In this paper, Miniature Encoche Coplanar antennas are proposed. Tovalidate our structure and to develop an analytic method to determine thegeometry parameters, the Lumped theory is used. The proposed structure issimulated using ADS and then Compared to the electrical Model. Theproposed circuit has the same resonant aspect when comparing to theEncoche antenna with a much reduced simulation time. The compactcoplanar antenna has a box with a size of 36*52*0.2 mm3. This antenna willbe designed to an RFID TAG that resonates on 2.45 GHz.DOI:http://dx.doi.org/10.11591/ijece.v3i3.257

Ferchichi, Abdelhak

Gharsallah, Ali

English

Institute of Advanced Engineering and Science

International Journal of Electrical and Computer Engineering (IJECE) Vol. 3, No. 3, June 2013, pp. 386~391 ISSN: 2088-8708  386   Journal homepage: http://iaesjournal.com/online/index.php/IJECE A Circuit Model to an Encoche Coplanar Antenna for a Radio Frequency Identification TAG   Abdelhak Ferchichi, Ali Gharsallah Unit of research Electronics HF Systems and Circuits, Faculty of Science, El Manar Univercity    Article Info  ABSTRACT Article history: Received Mar1, 2013 Revised Apr 22, 2013 Accepted May 24, 2013  In this paper, Miniature Encoche Coplanar antennas are proposed. To validate our structure and to develop an analytic method to determine the geometry parameters, the Lumped theory is used. The proposed structure is simulated using ADS and then Compared to the electrical Model. The proposed circuit has the same resonant aspect when comparing to the Encoche antenna with a much reduced simulation time. The compact coplanar antenna has a box with a size of   36*52*0.2 mm3. This antenna will be designed to an RFID TAG that resonates on 2.45 GHz. Keyword: Encoche antenna Coplanaire  Lumped elements RFID TAG Copyright © 2013 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: Abdelhak Ferchichi,  Unit of research Electronics HF Systems and Circuits, Faculty of Science,  El Manar Univercity Rommana 1068, Tunis, Tunisia. Email: abdelhakferchichi@yahoo.fr   1. INTRODUCTION RFID technology has a bright future in a future where all or objects that surround us can communicate with each other through a network such as the Internet thanks to RFID chips, this vision is called "Internet of Things". It is based on the concept of ubiquity whose goal is to provide easy communication with any object, any time and in any place. So if we ever get to this stage, there will be a disruption of our daily lives. In fact, RFID tags will be present everywhere, not only in our identity cards and passports, but also in all objects, even inside our bodies. This is the digital revolution of the next years, where all the objects that surround us can communicate with each other autonomously making the daily lives of human beings more comfortable, [1]-[6].  Some protests not reason to exist because RFID technology itself has several variants that differ mainly seen from the point of reading distance. But the problem is that the majority of actors in civil society are not expert in the technical aspects of RFID technology. This could slow down the deployment of RFID technology. However, history shows that any technology that can increase the comfort of the everyday life of citizens, managed to win despite any inconvenience that may arise. Currently there is a need to develop an identification system for managing communication in different applications. This is because currently, there is a great difficulty for simplify identification and control operations. In the last years, many works are developed to offer an important antenna for RFID applications. In our case, we focus on RFID TAG antenna where we need to propose a miniaturized structure with acceptable parameters. In order to achieve this goal, we have seen some recent publications. First, H-D.Chen et all design a miniaturized coupled Fed TAG antenna, in their work, the polarization was circularly and the structure is mounted in a metallic surface, [7]. In [8], C-H-Lin et all present a miniaturized Inverted–F Antenna, the structure is designed to on-body communication and resonate on 2.45 GHz. Third, IJECE ISSN: 2088-8708   A Circuit Model to an Encoche Coplanar Antenna for a Radio Frequency... (Abdelhak Ferchichi) 387R.O.Ouedraogo et all use the metamaterial techniques to propose a miniaturized patch antenna with CSSR structure, [9]. In [10], Z.Fang et all present a dipole for an active RFID TAG. This paper is organized as follow, in the first section we will describe an ordinary planar Encoche antenna which resonate on 2.45GHz. In the second section, a novel coplanar Encoche is designed and simulated. In the third paragraph we build an electrical model to the two structures of Encoche antenna. Finally, we conclude our paper and we suggest some perspectives.            2. AN ENCOCHE PLANAR ANTENNA  a. Geometry The proposed geometry is a classical Encoche planar antenna. The structure is designed to resonate at 2.45 GHz and it is mounted on a substrate material with a thickness h = 1.6 mm. the used substrate is the FR4 epoxy, Figure 1.       Figure 1. An Encoche planar antenna Figure 2. The geometry dimension of the Encoche antenna   The geometry dimension of the box containing the antenna is about 58*74*1.6 mm, Figure 2 b.  Simulation Results The proposed antenna is simulated using ADS. As be shown in figure 3, the resonant frequency is equal to 2.45GHz, one of the RFID frequencies. The Band width is about 80MHz. which is acceptable for an RFID TAG.   