Compact planar log-periodic dipole array based yagi-uda antenna

In this paper, a compact planar Yagi-Uda antenna based on two elements log-periodic dipole array has been designed to achieve an end fire directional characteristics over a broad range of frequencies. To feed the driven elements of log-periodic dipole array, a tapered microstrip balun is designed, which converts unbalanced coaxial feed to balanced microstrip line feed. The prototype of antenna has been fabricated on a low cost glass epoxy FR4 substrate with overall size of the antenna is 0.41λ
_o
× 0.54λ
_o
at center frequency (84mm × 111mm). The measured results have been compared with simulated results. Measured results show a bandwidth of approximately 41.4% centered at 1.45 GHz for VSWR <; 2. Maximum gain is 7.2 dBi with nearly 1 dB variations over the bandwidth. Peak front to back ratio is 28 dB with better than 15 dB has been achieved over the bandwidth.