RESUMEN

This paper presents a conformal, miniaturized, and geometrically simple monopole antenna designed for Vehicle-to-Everything (V2X) communications. The antenna consists of a flexible substrate, radiating patch, ground, and metallic stubs. Meandered lines are added to the U-shaped radiator to achieve the required bandwidth of the antenna. The antenna has |S11|< -10 dB magnitude from 5.06 to 7.24 GHz, attaining a peak low magnitude of-68 dB. The antenna is configured into a 4-port Multiple-Input-Multiple-Output (MIMO) setup to minimize the mutual coupling between its elements. The proposed flexible MIMO antenna offers bandwidth from 5.37 to 7.34 GHz and a peak moderate gain of 4.63 dBi with omnidirectional stable radiation patterns. To improve the mutual coupling, two hollow concentric circular structures, in combination with a pair of stub networks are integrated between the elements of the MIMO system. The transmission coefficient and surface current analysis confirm the effectiveness of the decoupling structure. The presented MIMO antenna is characterized by high isolation, a low envelope correlation coefficient (ECC), and high diversity gain, suitable for V2X MIMO communication scenarios.

RESUMEN

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.

RESUMEN

This paper presents a novel approach to the design of a brain implantable antenna tailored for brain-machine interface (BMI) technology. The design is based on a U-shaped unit-cell metamaterial (MTM), introducing innovative features to enhance performance and address specific challenges associated with BMI applications. The motivation behind the use of the unit-cell structure is to elongate the electric path within the antenna patch, diverging from a reliance on the electrical properties of the MTM. Consequently, the unit cell is connected to an inset-fed transmission line and shorted to the ground. This configuration serves the dual purpose of reducing the size of the antenna and enabling resonance at the 2.442 GHz band within a seven-layer brain phantom. The antenna is designed using a FR-4 substrate (εr = 4.3 and tan Î´ = 0.025) of 1.5 mm thickness, and it is coated with a biocompatible polyamide material (εr = 4.3 and tan Î´ = 0.004) of 0.05 mm thickness. The proposed antenna achieves a compact dimension of 20 × 20 × 1.6 mm3 (0.338 × 0.338 × 0.027 λg3) and demonstrates a high bandwidth of 974 MHz with its gain of -14.6 dBi in the 2.442 GHz band. It also exhibits a matched impedance of 49.41-j1.32 Ω in the implantable condition, corresponding to a 50 Ω source impedance. In comparison to a selection of relevant research works, the proposed antenna has a low specific absorption rate (SAR) of 218 W/kg and 68 W/kg at 1g and 10g brain tissue standards, respectively. An antenna prototype has been fabricated and measured for return loss in both free space and in-vivo conditions using sheep's brain. The measurement results are found to be in close agreement with the simulation results for both conditions, showing the practical applicability of the proposed antenna for BMI applications.

RESUMEN

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.

Asunto(s)

RESUMEN

The proposed paper presents a flexible antenna that is capable of operating in several frequency bands, namely 2.45 GHz, 5.8 GHz, and 8 GHz. The first two frequency bands are frequently utilized in industrial, scientific, and medical (ISM) as well as wireless local area network (WLAN) applications, whereas the third frequency band is associated with X-band applications. The antenna, with dimensions of 52 mm × 40 mm (0.79 λ × 0.61 λ), was designed using a 1.8 mm thick flexible kapton polyimide substrate with a permittivity of 3.5. Using CST Studio Suite, full-wave electromagnetic simulations were conducted, and the proposed design achieved a reflection coefficient below -10 dB for the intended frequency bands. Additionally, the proposed antenna achieves an efficiency value of up to 83% and appropriate values of gain in the desired frequency bands. In order to quantify the specific absorption rate (SAR), simulations were conducted by mounting the proposed antenna on a three-layered phantom. The SAR1g values recorded for the frequency bands of 2.45 GHz, 5.8 GHz, and 8 GHz were 0.34, 1.45, and 1.57 W/Kg respectively. These SAR values were observed to be significantly lower than the 1.6 W/Kg threshold set by the Federal Communication Commission (FCC). Moreover, the performance of the antenna was evaluated by simulating various deformation tests.

