Weng, Tzu-Hsuan; Lin, Yi-Cheng (Graduation Institute of Commucation Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan)
Log periodic antennas are widely used in EMI/Antenna measurement because of their ultra wideband properties. When designing a planar log -periodic antenna, the feeding method is a main issue. In this paper, a planar log-periodic antenna is fed by a planar Marchand balun. The whole design is illustrated on a PCB without any supporting device. The bandwidth ranges from 1.2GHz to 3.3GHz, with maximum radiation at the broadside. Additionally, shielding striplines are employed in the antenna design to suppress the cross-polarization component with successful results.