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UWB Bowtie 2 x 2 Array Antenna for UWB Mobile Communication System

M.A. Othman1, M.H. Radzi 1,2, M.Z.A. Abd Aziz1, M.M.Ismail1, H.A. Sulaiman1, M.H. Misran1, M.A. Meor Said1, R.A. Ramlee1

1Centre for Telecommunication Research and Innovation, Fakulti Kej. Elektronik dan Kej. Komputer,

Universiti Teknikal Malaysia Melaka, 76100 Durian Tunggal, Melaka, Malaysia.

2Jabatan Kejuruteraan Elektrik,

Politeknik Ungku Omar, Jalan Raja Musa Mahadi,

31400 Ipoh, Perak, Malaysia.

1azlishah@utem.edu.my, 1,2hamizan@jke.puo.edu.my, 1zoinol@utem.edu.my, 1muzafar@utem.edu.my, 1asyrani@utem.edu.my, 1harris@utem.edu.my, 1maizatul@utem.edu.my, 1ridza@utem.edu.my

Abstract — In this paper, presented an array of 2 x 2 UWB Bowtie antennas for Ultra Wide Band (UWB) mobile communication is being proposed. The antenna designs have been simulated using CST Microwave Studio. The antenna covers the UWB spectrum from 4.0 to 10.6 GHz, and had a return loss below than 10 dB throughout the entire band. A compact antenna area of 56.4 x 76.0 mm2 is obtained. The material used is FR-4 epoxy glass substrate that has dielectric constant, 4.4=rε and the dielectric thickness; .6.1 mmh = The antenna also gives omni directional radiation characteristics with reasonable gain values over the same frequency band. Keywords— array Bowtie antenna, return loss, gain, VSWR, radiation pattern.

I. INTRODUCTION Recently, wireless communication systems have

experimented very fast. Since the growth from one generation to another generation, starting from the first generation (1G) analogue voice signal to the next generation of fourth generation (4G) mobile technology. The main target for application of the Ultra Wideband arrays leads to small beam width side lobes for free sparse arrays with the large element spacing. However, this technology of the wireless communication still wants to improve to satisfy the higher resolution and data rate requirements.

After the United States Federal Communication Commission (FCC) announced to allow the unlicensed for public to use the UWB frequency band from 3.1 to 10.6 GHz for communication systems in 14 February 2002 [1], there has been a great news for world to improve and commercial UWB technology.

In this paper, an array of 2 x 2 bowtie antenna has been designed to improve gain, antenna beam, bandwidth and

reliability of the mobile communication system. These performances can be archive by designed using multiple antenna elements, compared to the single array of the antenna. The array antenna structure is very interesting to explore and it is widely applicable to increase the performances range and reliability [2]-[4] of Wi-Fi LAN network, Bluetooth system, PDA (Personal Digital Assistants) DCS (Digital Communication System) and also for mostly application in the field of mobile communication system. This type of antenna is used extensively in many applications such as ground penetrating radar [5], wireless communications and mobile station [6]. In UWB antenna design, several bow-tie based configurations have been reported [7-9].

This paper will discuss the UWB bowtie array antenna design in section II while the performance simulation results will be discuss in section III. In the last section, the conclusion section will conclude about the design and the performance of the UWB bowtie antenna design. The design of the antenna is simulated and optimized by using CST 2009.

II. UWB BOWTIE 2 X 2 ANTENNA ARRAY DESIGN In designing an antenna, the selection of substrate can be

used to archive a good response and the dielectric constant are usually used in range of 2.2 ≤ Ɛ ≤ 12. The most suitable substrate for the good antenna performances is normally thick substrate, which is at the lower end. In is because, this range provides better performances compared to the thin substrate [7]. Generally the design of the array antenna, usually are similar with the each other. It is because the antenna is the key element in a microwaves technology. The structure of an array 2 x 2 bowtie antenna is designed on FR4 substrate with the dielectric Ɛr = 4.4 and thickness 1.6 mm.

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Figure 1: An array 2 x 2 bow tie antenna

Figure 2: The structure of 2 x 2 bow tie antenna (front view of the antenna)

The structure of the full-size antenna is shown in Figure 1 and 2above. The material used is FR-4 epoxy glass substrate that has dielectric constant, ,4.4=rε and the dielectric thickness, =h 1.6mm with the size of W×L = 56.4 x 70.0 mm2. Microstrip lines having 50Ω input impedance are used for feeding the antenna as shown in Figure 3. The width of the feed line is wf = 5.0 mm, with the height of the feed, hr=14.3 mm. The bowtie triangular size was set at 8.5 mm x 8.8 mm x 8.8 mm while the circle radius was set at 7 mm. Four bowties antennas was placed on the front and the back of the FR4 as shown in figure 4 and 5. The parameter of every element in the antenna has been discussed in this section. The parameter that needed to be applied onto Computer Simulation Tool (CST 2009) microwaves environment software programming. The distance between the antenna elements at the right side and the left side is 21.6 mm.

