A tightly coupled dipole array used for radiation power improvement on finite radiation aperture

Abstract

Radiation power of an electromagnetic wave plays a decisive role in its transmission distance. Traditionally, the radiation power can be improved by expanding the radiation aperture size of the antenna array or increasing input power of the unit cell. However, the radiation aperture size is always restricted by assembly space. The input power improvement of the unit cell is always limited by the signal source. It is difficult to improve radiation power on a finite radiation aperture. However, the radiation power on a finite radiation aperture is related closely to the number of antenna elements and the radiation efficiency of the antenna array. It is useful to arrange more elements and improve radiation efficiency of the antenna array to improve the radiation power on a finite radiation aperture. Wideband wide-angle scanning phased array is able to make full use of a finite radiation aperture. The wide-angle scanning properties make it possible for the radiated power to cover a wide area. In this paper, a compact wideband wide-angle scanning tightly coupled dipole array (TCDA) is proposed. A high permittivity substrate and compact wideband balun are used for miniaturizing the antenna array. The period of the unit cell is only 0.144<i>λ</i>_high × 0.144<i>λ</i>_high (<i>λ</i>_high is the wavelength at the highest operation frequency in free space). Parameters of the balun are optimized to improve impedance matching between the balun and the antenna array. Two bilateral frequency selective surfaces (FSSs) are used to replace traditional dielectric superstrate to improve the impedance matching between the antenna array and free space. A low-loss dielectric substrate is used to reduce dielectric loss of the antenna array. In these ways, the radiation efficiency is greatly improved. The simulation results show that the proposed antenna array operates at 1.7–5.4 GHz (3.2:1) while scanning up to 65° in the E plane, 45° in the H plane and 60° in the D plane with following a rigorous impedance matching criterion (active VSWR < 2). A 16 × 16 prototype array is fabricated and measured. Good agreement is achieved between the simulation results and the measurement results. Compared with the designs in the literature, the proposed antenna array has an excellent performance in radiation power on a finite radiation aperture.