A Compact UWB Antenna for On-Body Applications - IEEE Xplore

IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 59, NO. 4, APRIL 2011

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A Compact UWB Antenna for On-Body Applications Nacer Chahat, Student Member, IEEE, Maxim Zhadobov, Member, IEEE, Ronan Sauleau, Senior Member, IEEE, and Koichi Ito, Fellow, IEEE

Abstract—A new compact planar ultrawideband (UWB) antenna designed for on-body communications is presented. The antenna is characterized in free space, on a homogeneous phantom modeling a human arm, and on a realistic high-resolution whole-body voxel model. In all configurations it demonstrates very satisfactory features for on-body propagation. The results are presented in terms of return loss, radiation pattern, efficiency, and E -field distribution. The antenna shows very good performance within the 3–11.2 GHz range, and therefore it might be used successfully for the 3.1–10.6 GHz IR-UWB systems. The simulation results for the return loss and radiation patterns are in good agreement with measurements. Finally, a time-domain analysis over the whole-body voxel model is performed for impulse radio applications, and transmission scenarios with several antennas placed on the body are analyzed and compared. Index Terms—Body-area network (BAN), body-centric wireless communications, compact antenna, printed antenna, ultrawideband (UWB) antenna.

I. INTRODUCTION

B

ODY-AREA NETWORKS (BAN) are wireless communication systems that enable communications between wearable and/or implanted into the human body electronic devices. Such systems are of great interest for various applications including sport, multimedia, health care, and military applications [1], [2]. Ultrawideband (UWB) antennas have been identified as a highly promising solution for BAN. One of the major advantages of the UWB systems at 3.1–10.6 GHz is their high data-rate-transmission capabilities (typically 100 Mbps) with low power spectral densities ( 41.3 dBm/MHz) [3], ensuring thereby low interference with other narrow-band wireless devices. Designing an antenna for UWB body-centric communications is a challenging task, as the antenna needs to fulfill several fundamental requirements, such as: 1) optimized characteristics in frequency-and time-domains; 2) small size and low profile; 3) good on-body propagation. Indeed, both frequency-and time-domain responses should be considered and characterized [4]–[7], and the interaction with the human body, i.e., the changes in the antenna performance Manuscript received April 12, 2010; revised August 04, 2010; accepted September 24, 2010. Date of publication January 28, 2011; date of current version April 06, 2011. This work was supported in part by the “Agence Nationale de la Recherche” (ANR), France by Grants ANR-09-VERS-003 (METAVEST project) and ANR-09-RPDOC-003-01 (Bio-CEM project), “Région Bretagne” (Dose_ULB project), and in part by the “Centre National de la Recherche Scientifique” (CNRS), France. N. Chahat, M. Zhadobov, and R. Sauleau are with the Institute of Electronics and Telecommunications of Rennes (IETR), UMR CNRS 6164, University of Rennes 1, 35042 Rennes, France (e-mail: [email protected]). K. Ito is with the Graduate School of Engineering, Chiba University, Chiba 263-8522, Japan (e-mail: [email protected]). Digital Object Identifier 10.1109/TAP.2011.2109361

