Showing papers on "Smart antenna published in 1971"
TL;DR: In this article, the minimum required antenna spacing between two base-station antennas in order to take advantage of spatial diversity technique was investigated, and it was shown that for correlation up to 0.7, the advantage of two-branch diversity can still be obtained.
Abstract: The minimum required antenna spacing between two base-station antennas in order to take advantage of spatial diversity technique was investigated. The measurements were made for two cases: (i) the incoming radio signal was perpendicular to the axis of two base-station antennas (the broadside case), and (ii) the signal was in-line with the axis of two base-station antennas (the in-line case). The correlation of signals received from two separated antennas at the base station was found to be much higher for the in-line case than for the broadside case with any given antenna spacing. For correlation up to 0.7, from which most of the advantage of two-branch diversity can still be obtained, we found the minimum required antenna spacing is around 70λ–80λ for the in-line case and 15λ–20λ for the broadside case. In order to achieve a correlation always less than 0.7 between two base-station signals regardless of the arrival direction of the incoming signal, a triangular configuration with a three-antenna array used with a three-branch diversity receiver is proposed, requiring less antenna spacing in the array than for a two-antenna setup.
69 citations
TL;DR: In this article, the maximum realized gain of arbitrary planar and circular arrays is shown to be the same as that of uniformly spaced circular arrays, and a gain equivalence between multiple planar arrays is derived.
Abstract: A theorem concerning the maximum realized gain of arbitrary arrays is proven. The theorem is applied to the specie case of uniformly spaced circular arrays. A gain equivalence between multiple planar and circular arrays is also derived.
16 citations
01 Jan 1971
8 citations
01 Jan 1971
5 citations
TL;DR: In this paper, the problem of realization of an arbitrary current distribution on an broadside array antenna derived from the theory of pattern synthesis is treated and some practical methods are proposed to yield Chebyshev patterns.
Abstract: The problem of realization of an arbitrary current distribution on an broadside array antenna derived from the theory of pattern synthesis is treated and some practical methods are proposed. In these methods, the input voltage of each antenna is transformed by a reactive transformer to take the required value. In one of the methods, experiments to yield Chebyshev patterns were performed and satisfactory results were obtained.
4 citations
3 citations
01 Jun 1971
TL;DR: A novel method is presented in which the admittance matrix representing an antenna array, consisting of both active and passive elements, is extracted from the array's element-pattern data, and enables optimization of the location of both passive and active elements.
Abstract: : The report describes a technique developed to optimize the performance of antenna arrays under realistic, on the vehicle conditions. This technique permits free choice of optimality criteria and design parameters and is applicable to both planar and nonplanar arrays with geometric constraints. The need for an improved Airborne Early Warning (AEW) airplane, the improvement being that of an airborne antenna system with reduced side lobes, was the main impetus for this investigation. The work reported grew from an initial study of the antenna array problem under the assumption of idealized free-space conditions. An experimental-computational approach to the solution of this problem has been formulated in which powerful n-dimensional optimum search methods (i.e., the Davidon algorithm) are applied to experimental data obtained from carefully scaled models of the vehicle and antenna array configuration. The optimization algorithm provides a new design for the antenna array that is then used in the scale model, and the process develops in an iterative fashion. The necessary laboratory setup and data processing techniques used to test the feasibility of this approach are discussed. Experimental results showing encouraging improvements have been obtained on an array of eight elements both with and without an aircraft model. These results indicate that the algorithmic procedure is both stable and convergent. (Author)
2 citations
1 citations
TL;DR: In this paper, the effects of non-uniform wave incident on an amplitude monopulse tracking antenna were analyzed for a target consisting of two isotropic scatterers, and compared with results obtained for the case of a locally uniform wave incident.
Abstract: Variations in apparent target direction, or glint, as sensed by an amplitude monopulse tracking antenna are analyzed for several cases when a nonuniform wave is incident on the antenna. Results are given for a target consisting of two isotropic scatterers, and compared with results previously obtained for the case of a locally uniform wave incident on the antenna.
1 citations
TL;DR: In this article, a technique for the analytical specification of optimal array geometry that enhances array reception is developed, which is illustrated for small antenna arrays of up to four elements in two classes of interference fields, with and without spatial constraints.
Abstract: A technique which allows the analytical specification of optimal array geometry that enhances array reception is developed. The technique is illustrated for small antenna arrays of up to four elements in two classes of interference fields, with and without spatial constraints. The analytical treatment is predicated upon signal detectability and employs error-free arrays of noninteracting nondirectional elements. The interference fields considered are those due to isotropic sources (case I) and sources uniformly distributed on an unbounded plane (case II). The optimality criterion is minimization of the signal detection error probability. For a phased receiving array, this is equivalent to maximizing the array detectability gain function, which has the effect of maximizing the predetection signal-to-noise ratio (SNR). The optimal array configuration is found to be two-dimensional in both cases (circular configuration in case I and elliptical configuration in case II, with the antennas equally spaced in angle along the periphery of the configuration). Numerical results are given which indicate that practical increases in predetection SNR of as much as 10 to 15 dB can be achieved by employing the array configuration most appropriate for the space-time correlation structure of the interference fields.
01 Aug 1971
TL;DR: Tubular antennas derived from arrays of gaps in circular waveguide can be designed by a computer program operating on the gap interspacings and gap widths, and taking into account realistic features like external mutual coupling and finite tube wall thickness.
Abstract: Tubular antennas derived from arrays of gaps in circular waveguide can be designed by a computer program operating on the gap interspacings and gap widths, and taking into account realistic features like external mutual coupling and finite tube wall thickness. Linearly polarised radiation makes these antennas candidates for radar applications and for microwave television transmitters.
TL;DR: In this article, a straightforward technique for optimum (minimum cost) design of digital radio relay systems is given, and the same technique with small modifications is also applied to analog FDM-FM systems.
Abstract: A straightforward technique for optimum (minimum cost) design of digital radio relay systems is given. The same technique with small modifications is also applied to analog FDM-FM systems. The total cost of a multihop radio relay system including transceiver, antenna, feeder, and mast expenses is considered by developing the cost functions for different component parts, i.e., the dependence of component price on the performance. After this the required component performances are derived based on the system specifications and the assumed mathematical model of propagation. Thus, the total cost can be minimized to get the optimum hop length and cost balance between transmitter, receiver, antenna, and mast. To illustrate the approach in a practical situation, calculations are carried out for a medium capacity digital and analog system.
TL;DR: In this article, a set of arbitrarily located receiving antenna elements, each connected with an appropriate network, can be used to construct a matched filter where the antenna array response results in an autocorrelation of a specified desired signal, correlating over time and space coordinates simultaneously.
Abstract: A set of arbitrarily located receiving antenna elements, each connected with an appropriate network, can be used to construct a matched filter where the antenna array response results in an autocorrelation of a specified desired signal, correlating over time and space coordinates simultaneously. A receiving system using such a signal processing antenna can discard interferences which do not have the same spectral characteristics as the desired signal, or which do not originate from the same point as the desired signal source. Examples of correlating antenna arrays for various arbitrary intelligence modulations of the desired signal are discussed in this communication.