Flexible and Compact AMC Based Antenna for ... - IEEE Xplore

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IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 61, NO. 2, FEBRUARY 2013

Flexible and Compact AMC Based Antenna for Telemedicine Applications Haider R. Raad, Member, IEEE, Ayman I. Abbosh, Student Member, IEEE, Hussain M. Al-Rizzo, and Daniel G. Rucker

Abstract—We present a flexible, compact antenna system intended for telemedicine applications. The design is based on an M-shaped printed monopole antenna operating in the Industrial, Scientific, and Medical (ISM) 2.45 GHz band integrated with a miniaturized slotted Jerusalem Cross (JC) Artificial Magnetic Conductor (AMC) ground plane. The AMC ground plane is utilized to isolate the user’s body from undesired electromagnetic radiation in addition to minimizing the antenna’s impedance mismatch caused by the proximity to human tissues. Specific Absorption Rate (SAR) is analyzed using a numerical human body model (HUGO) to assess the feasibility of the proposed design. The antenna expresses 18% impedance bandwidth; moreover, the inclusion of the AMC ground plane increases the front to back ratio by 8 dB, provides 3.7 dB increase in gain, in addition to 64% reduction in SAR. Experimental and numerical results show that the radiation characteristics, impedance matching, and SAR values of the proposed design are significantly improved compared to conventional monopole and dipole antennas. Furthermore, it offers a compact and flexible solution which makes it a good candidate for the wearable telemedicine application. Index Terms—Artificial Magnetic Conductor (AMC), flexible and wearable antennas, printed monopole, telemedicine.

I. INTRODUCTION

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ELEMEDICINE is becoming increasingly utilized by health care providers due to the growing demand for remote monitoring of human vital signs. Telemedicine applications include but not limited to monitoring of seniors, recovery tracking of patients, monitoring the health parameters of astronauts and athletes, and E-psychiatry [1]. The health parameters that may be forwarded to remote stations via wireless transmission (off body mode) range from basal body temperature, heart rate, respiratory rate, blood pressure, to glucose levels and Electro Cardio Gram (ECG) waveforms [2]. In addition to off- body means, on-body mode is also essential for communication between sensor devices worn or implanted within the patient’s body [3]. For optimum performance, antennas used in telemedicine schemes are required to be compact, lightweight, and mechanically robust. They are also preferred

Manuscript received May 27, 2012; revised July 27, 2012; accepted September 19, 2012. Date of publication October 09, 2012; date of current version January 30, 2013. H. R. Raad is with the Department of Engineering Science, Sonoma State University, Rohnert Park, CA 94928 USA (e-mail: [email protected]). A. I. Abbosh, H. M. Al-Rizzo, and D. G. Rucker are with the Department of Systems Engineering, University of Arkansas at Little Rock, Little Rock, AR 72204 USA. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TAP.2012.2223449

to be comfortable and conformal to the body shape; yet, they must express high efficiency and reliability. In general, traditional microstrip antennas offer favorable characteristics in terms of radiation pattern (uni-directional which is preferred in telemedicine application to minimizes the user’s exposure to EM radiation). Furthermore, microstrip antennas have the merits of low profile construction, low fabrication complexity and low cost; however, they suffer from a very narrow bandwidth which is a function of the substrate thickness and dielectric constant [4]. Thus, a low profile antenna with a hemi-spherical radiation pattern and a relatively wide bandwidth is needed to be employed in this application. Several techniques [5]–[8] have been reported to solve the aforementioned issues including the use of cavities, absorbers and shielding planes. However, these techniques lead either to an unacceptable increase in the antenna’s height, or a more complicated manufacturing process. In [5], a cavity slot antenna is proposed for Body Area Networks (BAN) applications. Although the antenna demonstrates a good efficiency when tested on a human phantom, it involves a multilayer fabrication process in addition to its relatively high profile. In [6], a reflector patch element is utilized to decrease the back radiated field. The performance of this technique is highly dependent on the ground plane size, furthermore, it is based on a stack of multiple (five) layers which leads to a complex high profile system. In [7], a Single Negative (SNG) metamaterial is utilized to suppress the EM wave propagating towards the human body, though efficient, it does not offer a low profile solution. In [8], the performance of a dual band (2.45, 5 GHz) textile antenna based on the conventional square-patch based AMC is investigated in terms of SAR. A significant reduction is achieved when the AMC structure is included; however, the size of the design is relatively large (120 mm 120 mm). Moreover, textile based antennas are prone to discontinuities in substrate materials in addition to the textile nature of fluid absorption [9]. In this paper, we present an ultra low profile printed monopole antenna integrated with a compact AMC ground plane based on a novel miniaturized JC inclusion. The AMC structure is utilized to provide in phase reflection which significantly enhances the front to back ratio and consequently reduces the SAR while maintaining a relatively large impedance bandwidth. Furthermore, the proposed antenna is flexible and compact which makes it suitable for the targeted application. In Section II, we present the design and analysis of the antenna and AMC ground plane. In Section III, we discuss the fabrication process. Results and discussion are provided in Section IV; while in Section V, the Specific Absorption Rate (SAR)