due to the presence of the body and power losses in the tissues, should be carefully taken into account [8]. Besides, the miniaturization of UWB antennas is particularly important for wearable applications. Significant research efforts have been undertaken to reduce the size of the radiating structures, and some interesting miniaturization techniques have been proposed [9]–[11]. Finally, for on-body applications, the antenna needs to exhibit suitable on-body propagation features. However, in most of the proposed body-centric UWB communication scenarios, omnidirectional planar antennas are placed parallel to the human body, and, as a result, the efficiency of these antennas is significantly reduced [12], and the on-body propagation is not optimal. Indeed, this configuration is more suitable for off-body communication, i.e., for communication between an antenna mounted on the body and a remote device or base station, as demonstrated in several studies introducing textile antennas with high potential for off-body communications [13]–[15]. It was shown that the antenna -field polarization needs to be normal to the body surface in order to improve the on-body propagation [16]. In particular, it was demonstrated that a quarter-wavelength monopole antenna is appropriate for on-body communication for the following reasons: 1) it has an omnidirectional pattern with maximum radiation along the body surface; 2) -field is normal to the body surface [16]. Furthermore, a comparison between two different UWB antennas has been performed showing that the planar inverted cone antenna (PICA) with an omnidirectional monopole-like pattern demonstrates very good performances for on-body communications [17]. Nevertheless, the quarter-wavelength monopole antenna and the PICA have a relatively large ground plane and heights. To overcome this problem we introduce here a reduced-size UWB antenna suitable for on-body communications since the -field is polarized perpendicularly to the body surface. This paper is organized as follows. The antenna design and a two-thirds muscle equivalent phantom used for numerical and experimental characterizations are introduced in Section II. The main characteristics of the proposed antenna, namely its reflection coefficient, radiation patterns, and efficiency are then given in Section III. Experimental results, obtained using the phantom, are also compared to calculations. In addition, the -field distribution around a homogeneous arm model and whole-body voxel phantom is also studied numerically to investigate the on-body propagation. Finally the time-domain capabilities of the antenna are analyzed in Section IV, transmission scenarios between several antennas placed on the body are numerically studied, and the effect of modulation schemes on the on-body system performance is discussed. All calculations are carried out using the finite integration technique implemented in CST Microwave Studio.

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Fig. 2. Reflection coefficients S of the proposed antenna simulated in free space for different slot shapes. Three values for the total slot length are considered: 6.9 mm, 11.9 mm, and 16.4 mm.

Fig. 1. (a) Geometry of the proposed antenna. (b) Antenna on the two-thirds muscle-equivalent phantom.

Fig. 3. Reflection coefficient S different ground plane heights. . 111111g .

10 mm

= 15 mm

of the proposed antenna in free space for . g . g

g

= 1 mm

= 5 mm

=

II. EXPERIMENTAL MODELS A. Antenna Design An antenna was designed and manufactured for UWB on-body applications. It consists of a compact microstrip-fed printed monopole [Fig. 1(a), ] printed on a 1.6-mm-thick AR350 substrate . In this study, the antenna performance is evaluated and optimized in the following configurations: 1) antenna located on a homogeneous phantom with two-thirds muscle-equivalent dielectric properties; 2) antenna mounted on a high-resolution nonhomogeneous human body model (Sections III-C, III-E, and IV). To our best knowledge, the smallest UWB antennas have a significant height (around 17 mm) [18]–[21] and thus might be not suitable for a perpendicular configuration ( -field normal to the body). Here, the ground plane size and radiator height have been reduced by 8 mm and 7 mm, respectively, leading to a total antenna height of only 10 mm. This choice enables us to minimize distortions in the antenna performance compared to the original design [22]. This size reduction results in a significant decrease of the current path, thus in an increase of the lower band limit. To decrease the lower frequency, one solution consists in extending the total slot length (white dotted line in Fig. 1(a)). The impact of this slot length is illustrated in Fig. 2 where we compare the reflection coefficients for three slot length values: 6.9 mm, 11.9 mm, and 16.4 mm. Selecting a long slot enables to slightly enlarge the 10 dB return loss bandwidth and cover the full UWB frequency range (solid line in Fig. 2).

TABLE I CROSS POLARIZATION LEVELS, PEAK GAINS, AND EFFICIENCY FOR THE PROPOSED ANTENNA WITH GROUND PLANE HEIGHT OF 1 mm/10 mm

As a wearable antenna, the antenna ground plane is voluntarily small to minimize the antenna height. The impact of the ground plane size on the reflection coefficient is illustrated in Fig. 3. Although slightly degraded around 4 and remains below 10 dB between these two 10 GHz, the frequencies for larger ground plane dimensions. Furthermore, the antenna size reduction (and particularly, the small ground plane), affects the cross-polarization component and peak gain (Table I). However, along the body surface (i.e., and ), the cross-polarization ratio remains below 10 dB. B. Phantom The human arm is modeled as a two-thirds muscle-equivalent phantom, and the antenna is located 1 mm above [Fig. 1(b) and Fig. 4]. This phantom has a parallelepipedic shape . A water-based semisolid phantom

CHAHAT et al.: COMPACT UWB ANTENNA FOR ON-BODY APPLICATIONS

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Fig. 4. Antenna prototype mounted on the two-thirds muscle-equivalent phantom.

