James J. (Jong Hyuk) Park et al. (eds.), Future Information Technology, Application, and Service, LNEE 179, pp. 325–330, DOI: 10.1007/978-94-007-5063-0_44, © Springer Science+Business Media Dordrecht 2012

A Study on Design of Microstrip Patch Antenna for Mobile Communication Systems

Jong-Dae Park, Sung-Won Jang, Byeong-Ho Park, Chan-Hong Park, Myung-Dong Kim, and Hyeon-Kyeong Seong

School of Computer, Information, and Communication Engineering, Sangji University, Woosan 660, Wonju, Kangwon 220-702, Korea

orient3690,bestpolarbear,eden200,pchnaya1,hkseong@sangji.ac.kr,

mdkim@utns.co.kr

Abstract. In this paper, a novel particle swarm optimization method based on IE3D is used to design a mobile communication Microstrip Patch Antenna. The aim of the thesis is to Design and fabricate an inset fed rectangular Microstrip Antenna and paper the effect of antenna dimensions Length (L), Width (W) and substrate parameters relative Dielectric constant ( r

ε ), substrate thickness on Radiation parameters of Band width. When the antenna was designed, a dual-band, dual-polarized antenna was used to secure the bandwidth and improve performance, and a coaxial probe feeding method so that the phased array of antenna is easy.

Keywords: Microstrip Patch Antenna, Mobile Communication Antenna, PSO, IE3D.

1 Introduction

The miniaturization of antenna has been actualized through the micro-strip antenna area so far, and currently exhibits visible achievements in various areas [1-3].

Antenna miniaturization method includes usage of dielectric substance, but this method deteriorates antenna characteristics such as antenna bandwidth and radiation efficiency, posing limits in miniaturization, and thus there are studies in progress for changing the antenna structure for miniaturization. Generally, decreasing the antenna size renders the antenna radiation pattern to be close to nondirectional, and the antenna benefit diminishes as well. Also, the antenna input resistance becomes very small and the reactance greatly increases to render the antenna bandwidth very narrow [4-6]. It is certainly not easy to develop a small-sized antenna while overcoming such issues. Matching impedance to maintain the characteristics while decreasing the size can be said to be the task of small-sized antennas.

2 Microstrip Patch Antenna for Mobile Communication

2.1 Simulation Environment

The resonance frequency for the design in this report is 2.4GHz, and the dielectric constant of the board (

rε ) is 2.45. As such, the board and high dielectric constant

326 J.-D. Park et al.

were selected to decrease the area of the antenna. The height of the dielectric board (h ) was set to 1.58mm as it is necessary to have a small antenna for micro patch antenna used in mobile phones.

Applying the above simulation environment, each value was found in seven stages as below, and the design incorporated the found values.

Stage 1: Width (w ) To calculate the width of the antenna while applying the resonance frequency (

0f ) of

2.4GHz and dielectric constant (r

ε ) of 2.45 given in the simulation environment

above, it follows equation (2) and results in value of 47.5mm.

( )12

2r

cW

fε

=+

(1)

Stage 2: Effective Dielectric Constant (reff

ε )

For effective dielectric constant (reff

ε ), while there is field for the wave at the edge

and line, it is not limited to dielectric board, so the value of the effective dielectric constant must be smaller than the constant of the dielectric board, and thus the effective dielectric constant is as in equation (3). In equation (3), the dielectric constant (

rε ) is 2.45, width of patch antenna is 47.5mm, and dielectric board height

( h ) is 1.58mm, and here, the effective dielectric constant (reff

ε ) is found to be

2.3368.

12

1 1 1 122 2r r

reff

h

W

ε εε−

+ − = + +

(2)

Stage 3: Patch Length Expansion ( LΔ ) When the conditions given above were applied, the calculation equation for patch length expansion ( LΔ ) can be expressed, and the patch length expansion ( LΔ ) calculation equation is as in equation (5).

( )

( )

0.3 0.2640.412

0.258 0.8

reff

reff

W

hL h

W

h

ε

ε

− + Δ = − +

(3)

Stage 4: Actual Length (L ) of Patch The actual patch length (L ) is calculated in equation (6), which resulted in 39mm.

2effL L L= − Δ (4)

Stage 5: GP Size The transmission cable model is basically applied to infinite GP, but practically when the transmission cable model is applied in small-sized antenna design, it is essential of have a finite GP. If GP has a surrounding board thickness of about six times the patch

A Study on Design of Microstrip Patch Antenna for Mobile Communication Systems 327

size, the finite GP and infinite GP can have about the same result value. Therefore, the GP value of antenna used in this report was set to be the GP size as in equation (7) and (8).

