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Showing papers on "Reflective array antenna published in 1977"


Journal ArticleDOI
TL;DR: In this paper, a two-layer stripline log-periodic dipole (LPD) antenna array is designed for 1-2 GHz operation and measured input impedance and far-field characteristics are demonstrated for a 12-element array.
Abstract: A procedure is given for designing a two-layer stripline log-periodic dipole (LPD) antenna array. Measured input impedance and far-field characteristics are demonstrated for a 12-element array for 1-2 GHz operation that are in good agreement with design specifications.

124 citations


Journal ArticleDOI
TL;DR: Proof of the feasibility of aft mounting low-profile antennas on reentry vehicles is presented and the versatility of these elements were further demonstrated by tailoring them for two different types of coverage to accommodate different vehicle operational requirements.
Abstract: Proof of the feasibility of aft mounting low-profile antennas on reentry vehicles is presented. This is an application of state of the art antenna hardware. Aft mounting presents the best reentry environment to antenna hardware, and its practicality has been demonstrated. Microstrip antenna principles can be used to produce very rugged antennas. Their low profile reduces many interface, mechanical, and survival problems. The pattern coverage for these vehicles must be toward the fore direction. This type of pattern requires an interaction between the vehicle and the antenna when the antenna is effectively shadowed from that direction. This paper describes the results obtained by actual experimental hardware. Contoured elements were used, as were foreshortened elements. These elements demonstrated ability to be fit around other aft equipment. The versatility of these elements were further demonstrated by tailoring them for two different types of coverage to accommodate different vehicle operational requirements.

38 citations


Patent
03 Feb 1977
TL;DR: In this article, the authors proposed several new and useful improvements in steering and control of a small number of elements, typically on the order of 5 to 17 elements, in order to reduce the possibility of phase transients in signals received or transmitted with the antennas, and increasing control and testing capacity with respect to the antennas.
Abstract: The present invention provides several new and useful improvements in steering and control of phased array antennas having a small number of elements, typically on the order of 5 to 17 elements. Among the improvements are increasing the number of beam steering positions, reducing the possibility of phase transients in signals received or transmitted with the antennas, and increasing control and testing capacity with respect to the antennas.

23 citations


Journal ArticleDOI
TL;DR: In this paper, an analytical model of a class of electrically small multiturn loop antennas has been formulated and compared with experimental measurements over a frequency range of 3 to 86 MHz.
Abstract: An analytical model of a class of electrically small multiturn loop antennas has been formulated and compared with experimental measurements over a frequency range of 3 to 86 MHz. Both air core and magnetically loaded eases were examined. Transmitted signal enhancement as high as 10 dB was predicted and observed by magnetic loading. Several interesting properties of the transmitting antenna were investigated experimentally and by analysis based upon the model. It is concluded that transmitted signals can be enhanced in the 2-30 MHz range, at reasonable power levels, as much as 10 dB with state-of-art ferrite materials. Secondly, the analytical model described in this paper should prove an effective design aid for a volumetrically constrained antenna of the class.

18 citations


Journal ArticleDOI
TL;DR: Tilting the antennas up to obtain 2 dB loss (for each antenna) over maximum gain during steady signal conditions is shown to reduce fading over this particular path as mentioned in this paper, and the technique should also work on other paths where sufficient angular separation between the direct and reflected rays exists, and where antennas with sufficiently "sharp" main beams are used.
Abstract: Tilting the antennas up to obtain 2 dB loss (for each antenna) over maximum gain during steady signal conditions is shown to reduce fading over this particular path. The technique should also work on other paths where sufficient angular separation between the direct and reflected rays exists, and where antennas with sufficiently "sharp" main beams are used.

15 citations


Journal ArticleDOI
TL;DR: It is shown that the frequency for maximum voltage across the load with skin as the material is 700 MHz and that resonant bare dipoles have a practical length and that insulated dipoles provide comparable voltages with the same antennas and loads at 3 GHz.
Abstract: A quantitative study is made of the receiving qualities of antennas embedded a short distance below the surface of a dissipative material in terms of the complex transfer function and the properties of the antenna. Types of antennas investigated include bare and insulated dipoles as single elements and in two-element broadside arrays. The eccentrically insulated dipole is also studied. Actual voltages across practical load impedances are determined when the antennas are embedded specifically at depths of 0.1, 0.5, and 1.0 cm in hide or skin. Comparable results apply also to muscle. A similar but more involved analysis is required if quantitative account is to be taken of a subcutaneous layer of fat between the skin and muscle. It is shown that the frequency for maximum voltage across the load with skin as the material is 700 MHz and that resonant bare dipoles have a practical length. However, the higher directivity of insulated dipoles provides comparable voltages with the same antennas and loads at 3 GHz.