[23] was chosen as a tissue-equivalent model for UWB measurements. The complex permittivity and conductivity of the phantom are adjusted using the polyethylene powder and sodium chloride, respectively. Agar is used to maintain the shape of the phantom, sodium azide is a preservative, and TX-151 improves the phantom stickiness [23].

Fig. 5. Measured and computed characteristics of the phantom. Measurement. Calculation.

Target.

III. FREQUENCY-DOMAIN ANALYSIS In this section, the dielectric properties of the phantom are provided in the 3–11 GHz range. Then computational and measured results are presented for the antenna return loss and radiation pattern. Finally, -field distributions are computed for the arm and human body models. A. Numerical Model and Dielectric Properties of the Phantom in the UWB Band

Fig. 6. Simulated reflection coefficients of the optimized antenna (the total slot Antenna in free space. Antenna mounted on length equals 16.4 mm). the phantom.

In order to model accurately the antenna in presence of the phantom, the dielectric properties of the phantom should be determined carefully in the 3.1–10.6 GHz range. Two-thirds of the muscle permittivity was used as a target value for the phantom. The muscle dielectric properties are well characterized up to 20 GHz [24]. For the numerical modeling, the complex dielectric permittivity of the phantom is expressed as a Debye’s dispersion equation [25] (1) where is the angular frequency, is the static permittivity, is the optical permittivity, and is the relaxation time. The best fit of this theoretical model to the target values was obtained for , , and . Theoretical permittivity and conductivity model is in a very good agreement with target values over the considered frequency range (3–11 GHz), confirming thereby that the choice of the Debye model is appropriate (Fig. 5). The phantom has been built as explained in Section II-B and characterized using the dielectric probe kit 85070E (Agilent Tech., CA). The measured complex permittivity is in satisfactory agreement with the numerical results (Fig. 5). B. Reflection Coefficient and Impact of the Feed Connector of the proposed UWB anThe reflection coefficients tenna are represented in Fig. 6 assuming the antenna is either in free space or on the arm. Here, the numerical models do not take into account the feed connector. These results show is very slightly affected by the presence of the that the

Fig. 7. Reflection coefficient of the antenna with feed connector mounted on Simulation results. Measurements. the phantom.

phantom and remains below 10 dB within the 3–11.3 GHz range. The fabricated prototype is fed by a tiny coaxial probe connector (BL58-3123-00, Orient Microwave Corp., Japan). Its reflection coefficient measured for the antenna mounted on the phantom is represented in Fig. 7. The agreement with simulations (accounting this time for the feed connector) is very satisfactory. The 10 dB return loss bandwidth almost covers the full 3.1–10.6 GHz UWB frequency range. C. Radiation Patterns and The antenna radiation patterns in planes have been computed at three frequency points (4, 7, and 10 GHz) for three configurations: antenna alone, antenna on the phantom, and antenna on the whole-body model (Duke model from Virtual Family [26]). Duke represents a 34 year-old 174 cm-tall adult weighting 70 kg. Compared to the free-space scenario, the antenna mounted on the phantom shows

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Fig. 8. Measured and simulated radiation patterns at 4, 7, and 10 GHz. (a) voxel phantom.

= 90

. (b) '

=0

.

Free space.

On homogeneous phantom.

On

Measurement.

TABLE II PEAK AND AVERAGE GAINS OF THE ANTENNA IN FREE SPACE AND ON THE PHANTOM

which corresponds to a practical situation where the antenna is mounted on clothes. However, the antenna efficiency can be improved using a larger ground plane size as shown in Table I. E. Computed E-Field Distributions

better front-to-back ratio. This is essentially related to the absorption in and reflections from the phantom. In addition, comand parison with measurements at 4 and 10 GHz in the planes using the two-thirds muscle-equivalent phantom confirms the very satisfactory matching between experimental and numerical results. The average and peak values of the antenna gain are given in Table II. These data confirm the gain plane due to the presence of the phantom, as reduction in already mentioned in other studies (e.g. [27], [28]). However, plane, the gain is reduced at 4 GHz where absorptions in are higher, and at 7 and 10 GHz, the gain increases due to the reflection caused by the arm. D. Radiation Efficiency Radiation efficiencies of 19.1%, 38.2%, and 28.4% are estimated on the homogeneous phantom, at 4, 7, and 10 GHz, respectively. As expected, the radiation efficiency is quite low since the gap between the antenna and the body is set to 1 mm,

