Abstract
The present work develops an innovative methodology for fixing deep nulls in radiation patterns of symmetrical thinned arrays while maintaining a low side lobe level (SLL) and a high directivity, implementing an optimization strategy based on the simulated annealing algorithm (SA). This procedure optimizes a cost function that has a term for each characteristic of the desired radiation pattern and can distinguish between the deep nulls and the filled ones depending on whether they are on the Schelkunoff unit circle or not. Then, a direct extension of the methodology for planar arrays based on the separable distribution procedure is addressed. Consequently, some examples with half-wavelength spacing are presented, where the fixing of one, two, or three deep nulls in arrays of 40, 60, and 80 elements are illustrated as well as an extension to a 40 × 40-element planar array with rectangular grid and rectangular boundary, with two deep nulls fixed on each one of its main axes. Additionally, a comparison of the obtained results with a genetic algorithm (GA) alternative is performed. The main advantage of the proposed method is its ability to fix deep nulls in the radiation patterns, while maintaining an easy feeding network implementation.
Highlights
The performance of antenna arrays regarding low side lobe level (SLL) and high directivity, at the same time that there is a far field depression on a certain range of their radiation pattern, represents a very interesting concern on antenna array designs with impact on radar [1] and space applications [2], and in the new design strategies for the future 5G communication deployment [3,4], where options such as metamaterialbased antenna designs are becoming of high interest in recent literature [5]
All the described examples are based on linear and planar arrays with interelement spacings of λ/2, and regarding the optimization stage, coefficients of the cost function implemented to obtain the optimized values in each case were c1 = 4, c2 = 2000, and c3 = 100
The values of these coefficients have been set after tuning of the parameters to obtain the results reported in this work
Summary
The performance of antenna arrays regarding low side lobe level (SLL) and high directivity, at the same time that there is a far field depression on a certain range of their radiation pattern, represents a very interesting concern on antenna array designs with impact on radar [1] and space applications [2], and in the new design strategies for the future 5G communication deployment [3,4], where options such as metamaterialbased antenna designs are becoming of high interest in recent literature [5] In this same framework, but concerning channel coding design, low density parity check (LDPC) coding is attracting great attention for improving transmission reliability [6,7]. Array thinning is a technique for the design of antenna arrays, based on removing (or turning off) some elements of an array without significantly changing its beamwidth [8] (p. 92)
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