# Broadband Generalized Sidelobe Canceler Beamforming Applied to Ultrasonic Imaging
## 5 Discussion and Conclusions  
The beamforming responses in Figure 3 are the key to understand the advantages of Broadband-GSC. Compared with traditional non-adaptive beamforming DAS and SA, Broadband-GSC will significantly improve the lateral resolution and restrain the interference and noise signal. Broadband-GSC only uses the receiving focused echo signal after DAS, which achieves an increase in lateral resolution with only one single emission. Compared with GSC, Broadband-GSC not only reduces the beamforming process complexity, but also reduces the system hardware complexity. Consequently, Broadband-GSC beamforming allows for high frame-rate imaging with increased imaging quality. The experiment of circular cyst shows that Broadband-GSC still can improve the lateral resolution and PSL even during the high speckle noise environment. Meanwhile, beamforming algorithms cannot improve the axial resolution. The axial resolution of the ultrasonic imaging system is determined by the center frequency of the ultrasonic f\({}_{0}\), ultrasonic velocity c, and the emitted ultrasonic numbers. The axial resolution of system can be improved by algorithm like coded excitation.  
Plane wave emission experiment changes the emission way of ultrasonic imaging system. Plane wave emission will use all elements to transmit ultrasonic, therefore, improves the system's SNR to obtain higher investigation depth. The system's SNR also influences the performance of the  
Figure 8: Lateral variation of each beamforming, (**a**) z = 35.6 mm; (**b**) z = 40.6 mm.  
Figure 7: Beamforming responses of the 16 scattering point targets with plane wave emission. (**a**) DAS; (**b**) Broadband-GSC.  
adaptive beamforming. Previous work [28] indicates that the performance of adaptive beamforming is dependent on the system's SNR. When system's SNR decreases, imaging quality after adaptive beamforming will rapidly decrease. Hence, plane wave emission still is one of the most commonly used emission methods in commercial ultrasonic imaging products. Results indicate that Broadband-GSC can achieve an increase in lateral resolution and PSL with only one single emission. Therefore, Broadband-GSC can be introduced to deal with the received echo data after plane wave emission.  
Broadband-GSC introduces the discrete wavelet transform to divide the broadband echo signal into a set of narrowband signals. Therefore, narrowband methods can be applied directly on broadband ultrasonic data. Basing on adaptive beamforming GSC, a set of adapted, data-dependent apodization weights for each wavelet subband are provided. Broadband-GSC can both maintain the desired signal and suppress the interference and noise signal, therefore, improves the system imaging quality. Furthermore, Broadband-GSC achieves an increase in lateral resolution with only one single emission. New beamforming reduces the algorithm process complexity and the system's hardware complexity. Broadband-GSC introduces the possibility for higher frame-rate and higher investigation depth with better imaging quality.  
Conceptualization, J.L. and X.C.; Methodology, L.M. and Z.M.; Software, H.C., Y.W. and Z.W.; Validation, J.L., L.M. and Z.M.; Formal Analysis, J.L., L.M. and Z.W.; Investigation, J.L. and Z.M.; Resources, J.L.; Data curation, J.L. and Z.W.; Writing--Original Draft Preparation, J.L., L.M. and Z.M.; Writing--Review & Editing, J.L., H.C. and Y.W.; Visualization, L.M. and Z.M.; Supervision, X.C. and Z.M.; Project Administration, L.M. and Z.M.; Funding Acquisition, H.C., Y.W. and X.C. All authors have read and agreed to the published version of the manuscript. This research was funded by [China National Key R&D Program during the 13 th Five-year Plan Period] grant number [2018 YFC0116200] and [China National Key R&D Program during the 13 th Five-year Plan Period] grant number [2017 YFC0109702]. The authors declare no conflict of interest.