Body-centric Wireless Communications Research Articles

High gain multi-band circularly polarized wearable leaky wave zipper MIMO antenna

A miniaturized, multi-band, four-port wearable Multiple Input Multiple Output (MIMO) antenna is proposed, which contains a leaky wave textile antenna (LWTA) on denim (εr = 1.6, tanδ = 0.006) as substrate and Shieldit Super Fabric as conductor textile. The concept in this work involves incorporating the metal and plastic zipper into the garment to function as an antenna worn on the body. Simulations and measurements have been conducted to explore this idea. The LWTA has dimensions of 40 × 30 × 1 mm³. Every two ports are separated by a zipper with two different kinds of materials: Acetal Polymer Plastic (APP) and 90 % brass to improve the isolation, gain, and Impedance bandwidth. The antenna operates in the frequency ranges covering the L, C, S, and X bands. Additionally, diversity performance is evaluated using the Envelope Correlation Coefficient (ECC) and diversity gain (DG). Simulation and measurement findings agree well, with a maximum gain of 12.15 dBi, low Specific Absorption Rate (SAR) based on the standards, DG greater than 9.65 dB, circular polarization (CP), and strong isolation (<-23 dB) between each port. Since the antenna's characteristics do not change significantly under bending and when the zipper is opened, the proposed antenna is a viable candidate for body-centric wireless communications on the battlefield. For example, it can facilitate communication covering wireless local area network (WLAN) and fifth-generation (5G) communications.

Optically control tissue-independent reconfigurable antenna for body-centric communications at 2.4 GHz ISM band

The objective of this article is to design a tissue-independent reconfigurable antenna that operates at the Industrial, Scientific, and Medical band (ISM band: 2.4 − 2.485 GHz) for body-centric wireless communications. The primary radiator of the proposed antenna consists of three concentric split-ring resonators (SRRs) and a photodiode appropriately placed between the rings. In addition, a hook-shaped slot in the ground plane, and a shorting pin between the radiator and the ground plane are employed to improve the impedance matching and adjust the resonance frequency, respectively. The optically controlled implantable antenna (OCIA) with the novel configuration operates in the respective frequency band in the skin and muscle tissue in the OFF state and the fat tissue in the ON state of the diode. The numerical design and analysis of the OCIA were carried out using CST Microwave Studio and the obtained results were verified by the in-vivo, ex-vivo, and in-vitro measurements of the fabricated antenna. To the best of the authors' knowledge, this is the first optically reconfigurable antenna capable of covering the 2.4 GHz ISM band within three different body tissues.

A symmetric T-H shape wideband negative index metamaterial for 28-GHz millimeter-wave applications

One of the leading candidates for the next fifth generation of (5G) and body-centric wireless communications is millimeter-wave frequencies. In this study, a wideband tunable metamaterial (MTM) consisting of T-H shaped symmetric resonator is presented for body-centric applications operating in the millimeter-wave frequency band centered at 28 GHz. The characteristics of the proposed MTM are examined through wave propagation in both Z and X directions. It has a wide operating frequency range of 5.6 GHz for waves travelling along the Z-axis, with DNG characteristics at 26.2 GHz resonance frequency. However, it represents a negative epsilon metamaterial (ENG) range during X-axis wave propagation in the 25–29.4 GHz frequency range. The metamaterial is constructed on a Rogers (RT-5880) substrate and has a compact size, with overall dimensions of 0.420 λo × 0.420 λo. A proposed Y-shaped antenna is developed with a compact size of 1.36 λo × 1.82 λoto cover the 5G at 28 GHz. The single-Y-shaped antenna consists of aradiating patch, Rogers substrate, full ground plane, air bandgap (ABG), and array of DNG MTM.Thus, the array of MTM has been applied to validate the effect in the overall antenna performance such as gain which has been increased from 5.5 dBi to 8.5 dBi. The experimental, simulated results, and equivalent circuit model using Advanced Design Software (ADS) for validation functions showed that the completed results are comparable. The proposed mm-wave metamaterial is expected to be a good candidate for modern 5G wireless communication system components, especially to enhance the antenna gain and isolation. The proposed antenna loaded with MTM is a suitable contender for the upcoming 5G mm wave mobile handheld devices.

A Conformal Tri-Band Antenna for Flexible Devices and Body-Centric Wireless Communications.

