CONCENTRIC MICROSTRIP RING ANTENNA - THEORY AND EXPERIMENT

The impedance and radiation properties of an electromagnetically fed c oncentric microstrip ring antenna using log-periodic principle is inve stigated experimentally and compared with those of two single ring res onators. The experimental result is verified numerically by Finite Dif ference Time Domain (FDTD) method. The variation of voltage standing w ave ratio with frequency is also measured and computed numerically for both the single rings and concentric structure. The comparison betwee n numerical and experimental results shows good agreement over a wide frequency range. The results indicate a considerable improvement of 1: 2 VSWR bandwidth for the concentric structure.