Series feed fan - beam antenna array with a low sidelobe level for positioning system

teristic 
impedance Z1 and length λ/4. It is desired to match the load to the Z0 line using the 
λ/4 line. From [13], the input impedance 𝑖𝑛 can be found as equation (3): 
Electronics & Automation 
N. T. K. Ngan, , L. M. Thuy, “Series feed fan-beam antenna  positioning system.” 58 
 𝑖𝑛 = 1 (
𝑅𝐿 + 𝑗 1 tan𝛽𝑙
 1 + 𝑗𝑅𝐿 tan𝛽𝑙
) 
(3) 
If l = 𝜆 4 then 𝛽𝑙 = 𝜋 𝜆 𝜆 4 = 𝜋 , which leads to: 
 𝑖𝑛 =
 1 
2
𝑅𝐿
(4) 
Let ᴦ reachs the minimum value, then 𝑖𝑛 = 0 and : 
 1 = √ 0 𝐿 (5) 
So a quarter-wave-matched-T Junction with Z0 = 50 ohm input impedance and 
two equal output ports of Z0 = 50 ohm, the impedance of the quarter-wave-
transformer is determined by equation (7): 
 1 = 0 √ (7) 
2.2. Feeding Network Design 
In this paper, the Chebyshev distribution is applied to calculate the output 
power amplitude for each element in the array [2]. The 1-10 feeding network 
consists of a main line fed by the 50 Ω line at the center, unequal T-junctions to 
control the output power amplitude excited at each the element and quarter-wave–
transformers to be matched with antenna element impedance. The Chebyshev 
output power amplitudes for 10 antenna elements are calculated and listed in the 
table 1. The feeding model at one side is shown in figure 3. 
 Figure 3. Feeding network model at one side with unequal T-junctions. 
The impedances of the unequal T-junctions (Z1, Z2,... Z10) and the impedances 
of the quater-wave transformers at figure 3 are determized by Z5/Z0 = u5/u0 = 1, 
Z4/Z0 = u4/u0 = 0.931, Z3/Z0= u3/u0 = 0.8024 , Z2/Z0 = u2/u0 = 0.6311, Z1/Z0 = u1/u0 
= 0.4392. After caculating the impedances of the unequal T-junctions, the 
impedances of quater-wave T-junctions (T1,T2...T10, Tz1,Tz2,...Tz10) are also 
determined and are shown in table 2 and table 3, respectively: 
Table 1. Chebyshev amplitude distribution for 10 antenna elements (SLL = -20dB). 
Element Amplitude (V) Amplitude (dB) 
u1 & u10 0.4392 -7.9424 
u2 & u9 0.6311 -5.6570 
u3 & u8 0.8024 -3.8873 
u4 & u7 0.9310 -2.5171 
u5 & u6 1 0 
u0
u5 u4 u3 u2 u1
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Journal of Military Science and Technology, Special Issue, No.66A, 5 - 2020 59 
Table 2. Impedance and dimension of T-Junctions. 
Feed element Amplitude (V) Impedance (Ω) Value of width (mm) 
Z1 & Z10 0.4392 113.84 0.28 
Z2 & Z9 0.6311 79.227 0.75 
Z3 & Z8 0.8024 62.313 1.2 
Z4 & Z7 0.9311 53.706 1.58 
Z5 & Z6 1 50 1.75 
Table 3. Dimension of the quarter-wave –transformers. 
Transformer Value of width 
(mm) 
Transformer Value of width 
(mm) 
T1 2.98 Tz1 1.75 
T2 2.924 Tz2 1.68 
T3 2.77 Tz3 1.48 
T4 2.58 Tz4 1.19 
T5 0.8343 Tz5 0.8343 
The simulated reflection coefficient S11 of the proposed feeding network is 
illustrated in figure 4 (a), showing that the feeding network works well in a wide 
range from 4 GHz to 6 GHz and having a good impedance matching. The excited 
phases at then antenna elements are nearly the same as shown in figure 3 (b) and 
table 4. The excited ampllitude of antenna elements u1&u10, u2&u9, u3&u8, u4&u7, 
u5&u6 are from 0.4392 to 1 accordign to the Chebyshev distribution . The power at 
the element 1 and 10 are smaller than the power at element 5 and 6 up to 50%. It is 
clear that the simulated amplitude coeficients in figure 4 (a) meet well with the 
desired Chebyshev distribution with a small negligible difference, but the signal is 
greatly attenuated due to the use of T-Junctions and quater-wave transformer. 
