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Novel Design of Ultra Wideband Vertical Slotted Triangular (VST) Sheet Antenna

Anuj Y. Modi Department of Electronics and Communication

Engineering, Institute of Technology/Nirma University

Ahmedabad, Gujarat, India

anujyrmodi@gmail.com

Aarti Gehani Department of Electronics and Communication

Engineering, Institute of Technology/Nirma University

Ahmedabad, Gujarat, India

aarti.gehani@nirmauni.ac.in

Abstract—In this paper, a new design of Ultra Wide Band (UWB) antenna is proposed. The antenna parameters in frequency domain analysis have been investigated to show its capability as an effective radiating element. The voltage standing wave ratio is less than 2 (VSWR< 2) and return loss ( ) is less than -10 dB along the operation bandwidth of 4 GHz to 17 GHz. The simulated return loss, VSWR,input impedance and radiation pattern are presented in this paper.The antenna is very useful for impulse and UWB communication systems (in radar communication, for military application (defense department), bio-medical technology, space communication through satellite) and as proposed antenna has end fire radiation pattern it is very useful in point to point communication with very high gain performance.

Keywords—Ultra wideband (UWB), triangular sheet,

Voltage standing wave ratio (VSWR), Return loss ( ).

I. INTRODUCTION Antenna is the most important part of any wireless

communication system. A wide variety of antennas are available for different applications. Antennas like dipole, monopole, loop, etc. are inherently narrowband antennas. Since the declaration of Ultra-Wideband (UWB) frequencies (from 3.1 GHz to 10.6 GHz) by the Federal Communications Commission (FCC) in 2002 [1], antenna design for this new communications standard has attracted increasing interest. Commercial UWB systems require small low-cost antennas with omnidirectional radiation patterns, large bandwidth and non-dispersive behavior [2]. By means of UWB antennas, high data rate transmission can be obtained in short-range local networks and short-duration pulses. The UWB antennas are used in the applications of UWB communication, medical imaging, ground-penetrating radar, through-wall radar, and precision location systems.

The planar antenna is widely used in the literature [3-7] as UWB antennadue to its wide bandwidth, simple structure and low cost. To design a single antenna with small electrical dimensions and broadband characteristics is a covetable feature in the high-speed data

communication systems. It has become one of the most considerable candidates for UWB application. As seen in the references, several designs of planar UWB antenna have been proposed. However, most of these antennas involve complex calculation and sophisticated fabrication process. Therefore, a simpler method to design the UWB antenna having two triangular metal sheets with vertical slots is proposed. The simulated return loss, VSWR, input impedance and radiation patterns of the antenna are discussed. In order to use the proposed antenna as directional antenna, a cylindrical reflector can be utilized and the radiation patterns of the same are also shown in the paper.

II. VERTICAL SLOTTED TRIANGULAR SHEET ANTENNA

Figure 1. Geometry of the proposed antenna

The structure of the proposed antenna is shown in Fig.1.

The Vertical Slotted Triangular (VST) sheet antenna consists of two triangular metal sheets connected to a SMA connector with their base. One sheet is considered as positive and is connected to the inner pin of SMA

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connector while the other sheet is connected to its outer. The antenna lies in the XZ-plane, and the Y-axis is parallel to its normal direction. The width of triangular metal sheet is 85 mm along the X-direction as indicated in Fig.2 and its length is fixed at 75.0 mm along the Z-direction. It has been studied that the performance of gain and return loss is affected by the width of triangle, the width of triangle, feeding position, width of these slots and number of vertical slots, which are shown in Fig. 2.

(a) (b)

Figure 2. (a) Front view and (b) Side view of the proposed antenna

To get ultra wideband characteristics from 4 GHz to 17

GHz the width of slots has been taken as ratio of width of triangular metal sheet to n, Where,

The width of the triangular sheets is a very critical

parameter to acquire UWB characteristic and higher gain performance. To get notch free ultra wideband characteristics, feeding is offset by 5.0 mm in positive X-direction along the base of triangular metal sheet. The gap between positive and negative plates has been taken as 3.0 mm. The antenna is fed by co-axial cable having SMA connector. Depth of the triangular metal plate has been taken as 1 mm. Finally, the overall physical dimensions of the proposed antenna for optimized performance are given in Table 1. TABLE I. DESIGN PARAMETERS OF THE PROPOSED ANTENNA

Design Parameters Optimized values (mm) 85.0 75.0 5.0 1.0 3.0 5.0 4.0

III. RESULTS AND ANALYSIS The performance of the proposed antenna was

simulated using a full-wave solver. This section discusses simulated return loss, VSWR, input impedance and the radiation patterns for various frequencies over operation bandwidth. Fig. 3 shows that the simulated return loss is less than -10 dB over the entire operation bandwidth (4 GHz to 17 GHz).

