Effects of Shading on Minor-Lobe Level and Beamwidth in Symmetrical Uniformly Spaced 6- and 4-Element Arrays

Abstract

The effects of shading on number of minor lobes, level of minor lobes with respect to the principal lobe, and beamwidth are analyzed for symmetrically shaded, uniformly spaced 6- and 4-element arrays. For a 6-element array shaded 1:a:b:b:a:1, there are no minor lobes above the parabola 125−30 a+a2−20b=0. Between this parabola and 5−2 a+a2−4b=0, there is one minor lobe, while between the second parabola and the straight line b−3a+5=0 there are two minor lobes, which may or may not be equal in amplitude. Below the straight line, there is again only one minor lobe. Curves in the a-b plane for constant first and second minor-lobe levels are presented, as well as curves of constant beamwidth for the half-wavelength spacing. For the 4-element array shaded 1:c:c:1, there are no minor lobes when c is greater than 3. Curves for minor-lobe level and beamwidths for the half-wavelength spacing as a function of c are presented.