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RAAD et al.: FLEXIBLE AND COMPACT AMC BASED ANTENNA FOR TELEMEDICINE APPLICATIONS

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Fig. 1. Prototype of the proposed design composed of an M-shaped printed monopole antenna and slotted JC-AMC.

is evaluated for the design with and without the AMC structure for comparison purposes. Finally, conclusions are given in Section VI.

Fig. 2. Geometry and dimensions of the proposed M-shaped antenna.

TABLE I DIMENSIONS OF THE M-SHAPED ANTENNA IN mm

II. DESIGN AND CONFIGURATION Design and analysis of the antenna and AMC structure are carried out using the full wave electromagnetic simulation software CST Microwave Studio which is based on the Finite Integration Technique (FIT) [10]. Simulated results are further verified using Ansys’ HFSS which is based on the Finite Element Method (FEM) [11]. A. Antenna Design The proposed antenna is designed to operate in the ISM 2.45 GHz band. The M-shaped monopole is fed by a Coplanar Waveguide (CPW) which offers a single-layer fabrication process. Both the radiating element and the CPW are printed on the same side of a 45 mm 30 mm Kapton polyimide substrate with a dielectric constant of 3.5 and a loss tangent of 0.002. Fig. 2 and Table I depict the geometry and dimensions of the proposed antenna. Polyimide Kapton was chosen as the antenna’s substrate since it exhibits a good balance of physical, chemical, and electrical properties with a low loss tangent over a wide frequency range. Furthermore, Kapton offers a very low profile (50.8 ), yet, very robust with a tensile strength of 165 MPa at 73 , a dielectric strength of 3500–7000 volts/mil, and a temperature rating of 65 to 150 [12]. The electrical length of the M-shaped monopole in addition to the ground plane size control the resonant frequency of the antenna which is designed to resonate at 2.45 GHz to cover the ISM band. It is worth noting that the separation distance between the two arms in addition to are selected through a parametric study to achieve the least return loss. B. AMC Design As is well known, a Perfect Electric Conductor (PEC) has a reflection phase of 180 for a normally incident plane wave, while a Perfect Magnetic Conductor (PMC) has a 0 reflection phase. Image theory states that a PEC ground plane causes the

antenna’s current and its image to cancel each other which is responsible for dropping the real part of the impedance towards zero , while the imaginary part approaches infinity. Hence, a significant amount of the electromagnetic energy is trapped between the antenna and the ground plane which in turn leads to a significant reduction in the antenna’s efficiency [13]. This is the opposite scenario if an AMC ground plane (which emulates a PMC in a specific frequency band) is used instead of PEC due to its in-phase reflection characteristics. Thus, utilizing an AMC as a ground plane significantly enhances the gain of dipole/monopole antennas [14]. In the application under consideration, the AMC ground plane is used to isolate the user’s body from undesired exposure to electromagnetic radiation in addition to eliminating the antenna’s impedance mismatch caused by the proximity to human tissues. Frequency Selective Surfaces (FSS) based on Jerusalem Cross (JC) geometry have long been applied in the design of microwave and RF systems, such as filters, polarizers, and couplers [15], [16]. With the advent of AMCs and their fascinating applications in enhancing the performance of antenna systems, JC structures were also considered in synthesizing

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Fig. 3. Circuit model for the JC based AMC showing the grid and dielectric impedances.

