Some highlights in reflector antenna development

Abstract

Reflector antennas have been used since the radio pioneering era of Lodge, Hertz, and Marconi, but it took the exigent demands of radar in World War II to stimulate a real development in the reflector art. Subsequent interest in the science of radio astronomy and the inception of microwave ground communication links were responsible for a burgeoning growth in the field, so that in the 1940s and 1950s the design principles and requirements for prime focus fed systems were well established. Cassegrain, or secondary focus systems, and horn reflectors came into prominence in the early 1960s with the advent of satellite tracking and communication networks. The desire to maximize the gain, or the gain‐temperature ratio, then led to development of sophisticated techniques for properly shaping the illumination over the reflector aperture in order to maximize efficiency and minimize spillover, among them being the shaping of the sub‐reflector in Cassegrain systems and the use of multimode and hybrid mode feed horns. Not all reflector antennas utilize paraboloidal surfaces. Some recent developments in line source feeds make the spherical reflector attractive for scanning applications and the conical reflector for deployable, space‐borne antennas. The large 1000‐foot diameter reflector at Arecibo is a well known example of the former. Although some extremely large spaceborne reflector antennas have been proposed and studied, the largest now in use appears to be the unfurlable 30‐foot reflector carried by ATS‐6. Finally, some gain comparisons are given for a few of the (electrically) largest reflectors that have been built both for radio astronomy and for space communications. If some milestones in reflector development have been overlooked it is due to the limitations inherent in a review paper.

Ultra-directional forward scattering by individual core-shell nanoparticles

“…7,9 and the references therein). Although it has been well known for a long time that the scattering patterns can be more efficiently and flexibly shaped through employing the interferences of electric and magnetic modes 1,2,10 , with outstanding examples such as Kerker's proposal 11 and the concept of Huygens source 12 , it has not attracted much attention since direct magnetic re- to demonstrate various kinds of scattering shaping and control 7,9,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] .…”

Synthesis of line-source feeds for conical reflectors and their performance using dipole arrays

“…1.3. The feed consists of a uniform length of circular waveguide with radiating holes and fin phase correctors [44]. The feed utilizes the radiation principles upon which a line feed constructed for the Arecibo spherical reflector was based [26].…”

Graded metascreens to enable a new degree of nanoscale light management

“…Following simple symmetry restrictions, a single electric interface scatters the impinging wave equally into both directions, and thus it is impossible to independently control the electromagnetic wave distribution on both sides of the interface. The principal consequence of introducing mutual electric and magnetic currents on the surface is to break such scattering symmetry, to some extent analogous to asymmetric radiation from a Huygens antenna [40]. In this context, recently we demonstrated the possibility of breaking the scattering symmetry of a non-magnetic metasurface by using stacked or grounded metasurface configurations [27,34], and efficiently controlling the local transmission or reflection phase at will.…”