Circular Microstrip Antenna inspired by Metamaterial and U-shaped Notch for ISM Applications

Metamaterials have drawn the considerable attention of researchers in recent years because of their promising applications in the field of electromagnetics, especially antennas. The metamaterial-inspired structures can provide a negative index of refraction which results in the enhancement of qualitative parameters of the Antenna. In this article, the design of a circular microstrip antenna (CMSA) along with an inverted rectangular U-shaped notch in the radiating patch and a Split Ring Resonator (SRR) in the ground plane as a metamaterial structure is illustrated. The unit cell structure of SRRs is analyzed and its electromagnetic behaviour on the proposed antenna structure is elaborated. The etching of SRR unit cells into the ground plane of CMSA forms a discontinuous ground plane. The surface current lengthening with a slight reduction in resonating frequency is observed by cutting an inverted rectangular U-shaped notch in the radiating structure of CMSA. The combined effect of notching and SRR structures etched in the ground plane provides overall broadband operation. The designed microstrip line-fed CMSA resonates at a frequency of 2.45GHz and with the size 0.294λ
0
× 0.506λ
0
× 0.013λ
0
(where λ
0
is the free-space wavelength at 2. 45GHz). The overall structure is analyzed and validated using HFSS (High Frequency Structure Simulator). The frequency is shifted slightly from 2. 46GHz to 2. 48GHz with a -10dB|S
11
|bandwidth of 60MHz(fractional bandwidth 2. 44%) and a reflection coefficient of – 23. 39dB therby showing a matched characteristic in terms of reflection coefficient and Voltage Standing Wave Ratio (VSWR). The overall gain of the antenna is just improved from 1. 5dBi to 2. 4dBi. The features of this proposed antenna design have appealing characteristics in the ISM band along with small size, low cost, and broadband operation.