Superdirective endfire antenna arrays

Efficient superdirective array functions can be generated using an optimized polynomial technique[1]. In this paper we further investigate methods for the generation of these functions and study the effects of changing the number of elements and array length on the different array parameters. Legendre polynomials have been used for the first time as optimized polynomial, and results are compared to Chebyshev polynomials where higher directivities were obtained without degradation to the array performance. In this study, an example of an eleven element two wavelength array was used to emphasize the possible improvements from using the new techniques. The difficulties facing the realization of superdirectivity in practice have been analysed for the designed arrays. Optimum separation between the array elements was identified for the endfire case. To illustrate some of the results, we show the radiation pattern obtained from using Legendre polynomial compared to the corresponding uniform array case in Fig.(1). Fig.(2) shows a comparison between the directivity obtained from Legendre polynomial and Chebyshev polynomial for eleven element array for various interelement spacings. The variation of directivity with spacing and side lobe level is shown in Figs.(3-4) for various number of elements.