Proceedings of iWEM2014, Sapporo, Japan
A low-profile dipole array antenna for on-body communications Joongki Park, Jinpil Tak, Jaehoon Choi Department of Electronics and Computer Engineering Hanyang University Seoul, Korea
[email protected],
[email protected] Abstract— In this paper, a low-profile dipole array antenna for on-body communications in wireless body area network (WBAN) is proposed. The proposed antenna consists of eight planar dipole antenna elements. To obtain the monopole-like radiation pattern, eight dipole elements are placed symmetrically around z-axis. The simulated 10-dB return loss bandwidth of the antenna is wide enough to cover the 2.45 GHz industrial, scientific, and medical (ISM) band. The proposed antenna has monopole-like radiation pattern with very thin thickness of only 1.6 mm.
II.
A. Antenna design Fig. 1 shows the proposed antenna structure. The antenna is designed on a FR4 (εr = 4.4, tanδ = 0.0245) substrate with thickness of 1.6 mm. The antenna has a dimension of 55 mm × 55 mm × 1.6 mm. The dipole antenna has a directional radiation pattern toward horizontal direction. Therefore, the array of the eight dipole antennas has a monopole-like radiation pattern. To reduce the human body effect, the proposed antenna is designed with ground.
Keywords—Low-profile; Monopole-like radiation pattern; Onbody;
I.
ANTENNA DESIGN AND SIMULATION RESULTS
INTRODUCTION
Recently, the interest on Wireless Body Area Network (WBAN) system has been increased due to its applicability in various services. Depending on the location of transceiver on the human body, WBAN system can be categorized as offbody, on-body, and in-body [1]. In order to obtain a good onbody communication channel between two on-body devices, an antenna is required to have a radiation characteristic like that of a vertical monopole antenna. However, monopole antenna is not suitable for on-body utilization owing to its large vertical size [2]. Therefore the low-profile antenna with the monopolelike radiation characteristic is needed for on-body communication. In order to establish low-profile antenna with the monopole-like radiation pattern, several types of patch antennas using various resonance modes have been proposed [3]-[4]. In [3], a microstrip monopolar patch antenna using TM01 and TM02 resonance modes was suggested. A circular patch-ring antenna with TM02 mode was proposed in [4]. However, these antennas require large horizontal substrate to achieve the desired antenna performance.
(a) Concept of the proposed antenna
In this paper, a low-profile dipole array antenna is proposed for on-body communication to accomplish low-profile and omnidirectional radiation. The designed antenna operates in the 2.45 GHz industrial, scientific, and medical (ISM) band with monopole-like radiation characteristic. The performance of the proposed antenna is verified when it is attached on a two third muscle-equivalent phantom.
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(b) Top view Fig. 1: Configuration of the proposed antenna.
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Fig. 4 shows the simulated radiation patterns of the proposed antenna. The antenna has omnidirectional radiation pattern similar to that of vertical monopole at 2.45 GHz ISM band for on-body communications. The simulated peak gain is 1.73 dBi. III.
CONCLUSTION
In this paper, a low-profile dipole array antenna with monopole-like radiation pattern for on-body communications is proposed. To attain monopole-like radiation pattern with lowprofile, the antenna used the array of eight dipole antennas. The antenna has a vertical monopole-like radiation pattern in 2.45 GHz ISM (2.4-2.485 GHz) band. Thus the proposed antenna is a good candidate for on-body communication devices.
Fig. 2: Simulation setup with body phantom.
Fig. 2 illustrates the simulation setup for the proposed antenna on a phantom. The proposed antenna is placed 15mm away from the surface of the two third muscle equivalentphantom (εr = 35.5, σ = 1.2 S/m). The phantom has a dimension of 200 mm × 200 mm × 70 mm.
ACKNOWLEDGMENT
B. Simulation results Fig. 3 shows the comparison between the simulated return loss characteristic of the proposed antenna in free space and on the phantom. The resonance frequency of the proposed antenna slightly shifts toward low frequency side due to the phantom effect. The 10-dB return loss bandwidth of the proposed antenna is wide enough to cover the whole ISM (2.4-2.485 GHz) band.
This research was funded by the MSIP(Ministry of Science, ICT & Future Planning), Korea in the ICT R&D Program 2013, and in part by the National Research Foundation of Korea (NRF) Grant funded by the Korean government (MEST) (no. 2010-0017934). REFERENCES [1] [2] [3]
[4]
Fig. 3: Simulated return loss characteristic of the proposed antenna.
Fig. 4: Simulated radiation patterns of the proposed antenna on the phantom at 2.45 GHz.
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P. S. Hall, Y. Hao, Antennas and Propagation for Body- centric Wireless Communications, Artech House, Norwood, pp. 1-64, 2006. W. L. Stutzman, G. A. Thiele, Antenna Theory and Design, John Wiley & Sons, pp. 59-66, 1998.. J. Liu, Q. Xue, H. Wong, H. Lai, and Y. Long, “Design and analysis of a low-profile and broadband microstrip monopolar patch antenna,” IEEE Trans. Antennas Propag., vol. 61, no. 1, pp. 11-18, Jan. 2013. A. Al-Zoubi, F. Yang, and A. Kishk, “A Broadband Center-Fed Circular Patch-Ring Antenna With a Monopole Like Radiation Pattern,” IEEE Trans. Antennas Propag., vol. 57, no. 3, pp. 789-792. Mar. 2009.