Figure 3: The measurement of 2 x 2 bow tie antenna (front view of the antenna)

Figure 4: The structure of 2 x 2 bow tie antenna (back view of the antenna)

Figure 5: The measurement of 2x2 bow tie antenna (back view of the antenna)

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III. RESULTS AND DISCUSSIONS Figure 6 shows the result of return loss where from the

figure the good result was obtained at frequency between 4.1 GHz until 9.5 GHz with the value of return loss under -10dB and below. It is because the intended design frequency has a value of under -10dB. The figure 4 also shown that, the best performances for S11 parameter of return loss value are -27 dB. But the result for S11 parameter only covered at the middle area of the UWB frequency range.

Figure 6: The S11 result for an array 2 x 2 bow tie antenna at range 3-11 GHz

When the impedances terminate the transmission line cable,

not all of the power are terminated and absorbed by the termination. Several part of the power is reflected back to the termination line. This incident signal is mixes with the reverse signal to cause the voltage standing wave pattern on the transmission line. The ratio of the maximum to minimum voltage is known as VSWR, or Voltage Standing Wave Ratio. In this design case, the value of the VSWR obtained in the figure 7. The result show that the VSWR value is under 2 which is considered a good result [5] although in the real world a value of VSWR 1.2 is considered excellent in most case. Although that the below under 2 is still valid to considered the VSWR are in good result.

Fig. 7: The VSWR value for the range 4.1-9.5GHz

The simulated array bow-tie antenna radiation patterns for the resonant frequencies are shown in Figure 8 respectively. The main lobe obtained for bow-tie antenna of 8 GHz has a magnitude of 2 dB with 160° and the 3dB angular width is

122.9°. From the simulation results, the wave is radiated in all directions.

Figure 8: The polar pattern of 2 x 2 bow tie antenna

Performances simulation and evaluation on array 2x2 bow tie antenna is similar like result as shown in the table 1 below;

Type E-Field (peak) Mode type Quasi TEM Line Impedances 50.2083 Ω Wave Impedances 224.718 Radiation efficiency -0.7990 dB Total efficiency -1.070 dB Realized gain 4.76 dB

Table 1: The summary of the simulation result for 2x2 bow tie antenna.

IV. CONCLUSION In this paper, the design and analysis of the UWB bowtie 2

x 2 array antenna has been discussed. Overall, the performances of the UWB bowtie 2 x 2 array antenna meets the desired suitable requirements in term of return loss, Voltage Standing Wave Ratio (VSWR), bandwidth, gain and radiation pattern. The best performance for S11 parameter is -27 dB at 5.6 GHz which mean considered suitable and valid for mobile communication system application. This antenna can be implemented in mobile communications system as high-speed data transfer between devices. For the future work, several factors such as feeding technique, types of substrate, the thickness, structure pattern of the antenna design and dielectric constant of the substrate can be improved respectively.

REFERENCES

[1]. Federal Communication Commission, “First Report and Order,

Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wideband Transmission System”, FCC02-48, Apr. 2002.

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Wideband Base Stations”, IEEE Antennas and Propagation Magazine, Vol. 46, No. 1, pp. 158–167,February 2004.

[3]. R. Comitangelo, D. Minervini, B. Piovano, “Beam Forming Networks of Optimum Size and Compactnessfor Multibeam Antennas at 900 MHz”, IEEE Antenna and Propagation International Symposium, Vol. 4, pp.2127-2130, July, 1997.

[4]. R. G. Vaughan and J.B. Anderson, “Antenna Diversity in Mobile Communications,” IEEE Trans. Antennas and Propagation, vol. 49, no 3. pp. 954-960,June 1987.

[5]. Elizabeth Rufus, Zachariah C Alex, and P Vivek Chaitanya, “A modified Bow-Tie Antenna for Microwave Imaging Applications.” Journal of Microwave, Optoelectronics and Electromagnetics Application, Vol. 7, No. 2, pp. 115-122, 2008

[6]. B. Saidaiah, A. Sudhakar and K. Padma Raju, “Modeling and Analysis of an Efficient Bow-Tie Antenna for UWB Applications,” International Journal of Emerging Technology and Advanced Engineering, Vol 2, No. 10, pp. 158-163, October 2012.

[7]. M. Fernando, K. Busawon, M Elsdon and D. Smith, “Fundamental Issues in Antenna design for Microwave Medical Imaging Applications,” 7th International Symposium on Communication Systems Networks and Digital Signal Processing, pp. 795 – 800, 2010.

[8]. S.   Didouh,   M.   Abri   and   F.   T.   Bendimerad,   “Multilayered   Bow-­‐tie  Antennas   Design   for   RFID   And   Radar   Applications   Using   A   Simple  Equivalent   Transmission   Line   Model”,   International   Journal   of  Computer   Networks   &   Communications,   Vol.4,   No.3,   pp.   121-­‐126,  May  2012.  

[9]. Kulwinder Singh, Yadwinder Kumar and Satvir Singh, “A modified bow tie antenna with U-shape slot for Wireless applications”, International Journal of Emerging Technology and Advanced Engineering ,Vol. 2, Issue 10, pp. 147-152, 2012.

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