Fig. 5. Reflection phase profiles for the proposed AMC structures compared to a conventional JC based AMC.

Fig. 4. Conventional JC AMC structure (a), proposed structure 1 (b), proposed structure 2 (c).

such artificial materials [17]. JCs offer a miniaturized structure over the conventional square-patch based FSS suggested originally by Sievenpiper [18]. More importantly, JC-based AMC exhibits higher angular stability compared to its corrivals when illuminated obliquely. Hence, this structure was selected as a candidate for the targeted application which requires angular stability since it is likely to be conformed on objects and follow certain curvatures. A circuit model for the JC-AMC is depicted in Fig. 3. The total surface impedance can be expressed as in [19] (1) where is the FSS grid impedance, and is the impedance of the grounded dielectric slab. From the above equation, the structure’s resonant frequency can be found (2) where , , are the grid inductance, dielectric slab inductance and grid capacitance, respectively. The grid capacitance of two parallel patches positioned on a dielectric slab can be extracted using (3) [20] (3) (4) is the width of the JC edge, is the gap between where two adjacent structures, and is equal to , where the dimension of is shown in Fig. 4(a). On the other hand the bandwidth of the JC-based AMC can be expressed by (5) (5)

Fig. 4 shows the geometry of the proposed AMC structure with reference to the conventional JC AMC. It is evident from (2) that the structure can be miniaturized by increasing one of the following parameters: the grid inductance , dielectric inductance , and grid capacitance . Obviously, increasing leads to a higher profile structure which is not preferred for the considered application. In this study, a central slot is introduced in the cross geometry to lengthen the current path which in turn increases the grid inductance. Further miniaturization can be achieved by increasing the grid capacitance which can be performed by either increasing the cross edge length to gap ratio (a/g) or through dielectric loading. In the second proposed structure (Fig. 4(c)), increasing the length of leads to an increase in the (a/g) ratio which leads to a higher value of the argument in (3) and consequently, an increased . For comparison purposes, a conventional JC structure is modeled to resonate at 4.7 GHz and compared to the proposed models. Fig. 5 shows the reflection phase profiles of the proposed structures in comparison to the conventional JC AMC. It is evident from the reflection phase profile depicted in Fig. 5 that the resonant frequency of the proposed structure is scaled down by a factor of 21% compared to conventional JC-based AMCs. For the application under consideration, the structure’s resonant frequency is tuned to cover the 2.45 GHz ISM band. Fig. 6 and Table II show the geometry and dimensions of the proposed AMC structure. The AMC ground plane comprises 3 3 unit cells of slotted JC-AMC which is designed to resonate at the same operating frequency of the antenna. The total size of the AMC structure is 65.7 mm 65.7 mm printed on a flexible vinyl substrate with a 1.5 mm thickness and a dielectric constant of 2.5. It is worth mentioning that the antenna is separated from the AMC (using flexible foam) by 1.7 mm to reduce the impedance mismatch caused by the AMC proximity. This value is found through a parametric study. III. FABRICATION The radiating element along with the CPW are printed on a 50.8 flexible Kapton polyimide substrate. A conductive ink based on sliver nano particles is deposited over the substrate by a Dimatix DMP 2831 ink-jet material printer followed by a


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Fig. 6. Geometry and dimensions of the slotted JC based AMC operating at 2.45 GHz.

TABLE II DIMENSIONS OF THE SLOTTED JC BASED AMC UNIT CELL IN mm

Fig. 7. Measured reflection coefficient for the M-shaped antenna with and without AMC.

thermal annealing at 100 for 3 hours by a LPKF Protoflow industrial oven. It should be noted that 2 layers of ink were jetted on the substrate to achieve a robust and continuous pattern. The three CPW conductors were affixed to an SMA connecter for measurement purposes. On the other hand, the AMC inclusions are printed on a kapton substrate then adhered to a grounded flexible vinyl substrate. This step is essential since it is not possible to directly print on vinyl substrates due to their surface hydrophobic nature. IV. RESULTS AND DISCUSSION

Fig. 8. Reflection coefficient system.

