Equally Spaced Spherical Arrays

Abstract : The report presents a new method of analyzing the radiation characteristics of a spherical array. The existing method of finding the characteristics of an array on a curved surface using computers does not provide a means of predicting the sidelobe level and beamwidth of the pattern. In this report, the theory of unequally spaced arrays developed by Ishimaru is applied to this problem and the radiation characteristic is found to behave as sin(u)/u. The elements of the array are arranged as a series of circular arrays of different radii on the spherical surface. The resulting radiation pattern for constant amplitude and element spacing of one wave length is discussed in detail. The validity of the theory is demonstrated by an experimental spherical array which employs half-wavelength dipole elements on an Eccoform sphere. Due to the difficulty of exciting each element of the array a plane wave is used to excite the array. Scattered wave is measured and compared with the theory. (Author)