Theoretical investigations of an annular elliptical ring microstrip antenna using Green´s function technique

Analytical expressions for the Green´s function of an annular elliptical ring microstrip antenna (AERMA) are developed and reported. The modal, radiation and input impedance characteristics of the TM_nm modes are determined from these expressions. The resonant frequencies of odd modes are greater than that of the even modes for all TM_nl modes (n=1, 2, 3,...) unlike elliptical microstrip structures. The radiation pattern and input impedance curves of the TM₁₂ mode, on comparison with available experimental results, show good agreement which provides an independent validation to this technique. The performance of the AERMA is then investigated as a function of thickness and substrate dielectric permittivity