Novel Quadrifllar Helical Antenna for RFID Applications Using Genetic Algorithms

For excellent tag-read communication in RFID applications, an interrogator equipped with an antenna having a circularly polarised radiation pattern is required. The antenna must also maintain a low proflle and be compact for ease of installation. A more compact QHA is developed by linearly-shifting its helical elements for minimal optimum quadrature-distance. As a result, a novel QHA design, a \linearly-shifted quadrifllar helical antenna" (LSQHA) is pro- posed to operate at 900MHz RFID applications using Genetic Algorithm (GA) driver with the industry-standard NEC-2 computational analysis program. Performance of the GA-optimised antenna shows that it has a 3dB beamwidth of 90 degrees and a total gain of 13.1dBi at the design frequency of 900MHz. The proposed antenna excellently meets VSWR and return loss requirements within the frequency boundary of (875{912.5)MHz. The performance also shows that the proposed LSQHA is circularly polarised.