13 citations


Patent
01 Aug 1977
TL;DR: In this paper, the antenna is characterized by a miniature, symmetrically toploaded dipole and efficient matching circuit at the lower VHF television band and the toploading elements are reused as parasitic elements in a compact, directive array at the upper VHF channels.
Abstract: A compact, all channel television antenna system is provided for improved reception within buildings where multiple reflections or ghosting and weak signals are typical operating conditions. The high performance in this environment with a very small antenna is achieved by the antenna's directive gain and pattern nulls, good impedance matching, low acceptance of vertical polarization, band switching, and repeatable orientation of the antenna. The antenna is characterized by a miniature, symmetrically top-loaded dipole and efficient matching circuit at the lower VHF television band. The top-loading elements are reused as parasitic elements in a compact, directive array at the upper VHF channels. Similarly, in the UHF television bands bending and top loading is used to reduce the size of radiators and to provide loading for the VHF bands. A construction of UHF half loops in parallel is used with a system of reflecting and directing elements.

10 citations


Journal ArticleDOI
A.L. Davidson1, W.J. Turney
TL;DR: Analysis of data shows that gain antennas have significantly less gain in areas where multipath propagation predominates and that the increased aperture of the gain antennas provides no significant smoothing of the received signals in the multipath environment.
Abstract: A program has been completed that investigated the effect of the urban multipath environment on mobile antennas at 900 MHz. The program involved the construction of several mobile antennas, careful measurement of these antennas on an antenna range to determine their characteristics in a controlled environment, and measurement of their characteristics in the multipath environment of cities. Measured results were compared to computed results and pattern range results were compared to field data to permit generalized conclusions to be reached. The results of the second phase of the program, measurements made in the mobile multipath environment, are presented. Analysis of this data shows that gain antennas have significantly less gain in areas where multipath propagation predominates and that the increased aperture of the gain antennas provides no significant smoothing of the received signals in the multipath environment.

10 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the maximum guidance-angle error is proportional to the amplitude of the indirect signal, the antenna beamwidth, and the time derivative of indirect signal as the direct beam-peak scans by the receiver.
Abstract: Multipath reception can cause guidance-angle errors in a microwave landing system (MLS). The antenna radiation-control problem for a scanning-beam MLS is defined and analyzed. "Centerline emphasis" is presented as a helpful design philosophy for the ground antennas. It is shown that the maximum guidance-angle error is proportional to 1) the amplitude of the indirect signal, 2) the antenna beamwidth, and 3) the time derivative of the indirect signal as the direct beam-peak scans by the receiver. This result is used in developing a rationale for the selection of the antenna beamwidth and sidelobe level (aperture size and excitation) for the azimuth and elevation guidance functions.

9 citations


Patent
23 Mar 1977
TL;DR: In this paper, a sidelobe cancellation system utilizing directional auxiliary antennas and e delays allows the spacing between the auxiliary antenna and a main radar antenna to be increased, which improves cancellation of multiple interference signals from the sidelobes of the main antenna.
Abstract: A sidelobe canceller system utilizing directional auxiliary antennas and e delays allows the spacing between the auxiliary antennas and a main radar antenna to be increased. This improves cancellation of multiple interference signals from the sidelobes of the main antenna.

7 citations


Journal ArticleDOI
TL;DR: In this paper, the admittance and current distribution of two parallel insulated monopoles in lake water were measured with three thicknesses of the insulation and the antennas were driven both in phase and in phase opposition.
Abstract: Measurements are reported of the admittances and distributions of current for two parallel insulated monopoles in lake water. Graphs of the admittance and impedance in the complex plane are displayed with the electrical distance between the elements as the parameter. These show significant coupling over electrically large separations. All data were obtained with the antennas driven both in phase and in phase opposition. Three thicknesses of the insulation were used.




15 May 1977
TL;DR: Performance capabilities of large microwave space antenna configurations with apertures generally from 100 wavelengths upwards are discussed and broad classes of antennas considered are examined and compared in terms of applications.
Abstract: Performance capabilities of large microwave space antenna configurations with apertures generally from 100 wavelengths upwards are discussed. Types of antennas considered include: phased arrays, lenses, reflectors, and hybrid combinations of phased arrays with reflectors or lenses. The performance characteristics of these broad classes of antennas are examined and compared in terms of applications.


01 Jan 1977
TL;DR: A general review of the state-of-the-art and new directions in research and development of spacecraft antennas is presented, including phased arrays, lenses, and reflector antennas.
Abstract: A general review of the state-of-the-art and new directions in research and development of spacecraft antennas is presented. Three general classes of antennas are discussed: phased arrays, lenses (dielectric and waveguide), and reflector antennas. Presently, the antenna with most applications is the reflector with considerable research being performed to improve its scan and multiple beam characteristics. Future applications for spacecraft antennas and research goals to meet these projected needs also are discussed.

Journal ArticleDOI
TL;DR: In this paper, a design procedure based on the principles of geometrical optics for antennas employing dielectric-cone feeds is described for any arbitrary amplitude and phase distributions, and can be used for dual-reflector antennas, reflector antennas with a subreflector supported with dielguides and reflector antenna with a shaped reflecting surface of the cone material.
Abstract: A design procedure based on the principles of geometrical optics, for any arbitrary amplitude and phase distributions, is described for antennas employing dielectric-cone feeds. The procedure can be used for dual-reflector antennas, reflector antennas with a subreflector supported with dielguides and reflector antennas using dielectric-cone feeds with a shaped reflecting surface of the cone material.

Proceedings ArticleDOI
20 Jun 1977