A variation of Minimum Variance Distortionless Response (MVDR) based Match Field Processing (MFP) referred to as Semi-coherent MVDR MFP has been developed; Initial simulation results presented here indicate that Semi-coherent MVDR MFP is both relatively robust to mismatch, with respect to relative amplitudes and phases amongst multipath arrivals in an isovelocity ocean, and comparable in performance to Full-coherent MVDR MFP under no mismatch conditions. Full-coherent MVDR MFP assumes complete and perfect characterization of the underwater propagation channel and is extremely sensitive to mismatch between assumed model parameters and actual environmental parameters. Three main conclusions may be drawn from the simulation results and deduced by analysis as well: Full-coherent MVDR MFP is extremely sensitive to mismatch. A 2 m error in the assumed ocean depth caused between a 15 and 25 dB drop in the peak of the Full-coherent MVDR MFP ambiguity surface at the true source location relative to that obtained in the no mismatch case. The performance of the "Incoherent" MVDR MFP scheme proposed by Krolik et. al.  is substantially degraded relative to that of Full-coherent MVDR MFP in the no mismatch case. The peak of the "Incoherent" MVDR MFP ambiguity surface with no mismatch was between 10 and 15 dB less than that of the corresponding Full-coherent MVDR MFP ambiguity surface. The performance of Semi-coherent MVDR MFP is both relatively robust to mismatch, with respect to error in the assumed ocean depth, and comparable in performance to Full-coherent MVDR MFP under no mismatch conditions. The three versions of MVDR MFP, Full-coherent, "Incoherent", and Semi-Coherent, are described in detail in Sections 2 and 3 of this report.
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