Application of Antennas and Filters in Wireless Sensing and Communication

Dear Colleagues,

In recent years, the demand for compact microstrip filters has been increasing due to the recent expansion in microwave and mobile communication systems. So far, a few effective techniques have been successfully developed to miniaturize the filter size and to transform the simple filter structure to a multi-band filter without additional components. Nowadays, multi-standard wireless communication systems require multi-band operating transceivers. Dual-band and multi-band filters are in demand for these wireless systems. In addition to having multi-band operation, low cost, simplicity, small occupied area, and performance are also desired features for these filters. Microstrip planar multi-band filters have been widely proposed as an approach to solving the most difficult technical challenges in microwave and wireless communication areas. To achieve these targets, many filtering structures have been investigated, including open-circuited stubs, hi-low impedance, parallel coupled, and end coupled. Nevertheless, these methods have ensured that satisfactory results remain unattainable. In order to approach the desired results, a DGS–DMS filter could be an effective solution. Due to their improved performance characteristics, many filter techniques and methodologies have been proposed and successfully realized. Defected ground structures (DGSs) with and without periodic array have been realized by etching a pattern in the backside of the metallic ground plane to obtain the stop band effect. DGSs often consists of two large defected areas and a narrow connecting slot channel which corresponds to its equivalent LC elements. The DGS with periodic or non-periodic topology leads to a reject band in some frequency ranges due to the slow wave effect that results from an increase in the effective capacitance and inductance of the transmission line. The DGS topologies can be integrated with other microwave circuits and can be used in combination with antennas, couplers, power dividers, and several microstrip devices in order to minimize the size and to improve the features of the electrical components.

Multiple service technologies have been broadly developed in recent years, especially in the radio frequency (RF) devices of the modern wireless communication systems, such as high-speed wireless fidelity (WiFi), Bluetooth, worldwide interoperability for microwave access (WiMAX), and high performance radio local area network (HiperLAN) systems operating at frequencies between 2 and 6 GHz. In order to accommodate this multi-band RF signal transmission and reception into a single RF transceiver, dual or more band devices are required to incorporate circuits working in different bands into a single unit so that the size, cost, and device number can be reduced. To meet this demand, several multi-band antennas with a variety of services have been developed. However, a big challenge remains in designing this type of antenna with a suitably compact circuit size, high gain, and more design feasibility. To achieve this goal, a new antenna structure was designed, simulated, and manufactured.

The new topology is combined with microstrip filter (filtenna) so that the overall size of the transceiver can be reduced and the capability of antennas as an antenna filter improved. Based on the filtenna and defected ground structure (DGS) method, new generations of wearable smart antennas with interesting roles can be developed, simulated, optimized, and tested. These new smart devices and smart textiles, along with broadband mobile technologies, can empower wearable sensors with a significant impact on the future of digital healthcare. Despite the recent evolution in this field, challenges related to lack of precision, reliability, user comfort, rigid form, and challenges in data analysis and interpretation have limited their wide-scale application. Therefore, it is necessary to develop a new, reliable, and user-friendly approach in facing these problems.

Dr. Ahmed Boutejdar
Guest Editor

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• microstrip filters
• planar antennas
• sensors
• healthcare sensing
• wireless sensor networks
• sensing technologies
• underwater wireless sensor network (UWSN)
• defected ground structure (DGS)
• DGS-planar filter using MEMS technology
• filtenna