Numerical research of bowtie Sierpinski fractal patch antenna in RFID

A Method of Moment (MoM) model is built by RWG (Rao-Wilton-Glisson) vector basis function which is suit both for lines and surfaces. Use this model the surface currents in a Sierpinski fractal patch antenna in RFID are calculated and the radiated performances are obtained when flare angle is 30°, 60° and 90° respectively. Results show that currents flow mainly along edges of triangles and the antenna behaviors a multi-band characteristic. When flare angle becomes broader firstly the resonant frequencies move towards the lower band which means that narrower flare angle benefits to antenna miniaturization; secondly the input impedance level becomes smoother and the minimum reflected coefficient becomes smaller and moves to higher resonant frequencies which means that broader flare angle benefits to radiation in higher frequencies; last the radiation pattern becomes more similar between each other. In brief variation in the flare angle brings about contradiction between miniaturization and radiation ability of the antenna. A compromise between mechanical property and electric performance should be adopted in antenna applications.