Abstract-A miniaturized printed log-periodic fractal dipole antenna is proposed. Tree fractal structure is introduced in an antenna design and evolves the traditional Euclidean log-periodic dipole array into the log-periodic second-iteration tree-dipole array (LPT 2 DA) for the first time. Main parameters and characteristics of the proposed antenna are discussed. A fabricated proof-of-concept prototype of the proposed antenna is etched on a FR4 substrate with a relative permittivity of 4.4 and volume of 490 mm × 245 mm × 1.5 mm. The impedance bandwidth (measured VSWR < 2) of the fabricated antenna with approximate 40% reduction of traditional log-periodic dipole antenna is from 0.37 to 3.55 GHz with a ratio of about 9.59 : 1. Both numerical and experimental results show that the proposed antenna has stable directional radiation patterns and apparently miniaturized effect, which are suitable for various ultra-wideband applications.

The log-periodical antenna (LPDA) is a kind of ultraw wide-band antennas. To achieve the purpose of miniaturization of the LPDA in radiate direction, this paper presents a novel structure log-periodically loaded with symmetrical meandering dipoles. The radiate direction is reduced to 46% of the conventional LDPA. The return loss is less than -10dB from 200MHz to 2GHz, according to the simulation results. A good directivity is also obtained that the gain ranges from 1.9dB to 7.2dB.