A Super-directive Two-Element Parasitic Dipole Antenna

This paper describes a method to achieve superdirectivity in dipole array by employing only two elements, a driven element and a shorted parasitic element. To maximize the directivity, initially the array is assumed to be fully driven and the required current excitation coefficients are calculated. Then the parasitic elements are added such that the parasitic array achieves almost the same directivity as the fully driven array when optimal loads (inductive, capacitive, short) are connected to the parasitic element. It is observed that a shorted parasitic element placed very near to the driven element could enhance the directivity to a high value. The directivity can be further enhanced by placing the elements on a trapezoidal shaped substrate. A two element parasitic dipole antenna array with a directivity of 9.17 dBi is presented.