Adaptive Beam Forming
Agenda
Antennas Filter Signals Based Upon Angle of Arrival
Simplifying Assumptions
Antennas Are Angle Of Arrival Filters
Antenna patterns can be found by evaluating the Z-transform of the weights, w, at points along the unit circle.
Array Pattern is DFT of Weighting
Maximizing Signal-to-Thermal-Noise Ratio
Analogies hold for all Z-transform properties
Steering is accomplished with a linear phase progression across the array.
Tapering the illumination pattern lowers sidelobes - reduces the nominal interferer for an unknown angle of arrival
The product of illuminations results in the convolution of the corresponding patterns (i.e. delta pattern).
The product of illuminations results in the convolution of the corresponding patterns (i.e. low sidelobe delta pattern).
Adaptive Beam Forming Utilizes Dynamic Weight Coefficients
Optimum Linear Filtering Maximizes the Signal-to-Interference plus Noise Ratio (SINR)
Assumptions
Derivation of Optimum Weight Vector
Derivation (cont’d)
The scale factor ? for the optimal weight w is arbitrary.
Covariance Matrix Basics
SINR Loss is the primary performance metric
Cancellation Ratio
PPT Slide
Covariance Matrix Estimation
Covariance Matrix Estimation (cont’d)
Data Domain Method
Jammer Cancellation with Linear Arrays
Diagonal Loading for Pattern Control
A Final Word About Covariance Matrix Estimation
Adaptive Beamforming Consists of Two Steps; Weight Calculation and Weight Application
Weighting receiver outputs to best match a desired sequence steers the antenna toward the desired signal.
An adaptive receiver forms a beam in the direction of the desired signal while simultaneously steering nulls in the direction of interferers and multipath reflections.
Email: mikepascale@ieee.org