The dynamic range of adaptive beamformers

All adaptive beamformers aim at increased resolution and better contrast. However, the same effect can be produced by dynamic range stretching. Adaptive beamformers are often tested on wire targets or uniform cysts, which do not allow to study dynamic range alterations. This work shows that dynamic range stretching may account for some of the benefits of some adaptive beamformers in the literature. We propose a phantom allowing us to do a dynamic range calibration. We demonstrate this calibration for the Mallart-Fink Coherence Factor (CF), the Camacho-Fritsch Phase Coherence Factor (PCF) and Capon'sMinimum Variance (MV) beamformer.We show that the increased resolution and contrast reported for the CF and PCF are to a great extent due to the alterations of the dynamic range.