth and effective field size, single-layer structure and ease of fabrication.

Textile monopole sensors for breast cancer detection

This paper presents two flexible monopole antennas implemented on cotton substrate as sensors designed for radar-based microwave imaging and particularly breast imaging systems. The flexible antennas are basic building block of a radar-based microwave imaging system that could be integrated in clothes. Thus, these low-cost textile sensors could be used by women for self-monitoring and early breast cancer detection at an affordable price. The ultra-wideband fully textile sensors are designed as rectangular and circular monopole antennas. Both sensors have an impedance bandwidth le − 10 dB from 2.2 to 8 GHz with an overall footprint of 50 × 50 mm2. Simulations for antenna in proximity to breast model with and without tumor as well as bending capacity are performed. The simulations are complemented with fabrication of a breast phantom and a tumor sample with parameters that mimic these of the human breast’s healthy and malignant tissue. Measurements are compared to simulation results as well as the performance of antenna before and after subjected to washing. Finally, the specific absorption rate is also calculated and measured to ensure safety for on-body deployment. The proposed work demonstrates the potential to develop wearable microwave imaging system using fully textile antennas.

Compact UHF RFID balun‐like integrated tag antenna for long range detection of water bottles

AbstractA compact, flexible, long‐range, and impedance transformer balun‐like integrated UHF RFID tag antenna is proposed for the detection of water bottles. To alleviate the performance of a tag antenna in close proximity to a high dielectric material such as water, the radiating element of the tag antenna uses folded, unbalanced strips made of balun‐like arms wrapped around the tag's body. As a result, a wide bandwidth with reasonably good radiation resistance is achieved. The tag's body comprises dual loops for the impedance matching to the tag chip. This leads to a long read range of 13.33 m; >5.83 m compared to other state‐of‐the‐art designs. The proposed tag antenna conforms to a small footprint by wrapping the balun‐like arms around the tag's body, which results in a compact form. The tag is fabricated, and the results reasonably agree with simulations.

Design and Analysis of a 5G Wideband Antenna for Wireless Body-Centric Network

A compact 5G wideband antenna for body-centric network (BCN) operating on Ka band has been presented in this paper. The design of the antenna consists of a very simple key-shaped radiator patch with a vertical slot for better impedance matching. The antenna was designed and simulated with the help of the Computer Simulation Technology (CST) Microwave Studio Suite, a well-liked and dependable electromagnetic simulation program running on Microsoft Windows. Free-space simulation produces a resonant frequency at 28 GHz, which falls under the Ka band and 5G’s n257, more precisely n261. The proposed antenna has a size of 1.24 λ × 0.6 λ × 0.153 λ and has a wider impedance bandwidth of more than 20 GHz. The antenna’s gain and radiation efficiency are 3.87 dBi and 70%, respectively, at the resonant point. Further parametric studies reveal that the antenna can be activated in the V-band by increasing the feedline width. The antenna is proposed for the application of BCN. Therefore, a three-dimensional human torso phantom was developed virtually to test on-body performance. The on-body findings of this antenna were resimulated by positioning the antenna in close proximity to the three-layer human body model, where 22.5 dB of on-body reflection coefficient was recorded at 28 GHz. Simulated on-body gain and efficiency were 4.56 dBi and 61.33 percent, respectively. A distance-based investigation was conducted to investigate the impacts of the human body’s presence by positioning the antenna at five different distances from the human torso model. The findings were compared to assess how distance affects its behaviors. The antenna’s gap was kept at 6 mm for the optimum results, which included 4.83 dBi of gain with a 66 percent efficiency and a recorded RL value of about 23 dB. The on-body simulations produced very consistent results with a slight deviation after 26.5 GHz, even though the distance was varied.

In Body Communication

This article makes an effort to assess the performance of a stacked meandered patch antenna in proximity of multiple homogeneous human tissue models. Nowadays, many smart wireless gadgets are being used around human vicinity, hence the performance investigation of these wireless gadgets is major concern. This article discloses the performance of meandered patch antenna for in-body communication in the MICS band. The human tissue is considerably effected by the exposure of electromagnetic radiation. Performance improvement of patch antennas used in wireless gadgets is the key solution of the problem. This article presents the estimation of parameters of stacked meandered patch antennas; reflection coefficient, radiation pattern, directive gain and VSWR in proximity of multiple homogeneous human tissue models.

