Analytical, Numerical, and Experimental Results for Wide-Angle Biconical Antennas

Abstract

In a previous paper,1 research on spherically capped, axially symmetric, wide-angle, biconical antennas 2, 3, 4, 5, 6, 7, 8, 9 was generalized to bicones with unequal cone angles. In particular, Samaddar and Mokole1 theoretically analyzed the radiated and received fields of such bicones for ultrawideband (UWB) short pulse excitations, the corresponding radiation patterns versus frequency, and the high-frequency behavior of electrically small and electrically large bicones. In the current discussion, the authors use the theoretical results of the earlier paper to study the input impedance (Zin), the voltage standing wave ratio (VSWR), and the normalized radiated field pattern. The expression for Z in is recast in a more usable form, which is then used to derive an analytical expression for the VSWR. These three quantities are computed numerically by two means: directly from the analytical representations and from Maxwell’s equations with a finite-difference time-domain (FDTD) method. The FDTD results compare reasonably well with the analytical representations. Finally, some preliminary measurements of the normalized radiated field patterns for an electrically small (ka « 1 ), wide-angle (100°), mono-cone (0.60325-cm radius) with a large, finite, circular ground plane (121.92-cm diameter) are compared to a theoretically derived, analytical representation.1 Because an infinite ground plane was assumed in the derivations of the analytical expressions of Samaddar and Mokole,1 the measured patterns for the finite ground plane deviated from the patterns computed with the analytical expressions, as a result of the edge effect of the finite ground plane, especially in the broadside direction.