Showing papers on "Smart antenna published in 1979"

Water-Immersed Microwave Antennas and Their Application to Microwave Interrogation of Biological Targets

Abstract: This paper describes a method of significantly improving the resolution of systems used for interrogating the spatial variation of permittivity of biosystems at S band. The basic principle employed is to contract the wavelength of the interrogating radiation and to reduce the physical aperture of the interrogating probes by immersing the transmitting antenna, receiving antenna, and the target into a material with a high dielectric constant, namely water. The antenna design is described, and line scans employing transmitted and reflected energy are presented.

Controlling Adaptive Antenna Arrays with the Sample Matrix Inversion Algorithm

Abstract: Considerations are given leading to the selection of the samplematrix inversion algorithm for the control of an airborne narrowbandand adaptive receiving array for use in omnidirecti com communications. Performance is measured for a laboratory nulling system which implements this design concept. This performance ance is compared with predictions based on the component tolerances of the laboratory system.

Steepest descent controller for an adaptive antenna array

Abstract: An adaptive antenna array including a main antenna and an auxiliary antenna with a steepest descent controller for deriving the optimal feedback gain to guarantee stable and rapid convergence of the weights comprising the weight vector w(t) to form a null in the direction of interference while having minimal effect on the main beam.

Method and apparatus for electrically scanning an antenna array in a monopulse DF radar system

Abstract: From an antenna array of a plurality of fixed, narrow beamwidth antennas, geographically oriented to provide omnidirectional coverage, first and second sets of antennas are selected in sequence. The first selected set includes several pairs of oppositely oriented antennas. The signals received by the antennas in each pair of the first selected set are combined and each of the combined signals is connected to a different one of a number of matched receiver channels. If the logarithmic video output signals from the receiver channels meet certain rules of acceptance, the monopulse ratio, formed by subtracting the outputs of the channels receiving the strongest and next strongest signals, is digitized and stored. This ratio represents the angular difference between the direction of the received signal and the direction of one of the antennas in the pair of the first set generating the strongest signal. However, it cannot be determined which of the antennas in the pair has the forelobe response and, thus, the ratio contains a 180° ambiguity. To resolve the ambiguity, a second antenna set is selected to include only the pair of the first selected set which were connected to the channel receiving the strongest signal. Each antenna in the second set is connected to the input of a different channel, the outputs of which are compared. The stronger signal is considered to be the forelobe response, and information relating to the sector of the antenna with the stronger signal is used to resolve the ambiguity present in the stored ratio.

Linear antenna arrays with broad nulls with applications to adaptive arrays

Abstract: The problem of designing a class of linear antenna arrays with broad nulls against interfering signals of variable direction of arrival is considered. The problem is formulated in an appropriate signal space selected for an efficient representation of array signals of specified angular occupancy. The array-weight vector is then chosen to be orthogonal to this space. The approach is seen to yield a min-max array in a sense to be defined in this paper. The application of such arrays to maintain the beamshape of an adaptive antenna array is also illustrated.

Radiation characteristics of dielectric tube antennas

Abstract: A study of the radiation characteristics of dielectric tube antennas is made with a possibility of its application in communications satellites. It has been shown through a systematic analysis that a multimoded dielectric tube shows a dip in the boresight region which is suitable for satellite antennas.

A review of adaptive antennas

Abstract: Most adaptive receiving arrays permit beam steering in a selected "look" direction while rejecting or nulling strong interferences which arrive at angles other than the look direction. Nulling is accomplished by adjusting parameters of a signal processor connected to the array sensing elements (whether at rf, audio, or seismic frequencies) to minimize total output power. A signal arriving in the look direction would not be nulled because the adaptive process is constrained to maintain a predetermined sensitivity in the look direction. A substantial literature exists in the field. The September 1976 issue of the IEEE Transactions on Antennas and Propagation was dedicated to the subject of adaptive antennas. It is the purpose of this presentation to compare the works of Howells and Applebaum, Widrow, and Frost.

A mobile radio antenna system having a self-diplexing function

Abstract: A coupled N-element antenna system on a mobile unit for simultaneous transmission and reception is discussed. A diplexer is required when an antenna for transmission and that for reception are installed with mutual coupling between them. An attempt is made to reduce coupling between the transmitting point and the receiving point by a lossless network and coupled antennas. The network is connected between the antenna and the input and output ports. The decoupled antenna is analyzed and theoretical and experimental results, which show the feasibility of the antenna system, are described.

Lossy-feed networks in multiple-beam arrays

Abstract: Using a lossy-feed network in a multiple-beam array antenna, particularly a receiving system without active amplifying components embedded in the network, has generally been avoided. Attention is called to certain antenna pattern characteristics that should be evaluated with respect to the system application involved. Lossless-feed networks often possess one or more of these pattern characteristics which can possibly be enchanced when the capabilities of a lossy network are properly traded off. Maximizing available antenna gain at the beam crossover points, for example, is shown to be one possible advantage for employing a lossy network instead of a lossless design. Near-in sidelobe levels can readily be controlled with a lossy network.