Design of Modified Bowtie Antenna for Wireless Applications

Design of Modified Bowtie Antenna for Wireless Applications

Bathala V. Sindooja

Post-graduate student Department of Electronics and Communication engineering Karunya University, India

Abstract

Design of modified bowtie antenna for bandwidth enhancement characteristics using CADFEKO software is reported in this paper. In a bowtie antenna, by using triangular elements instead of rods, the bandwidth is greatly increased. The basic bowtie antenna is modified using a coplanar waveguide feed (CPW). The main issue with CPW- fed antennas is to provide an easy impedance matching to the CPW-fed line. The proposed antenna can exhibit minimum return loss, Omni-directional radiation pattern, wide impedance bandwidth, and VSWR<2. Furthermore, the modified antenna is analyzed using different substrate materials.The results portray significant losses in gain when the loss tangent of the material is included in the simulations. From the simulation results it is concluded thatthe bandwidth

T. Anita Jones Mary

Assistant professor Department of Electronics and Communication engineering Karunya University, India

2. DESIGN FORMULATION

An empirical formula of resonant frequency of bow- tie antennas is presented, which is based on the cavity model of microstrip patch antennas as in [2]. A procedure to design a bow-tic antenna using generic algorithm (GA) in whichthe formula is taken as a fitness function is also given. An optimized bow-tic antenna by genetic algorithm is measured. Numerical and experimental results are used to validate the formula and GA.

The design formulae of a bow-tie patch, for the dominant TM10 mode, can be obtained using the equations that follow

of the antenna is improved using the substrate of lower dielectric constant or by increasing the substrate thickness.

f =

r

2

1.152 (1)

Keywords: Bow-tie antenna; CPW; VSWR

1. INTRODUCTION

R = +2 +( +2)(2)

t

2 (+2)(+2)

= 0.412 ( +0.3) +0.262

The commercial pressure of ever-higher data rates

( 0.258 ) +0.813

(3)

and increases in user density are driving the antenna design for

+1

1

12 1 2

mobile wireless communicators to have wide-band response with spatial ability. In radio systems, a biconical antenna is a

=

+

2

1 +

2

(4)

broad-bandwidth antenna made of two roughly conical

= +

(5)

conductive objects, nearly touching at their points. Biconical antennas are broadband dipole antennas, typically exhibiting a bandwidth of 3 octaves or more. A bowtie antenna is a wire approximation in two dimensions of a biconic dipole antenna (used, for example, for UHF television reception). The biconical antenna has a broad bandwidth because it is an example of a travelling wave structure; the analysis for a theoretical infinite antenna resembles that of a transmission line. Bow-tie and bow-tie slot antennas are planar-type variations of the biconical antenna that has wideband characteristics as in [5] and [10]. A number of bow-tie slot designs are introduced, which demonstrate wide BW that range from 17% to 40%. The WIFI frequency is divided into two bands: 2400-2484 MHz and 5150-5850 MHz; Because WIFI is the highest frequency on the mobile device; the WIFI antenna will be the smallest antenna.

The design is carried in FEKO, which is a Method of Moments (MoM) tool that can be used to calculate the radiation pattern, impedance and gain of an antenna while mounted on some defined geometry. In addition, it can calculate the isolation or mutual coupling (S12) between pairs of antennas, the near fields around an antenna and the electric currents that flow on an antenna or the surrounding structure as in [9].

2

Where, Wc is the central gap between the bows, which is made 0 because the antenna is designed from the origin (0,0,0) for the basic bowtie antenna, Rt, is the terminating resistance of the bowtie antenna and l is the extension length due to the fringing effect of the radiating antenna also the parameters, r, h and eare the permittivity of dielectric constant of the substrate, thickness of the substrate and effective permittivity of the substrate respectively and c is the velocity of electromagnetic wave in free space.

Figure 1. CPW fed bowtie antenna

The basic bowtie design is designed in FEKO and shown in figure 2. The simulated CPW feed bowtie is shown in figure 3.