To estimate possible range of application scenarios for the proposed antenna, it is important to consider electromagnetic field distribution in, on, and around the body. Fig. 9 shows the computed electric field distributions in the plane in cross-section plane of the numerical arm model [ Fig. 1(b)] at 4, 7, and 10 GHz. It is important to highlight that, component is the dominant one, in this configuration, the which means that the major contribution to the overall electric field comes from the component perpendicular to the upper side of the phantom. Based on these results, several observations can be made: • The electromagnetic field propagates along the phantom surface and, as expected, attenuates nonlinearly; • Within the considered frequency range, higher frequencies correspond to the more localized energy absorption. The field propagation around the body is analyzed in Fig. 10 using Duke model (the spatial resolution is ). The antenna is mounted on the left arm where most part of the electric field is confined. Fig. 10 shows that the electromagnetic field propagates in both directions along the left arm and that shadowing due to the human body plays a key role since the electric field is much stronger at the source side compared to the opposite side (the attenuation is at least 70 dB). Therefore, communications between antennas situated on opposite sides of the body might be difficult in this configuration. However, wireless radio links between hand/head or hand/foot are absolutely


Fig. 9. Electric field distributions (root-sum-square) in x

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0 y cross section of a homogeneous model.

Fig. 10. Electric field distribution around and within the Duke model at 4, 7, and 10 GHz.

achievable, and the time-domain behavior for such communication scenarios is studied in Section IV. IV. PROPAGATION AROUND THE BODY A. Time-Domain Analysis A UWB system can be either a traditional pulse-based system transmitting each pulse that occupies the entire UWB bandwidth, or a carrier system such as, for instance, multiband orthogonal frequency-division multiplexing (MB-OFDM) which has been adopted by WiMedia. Time-domain analyses

are of great importance to evaluate the capabilities of UWB antennas for impulse radio systems (IR-UWB). A UWB antenna excited by nanosecond pulses behaves as a pulse-shaping filter. Therefore, a suitable antenna for UWB communications has to demonstrate minimum distortion of the pulse in time-domain to reduce the complexity of the detection mechanisms at the receiver terminal. The quality of the received pulse is determined by (2)

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Fig. 11. (a) Normalized excitation signal. (b) Its spectral density.

Fig. 13. (a) Signals monitored by virtual probes. (b) Their spectra.

Fig. 12. Locations of the probes around the antenna.

where the source pulse and received pulse are normalized by their respective energies. The source pulse signal chosen here [Fig. 11(a)] is a fifthorder derivative Gaussian pulse satisfying the FCC power mask [Fig. 11(b)]

(3) where and denote the amplitude and spread of the Gaussian pulse, respectively. In the numerical simulations, the output signal is monitored in three directions using three probes located 50 cm apart from the antenna (Fig. 12). The pulse received at each is excellent: probe is represented in Fig. 13(a). Its fidelity 98.8%, 98.3%, and 95.2% for probes A, B, and C, respectively. A similar study has been conducted for on-body propagation. To this end, three transmission scenarios between four antennas are considered: the transmitting antenna is mounted on the left

