microstrip antenna side lobe suppression using left- handed metamaterial...

The 3 rdInternational Conference on Radar, Antenna, Microwave, Electronics and Telecommunications (ICRAMET) 2014

Batam– Indonesia | 7 – 8 May 2014

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Microstrip Antenna Side Lobe Suppression Using Left-

Handed Metamaterial Structure

Fitri Yuli Zulkifli1, Pamela Kareen

1, Basari

1 and Eko Tjipto Rahardjo

1

1Antenna, Propogation and Microwave Research Group (AMRG)

Dept. of Electrical Engineering, Faculty of Engineering, Universitas Indonesia

Kampus Baru UI Depok, Indonesia

E-mail: [email protected] , [email protected] , [email protected] , [email protected]

Abstract— In this paper, a Left-Handed Metamaterial (LHM)

structure has been designed at frequency 2.9-3.1 GHz for radar

application. LHM structure is placed at the top of the microstrip

antenna in order to suppress the side lobe level. The simulation

result shows that the side lobe level has been suppressed from -

9.2 dB to -12.8 dB at phi = 0 The Computer Simulation

Technology (CST) Studio Suite is used to simulate and show the

specification of the design.

Keywords: left-handed metamaterial (LHM), metam terial, side

lobe level suppression.

I. INTRODUCTION

Antenna for radar application plays an important role for

the whole radar system, therefore the antenna specification

tends to be quite advance. For example is the coastal

surveillance radar. For this radar, besides the frequency band

and antenna gain, the side lobe suppression must also be very

low to be able to detect objects precisely.

Several methodes are conducted to suppress the side lobe

level using antenna arrays with various synthesis technique

like chebyschev [1], some others use reflector [2] and also

electromagnetic band gap [3]. In this paper, left handed

metamaterial structure is proposed to suppress the side lobe

level.

II. METAMATERIAL THEORY

Electromagnetic metamaterials (MTMs) are broadly

defined as artificial effectively homogeneous electromagnetic

structures with unusual properties not readily available in

nature. There are several classification of metamaterials based

on their fundamental properties, which are their permittivity

and permeability. The double positive (DPS) metamaterials

have both positive permittivity and permeability ε > 0, μ > 0.

The epsilon-negative (ENG) metamaterials have the

permittivity less than zero ε < 0, μ > 0. The mu-negative

(MNG) metamaterials have the permeability less than zero ε >

0, μ < 0. The double negative (DNG) metamaterials have both

the permittivity and permeability negative ε < 0, μ < 0 [1].

The four possible sign combinations in the pair (ε,μ) are (+,

+), (+, -),(-, +), and (-, - ), as illustrated in the ε – μ diagram of

figure 1 [4] .

In the first quadrant (ε > 0 and μ > 0) represent right-

handed metamaterial (RHM), which support the forward

propagating waves. The second quadrant (ε < 0 and μ > 0)

denotes electric plasma, which support evanescent waves. The

third quadrant (ε < 0 and μ < 0) is the left-handed

metamaterial (LHM) supporting the backward propagating

Figure 1. Permittivity-permeability (ε – μ) and reactive

index (n) diagram. [4]

mailto:[email protected]






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waves. The fourth quadrant (ε > 0 and μ < 0) represents

magnetic plasma, which support evanescent wave.

III. LHM METAMATERIAL STRUCTURE

The DNG material unit cell employs split ring resonators

and thin wires. Thin wire structures produces effective

negative dielectric permittivity below the plasma frequency

and the split ring resonators can result in an effective negative

permeability over a particular frequency range [4]. Table 1

shows the specification of the LHM structure.

Tabel 1. Specification of the LHM structure

Parameters Dimension Unit

Substrate FR-4 -

Dielectric constant (εr) 4.6 -

Loss tangent 0.025 -

Thickness (h) 1.6 mm

Operating frequency 2.9-3.1 GHz

Figure 2 is the dimension of the LHM structure.

Where a = 0.25mm, b = 0.5mm, c = 1mm, d = 7mm, e = 37mm, f = 32mm, and g = 75mm.

IV. SIMULATION

A. Simulation of the LHM Structure

Simulation of the LHM structure is carried out using

Computer Simulation Technology (CST) Studio Suite

software. Before the simulation, the boundary condition has to

be set and shown in fig 3. The top and bottom of the LHM (y-

axis) is given Perfect Electric Conductor (PEC), the front and

behind of the LHM (z-axis) is given open add space, the left

and right of the LHM (x-axis) is given Perfect Magnetic

Condition (PMC). After the setting of the boundary condition,

the port is placed at the z-axis as the wave source.

V.

