Beam capture efficiency (BCE) is one key factor of the overall efficiency for a microwave power transmission (MPT) system, while sparsification of a large-scale transmitting array has a practical significance. If all elements of the transmitting array are excited uniformly, the fabrication, maintenance, and feed network design would be greatly simplified. This paper describes the synthesis method of the sparse uniform-amplitude transmitting array with concentric ring layout using particle swarm optimization (PSO) algorithm while keeping a higher BCE. Based on this method, uniform exciting strategy, reduced number of elements, and a higher BCE are achieved simultaneously for optimal MPT. The numerical results of the sparse uniform-amplitude concentric ring arrays (SUACRAs) optimized by the proposed method are compared with those of the random-located uniform-amplitude array (RLUAA) and the stepped-amplitude array (SAA), both being reported in the literatures for the maximum BCE. Compared to the RLUAA, the SUACRA saves 32% elements with a 1.1% higher BCE. While compared to the SAA, the SUACRA saves 29.1% elements with a bit higher BCE. The proposed SUACRAs have higher BCEs, simple array arrangement and feed network, and could be used as the transmitting array for a large-scale MPT system.
Reconfigurable antennas due to their versatile qualities are highly demanded nowadays. A novel frequency reconfigurable patch antenna with two metallic rings around a rectangular patch is presented in this paper. Frequency reconfigurability can be achieved by changing the radiating surface of antenna. Surrounding metallic rings are connected to center patch with switches. The antenna operate in 1.8 GHz and 2.4 GHz frequency bands, when the switches are turned ON and OFF respectively. When the switches are turned ON they add external rings to radiating surface, hence increasing the surface size which in return changes the operating frequency of antenna. Different types of switching elements like MEMS, varactor diodes PIN diodes or optical switches can be used depending upon the nature of application. In this paper optical switches are chosen due to their advantage of not interfering with antenna radiation characteristics due to no need of biased lines. Antenna presented in this paper can be reconfigured to operate on Wi-Fi (2.4 GHz) and GSM (1.8 GHz) frequencies at a time. The antenna gives directivity and efficiency of (7.89 dBi, 48 %) and (8.2 dBi, 93 %) at 1.8 GHz and 2.4 GHz respectively. CST (Computer Simulation Tool) is used for design and simulation of proposed antenna. Index Terms-Reconfigurable antenna, Dual band, Micro strip patch antenna.
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