There may be fringing fields and higher order modes associated with the 
discontinuity at such a junction, which leads to the attenuated energy. 
a) b) 
 Figure 4. (a)Reflection coefficient of the feeding network 
(b) Phases of elements in the feeding network. 
Electronics & Automation 
N. T. K. Ngan, , L. M. Thuy, “Series feed fan-beam antenna  positioning system.” 60 
3. THE PROPOSED ARRAY ANTENNA 
3.1. Printed Yagi Antenna Element 
 The printed Yagi antenna originated from the Yagi-Uda antenna by Huang in 
1991 [14] is chosen in this paper. Its structure consists of a folded half-wavelength 
dipole and an approximately quater-wavelength rectangular director to improve the 
gain and the front-to-back ratio. Besides, it is low profile, low-cost and has light 
weight, small size. These advantages make it suitable to be integrated into circuits 
as well as to be easily fabricated. Many contributions have been done in the design 
and optimization of the printed Yagi-antenna for specific applications [15-17]. In 
[13], the Invasive Weed Optimization (IWO) method is applied to design and 
optimize a printed Yagi antenna, the optimization goals are set to reach an antenna 
with a VSWR less than 1.5 and high gain radiation pattern. PSO (Particle swarm 
optimization) has been used to optimize gain, impedance and bandwidth of Yagi–
Uda array in [16]. In our proposal, two directors are used to increase the 
directivity. Moreover, the Yagi antenna element is miniaturized by bending its 
arms as shown in figure 5 (a). 
 a) 
 b) 
 Figure 5. The proposed Yagi antenna (a) Top layer 
(b) Bottom layer (Lg = 12, yg = 3.5; Lc = 5, L = 16.8, hy = 7, Ly = 15, w = 2.1, g = 
0.7, h1 = 7, yf = 10, Xs = 30, Ys = 37). 
Two element directors are added above the arms of the Yagi antenna element. 
The distance between two directors and their length are optimized based on PSO 
algorithm in [16]. The distances hy between directors should be 0.1λ and 0.45λ, and 
the length Ly of each element varies between 0.15λ and 0.35λ to increase the gain 
while the input impedance of the antenna and banwidth maintain good. The J-
shaped balun in figure 5 (b) based on Robert's research [18] is applied to overcome 
weak impedance matching of the I-shaped balun. The Yagi antenna element works 
by coupling from the J-shaped balun to its two arms. The proposed Yagi antenna 
element is printed on a Rogers 4003C substrate with the relative permittivity of 
3.55 and the thickness of 0.8 mm. The total size of each element antenna is 
30×37×0.8 mm3. The reflection coefficient S11 is -37 dB at 5 GHz as shown in 
figure 6 (a). The peak gain of 7.6 dBi is obtained as shown in figure 6 (b) while the 
Research 
Journal of Military Science and Technology, Special Issue, No.66A, 5 - 2020 61 
radiation efficiency is very high up to 96.2 %. The antenna gain of an array can be 
increased if the element antenna gain is increased. This Yagi antenna gain can be 
increased up to 9.5 dBi by just adding more the directors while the beamwidth is 
smaller and the antenna size in y direction will be increared. The suitable 
beamwidth and peak gain must be determined according to the antenna array 
application requirement. 
 (a) (b) 
 Figure 6. The Yagi antenna element: (a) Reflection coefficient (b) 3D pattern. 
3.2. The proposed array antenna 
(a) Top layer 
(b) Bottom layer 
 Figure 7. The proposed array antenna model. 
Electronics & Automation 
N. T. K. Ngan, , L. M. Thuy, “Series feed fan-beam antenna  positioning system.” 62 
The array structure is created by combining 10 single elements and 1-10 series 
feed network designed in the previous sections as shown in figure 7. The distance 
between the elements in the antenna array is λ, and the overall size of 
450×57×0.8 mm3. 
Table 4. Phase and amplitude excitation of the proposed array. 
Element Phase (degree) Amplitude (dB) 
u1 & u10 126 -16 
u2 & u9 125.5 -14 
u3 & u8 126 -13 
u4 & u7 130 -9 
u5 & u6 135 -6 
The simulated reflection coefficient of the proposed array antenna is shown in 
figure 8, where the wide bandwidth of 27.7 % can be seen. From the results in 
figure 9, the fan beam, high gain of 14.5 dBi and the low sidelobe levels of -18 dB 
are obtained. Moreover, the radiation efficiency is high up to 90% at 5GHz. Thus, 
the proposed antenna is suitable for outdoor positioning application systems. 
