Abstract: The angular accuracy of target signal is affected by the near-field effect in the radio frequency composite array. This paper presents a new method to solve the problem. The radiation electric field distribution of a three-element sub-array located on the spherical composite antenna arrays at the receiving antenna location, which is usually located in the radiating near-field region, is precisely calculated by an hybrid technique of the full-wave algorithm and uniform geometrical theory of diffraction (UTD), in the case of the three-element array surrounded with its nearby elements working at same and different frequencies. The equivalent phase center of the three-element array is then obtained by the phase gradient algorithm (PGA) based on its phase distribution. The deviation of the equivalent phase center with that derives from the amplitude gravity center equation is calculated, which is used to find the corrected input power for each element antenna of the three-element array. The simulation results for a real composite antenna array system show that the maximum angular accuracy of pitching direction is corrected from 1.50/2.37 milliradian to 0.06/0.06 milliradian on the microwave three-element antenna and millimeter wave three-element antenna.

Key words: three-element array of antenna, near-field effect, composite array, equivalent phase center