Showing papers on "Smart antenna published in 1988"
Proceedings Article•
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01 Sep 1988
TL;DR: In this paper, the authors give a perspective on DBF technology and propose an approach to preserve the total information received at the array aperture which, coupled with the flexibility of digital processing, offers a number of attractive features beyond the capabilities of conventional arrays.
Abstract: Digital beamforming (DBF) is an emerging technology which represents a quantum step in antenna performance. The approach preserves the total information received at the array aperture which, coupled with the flexibility of digital processing, offers a number of attractive features beyond the capabilities of conventional arrays. The intent of this paper is to give a perspective on DBF technology.
23 citations
12 Apr 1988
TL;DR: In this paper, Anderson et al. investigated the feasibility of optical processor based beamforming for microwave array antennas and developed a mathematical model to determine the necessary design parameters required for spatial aspects of the microwave "footprint" formation.
Abstract: Antenna beamforming using optical processingL. P. Anderson, F. Boldissar, D. C. D. ChangHughes Aircraft Company, Space and Communications GroupP. 0. Box 92919, El Segundo, California 90245ABSTRACTThis work concerns intself with the analytical investigation into the feasibility of opticalprocessor based beamforming for microwave array antennas. The primary focus is on systemsutilizing the 20/30 GHz communications band and a transmit configuration exclusively toserve this band.A mathematical model is developed for computation of candidate design configurations. Themodel is capable of determination of the necessary design parameters required for spatialaspects of the microwave "footprint" (beam) formation. Computed example beams transmittedfrom geosynchronous orbit are presented to demonstrate network capabilities.
19 citations
TL;DR: The experimental and analytical results obtained through the 15-meter antenna program will provide new technology for the application of large space antennas for future missions.
15 citations
06 Jun 1988
TL;DR: In this paper, the authors considered the application of eigenvector techniques to the solution of interference problems and extended the conventional minimum-variance signal-to-noise-ratio criteria to a case in which the eigenstructure of the array correlation matrix is used to cancel directional interference sources.
Abstract: The authors consider the application of eigenvector techniques to the solution of interference problems. The conventional minimum-variance signal-to-noise-ratio criteria are extended to a case in which the eigenstructure of the array correlation matrix is used to cancel directional interference sources. It is shown that while the method has good interference cancellation properties, it results in higher pattern distortion than conventional arrays. >
14 citations
17 Oct 1988
TL;DR: Describes the development activities and summarizes the results of a vehicle antenna program at JPL in support of a developing US mobile satellite service (MSS).
Abstract: The paper summarizes results of a vehicle antenna program at JPL in support of a developing U.S. mobile satellite services (MSS) designed to provide telephone and data services for the continental United States. Two classes of circularly polarized vehicle antennas have been considered for the MSS: medium-gain, satellite-tracking antennas with 10-12-dBic gain; and low-gain, azimuthally omnidirectional antennas with 3-5-dBic gain. The design and performance of these antennas are described, and the two antennas are shown to have peculiar advantages and disadvantages.
9 citations
06 Jun 1988
TL;DR: In this paper, a beam-space nulling algorithm is described which has potential for applications in communication circuits which are degraded by multipath signals, and results are presented from tests of the algorithm using real multipath data.
Abstract: A beam-space nulling algorithm is described which has potential for applications in communication circuits which are degraded by multipath signals. Results are presented from tests of the algorithm using real multipath data. The data used in these tests were recorded using a beacon and a large aperture antenna. These measurements were carried out on an over-water path. The direct signal, i.e. the signal that propagated via the shortest path from the beacon to the antenna, is selected as the desired signal and the indirect signal(s), i.e. the signals that propagated via reflection from the surface of the water, as the unwanted signal(s). In many cases the wanted and unwanted signals are separated by less than a beamwidth. Two examples are given. >
5 citations
06 Jun 1988
TL;DR: In this paper, a digital beamforming (DBF) array was fabricated and tested using commercially available parts to demonstrate beam agility and reconfigurability, and the experimental and theoretical patterns of a flat-top-beam and a difference pattern obtained by inverting the phase of half of the array were shown.
Abstract: A digital beamforming (DBF) array was fabricated and tested using commercially available parts to demonstrate beam agility and reconfigurability. The antenna portion of the DBF system consists of a 2*4 array of microstrip patch elements. The patch radiators are corner-fed square elements with a diagonal slot for circular polarization designed at 2.95 GHz in Duroid. The signal is split into I (inphase) and Q (quadrature phase) channels, and each channel is converted into a digital signal by an 8-b A/D (analog-to-digital) converter at a 5 MHz rate. The I and Q channels of each element are multiplied by an 8-b weight vector. The results of the I multiplications and Q multiplications are separately summed and then detected and converted to a DC voltage output proportional to the input received signal level. Numerous different patterns were obtained by varying the I and Q weight vectors appropriately. The experimental and theoretical patterns of a flat-top-beam and a difference pattern obtained by inverting the phase of half of the array are shown. >
5 citations
11 Apr 1988
TL;DR: The authors compare the performance of the standard LMS algorithm with the proposed scheme and shows that the proposed algorithm has a better convergence performance.
