Due to the rapid development of wireless communication technologies, the number of wireless users are radically increasing. Currently, ~23 billion wireless devices are connected to the internet, and these numbers are expected to increase manifolds in the years to come. The technology growth of the fifth-generation (5G) wireless systems will be needed to meet this high demand of the network. 5G wireless systems offer data-rates of up to 10Gbps, 1-ms latency, and reduced power consumption. It is a known fact that 5G wireless systems will be exploiting beyond the presently used 3 GHz microwave and millimetre-wave (mm-wave) frequency bands. This is the primary driver in the development of the 5G wireless system. Multi-beam Phased array antenna (PAA) systems are typically used in the deployment of 5G systems for high-gain and directionality. In current 5G and future Beyond 5G (B5G) antenna array systems, beamforming networks (BFNs) such as the Butler Matrix (BM) will play a key role in achieving multi-beam characteristics. So, this paper presents an extensive review of the BM based BFNs, and discusses which type of BM will be suitable for the phased array antenna (PAA) systems in the upcoming 5G and next-generation of B5G wireless systems. Moreover, this paper also summarizes the different types of BM designs based on the number of layers. The BMs are classified into the bi-layer, tri-layer, and four-layer structures. It includes different techniques that have been used to solve the problem of crossing, narrow bandwidth, and size reduction of the BM. From the previous studies, it is found that most of the past research work was performed using the bi-layer BM system, whereas the difficult geometries like tri- and four-layer BM are avoided due to their complex fabrication process. It is also found in this paper that the metamaterial (MTM) based bi-layer BM achieves low insertion-loss and phase-error, excellent bandwidth and compact size, and good S-parameter performance, which makes them an ideal BFN candidate for the upcoming 5G and next-generation B5G systems.

The design and analysis of a compact dual-band wearable antenna for WBAN applications is presented. The antenna was prototyped on a semi-flexible Rogers Duroid RO3003™ with compact dimensions of 41 × 44 mm ² which corresponds to 0.33 λ ₀ × 0.35 λ ₀ , where λ ₀ is the free space wavelength at 2.4 GHz. The antenna is designed in the preliminary stage to resonate at 5.8 GHz. An inverted U-shaped slot is added to the patch to create one more resonant frequency at 2.4 GHz. In order to enhance the antenna’s bandwidth and gain, two slots at the patch’s bottom edge and a partial ground are added. The measured percentage of impedance bandwidth at 2.4 GHz and 5.8 GHz are 3.75% and 5.17%, respectively. The gain is measured to be 3.74 dBi and 5.13 dBi and the efficiency is 91.4% and 92.3%, respectively at the operating bands. The measured radiation patterns exhibit a bidirectional and directional radiation pattern in the E -plane at 2.4 GHz and 5.8 GHz bands, while omnidirectional radiation patterns are observed in the H -plane. At 2.4 GHz, the SAR limits are simulated to be 0.955 W/kg and 0.571 W/kg for 1 g and 10 g of human tissue, while at 5.8 GHz, the SAR limits are 0.478 W/kg and 0.127 W/kg, respectively. Therefore, the proposed antenna has met the FCC and ICNIRP standards. Bending conditions and on-body measurements of the proposed antenna indicate that the antenna’s performance is unaffected. As a result, it is shown that the antenna possessed the ability to be utilized in WBAN applications.

Communication technology is increasingly pervading everyday life. The rapid progress in wireless communication besides the increasing interest in wearable antennas and electronics in civil, medical, sport wear and military domains promises to replace wiredcommunication networks in the near future in which antennas are in more important role. Recently, there has been growing interest in the antenna community to merge between wearable systems technology, Ultra-Wideband (UWB) technology and textile technology. All these together have resulted in demand for flexible fabric antennas, which can be easily attached to a piece of clothing. In this paper, three different structures of UWB antennas using clothing materials and suitable for wearable application were fabricated and presented. The substrate of the designed antennas was made from jeans textile material, while radiating element and ground plane are made out of copper tape. The operating frequency of all three designs is between 3 GHz and 12 GHz. Measured results are compared with simulations and good agreement was observed.

The detection of partial discharge (PD) activities in high-voltage equipment can be conducted according to several mechanisms of signal detection, including electromagnetic wave signal detection, acoustic signal detection, chemical reactions, electrical signal detection, and optical emission detection. Recently, multiple methods of detection and localization of partial discharge activities, which occurred in power transformers and gas-insulated switchgear (GIS), have been proposed to monitor the health condition of high-voltage equipment, especially when the awareness regarding preventive maintenance has been emphasized at the industrial level and among electrical providers. In aligning the needs of the industrial sector and the improvement of PD-detection methods, this manuscript focuses on reviewing the current practice methods for the detection and localization of PD signals in high-voltage equipment, comparing their efficacy, and summarizing the future direction of research work-related methods of PD detection. The comparative reviews are discussed in terms of the mechanism of PD signal detection, indication parameters, calibration techniques, and the advantages and limitations of each method of PD measurement in detail.

This work presents the design and implementation of active antennas as a part of a healthcare monitoring system that is based on the Internet of Things (IoT). The monitoring system comprises a SEN11547 pulse sensor and an LM35 temperature sensor for measuring heart rate in Beats Per Minute (BPM) and body temperature in Degree Celsius (°C). This data is then sent to the ThingSpeak IoT platform, which necessitates the integration with the NodeMCU ESP-32S Wi-Fi module to ensure the availability of data. Two dual-band (2.4 GHz and 5.8 GHz) microstrip patch antennas, one with a PIN diode and one without, are fabricated using Rogers Duroid RO3003™ substrate. Both antennas have dimensions of 41 × 44 mm². In order to achieve a dual-band operation at 2.4 GHz, a slot in the shape of an inverted letter U is introduced, to the existing patch which generates a 5.8 GHz frequency band. By controlling the PIN diode’s ON and OFF state, the active antenna can switch between a single band of 5.8 GHz and a dual-band of 2.4 GHz and 5.8 GHz. At both frequencies, the measured radiation patterns exhibit bidirectional and directional characteristics in the E -plane, whereas an omnidirectional pattern can be observed in the H -plane. In terms of nonlinear characteristics of the antenna, the third-order intermodulation distortion products (IMD3) frequencies are generated within an input power range of 0 to 20 dBm from the two-tone nonlinear measurements. Specifically, the IMD3 at 2.4 GHz is measured at -36.18 dBm and -47.19 dBm at 5.8 GHz. Additionally, the measurement showed that the 1-dB gain compression point (P _1-dB ) was not detected at 2.4 GHz, indicating linear behavior within the RF input power range. However, at 5.8 GHz, the P _1-dB was observed at an RF input power level of 13.8 dBm, suggesting linear functionality up to this power level. The experimental data are obtained from ten participants with ages ranging between 18 and 40 years old for 10-minutes duration with a 1-minute step size which implies 10 samples. For comparison and validation, the measurements are compared with the commercially available Laird Connectivity 2.4GHz/5.8GHz dipole antenna. It can be observed that the heart rate ranges from 85 BPM to 92 BPM for the active antenna whereas for the reference antenna, the values range from 84 to 90 BPM, which implies a good agreement. On the other hand, the body temperature ranges from 29 to 37°C for the active antenna and from 30 to 36°C for the reference antenna, which infers a good agreement as well. Therefore, it is shown that the proposed dual-band active antennas in this work can be effectively integrated into the IoT-based healthcare monitoring system.