The main objective of this work is to make a comparative study of the radiation patterns of circular patch antenna excited in transverses magnetics modes TM11, TM21, TM31, TM41, TM51 and TM61. This antenna is printed on a Epoxy substrate having a dielectric constant of 4.4 and designed at a height 1.58mm from the ground plane. This study is based on the model approach of the resonant cavity and intended for microwave band RFID reader around a resonance frequency of 2.45 GHz. The simulation results show that the far field components Eθ and Eø for dominant mode TM11 present the better results in term of amplitude at θ = 0° compared to higher order modes TM21, TM31, TM41, TM51 and TM61. The simulation was made by MATLAB program.