Design of two-stacked circular loop Yagi-Uda array antenna

A broadband multiple element Yagi-Uda two-stacked circular loop antenna is proposed in which two circular loop antennas with a high gain and a broadband are stacked in the broadside direction. In the two-stacked structure, circular dual-loop antennas are used in which the loops are connected with a parallel twin wire only for projector and are fed at the center. The antennas are analyzed numerically by setting equivalent antennas consisting of the loops and the parallel twin wire. Detailed design data for each parameter are obtained. The effect of the stack spacing of the loops on the radiation characteristics is significant. An optimum value is obtained at Dij = 0.45 - 0.60 λ. It is shown that the impedance loss can be compensated by the stab method. Also, an example of the design of a high gain antenna based on the design data is presented. The validity of the design procedure is confirmed experimentally. With an eight-element array, a sharp beam is obtained with an H-plane half-power angle of about 30 degrees. The maximum actual gain is 11 dB, and the 3-dB bandwidth is about 270 MHz. This high gain and broadband antenna is an improvement of the actual gain by more than 4 dB in comparison with a dipole array with the same dimensions. At present, this antenna is in the class of broadband antennas with the maximum gain.