The results in this work have been compared with the related works from the 
literatures as shown in table 5. The proposed antenna is more compact than the 
antenna in [3] and [11]. However, the gain is a little lower but the peak gain of 
array can be enhanced up to 4 dB using the reflector as the work in [3] and [11] 
mentioned and it will be higher than the work in [3] and [11] in the case using 
reflector. Besides, the radiation pattern of array antenan can be changed by adding 
directors in the dipole-yagi element according to the antenna element design. 
However, for positioning system, the wide angle in horizontal from 1200 to 1500 is 
required so that the proposed antenna is determined with two directors in antenna 
element. 
 Figure 8. Reflection coefficient of the array antenna. 
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Journal of Military Science and Technology, Special Issue, No.66A, 5 - 2020 63 
a) 
b) 
Figure 9. The simulation of array antenna (a) 2D radiation pattern (b) 3D 
radiation pattern. 
Table 5. Comparison between the proposed antenna array and related works. 
References [3] [6] [5] [11] This work 
Element No 10×1 10×1 10×1 10× 10×1 
Size (mm3) 422×100×10.15 - - 420x100x10.4 450×57×0.8 
Frequency 
(GHz) 
5.5 9 60 5.5 5 
Gain (dBi) 17.5 14.5 15.7 
14.2 (without 
reflector) 
17.5 (with reflector) 
14.5 
Results of 
SLL (dB) 
-26 -25.3 -27.7 -26 -18 
Preset of SLL -30 - -30 -30 -20 
4. CONCLUSION 
In this paper, a novel high gain and low sidelobe level linear microstrip antenna 
array for positining outdoor system application have been proposed. The design 
procedure from the single element to the complete array antenna has been 
presented in details. In order to get the low SLL, the Chebyshev distribution has 
been used in the feeding network of the array antenna. The Chebyshev excitation 
coefficients have been obtained in the feed using unequal T-junctions and quater-
wave transformers to get good impedance matching. The simulated results proved 
that the array can operate at 5 GHz with the high gain of 14.5 dBi and the low SLL 
of -18 dB. 
ACKNOWLEDGEMENT 
This research is funded by the Hanoi University of Science and Technology 
(HUST) under project number T2018-TĐ-006. 
Electronics & Automation 
N. T. K. Ngan, , L. M. Thuy, “Series feed fan-beam antenna  positioning system.” 64 
REFERENCES 
[1]. D. Ehyaie, “Novel Approaches to the Design of Phased Array Antennas,” Jan. 2011. 
[2]. C. A. Balanis, Antenna theory: analysis and design, Chapter 7, 3rd ed. Hoboken, NJ: 
John Wiley, 2005. 
[3]. T. Toan, T. Nguyen, and T. Giang, A low sidelobe fan-beam series fed linear 
antenna array for IEEE 802.11ac outdoor applications. 2017 International 
Conference on Advanced Technologies for Communications (ATC), pp. 161-165. 
[4]. D. M. Pozar and B. Kaufman, “Design considerations for low sidelobe microstrip 
arrays,” IEEE Trans. Antennas Propag., vol. 38, no. 8, pp. 1176–1185, Aug. 1990. 
[5]. Wenhui Shen, Jiahong Lin, and Kang Yang, “Design of a V-band low sidelobe and 
wideband linear DRA array,” 2016, pp. 477–480. 
[6]. J. Yin, Q. Wu, C. Yu, H. Wang, and W. Hong, “Low-Sidelobe-Level Series-Fed 
Microstrip Antenna Array of Unequal Interelement Spacing,” IEEE Antennas Wirel. 
Propag. Lett., vol. 16, pp. 1695–1698, 2017. 
[7]. M. Dürr, A. Trastoy, and F. Ares, “Multiple-pattern linear antenna arrays with 
single prefixed amplitude distributions: modified Woodward-Lawson synthesis,” 
Electron. Lett., vol. 36, no. 16, p. 1345, 2000. 
[8]. M. F. A. Ahmed, O. M. Haraz, G. Kaddoum, S. A. Alshebili, and A.-R. Sebak, “On 
using Gaussian excitation amplitudes to improve the antenna array radiation 
characteristics,” 2014 IEEE Asia-Pacific Conference on Applied Electromagnetics 
(APACE), pp. 131–134. 
