Empirical approximations to the current values for large Dolph-Tchebyscheff arrays

The demand for radar antennas exhibiting a narrow beam and low side-lobes has led to the development of the so called Dolph-Tchebyscheff array which optimizes the relationship between beamwidth and side-lobe level. Unfortunately, however, the calculation of the excitation coefficients for the Tchebyscheff array is quite time consuming and tedious for arrays with a large number of elements. The present paper describes a simple approximate method for calculating long Tchebyscheff arrays which cuts the calculating time by 95 per cent for a 40 element array and which does not increase in complexity with the number of elements in the array. Furthermore, sample calculations indicate errors of only 3 or 4 per cent in the excitation coefficients which is tolerable for most practical arrays. In addition, the paper contains a table of all the coefficients for Tchebyscheff arrays computed in the course of antenna development at the Hughes Aircraft Company. The table contains the exact excitation coefficients and the gain values relative to the corresponding uniform array.