A conformal tri-band antenna tailored for flexible devices and body-centric wireless communications operating at the key frequency bands is proposed. The antenna is printed on a thin Rogers RT 5880 substrate, merely 0.254 mm thick, with an overall geometrical dimension of 15 × 20 × 0.254 mm3. This inventive design features a truncated corner monopole accompanied by branched stubs fed by a coplanar waveguide. The stubs, varying in length, serve as quarter-wavelength monopoles, facilitating multi-band functionality at 2.45, 3.5, and 5.8 GHz. Given the antenna's intended applications in flexible devices and body-centric networks, the conformability of the proposed design is investigated. Furthermore, an in-depth analysis of the Specific Absorption Rate (SAR) is conducted using a four-layered human tissue model. Notably, the SAR values for the proposed geometry at 2.45, 3.5, and 5.8 GHz stand at 1.48, 1.26, and 1.1 W/kg for 1 g of tissue, and 1.52, 1.41, and 0.62 W/kg for 10 g of tissue, respectively. Remarkably, these values comfortably adhere to both FCC and European Union standards, as they remain substantially beneath the threshold values of 1.6 W/kg and 2 W/kg for 1 g and 10 g tissues, respectively. The radiation characteristics and performance of the antenna in flat and different bending configurations validate the suitability of the antenna for flexible devices and body-centric wireless communications.

Wearable coupled-quarter-mode SIW antenna platform with hybrid kinetic and ambient-light energy harvesting

As key enablers for smart fabric interactive textile (SFIT) systems, textile antenna systems and platforms need to be energy-efficient, low-profile and should guarantee a stable wireless body-centric communication link. Using multiple energy harvesters on and in the antenna platform is highly recommended to enable autonomous SFIT systems. Different sensors could be added to the system for monitoring the environmental and/or biophysical parameters of rescue workers, military personnel, and other safety workers. Therefore, a wearable coupled-quarter-mode (coupled-QM) substrate-integrated waveguide (SIW) antenna with optimally, seamlessly integrated hybrid kinetic and ambient-light energy harvesters is proposed. Two QM cavities are coupled via a non-resonant slot to create a compact antenna covering the [2.4; 2.4835] GHz Industrial, Scientific and Medical (ISM) band. The antenna platform fully consists of textile materials, being protective rubber foam and copper taffeta, enabling its unobtrusive integration into protective clothing. A novel, compact way of deploying a kinetic energy harvester inside the substrate, combined with flexible power management electronics on the antenna feed plane and a flexible ambient-light photovoltaic cell on the antenna plane, is proposed. The integrated antenna platform exhibits a measured impedance bandwidth of 307 MHz, a radiation efficiency of 88.57% and maximum gain of 3.74 dBi at 2.45 GHz. Wearing the antenna platform around a person’s wrist resulted in an average harvested power of 229.8 µW when walking in an illuminated room.

Elastomeric Textile Substrates to Design a Compact, Low-Profile AMC-Based Antenna for Medical and IoT Applications

A neoteric, compact, low-profile, wide-band elastomeric textile antenna for medical and IoT applications is presented. The design synthesis of flexible artificial magnetic conductor (AMC)-integrated antenna is done using stratum of textile and operates within 4.76–6.08 GHz covering the 5.8-GHz industrial, scientific, medical (ISM) and 5-GHz Wi-Fi band for IoT applications. The rectangular fed design operates in the high frequency band which is widened and optimized to operate in the lower 5-GHz band and the notch etched with the monopole’s edges, suppress the cross-polarization component. The suggested design features an impedance bandwidth of 24.4% with a high gain of 10.59 dBi and has a compact footprint of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.44\lambda _{0}\times $ </tex-math></inline-formula> 0.46 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}\times $ </tex-math></inline-formula> 0.0512 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> . Simulation and experimental studies provide evidence that in the case of structural deformities, such as bending and crumpling and also for human body loading, the suggested AMC-integrated antenna is stable and shows superior efficiency relative to the traditional monopole antenna. Thus, to a large extent, the antenna is stable to maintain its radiation properties. Furthermore, numerical analysis demonstrates maximum amount of the specific absorption rate (SAR) is 0.0832 W/Kg according to IEEE standard safety guidelines. The advantage of the suggested AMC-integrated antenna design is that it is resilient to moisture conditions and the enhancement in impedance bandwidth is achieved by simple cut edges in the radiator and the ground plane leading to a simple staircase design. In addition, the simulation and measurement results are consistent, thus confirming it to be a promising contender for sensing and applications in body-centric wireless communications and Internet of Things.