in-situ measurement for the proposed antenna

A. S-Parameters To study the effect of AMC proximity on the impedance matching, the reflection coefficient of the fabricated prototype is measured with and without AMC using an Agilent PNA-X series N5242A vector network analyzer with (10 MHz–26.5 GHz) frequency range. As can be seen in Fig. 7, a good impedance matching is maintained for both cases despite the slight increase in return loss and shift in the resonant frequency when the AMC is integrated. B. Effects of Proximity to Human Tissues To reflect a scenario of a realistic operation, an in-situ measurement is conducted where the proposed antenna system (with and without AMC) is positioned over a human arm to investigate the effect of human tissues proximity on its impedance matching. The antenna is affixed on a human arm with an adhesive tape then connected to the network analyzer. The measurement setup is shown in Fig. 8. As can be seen in Fig. 9, removing the AMC leads to a 170 MHz (7%) shift in the resonant frequency to the lower side in addition to about 10 dB increase in the return loss.

C. Flexibility Tests Since the antenna is expected to be bent or conformed during operation, flexibility tests are conducted to ensure performance reliability. Resonant frequency and return loss need to be evaluated since they are prone to shift/decrease due to impedance mismatch and change in the effective electrical length of the radiating element. Furthermore, repeated testing of the antennas under bending and twisting are required to test the deposited conductive ink for any deformations, discontinuities or cracks and to make sure no wrinkles or permanent folds are introduced in the substrate which might compromise the performance and/or operation of the antenna. As stated before, Polyimide Kapton substrate was chosen for the targeted application mainly due to its physical robustness and high flexibility. On the other hand, the vinyl substrate which is used as the AMC dielectric also expresses an excellent flexibility and mechanical robustness. It should be noted that the fabricated prototype demonstrated an excellent performance as it was tested repeatedly against bending, twisting, and rolling effects. Fig. 10 shows the flexibility test setup where the proposed

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Fig. 11. Measured with different radii ( extents. Fig. 9.

for the proposed system when bent on a foam cylinder and ) to mimic different bending

for the antenna on a human arm (with and without AMC).

Fig. 12. Radiation pattern measurement setup inside an anechoic chamber.

reflection coefficient of the proposed antenna system with different bending extents. D. Far-field Radiation Patterns Fig. 10. Flexibility test setup (Antenna and AMC are conformed over a cylindrical foam with different radii to reflect different extents of bending).

antenna is rolled over a foam cylinder and connected to the network analyzer for reflection coefficient measurements. Within the context of wearable and flexible electronics, the antenna system is conformed on two foam cylinders with radii and to mimic different bending extents. These radii were carefully chosen to emulate the antenna conformed on an average human arm and wrist, respectively. At the same time, they correspond to flexing the antenna with slight and extreme extents in flexible hand-held devices. The following results were observed: a shift (40–80 MHz) to a lower resonant frequency when the antenna system is conformed over the foam cylinders. However, the relatively large impedance bandwidth of the proposed antenna could easily accommodate this encountered shift. Fig. 11 depicts the measured

The far-field radiation patterns of the principal planes (E and H) were measured inside the University of Arkansas at Little Rock’s anechoic chamber. The Antenna Under Test (AUT) was placed on an ETS Lindgren 2090 positioner and aligned to a horn antenna with an adjustable polarization where both E and H cuts can be obtained. Radiation patterns of the proposed antenna at 2.45 GHz on the plane (E-plane) and plane (H-plane) are depicted in Fig. 13. It can be observed that the printed monopole retains a reasonable omni-directional radiation patterns at resonance. As stated earlier, integrating the AMC structure with the antenna (as a ground plane) overcomes the abovementioned problems associated with the human tissues proximity. Furthermore, the radiation pattern turns to quasi hemi-spherical when the AMC is integrated compared to an omni-directional radiation pattern for conventional monopoles due to an increase in the front to back ratio achieved by the in-phase reflection of the AMC ground plane. Fig. 12 depicts the radiation pattern


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Fig. 14. Numerical Human model (HUGO) used for SAR evaluation of the proposed antenna system.

