Mututal coupling effects on characteristics of turnstile spherical array antenna

The spherical array antenna considered here can scan its beam to a large angle. A theoretical method is outlined for obtaining the self- and mutual impedances of dipole antennas over a conducting sphere. The numerical results obtained are verified experimentally. The resonant length of the dipole antenna over a conducting sphere is determined using this method. The active impedance distribution and its scanning characteristics are discussed, with an allowance made for mutual coupling in the turnstile spherical array antenna. Mismatching of the impedance is shown to be very small at feeding points. The analysis also considers the effects of mutual coupling on the scanning characteristics of the power gain and the axial ratio of the polarization. It is found that, from the standpoint of the feeding system, the turnstile spherical array antenna is suitable for wide scanning.