HIGH IMPEDANCE SURFACES FOR FLEXIBLE AND CONFORMAL WIRELESS SYSTEMS

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1 American Journal of Engineering and Applied Science 7 (2): , 204 ISSN: H.R. Khaleel et al., Thi open acce article i ditributed under a Creative Common Attribution (CC-BY) 3.0 licene doi:0.3844/ajeap Publihed Online 7 (2) 204 ( HIGH IMPEDANCE SURFACES FOR FLEXIBLE AND CONFORMAL WIRELESS SYSTEMS Haider R. Khaleel, 2 Huain M. Al-Rizzo, 2 Ayman Iac and 2 Said Abuhamleh Department of Engineering Science, Sonoma State Univerity, Rohnert Park, California, USA 2 Department of Sytem Engineering, Univerity of Arkana at Little Rock, Little Rock, Arkana, USA Received ; Revied ; Accepted ABSTRACT Recent year have witneed a great deal of interet from both cientific and academic communitie in the field of flexible electronic ytem. Mot flexible electronic ytem require the integration of flexible antenna operating in pecific frequency band to provide wirele connectivity which i highly demanded by today network oriented ociety. On the other hand, High Impedance Surface have become very popular in the deign of contemporary antenna and micro-wave device due to their wide range of application derived from their unique electromagnetic propertie which ignificantly enhance the performance of antenna and RF ytem. Accordingly, the integration of HIS tructure within flexible wirele ytem i very beneficial in thi growing field of reearch. In thi paper, a ytematic review of flexible HIS tructure reported in the literature i conducted, which provide the reader with a thorough decription and a complete lit of tate of the art deign intended for flexible wirele ytem. Keyword: High Impedance Surface (HIS), Antenna, Flexible Electronic, Wirele Sytem. INTRODUCTION provide wirele connectivity. Needle to ay, the efficiency of thee ytem primarily depend on the Today indutrial and academic reearch i focuing characteritic of the integrated antenna. intenive activitie aimed at developing flexible and The nature of flexible wirele technologie require wearable wirele ytem due to their applicability in a the integration of flexible, low profile, light weight and wide pectrum of application uch a peronal compact antenna. At the ame time, thee antenna communication, medicine, firefighting, entertainment, hould be mechanically robut, efficient with ufficient aeronautic, military and Radio Frequency Identification bandwidth and deirable radiation characteritic. (RFID) tag (Cai et al., 2007; Hertleer et al., 2009). On the other hand, the ame decade witneed the Their light weight, low fabrication cot, eae of revolution of Metamaterial (MTM), artificially manufacturing and the availability of inexpenive engineered tructure which exhibit unique flexible film/ubtrate (i.e., paper, textile and platic) make flexible electronic an appealing electromagnetic propertie that do not exit in nature candidate for the next generation of hand-held (Yao et al., 2005). Thee tructure can be engineered electronic (Nathan and Chalamala, 2005). Moreover, to have deired feature within a deired frequency recent development in miniaturized and flexible energy range. The integration of thee artificial tructure torage component paved the road for the with antenna and microwave circuit ha hown to be commercialization of uch ytem (Huang et al., 20). extremely beneficial in everal application (Yang and Modern flexible electronic and gadget uch a Rahmat-Samii, 2009). flexible mobile phone, diplay, electronic book and The mot promiing type of MTM that are expected rollable keyboard are often equipped with an antenna to to be indutrialized in the field of wirele ytem are Correponding Author: Haider R. Khaleel, Department of Engineering Science, Sonoma State Univerity, Rohnert Park, California, USA 266

2 the µ-negative (MNG) MTM and High Impedance Surface (HIS) (Sievenpiper et al., 999). HIS are uccefully applied in many antenna ytem for performance enhancement utilizing their unique feature. Their advantage include urface wave reduction which i conidered a a eriou drawback in microtrip antenna a it reduce antenna gain, efficiency, limit their bandwidth and increae cro polarization level. In phae reflection and mutual coupling reduction among radiating element in antenna array in general and MIMO ytem in particular are very promiing application of thee artificial tructure. However, the application of uch tructure in flexible and wearable technologie i limited by their relatively high profile and their ize and bandwidth dependence on the ubtrate relative permittivity and thickne (Park et al., 200). Thi ha triggered the need for flexible, conformal and compact HIS to be integrated within the targeted technology. In repone to uch requirement, a plethora of deign and technique have been reported in the literature which will be reviewed in thi article. In ection 2, a theoretical background on HIS i provided. In ection 3, we dicu the deign, methodology and application of the ignificant flexible HIS deign reported in the literature. The flexibility analyi involved with characterizing the performance of HIS under bending and flexing condition i dicued in ection 4. Finally, concluion are given in ection HIGH IMPEDANCE SURFACES: BACKGROUND HIS wa firt propoed by (Sievenpiper et