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Compact planar Yagi-Uda antenna with improved characteristics

In this paper, two different designs of 3-element planar Yagi-Uda antenna based on the shape of driven and reflector elements are studied. To feed the driven element of Yagi-Uda antenna, a tapered microstrip balun is designed, which converts unbalanced coaxial feed to balanced microstrip line feed. Measured results of both the antennas are compared and it is shown that a planar Yagi-Uda antenna using tapered shaped dipole elements is more compact and has better characteristics in terms of bandwidth, front to back ratio and gain than that using normal rectangular shaped dipoles. For Yagi-Uda antenna using tapered dipoles, measured bandwidth is 18.6% for return loss less than 10 dB. Maximum gain is 6.4 dBi with less than 1 dB variation over the bandwidth. Measurement shows a peak front to back ratio of 30 dB.