A Compact Triple-Band Metamaterial Antenna Based on Dual Split-Complementary Split Ring

Resonator Prashant R. T1, Vani R.M2 and Hunagund P.V3

1, 3Dept. of P G Studies and Research in Applied Electronics, Gulbarga University, Gulbarga-585 106, Karnataka, India 2 University Science Instrumentation Centre, Gulbarga University, Gulbarga-585 106, Karnataka, India

1telkar_prashant@yahoo.com

Abstract— A compact triple-band proximity coupled fed rectangular microstrip patch antenna based Metamaterial type dual split-complementary split ring resonator (DS-CSRR) on radiating patch is designed, fabricated and tested. Measured results are good in agreement with IE3D simulation results. The proposed antenna has a size of 35 X 35 X 3.2 mm3 with low cost FR4 glass epoxy substrate having dielectric constant 4.4. The measured impedance bandwidths of 70MHz, 250MHz and 670 MHz at resonating frequency points of 4.28GHz, 5.22GHz and 8.08 GHz are obtained respectively, which are useful for WLAN and X-band applications. The proposed antennas are simple, has good radiation pattern and gain of 5.48 dBi with size reduction of 25.82% was achieved when compared to conventional antenna without DS-CSRR which is resonating at 5.78GHz.

Keywords- proximity fed; DS-CSRR; compact; bandwidth; IE3D;

I. INTRODUCTION Due to technological development, wireless technology has

seen a lot of advancement in last decade. Researchers are highly interested in the design of dual, triple or multiband antennas which could possibly be deployed in mobile communication and integrated circuits with the purpose to replace multiple antennas with single compact structure. Planar microstrip antennas are a very suitable candidate and have attracted a lot of researchers [1 -3]. These applications of planar microstrip antennas are applicable due to their various advantages such as low profile, light weight and ease conformal to host surface. Apart from these advantages, it has some limitations such as low gain, narrow bandwidth, and low efficiency, extraneous radiation from feed and low power handling capacity. These limitations can be overcome by using shorting pin or shorting wall, cutting slots or notch, loading gun or tunnel diode and gap coupling [4.5], but they fail to provide desired results in either compactness or radiation patterns [6]. But in the year 1996 Prof. Pendry was first developed Negative permeability medium, which consists of an array of split ring resonators (SRR). By combining this structure with the array of strip wires, the first left handed medium (LHM) with both negative permittivity and permeability was developed in 2002 [7]. Based on this concept (i.e., metamaterial) many types of SRR variation such as Complimentary split ring resonator (CSRR), double

S-shaped and Ω-like structures are designed and fabricated to exhibit the LH properties [8]. Metamaterials are special artificial structures which have a cell size of sub wavelength dimension exhibiting interesting properties, which lead them to be used in various applications [9-11]. By employing metamaterial in antenna structures, significant reduction in size and dual-band behaviour has been observed.

In this paper, a compact triple-band metamaterial antenna based on dual split-complementary split ring resonator by proximity coupled fed technique is proposed. Simulation work has been carried out by using method of moment full wave electromagnetic simulation software IE3DTM [12].

II. DESIGN OF ANTENNA AND DS-CSRR STRUCTURE Geometry of proximity coupled fed rectangular microstrip

patch antenna (PCRMSA) is shown in Fig. 1. The patch antenna structure consists of a defined metallic rectangular patch on the top side of patch substrate (h2) and metallic ground plane placed on other side of feed substrate (h1). The simulations for proposed antennas are performed on FR4 glass epoxy substrate. The rectangular patch is fed by electromagnetically coupled microstrip feed line placed between two FR4 dielectric substrates with relative permittivity (εr) of 4.4 with thickness (h) of 1.6 mm for both the substrates. The conventional PCRMSA is designed for 5.80GHz [1] with patch dimensions Lp=10mm and Wp=15mm radiating part, which is excited by simple 50Ω microstrip feed having dimensions length Lf =20mm and width Wf =3mm. The feed line is centred with respect to the centre of the radiating patch of an antenna. The bottom ground plane of antenna is calculated by Lg=6h+L and Wg=6h+ W which is length Lg=35mm and width Wg=35mm.

Fig. 1 Geometry of proximity coupled fed rectangular microstrip patch

antenna

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In the next step by keeping all the parameters of the PCRMSA same, only the radiating part is etched with DS-CSRR type metamaterial. The study is carried out by etching out sing unit of square DS-CSRR on the (x, y =0mm) of the radiating part and which is named as proximity coupled fed rectangular microstrip patch antenna with Dual Split- CSRR (PCRMSA DS-CSRR) as shown in Fig. 2 (b).

(a) (b)

Fig. 2 Proposed models of (a) PCRMSA (b) PCRMSA DS-CSRR Fig. 3 (a) & (b) shows the structure of dual split-split ring

resonator and dual split-complementary split ring resonator with the design parameters of SL = 7.2mm, Sw=0.2mm, g= 0.2mm, and S= 0.2mm. Fig. 4 shows the photographic view of the proposed PCRMSA and optimized PCRMSA-DS-CSRR.