( )6 6 1.5 39 48gL th L mm= + = + = (5)

( )6 6 1.5 47.5 56.5gW th W mm= + = + = (6)

Stage 6: Determination of Inset Feed Depth (y0) In this report, inset-feed type of feed was used. The feed depth is given by y0, and feed point must be positioned at the patch position of resonant frequency where input impedance is 50Ω. In this case, PSO was used to obtain the best feed point where return loss (RL) is most negative, that is, minimal. The point exists according to the patch length with minimal return loss.

When,

( ) ( ) ( )*0 0 cos 4 0 /Rin y y Rin y y Lπ= = =

( ) ( )*0 0.5 1 12Rin y G G= = ±

00

0

00 0

60 84 1

113.93 0.667 1.444

eff

c

eff

Wh WW h hZ

WW Whh h

ε

ε

∈ +

≤ = ≥ + + ∈ +

2

00

1 2

00

1

90

1

120

WW

GW

W

λλ

λλ

=

( )

2

0

312 0 02 0

sin cos1 2

sin sin120 cos

k W

G J K L dπ

θθ θ θ

π θ

=

By using Rin (y=y0) = 50 Ω from the first equation, mmu 130

= was obtained.

2.2 Simulation Results

During antenna design, the insert feed used in IE3D shall be designed with insert material of depth 13.2mm, feed line width of 5.6m, and feed path length of 37mm, and frequency range of 2.2 ~ 3.5GHz. The central frequency was selected to have

328 J.-D. Park et al.

minimal return loss, and the bandwidth can be calculated from the return loss (RL) found here. As the result, the depth of the optimal feed using PSO was found to be -27dB. In this case, the antenna bandwidth is computed to be 23.28 MHz, and the central frequency of 1.9120 GHz is found, and as the result, the optimal feed depth is found to be 13.2mm. Also, since the impedance of each line applied to the patch is different, the length of W is controlled to control the coordination of the impedance and at the same time the antenna bandwidth could be adjusted. As the result of measuring reflection loss of the produced patch antenna, it was showing frequency range of VSWR of below 3 from 2.2GHz to 3.5GHz. This shows broadband characteristics where the range of frequency where the antenna can be used is about 2.630GHz. For the radiation pattern plot of micro patch antenna, due to the normal radiation of the patch surface, the rising patterns of φ = 0 and φ = 90 are important. In Figure 1 below, the antenna benefits of 2.4GHz for φ = 0 and φ = 90 were shown, and the maximum benefit is __ obtained at the side, for total of 1.87 dBi, measured at φ = 0 and φ = 90.

Fig. 1. Elevation Pattern for φ = 0 and φ = 90 degrees

Figure 2 shows the E-area radiation pattern of the antenna. At the 2.630GHz band, where the antenna could be used, the value was 1.60dBi, and 1.81dBi at 2.655GHZ. H-area radiation pattern was 1.24dBi at 2.630, and 1.50dBi at 2.655.

A Study on Design of Microstrip Patch Antenna for Mobile Communication Systems 329

Fig. 2. E-field radiation pattern

Fig. 3. H-field radiation pattern

Figure 3 shows the H-area radiation pattern of patch antenna, which was found to be 1.24dBi at 2.63GHz and 1.50dBi at 2.655GHz. This can be judged to have directivity compared to the existing antenna, but the figure of the radiation pattern shows that reception can be made from all directions, showing that it is suitable for mobile communication.

3 Conclusion

Mobile communication microstrip patch antenna is to be used in mobile

communication system, and thus the resonance frequency of the antenna (0f ) was set

to 2.4GHz, and the dielectric constant (r

ε ) of the board used in the report was set to

2.45, and the height (h ) of the dielectric board was selected to be 1.58mm for the simulation. As the result of simulation, the depth of the optimal feed of the antenna

330 J.-D. Park et al.

was found to be 13.2mm for -27dB, and at this time, the central frequency was found to be from 1.9120GHz to 23.28MHz. The reflection loss of the antenna exhibited frequency range of VSWR being below 3 for 2.2GHz~3.5GHz, showing a broadband characteristic, and also the maximum benefit of the antenna was found to be 1.87dBi at the resonance frequency of 2.4GHz, showing excellent characteristics. Also, the radiation pattern in antenna E-area was found to be 1.60dBi at 2.630GHz, 1.81dBi at 2.655GHz where antenna can be used, and the H-area radiation pattern was found to be 1.24dBi at 2.630GHz and 1.81dBi at 2.655GHz, showing excellent characteristics, which was found to be suitable for mobile communication.

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