ping networks and technologies, J Lightwave Technol 18 (2000), 2058 –2075. 3. N. Deng, Y. Yang, C.K. Chan, W. Hung, L.K. Chen, Intensity- modulated labeling and all-optical label swapping on angle-modulated optical packets, IEEE Photon Technol Lett 16 (2004), 1218 –1220. 4. J. Yu and G.K. Chang, A novel technique for optical label and payload generation and multiplexing using optical carrier suppression and separation, IEEE Photon Technol Lett 16 (2004), 320 –322. 5. J. Yu, G.K. Chang, and Q. Yang, Optical label generation, erasure, and reinsertion in a packet switched optical network using optical carrier suppression, separation, and wavelength conversion, IEEE Photon Technol Lett 16 (2004), 2156 –2158. 6. T. Koonen, G. Morthier, et al., Optical packet routing in IP-over- WDM networks deploying two-level optical labeling, in Proc Eur Conf Optical Commun (ECOC2002), Copenhagen, Denmark, 2002, Paper 5.5.2. 7. N. Chi, B. Carlsson, P.V. Holm-Nielsen, C. Peucheret, and P. Jeppesen, Dispersion management for two-level optically labeled sig- nals in IP-over-WDM networks, Presented at the ECOC’02, Copen- hagen, Denmark, 2002, Paper 5.5.1. 8. C.W. Chow, H.K. Tsang, Optical label encoding and swapping using half-bit delayed dark RZ payload and DPSK label, Opt Exp 13 (2005), 5325–5330. 9. J. Yu, G.K. Chang, J. Barry, 40 Gbit/s signal format conversion from NRZ to RZ using a Mach-Zehnder delay interferometer, Opt Commun 248 (2005), 419 – 422. 10. C.-H. Cheng, The signal processing approach for the birefringent material based Mach-Zehnder interferometer design, Circuits Syst 1 (2005), pp. 211–214. 48th Midwest Symposium, Aug 7–10, 2005. 11. G.P. Agrawal, Fiber-optic communication systems, Wiley, New York, 1992, Chapter 4, pp. 133–178. © 2007 Wiley Periodicals, Inc. INTERNAL MEANDERED LOOP ANTENNA FOR GSM/DCS/PCS MULTIBAND OPERATION IN A MOBILE PHONE WITH THE USER’S HAND Chun-I Lin and Kin-Lu Wong Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwan, Republic of China Received 22 August 2006 ABSTRACT: A novel internal meandered loop antenna for application in a mobile phone for Global System for Mobile Communication/Digital Communication System/Personal Communication System (GSM/DCS/ PCS) multiband operation is presented. Along the symmetric metal-strip loop structure of the antenna, there are meandered sections for adjust- ing the antenna’s resonant frequencies and widened sections for improv- ing the impedance matching. The antenna’s first and second resonant modes (half- and one-wavelength modes) excited at about 900 and 1800 MHz for GSM/DCS operation. With the meandered sections in the loop structure, the antenna’s third resonant mode (1.5-wavelength mode) can be adjusted to be close to the second resonant mode at 1800 MHz to achieve a wider upper band for DCS/PCS operation. In addition, the central region of the proposed loop antenna is unoccupied, which can be used to accommodate possible nearby electronic components, such as the lens of a digital camera. Furthermore, effects of the user’s hand holding the mobile phone with the proposed loop antenna are analyzed in this study. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 759 –765, 2007; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/mop.22271 Key words: mobile antennas; loop antennas; internal mobile phone antennas; GSM/DCS/PCS mobile phone antennas 1. INTRODUCTION Recently, owing to the rapid growth in mobile communications, the internal antennas for mobile devices are usually required to be capable of multiband operation. For this application, many related designs of the planar inverted-F antenna for application in mobile phones have been reported [1]. However, all the operating bands of the multiband PIFAs are with unbalanced structures and will thus lead to larger excited surface currents on the system ground plane than the antennas with self-balanced structures [2]. In this case, larger antenna performance degradation due to the user’s adjacent effect than the antenna with self-balanced structures may be ex- pected. For achieving the self-balanced structures, the modified one-wavelength loop antennas suitable to be placed on the system ground plane of the mobile phone have been presented [2– 4]. These modified loop antennas, however, show mainly single-band operation and are with a two-layer or multilayer structure, which complicates the antenna configuration and increases the fabrication cost of the antenna. In this paper, we present a novel internal meandered loop antenna (MLA) capable of operating in the Global System for Mobile Communication/Digital Communication System/Personal Communication System (GSM/DCS/PCS) bands for mobile phone applications. The proposed MLA is mainly with a one-layer sym- metric metal-strip loop structure, which makes it easy to fabricate with a low cost. The antenna’s lower operating band is formed by the antenna’s first or fundamental resonant mode (half-wavelength mode), which covers the GSM (890 –960 MHz) operation. For the upper operating band, it has a wide bandwidth covering the DCS (1710 –1880 MHz) and PCS (1850 –1990 MHz) operation, and is formed by the antenna’s second resonant mode (one-wavelength mode) and third resonant mode (1.5-wavelength mode). A para- metric study on adjusting the three resonant modes of the proposed MLA to achieve the desired lower and upper operating bands for GSM/DCS/PCS multiband operation is presented. In addition, it is noted that among the antenna’s three excited resonant modes, the second resonant mode is with a self-balanced structure, while the other two modes are with unbalanced struc- tures. The antenna performances of the three resonant modes are discussed in this study. Further, the condition of the user’s hand holding the mobile phone with the proposed MLA is considered, and effects of the user’s hand on the antenna performances of the proposed MLA are analyzed. 2. ANTENNA DESIGN Figure 1(a) shows the top view of the proposed MLA placed at the top portion of the system ground plane of a mobile phone. The system ground plane in this study is printed on a 0.8-mm thick FR4 substrate of size 45  100 mm 2 , which is a reasonable size of general mobile phones. The MLA has a symmetric metal-strip loop pattern, which is cut from a 0.2-mm thick copper plate in the study. Note that, when there is no system ground plane, the MLA can only generate a one-wavelength resonant mode (the self-balanced mode). With the presence of the system ground plane, the MLA can generate additional half-wavelength and 1.5-wavelength reso- nant modes (the unbalanced modes). The successful excitation of the three resonant modes makes it possible to cover the GSM/ DCS/PCS operation for the proposed antenna. This behavior will be analyzed in more detail with the aid of Figure 7 in section 3 Detailed dimensions of the metal-strip loop pattern in the planar structure are given in Figure 1(b). The dashed line shown in the figure is the bending line. The bending line separates the metal-strip loop pattern into two portions: the radiation portion and the feeding portion. The radiation portion is located above the DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 49, No. 4, April 2007 759