An efficient approach to achieve the shielding effectiveness (SE) by using a frequency-selective surface (FSS) is presented. This FSS, which consists of cross dipoles and rings printed on the opposite sides of a single-layer FR-4 substrate, exhibits a wide, 7.5-GHz stopband to provide simultaneous shielding in both X- and Ka-bands. Experimental results confirm SE of the prototype over an ultra-wide band with more than 20-dB measured attenuation. The design is compact and suitable to provide shielding against the radiation interference caused by license-free and other radio systems.

A Single-Layer Frequency-Selective Surface for Ultrawideband Electromagnetic Shielding

A compact and low-profile wearable antenna is presented for on-body wireless body area network (WBAN) applications. The proposed triangular patch antenna is designed using low-cost widely available vinyl polymer-based flexible substrate. The final antenna topology is obtained by the combination of the Koch fractal geometry, meandering slits, and defected ground structure, to achieve a novel hybrid structure with compact footprint, good structural conformability, and enhanced impedance bandwidth (BW) to operate in the Industrial, Scientific, and Medical band with center frequency at 2.45 GHz. The fabricated prototype of the antenna has shown a good agreement between numerical and experimental results. In comparison to state-of-the-art prototypes, our design has more compact form factor of 0.318λo × 0.318λo × 0.004λo, along with 7.75% impedance BW, a peak gain of 2.06 dBi, and overall radiated efficiency of 75%. For the assessment of a specific absorption rate (SAR) performance of our design, it is tested on realistic heterogeneous HUGO voxel model. Both numerical and experimental investigations revealed extremely good robustness to both human body loading and structural deformation, making it an ideal candidate for flexible and body-worn devices.

A Compact, Low-Profile Fractal Antenna for Wearable On-Body WBAN Applications

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.

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

A wearable circular ring slot antenna with electromagnetic bandgap (EBG) structure for wireless body area network application is proposed in this letter. According to the analysis of equivalent circuit model, the volume of the EBG element is miniaturized for wearable applications. The measured impedance bandwidth of the proposed antenna is observed to be 2.28–2.64 GHz, which covers the 2.4 GHz Industrial Scientific Medical (ISM) band. The measured half-power beamwidths are 60° and 54° in the H -plane and the E -plane, respectively, and the front-to-back ratios are 17 and 13 dB in the H -plane and the E -plane, respectively. The specific absorption rate calculated values for tissue in 1 g (for the U.S. standard) and 10 g (for Europe standard) are both less than the limitations. In conclusion, it is proper to use the proposed antenna in wearable applications.

Wearable Circular Ring Slot Antenna With EBG Structure for Wireless Body Area Network

This letter presents the design of a dual-band wearable fractal-based monopole patch antenna integrated with an electromagnetic band-gap (EBG) structure. The prototype covers the GSM-1800 MHz and ISM-2.45 GHz bands. The EBG structure reduces the radiation into the human body over 15 dB. It also reduces the effect of frequency detuning due to the human body. The performance of the antenna under bending, crumpling, and on-body conditions has been studied and presented. Specific absorption rate (SAR) assessment has also been performed to validate the antenna for its usefulness in wearable applications.

Dual-Band EBG Integrated Monopole Antenna Deploying Fractal Geometry for Wearable Applications

In this letter, a compact frequency selective surface (FSS) composed of a modified swastika unit cell having the smallest dimension of 7 × 7 mm2 is proposed. The design is aimed at the rejection of 5-GHz WLAN band. The unit-cell geometry resembles the shape of crossed dipoles to achieve compactness. The proposed FSS provides 400 MHz bandwidth with 20 dB insertion loss. The proposed design holds a stable response for TE and TM modes of polarization as well as oblique incidence angles, thus ensuring polarization and angular independent operation. The simulated results are validated with measured results obtained from the fabricated FSS.

A Compact Frequency Selective Surface With Stable Response for WLAN Applications

In this letter, two triband RFID antennas are proposed, one for the radio frequency identification (RFID) reader and the other for the RFID tag. The antenna is the crucial part in designing any RFID system. The reader antenna operates at 3.6, 5.8, and 8.2 GHz. The tag antenna operating frequencies are 3.9, 5.9, and 8.2 GHz. The applications of these frequencies are RFID for logistics management, traffic toll collection, and tagometry (telemetry using RFID), respectively. Fractal structures are employed as radiating elements for this multiband antenna.

Triband Antenna Structures for RFID Systems Deploying Fractal Geometry

This letter introduces a new method of achieving broad VSWR bandwidth and axial ratio bandwidth (ARBW) deploying fractal geometry in a single feed compact annular slot antenna loaded with diagonal slots. Various studies have been carried out for different iteration order (IO) and iteration factor (IF) on antenna performance. A measured VSWR bandwidth (2:1) of 400 MHz (1.37 GHz to 1.77 GHz) and measured ARBW of 360 MHz (1.47 GHz to 1.83 GHz) is achieved. A measured peak gain of 6.6 dB is reported at 1.775 GHz. This antenna can be applied to handheld devices applications and WSN node positioning requiring GPS Data.

Circularly Polarized Broadband Antenna Deploying Fractal Slot Geometry

Patterned deposition of highly flexible transparent conducting materials is essential to realize stretchable optoelectronic devices. Silver nanowires (NWs) are suitable for these applications becau...

Jayaram Kizhekke Pakkathillam

Papers

Dual-Band EBG Integrated Monopole Antenna Deploying Fractal Geometry for Wearable Applications

A Compact Frequency Selective Surface With Stable Response for WLAN Applications

Triband Antenna Structures for RFID Systems Deploying Fractal Geometry

Circularly Polarized Broadband Antenna Deploying Fractal Slot Geometry

Printable Silver Nanowire and PEDOT:PSS Nanocomposite Ink for Flexible Transparent Conducting Applications