Design and modeling of finite and low-profile, ultra-wideband phased-array antennas

The physical phenomena that determine the bandwidth of wideband connected phased arrays are identified by examining time domain responses of the total voltage or current at the input terminals of a radiator in the array. The paper demonstrates that achieving the widest possible bandwidth from a phased array requires minimization or cancellation of the following: (1) signals traveling into the observation port from neighboring elements, (2) reflections from discontinuities in the geometry of the radiating element, (3) reflections from the edge of a finite connected array, and (4) reflections from the ground plane. 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. The use of high impedance substrates is further demonstrated as a means to obtain ultra widebandwidth when self-complementary radiators are placed above a conducting ground plane. Finally, advanced finite element methods are briefly described for the efficient and accurate analysis of both infinite and finite ultra wideband arrays.