Crumpling Effects and Specific Absorption Rates of Flexible AMC Integrated Antennas

This study presents the design of a wearable textile-based monopole antenna integrated with a flexible artificial magnetic conductor (AMC). The proposed design covers the industrial, scientific, and medical 2.45 GHz band. An AMC reflector is utilised to isolate the human body from undesired electromagnetic radiation and to improve the antenna radiation characteristics. A monopole antenna was backed with an AMC reflector and tested in free space and on human body models. The inclusion of an AMC reflector increases the front-to-back ratio and antenna gain in free space. On the human body models, the AMC antenna provides stable performance and a reduction in specific absorption rate levels compared with using the conventional monopole antenna. Moreover, the performance of the antenna with and without the AMC reflector under different crumpling conditions has been studied and presented. The effect of crumpling on reflection phase characteristics of the AMC reflector has been analysed as well

A Printed Wearable Dual-Band Antenna for Wireless Power Transfer

In this work, a dual-band printed planar antenna, operating at two ultra-high frequency bands (2.5 GHz/4.5 GHz), is proposed for wireless power transfer for wearable applications. The receiving antenna is printed on a Kapton polyimide-based flexible substrate, and the transmitting antenna is on FR-4 substrate. The receiver antenna occupies 2.1 cm2 area. Antennas were simulated using ANSYS HFSS software and the simulation results are compared with the measurement results

Semi-Deterministic Single Interaction MIMO Channel Model

In this chapter a mathematical model to characterize wireless communication channel is developed which falls into semi-deterministic channel models. This model is based on electromagnetic scattering and reflecting and fundamental physics however it has been kept simple through appropriate assumptions

Hybrid Inductive Power Transfer and Wireless Antenna System for Biomedical Implanted Devices

In this paper, we present a hybrid system consisting of a novel microstrip antenna that can be designed to resonate at various frequencies within the ultra-high frequency (UHF) band (e.g., 415 MHz, 905 MHz, and 1300 MHz), combined with a pair of high frequency (HF) coils (13.56 MHz). The system is designed to be fabricated on an FR4 substrate layer, and it provides a compact solution for simultaneous wireless power transfer (WPT) and multi-band wireless communication, to be utilized in implanted medical devices. The external antenna/coil combination (EX) will be located outside the body on the skin layer. The EX has 79.6mm-diameter. The implanted hybrid combination (IM) has 31.5mm-diameter. The antenna is designed such that by varying the position of a shorting pin the resonance frequency can be changed among three frequencies; therefore, the same design can be used for various applications. The system was designed using numerical simulation tools, and then it was fabricated and measured. The design was optimized while the performance of the system was numerically simulated at various depths inside a layered body model. Furthermore, the insertion loss (S21) and transmission efficiency (η) for both antenna and coil pairs at different depths were studied through simulation and measurements. The system provides a good solution for the combination of power transfer and multi-band data communication

Study of the Effects of Changing Physiological Conditions on Dielectric Properties of Breast Tissues

This paper addresses the changes in the physical characteristics (temperature and water/blood content) of breast tissue under different physiological conditions. We examined ex vivo specimens of breast tissue excised at the time of surgery to study the effects of physiological conditions on dielectric properties. We observed that the dielectric properties strongly depend on tissue physiological state. When the biological tissues undergo physiological changes, such as those due to disease or those induced by external changes such as variations in the environmental temperature, the microscopic processes deviate from their normal state and impact the overall dielectric properties. This suggests that microwave imaging might be used to monitor the physiological conditions of the body

Synthesis and Use of Bio-Based Dielectric Substrate for Implanted Radio Frequency Antennas

Equipped with precision sensors/antenna modules combined with integrated processing and telemetry circuitry, wireless implants that are both biocompatible and biodegradable are important devices for monitoring patient\u27s conditions and patient\u27s safety. In this article we report on the development, design, and testing of a bio-based monopole radio frequency (RF) sensor/antenna module for potential use in human health applications. The module is built on a dielectric substrate biocomposite made of 0.5:1.0 ratio of polylactic acid (PLA) to sunflower carbon substrate (SCS) produced via pyrolysis of seeds shells. Findings for the SCS include optimized reactor yields around 7.9 wt.% at 500°C, a 0.27:1.0 fixed to elemental carbon content, dielectric constant near 3.4, loss factor between 0.0 and 0.4 measured in the 1 to 6 GHz frequency range. The PLA-SCS biocomposite exhibited comparable dielectric properties to those of pure SCS, a 17% elastic modulus increase, and over 500% increase in hardness. Numerical simulation of the designed sensor/antenna module agreed fairly well with the experimental validation results. Tests of the fabricated sensor/antenna module on water, soil and muscle tissue phantom, as well as implanted inside muscle tissue phantom, via the reflection coefficient (S11) and in a communication link via the transmission coefficient (S21) confirmed use and applicability of the developed antenna

Design and evaluation of a flexible dual-band meander line monopole antenna for on- and off-body healthcare applications

