Radiation Characteristics of a Slot Antenna With Two Parasitically Excited Wires

The formulation and validation of the radiation characteristics of a slot antenna with two parasitically excited wires (SCPW) is presented in this letter. First, the coupled currents at the driving point of wires are derived. Then, the far-fields of a slot antenna and two wires excited with same amplitude but out of phase are derived under the commonly assumed electrically thin condition for the slot and wires, respectively. The antenna’s overall radiation field is then obtained by combining these components and the directivity is deduced. Next, the amplitude and the phase of the far-field of the wires are calculated and analyzed to obtain a cancelation to the far-field of the slot antenna. Finally, the slot antenna coupled with two parasitically excited monopoles (SCPM) achieves uniform radiation patterns in both E- and H-planes. A slot antenna coupled with two parasitically excited inverted-Ls (SCPI) broadens the radiation pattern in both principal planes, resulting in a half-power beamwidth of 90° in the H-plane and 88° in the E-plane. Furthermore, the interelement mutual coupling in the E-plane achieved around 6 dB reduction for SCPW elements compared to using a slot alone. For verification, the prototypes of SCPM, SCPI, and their 1 × 2 arrays were simulated, fabricated, and measured. Acceptable agreements among the calculated, simulated and measured results are achieved.