Different Power Adaptive Transmission Schemes Over Alternate Rician Shadowed Fading Channels

The two-sided bimodality property of Alternate Rician Shadowed (ARS) fading channels makes it a suitable fading model for body-centric wireless communication. The ARS fading model consists of two fluctuating specular components in which only one is active at a time. To provide excellent spectral efficiency with higher quality of service, system transmitter employs an adaptive transmission scheme. This paper derives the exact closed-form expressions of the ARS fading channels capacity. Various adaptive transmission schemes such as channel inversion with a fixed-rate, truncated channel inversion with a fixed-rate, and optimal rate adaptation are considered. A comparison of these schemes is also highlighted. Performance expressions such as binary bit error rate for various coherent and non-coherent modulation schemes and the outage probability are also derived. The derived results are plotted and analyzed for varying fading parameters of the ARS channel. Finally, the results of all performance metrics are verified with Monte-Carlo simulation results.

A compact dual-sense circularly polarized SIW textile antenna for body-centric wireless communication

In this communication, a dual-sense circularly polarized textile antenna that operates at the centre frequency of 5.8 GHz is presented for body-centric wireless communication. The proposed textile antenna is realized using a substrate integrated waveguide (SIW) cavity. Circular polarization is achieved by exciting two orthogonal quarter mode apertures in 900 phase differences. A metallic via is employed to control the magnetic field coupling between the two orthogonal quarter mode apertures. The feed point and dimensions of two-quarter mode apertures can be changed to realize both left-hand and right-hand circular polarization. The proposed textile antenna has a 4.8 % impedance bandwidth covering from 5.62 to 5.90 GHz. Moreover, the textile antenna has a 2.9 % 3 dB axial ratio bandwidth covering from 5.725 to 5.875 GHz frequency bandwidth. The textile antenna has exhibited good reflection characteristics when bent on the surface of a cylindrical structure. The textile antenna has a lesser than 1.27 W/Kg SAR value in the proximity of the human phantom model for a 1 W source and also has exhibited a minimum peak gain of 5 dBi, making it conducive for integration with body-centric wireless communication.

92 Mb/s Fat-Intrabody Communication (Fat-IBC) With Low-Cost WLAN Hardware.

The human subcutaneous fat layer, skin and muscle together act as a waveguide for microwave transmissions and provide a low-loss communication medium for implantable and wearable body area networks (BAN). In this work, fat-intrabody communication (Fat-IBC) as a human body-centric wireless communication link is explored. To reach a target 64 Mb/s inbody communication, wireless LAN in the 2.4 GHz band was tested using low-cost Raspberry Pi single-board computers. The link was characterized using scattering parameters, bit error rate (BER) for different modulation schemes, and IEEE 802.11n wireless communication using inbody (implanted) and onbody (on the skin) antenna combinations. The human body was emulated by phantoms of different lengths. All measurements were done in a shielded chamber to isolate the phantoms from external interference and to suppress unwanted transmission paths. The BER measurements show that, except when using dual on-body antennas with longer phantoms, the Fat-IBC link is very linear and can handle modulations as complex as 512-QAM without any significant degradation of the BER. For all antenna combinations and phantoms lengths, link speeds of 92 Mb/s were achieved using 40 MHz bandwidth provided by the IEEE 802.11n standard in the 2.4 GHz band. This speed is most likely limited by the used radio circuits, not the Fat-IBC link. The results show that Fat-IBC, using low-cost off-the-shelf hardware and established IEEE 802.11 wireless communication, can achieve high-speed data communication within the body. The obtained data rate is among the fastest measured with intrabody communication.

Design of pattern-reconfigurable circularly polarized unidirectional antenna based on quasi-radiator for ISM applications

A pattern-reconfigurable circularly polarized antenna for 2.45 GHz industrial, scientific, and medical (ISM) band applications is designed in this work. The proposed antenna consists of a slotted-stepped monopole connected to a rectangular ground plane via a shorting side-stub. This converts the omnidirectional radiation pattern of the antenna into stable unidirectional radiation. To dynamically steer the realized pattern, two switchable RF PIN diodes are jointly incorporated into the side-stubs to achieve symmetrical radiations in specific operating modes. In this way, the radiation patterns can be simultaneously tuned in the ±y directions by the simple switching of the PIN diodes ON and OFF. The fabricated prototype achieves an S11 smaller than -10dB within the 3dB axial ratio (AR) bandwidth with stable far-field patterns. The antenna maintains a low-profile and compact size of 0.055λ02 which makes it suitable for body-centric wireless communication (BWC) and personal wireless area networks.

