Showing papers on "Angular aperture published in 1973"
01 Jan 1973
TL;DR: In this article, two methods for determining antenna aperture distributions from the magnitudes (moduli) of radiation patterns are presented, based on the principle of holography, which can be arranged so that all the required information can be obtained without having to make any phase measurements.
Abstract: Two methods are presented for determining antenna aperture distributions from the magnitudes (moduli) of radiation patterns. Antennas under test are measured in the presence of fixed-reference antennas. Invoking the principle of holography, the radiation-pattern measurements are arranged so that all the required information can be obtained without having to make any phase measurements. The methods are illustrated with laboratory experiments, performed with acoustic antennas, for which the aperture distributions are determined to an estimated accuracy of within 5%.
17 citations
TL;DR: In this article, it was shown that two properly-scaled Fresnel zone plates in series constitute a useful coded aperture for imaging X-rays, gamma rays or other incoherent radiation.
12 citations
TL;DR: In this article, it was shown that high quality images can be obtained with Mertz' original encoding method under certain well-defined conditions, under the assumption that the on-axis Fresnel zone plate apertures are fixed.
Abstract: Coded aperture imaging of X ray or y ray emitting objects using on-axis Fresnel zone plate apertures was the original method suggested by Mertz in 1961. Since then other forms of coded aperture imaging have become more popular. We show in this paper that, under certain well-defined conditions, high quality images can be obtained with Mertz' original encoding method.
10 citations
TL;DR: In this paper, the intensity distribution in the Fresnel diffraction pattern of a slit aperture illuminated with partially coherent light is obtained, as a function of the coherence condition across the aperture, by evaluating the formula developed in a previous paper.
7 citations
Patent•
17 Jul 1973
TL;DR: In this paper, a wide angle objective lens system with high aperture ratio and long back focus is presented, in which the sixth and seventh lens elements are cemented at their confronting surfaces to form a doublet and satisfy the following conditions:
Abstract: A wide angle objective lens system of high aperture ratio and long back focus includes eight successively designated lens elements in which the sixth and seventh lens elements are cemented at their confronting surfaces to form a doublet and which satisfies the following conditions:
7 citations
TL;DR: In this article, it was shown that the axial intensity distribution of Fresnel diffraction by the slit aperture is effectively influenced by the coherence condition across the diffracting aperture.
6 citations
Patent•
02 Aug 1973TL;DR: In this paper, a horn antenna suitable for use at microwave frequencies having an exponential amplitude distribution across substantially the entire aperture is composed of three sections, including a section of quarter-wave long dielectric-filled waveguide which matches the waveguide wave number (or propagation constant) to the propagation constant at the aperture required for a damping factor which will yield a desired boresight scale factor at the design wavelength.
Abstract: A horn antenna suitable for use at microwave frequencies having an exponential amplitude distribution across substantially the entire aperture is composed of three sections The first section is a section of quarter-wave long dielectric-filled waveguide which matches the waveguide wave number (or propagation constant) to the propagation constant at the aperture required for a damping factor which will yield a desired boresight scale factor at the design wavelength The second section is also a dielectric-filled waveguide which supports a complex wave including a transverse standing wave in a central dielectric region and damped fields in the two air regions on opposite sides of the dielectric region, and whose propagation constant is the same as that at the aperture The third section terminates at the aperture, and precisely at the aperture, the microwave fields have the characteristics of waves supported by a surface wave structure, the third section transposing the energy so as to consist of a transverse standing wave of very thin finite dimension in the dielectric material near a reference plane, and an exponentially damped wave (or hyperbolic cosine field) progressing from the reference plane, thereby to achieve an exponential aperture distribution across substantially the entire aperture In other embodiments, the sections are combined
3 citations
TL;DR: In this paper, the angular aperture can be varied from ≈ 5.5 × 10−3 −1.5 rad with discrete steps of about 5 × 10 −4 rad, and the K+-Ar potential resulting from this method can be represented by V(r) = 10490 exp [−3.82r], 1.65 A ⊽ r ⩽ 2.39 A.
2 citations
TL;DR: In this paper, the diffraction pattern and frequency response analysis of a half-wave centrally coated lens was used for photography of extended objects when the coating is made on about 0.9 a portion of the lens, where a is the radius of the perfect lens aperture.
Abstract: From the diffraction pattern and frequency response analysis of a half-wave centrally coated lens, it is found that the system will be useful for photography of extended objects when the coating is made on about 0·9 a portion of lens, where a is the radius of the perfect lens aperture.
2 citations
TL;DR: The Fraunhofer integral of scalar wave diffraction theory is used to calculate the far-field onaxis irradiance of the peak far- field irradiance I of the diffraction pattern as a function of x.
Abstract: We consider herein the problem of diffraction of a square uniform beam of light by a circular aperture. The square beam and the round aperture are presumed to be coaxial, i.e., the center of the beam coincides with the center of the aperture and the beam is normally incident upon the aperture plane. The square beam incident upon the aperture plane con tains power P uniformly distributed over the square cross section of the beam. The diagonal dimension of the square is variable and is designated by x. The diameter of the circular aperture is considered to be fixed at value D. We shall consider the following optimization problem: Given a uniform square beam of fixed power P but vari able diagonal x that must be passed through a circular aperture of fixed diameter D, what is the optimum value ofx so as to maximize the on-axis far-field irradiance? We shall now confine our investigation to the calcula tion of the peak far-field irradiance I of the diffraction pattern as a function of x. To calculate the far-field onaxis irradiance, we use the Fraunhofer integral of scalar wave diffraction theory. The far-field on-axis wave am plitude u is given by The aperture field is given by
1 citations