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A Novel Wideband Circular Ring DGS Antenna Design for Wireless Communications
Rakesh Sharma, Abhishek Kandwal, and Sunil K. Khah
Abstract — This paper introduces a novel design of a wideband defected ground circular ring antenna for wireless communication systems. The proposed antenna operates in S-band with the resonating frequency at 3.5 GHz. Designed antenna shows a wideband in the frequency range from 3.3 GHz to 3.9 GHz. The antenna is designed and tested for the calculating the parameters like impedance bandwidth, VSWR and antenna gain.
Index Terms— Defected ground, Wideband, Wireless, Communication
I. Introduction
MICROSTRIP antennas have been rapidly developed in recent years and offer an attractive solution to compact, conformal and low cost designs of many wireless application systems. Microstrip patch antennas are very useful because of their advantages such as light weight, low cost, simplicity in design. Antennas are important contributors for the overall radar cross-section. Efforts have been devoted to minimize the size of microstrip antenna, with a lot of methods proposed recently, such as cutting slots on the patch, using stacked patch, and adopting the substrate with high permittivity, etc. Several techniques have been proposed to enhance the bandwidth in the state-of-the art antenna research. By using the shorting pins or shorting walls on U-shaped patch, U-slot patch, or L-probe feed patch antennas, wideband and dual band antenna with electrically small in size have been reported. Other techniques involve employing multilayer structures with
parasitic patches. Moreover, some structures are engraved in the patch or ground plane to miniaturize the size of
Manuscript received July 14, 2012.
R. Sharma is with the Electromagnetic Analysis Lab, Department of Physics, Jaypee University of Information Technology, Waknaghat, Solan-173234 (H.P.),INDIA; Phone: +91-1792-239221; fax: +91-1792-245362; e-mail: str.phy@gmail.com.
A. Kandwal is with the Electromagnetic Analysis Lab, Department of Physics, Jaypee University of Information Technology, Waknaghat, Solan-173234 (H.P.),INDIA; Phone: +91-1792-239221; fax: +91-1792-245362; e-mail: kandwal_abhishek@rediffmail.com.
S. K. Khah is with the Electromagnetic Analysis Lab, Department of Physics, Jaypee University of Information Technology, Waknaghat, Solan-173234 (H.P.),INDIA; Phone: +91-1792-239221; fax: +91-1792-245362; e-mail: sunil_khah@rediffmail.com.
antenna [1-5]. The rapid advancement in wireless communication has attracted the interests in microstrip antennas. With the wide spread proliferation of wireless communication technology in recent years, the demand for compact, low profile and broadband antennas has increased significantly. To meet the requirement, the microstrip patch antenna has been proposed because of its low profile, light weight and low cost. Now days defected ground structure (DGS) microstrip patch antennas have been rapidly developed for multi-band and broad band in wideband communication systems [6-11].
In the present communication a novel circular ring microstrip antenna with DGS is proposed. The proposed antenna design is analyzed by simulation software CST Studio Suit and experimentally tested using vector network analyzer. Calculations are thus carried out for calculating the impedance bandwidth, voltage standing wave ratio, input impedance and radiation properties such as antenna gain and side lobe level.
II. Antenna design
The geometry consists of a circular ring microstrip antenna with a defected ground as shown in figure (1). The circular ring antenna with DGS is designed on a commercially available glass epoxy substrate of dielectric constant 4.1 and height 1.59mm respectively. A circular ring of outer radius 23.5mm and inner radius 10mm is printed over the substrate material. Defect is introduced in the ground plane by removing metal strips of 2mm width from the ground plane below the circular ring symmetrically as shown in the figure. The antenna is fed by a coaxial probe at 13mm from the centre of the ring.
