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Design of Microstrip Antenna for LTE (Long Term Evolution) 700 MHz Applications

Dony Sugianto Fakultas Pendidikan Teknologi dan Kejuruan

Universitas Pendidikan Indonesia Bandung, Indonesia

dony.sugianto@yahoo.com

Tommi Hariyadi Fakultas Pendidikan Teknologi dan Kejuruan

Universitas Pendidikan Indonesia Bandung, Indonesia

tommi@ieee.org

Abstract – This paper discusses the design of microstrip antenna which is used in cellular communication application especially at LTE 700 MHz network. The antenna was printed using FR-4 substrate material with dielectric constant of r = 4.65 and thickness of h = 1.6 mm. The overall dimension of the antenna is 135 mm x 32 mm x 1.6 mm with 50 Ω impedance. This antenna operates between 697.6 MHz and 784.9 MHz for return loss of less than -10 dB. The simulation results suggest that the antenna gain ranges between 1.5 dBi and 2 dBi with omnidirectional radiation pattern.

Keywords—microstrip antenna, LTE, omnidirectional

I. INTRODUCTION The evolution of wireless technology has grown

dramatically. In the future, it is estimated that the need to access the internet will increase along with ever increasing human mobility. The presence of service for higher data rate will be the solution to answer the needs. In order to overcome this issue, LTE (Long Term Evolution) technology was launched. LTE will be the step towards the fourth generation (4G) originated from radio technology which is designed to improve network capacity and speed [1]. LTE provides downlink capacity of at least100 Mbps and uplink capacity of at least 50 Mbps.

In the wireless communication system, the role of antenna is very crucial. Wireless technology application requires a small, light weighted, cheap and easy to install antenna, without compromising its performance [2]. Microstrip antenna meets several requirements above. The special quality of microstrip antenna is its low profile and easy in realization. The proposed antenna dimension designed in this paper is 135 mm x 32 mm x 1.6 mm. The designed antenna follows the antenna design [3] with different shape of the patch. Besides, the antenna’s ground plane is narrowed down for better return loss value. Antenna [3] has the dimension of 242 mm x 35 mm x 1.65 mm which is larger than the antenna designed in this paper. In addition, the designed antenna has operating frequency between 697.6 MHz and 784.9 MHz for VSWR less than 2 with wide bandwith of 87.3 MHz. The purpose of antenna design is to improve the efficiency of LTE network.

II. ANTENNA DESIGN The microstrip antenna designed in this paper is a

rectangular microstrip patch antenna that utilizes microstrip line feed connected with SMA connector [4]. The designed antenna has 50 Ω impedance and created using FR-4 substrate with dielectric constant of 4.65 and thickness of 1.6 mm. The overall dimension is 135 mm x 32 mm x 1.6mm. The antenna is designed with the help of software with Finite Integration Technique (FIT) method.

W8

(a) (b) Figure 1. Antenna Design (a) top view and

(b) bottom view

The configuration of designed antenna using the help of this software can be seen in Figure 1. Figure 1(a) and 1(b) shows the top and bottom view of the antenna, respectively. The size of antenna parameter is shown in Table 1.

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Table 1. Antenna parameter’s size

Parameter Size (mm) Parameter Size (mm)

Ws 32 W8 2

Wg 32 Ls 135

W1 27 Lg 48

W2 6.5 L1 69

W3 23 L2 61

W4 2 L3 53

W5 2 L4 2

W6 13,75 L5 43

W7 4,5

The fabrication of microstrip antenna was conducted based on the simulation results utilizing the above mentioned software. Antenna fabrication was very easy to do and inexpensive.

III. SIMULATION RESULTS The software that be used to simulate the antenna has the

ability to display several antenna parameters such as return loss, VSWR, impedance, gain and radiation pattern. This section illustrates several simulation results of the designed antenna.

A. Return loss and Bandwidth Figure 2 demonstrates the return loss (S-Parameter) value,

as a result of antenna simulation. The antenna operates between 697.6 MHz and 784.9 MHz. Bandwidth is obtained from the difference between the upper and the lower frequencies. Bandwidth obtained from the simulation was quite large, 87.3 MHz.

Figure 2. Return loss (S-Parameter) of simulation result

B. VSWR Figure 3 illustrates the VSWR simulation result value.

The VSWR value obtained from simulation at 697.6 MHz was 1.932. This VSWR value fulfills the criteria of less than 2.