wrist (TX1), the three receiving antennas are placed on the left arm (RX1), left ear (RX2), and left leg (RX3) (Fig. 14). The distortion of the received pulses (Fig. 15) depends on the antenna position, and their fidelity equals 75%, 46%, and 81%, for RX1, RX2, and RX3, respectively. The most pronounced distortion is observed for the antenna on the head, suggesting that a direct communication in this scenario might be delicate. From these results, it is clear that pulses experience strong distortions in on-body scenarios. The signal fidelity can be very low (e.g., 46% for RX2), and therefore an appropriate modulation scheme needs to be implemented. For instance binary phase-shift keying (BPSK) is not appropriate in this case because of strong distortions of the transmitted signal. However, in IR-UWB systems, pulse-position modulation (PPM) and on-off keying (OOK) are excellent candidates for on-body communications. These two modulation schemes can be implemented with noncoherent receivers using energy detection mechanisms instead of correlation for coherent systems. With a noncoherent receiver, the pulse shape is secondary and the low fidelity can be overcome. We focus our attention here on IR-UWB system using the entire UWB-band. However, these modulations schemes can also be used as multiband schemes [29], [30].


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Fig. 16. Path loss of the proposed antenna mounted on the homogeg . neous phantom with different ground plane heights. g .

= 10 mm

222

= 1 mm

TABLE III MEAN PATH GAIN AND PATH GAIN VARIABILITY (RANGE) FOR SOME SPECIFIC ON BODY PATH LOSS

Fig. 14. Transmission scenario with four antennas mounted on the body.

efficiency (Table I) and as consequences the path loss becomes higher. The propagation path loss for this on-body scenario is presented in Table III. The mean path gain and variability within the 3.1–10.6 GHz UWB band are given for all receiving antennas. The wrist-to-arm link, being the shortest, has the lower loss, with an average loss of 53.9 dB, and has a peak-to-peak variation of approximately 32.9 dB within the whole UWB frequency band. The wrist-to-head link has the higher average loss, (this is mainly due to the longer link length), and its path loss variability is estimated around 34.4 dB. In the wrist-to-calf link, an average loss of 60.5 dB is evaluated, and the variability is much lower compared to the other links.

Fig. 15. Wave forms of the received pulses.

B. On-Body Propagation As a non-coherent receiver is preferred, the path loss needs to be investigated. The path loss of the proposed antenna mounted on the homogeneous phantom with two different ground plane heights is presented in Fig. 16. For each distance, each point represents the path loss result at one frequency point. The antenna with a 10-mm-height ground plane demonstrates a better on-body propagation performance. Using a larger ground plane improves the path loss by 7 dB whereas the cross-polarization component remains fairly the same between these two antenna models. However a larger ground plane improves the antenna

V. CONCLUSION A compact planar UWB monopole antenna has been designed for on-body communications. The antenna shows good impedance matching and satisfactory on-body propagation features. It was shown that, in spite of the small distance between the antenna and the body, the latter does not affect significantly the antenna input matching. The reflection coefficient and radiation patterns were successfully measured using a two-thirds muscle homogeneous phantom. The electric field distributions around a realistic whole-body model have been computed at different frequencies, and suitable on-body propagation features have been highlighted. Compared to the parallel configuration, the perpendicular one demonstrates higher gain, better on-body propagation, and the antenna impedance performance is less affected. The time-domain behavior of the proposed antenna has been fully investigated on a realistic body model. Significant pulse distortions have been observed and thus a noncoherent modulation is advised for on-body communication. Hence, for