(a) (b)

Fig. 3 (a) A dual split-split ring resonator (b) dual split-complementary split ring resonator (DS-CSRR) with the design parameters

Fig. 4 Photographic view of the proposed PCRMSA and PCRMSA DS-CSRR

III. RESULTS AND DISCUSSIONS The proposed antennas are designed by using method of

moment full wave electromagnetic IE3D simulation software and measured experimentally using Vector Network Analyzer (Rohde and Schwarz, Germany-made ZVK model 1127.8651). Fig. 5 shows the simulated and measured return loss characteristics of conventional PCRMSA. From this figure it is clear that the antenna is resonating at Fr =5.78 GHz which is designed for 5.80GHz with a minimum return loss of -35dB. The obtained bandwidth below -10dB is 640MHz (i.e., 11.07%). The impedance bandwidth over return loss less than -10dB is determined by using the equation,

2 1 x100%f fBW

fc⎡ ⎤−

= ⎢ ⎥⎣ ⎦

Where, f1 and f2 are the lower and upper cut-off

frequencies of the band respectively, when its return loss reaches -10dB and fC is the centre frequency between f1 and f2.

Fig. 5 Simulated and measured return loss characteristics of proposed

PCRMSA

Fig. 6 shows the simulated and measured return loss characteristics of proposed PCRMSA DS-CSRR which is resonating at three particular frequency points i.e., Fr1=4.28 GHz, Fr2= 5.22GHz, and Fr3= 8.80GHz with bandwidths of 1.63%, 4.78% and 8.29% along with minimum return loss of -13.87dB, -22dB and -21.86dB respectively. Due to the inclusion of DS-CSRR type metamaterial the antenna is resonating for triple resonating points instead of a single resonance. From these results we observe that by implementing the DS-CSRR the virtual size reduction of 25.82% is obtained compared to conventional PCRMSA.

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Fig. 6 Simulated and measured return loss characteristics of proposed

PCRMSA DS-CSRR

TABLE 1: SIMULATED AND MEASURED PARAMETERS OF PROPOSED ANTENNAS

The Fig. 7(a) shows simulated radiation pattern of

PCRMSA at 5.80GHz, (b) PCRMSA DS-CSRR at 4.02 GHz (c) at 5.35 GHz and (d) at 9.01 GHz. From the figures it is observed that all radiation patterns are broadside in nature.

(a) (b)

(c) (d)

Fig. 7 Radiation pattern of (a) PCRMSA at 5.80GHz, (b) PCRMSA DS-CSRR at 4.02 GHz, (c) at 5.35GHz and (d) at 9.01GHz

Fig. 8 shows the surface current distributions of (a) PCRMSA at 5.80GHz. The current is flowing in almost entire patch, the different colours represents different magnitudes of the current and the maximum current is 10.29 A/m, (b) PCRMSA DS-CSRR at 4.02 GHz, (c) at 4.32GHz and at 9.01GHz here the current follows the curvature of the CSRR.

(a)

(b)

(c)

Antennas Resonating Frequency

(GHz)

Minimum Reflection Co-efficient(dBi)

Bandwidth (%)

Sim Meas Sim Meas Sim Meas PCRMSA 5.80 5.78 -35 -23.61 10.32 11.07 PCRMSA DS-CSRR

4.02 4.28 -33.95 -13.87 2.06 1.63 5.35 5.22 -15.71 -22 4.93 4.78 9.01 8.08 -17.14 -1.86 16.44 8.29

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(d)

Fig. 8 The surface current distribution of the proposed antenna

(a) PCRMSA at 5.80GHz (b) PCRMSA DS-CSRR at 4.02 GHz, (c) at 5.35GHz and (d) at 9.01GHz.

IV. CONCLUSION A triple-band metamaterial dual split-complementary split

ring resonator (DS-CSRR) with proximity fed is proposed. The triple-band characteristic of the microstrip patch antenna is achieved due to the loading of DS-CSRR on the radiating part of proximity fed microstrip patch antenna. This technique considered to achieving both the reduction in antenna size and improvement in the impedance bandwidth of proximity fed microstrip patch antenna with multiple resonances. To verify the simulated results, the prototype antenna is fabricated and measured. It is found that the simulation and the measurement are reasonably good in agreement. The results presented in this paper are promising for designing metamaterial loaded proximity coupled fed rectangular microstrip patch antenna for wireless applications.

ACKNOWLEDGMENT The authors acknowledge there thanks to UGC, New

Delhi for sanctioning of the IE3D simulation software under Major research project and DST, New Delhi for sanctioning Vector Network Analyzer for measuring the parameters of proposed fabricated antennas which is most useful and reliable for designing microstrip antennas.

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