Figure 3. Simulated return loss of the proposed antenna

Fig. 4 shows that the simulated VSWR for proposed

antenna is less than 2 (VSWR < 2) over entire operation bandwidth which is very good characteristic as an UWB antenna.

Figure 4. VSWR of the proposed antenna from full-wave solver

Fig 5 shows that the real part of the input impedance

varies between 25 to 75 whereas the imaginary part varies between -20 to 20 .

Figure 5. Real and imaginary part of input impedance

Fig. 6 (a) and 6 (b) shows the simulated radiation

pattern of the proposed antenna in XY plane (horizontal plane) and XZ plane (vertical plane), respectively. The radiation patterns are shown at 5 GHz, 10.5 GHz and 16 GHz.The asymmetrical geometry is used to increase the bandwidth but results in the degradation of the radiation

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pattern. The asymmetry of the radiation pattern is caused mainly by the asymmetry of the feed configuration.

Figure 6. (a) Simulated radiation pattern of the proposed antenna at 5

GHz, 10.5 GHz and 16 GHz in XY plane (Horizontal plane)

Figure 6. (b) Simulated radiation pattern of the proposed antenna at 5

GHz, 10.5 GHz and 16 GHz in XZ plane (Vertical plane)

Proposed antenna has an end fire radiation pattern. In order to use this antenna as directional antenna, a reflector is kept at one side. For example, in fig. 7 (a) and 7 (b) radiation patterns have been plotted with reflecting cylindrical metal plate (having radius 50mm) at . Simulated results of fig. 7 (a) and 7 (b) show the capability of proposed antenna as highly directive antenna.

Any type of reflector can be used but it should be taken into consideration that addition of reflector may result in change in the return loss bandwidth.

Figure 7. (a) Simulated radiation pattern of the proposed antenna at 5

GHz, 10.5 GHz and 16 GHz in XY plane (Horizontal plane) with reflector

Figure 7. (b) Simulated radiation pattern of the proposed antenna at 5

GHz, 10.5 GHz and 16 GHz in XZ plane (Vertical plane) with reflector

IV. CONCLUSIONS In this paper, a Vertical Slotted Triangle (VST) sheet

antenna has been designed for the UWB communication and the narrow pulsed systems. The antenna operates from 4 to 17 GHz. The simulated return loss, VSWR, input impedance and radiation patterns are presented in this paper. It was shown that the asymmetric feed location results in increase in the bandwidth but degradation in the radiation pattern. The antenna is suitable for use in UWB applications as it has the operating bandwidth of 13 GHz i.e. 124 % fractional bandwidth. It can be very useful in radar communication, for military application, bio-medical technology and space communication through satellite.

ACKNOWLEDGMENT Authors would like to specially thank Prof. Dhaval

Pujara at Nirma University for his guidance and support throughout the design and optimization of the proposed antenna. Authors would like to thank Nilima Pisharody and Jigar Mehta at Nirma University for their contributions and suggestions.

REFERENCES [1] “First report and order,” Federal Communications Commission

(FCC), Feb. 2002. [2] H. G. Schantz, The Art and Science of Ultra wideband

Antennas.Boston, MA: Artech House, 2005. [3] Ojaroudi, M., C. Ghobadi, and J. Nourinia, “Small square

monopole antenna with inverted T-shaped notch in the ground plane for UWB application," IEEE Antenna and Wireless Propagation Letters, Vol. 8, 728-731, 2009.

[4] Chen, C., Y.-C. Jiao, L. Zhang, and W.-B. Zhang, “An ultra-wideband monopole antenna with dual band-notched characteristics," Journal of Electromagnetic Waves and Applications, Vol. 23, No. 11-12, 1595-1601, 2009.

[5] Agrawall N.P., Kumar G., and Ray K.P., “Wideband planar monopole antennas”, IEEE Trans. Antennas Propag., Vol. 46, pp.294-295, Feb. 1998.

[6] Evans J.A., Ammann M.J., “Planar trapezoidal and pentagonal monopoles with impedance bandwidths in excess of 10:1”, IEEE Antennas and Propagation Society International Symposium, Vol. 3, pp.:1558 –1561, July 1999.

[7] Chen Z. N., “Impedance characteristics of planar bow-tie-like monopole antennas”, Electronics Letters, Vol: 36 (13), pp. 1100 – 1101, June 2000.