A Wideband Stacked Magnetic Dipole Antenna With High Aperture Efficiency

This article presents a novel stacked magnetic dipole antenna with wide impedance bandwidth, directional radiation pattern, low cross-polarization, and low back radiation. The proposed antenna consists of a rectangular loop and a radiating aperture to produce two equivalent magnetic dipole radiations in a stacking reconfiguration. By carefully designing the separation of the two magnetic dipoles, a directive and broadside radiation pattern can be achieved when the phase difference between the two magnetic dipoles is nearly 90°. From the obtained result, the antenna has a stable gain and high polarization purity, which is contributed by the stacked radiating sources and the vertical pins of the rectangular loop. The antenna element covers a wide impedance bandwidth of 42% ranging from 28.2 to 43.1 GHz (for the reflection coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\le 10$ </tex-math></inline-formula> dB) with stable pattern, high aperture efficiency, low cross-polarization, and low back lobe. In order to demonstrate the flexibility in building up an array from the proposed stacked magnetic dipole element, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times 8$ </tex-math></inline-formula> antenna array is further investigated and designed. It covers a bandwidth from 29.6 to 40.1 GHz with a peak gain of 27 dBi, and the aperture efficiency reaches up to 97% at 30 GHz. These new antenna elements and their array find potential applications in millimeter-wave (mmW) systems of communications, sensing, and imaging.