al., 999) the tructure of which wa baed on quare metallic plate printed on a grounded dielectric ubtrate and connected to the ground plane through metallic pot (via). Later on, numerou type of HIS geometrie have been extenively tudied (Kim and Yeo, 2008; Cota et al., 2009). In general, HIS are claified into two type baed on their characteritic feature: Artificial Magnetic Conductor (AMC), which mimic a Perfect Magnetic Conductor (PMC) in a pecific frequency range and Electromagnetic Band Gap (EBG). It i known that a Perfect Electric Conductor (PEC) ha a reflection phae of 80 for a normally incident plane wave, while a Perfect Magnetic Conductor (PMC), which doe not exit in nature, ha a reflection phae of 0. Image theorem 267 tate that a PEC ground plane caue the antenna current and it image to cancel each other, in other word horting the antenna. Thi i reponible for dropping the real part of the antenna impedance toward zero ohm, while the imaginary impedance approache infinity. Thu, a ignificant amount of the electromagnetic energy i trapped between the antenna and the ground plane; hence the antenna can no longer radiate efficiently (Kim and Yeo, 2008). Thi i the oppoite cenario if an AMC i placed intead of PEC due to it reflection of electromagnetic wave with zero phae hift. HIS tructure can be artificially engineered to have in phae reflection coefficient propertie in a pecified frequency range. They are typically realized baed on periodic metallization pattern which are often called Frequency Selective Surface (FSS) printed on a grounded dielectric material (Qian et al., 997). The urface impedance of the HIS i defined a the ratio of the tangential component of the electric field E to the tangential component of the magnetic field H at the urface Equation : E t = Ht () where, E t and H t are the electric and magnetic field component tangential to the urface. The FSS grid along with the grounded dielectric lab can be repreented by a capacitance in parallel with an inductance (Cota et al., 2009), i.e., a reonant LC circuit with a reonant frequency given by Equation 2: f = (2) 2 Π LC where, L and C are the equivalent inductance and capacitance aociated with the dielectric lab and the FSS grid. The circuit analogy for the HIS i depicted in Fig.. Thi reonant frequency i determined by the dimenion and geometry of the tructure; i.e., changing the dimenion and geometry lead to a change in the value of L and C and therefore the reonant frequency can be modified accordingly. For example, the period of a quare patch baed HIS i related to it reonant frequency by Equation 3: λ c p = = (3) 2 2 f ε

3 (a) (b) Fig.. (a) Circuit repreentation for the HIS tructure (b) Conventional Square-patch baed HIS tructure According to the ame parallel LC model, the urface impedance and reflection coefficient for the HIS tructure can be calculated by Equation 4 and 5: = jωl (4) ( ω ) 2 ω o where, ω 0 i: ω = (5) 2 Π LC Γ = And the reflection coefficient i Equation 6: + (6) where, i the free pace impedance. A can be determined from (6), the urface impedance of a PEC urface, which ha a zero tangential component of electric field i zero. Hence, the PEC reflection coefficient i equal to -. While for a PMC urface, the tangential component of the magnetic field i zero which yield infinite urface impedance. Thu, the plane wave reflection coefficient for the PMC i +. It i worth mentioning here that the operational HIS bandwidth i between -90º and +90º a defined by (Sievenpiper et al., 999). On the other hand, when dealing with urface wave uppreion, muhroom type EBG tructure demontrate a better performance compared to viale tructure. However, grounding via complicate the fabrication 268 proce and it would be impractical to conider it for flexible and conformal application. In general, EBG reonant frequency doe not normally coincide with the AMC. Thi can deteriorate the benefit of HIS in pecific application. However, the AMC and EBG feature are not required to coexit in the conidered application. 3. LITERATURE REVIEW Bai et al. (2009) invetigated the performance of a textile Coplanar Waveguide fed (CPW) antenna under bending and crumpling condition. A HIS i ued to improve the wearable antenna performance. Both input impedance and radiation pattern were invetigated baed on numerical and experimental method. hu and Langley (2009), invetigated the performance of a flexible dual band (2.45, 5 GHz) textile antenna baed on the conventional quare patch baed HIS in term of Specific Aborption Rate (SAR). A ignificant reduction in SAR achieved when the HIS tructure i included; however, the ize of the deign i relatively large (20 20 mm). Moreover, textile baed antenna are prone to dicontinuitie in ubtrate material in addition to the textile nature of fluid aborption. A flexible, compact antenna ytem intended for telemedicine application wa propoed by (Raad et al., 202). The deign i baed on an M haped printed monopole antenna operating in the Indutrial, Scientific and Medical (ISM) 2.45 GHz band integrated with a miniaturized lotted Jerualem Cro (JC) HIS ground plane. The HIS ground plane i utilized to iolate the uer body from undeired electromagnetic radiation in addition to minimizing the antenna impedance mimatch caued by the proximity to human tiue.

