Self-complementary radiators for enabling ultra-wideband phased arrays

To obtain ultra-wide bandwidth from antenna apertures, a design goal is to eliminate or minimize the following: (1) signals traveling into observation ports from neighboring elements, (2) reflections from discontinuities in the geometry of the radiating element, (3) reflections from the boundary edges of finite arrays, and (4) reflections from a ground plane (if present). An investigation of currents on various connected arrays demonstrates that shaping the radiating element to minimize reflections from the end of the array and interactions with neighboring sources is an important first step toward wideband phased array designs. Of particular interest are self-complementary radiators which are shown through transient analysis to completely satisfy (1) and (2) when the radiators are infinite in extent and in free space. The use of high impedance substrates is further discussed as a means to obtain ultra wide bandwidth when self-complementary radiators are placed above a conducting ground plane. This design approach gives rise to a conceptually simple material stackup.