In this paper, a wearable antenna array based on a 9 × 3 artificial magnetic conductor (AMC) array is proposed with the characteristics of compact, low profile, low specific absorption rate (SAR), high front-to-back ratio (FBR) and high gain for wireless body area network (WBAN) bands. The proposed wearable antenna consists of a four-element array and an AMC array. The size of antenna array loaded AMC is 137.7 × 45.9 mm2. The dielectric substrate of the antenna and the AMC structure are made of 0.1 mm liquid crystal polymer material, which is flexible and low profiled. The antenna operates from 5.62 to 6 GHz after the AMC structure is loaded. The gain increases by 3.23 dB, reaching 12.03 dB at 5.8 GHz. And the FBR value is raised by 26.04 dB. The highest SAR value of the simulated antenna on the human model is 0.0496 W/kg, far less than the US federal or EU requirements. After constructing and testing the antenna, the outcomes of the tests agreed with the results of the simulation. The flexible antenna array with AMC structure has good prospect in WBAN applications.

This article presents a flexible wearable KIT monopole antenna for biomedical application. A metamaterial unit cell is proposed to improve the antenna performance. The proposed antenna and the metamaterial are fabricated on 1 mm-thick polydimethylsiloxane substrate to operate in the ISM frequency band of 2.45 GHz. Integration of the metamaterial improves the gain and reduces the specific absorption rate (SAR) of the antenna. The overall dimension of the antenna with the metamaterial is 49 × 49 × 19 mm3. The designed antenna is investigated for the loading effect of the body by placing on the hand phantom model. Bending tolerances are also analyzed for x and y direction with various bend radii. Gain and SAR of the proposed antenna are 4.61 dBi and 0.868 W/kg. The results of the fabricated prototype show that the proposed wearable antenna is safe for biomedical applications.

A compact, two-element textile MIMO antenna is designed with enhanced isolation by using modification in the ground, open-ended slots along with shorting pins. Maximum 27.8 dB isolation is achieved in two-element antennae, where the edge-to-edge distance is kept at 0.19 λ0 which is less than the conventional half wavelength. The Y-shaped decoupling and shorting pins improve the isolation up to 14 dB and can mitigate the current moment between the two ports effectively. The open slots in the ground are enhancing the mutual impedance and shift the operating band of the antenna toward the lower frequency band and thus size miniaturization is also achieved. The textile antenna achieves a 10 dB impedance bandwidth from 4.24 to 5.38 GHz with more than 21.1 dB isolation in the entire band. The phantom wrist model and bending analysis are carried out with the textile antenna to validate the on-body effects of the antenna in wearable and 5G applications.

In this work, a compact, wideband, circularly polarized wearable antenna is proposed using asymmetric coplanar strip feeding for wireless health monitor applications in the ISM frequency band. The proposed antenna consists of a composite right/left transmission line (CRLH TL) inspired structure to achieve compactness and a rectangular ring slot is created in the metallic ground to enhance the CP radiation of the antenna. A 5 × 5 artificial magnetic conductor unit cell-based metasurface is designed which is operating at 2.4 GHz as a ground plane for the CRLH-based CP antenna. Implementation of AMC-based metasurface as a ground plane results in enhancement of radiation characteristics of CRLH TL antenna. The proposed antenna has a small footprint of 50 × 50 mm2 with measured impedance bandwidth of 2.3–3.2 GHz. The 3 dB axial ratio bandwidth of the proposed antenna is 2.36–2.78 GHz with peak gain of 5.89 dBi. Simulation and experimental results show that proposed AMC-based antenna is robust in terms of structural deformation. Further, to validate the performance of the antenna for biomedical applications, we have simulated the proposed antenna with human phantom model. The proposed antenna exhibits stable scattering and radiation characteristics with the phantom body environment and due to the inclusion of AMC structure, the proposed design satisfies maximum specific absorption rate value given as per the IEEE standard safety guidelines.

