Angular aperture

About: Angular aperture is a research topic. Over the lifetime, 1771 publications have been published within this topic receiving 27257 citations.

Transient Field Calculation of Aperture Antennas for Various Field Distributions Over the Aperture

Abstract: This letter presents a time-domain method of near-field calculation for circular plane apertures of various field distributions. The method allows getting analytic forms presented in inverse trigonometric functions. New formulas for transient near field are derived in this letter for circular plane apertures of electric field falling down to edges of the aperture. The behavior of the transient near field of a circular aperture with distributions tapered toward the edge is explained.

Projection light source and optical system

Abstract: Disclosed is a lamp and reflector system designed to produce maximum energy through an aperture at a pre-determined intensity distribution across an aperture, particularly the film gate aperture of a movie projection system. The invention involves a gaseous discharge lamp having an arc or light source region of varying radiance with the radiance at one electrode substantially higher than the other and a modified eliptical reflector generally axially aligned with respect to the discharge lamp and with the primary focus of the reflector along the axis of the lamp but with the secondary focus at the plane of the aperture on a line forming an angle Delta with the axis of the lamp. Also disclosed is means for determining the optimum mirror or reflector length S in order to produce the maximum energy at a given intensity distribution across the film gate aperture of a projector system. The arc length, radiance distribution, the angle Delta , the mirror or reflector length S and the aperture dimensions are correlated for a reasonable projection f/number in a manner that the image of the brightest portion of the arc is superimposed upon the extremities of the aperture from all points on segment S and the images of the arc at the aperture from various points on the ellipse segment form a family of images with the average size equal to approximately 3/4 of the diagonal dimension. In achieving this type of image, the highest radiance portion of the arc is placed at the first focus of the mirror.

Fresnel Lens at Millimeter-Wave: Enhancement of Efficiency and Radiation Frequency Bandwidth

Abstract: In this paper, the performance of Fresnel lens antennas is investigated in detail. The performance is evaluated in terms of aperture efficiency and stable radiation pattern over a wide frequency band. This paper proposes an efficient technique for enhancing aperture efficiency by smoothly compensating for the spherical phase front arriving upon the lens surface. The feeder has been optimized to fit an axially symmetric cos n -like radiation pattern. For this, an accurate technological process has been used to manufacture a lens that allows for smooth compensation of the phase shift. The lens is compared with a classic Fresnel lens having the same physical dimensions and feeding system. The improvement is validated by measurement, which has revealed a maximum measured gain of 38.9 dBi corresponding to a maximum measured aperture efficiency of 59% with a −2 dB radiation frequency bandwidth of 29.25 GHz around 90 GHz. This amounts to an aperture efficiency enhancement of 60% and −2 dB radiation frequency bandwidth enhancement of 72% as compared with those of the classic Fresnel lens.

Objective lens having a doublet lens with high numerical aperture

Abstract: An objective lens having a doublet structure and a number of apertures of 0.7 or more and an optical pickup apparatus having the objective lens to be adaptable to a optical recording medium having a high information recording density, the objective lens being structured such that at least one side is formed into a aspheric surface and the lens elements are made of low-diffusion glass having an Abbe's number of 40 or greater.

Analysis and closed-form solutions of circular and rectangular apertures in the transverse plane of a circular waveguide

Abstract: An analysis is carried out to determine the discontinuity susceptance of a circular or rectangular aperture in the transverse plane of a circular waveguide. Closed-form solutions based on the scattered amplitude calculations and aperture coupling theory are derived. Example solutions for a small circular aperture and a resonant rectangular aperture are given. The calculated results agree very well with the experiments. The results have many applications in the design of circular waveguide components and circular waveguide-backed aperture antennas. >