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IR-UWB systems, PPM and OOK are excellent solutions for on-body scenarios. Finally, excellent path gain results have been demonstrated for specific transmission scenarios with several antennas placed on the body. ACKNOWLEDGMENT The authors would like to thank all members of Prof. Ito and Prof. Takahashi laboratory (Chiba University, Chiba, Japan) and especially Prof. K. Saito, Basari, N. Haga, and R. Watanabe for their kind assistance in measurements. REFERENCES [1] P. S. Hall and Y. Hao, Antennas and Propagation For Body Centric Communications Systems. Norwood, MA: Artech House, 2006, 10: 1-58053-493-7. [2] P. S. Hall and Y. Hao, “Antennas and propagation for body centric communications,” in Proc. First Eur. Conf. Antennas Propag., Nice, France, Nov. 6–10, 2006. [3] Federal Communication Commission, First Rep. Order Feb. 14, 2002. [4] Z. N. Chen, Antennas for Portable Devices. Hoboken, NJ: Wiley, 2007, 10: 0470030739. [5] X. N. Low, Z. N. Chen, and T. S. P. See, “A UWB dipole antenna with enhanced impedance and gain performance,” IEEE Trans. Antennas Propag., vol. 57, no. 10, pp. 2959–2966, Oct. 2009. [6] A. Alomainy, A. Sani, A. Rahman, J. G. Santas, and Y. Hao, “Transient characteristics of wearable antennas and radio propagation channels for ultrawideband body-centric wireless communications,” IEEE Trans. Antennas Propag., vol. 57, no. 4, pp. 875–884, Apr. 2009. [7] S. Chamaani and S. A. Mirtaheri, “Planar UWB monopole antenna optimization to enhance time-domain characteristics using PSO,” in Proc. Int. Symp. Antenna Propag. (ISAP 08), 2008, pp. 553–556. [8] W. T. Chen and H. R. Chuang, “Numerical computation of human interaction with arbitrarily oriented superquadric loop antennas in personal communications,” IEEE Trans. Antennas Propag., vol. 46, no. 6, pp. 821–828, Jun. 1998. [9] K. Bahadori and Y. Rahmat-Samii, “A miniaturized elliptic-card UWB antenna with band rejection for wireless communications,” IEEE Trans. Antennas Propag., vol. 55, no. 11, pp. 3326–3332, Nov. 2007. [10] A. M. Abbosh, “Miniaturization of planar ultrawideband antenna via corrugation,” IEEE Antennas Wireless Propag. Lett., vol. 7, pp. 685–688, 2008. [11] A. M. Abbosh, “Miniaturized microstrip-fed tapered-slot antenna with ultrawideband performance,” IEEE Antennas Wireless Propag. Lett., vol. 8, pp. 690–692, 2009. [12] M. Klemm and G. Troester, “EM energy absorption in the human body tissues due to UWB antennas,” Progress in Electromagn. Res., vol. 62, pp. 261–280, 2006. [13] C. Hertleer, H. Rogier, L. Vallozzi, and L. Van Langenhove, “A textile antenna for off-body communication integrated into protective clothing for firefighters,” IEEE Trans. Antennas Propag., vol. 57, no. 4, pp. 919–925, Apr. 2009. [14] C. Hertleer, H. Rogier, and L. Van Langenhove, “A textile antenna for protective clothing,” in Proc. IET Seminar on Antennas and Propag. Body-Centric Wireless Commun., Apr. 2007, pp. 44–46. [15] C. Hertleer, A. Tronquo, H. Rogier, L. Vallozzi, and L. Van Langenhove, “Aperture-coupled patch antenna for integration into wearable textile systems,” IEEE Antennas Wireless Propag. Lett., vol. 6, pp. 392–395, 2007. [16] P. S. Hall, Y. Hao, Y. I. Nechayev, A. Alomainy, C. C. Constantinou, C. Parini, M. R. Kamarudin, T. Z. Salim, D. T. M. Hee, R. Dubrovke, A. S. Owadally, W. Song, A. Serra, P. Nepa, M. Gallo, and M. Bozzetti, “Antennas and propagation for on-body communication systems,” IEEE Antennas Propag. Mag., vol. 49, no. 3, pp. 41–58, Jun. 2007. [17] A. Alomainy, Y. Hao, C. G. Parini, and P. S. Hall, “Comparison between two different antennas for UWB on-body propagation measurements,” IEEE Antennas Wireless Propag. Lett., vol. 4, pp. 31–34, 2005. [18] M. Sun and Y. P. Zhang, “A chip antenna in LTCC for UWB radios,” IEEE Trans. Antennas Propag., vol. 56, no. 4, pp. 1177–1180, Apr. 2008. [19] Q. Ye, Z. N. Chen, and T. S. P. See, “Miniaturization of small printed UWB antenna for WPAN applications,” in IEEE Int. Workshop on Antenna Technol. (iWAT), Mar. 2–4, 2009, pp. 1–4.

