Ieee transactions on antennas and propagation

Wearable antennas have gained much attention in recent years due to their attractive features and possibilities in enabling lightweight, flexible, low cost, and portable wireless communication and sensing. Such antennas need to be conformal when used on different parts of the human body, thus need to be implemented using flexible materials and designed in a low profile structure. Ultimately, these antennas need to be capable of operating with minimum degradation in proximity to the human body. Such requirements render the design of wearable antennas challenging, especially when considering aspects such as their size compactness, effects of structural deformation and coupling to the body, and fabrication complexity and accuracy. Despite slight variations in severity according to applications, most of these issues exist in the context of body-worn implementation. This review aims to present different challenges and issues in designing wearable antennas, their material selection, and fabrication techniques. More importantly, recent innovative methods in back radiations reduction techniques, circular polarization (CP) generation methods, dual polarization techniques, and providing additional robustness against environmental effects are first presented. This is followed by a discussion of innovative features and their respective methods in alleviating these issues recently proposed by the scientific community researching in this field.

/pdf/wearable-antennas-a-review-of-materials-structures-and-5bzxx4cp70.pdf

Wearable Antennas: A Review of Materials, Structures, and Innovative Features for Autonomous Communication and Sensing

A novel integrated antenna solution for wireless handheld devices is proposed for the existing 4G standards and upcoming 5G systems for broadband, high data rate communications. The complete antenna system is a unique combination of a multiple-input-multiple-output (MIMO) antenna system at microwave frequencies and a millimetre (mm)-wave antenna array. The MIMO antenna system consists of two reactive loaded monopoles while the mm-wave array consists of a planar 2 by four slot antennas. The integrated antenna system covers the frequency bands from 1870 to 2530 MHz for 4G standards along with the upcoming 5G mm-wave band at 28 GHz. In addition, the integrated antenna system is planar and is designed for typical smart phone devices with a standard 60 mm by 100 mm by 0.965 mm back plane. Excellent field correlation values were obtained across the 4G band while realised peak gain values of 4 and 8 dBi were, respectively, measured for the MIMO and mm-wave antenna arrays. The proposed antenna design may also be useful for other compact implementations that support 4G and 5G communications.

/pdf/compact-4g-mimo-antenna-integrated-with-a-5g-array-for-3sgngj5e48.pdf

Compact 4G MIMO antenna integrated with a 5G array for current and future mobile handsets

A textile endfire antenna operating in the 60-GHz band is proposed for wireless body area networks (BANs). The permittivity of the textile substrate has been accurately characterized, and the Yagi-Uda antenna has been fabricated using an ad hoc manufacturing process. Its performance in terms of reflection coefficient, radiation pattern, gain, and efficiency has been studied in free space and on a tissue-equivalent phantom representing the human body. It is shown that the antenna is matched in the 57-64-GHz band. Its measured on-body efficiency and maximum gain equal 48.0% and 11.9 dBi, respectively. To our best knowledge, this is the first textile antenna for on-body wireless communications reported at millimeter waves.

Wearable Endfire Textile Antenna for On-Body Communications at 60 GHz

This paper presents a metasurface-based single-layer low-profile circularly polarized (CP) antenna with the wideband operation and its multiple-input multiple-output (MIMO) configuration for fifth-generation (5G) communication systems. The antenna consists of a truncated corner patch and a metasurface (MS) of a 2 × 2 periodic square metallic plates. The distinguishing feature of this design is that all the radiating elements (radiator and MS) are printed on the single-layer of the dielectric substrate, which ensures the low-profile and low-cost features of the antenna while maintaining high gain and wideband characteristics. The wideband CP radiations are realized by exploiting surface-waves along the MS and its radiation mechanism is explained in detail. The single-layer antenna geometry has an overall compact size of 1.0λ
 0
 × 1.0λ
 0
 × 0.04λ
 0
. Simulated and measured results show that the single-layer metasurface antenna has a wide 10 dB impedance bandwidth of 23.4 % (24.5 - 31 GHz) (23.4 %) and overlapping 3-dB axial ratio bandwidth of 16.8 % (25 - 29.6 GHz). The antenna also offers stable radiation patterns with a high radiation efficiency (>95%) and a flat gain of 11 dBic. Moreover, a 4-port (2 × 2) MIMO antenna is designed using the proposed design by placing each element perpendicular to each other. Without a dedicated decoupling structure, the MIMO antenna shows an excellent diversity performance in terms of isolation between antenna elements, envelope correlation coefficient, and channel capacity loss. Most importantly, the operational bandwidth of the antenna covers the millimeter-wave (mm-wave) band (25 - 29.5 GHz) assigned for 5G communication. These features of the proposed antenna system make it a suitable candidate for 5G smart devices and sensors.

