Antenna miniaturization beyond the fundamental limits using impedance modulation

Antennas which are physically smaller than their operative wavelength are defined as electrically small antennas. An electrically small antenna characterizes any antenna which fits insides a sphere with radius a =1/k, where k is the wave number of the radiated or received field. Compact-size and wide-frequency bandwidth are in contradiction with lossless antennas. Based on the fundamental limits theory, the minimum radius of a sphere, a, which encloses a lossless antenna, is related to the maximum quality factor of the antenna, Q. This paper presents a novel technique based on impedance modulation to overcome the fundamental limits of antennas.