1. CPW FEED

   Following equation gives the tolerance quotient

   Antennas using CPW-fed line as shown in figure 1, have many attractive features including low radiation loss, less dispersion, easy integration for monolithic microwave circuits (MMICs) and a simple configuration with single metallic layer,

   c

   f c 2L r

   1. WIDTH VARAITON

      = 1

      2L 0r 0

      (6)

      since no backside processing is required for integration of devices as in [4],[8],[11]. Therefore, the designs of CPW-fed antennas have recently become more and more attractive. CPW-fed slot antennas with modified shape reflectors have been proposed. By shaping the reflector, noticeable enhancements in both bandwidth and radiation pattern, which provides unidirectional radiation, can be achieved while

      Second, the width W controls the input impedance

      and the radiation pattern. The wider the patch becomes the lower the input impedance. The permittivity rof the substrate controls the fringing fields lower permittivity have wider fringes and therefore better radiation. Decreasing the permittivity also increases the antenna's bandwidth. Following equation gives the tolerance factor

      maintaining the simple structure. Here, the possibility of covering some the standardized WiFi and WiMAX frequency bands while cling to the class of simply structured and compact antennas.

      L 1

      2fc 0 r 0

   2. HEIGHT VARAITION

   (7)

   The height of the substrate h also controls the bandwidth increasing the height increases the bandwidth. The fact that increasing the height of a patch antenna increases its bandwidth can be understood by principle: "an antenna occupying more space in a spherical volume will have a wider bandwidth." The following equation roughly describes how the bandwidth scales with these parameters:

   B r 1 W h (8)

   L

   2

   r

   Figure 2. Basic bowtie antenna in FEKO

   Figure 3. Proposed bowtie antenna in FEKO

2. SUBSTRATE MATERIAL ANALYSIS

   Substrate materials play vital in antenna design, production and finished product performance. A simple method that can be employed to modify the different properties of the antenna is by changing the substrates parameters such as height and dielectric constant of thesubstrate influence the antenna properties. All of the parameters in an antenna design (L, W, h, permittivity) control the properties of the antenna.

   1. LENGTH VARAITION

      First, the length of the patch L controls the resonant frequency. This is true in general, even for more complicated antennas that weave around the length of the longest path on the microstrip controls the lowest frequency of operation.

      The simulations are performed for different substrate configurations of bowtie antenna with Duroid, FR4 and benzo- cyclobuten substrates.

3. RESULTS AND DISCUSSIONS

The radiation pattern of the proposed bowtie anenna with CPW feed is having high directivity compared to conventional antenna and the results are shown in figures 4 and 5.

Figure 4. Radiation pattern of the basic bowtie antenna

Figure5. Radiation pattern of the proposed bowtie antenna

The S-parameters of the basic antenna is given in the figure 6. It gives nearly -15dB respectively.

Figure 6. S11 parameters of the basic bowtie antenna

From the proposed antennas S-parameter graphshown in figure 7, it is shown that the proposed antenna gives a wider bandwidth than the basic antenna structure. Table 1 shows the comparison of bandwidth achieved by the basic bowtie antenna and the proposed bowtie antenna.There is bandwidth enhancement achieved up to 50% in figure 7.

Table 1. Bandwidth Comparison of the basic bowtie antenna and proposed bowtie antenna

The proposed antenna is analyzed on three different substrate materials as mentioned earlier. The S11 characteristics curve for the first substrate – benzo-cyclobuten is shown in Figure8. The S11 value in dB is about -7.

Figure 7. S11 parameters of the proposed bowtie antenna

Figure 8.S11 characteristics of substrate1

The S11 characteristics curve for the second substrate

– Glass is shown in Figure 9. The S11 value in dB is about -7.5

Figure 9. S11 characteristics of substrate2

The S11 characteristics curve for the third substrate – Duroid 6010 is shown in Figure10. The S11 value in dB is about -7.8.