[9]. J. Lin, W. Shen, and K. Yang, “A Low-Sidelobe and Wideband Series-Fed Linear 
Dielectric Resonator Antenna Array,” IEEE Antennas Wirel. Propag. Lett., vol. 16, 
pp. 513–516, 2017. 
[10]. P. Borah and S. Bhattacharyya, "Design of a fan beam 1×4 array antenna using V-
shaped patch element for its use in X-band communication," URSI AP-RASC 2019, 
New Delhi, India, 09 - 15 March 2019. 
[11]. Tang The Toan, Nguyen Minh Tran and Truong Vu Bang Giang, "A Novel 
Chebyshev Series Fed Linear Array with High Gain and Low Sidelobe Level for 
WLAN Outdoor Systems," REV Journal on Electronics and Communications, Vol. 8, 
No. 1–2, January–June, 2018. 
[12]. Sun-Woong Kim and Dong-You Choi, "Analysis of Beamforming Antenna for 
Practical Indoor Location-Tracking Application," Journal of Sensors, 
doi:10.3390/s19143040, 2019 
[13]. D. M. Pozar, "Microwave engineering," Chapter 7, 4th ed. Hoboken, NJ: 
Wiley, 2012 
 [14]. J. Huang and A. C. Densmore, “Microstrip Yagi array antenna for mobile satellite 
vehicle application,” IEEE Trans. Antennas Propag., vol. 39, no. 7, pp. 1024–1030, 
Jul. 1991. 
[15]. S. H. Sedighy, A. R. Mallahzadeh, M. Soleimani, and J. Rashed-Mohassel, 
“Optimization of Printed Yagi Antenna Using Invasive Weed Optimization (IWO),” 
IEEE Antennas Wirel. Propag. Lett., vol. 9, pp. 1275–1278, 2010. 
[16]. M. Rattan, M. S. Patterh, and B. S. Sohi, “Optimization of Gain, Impedance, and 
Bandwidth of Yagi-Uda Array Using Particle Swarm Optimization,” Int. J. Antennas 
Propag., vol. 2008, pp. 1–4, 2008. 
Research 
Journal of Military Science and Technology, Special Issue, No.66A, 5 - 2020 65 
[17]. J.-M. Floc H and A. El Sayed Ahmad, “Dual-Band Printed Dipole Antenna with 
Parasitic Element for Compensation of Frequency Space Attenuation,” Int. J. 
Electromagn. Appl., vol. 2, no. 5, pp. 120–128, Dec. 2012. 
[18]. Trong Thuy Pham, Le Minh Thuy, Tran Truong Phan, Pham Xuan Lap, Ngo Hoang 
Anh, “Novel Dual-Polarized 5G Base Station Antenna”, 2017 IEEE Asia Pacific 
Microwave Conference (APMC), pp 474-478, (2019). 
TÓM TẮT 
ĂNG TEN MẢNG TUYẾN TÍNH TIẾP ĐIỆN NỐI TIẾP BÚP SÓNG DẢI 
QUẠT VỚI MỨC BÚP PHỤ THẤP CHO HỆ THỐNG ĐỊNH VỊ 
Bài báo này đề xuất một mảng ăng ten mới hoạt động ở dải tần 5 GHz với búp 
sóng phụ thấp phù hợp cho các ứng dụng định vị ngoài trời. Mảng ăng ten có kích 
thước nhỏ gọn 450 ×57×0.8 mm3 gồm 10 phần tử, độ tăng ích 14.5 dBi và độ nén 
búp phụ thấp -18 dB tại tần số 5 GHz. Ẳng-ten sử dụng mạng tiếp điện 1-10 kiểu nối 
tiếp, phân bố biên độ ở các đầu ra tuân theo luật phân phối Chebyshev để đạt độ 
nén búp sóng phụ thấp. Các ăng ten chấn tử Yagi kiểu mạch in được sử dụng để 
tăng tính định hướng cho ăng ten mảng. Ngoài ra, độ tăng ích của ăng ten phần tử 
có thể được tăng bằng việc ghép thêm phần tử dẫn sóng định hướng phía trên các 
ăng-ten chấn tử. 
Từ khóa: Mảng ăng-ten vi dải; Độ nén búp sóng phụ thấp; Đa thức Chebyshev; Ăng-ten Yagi vi dải. 
Received 20th February, 2020 
Revised 11th April, 2020 
Published 06th May, 2020 
Author affiliations: 
1 Hanoi University of Science and Technology; 
2 Electric Power University; 
3 University of Transport and Communications. 
*Corresponding author: thuy.lm@hust.edu.vn.