Reflector (antenna)

About: Reflector (antenna) is a research topic. Over the lifetime, 28730 publications have been published within this topic receiving 212618 citations.

Calculation of Doubly Curved Reflectors for Shaped Beams

Abstract: A method based upon conservation of energy and the simple laws of geometrical optics is described for the calculation of double-curvature surfaces to produce from a point source a shaped beam of arbitrary shape in one plane and uniformly narrow in the perpendicular planes. A specific application of the shaped-beam antenna is in connection with radar antennas for airborne navigational systems, for which the optimum elevation pattern is found empirically to be G(0) = Kcsc20 cos 0. A reflector to produce from a given primary source the required pattern is the envelope of a family of paraboloids determined by a central-section curve which is adjusted to give the necessary distribution of energy for the shaped beam. A test for the single-valuedness of a computed surface is described. Patterns are shown for experimental antennas whose reflectors were computed by this method. It is demonstrated that some control of the antenna pattern can be achieved by proper motion of the antenna feed. A discussion of errors is included in an Appendix.

Enhanced EBG Resonator Antenna as Feed of a Reflector Antenna in the Ka Band

Abstract: Recent studies have shown that a multibeam reflector antenna could be illuminated by a multifeed electromagnetic bandgap (EBG) structure, in order to achieve a high gain multispot coverage with the simple "one feed by beam" concept and only one aperture. This letter deals with the design of a metallic EBG antenna in the Ka band, feeding a side-fed offset cassegrain antenna (SFOCA) for a European multispot coverage. This reflector presents a high focal-length-to-diameter ratio limiting the defocusing effects for multibeam applications. It, therefore, requires focal feeds with a high directivity and a good radiation pattern quality. The well-known drawbacks of an EBG antenna are the narrow radiation bandwidth for high directivities and also the high sidelobes level reducing the reflector antenna efficiency. Consequently, the work presented in this letter consisted in improving the EBG antenna performances by using a more efficient feed. The replacement of the usual microstrip patch by a horn allowed to double the radiation bandwidth while decreasing the sidelobes level (-15 dB) of a 24-dB EBG antenna. A metallic prototype excited by a single horn has been manufactured at 30 GHz, and the measurements agree with the simulation. This device with one feed allows good SFOCA performances, similar to those obtained with a conventional focal feed like a Potter horn.

Optical transform system

Abstract: Method and apparatus for generating compound shapes in optical surfaces needed to accomodate variable magnification, off-axis projection, reflection from diverse surfaces, reflector relay, intensity pattern requirements and other complex optical transform functions. The present invention permits the realization of mirrors of which provide a variable magnification. The surface generation capabilities permit controlled magnification changes that nevertheless are still image forming and typically avoid the human eye focussing difficulties normally associated with variable magnification mirrors. The present invention includes a computer driven, reflector design system which permits the designer to see the field of view, ray tracings, reflected beam intensity pattern and other data pertinent to a variable magnification mirror from entered mirror specifications. The effect of changes in specifications can be rapidly determined and a final design achieved through one or more such reiterations. The system further determines machine tool motional controls for grinding a surface corresponding to the entered mirror specifications. The capability of the invention in producing irregular optical shapes for these applications is utilized for the production of mirrors that accomplish complex focussing functions for use in off-axis projection mirrors, relay mirrors, and headlamp reflector mirrors. According to the invention, optical systems capable of accomplishing such complex focussing can be realized with a single reflector.

Solar tracking concentrator

Abstract: A solar tracking point concentrator for a solar energy system comprises a light weight reflector in the shape of a paraboloid dish having a rim angle of approximately 109°, whereby the center of gravity of the reflector mass is coincident with the focal point of the paraboloid. The reflector is supported on a light weight pipe pedestal assembly and controllably driven by a light weight control-drive means so as to be angularly adjustable in both elevation and azimuth to track the sun and efficiently continuously reflect the sun's rays to a heat receiver disposed at the focal point of the paraboloid preferably in a fixed position. The reflector is mounted for controlled movement to effect such angular adjustments about horizontal and vertical axes which intersect at the focal point of the reflector paraboloid. The 109° paraboloid rim angle provides a paraboloid reflector that inherently has its center of gravity essentially coincident with its focal point. This arrangement provides an essentially balanced mounting of the paraboloid reflector without requiring counterbalancing means. Therefore, the paraboloid reflector may be supported by a light weight pipe pedestal assembly and driven by light weight control-drive means, such as linear stepping motors which are controlled by electronic pulses generated by light weight microprocessors.