An antenna , comprising: a wave-propagating structure ; and a plurality of scattering elements distributed along the wave-propagating structure with inter-element spacings substantially less than a free-space wavelength corresponding to an operating frequency of the antenna, where the plurality of scattering elements have a plurality of adjustable individual electromagnetic responses to a guided wave mode that propagates within the wave-propagating structure and the plurality of adjustable individual electromagnetic responses provide an adjustable radiation field of the antenna; wherein the wave-propagating structure includes one or more one-dimensional wave-propagating structures, one or more conducting surfaces and the plurality of scattering elements corresponding to a plurality of apertures within the respective one or more conducting surfaces wherein the one or more one-dimensional wave-propagating structures include one or more closed waveguides and wherein the one or more conducting surfaces are one or more respective upper surfaces of the one or more closed waveguides; and wherein the plurality of apertures defines a respective plurality of conducting islands that are electrically disconnected from the respective one or more conducting surfaces , and the antenna further comprises: a plurality of bias voltage lines configured to provide respective bias voltages between the respective one or more conducting surfaces and the respective plurality of conducting islands; and an electrically adjustable material disposed at least partially within respective vicinities of the plurality of apertures . a wave-propagating structure ; and a plurality of scattering elements distributed along the wave-propagating structure with inter-element spacings substantially less than a free-space wavelength corresponding to an operating frequency of the antenna, where the plurality of scattering elements have a plurality of adjustable individual electromagnetic responses to a guided wave mode that propagates within the wave-propagating structure and the plurality of adjustable individual electromagnetic responses provide an adjustable radiation field of the antenna; wherein the wave-propagating structure includes one or more one-dimensional wave-propagating structures, one or more conducting surfaces and the plurality of scattering elements corresponding to a plurality of apertures within the respective one or more conducting surfaces wherein the one or more one-dimensional wave-propagating structures include one or more closed waveguides and wherein the one or more conducting surfaces are one or more respective upper surfaces of the one or more closed waveguides; and wherein the plurality of apertures defines a respective plurality of conducting islands that are electrically disconnected from the respective one or more conducting surfaces , and the antenna further comprises: a plurality of bias voltage lines configured to provide respective bias voltages between the respective one or more conducting surfaces and the respective plurality of conducting islands; and an electrically adjustable material disposed at least partially within respective vicinities of the plurality of apertures . a plurality of bias voltage lines configured to provide respective bias voltages between the respective one or more conducting surfaces and the respective plurality of conducting islands; and an electrically adjustable material disposed at least partially within respective vicinities of the plurality of apertures . <EOS>