4 SAR i aeed uing a Human body model (HUGO) to verify the feaibility of the propoed deign. The antenna expree 8% impedance bandwidth; moreover, the integration of the HIS ground plane increae the front to back ratio by 8 db, provide 3.7 db increae in gain, in addition to 64% reduction in SAR (Shahid, 2009) preented a modified wearable form of HIS defined a non uniform HIS and integrated it with an antenna for improved performance under low profile limitation. The HIS wa alo utilized to reduce the ize of a normal patch antenna and improve it gain and impedance bandwidth. A low profile antenna baed on the propertie of a non-uniform HIS wa preented by the ame author in 200. The propoed deign i able to minimize electromagnetic interaction with the human tiue which in turn reduce SAR and degradation in radiation efficiency. Finally, A flexible uniplanar HIS deign manufactured uing laer micromachining wa preented by (De Co and La-Hera, 202). It i characterized under flat and bent condition by meauring it reflection coefficient phae in an anechoic chamber. The deigned prototype how broad HIS operation bandwidth (around 7%) and polarization angle independency. 4. FLEXIBILITY ANALYSIS A tated previouly, flexible, wearable and conformal antenna ytem are becoming extremely popular nowaday. One of the main challenge facing uch ytem i the uncertainty of maintaining performance parameter of the wearable/conformal antenna ytem which are baed on their flat profile during operation epecially for element made of flexible material. Therefore, it i neceary to evaluate the performance of antenna and any type of integrated tructure under bending and flexing condition. It i worth mentioning that mot previou reearch wa only focued on invetigating the bending effect on wearable/conformal antenna baed on conventional PEC ground plane both numerically and experimentally (Farahani et al., 200). Palikara et al. (20), propoed a conformal HIS i utilized to reduce the diameter of a cylindrical antenna, However, only the effect of curvature on the far field radiation pattern wa invetigated. Bai et al. (2009) invetigated the performance of a dual band textile antenna integrated with an HIS under bending and crumpling condition in term of input impedance and radiation pattern. However, the reported reearch focued mainly on the effect of curvature on the antenna characteritic only. De Co et al. (20) preented and characterized a flexible uniplanar AMC baed on reflection coefficient phae under flat and creeping condition. Liu et al. (2008) propoed a trial and error 269 method to evaluate the effect of curvature on the reflection phae characteritic of an AMC tructure. By oberving the change of the correponding frequency band of return lo of different length dipole antenna veru inphae reflection, the effect of curvature on the reflection phae i determined. Raad et al. (202) propoed a ytematic approach to characterize the performance of a flexible HIS when ubjected to different extent of bending i propoed. The performance of an array of quarepatch baed HIS under variou bending extent wa invetigated a a benchmark. According to the reflection phae analyi, a hift to a higher reonant frequency i oberved in addition to bandwidth degradation when the degree of bending i increaed. It i worth mentioning that the reported tudy could be applied to different HIS geometrie depending on the targeted application. 5. CONCLUSION The integration of High Impedance Surface (HIS) within modern wirele ytem i becoming increaingly popular nowaday due to their beneficial propertie. Conitently, flexible electronic are drawing much attention and are on a fat track to commercialization. Thi triggered the need for an article to ytematically review the tatu of the flexible and conformal HIS reearch. A theoretical background wa provided in the firt ection, followed by an extenive literature review decribing deign and application of flexible HIS. Finally, flexibility analye which are needed to characterize the performance of uch tructure under operational bending and flexing effect are reviewed. It wa concluded that thi type of tudy i vital when deigning HIS tructure for flexible and conformal application due to their conequent parameter change. 