MIMO antenna systems can greatly improve the capacity and transmission rate of wireless communication. In this letter, two four-port multiple-input-multiple-output (MIMO) antenna systems are proposed in mobile devices. An algorithm of calculating envelope correlation (ρ e ) between antenna units is also proposed. By this algorithm the ρ e of the PIFA-MIMO antenna system has been calculated. First, a PIFA-MIMO antenna system is designed for ISM (2.4 GHZ) application. The slots are etched on the ground and the antenna units are placed in such a way that the polarization diversity is exploited to enhance the impedance matching and isolation. Based on this, a printed wideband MIMO antenna system is proposed for portable 3G and 4G applications by means of multi-branch and the defect of ground technology, increasing the bandwidth and reducing mutual coupling between the antennas. The simulation results show that the return loss and isolation of the two antenna systems can meet the performance requirements of the antennas in the mobile phone.
This paper describes the entire process of completing a multicast streaming media server and applying it to a cellphone live streaming system. By using the RTSP protocol, the streaming media server controls the connection of video capture client, data stream reception and processing as well as playback interaction. The media server can publish real-time data from a data acquisition terminal or a historical data file in the server to the Web so that users on the network can view all the videos through a variety of terminals anytime and anywhere, without having to wait for all the data downloaded completely. The streaming media server of the system is developed based on an open-source streaming media library Live555. The developed server can run on a Windows or a Linux system. The standard RTSP/RTP protocol is used and the video media format is H264. The paper mainly introduces the design of a streaming media server, including data processing for real time, designing a data source, the implementation of multi-acquisition end and multi-player operation, RTSP interaction and RTP packaging, and the setting up of the data buffer in the server. Experiment results are given to show the effect of the system implementation.
Chirp-SF signal is a new kind of high range of resolution signal. This paper firstly points out that the traditional signal processing methods will cause "ghost images" when there is more than one scatter in a distance unit. Then a new method which including interfacing each sub-pulse in the Timeline and frequency shifting to Constitute a FM signal is proposed. We can solve this problem and have a high range resolution by execute the pulse compression on the synthetic signal. In the end, the simulation result is shown to prove the correction of the Algorithm.
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