A high gain 2-element Microstrip array antenna with Circular Polarisation for RFID Applications

Radio Frequency Identification(RFID) is a wireless technology used for tracking a tag attached to an object and uniquely identifying it. In the proposed work, a compact Microstrip antenna that has a high Gain, a good Return Loss (S₁₁), a good Impedance bandwidth and a very good Circular Polarisation working at 2.4 GHz ISM band for RFID Applications has been designed. The antenna has been designed and simulated with Fire Resistant FR4 Epoxy as its substrate. The antenna is an array of 2 elements, has an overall dimensions of 120 × 73 × 1.5 mm³ and has a Microstrip line feed matched to 50Ω. The impedance bandwidth achieved by the design is about 92 MHz (2.44-2.53 MHz) at the 2.4 GHz ISM band and has an S₁₁ of about -16.10 dB. The Gain obtained is around 7.5 dB. The final design has a very good Circular Polarisation(CP) with an Axial Ratio of 0.8 dB and an Axial Ratio bandwidth of 47 MHz(2.430-2.477 MHz). The antenna has a beamwidth of 60°, a broadside radiation pattern and is highly directional. The antenna has been designed using Ansoft High Frequency Simulation Software (HFSS).