6. REFERENCES Bai, L., A.L. Goldman and J.R. Carlon, Poitive and negative regulation of odor receptor gene choice in Droophila by acj6. J. Neuroci., 29: DOI: 0.523/JNEUROSCI Cai, X.H., B. An, X.W. Lai, Y.P. Wu and F.S. Wu et al., Reliability evaluation on flexible RFID tag inlay packaged by aniotropic conductive adheive. Proceeding of the 8th International Conference on Electronic Packaging Technology, Aug. 4-7, IEEE Xplore Pre, Shanghai, pp: -4. DOI: 0.09/ICEPT

5 Cota, F., S. Genovei and A. Monorchio, On the bandwidth of high-impedance frequency elective urface. Proceeding of the IEEE Antenna and Wirele Propagation Letter, Dec. -3, IEEE Xplore Pre, pp: DOI: 0.09/LAWP De Co, M.E. and F. La-Hera, 202. Novel uniplanar flexible artificial magnetic conductor. Int. J. Antenna Propagat., 09: DOI: 0.007/ De Co, M.E., Y. Alvarez, R. Hadarig and F. La-Hera, 20. Flexible uniplanar artificial magnetic conductor. Proceeding of the 5th European Conference on Antenna and Propagation, April - 5, IEEE Xplore Pre, Rome, pp: Farahani, H.S., M. Veyi, M. Kamyab and A. Tadjalli, 200. Mutual Coupling Reduction in Patch Antenna Array Uing a UC-EBG Supertrate. IEEE Antenna Wirele Propagat. Lett., 9: DOI: 0.09/LAWP Hertleer, C., H. Rogier, L. Vallozzi and L. Van Langenhove, A textile antenna for off-body communication integrated into protective clothing for firefighter. IEEE Tran. Antenna Propagat., 57: DOI: 0.09/TAP Huang, Y., J. Chen,. Yin and Y. Xiong, 20. Roll-toroll proceing of flexible heterogeneou electronic with low interfacial reidual tre. IEEE Tran. Component Packag. Manufact. Technol., : DOI: 0.09/TCPMT Kim, D. and J. Yeo, Low-profile RFID tag antenna uing compact AMC ubtrate for metallic object. IEEE Antenna Wirele Propagat. Lett., 7: DOI: 0.09/LAWP Liu, T., X.Y. Cao, J. Ma and W. Wang, Effect of curvature on reflection phae characteritic of electromagnetic band-gap tructure. Proceeding of the Global Sympoium on Millimeter Wave, Apr. 2-24, IEEE Xplore Pre, Nanjing, pp: DOI: 0.09/GSMM Nathan, A. and B.R. Chalamala, Special Iue on Flexible Electronic Technology, Part : Sytem and Application. IEEE Proc., 93: DOI: 0.09/JPROC Palikara, G.K., A.P. Fereidi and C.G. Parini, 20. Advance in conformal metamaterial antenna uing High Impedance (HIS) and Electromagnetic Bandgap (EBG) urface. Proceeding of the 5th European Conference on Antenna and Propagation, Apr. -5, IEEE Xplore Pre, Rome, pp: DOI: Park, J.Y., C.C. Chang, Y. Qian and T. Itoh, 200. An improved low-profile cavity-backed lot antenna loaded with 2D UC-PBG reflector. Proceeding of the IEEE Antenna and Propagation Society Sympoium, Jul. 8-3, IEEE Xplore Pre, Boton, MA, USA, pp: DOI: 0.09/APS Qian, Q., M. Wu, H. Cao, Y. Guo and S. Fang et al., 997. The effect of antiene human Fa RNA on activation induced apoptoi of T cell. honghua, 8: PMID: Raad, H.R., A.I. Abboh, H.M. Al-Rizzo and D.G. Rucker, 202. Flexible and compact AMC baed antenna for telemedicine application. IEEE Tran. Antenna Propagat., 6: DOI: 0.09/TAP Shahid, B., Deign and ynthei of non uniform high impedance urface baed wearable antenna. Phd thei, Loughborough Univerity Intitutional Repoitory. Sievenpiper, D., L.J. hang, R.F.J. Broa, N.G. Alexopolou and E. Yablonovitch et al., 999. High-impedance electromagnetic urface with a forbidden frequency band. IEEE Tran. Microw. Theory Tech., 47: DOI: 0.09/ Yang, F. and Y. Rahmat-Samii, Electromagnetic Band Gap Structure in Antenna Engineering. t Edn., Illutrated, Cambridge, Cambridge Univerity Pre, ISBN-0: X, pp: 266. Yao, H.Y., W. Xu, L.W. Li, Q. Wu and T.S. Yeo et al., Propagation property analyi of metamaterial contructed by conductive SRR and wire uing the MGS-baed algorithm. IEEE Tran. Microwave Theory Technique, 53: DOI: 0.09/TMTT hu, S. and R. Langley, Dual-band wearable textile antenna on an EBG ubtrate. IEEE Tran. Antenna Propagat., 57: DOI: 0.09/TAP