Transmitted fields of a directional antenna in proximity of a wall

Transmission of a directional antenna in near proximity of a building wall modelled by a semi-finite dielectric slab above a perfectly conducting ground is investigated and an accurate and fast method to predict wall penetration loss (PL) once the source/observation points are in proximity of the wall is proposed. First, the antenna is replaced by an array of electric Hertzian dipoles with approximately the same half power beamwidth. Second, the dipole array radiation is calculated both numerically and asymptotically. They are based on computation of Sommerfeld integrals using Filon quadrature (FQ) technique and the steepest descent method, respectively. Third, PL of a typical x -polarised and y -polarised horn and a z -polarised wire antenna, simulated in FEKO using the method of moments (MoM) is compared with that of, respectively, the x -, y - and z -directed dipole arrays calculated using FQ technique. A good agreement between MoM and the dipole model results are obtained for relatively short stand-off distances for which estimation based on slab transmission coefficient is not an accurate approximation. The proposed dipole array model with FQ technique makes calculation at least 7.5 times faster than FEKO. Fourth, PL for different wall permittivity and conductivity is studied.

A Novel Low-Profile High-Gain UHF Antenna Using High-Impedance Surfaces

A novel wideband low-profile planar antenna design based on the use of a high-impedance surface (HIS) is presented for digital television (DTV) reception in the UHF band. The proposed design is based on a wideband monopole antenna in close proximity to an artificial ground plane, composed of an array of square metal loops at the top, an air gap and a ground plane at the bottom, without grounded vias. Low-cost substrates are employed in the design: rigid PVC for the antenna and foamed PVC for the artificial ground plane. The advantages of the proposed design for DTV applications are high gain, low profile, light weight, low cost and large bandwidth. Details of the proposed antenna design are described, and measurements together with a comparison to a conventional antenna with PEC ground plane are presented.

Impact compressive and bending behaviour of rocks accompanied by electromagnetic phenomena.

It is well known that electromagnetic phenomena are often observed preceding earthquakes. However, the mechanism by which these electromagnetic waves are generated during the fracture and deformation of rocks has not been fully identified. Therefore, in order to examine the relationship between the electromagnetic phenomena and the mechanical properties of rocks, uniaxial compression and three-point bending tests for two kinds of rocks with different quartz content, granite and gabbro, have been carried out at quasi-static and dynamic rates. Especially, in the bending tests, pre-cracked specimens of granite were also tested. Using a split Hopkinson pressure bar and a ferrite-core antenna in close proximity to the specimens, both the stress-strain (load-displacement) curve and simultaneous electromagnetic wave magnitude were measured. It was found that the dynamic compressive and bending strengths and the stress increase slope of both rocks were higher than those observed in static tests; therefore, there is a strain-rate dependence in their strength and stress increase rate. It was found from the tests using the pre-cracked bending specimens that the intensity of electromagnetic waves measured during crack extension increased almost proportionally to the increase of the maximum stress intensity factor of specimens. This tendency was observed in both the dynamic and quasi-static three-point bending tests for granite.

On the Impact of Antenna Disturbances by Urban Furniture on Deterministic Propagation Simulations

In this work, we study the impact of antenna radiation patterns disturbed by urban furniture on propagation characteristics. The propagation in urban scenario is modeled with a ray-based deterministic tool. Different base station scenarios are discussed: antenna in proximity of a wall; antenna mounted on a lamp post; and antenna on a bus stop shelter. The statistical influence of the support is evaluated comparing the results in terms of pathloss with the ones obtained when the isolated antenna radiation patterns are considered.

Compact Surface-Wave Assisted Beam-Steerable Antenna Based on HIS

The concept of taking surface wave as an assistant role to obtain wide beams with main directions tilting to endfire is introduced in this paper. Planar Yagi-Uda-like antennas support TE 0 surface wave propagation and exhibit endfire radiation patterns. However, when such antennas are printed on a thin grounded substrate, there is no propagation of TE mode and beams tilting to broadside. Benefiting from the advantage that the high impedance surface (HIS) could support TE and/or TM modes propagation, the idea of placing a planar Yagi-Uda-like antenna in close proximity to a HIS to excite unidirectional predominately TE surface wave in HIS is proposed. Power radiated by the feed antenna, in combination with power diffracted by the surface wave determines the total radiation pattern, resulting in the desired pattern. For verification, a compact, low-profile, pattern-reconfigurable parasitic array (having an interstrip spacing of 0.048 λ 0 ) with an integrated DC biasing circuit was fabricated and tested. Good agreement was obtained between measured and simulated results.

