Previous works have shown that wearable antennas can operate ideally in free space; however, degradation in performance, specifically in terms of frequency shifts and efficiency was observed when an antenna structure was in close proximity to the human body. These issues have been highlighted many times yet, systematic and numerical analysis on how the dielectric characteristics may affect the technical behavior of the antenna has not been discussed in detail. In this paper, a wearable antenna, developed from a new electro-textile material has been designed, and the step-by-step manufacturing process is presented. Through analysis of the frequency detuning effect, the on-body behavior of the antenna is evaluated by focusing on quantifying the changes of its input impedance and near-field distribution caused by the presence of lossy dielectric material. When the antenna is attached to the top of the body fat phantom, there is an increase of 17% in impedance, followed by 19% for the muscle phantom and 20% for the blood phantom. These phenomena correlate with the electric field intensities (V/m) observed closely at the antenna through various layers of mediums (z-axis) and along antenna edges (y-axis), which have shown significant increments of 29.7% in fat, 35.3% in muscle and 36.1% in blood as compared to free space. This scenario has consequently shown that a significant amount of energy is absorbed in the phantoms instead of radiated to the air which has caused a substantial drop in efficiency and gain. Performance verification is also demonstrated by using a fabricated human muscle phantom, with a dielectric constant of 48, loss tangent of 0.29 and conductivity of 1.22 S/m.

Frequency detuning issues in antenna operation due to structural deformation have become a concern, especially for flexible devices such as a textile antenna. Under deformed conditions such as during bending, the antenna might not operate at the desired frequency, causing performance degradation. Therefore, a 1.575 GHz textile antenna for GPS tracking application with defected ground structure is proposed in this paper to alleviate the frequency detuning issues and is demonstrated under two bending conditions, H-plane and E-plane. The implementation of DGS is expected to minimize the frequency detuning by increasing the bandwidth. Hence, the frequency detuning effects could be minimized under bent conditions with broader bandwidth and acceptable antenna performance. In this paper, a planar textile-based antenna with the dimension of 90mm ( $L$ ) $\times100$ mm ( $W$ ) was designed, and three rectangular slots were applied at the ground to create DGS. A self-developed electro-textile and polyester were used as the antenna conductive material and substrate. Through the study, a detailed analysis was conducted for both antennas, with and without DGS. The significance of DGS in the proposed design is evaluated and clarified by comparing electric and magnetic field intensities in non-radiating and radiating edges. The detailed performance comparison were observed and analyzed through S-parameter, gain, radiation pattern, and current distribution. The technical performance of the proposed technique is validated through simulation and measurement. DGS implementation has improved the antenna bandwidth from 4.04% to 12.20%, with 1.45dB gain and 23.75% radiation efficiency. As a result, the antenna can operate at the desired frequency under both bending conditions. DGS method provides simplicity in its design, and this method has been widely used in conventional antennas previously. However, the detailed behaviour of field intensity around the non-radiating and radiating edges have not been demonstrated and analyzed. Therefore, the validation of the proposed design through a detailed analysis of E-field and H field intensity concerning antenna configurations; with and without DGS becomes the main contribution of this paper. In addition, the study of bending on different bending radius is also conducted in this paper.

In the 5G system, multiple-input multiple-output (MIMO) antennas for both transmitting and receiving ends are required. However, the design of MIMO antennas at the 5G upper band is challenging due to the mutual coupling issues. Many techniques have been proposed to improve antenna isolation; however, some of the designs have impacts on the antenna performance, especially on the gain and bandwidth reduction, or an increase in the overall size. Thus, a design with a detailed trade-off study must be implemented. This article proposes a new C-shaped parasitic structure around a main circular radiating patch of a MIMO antenna at 16 GHz with enhanced isolation features. The proposed antenna comprises two elements with a separation of 0.32λ edge to edge between radiation parts placed in a linear configuration with an overall dimension of 15 mm × 26 mm. The C-shaped parasitic element was introduced around the main radiating antenna for better isolation. Based on the measurement results, the proposed structure significantly improved the isolation from −23.86 dB to −32.32 dB and increased the bandwidth from 1150 MHz to 1400 MHz. For validation, the envelope correlation coefficient (ECC) and the diversity gain (DG) were also measuredas 0.148 dB and 9.89 dB, respectively. Other parameters, such as the radiation pattern, the total average reflection coefficient and the mean effective gain, were also calculated to ensure the validity of the proposed structure. Based on the design work and analysis, the proposed structure was proven to improve the antenna isolation and increase the bandwidth, while maintaining the small overall dimension.

A compact simple structure modified Swastika shape multiband patch antenna is designed and investigated. The antenna, which occupies an overall dimension of 0.305λ × 0.305λ × 0.012λat lower frequency, has a simple structure which comprises of a planar wide square slot in the ground with four slits and Swastika shape radiation patch with a rectangular slot. The proposed Swastika shape antenna was designed and analyzed by using a finite element method based high frequency structural simulator HFSS. The experimental and numerical results exhibit that the antenna operates over the frequency ranges 950 MHz (2.28–3.23 GHz), 660 MHz (3.28–3.94 GHz), and 1120 MHz (5.05–6.17 GHz) suitable for WLAN (2.4/5.2/5.8 GHz) and WiMAX 2.5/3.5/5.5 GHz applications. It has a good omnidirectional radiation pattern and reaches 3.97 dBi at 2.44 GHz, 4.04 dBi at 3.5 GHz, and 3.25 dBi at the band of 5.98 GHz. A prototype is fabricated and then measured. The experimental and simulation results show good impedance bandwidth, radiation pattern, and stable gain across the operating bands.

In the 5G mobile system, new features such as millimetre wave operation, small cell size and multi beam are requested at base stations. At millimetre wave, the base station antennas become very small in size, which is about 30 cm; thus, dielectric lens antennas that have excellent multi beam radiation pattern performance are suitable candidates. For base station application, the lens antennas with small thickness and small curvature are requested for light weight and ease of installation. In this paper, a new lens shaping method for thin and small lens curvature is proposed. In order to develop the thin lens antenna, comparisons of antenna structures with conventional aperture distribution lens and Abbe’s sine lens are made. Moreover, multi beam radiation pattern of three types of lenses are compared. As a result, the thin and small curvature of the proposed lens and an excellent multi beam radiation pattern are ensured.

E-Textiles have gained enormous attention due to their specific characteristics in various non-conventional applications such as electromagnetic shielding materials. With the advent of various high frequency-driven devices, the need to restrict the non-ionizing radiations from their undesired effects became imperative. Due to the ease of production, better electrical conductivity and durability, the conductive hybrid cover yarns with continuous metallic filaments have earned its place as the most convenient form of yarns to develop E-textiles. However, controlling the amount of conducting material in yarns poses a challenge as the increase in size of the metallic filaments are associated with reduced electromagnetic shielding effectiveness due to increased stiffness of yarns, which resists in proper interlacement and hence causes openness in fabrics. The proposed design of conductive hybrid cover yarns is proven to have better tensile properties and modulus, therefore this design is more suitable to produced fabrics with higher cover factors. The amount of conducting material in the proposed design increased significantly without changing the size of the continuous filaments. Moreover, 99.9% shielding effectiveness is achieved with this increased metal content in fabrics in S-band and partly C-band microwave frequencies.