RESUMEN

Efficiently managing coexistence is crucial for achieving high-quality wireless communication in the Industrial, Scientific, and Medical (ISM) band where multiple wireless communication systems operate. Coexistence problems between Wi-Fi and Bluetooth Low Energy (BLE) signals are especially significant due to their shared frequency band, which often leads to interference and a reduced performance for both systems. Therefore, effective coexistence management strategies are essential for ensuring the optimal performance of Wi-Fi and Bluetooth signals in the ISM band. In this paper, the authors conducted a study to investigate coexistence management in the ISM band by evaluating four frequency hopping techniques: random, chaotic, adaptive, and an optimized chaotic technique proposed by the authors. The optimized chaotic technique aimed to minimize interference and ensure zero self-interference among hopping BLE nodes by optimizing the update coefficient. Simulations were conducted in an environment with existing Wi-Fi signal interference and interfering Bluetooth nodes. The authors compared several performance metrics, including the total interference rate, total successful connection rate, and trial execution time for channel selection processing time. The results indicated that the proposed optimized chaotic frequency hopping technique achieved a better balance between reducing interference with Wi-Fi signals, achieving a high success rate for connecting BLE nodes, and requiring minimal trial execution time. This makes it a suitable technique for managing interference in wireless communication systems. While the proposed technique had a higher interference than the adaptive technique for small numbers of BLE nodes, for larger numbers of nodes it had a much lower interference than the adaptive technique. The proposed optimized chaotic frequency hopping technique provides a promising solution for effectively managing coexistence in the ISM band, particularly between Wi-Fi and BLE signals. It has the potential to improve the performance and quality of wireless communication systems.

RESUMEN

Advances in wearable device technology pave the way for wireless health monitoring for medical and non-medical applications. In this work, we present a wearable heart rate monitoring platform communicating in the sub-6GHz 5G ISM band. The proposed device is composed of an Aluminium Nitride (AlN) piezoelectric sensor, a patch antenna, and a custom printed circuit board (PCB) for data acquisition and transmission. The experimental results show that the presented system can acquire heart rate together with diastolic and systolic duration, which are related to heart relaxation and contraction, respectively, from the posterior tibial artery. The overall system dimension is 20 mm by 40 mm, and the total weight is 20 g, making this device suitable for daily utilization. Furthermore, the system allows the simultaneous monitoring of multiple subjects, or a single patient from multiple body locations by using only one reader. The promising results demonstrate that the proposed system is applicable to the Internet of Healthcare Things (IoHT), and particularly Integrated Clinical Environment (ICE) applications.

RESUMEN

Due to the rapid development of Internet of Things (IoT) systems operating in industrial, scientific and medical (ISM) frequency bands, many researchers have attempted to determine the amount of interference that can be expected in such systems. The basic information required for this purpose is the current occupancy of frequency channels in various geographical locations. It is known that the occupancy measurement must last long enough to allow for the detection of low duty cycle transmissions. In this paper, it is shown that fulfilling only this criterion may lead to unreliable results being obtained. In two measurement campaigns performed in two different locations, the occupancy of a selected sub-band in the 868 MHz ISM band was determined on the basis of two hour-long observations repeated several times a day. During a typical day, the ratio of the maximum and the minimum result depended on the location and reached a value of eight; however, on one day, a period of abnormally high channel usage reaching 65% was observed in the location in which typical values did not exceed 1%.

RESUMEN

This article presents a compact size circularly polarized substrate integrated waveguide (SIW) based wideband antenna array that serves industrial, scientific, and medical (ISM) band applications. A coplanar waveguide (CPW) technique is used to ensure the antenna size compactness. The proposed antenna is fabricated on a low-profile Rogers RT6002 substrate with a dielectric constant of 2.94, tanδ of 0.0012 and an approximate height of 0.76mm. The proposed design covers the frequency range from 2.15 GHz to 3.63 GHz (60.4%) while the axial ratio has a 3 dB bandwidth covering from 2.19 GHz to 2.51 GHz (13%) at the operating band of 2.45 GHz. The antenna is miniaturized and has a size of about 46.50 × 29 × 0.76 mm3. The simulation and experimental results are taken into consideration and there is a good promise between them. Hence, the antenna is a suitable applicant to be utilized for the applications in the ISM band.

