
Accession Number : ADA116583
Title : Interfenence Sources and Degrees of Freedom in Adaptive Nulling Antennas.
Descriptive Note : Technical rept.,
Corporate Author : MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
Personal Author(s) : Fenn,Alan J
PDF Url : ADA116583
Report Date : 12 May 1982
Pagination or Media Count : 41
Abstract : It is sometimes desirable to know how many interference sources can Nelement phased array or Nbeam multiplebeam antenna can adaptively null. This problem is usually addressed by considering the antenna to have at most N1 degrees of freedom available for placing null on interference sources. However, if some of the N1 sources are very close together, it is possible that less than N1 degrees of freedom are used. This paper quantitatively describes this effect by examining the eigenvalue spread of the interference covariance matrix. It is shown in the case of two equalpower interference sources in the field of view of either a multiplebeam antenna, or a phased array antenna, the two dominant eigenvalues are approximately equal when the source separation is equal to one halfpower beamwidth. In other words, two degrees of freedom are consumed by two interference sources when they are separated by approximately one halfpower beamwidth. This effect is also investigated for several configurations of three interference sources. To consume three degrees of freedom, it is shown that the eigenvalue spread is dependent on the interference source configuration and the antenna geometry. (Author)
Descriptors : *Antenna arrays, *Adaptive systems, Nulls(Amplitude), Multiple access, Degrees of freedom, Eigenvalues, Interference
Subject Categories : Electrical and Electronic Equipment
Distribution Statement : APPROVED FOR PUBLIC RELEASE