Slot-Loaded Folded Dipole Antenna With Wideband and Unidirectional Performance for L-Band Applications

Wideband antennas operating at L-band are rapidly finding their applications in various microwave-based medical diagnostic systems. To increase signal penetration while working in a limited space, these systems require compact unidirectional antennas. To meet these requirements, a three-dimensional folded dipole antenna is presented. It is composed of a slot-loaded coaxially fed printed slab and a U-shaped copper structure that completes the folded dipole loop. An appropriate slot loading enables achieving significant improvements of the proposed design in terms of bandwidth, gain, and front-to-back ratio compared to the conventional folded dipole antenna. A parametric analysis is performed for a deep understanding of the antenna's mechanism. A fabricated prototype demonstrates 57% fractional bandwidth, centered at 1.44 GHz with an average gain of 3.7 dBi over that band. The antenna has a directional radiation pattern with around 9 dBi front-to-back ratio and -10-dB cross-polarization levels along the boresight direction. The overall volume of the antenna is 0.24 × 0.10 × 0.05 λ
³
, where λ is the wavelength of the lowest operating frequency.