Sat, 19 Jul 2008 02:58:28 BST CiteULike: dcastro's Lai http://www.citeulike.org/user/dcastro/author/Lai CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dcastro/article/2859756 <i>Antennas and Propagation, IEEE Transactions on, Vol. 55, No. 3. (2007), pp. 868-876.</i><br /><br />The analysis of resonant-type antennas based on the fundamental infinite wavelength supported by certain periodic structures is presented. Since the phase shift is zero for a unit-cell that supports an infinite wavelength, the physical size of the antenna can be arbitrary; the antenna's size is independent of the resonance phenomenon. The antenna's operational frequency depends only on its unit-cell and the antenna's physical size depends on the number of unit-cells. In particular, the unit-cell is based on the composite right/left-handed (CRLH) metamaterial transmission line (TL). It is shown that the CRLH TL is a general model for the required unit-cell, which includes a nonessential series capacitance for the generation of an infinite wavelength. The analysis and design of the required unit-cell is discussed based upon field distributions and dispersion diagrams. It is also shown that the supported infinite wavelength can be used to generate a monopolar radiation pattern. Infinite wavelength resonant antennas are realized with different number of unit-cells to demonstrate the infinite wavelength resonance Infinite Wavelength Resonant Antennas With Monopolar Radiation Pattern Based on Periodic Structures A Lai KMKH Leong T Itoh doi:10.1109/TAP.2007.891845 Antennas and Propagation, IEEE Transactions on, Vol. 55, No. 3. (2007), pp. 868-876. 2008-06-03T18:57:48-00:00 2007 Antennas and Propagation, IEEE Transactions on 55 3 868 876 antenna crlh metamaterial http://www.citeulike.org/user/dcastro/article/2859279 <i>Advanced Information Networking and Applications, 2003. AINA 2003. 17th International Conference on (2003), pp. 318-323.</i><br /><br />The IEEE 802.11 standards support the peer-to-peer mode independent basic service set (IBSS), which is an ad hoc network with all its stations within each other's transmission range. In an IBSS, it is important that all stations are synchronized to a common clock. Synchronization is needed for frequency hopping and power saving. The synchronization mechanism specified in the IEEE 802.11 standards has a severe scalability problem. The probability that stations may get out of synchronization is pretty high in large IBSS. A new synchronization algorithm has been proposed for large-scale ad hoc networks. We propose a more efficient algorithm in this paper that synchronizes the clock more accurately. We are able to synchronize the clock within 100 /spl mu/s when the number of stations is more than 300. This is a big improvement over the current best algorithm and the 802.11 specified protocol. To our best knowledge, the current best algorithm can synchronize the clock within 550 /spl mu/s for a 300-station network. The 802.11 standard protocol can have clock drift over 5000 /spl mu/s for the same network. Efficient,and scalable IEEE 802.11 ad-hoc-mode timing synchronization function Ten-Hwang Lai Dong Zhou doi:10.1109/AINA.2003.1192897 Advanced Information Networking and Applications, 2003. AINA 2003. 17th International Conference on (2003), pp. 318-323. 2008-06-03T14:50:00-00:00 2003 Advanced Information Networking and Applications, 2003. AINA 2003. 17th International Conference on 318 323 ad-hoc synchronization time wifi http://www.citeulike.org/user/dcastro/article/2839871 <i>Microwave Conference, 2006. 36th European (2006), pp. 937-939.</i><br /><br />This paper reviews applications of the infinite wavelength supported by certain metamaterials accomplished to date by the authors' group. In particular, novel microwave resonators, dividers, and antennas based on the fundamental infinite wavelength supported by the composite right/left-handed metamaterial transmission line are presented. Applications and the unique properties of these novel microwave devices are also presented Applications of Infinite Wavelength Phenomenon A Lai KMKH Leong Tatsuo Itoh doi:10.1109/EUMC.2006.281075 Microwave Conference, 2006. 36th European (2006), pp. 937-939. 2008-05-28T07:02:30-00:00 2006 Microwave Conference, 2006. 36th European 937 939 metamaterial http://www.citeulike.org/user/dcastro/article/2839865 <i>Antennas and Propagation Society International Symposium, 2005 IEEE, Vol. 3A (2005), pp. 798-801 vol. 3A.