Interfenence Sources and Degrees of Freedom in Adaptive Nulling Antennas.
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- May 12, 1982
- Accession Number
- ADA116583
Entities
People
- Alan J. Fenn
Organizations
- Massachusetts Institute of Technology