Figure 3. VSWR at frequency 697.6 MHz

The designed antenna operates very well at frequency 738.1 MHz, with the value of VSWR is 1.084. Figure 4 shows the VSWR value at 738.1 MHz.

Figure 4. VSWR at frequency 738.1 MHz

At frequency 784.9 MHz, a decline in antenna’s quality performance was observed. This is due to high VSWR value of 1.889. However, this would not be an issue, as the VSWR value was still below the requirement of < 2. Figure 5 shows the VSWR value at 784.9 MHz.

Figure 5. VSWR at frequency 784.9 MHz

C. Gain The antenna has various gains at frequency range between

697.6 MHz and 784.9 MHz. At 697.6 MHz, the antenna gain was 1.535 dBi as shown in Figure 6. The antenna gain at 738.1 MHz was 2.093 dBi, which is demonstrated in Figure 7. At 784.9 MHz, the antenna gain was 1.745 dBi as depicted in Figure 8. From the results, it can be observed that at the

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operating frequency, the highest antenna gain occurs at 784.9 MHz where at this frequency, the VSWR antenna reaches the lowest value. In addition, the antenna gain at 738.1 MHz is greater than that of at other frequencies. This is because the efficiency at this frequency is greater than that of at other frequencies as seen in Figure 6, 8 and 10.

D. Radiation Pattern

The designed antenna has omnidirectional radiation pattern, as shown in Figure 6 to 11. This is one of the characteristics of a monopole antenna, which is similar to that of dipole antenna. Radiation pattern of E plane and H plane at 697.6 MHz can be seen in Figure 7.

Figure 6. Gain dan pola radiasi 3D pada frekuansi 697,6 MHz

(a) E plane (b) H plane

Figure 7. Radiation pattern of E plane and H plane at frequency 697.6 MHz

The 3D radiation pattern at 738.1 MHz is shown in Figure

8 while radiation pattern of E plane and H plane can be seen in Figure 9.

Figure 8. Gain dan pola radiasi 3D pada frekuansi 738,1 MHz

(a) E plane (b) H plane

Figure 9. Radiation pattern of E plane and H plane at frequency 738.1 MHz

The 3D radiation pattern at 784.9 MHz frequency can be

seen in Figure 10, while radiation pattern of E plane and H plane is depicted in Figure 11.

Figure 10. Gain dan pola radiasi 3D pada frekuansi 784,9 MHz

(a) E plane (b) H plane

Figure 11. Radiation pattern of E plane and H plane at frequency 784.9 MHz

Table 2 shows VSWR value and antenna gain simulation

results. The antenna operates very well at 738.1 MHz frequency and exerts larger gain of 2.1 dB, which is larger than that of other frequencies.

Table 2. Antenna simulation results of VSWR and gain Frequency (MHz) VSWR Gain (dB)

697.6 1,932 1,535 738,1 1,084 2,093 784,9 1,889 1,745

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IV. CONCLUSION From the design and simulation of microstrip antenna with

the help of software utilizing FIT method, it can be concluded that the antenna operating frequency ranges from 697.6 MHz to 784.9 MHz for less than -10 dB return loss or almost equivalent to VSWR less than 2. The antenna gain ranges between 1.5 dBi and 2.1 dBi. The highest gain occurs at 738.1 MHz where the VSWR value reaches 1.084. This antenna has omnidirectional radiation pattern, which is in line with monopole antenna characteristics. The antenna dimension is 135 mm x 32 mm x 1.6 mm. Due its 700 MHz operating frequency, this antenna can be implemented in LTE (Long Term Evolution) 700 MHz applications.

REFERENCES

[1] 3GPP TS 36.101, V8.3.0, “EUTRA User Equipment Radio Transmission and Reception,” September 2008.

[2] Garg, R., Bhartia, P., Bahl, I., Ittipiboon, A., Microstrip Antenna Design Handbook, Artech House, Inc, 2001.

[3] C.-Y. Huang, B.-M. Jeng and C.-F. Yang, “ Wideband monopole antenna for DVB-T applications,”IEEE Electronics Letter, vol. 44, 2008.

[4] W. C. Liu, M. Ghavami, and W. C. Chung, “Triple-frequency meandered monopole antenna with shorted parasitic strips for wireless application,” IET Microw., Antennas, Propag., vol. 3, pp. 1110–1117, 2009.

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