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In this paper, a novel Fractal PIFA antenna for triple-band is presented. The proposed antenna is based on the self affinity and lengthen shorting pin of PIFA structure. The combining design of the F-PIFA antenna is optimized and validated via simulation using CST-MW Studio as well as measurement.
Electronics and Automation DESIGN OF A COMPACT TRIPLE-BAND FRACTAL PLANAR INVERTED F ANTENNAFOR HANDHELD APPLICATION Duong Thi Thanh Tu1,2*, Nguyen Ngoc Tu1, Vu Van Yem2 Abstract:In this paper, a novel Fractal PIFA antenna for triple-band is presented The proposed antenna is based on the self affinity and lengthen shorting pin of PIFA structure The combining design of the F-PIFA antenna is optimized and validated via simulation using CST-MW Studio as well as measurement The measured result is well in agreement tothe simulated result Being on the FR4 substrate with the height of 1.6mm, the antenna getsa compact size with patch dimension of 9.36x9.68mm2that is quite suitable for handheld terminals.The proposed F-PIFA antenna operates at 2.6GHz, 5.0GHz and 7.3GHz with large bandwidth of 10.55%, 25% and 5% respectively All leads to the meet for mobilebroadband services: LTE, Wi-Fi and X-band of Satellite on each handle mobile equipment Keywords:PIFA,F-PIFA, Fractal, Triple band INTRODUCTION Recently, the wireless communication system has advanced incredibly, especially in mobile phone system The dimensions of end used equipment is not only more and more decrease but also the number of internal antennas in one terminal increase rapidly [1-2] These require that internal antennas must be compacted to used practical mobile handsets and have multiband for multi technologies In last three decades, Planar Inverted F Antenna (PIFA) has emerged as one of the most promising candidate for satisfying above demands [3-4] However, one of the limitations of PIFA antenna is narrow bandwidth which makes this antenna type unsuitable for wide-band commercial applications To make multiband PIFA antenna, there are several methods that have been proposed However, using Fractal structure for making multiband in antenna design has attracted rather studies [5-9] just because this technique not only gets the multiband behaviour but also has small size and large bandwidth Recently, there have been a number of studies that combine Fractal and PIFA structure [10-12] Because the resonant frequency of PIFA antenna is inversely proportional to the antenna height, most of previous F-PIFA designs are based traditional PIFA structure which has the antenna height are higher than thickness of substrate This is why the PIFA antenna is fabricated much more complex than other patch antennas Here, we propose a novel antenna design which combines fractal configuration and innovated PIFA structure with lengthen shorting pin on the ground plane By this way, our F-PIFA antenna’s height is as equal as the substrate thickness Therefore, the hybrid Fractal PIFA antenna is not only easy to fabricate but also can operatein three bands with large bandwidth, which is suitable for wide-band commercial applications ANTENNA DESIGN Figure shows arecursive procedure of forming fractal for making multiband.Firstly, the circumscribed radius of a hexagonal shape, a, is calculated for lower resonant frequency of 2.6 GHz by the following equations [13]: F a= 1+ 40 ln + 1.7726 / (1) D.T.T.Tu, N.N.Tu,V.V.Yem, “Design of compact triple-band fractal planar…” Research F= 8.791x10 f √ε (2) Where:r is the dielectric constant, fr is the resonant frequency and h is the height of the substrate Figure Recursive procedure of forming fractal For giving freedom to cut fractal on the antenna surface, a microstrip line feeding is used The feed line is matched with the antenna through a quarter wave transformer and a characteristic impedance of 50 is obtained by the following equations [13]: Z = ε = 120π ε x + 1.393 + ln (3) + 1.444 ε +1 ε −1 h + + 12 2 W (4) Where:eff is the effective dielectric constant and W is the width of the feeding line After that, we cut the initial shape by the hexagonal shape on the boundary and the round shape at the center to make the 1st iteration fractal