The human body is an extremely challenging environment for wearable antennas due to the complex antenna-body coupling effects. In this article, a compact flexible dual-band planar meander line monopole antenna (MMA) with a truncated ground plane made of multiple layers of standard off-the-shelf materials is evaluated to validate its performance when worn by different subjects to help the designers who are shaping future complex on-/off-body wireless devices. The antenna was fabricated, and the measured results agreed well with those from the simulations. As a reference, in free-space, the antenna provided omnidirectional radiation patterns (ORP), with a wide impedance bandwidth of 1282.4 (450.5) MHz with a maximum gain of 3.03 dBi (4.85 dBi) in the lower (upper) bands. The impedance bandwidth could reach up to 688.9 MHz (500.9 MHz) and 1261.7 MHz (524.2 MHz) with the gain of 3.80 dBi (4.67 dBi) and 3.00 dBi (4.55 dBi), respectively, on the human chest and arm. The stability in results shows that this flexible antenna is sufficiently robust against the variations introduced by the human body. A maximum measured shift of 0.5 and 100 MHz in the wide impedance matching and resonance frequency was observed in both bands, respectively, while an optimal gap between the antenna and human body was maintained. This stability of the working frequency provides robustness against various conditions including bending, movement, and relatively large fabrication tolerances

High gain triple-band metamaterial-based antipodal Vivaldi MIMO antenna for 5G communications

This paper presents a miniaturized dual-polarized Multiple Input Multiple Output (MIMO) antenna with high isolation. The antenna meets the constraints of sub-6 GHz 5G and the smartphones’ X-band communications. A vertically polarized modified antipodal Vivaldi antenna and a horizontally polarized spiral antenna are designed and integrated, and then their performance is investigated. Three frequency bands of 3.8 GHz, 5.2 GHz, and 8.0 GHz are considered, and the proposed dual-polarized antenna is studied. High isolation of greater than 20 dB is obtained after integration of metamaterial elements, and without applying any other decoupling methods. The proposed triple-band metamaterial-based antenna has 1.6 GHz bandwidth (BW) (2.9 GHz–4.5 GHz), 13.5 dBi gain, and 98% radiation efficiency at 3.8 GHz. At 5.2 GHz it provides 1.2 GHz BW, 9.5 dBi gain, and 96% radiation efficiency. At 8.0 GHz it has 1 GHz BW, 6.75 dBi gain, and 92% radiation efficiency. Four antenna elements (with eight ports) were laid out orthogonally at the four corners of a mobile printed circuit board (PCB) to be utilized as a MIMO antenna for 5G communications. The performance of the MIMO antenna is examined and reported

Design and Evaluation of a Button Sensor Antenna for On-Body Monitoring Activity in Healthcare Applications

A button sensor antenna for on-body monitoring in wireless body area network (WBAN) systems is presented. Due to the close coupling between the sensor antenna and the human body, it is highly challenging to design sensor antenna devices. In this paper, a mechanically robust system is proposed that integrates a dual-band button antenna with a wireless sensor module designed on a printed circuit board (PCB). The system features a small footprint and has good radiation characteristics and efficiency. This was fabricated, and the measured and simulated results are in good agreement. The design offers a wide range of omnidirectional radiation patterns in free space, with a reflection coefficient (S11) of −29.30 (−30.97) dB, a maximum gain of 1.75 (5.65) dBi, and radiation efficiency of 71.91 (92.51)% in the lower and upper bands, respectively. S11 reaches −23.07 (−27.07) dB and −30.76 (−31.12) dB, respectively, with a gain of 2.09 (6.70) dBi and 2.16 (5.67) dBi, and radiation efficiency of 65.12 (81.63)% and 75.00 (85.00)%, when located on the body for the lower and upper bands, respectively. The performance is minimally affected by bending, movement, and fabrication tolerances. The specific absorption rate (SAR) values are below the regulatory limitations for the spatial average over 1 g (1.6 W/Kg) and 10 g of tissues (2.0 W/Kg). For both indoor and outdoor conditions, experimental results of the range tests confirm the coverage of up to 40 m

Dual-Band Wearable MIMO Antenna for WiFi Sensing Applications

Multiple input multiple output (MIMO) technology combined with orthogonal frequency division multiple access (OFDMA) is an enabling technology used in WiFi 6/6E (IEEE 802.11ax) to increase the throughput. With the addition of WiFi 6/6E and taking advantage of MIMO and OFDMA, many applications of wearable WiFi can be imagined. For example, WiFi can be used for tracking and fall detection. Wearable devices, such as those used in gaming, vital sign monitoring, and tracking, can also take advantage of wearable MIMO antennas. In this paper, a wearable small dual-band antenna is proposed that can be fabricated on felt or denim substrate. In the proposed antenna, a conductive layer is used as a reflector to improve the gain and reduce the sensitivity of the antenna performance to the body loading effects. The details of the design and its performance in a sample indoor MIMO setting are provided. The MIMO antenna is proposed for WiFi tracking and sensing applications. The performance of the MIMO antenna in an indoor setting is examined