Overview

One of the major advantages of array antennas is that the array excitation can be closely controlled to produce extremely-low-sidelobe patterns or very accurate approximations of chosen radiation patterns. Many intricate procedures have been developed for synthesizing useful array factors. These methods fit into three main classes of synthesis: synthesis of various sector patterns that are usually many beamwidths wide, synthesis of low-sidelobe, narrow-beam patterns, and procedures that optimize some (usually receiving) array parameter, such as gain and signal- to-noise ratio, subject to some constraint on the sidelobe level or the existence of outside noise sources.

Most of the synthesis procedures described in the chapter are for narrow-beam, low-sidelobe array factors. However, the Fourier transform method, the Woodward synthesis technique, the alternative projection method, and power pattern synthesis methods are very appropriate for the synthesis of shaped-beam patterns. The chapters by Schell and Ishimaru ^[1], Ma ^[2], and Rhodes ^[3] present detailed treatments of the synthesis problem. Such details are beyond the scope of this text, which is devoted to the task of presenting specific results for practical design.

Throughout this chapter, the synthesis is carried out for arrays with broadside beams, without loss of generality, because the scanned performance is obtained from the broadside pattern by multiplying the excitation coefficients by the exponential factor

for a two-dimensional array. Thus, replacing u by ( u ? u ₀) and v by ( v ? v ₀) will produce the correct equations for...