High-directivity, compact, omnidirectional horizontally polarized antenna array

Omnidirectional horizontally polarized (OHP) 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 OHP 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) OHP array is only 0.07 × 0.22 × 3.3 λ03 (0.07 × 0.22 × 4.3 λ03) 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 HP sources covering the entire azimuthal plane.