Slotted surface scattering antennas

An antenna, comprising:

• a waveguide;
• a plurality of subwavelength radiative elements coupled to the waveguide;
• and
• a plurality of lumped element circuits directly coupled to the subwavelength radiative elements and configured to adjust radiation characteristics of the subwavelength radiative elements;
• wherein the waveguide includes a bounding surface, and the plurality of subwavelength radiative elements includes a plurality of unit cells each containing a slot in the bounding surface;
• wherein the waveguide defines a propagation direction, and the subwavelength radiative elements have inter-element spacings along the propagation direction that are substantially less than a free-space wavelength corresponding to an operating frequency band of the antenna;
• and
• wherein the inter-element spacings are less than or equal to one-third of the free-space wavelength.