RESUMEN

The rapid development of Internet of Things (IoT) has led to more and more devices using ISM frequency bands. Because they are not time synchronized, medium access collisions are unavoidable. The probability of such a collision is usually reasonably low; however, it increases with the number of transmitters competing for the same frequency channel. For this reason, ISM bands' occupancy is regularly monitored by researchers. This paper presents the results of the measurement campaign during which a selected part of the 868 MHz ISM frequency band was monitored for the presence of transmissions in six locations in various residential areas in Warsaw, Poland. For the purpose of the campaign, a dedicated measurement set-up comprising a software-defined radio (SDR) module was assembled. The measurements results showed that the channel occupancy is in most cases lower than 1% with a maximum observed value of 2%. The paper presents selected characteristics of the detected signals. Additionally, distribution over time of the detected signals was used together with the Monte Carlo simulations to analyze how long idle time blocks are available for new transmitters that could be deployed in the band under testing.

RESUMEN

A simple dual-band patch antenna with paired L-shap slots for on- and off-body communications has been presented in this article. The proposed antenna resonates in the industrial, scientific, and medical (ISM) band at two different frequencies, at 2.45 GHz and 5.8 GHz. At the lower frequency band, the antenna's radiation pattern is broadsided directional, whereas it is omni-directional at the higher frequency band. The efficiency and performance of the proposed antenna under the influence of the physical body are improved, and the specific absorption rate (SAR) value is significantly reduced by creating a full ground plane behind the substrate. The substrate's material is FR-4, the thickness of which is 1.6 mm and it has a loss tangent of tanδ = 0.02. The overall size of the proposed design is 40 mm × 30 mm × 1.6 mm. Physical phantoms, such as skin, fat and muscle, are used to evaluate the impact of physical layers at 2.45 GHz and 5.8 GHz. The SAR values are assessed and found to be 0.19 W/kg and 1.18 W/kg at 2.45 GHz and 5.8 GHz, respectively, over 1 gram of mass tissue. The acquired results indicate that this antenna can be used for future on- and off-body communications and wireless services.

Asunto(s)

RESUMEN

A textile patch antenna is an attractive package for wearable applications as it offers flexibility, less weight, easy integration into the garment and better comfort to the wearer. When it comes to wearability, above all, comfort comes ahead of the rest of the properties. The air permeability and the water vapor permeability of textiles are linked to the thermophysiological comfort of the wearer as they help to improve the breathability of textiles. This paper includes the construction of a breathable textile rectangular ring microstrip patch antenna with improved water vapor permeability. A selection of high air permeable conductive fabrics and 3-dimensional knitted spacer dielectric substrates was made to ensure better water vapor permeability of the breathable textile rectangular ring microstrip patch antenna. To further improve the water vapor permeability of the breathable textile rectangular ring microstrip patch antenna, a novel approach of inserting a large number of small-sized holes of 1 mm diameter in the conductive layers (the patch and the ground plane) of the antenna was adopted. Besides this, the insertion of a large number of small-sized holes improved the flexibility of the rectangular ring microstrip patch antenna. The result was a breathable perforated (with small-sized holes) textile rectangular ring microstrip patch antenna with the water vapor permeability as high as 5296.70 g/m2 per day, an air permeability as high as 510 mm/s, and with radiation gains being 4.2 dBi and 5.4 dBi in the E-plane and H-plane, respectively. The antenna was designed to resonate for the Industrial, Scientific and Medical band at a specific 2.45 GHz frequency.

