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

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. [ABSTRACT FROM AUTHOR]