Microstip Antenna with a Reconfigurable Dumbbell-Shaped Defected Ground Plane

for DCS-1800 and PCS-1900

Mohammad Mehdi Fakharian, Pejman Rezaei, and Ali Asghar Orouji Department of Electrical and Computer Engineering

Semnan University Semnan, Iran

m_fakharian@sun.semnan.ac.ir

Abstract— A microstrip antenna with reconfigurable Dumbbell-shaped defected ground plane (DGS) is designed and simulated. In the proposed structure, in order to generate frequency diversity at 1.8GHz and 1.9GHz, a DGS with a p-i-n diode is etched on the ground plane. The simulated results by HFSS and CST softwares show the effectiveness of the proposed antenna configuration.

I. INTRODUCTION Reconfigurable antennas play an important role in modern

wireless communication systems, such as personal communications (PC) and digital cellular (DC) services [1]. Moreover, recently there has been a great interest in the implementation of reconfigurable defected ground structures (DGS) where the number and location of the transmission zeros may be controllable [2-3]. In this letter, a dumbbell-shaped reconfigurable DGS resonator for frequency agility between DCS-1800 and PCS-1900 is suggested. The design of the antenna consists of a traditional square patch, and defected ground plane with a p-i-n diode. The full-wave electromagnetic simulations and analysis for the presented antenna are performed using the commercial computer software packages Ansoft HFSS and CST Microwave Studio, which are based on the finite element method and finite integration technique, respectively. The paper is organized as follows; Section II gives the structure description with complete dimensions, Section III gives the simulated response, and Section IV is devoted to the conclusion.

II. ANTENNA DESIGN AND CONFIGURATION The rectangular microstrip antenna fed by a 50-Ω inset

microstrip line is shown in Fig. 1, which is printed on an FR4 substrate of thickness 0.8 mm, permittivity 4.4, and loss tangent 0.02. In this antenna, a Dumbbell-Shaped DGS with a p-i-n diode and a rectangular slot under the patch have been added to the ground plane. In this study, ideal switch models are used to imitate p-i-n diode switch for proof of the concept, i.e., the opened (OFF) and closed states (ON) of the switch are simulated in the absence or presence of a metal pad, respectively.

Figure 1. Geometry of the proposed antenna with reconfigurable DGS resonator.

As illustrated in Fig. 1, the DGS pattern as etched on the ground plane, where a, b, and g1 are the horizontal and vertical length of the aperture and the etched gap distance, respectively. The length of the narrow gap is the same as the width, w1, of the microstrip line on the other plane. DGS section can provide a cutoff frequency in some frequency. It means that DGS section increases the effective permittivity, so that the effective inductance of a microstrip line is increased. The cutoff frequency depends on the etched square area (a × b) in the ground plane. The etched gap, which is placed under a microstrip line, provides the parallel capacitance with the effective inductance [4]. The narrow connecting lines lead to series inductance. In contrast, gaps across the width of the line increase the shunt capacitance. In order to achieve reconfigurable function, a p-i-n diode is embedded across the Dumbbell-Shaped DGS, and its role is removing the effect of the DGS configuration. When the p-i-n diode is biased forwardly, it shorts out the center section of the Dumbbell–shaped DGS.

To optimize the performance of the proposed antenna, a parametric study is also performed, and the final dimensions of the proposed antenna are determined, in which: G=45mm, Ws=40mm, Ls=29mm, W=27mm, L=24mm, Wt=5.9mm, Lt=9.5mm, W1=1.5mm, a=7mm, b=4.5mm, and g1=1.5mm.

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III. RESULTS AND DISCUSSIONS In this section, the printed antenna with reconfigurable

DGS resonator is simulated, and the numerical results of the input impedance and radiation characteristics are presented.

Fig. 2 presents the characteristic of the simulated S11 of the proposed antenna by HFSS and CST softwares. It is seen that the proposed antenna operates from 1.7GHz to 1.9GHz with S11≤ –10dB to cover the DCS-1800 (uplink: 1.71–1.79GHz and downlink: 1.81–1.88GHz), when the p-i-n diode is OFF, and it operate in the 1.8GHz to 2.05GHz band to cower PCS-1900 (uplink: 1.85–1.91GHz and downlink: 1.93–1.99GHz), when the p-i-n diode is ON.

Figure 2. Simulated return loss for the proposed antenna.

Fig. 3 shows the simulated radiation patterns including the co- and cross-polarization in the H-plane (xz-plane) and E-plane (yz-plane) at 1.8 GHz (diode: OFF) and 1.9 GHz (diode: ON). It can be seen that the radiation patterns in xz-plane are nearly omnidirectional for the two frequencies.

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Figure 3. Simulated radiation patterns of the proposed antenna,

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IV. CONCLUSION A reconfigurable patch antenna with switchable DGS for

frequency agility in DCS-1800 and PCS-1900 bands is proposed. The frequency is controlled by only one diode, which is located in the middle of DGS in the ground plane. Good reconfigurable frequency function and radiation performance are obtained from simulations. This proposed antenna has the merits of concise structure and low cost and supports wide applications in wireless communication systems.

ACKNOWLEDGEMENT This research was supported by Semnan University. Also,

the authors would like to thanks the Office of Brilliant Talents at the Semnan University for financial support.

REFERENCES [1] J.L.T. Bernhard, “Reconfigurable Antennas,” Morgan & Claypool

Publishers, 2007 - Technology & Engineering. [2] E.K.I. Hamad, A.M.E. Safwat, and A.S. Omar, “A MEMS

reconfigurable DGS resonator for K-band applications,” Journal of Microelectromechanical Systems, vol. 15, pp. 756–762, Aug. 2006.

[3] H. B. El-Shaarawy, F. Coccetti, R. Plana, M. El-Said, and E. A. Hashish, “Novel reconfigurable defected ground structure resonator on coplanar waveguide,” IEEE Trans. Ant. Propag., vol. 58, pp. 3622–3628, Nov. 2010.

[4] D. Ahn, J.-S. Park, C.-S. Kim, J. Kim, Y. Qian, and T. Itoh, “A design of the low-pass filter using the novel microstrip defected ground structure,” IEEE Trans. Microwave Theory Tech., vol. 49, no. 1, pp. 86–93, Jan. 2001.

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