Shortened Log-Periodic Dipole Antenna Using Printed Dual-Band Dipole Elements

In this paper, a compact log-periodic dipole array (LPDA) antenna is developed at 0.5-10 GHz. This LPDA structure constitutes fewer dipole elements than a conventional LPDA antenna that exhibits similar resonant frequencies. In the design of a miniaturized LPDA antenna, various size-reduction techniques have been proposed in the open literature to decrease the lateral size of a conventional LPDA. However, little or no attention has been focused on reducing the size of the LPDA antenna by shortening the boom or axial length. In pursuit of reducing the total length of a conventional LPDA, a dual-band dipole antenna is proposed as the radiating elements for the LPDA antenna in this paper. The proposed dipole structure is a printed half-wave principal dipole loaded with a pair of resistive structures via subfeeding lines. A pair of resistive loads forms the auxiliary (secondary) dipole of the proposed dipole antenna. The structure of the proposed dual-band dipole is achieved without a ground plane as opposed to many existing dual-band antenna types. As a result, the dipole antenna has a simple geometry with omnidirectional characteristics. Also, the feeding structure of this dipole can provide an extra degree of freedom to tune the antenna for matching purposes. A 25-element LPDA antenna is designed with a much reduced boom length compared with existing LPDA structures. To confirm the feasibility of the technique, the experimental results of the proposed LPDA prototype were analyzed and juxtaposed with a benchmark LPDA.