A compact wearable antenna with a novel miniaturized electromagnetic bandgap (EBG) structure at 2.4 GHz for medical application is presented in this letter. The design demonstrates a robust, compact, and low-profile solution to meet the requirements of wearable applications. The EBG structure reduces the back radiation and the impact of frequency detuning due to the high losses of human body. In addition, the structure improves the front-to-back ratio (FBR) by 15.5 dB. The proposed compact antenna with dimensions of 46 × 46 × 2.4 mm ³ yields an impedance bandwidth of 27% (2.17-2.83 GHz), with a gain enhancement of 7.8 dBi and more than 95% reduction in the specific absorption rate. Therefore, the antenna is a promising candidate for integration into wearable devices applied in various domains, specifically biomedical technology.

The recent advancement in the wireless technology has led to the advent of wearable antennas. These antennas are utilized for Wireless Body Area Networks (WBANs) purposes such as health-care, military sportive activities and identification systems. Compared to conventional antennas, wearable antennas operate in an environment which is in highly near proximity to the curved human body. Therefore, the wearable/flexible antenna performance parameters, including reflection coefficient, bandwidth, directivity, gain, radiation characteristic, Specific Absorption Rate (SAR), and efficiency are anticipated to be influenced by the coupling and absorption by the human body tissues. In addition, an electromagnetic band-gap structure is introduced in the wearable/flexible antenna designs to enable and give a high degree of isolation from the human body which also decreases the SAR dramatically. This paper reviews the state-of-the-art wearable/flexible antennas integrated with the electromagnetic band-gap structure on flexible materials concentrating on single and dual-band designs. Besides, it also highlights the challenges and considerations for an appropriate wearable/flexible antenna.

A compact wearable symmetrical e-slots antenna operated at 2.4 GHz was proposed for Medical Body Area Network applications. The design was printed onto a highly flexible fabric material. The final design topology was achieved by the integration of symmetrical e-slots antenna with an Electromagnetic Band-Gap (EBG) and Defected Ground Structure (DGS). The use of EBG was to isolate the body and antenna from each other whereas the DGS widened the bandwidth. This combination forms a novel and compact structure that broadens bandwidth. This broadened bandwidth makes the structure robust to deformation and loading in the human body. The design achieved a measured impedance bandwidth of 32.08 %, a gain of 6.45 dBi, a Front to Back Ration (FBR) of 15.8 dB, an efficiency of 72.3% and a SAR reduction of more than 90%. Hence, the integration of symmetrical e-slots antenna with EBG and etched DGS is a promising candidate for body-worn devices.

The compact and robust high-impedance surface (HIS) integrated with the antenna is designed to operate at a frequency of 2.45 GHz for wearable applications. They are made of highly flexible fabric material. The overall size is $45\times \,\,45\times 2.4$ mm ³ which equivalent to $0.37\lambda \text{o}\times 0.37\lambda \text{o}\times 0.02$ mm ³ . The value of using HIS lies in protecting the human body from harmful radiation and maintaining the performance of the antenna, which may be affected by the high conductivity of the human body. Besides, setting the antenna on the human body by itself detunes the frequency, but by adding HIS, it becomes robust and efficient for body loading and deformation. Integrated antenna with HIS demonstrates excellent performance, such as a gain of 7.47 dBi, efficiency of 71.8% and FBR of 10.8 dB. It also reduces the SAR below safety limits. The reduction is more than 95%. Therefore, the presented design was considered suitable for wearable applications. Further study was also performed to show the useful of placing antenna over HIS compared to the use of perfect electric conductor (PEC). The integrated design was also investigated with the worst case of varying the permittivity of body equivalent model which shows excellent performance in term of reflection coefficient and SAR levels. Hence, the integrated antenna with HIS is mechanically robust to human body tissue loading, and it is highly appropriate for body-worn applications.

This paper presents the findings of a steerable higher order mode (TE $^{\mathrm {y}}_{1\delta 3}$ ) dielectric resonator antenna with parasitic elements. The beam steering was successfully achieved by switching the termination capacitor on the parasitic element. In this light, all of the dielectric resonator antennas (DRAs) have the same dielectric permittivity similar to that of ten and excited by a $50\Omega $ microstrip with a narrow aperture. The effect of the mutual coupling on the radiation pattern and the reflection coefficient, as well as the array factor, was investigated clearly using MATLAB version 2014b and ANSYS HFSS version 16. As the result, the antenna beam of the proposed DRA array managed to steer from −32° to +32° at 15 GHz. Furthermore, the measured antenna array showed the maximum gain of 9.25 dBi and the reflection coefficients which are less than −10 dB with the bandwidth more than 1.3 GHz, which is viewed as desirable for device-to-device communication in 5G Internet of Things applications.

In this paper presents a compact square ring patch antenna with miniaturized AMC structure at 5.8 GHz for WBAN applications. To minimize detuning, keeping its radiation efficiency high and acceptable gain while keeping the SAR levels low for safety is a challenging task. One of the critical issues in WBAN antenna design is the size of the antenna for portable devices, because the size affects the gain and bandwidth. The AMC configuration decreases the back radiation and the effect frequency detuning results from the high loss in the human body. Furthermore, the AMC also increases the front-to-back ratio (FBR) of 15.3 dB. The proposed antenna has dimensions of 15.27×15.27×2.2 mm3 and provides a 404 MHz impedance bandwidth, with a gain improvement of 8.69 dBi and a 93.7% reduction of the initial SAR value. For this reason, the antenna is suitable for WBAN application in various fields, particularly in medical technology.