Then the 2nd and 3rd one are created with a self similar The purpose of applying fractal geometry to the patch antenna is to have multiband behavior as well as enlarge bandwidth (a) Top view (b) Bottom view Figure The structure of the proposed Fractal PIFA antenna Finally, to miniaturize the size of the antenna, fractal geometry is applied on a FIPA structure The resonance frequency of a typical rectangular PIFA antenna is approximated by Equation (5) [14] which is related to the electrical lengths is the relative permeability of the medium in between the ground and the radiating patch Also, H is the height of the Journal of Military Science and Technology, Special Issue, No.48A, - 2017 41 Electronics and Automation patch in reference to the ground, L and W are the patch length and the patch width, respectively f= c 4(H + L + W)√ε (5) In our antenna design, the shorting pin is lengthened on the ground to rise the distance of H to get the much compact size of PIFA antenna while the height of PIFA is 1.6mm which is the height of substrate This is a significant result in reducing thickness of equipment as well as complexity of antenna fabrication.The design of hybrid Fractal PIFA (FPIFA) antenna is optimized by CST software and illustrated in Figure with the detail dimensions of the proposed antenna shown on Table Table Detail dimension of proposed FPIFA antenna Parameter Value (mm) Parameter Value (mm) Parameter Value (mm) d L4 14.3 Wg 28.4 Lg 33.6 Lp 9.36 W1 0.5 L1 15.2 p 1.2 W2 L2 r1 0.64 Wp 9.68 L3 10.7 r2 1.6 Based on the FR4 substrate of 1.6mm thickness with relative permittivity of 4.4 and loss tangent of 0.02, the total size of proposed FPIFA is 33.6 x 28.4 mm2 and the patch size is 9.36 x 9.68 mm2 that is equivalent 10% theoreticalantenna’s size and more compact than previous studies SIMULATION RESULTS Performance of the proposed FPIFA antenna has simulated in CST software S parameter with different steps of antenna procedure is shown in Figure From Fig 3(a) and (b), it is clearly seen that using fractal geometry, the antenna not only gets multiband but also decreases resonant frequency from 8.2GHz down to 7.3GHz This means the antenna size is more compact if operates at same resonant frequency Appling this fractal on lengthened shorting pin PIFA structure which still uses the microstrip line feeding, significant reduction of resonant frequency is achieved The lower band of FPIFA has decreased from 7.3 GHz down to 2.6 GHz as shown in Fig 3(c) Hence the F-PIFA antenna size is reduced by 64% comparing to the 3rd iteration fractal geometry and gets much compact patch size of 9.36 x 9.68 mm2 while ensures the total height of PIFA antenna of 1.6mm (a) Initial hexagonal shape 42 D.T.T.Tu, N.N.Tu,V.V.Yem, “Design of compact triple-band fractal planar…” Research (b) 3rd iteration fractal geometry (c) Hybrid Fractal PIFA antenna Figure S parameters of progressive Fractal PIFA antenna It can be illustrated more clearly by analyzing the current distribution as shown in Figure Electric current goes from the microstrip line feeding to distribute on the patch as well as on the lengthened shorting pin Thus the electrical length of antenna is increased This means that the antenna size is reducedwithout frequency variation Fig Surface current distribution on antenna at resonant frequency Besides, from the Fig 4(c), it can be seen that the proposed antenna gets three bands which are 2.6 GHz, 5.0GHz and 7.3 GHz with large bandwidth of 274 MHz (10.55%), 1251 MHz (25%) and 369 MHz (5%), the reflection coefficient of -25dB, -32dB and 13dB respectively This result not only has solved the narrow bandwidth character which is the huge challenge of PIFA antenna but also quite be good for compact handheld equipment with LTE Wi-Fi and X band satellite applications The 2D and 3D radiation pattern for the three bands of proposed antenna are illustrated by Figure It can be seen that all 2D radiation pattern have dipolar and smooth radiation In addition, low radiation efficiency is one of drawbacks of patch antenna, especially using fractal geometry It is Journal of Military Science and Technology, Special Issue, No.48A, - 2017 43 Electronics and Automation reason why