Showing papers on "Smart antenna published in 1976"
TL;DR: In this paper, the possibilities of connecting a lossless network between input ports and antenna ports such that there is no coupling and scattering between the antennas are discussed, and a necessary condition for complete decoupling and descattering is power orthogonality between the patterns of the individual antennas.
Abstract: The possibilities of connecting a lossless network between input ports and antenna ports such that there is no coupling and scattering between the antennas are discussed. A necessary condition for complete decoupling and descattering is power orthogonality between the patterns of the individual antennas. Numerical and experimental results are presented for monopole antennas.
246 citations
TL;DR: Computer simulations and breadboard array measurements substantiate the mathematical development and indicate the practicality of the optimal phase weightings and demonstrate the decomposition of the antenna pattern into a sum of patterns which place gain towards each directional emitter.
Abstract: Adaptive null-steering arrays which use phase-only weights are examined. The optimal phase weightings are developed and the mathematical equations are reduced to a simplified computational form. Approximations for low sidelobe arrays allow more efficient computations and demonstrate the decomposition of the antenna pattern into a sum of patterns which place gain towards each directional emitter. Computer simulations and breadboard array measurements substantiate the mathematical development and indicate the practicality of the method.
140 citations
TL;DR: Some fundamental limitations on radiation pattern nulling inherent in any multiple-beam antenna system are derived and the earth-coverage constraint is seen to severely limit the gain available to a signal source near the null, relative to the maximum signal mode.
Abstract: Some fundamental limitations on radiation pattern nulling inherent in any multiple-beam antenna system are derived. The specific case of a satellite multiple-beam antenna at synchronous altitude operating over the earth field of view is considered in detail, although the general results are presented so as to be applicable to an arbitrary planar aperture such as a phased array. The multiple-beam antenna offers the large aperture needed for good nulling resolution, while keeping the number of signal ports utilized in any nulling algorithm at a tractable number. Two specific modes of operation are considered: an earth-coverage mode, in which one desires to null a number of interfering sources while realizing the best possible earth-coverage communications link over the remaining earth field of view; and a maximum signal mode, where one desires only to maximize the signal to a specified number of users while nulling the interfering sources. Both cases are treated in detail. Optimum results are derived for an arbitrary planar aperture and compared to what can be accomplished with a fixed set of beams (the case of 7 and 19 beams are considered). For the earth-coverage mode, the quality of the earth-coverage radiation pattern versus beam position must be traded off with the optimum beam position for good nulling-i.e., it will be shown that the set of beams which gives the flatest earth-coverage radiation pattern with no prescribed nulls is not optimum when nulls are to be formed. The optimum beam positioning is determined using the results of two-dimensional sampling theory. Furthermore, the earth-coverage constraint is seen to severely limit the gain available to a signal source near the null, relative to the maximum signal mode. The maximum directivity available to a user in the maximum signal mode is also shown to be a function of beam position. For signal sources close to the edge of the field of view, the directivity available to the source can be significantly less than optimum.
29 citations
TL;DR: In this article, the radiation resistance of loop antennas with dimensions comparable to the wavelength was calculated by means of a digital computer, and the result showed that the antenna's radiation resistance is linear in the length of the antenna.
Abstract: Loop antennas with dimensions comparable to the wavelength are sometimes of practical interest. In order to use such antennas, design engineers would need simple formulas or data about the radiation resistance of such antennas. For the reason, that nothing else has been known, the radiation resistance has been calculated by means of a digital computer.
28 citations
TL;DR: The experimental pattern behavior of a four-element adaptive array based on a steepest-descent feedback algorithm that uses four multiturn loop elements on an aircraft fuselage mock-up is described.
Abstract: The experimental pattern behavior of a four-element adaptive array based on a steepest-descent feedback algorithm is described. The array uses four multiturn loop elements on an aircraft fuselage mock-up. Operational patterns have been measured as a function of various parameters: frequency, element placement, desired signal and interference angles of arrival, signal powers, etc. Typical patterns are presented and the performance characteristics of the array are described.
26 citations
7 citations
TL;DR: In this article, multiple-antenna arrays with respect to size, performance characteristics, and cost are discussed with a focus on the use of circularly polarized antennas on candelabra arrays.
Abstract: Multiple-antenna arrays are discussed with respect to size, performance characteristics, and cost. Parameters are given to facilitate optimizing by the broadcaster of multiple-antenna structure size and performance. Use of circularly polarized antennas on candelabra arrays is also discussed.
6 citations
24 Mar 1976
TL;DR: This paper describes several electronically-steered phased-array antennas for use in the HF, VHF and UHF bands and methods will be described for mode selection of omni and the four quadrantal directions using semiconductor switching.
Abstract: This paper describes several electronically-steered phased-array antennas for use in the HF, VHF and UHF bands. An approach is described which uses 4 vertical elements above the ground plane in a square pattern. With proper phasing, a directive beam of 97° width may be electronically switched in quadrants to provide full 360° azimuth coverage. This antenna provides significant forward gain and a high front-to-back ratio to provide suppression of interference not in the path of communication. An alternate approach uses three elements in a triangular configuration, each beam covering 120° of azimuth. Methods will be described for mode selection of omni and the four quadrantal directions using semiconductor switching.
1 citations
TL;DR: A computer program has been written to simulate antenna performance on a small ground plane and gain relationships between a quarter-wavelength antenna and various gain antennas over different sized ground planes are presented.
Abstract: A computer program has been written to simulate antenna performance on a small ground plane. The solution for a quarter-wavelength antenna has been expanded to include larger antennas with more complex current distributions. This paper includes a summary of the computer program and presents gain relationships between a quarter-wavelength antenna and various gain antennas over different sized ground planes. Experimental data which verify the results of the program are also presented.
01 Jul 1976
TL;DR: The potential uses and techniques for the shuttle spacelab Millimeter Wave Large Aperture Antenna Experiment (MWLAE) are documented in this article, where applications to radio astronomy, the sensing of atmospheric turbulence by its effect on water vapor line emissions, and the monitoring of oil spills by multifrequency radiometry are identified.
Abstract: The potential uses and techniques for the shuttle spacelab Millimeter Wave Large Aperture Antenna Experiment (MWLAE) are documented Potential uses are identified: applications to radio astronomy, the sensing of atmospheric turbulence by its effect on water vapor line emissions, and the monitoring of oil spills by multifrequency radiometry IF combining is preferable to RF combining with respect to signal to noise ratio for communications receiving antennas of the size proposed for MWLAE A design approach using arrays of subapertures is proposed to reduce the number of phase shifters and mixers for uses which require a filled aperture Correlation radiometry and a scheme utilizing synchronous Dicke switches and IF combining are proposed as potential solutions
TL;DR: In this paper, a special form of complex matrix called a "phasedifference matrix" that arises in the optimization of antenna arrays is discussed and it is shown that the inverse of such a matrix can be obtained by inverting an associated real matrix without having to perform any arithmetic operations with complex numbers.
Abstract: A special form of complex matrix called a "phase-difference matrix" that arises in the optimization of antenna arrays is discussed. It is shown that the inverse of such a matrix can be obtained by inverting an associated real matrix without having to perform any arithmetic operations with complex numbers.