排序方式: 共有29条查询结果,搜索用时 31 毫秒
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In this paper, we consider a multi-user cognitive radio network (CRN) equipped with an intelligent reflecting surface (IRS). We examine the network performance by evaluating the fairness of the secondary system, which is satisfying the minimum required signal to interference and noise ratio (SINR) for each secondary user (SU). The minimum SINR of the SUs is maximized by joint optimization of the beamforming vector and three-dimensional beamforming (3DBF) angles at the secondary base station (SBS) and also the phase shifts of the IRS elements. This optimization problem is highly non-convex. To solve this problem, we utilize Dinkelbach’s algorithm along with an alternating optimization (AO) approach to achieve some sub-problems. Accordingly, by further applying a semi-definite relaxation method, we convert these sub-problems to equivalent convex forms and find a solution. Furthermore, analytically we propose an algorithm for optimizing 3DBF angles at the SBS. Through numerical results, the improvement of the sum SINR of the secondary system using the proposed method is illustrated. Moreover, it is shown that as the number of reflecting elements of IRS increases, the sum SINR significantly augments while satisfying fairness. Also, the convergence of the proposed algorithm is verified utilizing numerical results. 相似文献
22.
Shaoqiu Xiao Bing-Zhong Wang Gaofeng Wang 《International Journal of Infrared and Millimeter Waves》2002,23(7):1091-1099
Reconfigurable antenna is a novel concept of antenna. A novel reconfigurable millimeter-wave patch antenna is proposed and simulated by the finite-difference time-domain (FDTD) method. The simulation results demonstrate that the antenna can operate in two states and shift the operation frequency band between 22.830.8GHz and 28.737.3GHz as the state is changed. This antenna is useful for millimeter-wave wireless communication and radar systems. 相似文献
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随着海洋探索和军事应用的迫切需求,水声通信需要向高数据率、高可靠性方向发展。正交频分复用技术被视为水声高速通信的新途径,并被成功应用于水声通信,在水声通信中展现了其优越性。高度灵活的自适应平台的发展,激发了可重编程水声调制解调器的发展,以适应不同实验/应用场景的需求。文中从带宽、调制方案、数据率、传输距离、误码率方面,介绍了国内外研究机构对可重编程正交频分复用水声调制解调器研究的进展,并对其中的技术进行概述。最后对可重编程正交频分复用水声调制解调器进行了展望。认为可重编程正交频分复用水声调制解调器需要的是分块接收处理的自适应实时扩展平台,同时也坚信水声网络的发展和需求必将推动智能水声通信的发展。 相似文献
24.
A novel and simple technique to realize reconfigurable microwave photonic transversal filter is presented. In the proposed method, a multi-wavelength source and a dispersive medium are applied to achieve multiple taps; and an electro-optic ceramic material-based variable gain tilt filter (VGTF) is utilized to control the tap weights of the filter. The VGTF is computer-controlled via a universal serial bus interface, which enables real-time reconfiguration of the filter. Filter responses with different passband bandwidth and different sidelobe suppression can be achieved. Compared with previous approaches, the given method features in less optical components involved and faster response speed. A three-tap reconfigurable filter with sub-millisecond response speed is experimentally demonstrated. 相似文献
25.
Minming Geng Lianxi Jia Lei Zhang Lin Yang Ping Chen Yuliang Liu 《Optics Communications》2009,282(17):3477-3480
We designed and fabricated a four-channel reconfigurable optical add-drop multiplexer based on silicon photonic wire waveguide, which is controlled through the thermo-optic effect. The effective footprint of the device is about 1000 × 500 μm2. The minimum insertion loss including the transmission loss and coupling loss is about 10.7 dB. The tuning bandwidth is about 17 nm, the average tuning efficiency about 6.11 mW/nm and the tuning speed about 24.5 kHz. 相似文献
26.
Huilai Liu Bing-Zhong Wang Wei Shao 《International Journal of Infrared and Millimeter Waves》2007,28(1):25-31
A novel dual-band bi-directional reconfigurable antenna based on Koch patch is presented in this paper. By controlling the
switches in the slots etched on the Koch patch, different far field bi-directional patterns at the dual-band around 60 GHz/80 GHz
could be achieved. And full azimuthal coverage at this dual-band is possible by electronically controlling the switches in
the slots of the patch.
This work was supported by the National Natural Science Foundation of China (No. 60371008, No. 90505001) and the CRT Program
of UESTC. 相似文献
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一种新型可配置全光分插复用器的设计 总被引:1,自引:1,他引:0
本文提出了一种新型的基于光纤光栅和光纤环形镜的可动态配置的全光分/插复用器,并对这种结构实现单信道、多信道或有选择性地对奇次信道或偶次信道进行下路或直通配置进行了模拟和分析,说明了这种结构的可行性. 相似文献
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