Figure 3. Simulation Results of Encoche planar antenna   3. COPLANAR ANTENNA AND ANALYSIS  a. Coplanar Technique Coplanar lines are excellent waveguides integrated. They are low-cost technology, easily achievable and propagate quasi-TEM mode. Coplanar lines have a characteristic that differentiates them from other 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3x 109-25-20-15-10-50Ghz |s11|dB ADS   ISSN:2088-8708 IJECE Vol. 3, No. 3, June 2013:  386–391 388types of lines: all conductive strips are located on the same plane of the substrate. They have the advantage of being less dispersive compared to other types of lines.  The   configuration of fields in a CPW is different when compared to planar structure. The fields are not entirely confined in the dielectric and extend in the air above the substrate. This contributes to the dispersion and radiation. The currents are highly concentrated in the edges of the conductor which increases the losses that the edges are rougher than the surface. The magnetic field is quasi-planar above the central strip, and rotates around the ribbon. The electric field is substantially planar in the slots, and loop tape to the ground planes. CPW lines are well suited for the connection of lumped elements in parallel. CPW lines have resonances dimensional when their length is of the order of a fraction of a wavelength, for example half-wave, which means only some frequencies, can be stationary wave and there is an absorption peak of the transmission.  b. Geometry   The Encoche coplanar geometry is different to planar one. The difference is that the gound and the patch are in the plane. We used the same substrate (FR4 epoxy). The proposed antenna is more compact and the high of substrate is only 0.2mm, Figure 4    Figure 4. The Geometry of an Encoche Coplanar Antenna   The box containing antenna has a size equal to 36*52*0.2mm, which means a reducing of size of the antenna. The compact antenna will be very important in the case of RFID TAG.  c. Simulation Results The reflection coefficient S11 of the antenna shows a resonant frequency of about 2.45 GHz with a bandwidth of about 70MHz, Figure5. In addition, the gain is about 5.7 dB and the directivity is about 6.12 dB. The proposed antenna has acceptable characteristics for RFID systems.   Figure 5. Return Loss of Encoche Coplanar Antenna   4. ELECTRICAL MODEL OF ENCOCHE COPLANAR ANTENNA  a. Electrical Model Technique To design antenna structures, many techniques are developed. These techniques use numerical methods based on solving the electromagnetic equations in different form. For this reason, a lot of software 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3x 109-25-20-15-10-50Ghz |s11|dB ADSIJECE ISSN: 2088-8708   A Circuit Model to an Encoche Coplanar Antenna for a Radio Frequency... (Abdelhak Ferchichi) 389has been used as ADS simulator, simulator HFSS, CST Microwave. These simulators give their full results solve the electromagnetic equations in their integral or differential forms. Those techniques can be useful in some applications but they present some limits.  Firstly, we cannot take in account all kind of losses. In addition, after the simulation structures, we have no ability to control the antenna parameters such as yield loss, input impedance when modifying the geometry of the antenna, the type of substrate.  Therefore, the replacement of an antenna by an equivalent circuit is very important in the parametric analysis of the proposal structure. In this way, the model techniques are of great interest. One of these solutions is modeling of an antenna by an electric model. Construction of an electrical model means replacing antenna by a RLC circuit. As shown in previous work, [11]-[13], the electric model is used in different applications to simplify antenna design operation. In the next section, we will build an electrical model to both planar and coplanar antenna. The importance of the lumped circuit will be seen in analytic discussion of Encoche coplanar antenna.  b. Circuit Model of Encoche planar Antenna The electrical model was built using the same technique as a single patch but with a few different. We followed the steps below: 1. The excitation line is replaced by the electric model of a single patch where the parameters r, s and c are determined using the equations developed in [11]; 2. The active patch is modeled by two resonant cavities. Parameters R, L and C are calculated using the same equations of rectangular patch described in our previous works[12]; 3. A coupling capacitance Cc is integrated in the structure to introduce the coupling between the excitation line and the two resonant cavities, [13]. The model is described in the figure below, Figure 6.      Figure 6. Electrical model of Encoche planar Antenna Figure 7. Simulation results of Electrical model of Encoche planar Antenna   Simulation of our structure and the electrical model give us the results shown in Figure 7. According to the above figure, we can see that there is a good agreement between the results obtained using either the ADS or the electric model with a slight difference in bandwidth. Given the accuracy of the model built electric and speed, it was thought to control the bandwidth of this structure in the parameters of the proposed model. Our study showed that the variation of the coupling capacitance Cc modifies the BP. Indeed, Cc depends essentially on the distance between the line and the two excitation cavities forming the rectangular patch.  