Figure 10. S11 characteristics of substrate3

Table 2. Comparison of the modified bowtie antenna simulated results on different Dielectric Constants

7. REFERENCES

1. Abdelnasser A. Eldek, Atef Z. Elsherbeni Senior Member, IEEE, and Charles E. Smith Life Senior Member (2004), IEEE Wideband bow-tie Slot Antenna with Tuning Stubs Radar Conference, 2004. Proceedings of the IEEE

2. AhmetCemalDurgun, Student Member, IEEE, Constantine A. Balanis, Life Fellow, IEEE, Craig R. Birtcher, and David R. Allee, Member, IEEE (2011) Design, Simulation, Fabrication and Testing of Flexible Bow-Tie Antennas IEEE transactions on antennas and propagation, vol. 59, no. 12, december 2011

3. Chen Wen-jun, Li Bin-hong and XicTao (2004), IEEE A Resonant Frequency Formula of Bowtie Antenna and its Application Antennas and Propagation Society International Symposium, 2004.

   IEEE, Volume: 4

4. Chang-Ju Wu, I-Fong Chen, and Chia-Mei Peng (2011) A Dual Polarization Bow-tie Slot Antenna for Broadband Communications Progress In Electromagnetics Research Symposium Proceedings, Marrakesh, Morocco, Mar. 2023

5. KamyaYekehYazdandoost and Ryuji Kohno (2012) Slot Antenna for Ultra Wideband System Wireless Communications and Applied Computational Electromagnetics, 2005. IEEE/ACES International Conference

6. Kulwinder Singh, Yadwinder Kumar, Satvir Singh A modified bow tie antenna with U-shape slot for Wireless applications International Journal of Emerging Technology and Advanced Engineering ISSN 2250-2459, Volume 2, Issue 10, October 2012)

7. K.V. Rop1, D.B.O. Konditi2 1Department of Telecommunication and Information Engineering Jomo Kenyatta

   Name of the substr atema terial	Permittiv ity of the dielectric , r	Thickn ess of the substra te, h	Loss tange nt,	Fracti onal B.W %	Min VS WR	S11 in dB
   Benzo – cyclob uten	2.6	1.6	0	5	1.2	-7
   Glass	5.5	1.6	0	27	1.5	-7.5
   Duroid 6010	10.2	1.6	0.002 3	7	2	-7.8

   2

   University of Agriculture and Technology, Nairobi, Kenya. Faculty

   The wider bandwidth is due to the lowering the quality factor of the antenna. Both bandwidth and gain decrease as rincreases for perfect dielectric. A linear relationship of 2 dB drops per decade is observed between the gains and ideal revaluated in the range of this study. The bandwidth does not vary for lossy substrates. However, the gains drop linearly by 1.5 dB per decade for increasing r. The results portray significant losses in gain when the loss tangent of the material is included in the simulations

   6.CONCLUSION

   It is analyzed that the CPW feed for the antenna has achieved bandwidth enhancement double the original value. Also the substrates on which the antennas are constructed show that the lower permittivity valued substrate helps in achieving a good antenna performance.

   of Engineering, Multimedia University, Nairobi Kenya. (2012) Performance Analysis of a Rectangular Microstrip Patch Antenna on Different Dielectric SubstratesInnovative Systems Design and Engineering ISSN 2222-1727 (Paper) ISSN 2222-2871 (Online) Vol. 3, No. 8, 2012

8. PrapochJirasakulporn (2008) Multiband CPW-Fed Slot Antenna with L-slot Bowtie Tuning Stub World Academy of Science, Engineering and Technology 24, 2008

9. Siva Agora SakthivelMurugan, K.Karthikayan, Natraj.N.A, Rathish.C.R (2013) A Triband Slotted Bow-Tie Antenna for Wireless Applications International Journal of Computational Engineering Research, Vol:03,Issue, 7

10. Y. Tawk, Student Member, IEEE, K. Y. Kabalan, A. El- Hajj, C. G. Christodoulou, Fellow, IEEE, and J. Costantine, Student Member, IEEE (2008) A Simple Multiband Printed Bowtie Antenna

    IEEE antennas and wireless propagation letters, vol. 7, 2008

11. Yu-Wei Liu, Shih-Yuan Chen, and Powen Hsu(2010) Metal Strip-Embedded Slot Bowtie Antenna for Wi-Fi and WiMAX Applications Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE.