One of the complex tasks in mass production of RF electronics is printing the communication antenna using electrically conductive ink. For example, this is very common for radiofrequency identification (RFID) tags. Electrical properties of the ink are mostly determined by conductive (e.g. silver) particles mixed into the ink solution and the way they 'connect' in the cured ink. It is also desirable to minimise the amount of ink used per antenna, because high-conducting metals like silver used in the ink are rather expensive. Metal-based inks have limited conductivity, so the thicker the cured ink layer will be the better the antenna radiation efficiency can be achieved, but also the higher will be the costs. In the paper, the authors report on the investigations of the possibility of minimising the amount of ink used per antenna. This can be achieved by printing thicker ink layers, where antenna structures are known to have high current density. Two common antenna structures and a dedicated antenna for passive RFID are used in the investigation. The main result of the paper is that radiation efficiency depends primarily on the total amount of ink used for printing the antenna, rather than on the variations of the layer thickness within the antenna structure.
Abstract-Fragment structure should find its application in acquiring high isolation between multipleinput multiple-output (MIMO) antennas. By gridding a design space into fragment cells, a fragmenttype isolation structure can be constructed by metalizing some of the fragment cells. For MIMO isolation design, cells to be metalized can be selected by optimization searching scheme with objectives such as isolation, return losses, and even radiation patterns of MIMO antennas. Due to the flexibility of fragment-type isolation structure, fragment-type structure has potentials to yield isolation higher than canonical isolation structures. In this paper, multi-objective evolutionary algorithm based on decomposition combined with genetic operators (MOEA/D-GO) is applied to design fragment-type isolation structures for MIMO patch antennas and MIMO PIFAs. It is demonstrated that isolation can be improved to different extents by using fragment-type isolation design. Some technique aspects related to the fragment-type isolation design, such as effects of fragment cell size, design space, density of metal cells, and efficiency consideration, are further discussed.
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