ground plane. The reader is referred to [21], [22] for detailed investigation on the effect of bending on the radiation pattern of flexible and wearable antennas. V. SAR ANALYSIS SAR is a standard measure used to evaluate the electromagnetic power deposition in the human tissues. According to the guidelines specified by the Federal Communication Commission (FCC), SAR values must not exceed the exposure limit which is 1.6 W/kg averaged over 1 g of tissue [23]. The following equation relates SAR with the applied input power:

(6)

Fig. 13. Measured E-plane ( cut) and H-plane ( cut) radiation patterns for the M-shaped printed monopole antenna (without AMC) (top), and the same antenna integrated with the slotted JC-AMC ground plane (bottom).

measurement setup which was performed inside the anechoic chamber of UALR. It is evident from Fig. 13 that a considerable improvement in terms of gain is achieved (3.7 dB) by including the AMC structure. The measured gain for the proposed antenna system is 4.8 dB compared to 1.1 dB for the case without AMC. An increase in the measured front to back ratio of around 8 dB is achieved for the fabricated prototype. It should be noted that the front to back ratio could be further increased if more AMC unit cells are utilized (larger ground plane); however, this solution leads to a larger design. This is associated with the well known tradeoff between the size of the ground plane and the amount of back radiation. It is also worth mentioning that the antenna’s directivity is expected to be moderately reduced when subjected to bending due to the decreased effective shielding area of the bent

where is the conductivity of the tissue in S/m, is the electric field in V/m, and is the mass density of the tissue in . As a benchmark, a 125 mW power input is chosen to evaluate the performance of the proposed antenna systems in terms of SAR. To reflect a realistic setup, the proposed antenna without AMC was first simulated over a HUGO numerical human model then compared to the case when the AMC is inserted underneath the antenna. HUGO is a numerical 3D volume and surface anatomical data set of the human body produced by the National Library of Medicine. The HUGO data set is segmented and categorized into 40 distinct types of tissues and available at a mesh size [24]. The antenna is positioned on the arm of the human model as a typical realistic setup. To reduce the simulation time, a reasonably sized portion of the arm (sectional area of about 10 times the antenna’s size) is selected instead of simulating the entire numerical model. The number of mesh cells is reduced from 37,756,913 down to 1,866,174 mesh cells which led to a substantial reduction in the simulation time. The numerical setup for the antenna-Hugo model is shown in Fig. 14.

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SAR values for the AMC based antenna were very low with a reduction of 64% compared to the same antenna without the integration of AMC. Moreover, the design exhibits a low susceptibility to performance degradation in terms of return loss and shift in the resonant frequency when conformed on curved surfaces. To conclude, the proposed compact and flexible design would be a good candidate for WBAN and telemedicine applications in terms of SAR, efficiency, bandwidth and stability. REFERENCES

Fig. 15. SAR values for the proposed design (a) and for the same design without the AMC structure (b).

It is evident from Fig. 15 that for the considered input power, the proposed design achieved a SAR value of 0.683 W/Kg while the same antenna without AMC experiences 1.88 W/Kg which is above the specified rate allowed by the FCC. Thus, the proposed design achieved a 64% reduction in SAR. VI. CONCLUSION We presented a flexible compact printed monopole antenna design integrated with a miniaturized slotted JC AMC ground plane for telemedicine applications. The AMC ground plane is utilized to eliminate the impedance mismatch and frequency shift caused by the human tissues proximity. Furthermore, the in-phase reflection characteristic of the AMC structure significantly reduced the undesired electromagnetic radiation towards the patient’s body which is essential to the performance of telemedicine antenna systems. The proposed antenna has an operating bandwidth of 18% at 2.45 GHz. The calculated