Abstract: The constrained least-mean-squares (LMS) algorithm uses a noise estimate of the required gradient to adaptively estimate the weights of an optimal antenna array. The gradient is estimated by multiplying the array output with the array receiver outputs. An alternative scheme for estimating the required gradient is proposed. The proposed scheme uses a structured estimate of the array correlation matrix to estimate the gradient. This structure reflects the structure of the exact array correlation matrix and is obtained by a spatial averaging of the elements of the noisy array correlation matrix used in the standard algorithm. The authors compare the performance of the standard LMS algorithm with the proposed algorithm and shows that their algorithm has a better convergence performance. >
4 citations
06 Jun 1988
TL;DR: In this paper, the synthesis of an array of non-uniformly spaced elements is studied, for a predefined number of elements, the element distribution yielding a directivity pattern which most closely approximates the desired pattern.
Abstract: The authors focus on the synthesis of equally excited arrays obtained by modifying element number and position. The advantage of these arrays resides in the simplification of the feed system. On the other hand, certain constraints arise, due to the fact that the elements cannot overlap. The results were obtained with two types of antenna arrays based on microstrip radiating elements: arrays with nonuniformly spaced elements, and arrays with switched feeding systems. For both types of array, excitation was equal in amplitude and phase. The synthesis of an array of nonuniformly spaced elements consists in determining, for a predefined number of elements, the element distribution yielding a directivity pattern which most closely approximates the desired pattern. This distribution may be either linear or planar. For each of the two types of arrays, a number of different synthesis methods were used. The results of several of these methods are presented. >
2 citations
01 May 1988
TL;DR: Multibeam arrays are first discussed, then unfurlable and inflatable reflector antennas are described, now qualified in Europe for future mobile systems, for which the optimum choice of antenna technology has been found to be the key to efficient use of spectrum and power resources.
Abstract: The onboard antenna front end is the key subsystem conditioning configuration and performance of mobile communication satellites. The objectives of this paper are to demonstrate this key role and to review L-band satellite antenna technology for earth coverage and regional applications. Multibeam arrays are first discussed, then unfurlable and inflatable reflector antennas are described. These technologies are now qualified in Europe for future mobile systems, for which the optimum choice of antenna technology has been found to be the key to efficient use of spectrum and power resources.
2 citations
11 Apr 1988
TL;DR: A preliminary performance study shows that proper spatial filtering can be achieved whether the desired signal and the interferences are correlated or not.
Abstract: A novel approach is presented to wideband adaptive beamforming for correlated desired signal and interferences. Unlike spatial smoothing, it solves the signal cancellation problem by using the idea of frequency-domain smoothing. Advantages over the spatial smoothing are identified, and a particular method is developed for moderately wideband system applications. A preliminary performance study shows that proper spatial filtering can be achieved whether the desired signal and the interferences are correlated or not. >
23 Feb 1988
TL;DR: A new adaptive cancelling technique which can be implementated on multiple beam antenna systems and exhibits efficient operation even with highly correlated target and interference signals.
Abstract: This paper presents a new adaptive cancelling technique which can be implementated on multiple beam antenna systems. One of its notable features is that it exhibits efficient operation even with highly correlated target and interference signals.
28 Nov 1988
TL;DR: The use of higher order modes in a horn reflector antenna to achieve pattern diversity is discussed and a candidate mode coupler is analyzed, and the measured performance for a one-fifth-scale model is reported.
Abstract: The use of higher order modes in a horn reflector antenna to achieve pattern diversity is discussed. During multipath fading, off-axis arrival of signals excites higher-order modes in the antenna feed. The separation of the appropriate modes and their proper recombination can be used to generate two orthogonal antenna patterns for both vertical and horizontal polarizations. A candidate mode coupler is analyzed, and the measured performance for a one-fifth-scale model is reported. >
06 Jun 1988
TL;DR: In this paper, the most promising antenna system for DBS was identified in a reconfigurable dual antenna configuration (circular polarization) with aperture diameters of 2.5 m to be mounted on the spacecraft sidewalls.
Abstract: The most promising antenna system for DBS has been identified in a reconfigurable dual antenna configuration (circular polarization) with aperture diameters of 2.5 m to be mounted on the spacecraft sidewalls. Beam reconfigurability foresees the combination of coverages two, three, four and five in two supercoverages (2+3 and 4+5, respectively). Channel routing is accomplished by using variable power dividers, while feed sharing on the same polarization among overlapping beams is avoided by a suitable coverage assignment among the two antennas. A preliminary mass estimate indicates that the reconfigurable dual antenna weight is in the order of 110 kg, against the 80 kg of the single antenna. The computed RF powers for each channel are given. >