</i><br /><br />An FDTD method, combined with thin wire and thin slot algorithms used to analyze a metamaterial based on periodic mushroom structures, is proposed. This proposed method is suitable for analyzing problems with fine structural details. Two examples of mushroom structures are investigated to compare the results between simulation and measurement to show left-handed propagation properties. Accuracy of the proposed method is verified compared to the measurement results. Efficient FDTD method for analysis of left-handed mushroom structure Wei-Yang Wu A Lai KMKH Leong Chih-Wen Kuo T Itoh doi:10.1109/APS.2005.1552377 Antennas and Propagation Society International Symposium, 2005 IEEE, Vol. 3A (2005), pp. 798-801 vol. 3A. 2008-05-28T06:58:07-00:00 2005 Antennas and Propagation Society International Symposium, 2005 IEEE 3A 798 801 vol. 3A crlh fdtd metamaterial mushroom http://www.citeulike.org/user/dcastro/article/2839856 <i>Microwave Symposium, 2007. IEEE/MTT-S International (2007), pp. 1423-1426.</i><br /><br />In this paper, a mode selective metamaterial which supports either forward or backward waves within the same frequency bandwidth is presented. The choice between dispersion operations is based on the mode excitation applied to the metamaterial. A demonstration microstrip prototype of this novel dual-mode composite right/left-handed metamaterial is realized and characterized. The metamaterial is right-handed under even-mode excitation and is left-handed under odd-mode excitation in the 1.86 GHz -2.00 GHz frequency range. Circuit simulations with the numerical and experimental results of the dual-mode metamaterial transmission line are performed to demonstrate electromagnetic wave steering and spatial multiplexing at a fixed frequency based on dispersion selectivity. Dual-Mode Metamaterial with Backward and Forward Wave Selectivity A Lai KMK Leong T Itoh doi:10.1109/MWSYM.2007.380499 Microwave Symposium, 2007. IEEE/MTT-S International (2007), pp. 1423-1426. 2008-05-28T06:51:03-00:00 2007 Microwave Symposium, 2007. IEEE/MTT-S International 1423 1426 metamaterial http://www.citeulike.org/user/dcastro/article/2839849 <i>Microwave Symposium Digest, 2005 IEEE MTT-S International (2005), 4 pp..</i><br /><br />A novel N-port series divider based on a composite right/left-handed (CRLH) transmission line (TL) supporting a wave with an infinite wavelength is presented. This novel divider evenly divides power in phase to an infinite number of ports at its infinite wavelength frequency. In addition, it is shown that the novel series divider's performance is not dependent on the location of its output ports. The basic operating principle is based on the fact that a CRLH TL is able to support a wave with an infinite wavelength. As a result, all points along the CRLH TL have the same magnitude and phase. A 3-port series divider consisting of a 8 unit-cell CRLH TL is shown to exhibit 0.22 dB maximum magnitude difference and 1.32/spl deg/ maximum phase difference between output ports at its infinite wavelength frequency. In addition, a 5-port series divider consisting of a 13 unit-cell CRLH TL is fabricated and shown to exhibit 0.30 dB maximum magnitude difference and 6.3/spl deg/ maximum phase difference between output ports at its infinite wavelength frequency. Both simulation and experimental results are shown to support the authors' claims. A novel N-port series divider using infinite wavelength phenomena A Lai KMKH Leong T Itoh doi:10.1109/MWSYM.2005.1516834 Microwave Symposium Digest, 2005 IEEE MTT-S International (2005), 4 pp.. 2008-05-28T06:43:47-00:00 2005 Microwave Symposium Digest, 2005 IEEE MTT-S International 4 pp. array metamaterial http://www.citeulike.org/user/dcastro/article/2839846 <i>Microwave Conference, 2006. APMC 2006. Asia-Pacific (2006), pp. 1060-1066.</i><br /><br />In this paper, a free space power combining oscillator antenna array using a metamaterial based injection locking coupling network is described and demonstrated. The unique metamaterial series coupling network utilizes the infinite wavelength phenomenon which allows it to support an infinitely long wave at a non-zero frequency. It is demonstrated that equal phase/amplitude oscillator synchronization can be achieved without regards to the antenna element spacing in the array. A small scale prototype oscillator array is designed to have compact, non-uniform element spacing to demonstrate the concept. An EIRP of 18 dBm at 2.37 GHz is measured. Power combining oscillator array using metamaterial based injection locking coupling network KMK Leong A Lai T Itoh doi:10.1109/APMC.2006.4429592 Microwave Conference, 2006. APMC 2006. Asia-Pacific (2006), pp. 1060-1066. 2008-05-28T06:43:38-00:00 2006 Microwave Conference, 2006. APMC 2006. Asia-Pacific 1060 1066 active array metamaterial oscillator http://www.citeulike.org/user/dcastro/article/2839828 <i>Antenna Technology Small Antennas and Novel Metamaterials, 2006 IEEE International Workshop on (2006), pp. 404-407.</i> Composite Right/Left-Handed Metamaterial Antennas A Lai KMKH Leong T Itoh Antenna Technology Small Antennas and Novel Metamaterials, 2006 IEEE International Workshop on (2006), pp. 404-407. 2008-05-28T06:41:50-00:00 2006 Antenna Technology Small Antennas and Novel Metamaterials, 2006 IEEE International Workshop on 404 407 antenna crlh metamaterial http://www.citeulike.org/user/dcastro/article/2839810 <i>Antenna Technology: Small Antennas and Novel Metamaterials, 2005. IWAT 2005. IEEE International Workshop on (2005), pp. 69-72.