V.S. Panko, Yu.P. Salomatov, A.A. Erokhin

The task of antenna system main lobe scanning can be solved by using a multi-beam antenna array. Scanning is performed by switching between sub-arrays. As was shown previously, such arrays can be built in the form of circle or arc, consisting of log-periodic antennas (LPA) as array element. The LPA length and array configuration can be chosen in such a way that the electric distance between active zones of adjacent LPAs keeps constant while frequency varying. As a result, radiation pattern will demonstrate shape which close to persistent over the entire operating frequency range. In the article choosing of arc array dimensions for frequency range 3-30 MHz is described. It is shown that for angle between array elements 22,5° to achieve a permanent form of radiation pattern required LPA length is about 278 m. It is noted that due to the arc shape of the array, for formation of the main lobe it is necessary to set the different phases of excitation for individual elements of the array. This yields an array model which produces consistent radiation pattern and constant gain figures over frequency range with overlap factor of 10. Radiation patterns for different numbers of array elements are given. Calculation shows that the increase of array elements number will increases the gain, but up to a certain extent.