/pdf/metasurface-based-single-layer-wideband-circularly-polarized-36hrkzr7us.pdf

Metasurface-Based Single-Layer Wideband Circularly Polarized MIMO Antenna for 5G Millimeter-Wave Systems

In this paper, two different methods for fabric characterization are presented: a single frequency method and a broadband method. Felt and denim fabrics are characterized, and patch antennas are designed using these substrates to test both methods. Prototypes of the antennas on felt and denim are manufactured using conductive textile (called electrotextile) aiming to obtain fully flexible antennas. The prototypes are characterized in anechoic chamber to be compared and obtain conclusions related to the characterization methods. A new dual-band hexagonal AMC reflector combinable with antennas is also proposed to improve their performance and reduce the backward radiation to the human body. A novel broadband CPW-fed monopole antenna is designed to be combined with the AMC. The resulted prototype is characterized and compared with the performance of the CPW-fed antenna alone.

/pdf/investigation-of-flexible-textile-antennas-and-amc-zs9gjh58ez.pdf

Investigation of Flexible Textile Antennas and AMC Reflectors

This letter describes a simple beam-tilting technique for an endfire antenna using only a single-layer frequency selective surface (FSS). The proposed approach is based on placing a parasitic FSS element under the antenna to tilt the beam in the desired direction. This is achieved by using a modified uniplanar compact FSS. To demonstrate the principle, the periodic structure is applied to a Yagi–Uda antenna operating in the millimeter-wave frequency band from 28 to 31 GHz. The measured results, by integrating the proposed FSS (one layer of 3 × 5 unit cells) under the directors of the antenna, show that at 30 GHz, the main beam radiation tilts the endfire direction ( yz plane) by +23° and –29° when the FSS structure is rotated by 90°, respectively. The simplicity of this method makes it suitable for 5G communication networks.

Beam-Tilting Endfire Antenna Using a Single-Layer FSS for 5G Communication Networks

The current practice for designing antennas over artificial magnetic conductor (AMC) is time and labour intensive. A novel methodology is described for saving time and effort in designing such antennas. The proposed method is based on using conductive fabric as a radiating element. The method is validated via the design of a textile dual-band monopole antenna on AMC covering both WiFi and the 4G long term evolution (LTE) frequency bands.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/el.2015.3135

Design methodology for wearable antenna on artificial magnetic conductor using stretch conductive fabric

This letter presents a new design of tilted-beam antenna with gain enhancement based on the multilayer frequency selective surfaces (FSSs) for fifth-generation applications. A dual-sided printed FSS element with two C-shaped resonators at the top layer and a slotted circular patch at the bottom side, is proposed. The FSS element holds a size of 0.46λ × 0.46λ (at 28 GHz). A wideband Vivaldi antenna with an end-fire radiation is used to excite the elements of the FSS layers. The effects of different sizes, number, and the angular rotation of the FSS layers are employed to achieve the best antenna performance in terms of beam-tilting, realized gain, and reducing the sidelobe level (SLL). The best antenna performance is achieved when two unequal-sized FSS layers rotated to 45° and fixed under the Vivaldi. The proposed antenna is fabricated and measured. The obtained measured results show a maximum beam tilt angle of 38°, realized gain of 9 dBi, and SLL at –8 dB. The beam tilt angles are validated with the results obtained using the Snell's law in a multilayer environment and found a good agreement.

Millimeter-Wave Beam-Tilting Vivaldi Antenna With Gain Enhancement Using Multilayer FSS

In this paper, a configuration is proposed to improve the performance of CPW antennas placed over an EBG material for dual band on body antenna applications. The aim was to improve the performance of such type of antennas by varying the position of the EBG with respect to the antenna. Simulation results show that the gain of the antenna is improved over the required frequency bands.

Mohamad Mantash

Papers

Investigation of Flexible Textile Antennas and AMC Reflectors

Beam-Tilting Endfire Antenna Using a Single-Layer FSS for 5G Communication Networks

Design methodology for wearable antenna on artificial magnetic conductor using stretch conductive fabric

Millimeter-Wave Beam-Tilting Vivaldi Antenna With Gain Enhancement Using Multilayer FSS

Dual-band CPW-fed G-antenna using an EBG structure