Bending Assessment and On-body Investigation of a Textile Antenna for Body-Centric Wireless Communication Applications

This article presents the design and investigation of a textile-based antenna for body wireless communication applications. The Christmas tree structure inspired the antenna design, and a staircase-like defective ground element supported it. The antenna is tiny with a footprint of 30×20×1 mm3 and is developed on polyester fabric. This material has good grades of flexibility and has the most negligible affinity to moisture, so it was chosen as a suitable substrate for the developed wearable antenna. The radiating elements and grounds conductivity is actualised using the adhesive conductive copper tape. The propounded antenna operates in a treble band of Telemetry, Industrial Scientific and Medical (ISM), and X-band at 4.5, 5.8, and 8 GHz frequencies. The developed textile antenna is intended for body applications, so it was methodically examined by bending it at various vertical and horizontal bending angles. This analysis shows that the antenna’s resonating frequencies are not substantially varied in the vertical and horizontal bending aspects. The antennas on body performance were also examined by placing the prototype directly on the subject’s skin. These results confirm the developed antennas’ applicability for body wireless communication applications.

Design of Metamaterial Zipper Antenna for Boby-Centric Wireless Communication

The concept of making metamaterial zipper antenna to serve as an off- body antenna is proposed and the stimulations are carried out. The feeding point is located at the bottom and in order to be more specific it is around one of the variation and reflection coefficient as well as radiation pattern or brought by excitation at certain tooth of zipper. The radiation pattern is reconfigurable to some extent. A fractional bandwidth of 4.80 percent at 2.48 GHz of industrial, scientific and medical band with a gain of about 5dBi has been achieved. The stimulation result indicate reasonable agreement to that of stimulation in both matching performance and the radiation feature of metamaterial zipper antenna, which makes the antenna more promising candidate for body centric wireless communication device .

Design and characterization substrate integrated waveguide antenna for WBANS application

Millimetre-wave frequencies are defined as one of the front-runner contenders for body-centric wireless communication. In this study, low-profile antenna with the substrate integrated waveguide (SIW) has been proposed that operate in the band of the millimetre-wave frequency that has been centred at 60 GHz. The proposed antenna has been implemented with the use of the FR4 substrate with εr and tangent loss of 4.3 and 0.025, respectively. The substrate height and size are 1.5875 mm and 20 mm x 20 mm, respectively. The performance of the antenna is evaluated in off-body (free space) and on-body (human voxel model), through simulation. The proposed antenna has an ultra-wideband (UWB) and a specific absorption rate the maximal (SAR) for (10 g) is 0.0344815 W/kg and for (1 g) is 0.0184723 W/kg. It achieves 74% and 63% efficiency in the off and on-body scenario, respectively. The small antenna with the exceptional matching of impedance, low SAR, broad bandwidth, and good efficiency, a good voltage standing wave ratio good (VSWR), and good front-to-back ratio (FBR). As a result, its characteristics make it one of the best potential candidates for the simultaneous transmission and reception of data at (mm-wave) band for WBAN applications.

Novel Compact Design and Investigation of a Super Wideband Millimeter Wave Antenna for Body-Centric Communications

This paper presents a novel design for a multiple band millimeter wave antenna with a wide active region in the extremely high frequency (EHF) range. The antenna's performance was tested at three evenly separated frequencies: 60 GHz within the V-band region, 80 GHz within the E-band region, and 100 GHz. Simulation exhibits satisfactory results in terms of gain and efficiency, although the efficiency falling tendency for higher frequency persists. As millimeter wave antennas have miniature-like dimensions and low penetration depth into human body layers, the performance of these antennas is less disturbed by the presence of a human body, making them ideal for body-centric wireless communication (BCWC) applications. Thus, a human body model was created virtually with the necessary property data. Simulations are repeated at the same frequencies as before, with the antenna kept close to the constructed human body model. The results were promising as the gains found increased radiation patterns and return loss curves remained almost identical, except some efficiencies that were considered. Some H-plane radiation patterns are changed by the presence of a human body. Although all three frequencies present satisfactory results, 60 GHz is found to be more balanced, but 100 GHz shows better gain and directivity. Multiple band operability makes this antenna suitable for various applications. Finally, a distance-based analysis was conducted to realize the in-depth characteristics of the antenna by placing the antenna at five different gaps from the human body. The result verifies the antenna’s category as suitable for body-centric communications.

