Synthesis of highly directive broadside arrays using nested Chebyshev polynomials

This paper presents the synthesis of highly directive broadside array using nested Chebyshev polynomials. It is known that, the best possible directivity is achieved by uniform excitation coefficients. It is also known that by reducing the inter-element spacing d to less than
$\frac{\lambda}{2}$
invisible regions are created in the radiation characteristics. Improved radiation characteristics can be theoretically achieved by increasing the radiation intensity in the invisible regions. Nested Chebyshev polynomials have been used to achieve this condition. Simulations showed a significant improvement in the half power beamwidth, without any degradation in the side lobes for
$\mathbf{d}=\frac{\lambda}{4}$
.