[20] L. Guo, S. Wang, Y. Gao, X. Chen, and C. Parini, “Miniaturisation of printed disc UWB monopoles,” in Proc. Int. Workshop on Antenna Technol.: Small Antennas and Novel Metamater. (iWAT), Mar. 4–6, 2008, pp. 95–98. [21] M. Sun and Y. P. Zhang, “Miniaturization of planar monopole antennas for ultrawide-band applications,” in Proc. Int. Workshop on Antenna Technol.: Small and Smart Antennas Metamater. Appl. (IWAT), Mar. 21–23, 2007, pp. 197–200. [22] Z. N. Chen, T. S. P. See, and X. M. Qing, “Small printed ultrawideband antenna with reduced ground plane effect,” IEEE Trans. Antennas Propag., vol. 55, no. 2, pp. 383–388, Feb. 2007. [23] Y. Okano, K. Ito, I. Ida, and M. Takahashi, “The SAR evaluation method by a combination of thermographic experiments and biological tissue-equivalent phantoms,” IEEE Trans. Microw. Theory Tech., vol. 48, no. 11, pt. 2, pp. 2094–2103, Nov. 2000. [24] S. Gabriel, R. W. Lau, and C. Gabriel, “The dielectric properties of biological tissues: II. Measurements in the frequency range 10 Hz to 20 GHz,” Phys. Med. Biol., vol. 41, pp. 2251–2269, 1996. [25] O. G. Martinsen, S. Grimmes, and H. P. Schwan, “Interface phenomena and dielectric properties of biological tissue,” in Encyclopedia of Surface and Collied Science. New York: Marcel Dekker, 2002. [26] IT’IS Foundation, The Virtual Family [Online]. Available: http://www. itis.ethz.ch/index/index_humanmodels.html [27] A. Cai, T. S. P. See, and Z. N. Chen, “Study of human head effects on UWB antenna,” in Proc. IEEE Int. Workshop on Antenna Technol.: Small Antennas and Novel Metamater. (IWAT), Mar. 7–9, 2005, pp. 310–313. [28] Z. N. Chen, A. Cai, T. S. P. See, and M. Y. W. Chia, “Small planar UWB antennas in proximity of the human head,” IEEE Trans. Microw. Theory Tech., vol. 54, no. 4, pp. 1846–1857, Jun. 2006. [29] S. Woods and S. Aiello, Essentials of UWB. Cambridge, U.K.: Cambridge Univ. Press, 2008, 10: 0521877830. [30] S. Hernandez and R. Kohno, “Ultra low power UWB transceiver design for body area networks,” in Proc. Biomed. Commun. Technol. Int. Symp., Nov. 24–27, 2009, pp. 1–4. Nacer Chahat (S’09) was born in Angers, France, in 1986. He graduated in electrical engineering and radio communications from the Ecole Supérieur d’ingénieur de Rennes (ESIR) and received the Master’s degree in telecommunication and electronics in 2009. Since 2009, he has been working toward the Ph.D. degree at the Institute of Electronics and Telecommunications of Rennes (IETR), University of Rennes 1, Rennes, France. His current research fields are electrically small antennas, millimeter-wave antennas, and the evaluation of the interaction between the electromagnetic field and human body. In 2009, he accomplished a six-month Master’s training period as a special research student at the Graduate School of Engineering, Chiba University, Chiba, Japan.

Maxim Zhadobov (S’05–M’07) was born in Gorky, Russia, in 1980. He received the M.S. degree in radiophysics from Nizhni Novgorod State University, Nizhni Novgorod, Russia, in 2003, and the Ph.D. degree in bioelectromagnetics from the Institute of Electronics and Telecommunications of Rennes (IETR), University of Rennes 1, Rennes, France, in 2006. He accomplished Postdoctoral training with the Center for Biomedical Physics, Temple University, Philadelphia, PA, in 2008, and then rejoined IETR as an Associate Scientist with the Centre National de la Recherche Scientifique (CNRS). He has authored or coauthored more than 50 scientific contributions. His main scientific interests are in the field of biocompatibility of electromagnetic radiations, including interactions of microwaves, millimeter waves and pulsed radiations at the cellular and subcellular levels, health risks and environmental safety of emerging wireless communication systems, biocompatibility of wireless noninvasive biomedical techniques, therapeutic applications of nonionizing radiations, bioelectromagnetic optimization of body-centric wireless systems, experimental, and numerical electromagnetic dosimetry. Dr. Zhadobov was the recipient of the 2005 Best Poster Presentation Award from the International School of Bioelectromagnetics, the 2006 Best Scientific Paper Award from the Bioelectromegnetics Society, and Brittany’s Young Scientist Award in 2010.


