High-Directivity, Compact, Omnidirectional Horizontally Polarized Antenna Array

Abstract

Omnidirectional horizontally polarized (OTIP) X-band magnetic dipole (MD) antenna arrays are reported that simultaneously achieve high directivity and wide bandwidth while being compact in size. A major innovation is the seamless integration of several phase inverters into an electrically long TE0.5,0 mode open waveguide. The resulting open structure radiates as a collinear series of MD sections. The inverters facilitate the realization of in-phase electric fields along its entire length and, hence, phase coherence between all of these MDs. Each phase inverter is realized as a combination of a meandering slot on one metallic surface of the waveguide and several shorting vias surrounding it. Two such multistaged (six- and eight-element) collinear OTIP MD arrays were designed and optimized. Prototypes of both were fabricated with standard, low-cost PCB manufacturing technology. The volume of the six-element (eight-element) OTIP array is only 0.07 × 0.22 × 3.3 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (0.07 × 0.22 × 4.3 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ); it achieves a measured 8.2 dBi (10.4 dBi) peak realized gain (RG). The measured overlapping -10 dB impedance bandwidth and 3 dB RG bandwidth was 8% in both cases. These designs are ideal for wireless applications requiring thin high-directivity TIP sources covering the entire azimuthal plane.