this parameter has not presented in almost previous fractal researches In our FPIFA design, as shown in 3D radiation, the radiation efficiency of antenna gets high value of 88% at 2.6 GHz This parameter gradually decreases but is rather high value of 80% at GHz and acceptable one of 64% at 7.3 GHz Thus, from the simulation results, it can be concluded that the proposed FPIFA has solved both challenges of Fractal geometry and PIFA structure in antenna design which are low radiation efficiency and narrow bandwidth for wideband commercial applications Tot effic.: - 0.58 (a) At 2.6 GHz resonant frequency Tot effic.: - 0.99 (b) At GHz resonant frequency Tot effic.: -2.24 (c) At 7.3 GHz resonant frequency Figure 5.The 2D, 3D radiation patterns of final designed antenna In addition, Table shows comparison between our proposed antenna and previous fractal designs It is clearly seen that the novel FPIFA antenna gets compact size than previous research while ensuring the large bandwidth for modern wireless 44 D.T.T.Tu, N.N.Tu,V.V.Yem, “Design of compact triple-band fractal planar…” Research communications.Going into detail, the considerably comparison in [6], our antenna design is equivalent 4% patch size while the bandwidth makes twice The remarkable reduction of antenna size is decreased by 23.64% and 28.76% in [8] and [10] respectively but the bandwidth of our design still makes twice and even more in [10] Comparison with [7], the bandwidth of our FPIPA is smaller slightly, however, the patch size is still much more compact that is equivalent nearly 27% Finally, comparison with [9], the patch size of our FPIPA is smaller slightly and the bandwidth of our FPIPA is larger little but the results of [9] are not much significant as lack of measurement results Table Comparison between present design and previous fractal geometry Freq (GHz) Patch size Max bandwidth (%) Ref [6] 2.6 0.416 x 0.416 12.3% Ref [7] 2.65 0.199 x 0.131 31.3% Ref [8] 2.5 0.215 x 0.316 8.1% Ref [9] 1.2364 0.061 x 0.114 22.89% Ref [10] 2.4 0.168 x 0.12 12.5% Our design 2.6 0.081 x 0.083 24.5% MEASUREMENT RESULTS The proposed F-PIFA antenna is fabricated on an FR4 substrate with the dielectric constant, r =4.4 and the thickness of 1.6mm.As shown in Fig.6 (a) and (b), the proposed antenna gets compact of total size is 28.4 x 33.6 x 1.6 mm3 With the height of antenna being the same of the height of substrate and the shorting pin be placed inner antenna structure, the proposed FPIFA is easy to fabricate comparing conventional PIFA antennas (a) top view (b) bottom view (c) Comparison between measured result and simulated one Figure6 Fabricated proposed Fractal PIFA antenna Moreover, using the microstrip line feeding, the measured result agrees well with the simulated one as shown in Figure 6(c) It is clearly seen that the FPIFA antenna operates at Journal of Military Science and Technology, Special Issue, No.48A, - 2017 45 Electronics and Automation 2.6GHz, 5GHz and 7.3GHz with the bandwidth approximating 10.6%, 20% and 5%, the reflection coefficient of -23dB, -22dB and -13dB, respectively CONCLUSION In this paper, the novel hybrid antenna design based on innovated PIFA structure and fractal geometry is proposed The FPIFA antenna operates at three bands which are 2.6GHz, GHz and 7.3GHz for LTE, Wi-Fi and X-band Satellite applications Thanks to fractal design as well as lengthened shorting pin of PIFA structure, the proposed FPIFA gets wide band of 10.6%, 24.5% and 5% and good radiation efficiency of 88%, 80% and 64% at 2.6GHz, GHz and 7.3GHz respectively Thus, the proposed FPIFA has solved both challenges of Fractal geometry and PIFA structure in antenna design which are low radiation efficiency and narrow bandwidth for wideband commercial applications In addition, the total size of FPIFA is 28.4x33.6x1.6mm3 which is much more compact than previous Fractal antennas REFERENCES [1] Rowell, C., Lam, E.Y., “Mobile phone antenna design,” IEEE Antennas and Propagation Magazine, vol 54, no 4, pp 14-34, 2012 [2] Hang Wong, Kwai-Man Luk, Chi Hou Chan, Quan Xue, Kwok Kan So, Hau Wah Lai, “Small antennas in Wireless Communications,” Proceedings of the IEEE, vol 100, issue 7, pp 2109-2121, July 2012 [3] Jhimlee