Design of Embroidery Antenna for Wearable Applications

The rapid growth of wearable devices has augmented the requirement for body centric wireless communication. In addition to this, to reduce the size of the device and its power consumption, it is also significant to develop a flexible antenna’s that may be incorporated for wearable applications. This paper presents the primary development of the wearable embroidery textile antenna for the wireless body area networks. The operating centre frequency ( fc ) of this wearable embroidery textile antenna is 2.40 GHz. Textile materials are used as the substrates as it has low relative permittivity and dielectric constant. A strip lines made up of conductive materials is used as radiating element. The nylon material used as a substrate material with a relative permittivity of 1.7 .The size of the antenna is very thin .The properties were analyzed for the proposed antenna.

A Compact Microstrip Wearable Dual-Band Antenna

Body-centric communication systems are said to be one of the most emerging areas in wireless communication. It has a major impact in areas like, health monitoring; position monitoring, real-time video feed networks, which makes body-centric wireless communication one of the most attractive research areas. However, having the human body in the network, the system becomes more complex. Each element of the system demands special attention in the designing and implementation process. The main purpose of this work is to design the dual-band (2.95 GHz and 5.7 GHz) micro-strip wearable antenna. The proposed design is a combination of rectangular and F-shaped configuration designed on the FR4 Epoxy dielectric substrate of 1.6 mm thickness, the relative permittivity of 4.4, and dielectric loss tangent of 0.02. The antenna design is simulated and analyzed to get low return loss, high gain, and low VSWR. One of the significant features of the designed wearable antenna is its compact size. The size of the substrate is reduced to 35*35mm. When it is compared with the existing design, it was found that the proposed design has a reduced size of the substrate. The CST microwave studio software is used as a tool for simulation. The human phantom model has to be introduced in the future to design and check the effect of electromagnetic radiation on the human body using SAR standard.

Comparative Design and Study of A 60 GHz Antenna for Body-Centric Wireless Communications

Comparative Design and Study of A 60 GHz Antenna for Body-Centric Wireless Communications

DGS-based wideband MIMO antenna for on–off body communication with port isolation enhancement operating at 2.45 GHz industrial scientific and medical band

A wide band, dual radiator Multiple input multiple output (MIMO) antenna resonating at 2.4 GHz Industrial Scientific and Medical (ISM) band is designed and analysed for the body-centric wireless communication. Defected ground structure (DGS) is used to reduce the antenna size and to achieve wide bandwidth. Moreover, a decoupling slot is also etched in the ground plane to improve the port isolation. Proposed 2 × 1 array MIMO structure has occupied the volume of 90 × 40 × 0.8 mm3. Rectangular and cylindrical shaped multi-layered tissue models are used for simulation and pork tissue is used for the measurement of antenna performance. Broad 10-dB bandwidth of 1250/900 MHz, port isolation of 21/20 dB, gain of 5.53/5.07 dBi with, SAR value of 0.628/0.627 W/kg is achieved for the flat/deformed state of antenna. Results show that the proposed DGS-based antenna is reliable to operate on different tissue environment for body area network.

Wearable Tri-Band Antenna for Switching Between WLAN and Bluetooth for Body Centric Wireless Communication

This paper presents a novel, flexible, and compact tri-band switchable antenna for body-centric wireless communication. The proposed antenna possesses the capability to switch between Bluetooth and WLAN frequency band by utilizing a single switch without affecting other operating passbands. The antenna is designed on a flexible substrate having an optimized size of 50 × 55 mm2. The proposed antenna design demonstrates advantageous radiation patterns with S11 < − 10 dB in passbands of both states. Moreover, measured and simulated results in both states exhibit good agreement. Based on the developed results, this antenna proves to be an appropriate choice for various wireless applications including WLAN, Bluetooth, WiMAX, and X-band satellite communication systems. Moreover, it is also shown by simulations that the proposed antenna is suitable for on-body communications.

Design of UWB Band Notch Textile Antenna for Body-Centric Wireless Network with the Comparison of Five Different Textile Substrates

Designing an effective antenna on textile substrate is quite a challenging issue which needs close monitoring of antenna return loss performance, gain, radiation pattern, efficiency etc. This paper presents the basic design of Ultra Wideband (UWB) band notch textile antenna for body-centric wireless network. Moreover, Wireless Communication is a notable communication practice and the UWB body-centric wireless communication is one of the foremost attractive ones. Hence, to design the UWB textile antenna, five different substrates have been used and analyzed for better performance evaluation. Textile substrates make the antenna wearable, and therefore can be used in sport monitoring, and in different medical applications as well. Comparing the designed antenna with five different substrates, finally the antenna is proposed with 100% Polyester substrate because among the other four textile substrates, it shows better and also has the intended antenna performance.