Log-periodic antenna effect on modulated signals in regions of negative group delay

Abstract

In frequency regions where ultra-wide band log-periodic antennas exhibit negative group delay (NGD), the effect of higher-order modes upon amplitude-modulated signals is examined using convolution theory. It is shown that in these frequency regions, the group delay and the effect of the higher order modes upon amplitude-modulated signals vary throughout the antenna's radiation pattern. It is also shown that the signal time advances predicted by the NGD are due to signal distortion when undesired higher-order modes are present on the antenna.