Compact quasi-Yagi antenna with folded dipole fed by tapered integrated balun

Planar quasi-Yagi antennas including a printed balun are designed and experimentally characterised. The parasitic array driver is a folded dipole connected to a parallel stripline. The unbalanced to balanced transition between the input microstrip and the folded dipole terminals is obtained by linearly tapering both the microstrip and the ground plane widths. These printed antennas are more compact and directive than their counterparts based on resonant half-wavelength dipole drivers: indeed, in the presence of one director, the size of the board is about 0.4 lambda X 0.5 lambda and the measured gain is 7 dB.