An Introduction to Adaptive Arrays
Abstract
A tutorial introduction to adaptive arrays is presented via analysis of linear arrays with adaptive control loops of the Applebaum analog type, which derive weighting adjustment control from the correlations between element signals, i.e., on the basis of the covariance matrix of the set of system inputs. Phase conjugacy, cross-correlation interferometers, and the IF phase- cancellation principle were reviewed, and a simple two-element array with a single adaptive control loop was analyzed. The analysis was based on reduction to a type-O follower servo equivalent circuit and includes transient behavior, bandwidth effects, and the Applebaum hard-limiter modification. The analysis then proceeded to a K-element linear array with K adaptive control loops. The system analysis consisted of a Q-matrix transformation into orthonormal eigenvector space, and interpreting the transformation in terms of an orthogonal beam-forming network, similar in principle to a Butler matrix network. The system was thus converted into an equivalent 'orthonormal,' adaptive control- loop network to which the type-O follower servo analysis can again be applied. The Q-matrix transformation network produced a set of K orthogonal, normalized, eigenvector beams whose output powers are proportional to the eigenvalues of the covariance matrix. These beams were used as the basis of a convenient expression for calculating the time-dependent output pattern function for the array.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 31, 1974
- Accession Number
- AD0922178
Entities
People
- William F. Gabriel
Organizations
- United States Naval Research Laboratory