[1] Q. Fang, S. Lee, H. Permana, K. Ghorbani, and I. Cosic, “Developing a wireless implantable body sensor network in MICS band,” IEEE Trans. Inf. Technol. Biomed., vol. 15, no. 4, pp. 567–576, Jul. 2011. [2] G. Conway and W. Scanlon, “Antennas for over Body-Surface Comm. At 2.45 GHz,” IEEE Trans. Antennas Propagat., vol. 57, no. 4, pp. 844–855, Apr. 2009. [3] Y. Ouyang, D. Love, and w. Chapel, “Body-worn distributed MIMO system,” IEEE Trans. Veh. Technol., vol. 58, no. 4, pp. 16–22, May 2009. [4] L. Liu, S. Zhu, and R. Langley, “Dual-band triangular patch antenna with modified ground plane,” Electron. Lett., vol. 43, no. 3, pp. 140–141, Feb. 1, 2007. [5] N. Haga, K. Saito, M. Takahashi, and K. Ito, “Characteristics of cavity slot antenna for body-area networks,” IEEE Trans. Antennas Propagat., vol. 57, no. 4, pp. 837–843, Apr. 2009. [6] W. Rowe and R. Waterhouse, “Reduction of backward radiation for CPW fed aperture stacked patch antennas on small ground planes,” IEEE Trans. Antennas Propagat., vol. 51, no. 6, pp. 1411–1413, Jun. 2003. [7] C. T. Islam, M. Faruque, and N. Misran, “Reduction of specific absorption rate (SAR) in the human head with ferrite material and metamaterial,” Prog. Electromagn. Res. C, vol. 9, no. 4758, 2009. [8] S. Zhu and R. Langley, “Dual-band wearable textile antenna on an EBG substrate,” IEEE Trans. Antennas Propagat., vol. 57, no. 4, pp. 926–935, Apr. 2009. [9] Y. P. Salonen, J. Kim, and Y. Rahmat-Samii, “Dual-band E-shaped patch wearable textile antenna,” in IEEE Antennas Propagat. Soc. Symp., 2004, vol. 1, pp. 466–469. [10] CST Microwave Studio [Online]. Available: http/www.cst.com [11] Ansys High Frequency Structure Simulator [Online]. Available: http/ www.ansys.com [12] Dupont Kapton Polyimide Specification Sheet [Online]. Available: http://www2.dupont.com/kapton [13] D. Sievenpiper, Z. Lijun Zhang, R. Broas, N. Alexopolous, and E. Yablonovitch, “High-impedance electromagnetic surfaces with a forbidden frequency band,” IEEE Trans. Microw. Theory Tech., vol. 47, no. 11, pp. 2059–2074, Nov 1999. [14] A. Vallecchi, J. De Luis, F. Capolino, and F. De Flaviis, “Low profile fully planar folded dipole antenna on a high impedance surface,” IEEE Trans. Antennas Propagat., vol. 60, no. 1, pp. 51–62, Jan. 2012. [15] R. Cahill and E. Parker, “Concentric ring and jerusalem cross arrays as incidence diplexer,” Electron. frequency selective surfaces for a 45 Lett., vol. 18, no. 8, pp. 313–314, Apr. 1982. [16] R. Dickie, R. Cahill, N. Mitchell, H. Gamble, V. Fusco, and Y. Munro, “664 GHz dual polarization frequency selective surface,” Electron. Lett., vol. 46, no. 7, pp. 472–474, Apr. 2010. [17] M. Hosseini, A. Pirhadi, and M. Hakkak, “A novel AMC with little sensitivity to the angle of incidence using 2-layer Jerusalem cross FSS,” Prog. Electromag. Res., PIER, vol. 64, pp. 43–51, 2006. [18] D. F. Sievenpiper, “High-impedance electromagnetic surfaces,” Ph.D. thesis, Univ. Calif., Los Angeles, CA, 1999. [19] M. Hosseini, A. Pirhadi, and M. Hakkak, “Design of an AMC with little sensitivity to angle of incidence using an optimized jerusalem cross FSS,” in Proc. IEEE Int. Workshop Antenna Technology: Small Antennas Novel Metamat., New York, 2006, pp. 245–248. [20] C. R. Simovski, P. de Maagt, and I. V. Melchakova, “High-impedance surfaces having stable resonance with respect to polarization and incidence angle,” IEEE Trans. Antennas Propagat., vol. 53, no. 3, Mar. 2005. [21] L. Locher, M. Klemm, T. Kirstein, and G. Troster, “Design and characterization of purely textile patch antennas,” IEEE Trans. Adv. Packag., vol. 29, no. 4, pp. 777–788, Nov. 2006.


