Compact End-Fire Arrays: from Theory to Directivity and Gain Maximization

End-fire arrays are among the best candidate for high directivity and compact dimensions. Several solutions for the synthesis of superdirective arrays have been proposed in the literature. However, what is called a "superdirective" array suffers inevitably from high losses and very poor radiation efficiency. More appealing is the joint optimization of directivity and efficiency, or the intrinsic gain, of the antennas. This paper set side by side the directivity and gain optimization methods based on the Spherical Wave Expansion (SWE) theory. The synthesis of superdirective and supergain end-fire arrays is proposed when Huygens sources, which attain the highest level of directivity, or simple bent dipoles are selected as elements of the array. On behalf of the spherical modal expansions, the results obtained for different optimizations of the two arrays are examined.