Multi-Beam Near Field Focusing Characteristics of Microstrip Patch Antenna Array

Several modern-day antenna applications require the radiated fields to be focused at a predetermined point away from the antenna to perform different tasks, such as sensing, testing, charging, diagnosing, and treatment of different medical conditions. In this thesis, a thorough study has been made to investigate the characteristics of near-field focusing. In many applications, along with focusing the radiated fields at a focal point, it is also required to move that focused beam to scan a specific region i.e., usually carried out either electronically or physically by changing the position of the antenna array. The thesis proposes a robust mechanism to move the focused beam at single and dual focal points to improve the scanning properties of the antenna array. The proposed mechanism does not depend upon any external phase shifter circuit or changing the position of the array for focusing and scanning the focused beam. The movement of the focused beam is achieved as a result of introducing extra transmission lines to the scanning axis of the array. Antenna designs for single-focal and dual-focal points are analyzed using MATLAB and CST simulation software. The simulation results show that the proposed designs work efficiently as the movement of the beam is controlled by the change in frequency. Furthermore, in the case of dual focal point near field focused antenna array, there is a significant increase in the scanning distance as compared to the single focal point. The proposed mechanism results in an increment in scanning distance of around 53%. The proposed designs can be used in applications such as RFID, Non-destructive industrial inspection and testing, and wireless power transfer, where the focused beam is to be directed at a point in the near-field and the scanning of the focused beam is required as well. Keywords: microstrip patch antenna array, near-field focusing, parasitic patch, hyperthermia, beam scanning.