Figure 1(a,b) shows the top and bottom view of defected ground structure circular ring microstrip antenna design. The prototype of the antenna design is shown in figure (2). Figure 2(a) shows the top view and figure 2(b) shows the bottom view of the defected ground structure. The dimensions of the antenna structure are also shown in figure 2(a) and 2(b). The proposed has dimensions of (52 mm x 52 mm) with a < b, where ‘a’ is the inner radius and ‘b’ is the outer radius of the proposed circular ring defected ground antenna.
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III. Results and discussion
Fig. 1. Geometry of defected ground structure circular ring microstrip antenna design (a) top view (b) bottom
a
b
Fig. 2. Prototype of defected ground structure circular ring microstrip antenna design (a) top view (b) bottom view
Results are compared for both the antenna structures, structure without defected ground plane and structure with defected ground plane. Parameters such as return loss, input impedance, bandwidth for the cases are measured, calculated and compared. simulations are carried out using simulation software and vector network analyzer is used for experimental measurement purposes.
For the first case, when the ground plane for the designed antenna is not defected and covers whole of the substrate, the simulated and experimental graph of return loss is shown in figure 3. From the graph, we can see that the antenna shows a good return loss but not showing wide band characteristics. The antenna shows a bandwidth of about 5.8 % and 6.05 % for simulated and experimental respectively.
Fig. 3. Simulated and experimental return loss variation with frequency (without defect)
For the second case, when the defect in the ground plane is introduced, the antenna shows a wide band. The simulated and experimentally measured return loss is shown in figure 4.
Fig. 4. Simulated and experimental return loss variation with frequency (with defect)
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From this figure, we can see that the antenna shows a wideband in the frequency range of 3 - 4 GHz with good impedance matching. The antenna resonates at the frequency 3.5 GHz in the frequency range from 3.3 GHz to 3.9 GHz. The simulated impedance bandwidth calculated from the graph is 16.3 % and the experimentally measured bandwidth is about 16.6 %. The impedance curve is also shown in figure 5.
Fig. 5. Simulated and experimental input impedance variation with frequency (with defect)
A good impedance matching is obtained at the resonant frequency 3.5 GHz. Both the simulated and experimental results are in good agreement with each other.
The voltage standing wave ratio (VSWR) both simulated as well as experimentally measured is also shown in figure (6). For the frequency range 3.3 GHz to 3.9 GHz, the entire VSWR curve is < 2.
The simulated radiation pattern for the defected ground antenna structure is shown in figure 6.
D
1 DO
| Freq. I'Fl - 3.S Ghfa |
Fig. 6. Radiation pattern (with defect) for Directivity Abs (Phi = 90) between Theta/Degree vs. dBi for frequency F = 3.5 GHz
The polar plot is plotted for directivity Abs (Phi = 90) between Theta/Degree vs. dBi for the resonant frequency 3.5 GHz. in the main lobe direction 179.0 degree, the antenna gain obtained is 7.0 dBi. Within 3 dB angular width in the direction 75.3 degree, the side lobe level obtained is also reduced to a good extent of about -8.3 dB.
Therefore from the above results, we can observe that the defect in the ground plane results in the bandwidth enhancement with good radiation characteristics thereby reducing the overall size of the antenna structure. In the proposed antenna structure also, we obtain wide band with improved radiation characteristics.
IV. Conclusion
A novel defected ground microstrip ring antenna with a defected ground is presented and discussed. It is therefore observed that by introducing the defected ground plane, the characteristic properties are improved. Bandwidth of the antenna is increased to 16 % which is very good for wideband applications with a reasonable antenna gain and side lobe level. The proposed antenna is applicable for various wideband communication systems and wireless applications.
References
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[9] F. E. Fakoukakis, S. G. Diamantis, A. P. Orfanides, and G. A. Kyriacou, “Development of an adaptive and a switched beam smart antenna system for wireless communications,” Journal of Electromagnetic Waves and Applications, vol. 20, no. 3, pp. 399408, 2006.
[10] D. M. Pozar, and D. H. Schaubert, Microstrip Antennas: The Analysis and Design of Microstrip Antennas and Arrays. New York, IEEE Press, 1995.
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