Adhikari Ray, S R Bhadra Chaudhuri, “A review of PIFA technology,” IEEE Antenna Week (IAW), pp.1-4, Dec 2011 [4] N Kumar and G Saini, “A Multiband PIFA with Slotted Ground Plane for Personal Communication Handheld Devices,” International Journal of Engineering Research and Development, vol.7, no.11, pp.70-74, 2013 [5] T.Benyetho, L.El Abdellaoui, J Terhzaz et al., “Design of a Novel Fractal Multiband Planar Antenna with a CPW-Feed,”International Journal of Electrical, Computer, Energetic, Electronic and Communication Engineering, vol.9, no.1, pp.12-15, 2015 [6] Deepa Dubey, Jagdeesh Ahirwar, Deepak Dekate and Zohaib Hasan, “Circular Sierpinski Fractal Antenna for Multiband Wireless,” 2015 International Conference on Computational Intelligence and Communication Networks, IEEE publisher, 2015 [7] Yadwinder Kumar, Surinder Singh, “A Quad-Band Hybrid Fractal Antenna for Wireless Applications,” 2015 IEEE International Advance Computing Conference (IACC), pp.730-733, 2015 [8] Livya Shree G., Maheswari T et al., “A Compact Fractal Antenna based on Sierpinski Geometry for “S” band Applications,” International Journal of Innovative Research and Development, vol.4, issue.3, pp.244-249 [9] Yadwinder Kumar et al, “A Compact Multiband Hybrid Fractal Antenna for Multi standard Mobile Wireless Applications,” Wireless Personal Communications, Springer journal, vol.84, Issue 1, pp 57–6, September 2015 [10].Ali J Salim, Raad S Fyath et al., “A New Fractal Based PIFA Antenna Design for MIMO Dual Band WLAN Applications,” Progress in Electromagnetics research Symposium Proceedings (PIER), pp.1526-1530, 2012 46 D.T.T.Tu, N.N.Tu,V.V.Yem, “Design of compact triple-band fractal planar…” Research [11].N A Saidatul et al., “Multiband Fractal Planar Inverted F Antenna (F-PIFA) for Mobile Phone Application,” Progress IN Electromagnetics Research B, vol.14, pp.127-148, 2008 [12].Y Belhadef and N.Boukli Hacene, “Multiband F-PIFA Fractal Antennas for Mobile Communication Systems,” International Journal of Computer Science Issues (IJCSI), 2012 [13].Balanis C.A, “Antenna Theory: Analysis and Design,” Edition 3rd, Wiley, 2005 [14].Nariman Firoozy, Mahmoud Shirazi, “Planar Inverted-F Antenna (PIFA) Design Dissection for Cellular Communication Application,” Journal of Electromagnetic Analysis and Applications, No 3, pp 406-411, 2011 TÓM TẮT THIẾT KẾ ANTEN BA BĂNG TẦN CHO CÁC ỨNG DỤNG CẦM TAY DI ĐỘNG DỰA TRÊN CẤU TRÚC PIFA VÀ HÌNH HỌC FRACTAL Nội dung báo đề xuất mẫu anten PIFA kết hợp kiến trúc Fractal (anten FPIFA) cho ứng dụng đa băng thiết bị đầu cuối di động Anten đề xuất sử dụng đặc tính tự đồng dạng hình học Fractal kết hợp với cấu trúc PIFA cải tiến chiều dài shorting pin mặt phẳng đất Toàn cấu trúc hình học Fractal kiến trúc PIFA anten tối ưu phần mềm CST-MW Chế tạo vật liệu FR4, anten đề xuất cho kết thực nghiệm mô tương đồng Với chiều cao 1.6mm, anten FPIFA có kích thước vơ nhỏ gọn so với thiết kế Fractal trước với bề mặt xạ anten đạt 9.36 x 9.68mm2, hoàn toàn phù hợp cho thiết bị cầm tay di động Cộng hưởng ba tần số 2.6GHz, 5GHz 7.3GHz, anten đề xuất đạt băng thông siêu rộng 10.55%, 25%, 5%, đồng thời ứng dụng cho ba công nghệ băng rộng phổ biến LTE, WIFI vệ tinh băng X Từ khóa: PIFA, F-PIFA, Fractal, Ba băng tần Received date, 18th November 2016 Revised manuscript, 14th January 2017 Published on 26th April 2017 Author affiliations: Posts and Telecommunications Institute of Technology; Hanoi University of Science and Technology; *Corresponding author:tudtt@ptit.edu.vn Journal of Military Science and Technology, Special Issue, No.48A, - 2017 47 ... N.N.Tu,V.V.Yem, Design of compact triple- band fractal planar ” Research (b) 3rd iteration fractal geometry (c) Hybrid Fractal PIFA antenna Figure S parameters of progressive Fractal PIFA antenna It can be... N.N.Tu,V.V.Yem, Design of compact triple- band fractal planar ” Research [11].N A Saidatul et al., “Multiband Fractal Planar Inverted F Antenna (F- PIFA) for Mobile Phone Application, ” Progress IN Electromagnetics... proposed FPIFA has solved both challenges of Fractal geometry and PIFA structure in antenna design which are low radiation efficiency and narrow bandwidth for wideband commercial applications In addition,