Ping Wang, Guang-Jun Wen, Yong-Jun Huang and Yuan-Hua Sun A compact coplanar waveguide (CPW)-fed planar monopole antenna with triple band operation is presented. By inserting two I-shaped notched slots and a open-ended U-shaped slot on the edge of the radiation patch, and integrating two symmetrical meander microstriplines on the upper edge of two rectangular ground planes, three operating bands covering 2.4 –2.63, 3.23 –3.8 and 5.15 –5.98 GHz can be achieved. Moreover, the designed antenna, with compact size of 23 × 30 mm2, can provide excellent characteristics, including better performance of interference suppression, nearly dipole-like radiation pattern and moderate gain for three bands, which prove that the proposed antenna is very suitable for WiFi/WiMAX applications.
Introduction: Wireless communications have been developed widely and rapidly, which has lead to a great demand in designing compact, low-profile, and multiband antennas for mobile terminals, especially for satisfying the wireless local area network (WLAN/WiFi) standards of 2.4– 2.484/5.15– 5.825 GHz and the worldwide interoperability for microwave access (WiMAX) standards of 2.5– 2.69/3.4 – 3.69/5.25– 5.85 GHz. The microstrip printed antenna may be an excellent candidate owing to its attractive merits, such as simple structure, ease of fabrication, high integration with active devices and nearly omnidirectional radiation patterns. Thus, several printed monopole antennas [1, 2] and slot antennas [3, 4] have been proposed for WiFi/WiMAX applications. However, most of them have large dimensions and do not pay attention to interference suppression, because there are many other existing narrowband services such as C-band satellite communications that have occupied some licensed frequency bands, which may result in lower performance of interference suppression. To avoid the problem, a distinct triple-band mirrored-L monopole antenna with better performance of interference suppression is proposed [5], but it has a large size of 53.73 × 67.04 mm2. Reference [6] continues the research by using a small ground-plane size and achieves a wide frequency coverage. However, this antenna has also large size (34 × 46 mm2). In this Letter, a distinct triple-band antenna employing a symmetrical coplanar waveguide (CPW) feed for WiFi/WiMAX applications is presented. By using two I-shaped notched slots and an open-ended U-shaped slot on a radiation patch, along with introducing two symmetrical meander microstrip-lines on the ground plane, the proposed antenna can generate six resonant modes to cover the desired bands. Compared to those designs shown in [1– 6], the antenna has not only better performance of interference suppression, but also smaller size.
and two I-shaped notched slots are inserted into a radiation patch, which controls the lower band (2.4/2.5 GHz) and the upper band (5.2 GHz). Furthermore, two equal rectangular ground planes of size 5.8 × 13.3 mm are situated symmetrically on each side of the CPW line and integrate with two symmetrical meander microstrip-lines in the upper edge of the ground plane. By optimising two meander microstrip-lines carefully, three resonate modes can be excited, of which two resonate modes appeared in the medium band (3.35 and 3.72 GHz) and another resonate mode happened in the upper band (5.87 GHz). This arrangement was found to be effective in obtaining an appropriate impedance bandwidth. The proposed structure is optimised using an Ansoft High Frequency structure simulator (HFSS) and the optimised values are illustrated in Fig. 1. 0 reflection coefficient, dB
Compact CPW-fed planar monopole antenna with distinct triple bands for WiFi/WiMAX applications
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Antenna configuration: The geometrical configuration of the proposed antenna is shown in Fig. 1. The antenna has a single-layer metallic structure and is printed on an inexpensive FR-4 substrate of thickness 0.75 mm, with dielectric constant of 4.6 and a loss tangent of 0.02. A 50 V CPW transmission line of strip width 2.8 mm, and gap 0.3 mm is used for feeding the antenna. The overall dimensions of the antenna are only 23 × 30 mm. In this design, one open-ended U-shaped slot