Performance Study of a UWB Antenna in Proximity to a Human Arm

This letter studies the frequency- and time-domain performance of a recently developed printed coplanar-fed ultrawideband (UWB) monopole antenna aiming at predicting its behavior close to a human arm. The input reflection coefficient $(\vert{ S}_{11}\vert)$ and fidelity factor of the antenna were evaluated in free space and close to an arm. Simulations using three simplified arm models with different cross sections (flat, rectangular, and elliptical) were compared to measurements. All models include the relevant human tissue layers: skin, fat, muscle, and bone. It was found that an accurate model requires the inclusion of the tissues broadband dispersion characterization. Moreover, the skin layer has a major impact in $\vert{S}_{11}\vert$ , and a small effect on fidelity, while the models can be simplified by discarding the bone. Furthermore, the geometry of the models is less relevant than dispersion characterization. It has also been observed that using the simplified models with proper broadband tissues dispersion yields good performance predictions, and that the fidelity factor increases as the antenna gets closer to the arm.

User Effects in Beam-Space MIMO

The performance and design of the novel single-RF-chain beam-space MIMO antenna concept is evaluated for the first time in the presence of the user. First, the variations of different performance parameters are evaluated when placing a beam-space MIMO antenna in close proximity to the user body in several typical operating scenarios. In addition to the typical degradation of conventional antennas in terms of radiation efficiency and impedance matching, it is observed that the user body corrupts the power balance and the orthogonality of the beam-space MIMO basis. However, capacity analyses show that throughput reduction mainly stems from the absorption in user body tissues rather than from the power imbalance and the correlation of the basis. These results confirm that the beam-space MIMO concept, so far only demonstrated in the absence of external perturbation, still performs very well in typical human body interaction scenarios.

Antenna Coupling—A Novel Mechanism of Radiofrequency Electrosurgery Complication

(1) To determine if antenna coupling occurs in common operating room scenarios. (2) To define modifiable clinical variables that reduce the magnitude of antenna coupling. Mechanisms of electrosurgical burns where monitoring devices contact the surgical patient are unclear. Antenna coupling occurs when the "bovie" active electrode (electrically active transmitting antenna) emits energy, which is captured by a nonelectrically active wire (electrically inactive receiving antenna) in close proximity without direct contact. Monopolar radiofrequency energy was delivered to a laparoscopic instrument (electrically active transmitting antenna), whereas other nonelectrically active wires (electrically inactive receiving antenna) including electrocardiogram (EKG) lead, nonactive "bovie" pencil, and nerve electrode monitor were placed in proximity. Temperature changes of tissue placed adjacent to the electrically inactive receiving antennae were measured. Nonelectrically active wires (receiving antenna) increase tissue temperature when lying parallel to the active electrode cord: EKG pad 2.4°C ± 1.2°C (P = 0.002), "bovie" pencil tip 90°C ± 9°C (P < 0.001), and nerve electrode monitor 106°C ± 12°C (P < 0.001). Factors that reduced the heat generated by antenna coupling included the following: increasing angulation between transmitting and receiving antennae (parallel = 90°C ± 9°C; 45° angle = 53°C ± 10°C; perpendicular = 35°C ± 11°C; P < .001), increasing separation distance between parallel transmitting and receiving antenna (<1 cm = 90°C ± 9°C; 15 cm = 44°C ± 18°C; 30 cm = 39°C ± 2°C; P < .001); and decreasing generator power setting (15 W = 59°C ± 11°C; 30 W = 90°C ± 9°C; 45 W = 98°C ± 8°C; P < .001). Antenna coupling occurs in common operating room scenarios. Simple, practical measures by the surgeon, such as orienting the receiving antenna at a greater angle and with greater separation to the active electrode cord, or lowering the generator power setting reduce antenna coupling.

Demonstration of a Cognitive Radio Front End Using an Optically Pumped Reconfigurable Antenna System (OPRAS)

A cognitive radio front end using an optically pumped reconfigurable antenna system (OPRAS) is investigated. The scheme consists of a ultrawideband antenna and a reconfigurable narrowband antenna in close proximity to one another. The narrowband reconfigurability is achieved by a integrating laser diodes within the antenna structure to control the switching state of photoconductive silicon switches. This scheme has the advantage of eliminating the use of optical fiber cables to guide light to the switches, and enables easier integration of the reconfigurable antenna in a complete communication system. The performance of the proposed technique is presented, and comparisons are made to other commonly used switching techniques for reconfigurable antennas, such as techniques based on PIN diodes and RF microlectromechanical systems integration. The application of this antenna design scheme serving as the receive channel in a cognitive radio communication link is also demonstrated.

