Showing papers on "Fresnel zone antenna published in 1987"
Patent•
27 May 1987
TL;DR: In this article, the phase difference between the signal from the reference antenna and the signals from the other antennas is used to determine the direction of the signal in a radio direction finding system.
Abstract: Radio direction finding equipment has an array of direction finding antennas. The antennas are connected to receivers and signals from the antennas are processed, for example with a microcomputer, to give direction information derived from the phase difference between the signals. A reference antenna is also provided and this is of greater sensitivity than the other antennas. The direction information is derived from phase differences determined between the signal from the reference antenna and the signals from the other antennas.
20 citations
15 Jun 1987
13 citations
01 Jun 1987
TL;DR: Two types of compact mobile antennas for a multi-beam satellite communication system are described, one of them is conically shaped beam antennas and the other is an electronically controlled beam-steerable antenna with a simple tracking system.
Abstract: This paper describes two types of compact mobile antennas for a multi-beam satellite communication system. One of them is conically shaped beam antennas. Quadrifilar helix and microstrip antenna are discussed, and they can be extremely simple and inexpensive antennas, although their beamwidths are narrow. The other one is an electronically controlled beam-steerable antenna with a simple tracking system. This antenna is applicable as a mobile antenna to cover a wide elevation angle.
10 citations
15 Jun 1987
9 citations
TL;DR: In this article, a method of calculating the radial intensity distribution of the Fresnel diffraction pattern of a circular aperture is presented. But this method can also be applied to calculations of more complicated apertures.
Abstract: The author presents a method of calculating the radial intensity distribution of the Fresnel diffraction pattern of a circular aperture. The method uses the concept of counting whole or partial Fresnel zones and has an accuracy of about five per cent of the maximum intensity, although it can be refined to improve this figure somewhat. The method can also be applied to calculations of the Fresnel diffraction patterns of more complicated apertures.
8 citations
TL;DR: Using the Hopkins algorithm, expressions for the intensity patterns, in both the Fresnel and far-field regions, associated with the diffraction of a plane-wave elliptical Gaussian beam truncated by an elliptical aperture were derived in this paper.
Abstract: Using the Hopkins algorithm, expressions are derived for the intensity patterns, in both the Fresnel and far-field regions, associated with the diffraction of a plane-wave elliptical Gaussian beam truncated by an elliptical aperture This is accomplished by evaluating the diffraction integral subject to the Fresnel approximation Numerical results are presented that indicate how the truncation parameter affects the side-lobe level in the Fresnel and far-field regions
7 citations
01 Apr 1987
TL;DR: In this paper, the authors present an overview of the current multi-beam and contoured-beam antenna technology and the limitations of the offset reflector with respect to beam scanning and cross polarization.
Abstract: : High-gain spacecraft antennas with multiple beams and contoured beams are key components in satellite communications and direct broadcast systems. This is reflected on the latest generation of communications satellites, where the antenna subsystem is the largest subsystem with its weight of more than 300 kg. The antennas achieve a large communications capacity through multiple frequency re-uses and may be reconfigured to serve different coverage areas. The paper overviews the current multi-beam and contoured-beam antenna technology. Different implementations, reflector or lens with feed array or direct radiating array, are considered. The emphasis is placed upon systems with offset paraboloidial reflectors. The limitations of the offset reflector with respect to beam scanning and cross polarization are reviewed. computer-aided design procedures and design examples are presented.
6 citations
15 Jun 1987
TL;DR: In this paper, the Fourier transform relationship between the far-field pattern and a function related to the indud current is exploited to localize the distortion with the aid of an FFT algorithm.
Abstract: Among the many different diagnostic techniques, microwave holography has been s~~ccessfully applied in recent years [l-31. In this technique, the far-field amplitude and phase are measured and then the Fourier transform relationship which exists between the far-field pattern and a function related to the indud current is exploited to localize the distortion with the aid of an FFT algorithm. Up to now the technique has been applied to far-field data either measured in the far field or construded from planar near-field measurements.
5 citations
15 Jun 1987
TL;DR: In this paper, a monostatic millimeter-wave radar Ntenna by integrating transmit, receive, phase shift, control and other functions into a single monolithic integrated circuit, and then assembling them in large numbers with antenna elements to form electronically-controlled phased arrays, leads to such a large concentration of heat generating components in such a small volume that cooling the assembly for safe reliable operation appears to be impossible if the transmit power exceeds some modest limit.
Abstract: Building a monostatic millimeter-wave radar ntenna by integrating transmit, receive, phase shift, control and other functions into a single monolithic integrated circuit, and then assembling them in large numbers with antenna elements to form electronically-controlled phased arrays, leads to such a large concentration of heat generating components in such a small volume that cooling the assembly for safe reliable operation appears to be impossible if the transmit power exceeds some modest limit.
2 citations
01 Jan 1987
TL;DR: In this article, an analytical description of the far-field pattern has been developed for a new type of flat lens, which is used as a quasi-optical focusing or frequency-filtering element at frequencies from 35 to 210 GHz.
Abstract: Characteristics are given for Fresnel zone plates used as quasi-optical focusing or frequency-filtering elements at frequencies from 35 to 210 GHz. An analytical description of the far-field pattern has been developed. Design data, measured results are given for a new type of flat lens.
1 citations
Patent•
07 May 1987
TL;DR: In this paper, a passive infrared receiver has a Fresnel lens system which focuses the body radiation emerging from a moving person and has a lens film which is curved in the form of a radius and arranged such that the focuses of all the Fresnel lenses coincide at a common focus at which the infrared detector is arranged.
Abstract: A passive infrared receiver having a Fresnel lens system which focuses the body radiation emerging from a moving person and has a Fresnel lens film (11) which is curved in the form of a radius and is arranged such that the focuses of all the Fresnel lenses coincide at a common focus at which the infrared detector (10) is arranged. In order to create an arrangement which is space-saving and simple in terms of production engineering and operation for the optical or optoelectronic system of the infrared receiver, a focusing device (12) is arranged on the side of the circuit carrier board (6) which is fitted with components, which focusing device (12) defines the curvature of the Fresnel lens film (11), can be assembled with the circuit carrier board (6) to form a structural unit, and carries the Fresnel lens film (11) and a second circuit carrier board (9) with the infrared detector (10).
15 Jun 1987
TL;DR: The design of a hybrid C-band and K-band communications system for use in space has been described in this article, which was designed to require minimum satellite surface without using deployable components but still providing maximum gain, cross polarization isolation, suitable pattern coverage and high reliability.
Abstract: The design of a hybrid C-band and K-band communications system for use in space has been described. The .systems were designed to require minimum satellite surface without using deployable components but still providing maximum gain, cross polarization isolation, suitable pattern coverage and high reliability. The antenna systems have been successfully launched by space shuttle and the ARIANE rocket. Expectation for continued use is high.
15 Jun 1987
15 Jun 1987
TL;DR: In this paper, the authors evaluate the focal region of dual-reflector antennas and derive the excitation CXP efficients of the array feed by conjugate matching, which is then used to determine the array characteristics.
Abstract: A. Introduction. In low-sidelobe beam scanning applications of reflector antennas an array of feeds is normally enployed as the excitation source. The fundamental design problem is then to determine the array characteristics which corresponds t o a p r e scribed radiation pttern. This papr addresses this problan through the evaluation of the focal region f ie lds of dual-reflector antennas fran which, by conjugate matching, the excitation CXP efficients of the array feed are abtained.
15 Jun 1987