A Microstrip Magnetic Dipole Yagi–Uda Antenna Employing Vertical I-Shaped Resonators as Parasitic Elements

A low-profile planar Yagi–Uda antenna with exact endfire radiation and vertical polarization is presented in this paper. The concept is the combination of an aperture element and a novel vertical I-shaped resonator (VISR). The aperture acts as the driven antenna, which can be equivalent of a virtual magnetic dipole. The VISR array constructed with VISR unit cell is employed as a director or a reflector element depending on the resonant frequency of the unit cell, which consists of two identical rectangular metal conductors printed on both sides of a substrate and their electrical connection using via holes. Two prototype antennas are then designed, fabricated, and measured to test the validity of the operating principle. Antenna I with one director and one reflector achieves an endfire realized gain of 9.9–10.3 dBi and a front-to-back ratio (FBR) of more than 17.4 dB across 6.36–6.70 GHz. With four directors and one reflector, an endfire realized gain of 12.9–13.6 dBi and an FBR of more than 17.9 dB are accomplished by antenna II across 6.38–6.71 GHz. Moreover, a sensitivity analysis is implemented for the proposed antennas. Simulated results show that the standard PCB process is a reliable method for antenna fabrication.