On-Board Printed Coupled-Fed Loop Antenna in Close Proximity to the Surrounding Ground Plane for Penta-Band WWAN Mobile Phone

A small-size coupled-fed loop antenna suitable to be printed on the system circuit board of the mobile phone for penta-band WWAN operation (824-960/1710-2170 MHz) is presented. The loop antenna requires only a small footprint of 15 x 25 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> on the circuit board, and it can also be in close proximity to the surrounding ground plane printed on the circuit board. That is, very small or no isolation distance is required between the antenna's radiating portion and the nearby ground plane. This can lead to compact integration of the internal on-board printed antenna on the circuit board of the mobile phone, especially the slim mobile phone. The loop antenna also shows a simple structure; it is formed by a loop strip of about 87 mm with its end terminal short-circuited to the ground plane and its front section capacitively coupled to a feeding strip which is also an efficient radiator to contribute a resonant mode for the antenna's upper band to cover the GSM1800/1900/UMTS bands (1710-2170 MHz). Through the coupling excitation, the antenna can also generate a 0.25-wavelength loop resonant mode to form the antenna's lower band to cover the GSM850/900 bands (824-960 MHz). Details of the proposed antenna are presented. The SAR results for the antenna with the presence of the head and hand phantoms are also studied.

Employing EBG Structures in Multiantenna Systems for Improving Isolation and Diversity Gain

This letter investigates the effect of mutual coupling on the operation of a multiantenna system. Radiation pattern, input impedance, gain, and efficiency of a slot antenna in proximity of another slot antenna are studied through simulations. A mushroom-type electromagnetic band-gap (EBG) structure is designed to isolate the antennas and reduce the influence of coupling on radiation characteristics. Two multiantenna prototypes are fabricated and experimentally evaluated. Measurement results confirm the improvement of isolation between the antennas by 28 dB at the radiation frequency of 5.2 GHz when the EBG reflector is utilized. In addition, the diversity gain of the two prototypes are measured using a reverberation chamber demonstrating an increase of 3.3 dB in the combined received power for 99% of transmission trials when the EBG structure is added in the substrate of the multiantenna system.

Proximity Effects of Metallic Environments on High Frequency RFID Reader Antenna: Study and Applications

We study the proximity effects of metallic environments on the performance of high frequency (HF) radio frequency identification (RFID) reader antenna operating at 13.56 MHz. The performance of a typical HF RFID reader loop antenna in the proximity of various metal plate configurations is experimentally investigated in terms of resonant frequency, field intensity, and field distribution. The study shows that the presence of the metal plates shifts up the resonant frequency of the antenna and weakens its field intensity. The proximity effects are strongly dependent on the size of the metal plate, distance between the plate and the antenna as well as the orientation of the plate. Such effects greatly degrade the reading range and restrict the co-existence of HF RFID systems. A solution to alleviate the effects is to re-tune or co-design the reader antenna in proximity with the metallic objects based on the information from the study. As an example, a loop antenna is co-designed with a metal plate to configure a metal-backed loop antenna, and optimized for an RFID smart shelf system to restrain the interference and enhance the detection accuracy.

Improved Solution of Tensor-Volume Integral Equation Using Mixed-Domain MoM with Polynomial Expansion

A new approach for solution of the Tensor-Volume Integral Equation (TVIE) using Galerkin-based moment method (MoM) for three-dimensional dielectric bodies is proposed. Two problems of plane wave scattering by a dielectric sphere and a thin-wire antenna in close proximity to a dielectric body are investigated. In both cases, cubic modeling is applied and a combination of entire-domain and sub-domain basis functions, including three-dimensional polynomial functions with different degrees is utilized for field expansion inside dielectric bodies. Power polynomial is adopted for this purpose and its property is discussed over the proposed mixed-domain MoM formulation. Numerical examples show that based on the proposed method, a relative fast algorithm and suitable accuracy are achieved compared with conventional MoM. The accuracy of the proposed method is verified by comparing it with the Mie theory, conventional MoM and the FDTD method.

Electromagnetic interaction between resonant loop antenna and simulated biological tissue

AbstractThe electromagnetic interaction between a resonant loop antenna in proximity to biological tissue is examined in terms of field components, wave impedance, return loss, efficiency, and specific absorption rate (SAR). Various loop orientations are investigated with respect to the tissue, in order to provide the best coupling and power deposition into the body. An evaluation in terms of antenna detuning is also made. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2418–2421, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21959

Characteristics of a 2.4-GHz compact shorted patch antenna in close proximity to a lossy medium

Impedance and radiation characteristics of a 2.4-GHz compact shorted-patch antenna in close proximity to a lossy medium are investigated. In this study, a lossy medium with permittivity and conductivity close to those of a human torso or arm at 2.4 GHz is studied. The results obtained show that the antenna can still provide acceptable operating bandwidth (> 84 MHz covering the 2.4-GHz WLAN band) and efficiency (> 60%) when the antenna is placed very close (1-mm spacing only) to the lossy medium. The results indicate that the compact shorted-patch antenna studied is promising for application as a body-worn antenna on the body. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 480–483, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20858