Printed quasi-Yagi antenna with folded dipole driver

Abstract

Printed quasi-Yagi antennas [1] have been used in a number of applications requiring broad-band planar end-fire antennas. So far they have been mostly realized on high dielectric constant substrates with moderate thickness in order to excite the TE 0 surface wave along the dielectric substrate. An alternative design of a printed Yagi-Uda antenna, developed on a low dielectric constant material, was presented in [2]. In this design, an additional director and a reflector were used to increase the gain of the antenna. However the achieved bandwidth of the antenna is quite narrow (about 3–4%) compared to the bandwidth of a quasi-Yagi antenna fabricated on a high dielectric constant substrate [1]. Another disadvantage of a conventional quasi-Yagi antenna fabricated on a low dielectric permittivity substrate is that the length of the driver is increased and it is difficult to achieve 0.5 λ 0 spacing between the elements required for scanning arrays, where λ 0 corresponds to a free-space wavelength at the center frequency of the antenna.