A New Approach for Matching Small Parasitic Superdirective Antennas Using Network Characteristic Modes

This paper presents a network characteristic modes based method for parasitic superdirective arrays matching. The proposed method is used for designing a two M-monopole array with a separation distance of
$d=0.1\lambda$
that achieves a near
$50\ \Omega$
input radiation resistance, resulting in a matched input impedance, and therefore, a substantial increase in realized gain and total efficiency. The designed array shows a maximal directivity of 7.37 dBi and an impedance bandwidth of 23 MHz. The array present a −1 dB bandwidth of directivity, gain and realized gain respectively of 70 MHz, 70 MHz and 31 MHz.