US Patent 11183760 Active Vivaldi antenna

An antenna system having a Vivaldi antenna configured to be impedance matched to antenna impedance Za at and above but not below a frequency fc; a Field-Effect-Transistor buffer coupled to the Vivaldi antenna, the length of the coupling between the antenna terminals and the buffer being of a distance much less than a wavelength at frequency fc, the buffer configured to present a high impedance at frequencies substantially <fc, the buffer output impedance further configured to be matched to a system impedance Z0 at frequencies both above and below fc.