ELECTRONICS LETTERS 29th March 2012 Vol. 48
a 2.56 GHz b 3.6 GHz c 5.36 GHz
Results and discussion: The measurement of reflection coefficient is carried out with a network analyser Agilent N5230A. Fig. 2 shows the simulated and measured reflection coefficients for the proposed antenna, which presents a little discrepancy owing to the error of substrate parameters of the FR-4 substrate and tolerance in manufacturing. It is clearly seen that six resonant modes are excited at the frequencies of 2.46, 2.54, 3.35, 3.72, 5.34, and 5.87 GHz. Continuous two resonant modes of them are deliberately made to merge as a single broadband in order to form three distinct bands. Three distinct operating bands with 10 dB return loss are about 2.4 – 2.63, 3.23– 3.8, and 5.15 – 5.98 GHz, corresponding to 9.15, 16.2, and 15%, respectively. Obviously, the achieved bandwidths cover not only the WiFi bands of 2.4/5.2/
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5.8 GHz, but also the WiMAX bands of 2.5/3.5 /5.5 GHz. Fig. 3 shows the simulated far-field radiation patterns of the proposed antenna in the xz-plane and the yz-plane for both EF and Eu at frequencies of 2.56, 3.6 and 5.36 GHz. It can be seen that the electric field Eu always keeps an eight-shaped radiation pattern and the electric field EF holds nearly a omnidirectional radiation pattern, which show that the antenna exhibits dipole-like radiation characteristic. Finally, the peak gain is shown in Fig. 4. For the operating band of 2.4– 2.69 GHz, the peak gain of the antenna varies from 1.2 to 2.29 dB, and for the medium band of 3.4– 3.69 GHz, the antenna gain level is 0.38– 0.9 dB. Results in the upper band of 5.15– 5.85 GHz show that the gain variation is from 1.25 to 3.45 dB.
and reasonable gain. This indicates that the proposed antenna is well suited for WiFi/WiMAX portable units and mobile handsets. # The Institution of Engineering and Technology 2012 15 December 2011 doi: 10.1049/el.2011.3692 One or more of the Figures in this Letter are available in colour online. Ping Wang, Guang-Jun Wen, Yong-Jun Huang and Yuan-Hua Sun (Centre for RFIC and System Technology, School of Communication and Information Engineering, University of Electronic Science and Technology, Chengdu 610054, People’s Republic of China) E-mail:
[email protected]
2.4–2.69GHz 3.4–3.69GHz
Ping Wang: Also with the College of Electronic and Information Engineering, Chongqing Three Gorges University, Chongqing 404000, China
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Conclusion: A compact planar monopole antenna for WiFi/WiMAX applications is presented. By employing three different types of structures – two I-shaped notched slots, an open-ended U-shaped slot and two symmetrical meander microstrip-lines – three operating bands (2.4 – 2.63, 3.23– 3.8, 5.15 – 5.98 GHz) can be achieved. Moreover, the proposed antenna has several advantages, such as smaller size, better performance of interference suppression, excellent radiation patterns,
1 Pan, C.Y., Horng, T.S., Chen, W.S., and Huang, C.H.: ‘Dual wideband printed monopole antenna for WLAN/WiMAX applications’, IEEE Antennas Propag, Lett., 2007, 6, pp. 149–151 2 Thomas, K.G., and Sreenivasan, M.: ‘Compact triple band antenna for WLAN/WiMAX applications’, Electron. Lett., 2009, 45, (16) 3 Hu, L., and Hua, W.: ‘Wide dual-band CPW-fed slot antenna’, Electron. Lett., 2011, 47, (14) 4 Yang, K., Wang, H., Lei, Z., Xie, Y., and Lai, H.: ‘CPW-fed slot antenna with triangular SRR terminated feedline for WLAN/WiMAX applications’, Electron. Lett., 2011, 47, (12) 5 Chaimool, S., and Chung, K.L.: ‘CPW-fed mirrored-L monopole antenna with distinct triple bands for WiFi and WiMAX applications’, Electron. Lett., 2009, 45, (18) 6 Chung, K.L., and Chaimool, S.: ‘Triple-band CPW-fed L-shaped monopole antenna with small ground plane’, Micow. Opt. Technol. Lett., 2011, 53, (10), pp. 2274– 2277
ELECTRONICS LETTERS 29th March 2012 Vol. 48 No. 7
