University Events

Description: Topic: Mitigating Interferer Motion with Universal Adaptive Beamformers

Location: Lester W. Cory Conference Room, Science & Engineering Building (SENG), Room 213A

Zoom Conference Link: https://umassd.zoom.us/j/92380705367
Meeting ID: 923 8070 5367 Passcode: 539575

Abstract:
A signal received by a passive sonar may contain the desired signal, background noise, and moving or nonmoving interferers simultaneously. The beamformer processes observed narrowband signals to implement a spatial filter by selecting the desired signal from a specific location while eliminating loud interference and noise from other locations. One of the most common adaptive beamformers is the minimum variance distortionless response (MVDR) beamformer. The MVDR beamformer minimizes the output power of the array subject to a unity gain constraint in the direction of the desired signal. The MVDR beamformer obtains a minimized output power by placing sharp notches in the location of the interferers. MVDR is an optimal beamformer when a nonmoving interferer is present. However, close range, fast interferers move with a high bearing rate, transiting resolution cells faster and challenging MVDR's ability to place accurate notches in the actual direction of the interferer. Consequently, the MVDR notch location will always slightly lag the interferer's actual location, and the MVDR beamformer's ability to suppress the interferer degrades. Applying a flatter and broader notch near the interferer location is a more effective approach to dealing with the interferer motion. Many proposed notch widening approaches attenuate the interferers by placing a fixed large notch in the direction of the interferer. Choosing a larger notch width is a conservative approach to attenuate interferers but wastes degrees of freedom and reduces the white noise gain. A universal beamformer can be used to balance the trade-off between interferer suppression and white noise attenuation by saving degrees of freedom even in dynamic environments. The universal beamformer converges to the performance of the best beamformer in a set by choosing the blend weights so that the regret goes to zero asymptotically. This work will investigate the universal version of double zero, the covariance matrix tapers, and spatial subband processing to expand the width of the notch with fewer degrees of freedom and analyze their respective performance in interferer suppression and white noise gain.

Advisor(s): Dr. John R. Buck, Chancellor Professor, Department of Electrical & Computer Engineering, UMASS Dartmouth

Committee Members: Dr. David A. Brown, Professor, Department of Electrical & Computer Engineering, UMASS Dartmouth; Dr. Paul J. Gendron, Associate Professor, Department of Electrical & Computer Engineering, UMASS Dartmouth; Dr. Kay L. Gemba, Professor, Naval Postgraduate School

NOTE: All ECE Graduate Students are ENCOURAGED to attend.
All interested parties are invited to attend. Open to the public.

*For further information, please contact Dr. John R. Buck at 508.999.9237 or via email at jbuck@umassd.edu.