In this paper, the development of weighted nonlinear beamformer, called as Filtered Delay Weighted Multiply and Sum (F-DwMAS) is reported. This method was investigated on Synthetic Transmit Aperture (STA) technique. The performance of the developed F-DwMAS method was compared with Delay and Sum (DAS) and recently introduced F-DMAS beamforming methods. Importantly, in the method proposed, an extra window stage is added after the delay stage in the F-DMAS method. The different methods of DAS, F-DMAS and F-DwMAS were compared in terms of the resulting image quality metrics, Lateral Resolution (LR), Axial Resolution (AR), Contrast Ratio (CR) and contrast-to-noise ratio (CNR), in experiments on tissue-mimicking phantoms. Experimental results show that, for STA technique, F-DwMAS resulted in improvements of AR by 46.91% and 30.19%, LR by 61.35% and 52.48%, CR by 84.68% and 27.51%, and CNR by 5.45% and 34.4% compared to those obtained using DAS and F-DMAS, respectively. Hence, it can be concluded that the image quality is improved by F-DwMAS compared to DAS and F-DMAS. © 2020 IEEE.