Wavefront Converter-Based Antenna for Synchronous Modulation of Radiation and Scattering Characteristics

A low-profile wavefront converter (WFC)-based antenna for synchronous modulation of radiation and scattering characteristics is presented. The WFC located at the near-field region of a microstrip patch antenna, composed of two dielectric substrates sandwiched by three layers of circular ring resonators or their complementary patterns, can effectively concentrate additional radiation energy of the antenna toward the main lobe direction by converting spherical waves to plane waves in the near-field region, thereby enhancing radiation gain and directionality in the far-field region. At the same time, when encountering an incidence plane wave externally for investigating the scattering properties of the considered antenna, the WFC will transform the reflected plane wave into a quasi-ellipsoidal wave, which can achieve a monostatic radar cross-sectional (RCS) reduction in the far-field region by dispersing the scattering energy in all directions. The mechanisms of synchronous modulation of radiation and scattering characteristics are studied by the principle analysis and experimental verification. Numerical and experimental results show that the reference antenna’s gain has been enhanced by 15.7 dBi, while its in-band monostatic RCS has been reduced by more than 10 dB. Moreover, the thickness of the proposed WFC is only $0.077\lambda $ ( $\lambda $ is the free-space wavelength at 11.5 GHz), which has certain advantages in miniaturized applications.