TABLE I. PERMEABILITY

Figure 4 shows the simulation result of the LHM structure.

To determine that the structure has LHM characteristic, therefore Nicholson, Ross and Weir (NRW) formula are used to calculate the value of the permittivity and permeability of the LHM Structure, using the equations as follow [4]:

(1)

(2)

Figure 2. Dimension of the LHM substrate

Figure 3. LHM simulation setup

g

g

b c

a

c d

d

e

f

Figure 4. LHM simulation result



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(3)

(4)

Where: μr is permeability, εr is permittivity, ω is the frequency in Radian, c is the speed of Light, and d is the thickness of the substrate.

Permittivity and the permeability using NRW method is

calculated using the MS-Excel. Table 2 shows the result of the

calculation. Tabel 2. Permeability and Permittivity of LHM metamaterial

structure

Figure 5 and figure 6 show at the frequency 2.9-3.1 GHz the LHM structure has negative permittivity and permeability. This structure can also be called double negative (DNG) structure.

B. MICROSTRIP ANTENNA WITH LHM STRUCTURE

Figure 7(a) shows the microstrip antenna that operates at

frequency 2.9-3.1 GHz [5] that will be added with the LHM

structure. To get a better result of side lobe level suppression,

the LHM structure is added on top of the antenna design.

LHM structure is placed at the top of the microstrip antenna

shown in the figure 7(c) with an air gap 0.05λ.

Frequency

(GHz) Re [μr] (μ)

Re [εr]

(μ)

2.9 -2.59 -3.09

3 -1.40 -1.58

3.1 -1.00 -1.09

Figure 5. Permeability vs Frequency

Figure 6. Permittivity vs Frequency

(a)

(b)

(c)

Figure 7. (a) Microstrip antenna (b) LHM structure

(c) Exploded view of microstrip antenna with LHM

structure



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Figure 8 shows the result of S11 of the microsrtip antenna with and without LHM structure. The black line is without LHM structure and the red line is the S11 microstrip antenna with LHM structure.

Figure 9 shows the radiation pattern of the microstrip antenna without LHM structure at phi = 0 at frequency 2.952. It shows that the side lobe level is -9.2 dB. Figure 10 is the radiation pattern at the same frequency for microstrip antenna with LHM structure at phi = 0 and it shows the side lobe level is suppressed to -12.8 dB.

Figure 9. radiation pattern at phi=0 without

LHM structure

VI. CONCLUSION

The LHM metamaterial structure has been designed with

both negative permittivity and permeability and work at

frequency 2.8 -3.1 GHz. The microstrip antenna with the

LHM structure can reduce the side lobe level of the microstrip

antenna from -9.2 dB to -12.8 dB at phi = 0.

Figure 8. S11 Microstrip antenna with and without LHM structure

Figure 10. radiation pattern at phi=0 with LHM structure



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REFERENCES

[1] Fitri Y.Z, Taufal H., Basari, Eko T.R, “Sidelobe Level Suppression

Using Unequal Four-Way Power Divider for Proximit Coupled Microstrip Antenna”, Asia-Pacific Microwave Conference (APMC),

2013, pp.1166-1168.

[2] Lestari, A.A.; Hakkaart, P.; Zijderveld, J.H.; Zwan, F.V.D.; Hajian, M.; Ligthart, L.P., “INDRA: The Indonesian Maritime Radar” Proceedings of the 5th European Radar Conference, 2008

[3] L. Li, X.J Dang, C.H Liang. “Analysis and Design of Waveguide Slot Antenna Array Integrated With electromagnetic Band-Gap Structures”. Antenna and Wireless Propagation Letters. Vol.5. pp 111-116. Desember 2006.

[4] Caloz, C. and T. Itoh, Electromagnetic Metamaterials Transmission Line Theory and Microwave Applications, Wiley Inter Science, 2006.

[5] Taufal H., Fitri Y.Z., Basari, Eko T.R.,“Bandwidth and Gain Enhancement of Proximity Coupled Microstrip Antenna Using Side Parasitic Patch”, International conference on Radar, Antenna, Microwave, Electronic and Telecommunications (ICRAMET) 2013

DISCUSSION

1. Mashury Wahab

Q: How to suppress the side lobe?

A: There are many ways to suppress the side lobe. One

example is to use reflector. We plan to combine the

metamaterial technique with reflector or maybe using

another material to meet the desired specification.

2. Syamsu Ismail

Q: How to get the material?

A: We use PCB substrate as with the common material. We

do not make material. Our purpose is to design a structure

so that ε < 0 and μ < 0

microstrip antenna side lobe suppression using left- handed metamaterial...

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