A flexible and high gain saw-tooth-shaped boundary fractal wearable antenna is anticipated for WBAN applications. A square shape is converted to the saw-tooth-shaped boundary by sequentially rotating the square at an angle of 45° and overlaid on one another and repeated the same for three iterations. The geometry is built on a flexible jeans substrate, and the total size of the anticipated antenna is 0.583λ × 0.583λ × 0.02λ at 2.4 GHz. A prototype has been made to test its suitability for wearable applications' gain, bandwidth, and efficiency. The results revealed that the proposed antenna provides an impedance bandwidth of 4.2% and a peak gain of 5.76 dBi at the 2.45 GHz ISM band. The anticipated antenna is wrapped around foam cylinders of radii 70 and 50 mm to test the stability and deformability of its performance. The full ground plane isolates the antenna from the human body contributing to the lower SAR values. The simulated maximum achieved specific absorption rate (SAR) of 0.3025 and 1.16 W/kg for 10 and 1 g of average tissue for the input power of 100 mW, respectively, found within the standards as per FCC. The peak gain, compact size, and SAR permanence made the anticipated antenna a worthy candidate for wearable on/off body applications.

This paper presents a pattern diversity UWB antenna for Wireless Body Area Network (WBAN) communications. Pattern diversity antenna comprises two antenna elements with directional and omnidirectional patterns suitable for off-body and on-body communications respectively. Several broad-banding techniques such as Co-Planar waveguide, parasitic patches, and cavity resonant techniques are incorporated in microstrip antenna to achieve an ultra-wideband of 7.5 GHz (3.1 to 10.6 GHz) with a directional pattern. Monopole radiator topology is utilized to achieve a UWB frequency range of 2.6–10.6 GHz with an omnidirectional pattern. Pattern diversity is achieved using an orthogonal arrangement of the antenna elements in a compact size of 40 mm × 34 mm, maintaining the isolation >20 dB between the antennas. Gain varies from 2.2 to 4.6 dBi and 2.5 to 7.5 dBi for omnidirectional and directional antenna respectively. The simulated radiation efficiency for the directional antenna and the omnidirectional antenna are 74–86% and 52–66.5% respectively. The proposed design provides a good diversity performance in the entire UWB bandwidth with ECC<0.1 and a diversity gain of approximately 10 dB. SAR impact evaluated under various conditions is found to be <1.6 W/Kg for 1 gram of tissue.

This paper presents a comprehensive review of symmetrically shaped antennas in terms of antenna size, dielectric materials, resonating band, peak gain, radiation pattern, simulating tools, and their applications. In this article, flower shape, leaf shape, tree shape, fan shape, Pi shape, butterfly shape, bat shape, wearable, multiband, monopole, and fractal antennas are discussed. Further, a survey of previously reported bandwidth enhancement techniques of microstrip patch antenna like introduction of thick and lower permittivity substrate, multilayer substrate, parasitic elements, slots and notches, shorting wall, shorting pin, defected ground structure, metamaterial-based split ring resonator structure, fractal geometry, and composite right-hand/left-handed transmission line approach is presented. The physics of these techniques has been discussed in detail which is supported by circuit theory model approach.

In this paper, a flexible single fed planar circular polarized slot antenna is proposed for Internet of Things wideband applications. The antenna flexibility is achieved by employing a mechanically bendable liquid crystalline polymer substrate. The overall antenna volume is 50 mm × 42 mm × 0.1 mm. The antenna design uses 45° rotated elliptical ground structure for generating circular polarized radiation over wideband spectrum. Two parametrical analyses targeting the slot ground are introduced in order to achieve the most efficient design. The final antenna design demonstrates a good matching in terms of reflection coefficient (<−10 dB), semi-omnidirectional radiation patterns, average gain of 4 dB, and <3 dB axial ratio over entire frequency band of operation. All antenna parameters are studied in both straight and bent antenna setup scenarios. Good agreement between simulation and measurement results of the antenna parameters are achieved. For both straight and bent antenna scenarios, the antenna receiving functionality in time domain is confirmed by retrieving highly correlated impulse responses.