Ronan Sauleau (M’04–SM’06) graduated in electrical engineering and radio communications from the Institut National des Sciences Appliquées, Rennes, France, in 1995. He received the Agrégation degree from the Ecole Normale Supérieure de Cachan, France, in 1996, and the Doctoral degree in signal processing and telecommunications and the “Habilitation à Diriger des Recherche” degree from the University of Rennes 1, France, in 1999 and 2005, respectively. He was an Assistant Professor and Associate Professor with the University of Rennes 1, between September 2000 and November 2005, and between December 2005 and October 2009. He has been a full Professor with the same University since November 2009. His current research fields are numerical modeling (mainly FDTD), millimeter-wave printed and reconfigurable (MEMS) antennas, lens-based focusing devices, periodic and nonperiodic structures (electromagnetic bandgap materials, metamaterials, reflectarrays, and transmitarrays), and biological effects of millimeter waves. He has received four patents and is the author or coauthor of 70 journal papers Dr. Sauleau has more than 180 contributions to national and international conferences and workshops. He received the 2004 ISAP Conference Young Researcher Scientist Fellowship (Japan) and the first Young Researcher Prize in Brittany, France, in 2001 for his research work on gain-enhanced Fabry-Perot antennas. In September 2007, he was elevated to Junior member of the “Institut Universitaire de France.” He was awarded the Bronze medal by CNRS in 2008.

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Koichi Ito (M’81–SM’02–F’05) received the B.S. and M.S. degrees from Chiba University, Chiba, Japan, in 1974 and 1976, respectively, and the D.E. degree from the Tokyo Institute of Technology, Tokyo, Japan, in 1985, all in electrical engineering. From 1976 to 1979, he was a Research Associate at the Tokyo Institute of Technology. From 1979 to 1989, he was a Research Associate with Chiba University. From 1989 to 1997, he was an Associate Professor with the Department of Electrical and Electronics Engineering, Chiba University, and is currently a Professor with the Department of Medical System Engineering, Chiba University. From 2005 to 2009, he was Deputy Vice-President for Research, Chiba University. From 2008 to 2009, he was Vice-Dean of the Graduate School of Engineering, Chiba University. Since April 2009, he has been Director of Research Center for Frontier Medical Engineering, Chiba University. In 1989, 1994, and 1998, he visited the University of Rennes I, France, as an Invited Professor. His main research interests include analysis and design of printed antennas and small antennas for mobile communications, research on evaluation of the interaction between electromagnetic fields and the human body by use of numerical and experimental phantoms, microwave antennas for medical applications such as cancer treatment, and antennas for body-centric wireless communications. Dr. Ito is a Fellow of the Institute of Electronics, Information and Communication Engineers (IEICE) of Japan, a member of the American Association for the Advancement of Science, the Institute of Image Information and Television Engineers of Japan (ITE) and the Japanese Society for Thermal Medicine. He served as Chair of the Technical Group on Radio and Optical Transmissions, ITE from 1997 to 2001, Chair of the Technical Committee on Human Phantoms for Electromagnetics, IEICE from 1998 to 2006, Chair of the IEEE AP-S Japan Chapter from 2001 to 2002, TPC Co-Chair of the 2006 IEEE International Workshop on Antenna Technology (iWAT2006), Vice-Chair of the 2007 International Symposium on Antennas and Propagation (ISAP2007) in Japan, General Chair of iWAT2008, Co-Chair of ISAP2008, and an AdCom member for the IEEE AP-S from 2007 to 2009. He currently serves as an Associate Editor for the IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, a Distinguished Lecturer for the IEEE AP-S, and Chair of the Technical Committee on Antennas and Propagation, IEICE. He has been appointed as General Chair of ISAP2012 to be held in Nagoya, Japan in 2012.