Is. Misra et Sk. Chowdhury, CONCENTRIC MICROSTRIP RING ANTENNA - THEORY AND EXPERIMENT, Journal of electromagnetic waves and applications, 10(3), 1996, pp. 439-450
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.