Перегляд за автором "Man, Ka Lok"

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  • Зображення мініатюри
    Публікація
    Design and Optimization of a Planar UWB Antenna
    (EWDTS, 2013) Lim, Eng Gee; Wang, Zhao; Juans, Gerry; Man, Ka Lok; Zhang, Nan; Hahanov, V. I.; Litvinova, E. I.; Chumachenko, S. V.; Mishchenko, A.; Dementiev, S.
    In this paper, we present our design on a simple, low-profile wideband planar antenna with a pure circular radiator fed by a 50 Ω microstrip line. By investigating the feeding position and ground plane dimensions, the antenna is optimized to have a very wide bandwidth that covers the whole FCC-allocated ultra-wideband (UWB) spectrum. Because of the additional patch beneath the radiator, the bandwidth can be further extended towards the lower side of the frequency spectrum. This antenna is finally modified to have a bandwidth from 2 to 12 GHz, which satisfies system requirements for S-DMB, WiBro, WLAN, CMMB and the entire UWB with S11 < -10dB. Since the Federal Communications Commission (FCC) of United States allocated the unlicensed frequency spectrum from 3.1 GHz to 10.6 GHz for commercial applications of ultra-wideband (UWB) technology in 2002 [1], ultra-wideband (UWB) technology has gained great popularity in research and industrial areas because of its high data rate wireless communication capability for various applications. As a crucial part of the UWB system, UWB antennas have been investigated extensively by researchers and numerous proposals for UWB antenna designs have been reported [2-5]. In [2], a new ultra-wideband antenna consisting of two steps, a single slotted patch and a partial ground plane is designed to operate from 3.2 to 12 GHz. In J. N. Lee’s work [3], an ultrawideband antenna composed of a modified trapezoidal radiating patch, a PI-shaped matching stub, CPW feeding, and two steps for impedance matching has been proposed for UWB applications. In [4], an ultrawideband microstrip-fed monopole antenna with a narrow slit and a modified inverted U-slot on the patch is presented. Recently, a small planar antenna fed by a microstrip line has been investigated and designed to exhibit dualband operation for Bluetooth (2.4 - 2.484 GHz) and UWB (3.1 - 10.6 GHz) bands [5]. However, many of the proposed designs employed slots or other complicated modifications in the antenna radiator and/or ground plane. These designs may pose complications during fabrication of the antenna since the tolerance of the increased special features/variables could be problematic when it goes to mass production, and instability due to the fact that complicated antenna structures may also occur in practice. Therefore, we are motivated to design a low complexity, low cost and compact antenna with wide frequency coverage supporting various applications such as Satellite Digital Multimedia Broadcasting (S-DMB), Wireless Broadband (WiBro), Wireless Local Area Network (WLAN), China Multimedia Mobile Broadcasting (CMMB) and UWB. In this paper, we present a very simple circular planar antenna with operating bandwidth ranging from 2 GHz to 12 GHz by integrating several techniques into one compact antenna. The design approach is very similar to our previously reported paper [6]. We start with a simple circular planar antenna fed by a 50Ω microstrip line with a truncated ground plane. Next, based on the study of the size of the radiator and current distribution, the antenna is designed to have an operating bandwidth covering the entire UWB band, i.e. 3.1 - 10.6 GHz. Then, the study on the size of the partial ground plane is conducted to increase the bandwidth towards the lower side of the frequency spectrum, to cover the bands for WLAN (2.4 - 2.484 GHz) and CMMB (2.635 – 2.66 GHz). With an extra patch printed on the back side of the substrate, underneath the circular radiator, the bandwidth can be further increased to cover Wibro (2.3 - 2.4 GHz) and S-DBM (2.17 -2.2 GHz) without significantly influencing other frequency bands. Thus the proposed antenna can be used for various applications such as SDMB, Wibro, WLAN, CMMB and the operating bands are evaluated using with the criterion of having return loss S11 less than 10 dB. Simulated radiation patterns over the whole frequency bands are acceptable.
  • Зображення мініатюри
    Публікація
    Internet of Things: A Practical Implementation based on a Wireless Sensor Network Approach
    (EWDTS, 2012) Mercaldi, Michele; D’Oria, Andrea; Murru, Davide; Liang, Hai-Ning; Man, Ka Lok; Lim, Eng Gee; Hahanov, V. I.; Mischenko, A.
    In this paper we present an introduction and an overview of the Internet of Things concept and its possible realization of an infrastructure based on a Wireless Sensor Network. Our proposed solution aims for memory and power consumption efficiency. Similarly, our proposed implementation is informed by (1) open technology standards; (2) accessibility and reachability; and (3) multi functionality and modularity. In addition, we place emphasis on the use of very low power devices and communication protocols. Internet of Things (IoT), a term first coined by Kevin Ashton in 1999 , is used to refer to uniquely identifiable objects (or more broadly things) and their virtual representations, similar to the network of websites in an internet. The idea is to have all things tagged and, if that were the case, they could be identified and inventoried by computers. If this could be implemented, it will transform drastically our way of life —waste will be reduced significantly; stores will not run out of stock; and stolen items could be easily located. A main component of IoT infrastructure is “smart objects” which are objects that hold a unique identifier. The identifier will allow the objects to be located, enable them to interact with their surrounding environment, and let them communicate with each other for data exchange and collaboration. Within the IoT paradigm, smartness is not only for objects but includes the nature of the networks that connect them. To build smart objects, we need sensors, actuators, radio-frequency identification (RFID) tags, etc. Applications of IoT include domotics, industrial application, nature and environmental monitoring. Even after more than a decade since it was first coined, the implementation of a system of IoT has yet to become a reality. In this paper we proposed a plausible implementation of an IoT system or infrastructure based on a wireless sensor network (WSN) approach. We propose hardware and software possibilities to support such an infrastructure.