Short Paper—Bandwidth Enhancement of Microstrip Patch Antenna by Using Metamaterial Bandwidth Enhancement of Microstrip Patch Antenna by Using Metamaterial

In this paper we designed microstrip patch antenna by using metamaterial to improve antenna bandwidth. We inserted Complementary Split Ring Resonator (CSRR) structure between the ground and patch in the substrate. We compared our design with the conventional microstrip patch antenna in point of bandwidth. We obtained bandwidth improvement by 800MHZ. Simulation was obtained by using High Frequency Structure Simulation (HFSS) simulator. Keywords—Microstrip patch antenna, metamaterial, complementary split ring resonator, bandwidth.


Introduction
The idea of Material which is known Left Handed Materials (LHMs) dates back to (1967), when Veselago [1] considered theoretically electromagnetic plane wave propagation in a lossless medium with simultaneously negative real permittivity and permeability at a given frequency. In order to describe a LHM, we need to start with a description of a Right Handed Material (RHM) first. In general, materials have two unique parameters, permeability and permittivity that determine how the material will interact with electromagnetic radiation, which includes light, microwaves, radio waves, even x-rays. A RHM is a material whose permeability and permittivity are simultaneously positive. RHMs are also called Double Positive Material (DPS) in the literature. If the direction of the Electric field (E) and the Magmatic field (H) are represented by the thumb and the index finger of the right hand respectively, then the middle finger gives the direction of propagation of the wave, if it is placed normal to both fingers. Additionally, in RHMs wave propagation or the energy flow represented by Pointing vector = .
[ × * ] and the phase changes represented by ) are in the same direction as shown in Figure 1. Electromagnetic waves propagation in all known natural materials follows the right hand rule, with positive refractive indexes [2]. On the other hand, a LHM is a material whose permeability and permittivity are simultaneously negative. LHMs also called Double Negative Materials (DNGs). LHM as defined by Sihvola [3], is an engineered material that does not exist in nature which gains its material properties from its structure rather than inheriting them directly from the material. In such a medium, LHM, if the direction of the electric field (E) and the magmatic field (H) are represented by the thumb and the index finger of the left hand respectively, then the middle finger gives the direction of phase changes of the wave ( = √( )√( ) * ) if it is placed normal to both fingers. In a LHM medium the energy flow = .
[ × * ] and the phase changes represented by phase constant ( ) are in opposite directions (anti-parallel) as shown in Figure 2. Propagation of type is called backward propagation [1].

Fig. 2. Wave Propagation in left handed medium.
Considering the effect that the LHM has on the refractive index ( ) defined by equations (1) to (3): where: = Relative permeability of material = Relative permittivity of material When both permittivity and permeability are negative, thus equation takes the following: Which reduces to

) Antenna Design
In order to obtain enhanced characteristics and good performance, the double layered substrate concept is applied to a metamaterial loaded micro strip antenna .Initially micro strip antenna, which is a square patch with a resonant frequency of (2.4)GHz, will be designed [4]. Then it will load with a metamaterial Complementary Split Ring Resonator (CSRR) structure between the ground and patch in the substrate. The inclusion of the metamaterial has shown an increase in the bandwidth, but there has to be a tradeoff with the gain, as it was found to reduce, thereby becoming a drawback. Another substrate will then be added over the previous one, which will increase the effective dielectric constant, thereby increasing the gain along with the bandwidth. The effective dielectric constant is found to increases. The substrate used for the second layer, FR4 Epoxy substrate having a dielectric constant of 4.4 that use in the first layer. The height of the substrate selected as 2 mm and the dimensions of the substrate to be 50 mm which is a square patch with dimensions 25 mm. The micro strip feed, which is essentially a micro-strip line, 4.5 mm in length and 2 mm thick [5 -13].

Simulation and Results
The proposed antenna has been simulated by using High Frequency Structure Simulation (HFSS) as shown in figures 4 and 5.   For antenna without metamaterial we obtained one resonance frequency at 8.8GHz. For the design with metamaterial we obtained two resonance frequencies at 4.6GHz and 8.8GHz. We got an improvement in the gain for 8.8GHz by 800MHz.  We obtained almost the same radiation pattern for both cases.
iJIM -Vol. 14, No. 1, 2020  We observed that we have improvement in the gain for the case of antenna with metamaterial by 1dBi.
As can be seen from the above Figures 8 (a), 8 (b) that the (-10) dB bandwidth is increased with metamaterial. The bandwidth of patch antenna with metamaterial is 800MHz.

Conclusion
The main problem in microstrip patch antenna is narrow bandwidth. By using metamaterial we can increase the antenna bandwidth. In this paper we designed microstrip patch antenna by using metamaterial to improve antenna bandwidth. We inserted Complementary CSRR structure between the ground and patch in the substrate. We compared our design with the conventional microstrip patch antenna in point of bandwidth. We obtained bandwidth improvement by 800MHz. Simulation was obtained by using HFSS simulator.