Sidebands suppression in time-modulated linear arrays using directive element patterns

A technique for reducing the sideband levels of time-modulated linear arrays (TMLA) based on the directive radiation pattern of the array elements is presented. The approach uses a generic modification of conventional time-switching sequences to produce harmonic array factor patterns in which the radiated energy is concentrated in the end-fire regions of space. By combining an array energized with these sequences with a directional element pattern which has low radiation levels at angles corresponding to the end-fire regions, suppression of the array harmonics can be achieved. In particular there is a significant suppression of the dominant first positive, and negative, harmonic frequencies. The approach is illustrated by applying the technique to a 16 element TMLA designed to produce a low-sidelobe Chebyshev radiation pattern.