Asunto(s)

RESUMEN

Surface acoustic wave (SAW) resonators are low cost devices that can operate wirelessly on a received radio frequency (RF) signal with no requirement for an additional power source. Multiple SAW resonators operating as transponders that form a wireless sensor network (WSN), often need to operate at tightly spaced, different frequencies inside the industrial, scientific and medical (ISM) bands. This requires nanometer precision in the design and fabrication processes. Here, we present results demonstrating a reliable and repeatable fabrication process that yields at least four arrays on a single 4-inch wafer. Each array consists of four single-port resonators with center frequencies allocated inside four different sub-bands that have less than 50 kHz bandwidth and quality factors exceeding 8000. We see promise of standard, low-cost photolithography techniques being used to fabricate multiple SAW resonators with different center resonances all inside the 433.05 MHz-434.79 MHz ISM band and a mere 100 kHz spacing. We achieved that by leveraging the intrinsic process variation of photolithography and the impact of the metallization ratio and metal thickness in rendering distinct resonant frequencies.

RESUMEN

Due to the development of modern wearable mobile devices, the need of antenna with smaller size and internally flexible to fit becomes necessary. Miniaturization of Micro Strip Patch (MSP) antenna increases its employability for communication in different aspects. The use of flexible material for the fabrication of MSP antenna still improves its use for Wireless Body Area Networks (WBAN) which includes devices for monitoring systems in military, surveillance and medical applications. The devices designed specifically in Industrial Scientific Medical (ISM) band are used for communication in these applications. Defected Ground Structure (DGS) is adopted as an emerging technique for improving the various parameters of microwave circuits, that is, narrow bandwidth, cross-polarization, low gain, and so forth. In this paper, the design of compact micro strip patch antenna using different flexible substrate materials with DGS is proposed to resonate the antenna at 2.45GHz ISM band which can be used as biomedical sensors. Felt and Teflon with dielectric constant 1.36 and 2.1respectively are chosen as flexible substrate material among various flexible materials like cotton, rubber, paper, jeans etc. Using CST studio suite software, the designed antenna is simulated and the fabricated antenna is tested with Vector Network Analyzer (VNA). The performance parameters like return loss, gain, directivity and Voltage Standing Wave Ratio (VSWR) of the antenna are analyzed.

Asunto(s)

RESUMEN

In the field of medicinal applications, early / (Timely) detection of Breast cancer is a key diagnosing process which provides effective medical treatment and also reduces women mortality. Due to the advancement and growth of medical sciences, efficient antennas are needed for imaging, diagnosing and providing superior treatment to the patients. Since tumor is tiny in size at the early stage, the knowledge of its precise location is chiefly required. For this purpose several antennas with high accuracy are designed. Among them, Flexible antenna has several advantages compared to other antennas. The main advantage of flexible antenna is its simple construction, high gain and cost-efficiency. The proposed research work implements a novel flexible antenna for detection of early breast cancer, with and without tumor application. In the study, (for the sake of comprehensive analysis and accuracy / familiarity / simplicity), Jean material is used as dielectric substrate with dielectric constant 1.7. The flexible antennas are designed with a slot loaded over the patch and with ground plane that are made up of copper as the conducting material. The jeans cloth material with 1 mm thickness is considered as a substrate, which is to be placed on the breast surface. Co-axial feeding method is chosen for the proposed antenna which improves the antenna performance. In addition to this, the antenna is a wearable textile type designed for ISM (Industrial, Scientific and Medical) band 2.4 GHz applications. The antenna is simulated using HFSS (High Frequency Structure Spectrum) software. From the simulation analysis, Return loss (S11), Gain in dB, Radiation pattern, axial ratio (AR) and VSWR are obtained and analyzed. Finally, the simulation results are compared with the existing methodologies.

