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A single‐fed microstrip patch antenna with frequency and polarization diversities is presented in this article. The proposed antenna consists of a square patch fed along its diagonal line with four parasitic stubs added around its four sides connected by four PIN diodes. The center of edges of two stubs far away from the feed point is connected to ground via another two diodes, while those of the other two stubs are connected to ground via capacitors. By turning these diodes on and off, the antenna has five different operating states. It is capable of switching between right hand circular polarization and left hand circular polarization in the frequency band (2.422–2.448 GHz), and also can operate at two frequency bands with horizontal and vertical polarization or vertical and horizontal polarization, respectively. In addition, it can radiate 45° linear polarization as a traditional patch antenna fed along its diagonal line. The measured results verify the reconfigurable characteristics of the antenna and demonstrate that it is a good candidate for wireless communication applications. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1494–1500, 2015

At present, machine learning, especially active learning in machine learning, is introduced in cyberspace security field. In this paper, we first analyze the background of cyberspace security and profile active learning. And then we focus on a survey on the application research of active learning in cyberspace security field, mainly including system software security, network security and application security. In the end, we also explore some potential future issues on active learning in cyberspace security.