[22] 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 Propagat., vol. 57, no. 4, pp. 919–925, April 2009. [23] IEEE Recommended Practice for Measurements and Computations of Radio Frequency Electromagnetic Fields With Respect to Human Exposure to Such Fields, 100 kHz–300 GHz, IEEE Std C95.3-2002, 2002, (Revision of IEEE Std C95.3-1991), vol., no., pp.i–126. [24] [Online]. Available: http://www.vr-laboratory.com Haider R. Raad (S’09–M’12) received the Ph.D. and M.S. degrees in telecommunication systems engineering from the University of Arkansas at Little Rock (UALR), Little Rock, AR, in 2012 and 2011, respectively; and the M.S. degree in electrical and computer engineering from New York Institute of Technology, NY, in 2006, (highest honors). Currently, he serves as a Visiting Assistant Professor in the Department of Engineering Science, California State University, Sonoma, CA. Dr. Raad has published 2 book chapters, and over 25 peer reviewed journal and conference papers on research fields of his interest which include: flexible and wearable antennas; antennas for telemedicine and wireless body area networks, implantable antennas, metamaterials, electromagnetic bandgap (EBG) structures, artificial magnetic conductors (AMC), antennas for MIMO systems, and global positioning systems. He is also the recipient of the first place award of the Institute of Engineering and Technology 2012 Present Around the World competition, UALR’s Outstanding Teaching Support Award, and AAMI/TEAMS Academic Excellence Award in 2012.

Ayman I. Abbosh (S’12) received the B.Sc. degree in electrical engineering, electronics and communications and M.Sc. in electronics and communication from the University of Mosul, Mosul, Iraq, 1996, and 1999, respectively. Since then, he is a member of the Iraqi Engineers Union. In 2002 to 2007, he worked as a Lecturer in the Department of Electrical Engineering, Collage of Engineering, University of Mosul. He is currently working towards the Ph.D. degree in Systems Engineering at the University of Arkansas at Little Rock (UALR), Little Rock, AR, since 2010. His research interests area are in Wireless Systems Planning, MIMO technology, Beamforming, Antenna design for flexible, wearable and implantable devices, and electrically small antennas.

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Hussain M. Al-Rizzo received the B.Sc. degree in electronics and communications (1979) (High Honors), the Postgraduate Diploma in electronics and communications (1981) (High Honors), and the M.Sc. in microwave communication systems (1983) from the University of Mosul, Mosul, Iraq. From May 1983 to October 1987 he was working with the Electromagnetic Wave Propagation Department, Space and Astronomy Research Center, Scientific Research Council, Baghdad, Iraq. In December 1987, he joined the Radiating Systems Research Laboratory, Electrical and Computer Engineering Department, University of New Brunswick, Fredericton, NB, Canada, where he received the Ph.D. degree (1992) in computational electromagnetics, wireless communications, and the global positioning system. For his various academic achievements he won the nomination by the University of New Brunswick as the best doctoral graduate in science and engineering. Since 2000, he joined the Systems Engineering Department, University of Arkansas at Little Rock (UALR), Little Rock, AR, where he is currently a Professor of Systems Engineering. He has published over 40 peer-reviewed journal papers, 70 conference presentations, and several patents. His research areas include implantable antennas and wireless systems, smart antennas, WLAN deployment and load balancing, electromagnetic wave scattering by complex objects, design, modeling and testing of high-power microwave applicators, design and analysis of microstrip antennas for mobile radio systems, precipitation effects on terrestrial and satellite frequency re-use communication systems, and field operation of NAVSTAR GPS receivers.

Daniel G. Rucker received the B.Sc. degree in systems engineering from the University of Arkansas at Little Rock (UALR), Little Rock, AR, in Spring 2007. He was accepted by the National Science Foundation for a Research Experience for Undergraduates program in the summer of 2006 at the Arecibo Observatory in Puerto Rico. There he worked on digital electronics and radar control. Following this work, he shifted his undergraduate research to microstrip antennas for biomedical devices at UALR. Currently, he is working towards the Ph.D. degree in applied science at the UALR. His current research areas are microstrip antennas, low power wireless sensor systems, and systems engineering design. In the area of microstrip antennas, his work is focused on implantable and wearable microstrip antennas for biomedical applications.