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An Internal Wideband Monopole Antenna for UMTS/WLAN Dual-Mode Mobile Phone
 

An Internal Wideband Monopole Antenna for UMTS/WLAN Dual-Mode Mobile Phone

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An internal wideband metal-plate monopole antenna for mobile phone applications is presented. The antenna is easily fabricated by bending a single metal plate and suitable to be embedded within the ...

An internal wideband metal-plate monopole antenna for mobile phone applications is presented. The antenna is easily fabricated by bending a single metal plate and suitable to be embedded within the casing of a mobile phone as an internal antenna. Further, the antenna shows a wide operating bandwidth of about 5 GHz (about 1.8−6.7 GHz), making it easy to cover the UMTS band and the 2.4/5.2/5.8 GHz WLAN bands for mobile/WLAN dual-mode operation for a mobile phone.

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    An Internal Wideband Monopole Antenna for UMTS/WLAN Dual-Mode Mobile Phone An Internal Wideband Monopole Antenna for UMTS/WLAN Dual-Mode Mobile Phone Document Transcript

    • AN INTERNAL WIDEBAND MONOPOLE ANTENNA FOR UMTS/WLAN DUAL- MODE MOBILE PHONE Yung-Tao Liu1 and Saou-Wen Su2 1 Department of Physics, R.O.C. Military Academy, Feng-Shan 83059, Taiwan; Corresponding author: liuyt@ema.ee.nsysu.edu.tw 2 Technology Research Development Center, Lite-On Technology Corporation, Taipei 11492, Taiwan Received 22 November 2007 ABSTRACT: An internal wideband metal-plate monopole antenna for mobile phone applications is presented. The antenna is easily fabricated by bending a single metal plate and suitable to be embedded within the casing of a mobile phone as an internal antenna. Moreover, the antenna shows a wide operating bandwidth of about 5 GHz (about 1.8 – 6.7 GHz), making it easy to cover the UMTS band (1920 –2170 MHz) and the 2.4 –GHz (2400 –2484 MHz) and the 5.2/5.8-GHz (5150 –5350/ 5725–5825 MHz) WLAN bands for mobile/WLAN dual-mode opera- tion of a mobile phone. The proposed antenna is studied in detail, and the experimental and simulation results of the constructed proto- type are also presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1741–1744, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23546 Key words: mobile phone antennas; internal antennas; wideband anten- nas; planar monopole antennas; UMTS antennas 1. INTRODUCTION Planar metal-plate monopole antennas are easy to implement and can provide a wide impedance bandwidth [1-6], making them very promising to be applied to some wireless mobile devices [7]. However, the conventional planar monopole antenna usually has a large profile and needs to be protruded from the mobile phone casing when used as a mobile phone antenna, which greatly limits Figure 1 (a) Geometry of the proposed internal wideband monopole its practical applications. In this article, we demonstrate a prom- antenna; (b) detailed dimensions of the single metal plate used for fabri- ising wideband metal-plate monopole antenna for mobile-phone cating the antenna (dashed lines denote bending). [Color figure can be applications, especially for dual-mode mobile phones capable of viewed in the online issue, which is available at www.interscience.wiley. mobile (UMTS) and wireless local area network (WLAN in the com] 2.4/5.2/5.8 GHz band) communications. The proposed antenna occupies a compact volume of 10 20 20 mm3 only, making it very promising to be embedded within the casing of a practical mobile phone. Note that, the proposed antenna has an asymmet- rical two-branch feeding strip for input section. This structure is very promising for achieving bandwidth enhancement for a planar monopole antenna, which can easily provide a wide operating bandwidth of about 5 GHz (1818 – 6746 MHz here). In addition, the antenna with the proposed feeding strip together can easily be fabricated by using a single metal plate, and no external feeding network [8] is required. Details of the antenna design are de- scribed, and the experimental results of a constructed prototype are presented. 2. ANTENNA DESIGN Figure 1(a) shows the geometry of the proposed internal wideband metal-plate monopole antenna for a UMTS/WLAN dual-mode mobile phone. The antenna is easily fabricated by bending a single metal plate (a 0.2-mm thick copper plate) shown in Figure 1(b). The antenna shows a small cross-sectional area of 10 8 mm2 and a length of 19 mm with a feed gap of 1 mm, and is mounted at the center of the small ground plane (size 10 20 mm2) protruding Figure 2 Measured and simulated return loss for the proposed antenna. from the system ground plane. Note that between the feed gap is [Color figure can be viewed in the online issue, which is available at the central conductor (diameter 1.2 mm) of a 50- SMA connector www.interscience.wiley.com] DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 7, July 2008 1741
