Vertically Stacked Binomial-arrays of Resonant Dipoles for Mobile Wireless Communication and Scavenging Applications

The system under investigation consists of three-and four-element binomial arrays of half-wave resonant dipoles, stacked vertically on each of three equilateral triangular cross-sections of a ground plane, and employed in mobile cellular communications base stations. In practical terms, the dipoles being center-fed and carrying equal in-phase currents are arranged with a specified spacing of dipoles from the ground plane so as to generate the overlapping patterns required. Using Pascal's triangle concepts, it is shown that when the normalized excitation coefficients for the three-and four-element binomial arrays are 1, 2, 1 and 1, 3, 3, 1, respectively, the corresponding respective array factors emerge as: $(AF)_{3}=2\cos^{2}(0.5kd_{e}\cos\theta)$ and $(AF)_{4}=4\cos^{3}(0.5kd_{e}\cos\theta)$. With a resonant half-wave dipole as candidate for investigation, results of several computations of the array factor and radiated electric field patterns, displayed in graphical formats, reveal that the sidelobes occurrence associated with binomial array when the inter-element separation is greater than $0.5\lambda$ can be reduced if the length of each radiating elements of the array is increased to $1\lambda$. Because this choice of element length attracts increased directivity of the array, it is particularly suitable for use with RF energy scavenging applications. It seems desirable to perhaps add that this investigation derives impetus, as suggested in the presentation, from the prevalence of the ubiquitous contemporary surroundings for cellular communications mobile phones signals whose propagation in and out of constructed dwellings, provide preponderance reserve for energy scavenging possibilities.