Design of a Broadband Coupled-Fed Printed Dipole Antenna as an Array Element for Direction Finding Systems

This article proposes the design of a coupled-fed printed dipole antenna for direction finding (DF) systems. The antenna consists of a radiating 50 degrees angled expanded-arm printed dipole as well as a fan-shaped feeder that is located on the opposite side of the radiating dipole. The 50 degrees angled expanded-arm structure results in a wide beam-width and broadband-matching characteristics. The more the arm angle is bent, the wider the beam-width pattern. Note that the expanded structure to the side of the dipole arm allows the wide beam-width of the radiation pattern. The printed dipole is then electromagnetically coupled with the fan-shaped feeder to obtain broadband-matching characteristics. To obtain additional broadband-matching characteristics, the circular cavity and the four-step tapered structures of the radiating printed dipole are carefully tuned by considering the coupled fields induced by the indirect feeding structure. The reflection coefficients are -14.6 dB and -11.9 dB at 1.575 GHz and 2.4 GHz, and the boresight gains are 4.8 dBi and 1 dBi, respectively. To confirm the DF capability of the proposed antenna, the pattern of the 4x4 arrays is observed by varying the steering angle.