Keywords

1 Introduction

In today’s fast developing world, the most unavoidable thing in our life is mobile phone. As its need is increasing, the requirement of wireless technologies such as GSM, LTE, and WLAN [1] is also increasing. The rapid growth of mobile phones is also leading to a threat of harmful radiations from these mobile phones and the subsequent health problems. Since no one can think about avoiding the phones, the only possible solution is to reduce the radiation emitted by the mobile phones [2]. Certain methodologies have to be implemented while designing these mobile phones. When compared with the conventional antennas, the metamaterial antenna decreases the number of the antenna elements and enhances antenna performance. Metamaterial-supported antennas will have gain improvement, [3] bandwidth enhancement, high efficiency, etc. The highly efficient antennas are in a huge demand especially to work in service bands like global system for mobile communication (GSM-900, GSM-1800), [4] wireless LAN(WLAN) at 2.4 GHz [5] and 5 GHz, long-term evolution (LTE) [6] cover three bands (698–966 MHz, 1.427–2.69 GHz, 3.4–3.8 GHz), etc. [7]. The enhanced performance of metamaterial antennas makes them highly potential structures in wireless communication systems.

2 Metamaterials

The word metamaterial is derived from Greek word ‘meta’ and Latin word ‘materia’ meaning beyond and matter, respectively [8]. Metamaterials are artificial materials on which a particular property is being induced which the material does not possess naturally. These property may be due to its shape, structure, size or the geometry which it has, leading to changes in the electromagnetic property of the material [9]. So these properties are not derived from the base materials but from the internal microstructure [10]. The core objective of usage of metamaterial is that these materials help us to achieve the desired properties [11]. These desired properties are achieved, when necessary changes are made in the geometry which results in change in refractive index [12], either to a positive value, or a negative value resulting in achieving the property.

3 Split Ring Resonator

Split ring resonators (SRR) are structures which consist of two metallic rings that are etched on the dielectric material, and they also consist of slit which are etched at opposite sides [13]. These are structures that are mainly used by metamaterials in order to get the derived property [14]. It is mainly used for producing desirable magnetic susceptibility. Split ring resonators are having strong magnetic coupling and they are much more than ferromagnetic materials. Several kinds of split ring resonators are present and one such is complementary split ring resonator (CSRR) (Fig. 1).

Fig. 1
figure 1

Split ring and complementary split ring resonator

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4 Antenna Design

Antenna 1 in Fig. 5a is the initial antenna with a CPW L-shaped fed structure. Apparently on the dielectric substrate of the CPW structure, a lump with two diminished slits ground electrodes lied alongside and parallel to the strip on the same surface. It is fabricated using FR4 substrate which is having a relative permittivity of 4.5, loss tangent of 0.02 and thickness of 0.8 mm. The material is capable of retaining its mechanical characteristics and electrical insulation in dry as well as wet conditions. Along with good manufacturing, it can be utilized for various mechanical and electrical applications. All the dimensions of the antennas are in millimetres (mm). The substrate is in a square shape with an edge G1, and the overall size was 114 × 114 mm.

The geometry has L-shaped microstrip line acting as the patch. Here, dual band is obtained, but at lower frequencies the antenna gain and bandwidth are less. Usually for the gain improvement and bandwidth enhancement metamaterials are used, as they are utilized for achieving the desired properties. The antenna is modified by using a complementary circular split ring (CSRR)-based metamaterial as shown in Fig. 2b. The circular unit cell used in the antenna structure is shown in Fig. 2c. The complementary split ring is placed at the bottom of the CPW and is utilized to resonate at 1.8 GHz and 5.7 GHz, respectively. We obtained a band of 0.92–2.76 GHz and 5.02–7.1 GHz where 1.8 GHz and 5.7 GHz are included in these bands so that the proposed antenna is suitable for GSM, WLAN, LTE and RFID applications.