    • Figure 3 Measured radiation patterns at 2045 MHz. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com] located below a via-hole in the center of the small ground plane. In The proposed antenna, with the asymmetrical two-branch feed- addition, the length and width of the system ground plane are ing strip and the bending process shown in Figure 1(b), can be chosen to be 100 and 70 mm, respectively, which are reasonable divided into several portions, which easily makes the obtained dimensions for a practical PDA phone. impedance bandwidth to have a lower edge frequency less than 2 Figure 4 Measured radiation patterns at 2442 MHz. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com] 1742 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 7, July 2008 DOI 10.1002/mop
    • Figure 5 Measured radiation patterns at 5500 MHz. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com] GHz and provide a wide operating bandwidth of about 5 GHz. This and the main ground plane together operate in the high-order behavior is largely because the several resonant paths are obtained, resonant modes, thus leading to less smooth radiation patterns. which control the occurrence of the antenna’s different resonant Figures 6 and 7, respectively, plot the measured peak antenna modes. Moreover, a much more uniform current distribution in the gain and the simulation radiation efficiency against the UMTS planar monopole antenna is achieved. Note that the asymmetrical band and the 2.4/5.2/5.8 GHz WLAN band for the constructed two-branch feeding strip can provide additional coupling between prototype. The antenna gain in the UMTS band of about 3.1–3.5 the proposed antenna and the antenna ground plane, which helps dBi is obtained with the simulation radiation efficiency of about improve the impedance matching of the antenna, leading to a much 79 – 84%. The antenna gain in the 2.4 GHz band has a gain level wider impedance bandwidth obtained. In addition, owing to the of 3.3 dBi with the simulation radiation efficiency of about asymmetrical two-branch feeding strip, the proposed monopole 83%. In addition, in the 5.2/5.8 GHz band, the antenna gain antenna height above the small ground plane is reduced, which varies slightly in a range of about 4.4 – 4.9 dBi and the simu- helps achieve a compact size for the antenna. lation radiation efficiency exceeds about 84%. 3. EXPERIMENTAL RESULTS AND DISCUSSION 4. CONCLUSION The proposed antenna was constructed and studied with the design A wideband metal-plate monopole antenna suitable for applica- dimensions shown in Figure 1. Figure 2 shows the measured and tions of an internal mobile-phone antenna, especially for a PDA simulation return loss for the constructed prototype. The simula- tion results are obtained using the Ansoft simulation software high-frequency structure simulator (HFSS) [9], and good agree- ment between the experiment data and simulation result is seen. A very wide impedance bandwidth, defined by 10-dB return loss, is first obtained. The measured impedance bandwidth is about 5 GHz (1818 – 6746 MHz), which makes the antenna easily cover the UMTS band for mobile communications and the 2.4/5.2/5.8 GHz band for WLAN communications. The radiation characteristics were also studied. Figure 3 plots the measured radiation pat- terns at the center frequency (at 2045 MHz) of the UMTS band. Figures 4 and 5, respectively, show the measured radiation patterns at the center frequencies (at 2442 and 5500 MHz) of the 2.4 GHz WLAN band and the 5 GHz (5.2/5.8 GHz) WLAN band. By comparing the radiation patterns at 5500 MHz to those at 2045 and 2442 MHz, it is observed that the radiation patterns Figure 6 Measured antenna gain and simulated radiation efficiency for at 5500 MHz are seen to be less smooth. This characteristic is the UMTS band studied in Figure 2. [Color figure can be viewed in the largely because, at higher frequencies, the proposed antenna online issue, which is available at www.interscience.wiley.com] DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 7, July 2008 1743
