M. Álvarez-Folgueiras

Low-Sidelobe Patterns From Small, Low-Loss Uniformly Fed Linear Arrays Illuminating Parasitic Dipoles

Low-sidelobe radiation patterns with good directivity can be generated by antennas consisting of a linear array of parasitic dipoles in front of a smaller linear array of active dipoles fed uniform voltages, a configuration that facilitates the task of feed network design. The fundamental effect of the parasitic array is to allow the length of the active array to increase by a factor of 2 or more, thereby narrowing beamwidth while the parasitic elements keep side lobes low to ensure good directivity. For a given number of active elements, performance improves as the number of parasitic dipoles increases, levelling off when there are about twice as many parasitic as active elements. The method is easily generalizable to planar arrays.

Low-sidelobe patterns from small, low-loss uniformly fed linear arrays illuminating parasitic dipoles

The complexity of antenna array feed networks can be reduced by reducing the number of radiating elements and having the remainder illuminate an auxiliary array of parasitic elements. The performance of such antennas can be optimized by optimization of their geometry. Here we consider parasitic linear arrays of dipoles illuminated by smaller uniformly fed linear arrays so as to generate low-sidelobe sum patterns with good directivity. The results of a FEKO simulation validating the accuracy of the coupling model are presented, and the influence of the relative numbers of active and parasitic dipoles is discussed.

Analysis of Tolerance Among the Solutions to Shaped-Beam Synthesis Problems

The problem of synthesizing a linear array generating a shaped beam pattern with M filled nulls has 2 M alternative solutions. The sensitivity of the performance to errors in element position, excitation phase or amplitude of the solutions provided by the synthesis of a flat-topped beam pattern using an array of 16 isotropic elements spaced λ/2 was analysed.

Very fast method for synthesizing footprint patterns using very large antenna arrays

The proposed method allows very rapid synthesis of large antenna arrays, affording footprint patterns of satisfactory quality. It is possible to reduce the number of array elements by reducing the number of filled nulls of the modified Elliott-Stern pattern that is sampled at the expense of reducing of the average slope of the pattern (dropoff rate) and a small reduction in the pattern directivity.

Sum and difference pattern with common aperture tail

It has been shown that it is possible to obtain linear Taylor and Bayliss distributions sharing a common aperture distribution in a certain percentage. It is convenient to remark that the larger is the sharing zone, the poorer is the SLLs of the corresponding Bayliss patterns. Nevertheless, the normalized directivity peak and the normalized beamwidth remain a good level independently of the sharing tail size and the n̅B. The method is easily applicable to circular distributions.