</i><br /><br />Recent research on metamaterials with simultaneously negative permittivity (/spl epsiv/) and permeability (/spl mu/), more commonly referred to as left-handed (LH) materials, has stimulated the development of novel concepts and applications. Since right-handed (RH) effects are unavoidable, practical LH materials (LHM) are in reality composite right/left-handed (CRLH) materials. Interestingly, the co-existence of LH and RH contributions in CRLH materials, far from being detrimental, leads to useful phenomena. By applying a transmission-line (TL) approach towards CRLH metamaterials, the unique properties of these metamaterials have been used to realize novel microwave devices including antennas with characteristics (functionalities or performance) surpassing those of conventional (i.e., RH) materials. Microwave devices based on composite right/left-handed (CRLH) transmission line metamaterials A Lai C Caloz T Itoh doi:10.1109/IWAT.2005.1461003 Antenna Technology: Small Antennas and Novel Metamaterials, 2005. IWAT 2005. IEEE International Workshop on (2005), pp. 69-72. 2008-05-28T06:41:03-00:00 2005 Antenna Technology: Small Antennas and Novel Metamaterials, 2005. IWAT 2005. IEEE International Workshop on 69 72 crlh metamaterial microwave tl http://www.citeulike.org/user/dcastro/article/2809071 <i>Antennas and Propagation Society International Symposium 2006, IEEE (2006), pp. 394-397.</i><br /><br />Application of left-handed (LH) metamaterials in the field of microwave engineering has grown rapidly following their experimental verification. In particular, the LH transmission line (TL) has been used to realize various microwave devices not possible with conventional TLs alone. The purpose of this paper is to summarize some of the recent advances in microwave devices based on LH TLs. In particular, devices based on the unique characteristics of the composite right/left-handed (CRLH) TL, which is the general model of a practical LH TL, are presented. Microwave devices based on left-handed transmission lines A Lai KMKH Leong T Itoh doi:10.1109/APS.2006.1710541 Antennas and Propagation Society International Symposium 2006, IEEE (2006), pp. 394-397. 2008-05-18T14:06:55-00:00 2006 Antennas and Propagation Society International Symposium 2006, IEEE 394 397 crlh lh metamaterial microwave tl http://www.citeulike.org/user/dcastro/article/2674709 <i>Microwave Conference, 2007. European (2007), pp. 400-403.</i><br /><br />In this paper, metamaterial-based transmission lines will be discussed, with a focus placed on how these structures can be utilized in microwave systems. The different devices necessary for a basic dual-band receiver will be discussed and it will be shown how these dual-band components can be realized using metamaterial-based structure. Also, two different types of two-dimensional beam scanning systems will be introduced that utilize both one and two dimensional metamaterial-based structures. Practical applications of metamaterial-based structures in microwave systems CA Allen A Lai Cheng-Jung Lee T Itoh doi:10.1109/EUMC.2007.4405211 Microwave Conference, 2007. European (2007), pp. 400-403. 2008-04-15T18:08:16-00:00 2007 Microwave Conference, 2007. European 400 403 metamaterial microwave structure http://www.citeulike.org/user/dcastro/article/1876650 <i>Microwave Magazine, IEEE, Vol. 5, No. 3. (2004), pp. 34-50.</i><br /><br />Metamaterials are artificial structures that can be designed to exhibit specific electromagnetic properties not commonly found in nature. Recently, metamaterials with simultaneously negative permittivity (/spl epsiv/) and permeability (/spl mu/), more commonly referred to as left-handed (LH) materials, have received substantial attention in the scientific and engineering communities. The unique properties of LHMs have allowed novel applications, concepts, and devices to be developed. In this article, the fundamental electromagnetic properties of LHMs and the physical realization of these materials are reviewed based on a general transmission line (TL) approach. The general TL approach provides insight into the physical phenomena of LHMs and provides an efficient design tool for LH applications. LHMs are considered to be a more general model of composite right/left hand (CRLH) structures, which also include right-handed (RH) effects that occur naturally in practical LHMs. Characterization, design, and implementation of one-dimensional and two-dimensional CRLH TLs are examined. In addition, microwave devices based on CRLH TLs and their applications are presented. Composite right/left-handed transmission line metamaterials A Lai T Itoh C Caloz doi:10.1109/MMW.2004.1337766 Microwave Magazine, IEEE, Vol. 5, No. 3. (2004), pp. 34-50. 2007-11-07T07:48:30-00:00 2004 Microwave Magazine, IEEE 5 3 34 50 crlh metamaterial