Wide beamwidth planar self-balanced magnetic dipole antenna with enhanced front-to-back ratio

A design approach to a novel planar self-balanced, wide beamwidth magnetic dipole antenna with high front-to-back ratio (FBR) is advanced. The principle for FBR enhancement is revealed at first. As seen, the back-lobe level can be effectively suppressed by adjusting the unbalanced current ratio (UCR) factor: By varying the radius of the circular sector magnetic dipole antenna on the bottom layer and incorporating an arc-shaped branch at the end of the parasitic strip, the UCR factor can be properly tuned, and the back-lobe level can be flexibly controlled. Then, a set of closed-form formulas is derived to provide basic design guidelines and determine the initial value of key parameters. Parametric studies on FBR are then carried out to attain the ultimate designs in a step-by-step manner. As numerically and experimentally verified at the 2.45-GHz band, the FBR of a planar, air-substrate magnetic dipole antenna is indeed increased to over 30 dB with broadened E-/H-plane half-power beamwidth up to 130 degrees/90 degrees. Good agreement between the theoretical, numerical, and experimental results has evidently validated the proposed antenna design approach.