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 N-element phased array or N-beam multiple-beam antenna can adaptively null. This problem is usually addressed by considering the antenna to have at most N-1 degrees of freedom available for placing null on interference sources. However, if some of the N-1 sources are very close together, it is possible that less than N-1 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 equal-power interference sources in the field of view of either a multiple-beam antenna, or a phased array antenna, the two dominant eigenvalues are approximately equal when the source separation is equal to one half-power beamwidth. In other words, two degrees of freedom are consumed by two interference sources when they are separated by approximately one half-power 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