c. Circuit Model of Coplanar Encoche Antenna To build the electric model of the proposed antenna, we tried to study the geometry and introduce a specific model. The major problem in our case is the absence of ground plane unlike the planar patch that allowed us to change the technical construction of the electric model, Figure 8. This technique can be described by the following steps: 1. Determine the resonance resistance R reflecting all losses in the patch: losses in the metal, the dielectric losses, radiation losses    ISSN:2088-8708 IJECE Vol. 3, No. 3, June 2013:  386–391 3902. Determine the total capacitance C of the structure which is composed of 4 capacities: -Two capacitances of the two resonant cavities, C1  -Two coupling capacitances between the two lines forming the CPW ground plane and the two resonant cavities, Cc1 - Two coupling capacitances between the excitation line and the two resonant cavities, Cc2 - 2 capabilities gap between the excitation line and the two lines of the CPW ground plane, Cg Finally, the total capacitance can be obtained by using the equation bellow:  1 1 22 2 2 2                                             ( 1 )c c gC C C C C      3. Determine the total inductance L for the resonance frequency equal to 2.45 GHz The simulation results of the proposed model are shown in figure 9. As can be seen, we obtain the same resonant frequencies with a few differences in the band width. The variation of the band width can be resolved by an analytic discussion of the different parameters models.      Figure 8. Electrical model of Encoche Coplanar Antenna Figure 9. The reflexion Coefficient of Encoche Coplanar Antenna   d. Comparaison between the Encoche Antenna When comparing the different parameters of the two proposed antenna, we can see the added value by using a Coplanar Encoche antenna and the simplification of the task by using circuit model, Table 1:   Table 1. A Comparaison between the two proposed Encoche Antenna    5. CONCLUSION A compact Encoche coplanar antenna is developed and proposed in this paper. The antenna is designed to an RFID TAG and it presents many advantageous comparing to a classical planar Encoche antenna. The use of a simple and an efficient circuit model was very useful and helps us to do a good analytic study. Besides, the simulation time was reduced which means a fast tools of simulation.   IJECE ISSN: 2088-8708   A Circuit Model to an Encoche Coplanar Antenna for a Radio Frequency... (Abdelhak Ferchichi) 391REFERENCES  [1] K Finkenzeller. RFID Handbook. 2nd Edition. 2003 [2] NC Karmakr. Handbook of Smart Antenna for RFID Systems, New York: Wiley-Interscience. 2010: 423. [3] Amir Galehdar, David V Thiel, Steven G O’Keefe. Antenna Efficiency Calculations for Electrically Small, RFID Antennas. IEEE antenna and wireless propagation letters. 2007; 6: 156-159. [4] G Marrocco. The art of UHF RFID antenna design: impedancematching and size-reduction techniques. IEEE Ant. Propag. Mag., 2008 ; 50(1) : 66–79. [5] Paredes, F Gonzalez, GZ Bonache, J Martin F. Dual-Band Impedance-Matching Networks Based on Split-Ring Resonators for Applications in RF Identification (RFID). IEEE Transactions on Microwave Theory and Technique. 2010; 58: 5: 1159-1166. [6] A Venna, E Perret, S Tedjini. High-Capacity Chipless RFID TAG Insensitive to the polarization. IEEE Transaction on antenna and propagation. 2012; 60(10).  [7] HD Chen, SH Kuo, CYD Sim, CH Tsai. On Coupling-Feed Circularly Polarized RFID Tag Antenna Mountable on Metallic Surface. IEEE Transaction On Antenna and Propagation. 2012; 60(5).  [8] CH Lin, K Saito, M Takahachi, K Ito. On Coupling-Feed Circularly Polarized RFID Tag Antenna Mountable on Metallic Surface. IEEE Transaction On Antenna and Propagation. 2012; 60(9).  [9] RO Ouedraogo, EJ Rothwell, AR Diaz, K fuchi, A Temme.  Miniaturisation of patch antenna using a Metamaterial-Inspired Technique. IEEE Transaction On Antenna and Propagation. 2012; 60(5).  [10] Z Fang, R Jin, J Geng. Asymmetric dipole antenna suitable for active RFID tags. Electron. Lett., 2008; 44(2): 71-72. [11] A Ferchichi, N Fadlallah, N Sboui, A Gharsallah. Analysis and design of Printed Fractal Antenna by Using an Adequate Electrical Model. International Journal of Communication Networks and Information Security IJCNIS. 2009; 1(3). [12] A Ferchichi, N Sboui, A Gharsallah. An Electrical Model to Sierpenski Gasket Patch Antenna. The Fifth Advanced International Conference on Telecommunications AICT. MAI. Italy. 2009: 284-288. [13] A Ferchichi, N Fadlammah, A Gharsallah. Novel electrical model to an antenna array, 27th Annual Review of Progress in Applied Computational Electromagnetics ACES. USA, Williamsburg, Virginia '2011 ACES. 2011; 689-694.   BIOGRAPHIES OF AUTHORS   Abdelhak Ferchichi is an Assistant Professor of electrical engineering. Since 2006 he has been with the faculty of Science of Tunis. His current research includes Antenna, RFID Technology, and Substrate Integrated Waveguide SIW.           Ali Gharsallah is a Professor of electrical engineering. Since 1991 he has been with the Faculty of Science of Tunis. His current research interests include antennas, multilayered structures and microwave integrated circuit.         

A Circuit Model to an Encoche Coplanar Antenna for a Radio Frequency Identification TAG

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A Circuit Model to an Encoche Coplanar Antenna for a Radio Frequency Identification TAG

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