Asunto(s)

RESUMEN

This paper investigates micromachined antenna performance operating at 5 GHz for radio frequency (RF) energy harvesting applications by comparing different substrate materials and fabrication modes. The research aims to discover appropriate antenna designs that can be integrated with the rectifier circuit and fabricated in a CMOS (Complementary Metal-Oxide Semiconductor)-compatible process approach. Therefore, the investigation involves the comparison of three different micromachined antenna substrate materials, including micromachined Si surface, micromachined Si bulk with air gaps, and micromachined glass-surface antenna, as well as conventional RT/Duroid-5880 (Rogers Corp., Chandler, AZ, USA)-based antenna as the reference. The characteristics of the antennas have been analysed using CST-MWS (CST MICROWAVE STUDIO®-High Frequency EM Simulation Tool). The results show that the Si-surface micromachined antenna does not meet the parameter requirement for RF antenna specification. However, by creating an air gap on the Si substrate using a micro-electromechanical system (MEMS) process, the antenna performance could be improved. On the other hand, the glass-based antenna presents a good S11 parameter, wide bandwidth, VSWR (Voltage Standing Wave Ratio) ≤ 2, omnidirectional radiation pattern and acceptable maximum gain of >5 dB. The measurement results on the fabricated glass-based antenna show good agreement with the simulation results. The study on the alternative antenna substrates and structures is especially useful for the development of integrated patch antennas for RF energy harvesting systems.

RESUMEN

Energy Harvesting techniques are increasingly seen as the solution for freeing the wireless sensor nodes from their battery dependency. However, it remains evident that network performance features, such as network size, packet length, and duty cycle, are influenced by the sum of recovered energy. This paper proposes a new approach to defining the specifications of a stand-alone wireless node based on a Radio-frequency Energy Harvesting System (REHS). To achieve adequate performance regarding the range of the Wireless Sensor Network (WSN), techniques for minimizing the energy consumed by the sensor node are combined with methods for optimizing the performance of the REHS. For more rigor in the design of the autonomous node, a comprehensive energy model of the node in a wireless network is established. For an equitable distribution of network charges between the different nodes that compose it, the Low-Energy Adaptive Clustering Hierarchy (LEACH) protocol is used for this purpose. The model considers five energy-consumption sources, most of which are ignored in recently used models. By using the hardware parameters of commercial off-the-shelf components (Mica2 Motes and CC2520 of Texas Instruments), the energy requirement of a sensor node is quantified. A miniature REHS based on a judicious choice of rectifying diodes is then designed and developed to achieve optimal performance in the Industrial Scientific and Medical (ISM) band centralized at 2.45 GHz . Due to the mismatch between the REHS and the antenna, a band pass filter is designed to reduce reflection losses. A gradient method search is used to optimize the output characteristics of the adapted REHS. At 1 mW of input RF power, the REHS provides an output DC power of 0.57 mW and a comparison with the energy requirement of the node allows the Base Station (BS) to be located at 310 m from the wireless nodes when the Wireless Sensor Network (WSN) has 100 nodes evenly spread over an area of 300 × 300 m 2 and when each round lasts 10 min . The result shows that the range of the autonomous WSN increases when the controlled physical phenomenon varies very slowly. Having taken into account all the dissipation sources coexisting in a sensor node and using actual measurements of an REHS, this work provides the guidelines for the design of autonomous nodes based on REHS.

RESUMEN

Internet of Things (IoT) technology is rapidly emerging in medical applications as it offers the possibility of lower-cost personalized healthcare monitoring. At the present time, the 2.45 GHz band is in widespread use for these applications but in this paper, the authors investigate the potential of the 915 MHz ISM band in implementing future, wearable IoT devices. The target sensor is a wrist-worn wireless heart rate and arterial oxygen saturation (SpO2) monitor with the goal of providing efficient wireless functionality and long battery lifetime using a commercial Sub-GHz low-power radio transceiver. A detailed analysis of current consumption for various wireless protocols is also presented and analyzed. A novel 915 MHz antenna design of compact size is reported that has good resilience to detuning by the human body. The antenna also incorporates a matching network to meet the challenging bandwidth requirements and is fabricated using standard, low-cost FR-4 material. Full-Wave EM simulations are presented for the antenna placed in both free-space and on-body cases. A prototype antenna is demonstrated and has dimensions of 44 mm × 28 mm × 1.6 mm. The measured results at 915 MHz show a 10 dB return loss bandwidth of 55 MHz, a peak realized gain of - 2.37 dBi in free-space and - 6.1 dBi on-body. The paper concludes by highlighting the potential benefits of 915 MHz operation for future IoT devices.