    • ENHANCEMENT OF BROADBAND PERFORMANCE FOR ON-CHIP SPIRAL INDUCTORS WITH INNER-PATTERNED- GROUND Jinglin Shi,1 Sheng Sun,2 Yong Zhong Xiong,1 Wooi Gan Yeoh,1 and Kiat Seng Yeo2 1 Institute of Microelectronics, Singapore 117685; Corresponding author: jinglin@ime.a-star.edu.sg 2 Nanyang Technology University, Singapore 639798 Received 23 November 2007 ABSTRACT: A set of on-chip spiral inductors with novel inner-pat- terned-ground (IPG) is presented in this article to enhance the broad- Figure 7 Measured antenna gain and simulated radiation efficiency for band performance. By grounding the simple center metal cross, the IPG the WLAN band studied in Figure 2. [Color figure can be viewed in the structure, an additional inner ground path is formed, the input imped- online issue, which is available at www.interscience.wiley.com] ance of the spiral inductor is reduced at the higher frequency range. When compared with conventional inductors, the quality factor (Q) of the IPG inductors increases by 15–30% over the frequency range of phone capable of UMTS/WLAN dual-mode operation, has been 15–35 GHz. The IPG inductors can be modeled based on a simple proposed. The proposed antenna can easily be fabricated by using lumped equivalent circuit. The extracted inductance and quality factors a single metal plate, thus making it easy to construct at a low cost. are verified by on-wafer measurement up to 50 GHz. © 2008 Wiley Pe- Prototypes of the proposed antenna have been constructed and riodicals, Inc. Microwave Opt Technol Lett 50: 1744 –1746, 2008; studied. A wide bandwidth of about 5 GHz (1818 – 6746 MHz) has Published online in Wiley InterScience (www.interscience.wiley.com). been achieved, which makes the antenna very promising for cov- DOI 10.1002/mop.23545 ering the UMTS and the 2.4/5.2/5.8-GHz bands for UMTS/WLAN dual-mode operation. The experimental results also indicate that Key words: on-chip spiral inductor; CMOS; inner-patterned-ground; good radiation characteristics over the UMTS and WLAN bands quality factor have been obtained. 1. INTRODUCTION REFERENCES Silicon on-chip spiral inductors have been widely used in radio 1. M. Hammoud, P. Poey, and F. Colombel, Matching the input impedance frequency integrated circuits (RFICs) for wireless communication of a broadband disc monopole, Electron Lett 29 (1993), 406-407. systems such as wireless local area networks, personal handsets, 2. N.P. Agrawall, G. Kumar, and K.P. Ray, Wide-band planar monopole and global positioning systems. Monolithic inductors have drawn antennas, IEEE Trans Antennas Propag 46 (1998), 294-295. tremendous research effort over the past decades, especially in 3. K.L. Wong, T.C. Tseng, and P.L. Teng, Low-profile ultra-wideband recent years. A lot of modeling approaches have been reported in metal-plate antenna for mobile phone applications, Microwave Opt recent years [1-3]. But only a few works has been done on the Technol Lett 43 (2004), 7-9. novel design of the spiral inductor structure itself [4-6]. 4. S.Y. Lin, Multiband folded planar monopole antenna for mobile hand- The FCC has opened up 22–29 GHz for ultrawideband vehicle set, IEEE Trans Antennas Propag 52 (2004), 1790-1794. 5. Y.T. Liu, Wideband stubby monopole antenna for mobile phone, Elec- radar systems [7]. Consequently, a lot of research work published tron Lett 42 (2006), 385-387. on 24-GHz range, 24 GHz blocks, or transceivers [8, 9]. In this 6. Y.T. Liu, A stubby monopole antenna for UMTS mobile phones with article, a novel inner-patterned-ground (IPG) structure is proposed E911 function, Microwave Opt Technol Lett 49 (2007), 380-382. for the design of broadband spiral inductors. The enhancement of 7. K.L. Wong, Planar antennas for wireless communications, Wiley, New quality factor over the frequency range of 15–35 GHz has been York, 2003. achieved as compared to the conventional inductors. The resultant 8. E. Antonino-Daviu, M. Cabedo-Fabres, M. Ferrando-Bataller, and A. performance is verified by measurement based on standard 0.18 Valero-Nogueira, Wideband double-fed planar monopole antennas, m CMOS technology. Electron Lett 39 (2003), 1635-1636. 9. Ansoft Corporation, HFSS, http://www.ansoft.com/products/hfss/. 2. INDUCTOR DESIGN © 2008 Wiley Periodicals, Inc. A set of inductors with and without IPG structure is fabricated using standard 0.18 m CMOS technology (substrate resistivity 10 O-cm). Figures 1(a) and 1(b) show the die photo of the conven- tional spiral inductor and the IPG inductor, respectively, fabricated using standard CMOS process technology with six layers of metal TiW/Al-1% Si/TiW interconnects. The inductors have an inner diameter of 40 m and 50 m, a metal winding width of 5 m, a metal winding spacing of 5 m and two turns. The IPG inductor has a metal cross, i.e., the IPG structure inside the inductor coil which consists of metal 1 to metal 6 together with vials. The width of the cross bar is 3 m, and the distance from the edge of the sign to the inductor inner edge is 5 m. The cross sign is connected to the ground bar through metal 1. Because of the implementation of the IPG structure, the mag- netic field and the electric field to the substrate are modified. At 1744 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 7, July 2008 DOI 10.1002/mop