Fig. 2
figure 2

Structure and dimensions of initial and proposed final antenna: G1 = G2 = 114 mm, L = 4 mm, L2 = 40 mm, W1 = W3 = 5 mm, L1 = 30 mm, W2 = 24 mm, r1 = 6 mm and r2 = 4.5 mm

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5 Results and Discussion

5.1 Return Loss

The return loss plot, VSWR, radiation patterns and 3D polar plots are shown in Figs. 3, 4 and 5.

Fig. 3
figure 3

Return loss plot for the antennas shown in Fig. 3

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Return loss values of − 18.9, − 11.2 dB are obtained at 1.8 and 5.7 GHz for antenna without metamaterial and − 24db, − 20.5db are obtained at 1.8 GHz and 5.7 GHz for antenna with metamaterial which is useful for GSM, WLAN, LTE and RFID applications.

5.2 VSWR

The values of VSWR are 0.93 and 1.54 at 1.4 and 5.2 GHz for antenna without metamaterial. The values of VSWR are 1.05 and 1.7 at 1.8 GHz and 5.7 GHz for antenna with metamaterial. This shows that the proposed design is well matched and antenna is well suited for GSM, WLAN, LTE and RFID applications (Fig. 4).

Fig. 4
figure 4

VSWR for the antennas shown in Fig. 1

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Fig. 5
figure 5

Radiation pattern for antenna 1 at a f = 1.4 GHz b 5.2 GHz and Radiation pattern for antenna 2 at c f = 1.8 GHz d f = 5.7 GHz

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5.3 Radiation Pattern

Figure 5a, b depicts the radiation pattern of antenna 1 in Fig. 2. Figure 5c, d depicts the radiation pattern of antenna 2 in Fig. 2. The variation of the power radiated by an antenna as a function of the direction away from the antenna is depicted by the radiation pattern of an antenna [5]. Figure 5a shows the radiation pattern centred at 1.4 GHz which is slightly deviated. Figure 5b shows the radiation pattern at 5.2 GHz which is more deviated than the pattern at 1.4 GHz. Figure 5b shows the radiation pattern centred at 1.8 GHz and Fig. 5c shows the radiation pattern at 5.7 GHz. It shows that at higher frequencies the radiation pattern undergoes distortion.

5.4 Gain

Figure 6a, b represents the 3D polar plot of the antenna 1 shown in Fig. 5. Figure 6c, d represents the 3D polar plot of the antenna 2 shown in Fig. 2. It can be observed from the plots that the gain at 1.4 GHz and 5.2 GHz is 2.5 dB and 5 dB. The gain at 1.8 GHz and 5.7 GHz is 4.8 dB and 6.2 dB, respectively. Hence, it shows that the gain is increased when antenna structure is modified using metamaterial.

Fig. 6
figure 6

3D polar plot for antenna 1 at a f = 1.4 GHz b f = 5.2 GHz and antenna 2 at c f = 1.8 GHz d f = 5.7 GHz

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This project mainly emphasizes on wireless bands, which mainly includes global system for mobile communication (GSM), wireless local area network (WLAN), long-term evolution (LTE) and radio frequency identification (RFID) applications. We could see that the designed antenna could be effectively used in these wireless band frequencies.

6 Conclusion

The evolution in wireless communication and electronic warfare systems in new era led to the emergence of metamaterial antennas resulting in increasing the efficiency or performance of the antenna to a greater extent. In order to adapt with the wireless communication systems in this modern era, ‘A dual band metamaterial loaded CPW-fed antenna for GSM, WLAN, LTE and RFID applications’ is introduced. The antenna is designed in two stages by introducing and without the complimentary split ring resonators. It was found that by using complimentary split ring resonators the antenna is able to provide high gain and bandwidth. The results obtained after simulation ensure that the antenna functions well in the lower (0.92–2.76 GHz) as well as in upper (5.02–7.11 GHz) frequency range. Since it covers the frequency band of GSM, WLAN, LTE and RFID, it is possible to use this antenna in these applications. The fabrication of antenna is much easier as well as it is simple, economical and also appropriate for small portable devices.