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Document Type:Latin Dissertation
Language of Document:English
Record Number:52832
Doc. No:TL22786
Call number:‭3383526‬
Main Entry:Vito F. Mecca
Title & Author:MIMO space-time adaptive processing for Doppler spread multipath clutter mitigationVito F. Mecca
College:Duke University
Date:2008
Degree:Ph.D.
student score:2008
Page No:149
Abstract:The original contribution of this thesis is a multiple-input multiple-output (MIMO) generalization of space-time adaptive processing (STAP) to mitigate spread Doppler clutter returns in radar. Of particular interest is clutter subject to multipath propagation between transmit and receive arrays. Significant sources of multipath clutter can occur in over-the-horizon (OTH) radar data when ground or ocean surface returns undergo multiple ionospheric scatterings that cause considerable Doppler frequency and wavenumber spreads. In such situations, conventional single-input multiple-output (SIMO) STAP cannot mitigate Doppler spread mainlobe clutter without suppressing the target in conjunction. A MIMO radar technique is presented wherein conventional radar waveforms are phase-coded to be orthogonal after Doppler processing at the receiver, i.e. in 'slow-time.' This approach allows for slow-time MIMO radar operation that only requires a phase modification to existing radar hardware, which facilitates MIMO operation in legacy radar systems. If pulse-to-pulse transmit amplitude control is enabled, a beamspace implementation of slow-time MIMO radar is shown to reduce the voltage standing wave ratio (VSWR) in the transmit antennas, thus reducing the risk of damaging transmit hardware. The mathematical formulation of MIMO STAP is developed in terms of a novel radar propagation model that accommodates scenarios which include both direct-path and multipath clutter. MIMO STAP methods allow for effective steering of the transmit beampattern as a function of range, receive angle and Doppler frequency, allowing for a greater flexibility in receive-side adaptive and non-adaptive weight design. Thus, s can be steered in different transmit directions that give rise to multipath clutter at each range, receive angle or Doppler. Out of this framework, slow-time MIMO operation also allows for the mapping of multipath propagation known as a transmit-receive directionality spectrum (TRDS) that relates transmitted wavenumbers to received wavenumbers. In propagation environments dominated by multipath or Doppler-spread clutter, Brennan's rule estimates of clutter rank can be significantly different than the actual clutter rank. A TRDS based method of estimating clutter rank is presented that captures over 30% more of the eigenvalues in a multipath environment for half-wavelength spaced arrays than a MIMO version of Brennan's rule captures. Simulation results demonstrate that in the presence of multipath clutter, large signal-to-clutter-plus-noise ratio (SCNR) gains over SIMO radar can be achieved by adaptively steering an effective transmit in the outbound direction towards the multiply scattered clutter. Additionally, slow-time MIMO STAP methods are implemented on an acoustical laboratory transmit/receive system to provide concrete examples of the concepts introduced herein in an environment rich with spread Doppler multipath clutter. Partially adaptive MIND STAP receive-side processing methods on real data are able to achieve over 25 dB of clutter suppression while maintaining a strong target response.
Subject:Applied sciences; Space-time adaptive; Doppler spread; Multipath clutter; Radar clutter; Electrical engineering; 0544:Electrical engineering
Added Entry:J. L. Krolik
Added Entry:Duke University