APB-1 Consumer Reports Addendum: Beam Noise Predictions for the MVSC Adaptive Beamformer
This report completes the Consumer Reports performance analysis study for the Phase 1 Advanced Processor Build sonar system. It provides a performance comparison between the conventional beamformer and the beam-based minimum variance soft constraint adaptive beamformer processing modules. Comparison was based on a beam noise output metric defined in terms of the beamformer array gain. This provides a more realistic measure of beamformer performance since, unlike the common definition of beam noise based solely on the noise field input to the beamformer, our beam noise metric factors in changes of signal power as the target signal is passed through the beamformer. Our results indicate that performance gain can be realized for the adaptive beamformer for certain scenarios. These gains were most likely to occur at the medium frequencies between 100 and 200 Hz, while significant gain was only occasionally observed at other frequencies. Adaptive beamforming was particularly successful when a clutter signal was present. However, any performance advantage usually begins to disappear as the target signal-to-noise ratio increases above approximately –15 dB.
Array Gain as a Function of SNR for the Beam-based MVSC Adaptive Beamformer
This paper examines the beam-based minimum variance soft constraint beamformer and shows that the beamformer array gain is almost always a function of SNR. The analysis shows that the MVSC array gain is necessarily a nonincreasing function of SNR and, in fact, is either strictly decreasing or constant relative to SNR. This result supplements earlier results of Van Veen and helps explain behavior observed in processed data.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).