Antenna design for wireless communication

Recent developments in computing,sensing and communication technologies coupled with the need to continuously monitor physical phenomena have led to the advanced of Wireless Sensor Networks (WSNs). WSN containsfour main components: A radio, sensors, a processor and battery. A WSN is organized by densely deployed sensor nodes in an application area. In most deployments, the sensor nodes have self-organizing capabilities, to form an proper structure in order to collaboratively perform a particular task. Wireless Sensor Networks are found suitable for applications such as surveillance,accuracyagriculture, smart homes, automation, habitat monitoring, vehicular traffic management and disaster detection. The key restriction in the development of WSNs are limited battery power, cost, memory limitation, limited computational capability, and the physical size of the sensor nodes. Probing and development in WSN technology has been primarily application-driven. In the past decade, immense research has been done in:protocol design and energy efficient hardware, identifying alternate power sources, distributed detection techniques, multihop protocols, scheduling, cross-layer optimization, localization, time synchronization and coverage. Most usuallyused wireless communications standard in WSNs is according to the IEEE 802.15.4, usually referred to as Zigbee. There are three main areas that has received much less attention are: (i) very low cost and very low power mixed signal design of the WSN radio chip, (ii) raise power sources like low cost, small form factor photovoltaics, and (iii) low cost sensors technology for different applications in particular biosensors. Because of the increasing usage of wireless communication applications, the performance recovery studies of such systems has found a growing research area in last years. Antennas as one of the most important parts of these systems have gained a great attention. Among the different types of antennas, circularly polarized (CP) antennas are the most desirable ones, owing to their unavoidable competency like reducing polarization mismatch and multipath fading. To benefit from broadband and low profiles, diffrent shapes and designs of broadband circularly polarized slot antennas have been developed by applying different techniques on patch and ground structures. Patch, microstrip and slot antennas due to their adaptability with integrated circuit systems are widely being used in circularly polarized structures. Recently different methods are presented for creating circularly polarized operation band. A microstrip slot antenna is a good offer as it is low specifications, low cost, lightweight, and can be easily integrated with monolithic microwave integrated circuits (MMICs).To prosper the operating bandwidth and not decrease the antenna size, applying the printed slot antenna is a feasible method. For the printed slot antenna is a double of the microstrip antenna, it is as well as feasible that by presenting some disorder to the slot antenna, circularly polarized (CP) radiation of slot antenna can be performed. CP antennas are more attentionthan other importance systems in wireless communications, sensors, radio frequency identifier (RFID), and vehicular radar. CP antennas is a good choice among the various designs and structures in wireless communications to raise of system implementationoffering better mobility, and weather penetration, more than the linearly polarized (LP) antennas. Also byapplyingthe CPantennas in wireless communication systems, arranging the direction of the antenna between the transmitter and receiver is not needed any more. CP antennas overcome the multipath fading problem and enhance system performance. Through feeding methods, coplanar waveguide (CPW) feed has some advantages like wide bandwidth, easy integration and single metallic layer. In order to producing CP radiation, created some of the methodssuch as : improvising two inverted-L grounded strips around two opposite corners of the slot, improvising T-shaped grounded metallic strip, which is orthogonal to the axis of the CPW feed-line, using an asymmetrical CPW fed from a corner of the slot with an embedding pair of grounded strips implanted in the slot, striped slot antenna with longerfraught, utilizing the additional arc-shaped grounded metallic strip for circular and linear polarization, and embedding a firelight shaped feed line and inverted-L grounded strips are used in literature. Through extensive simulation and measurements done, the designed antennas are all optimized and presented.