## 3 Results
### Experimental Results  
Examples of the resulting direct transmissions between arrays experimentally measured at 40 mm depth (\(\theta\) = 120\({}^{\circ}\) and gap = 9.6 mm) in a water tank are shown in Figure 8, where the rectangular and Tukey apodization laws in transmit are compared. The use of a Tukey window on transmit reduced the length of the direct transmissions between arrays, from approximately 50 us (38.5 mm depth) to 43.5 us (33.5 mm depth), which approximately matches the value predicted by the simulation (Figure 2c). The energy of the direct transmissions was also reduced by the Tukey window by 6.7 dB (146.5 dB vs. 139.8 dB). Similar results were observed for different probe configurations and imaging depths.  
B-mode images of the calibrated commercial phantom (CIRS 040 GSE) above the hypoechoic cysts and above the wire targets are shown in Figure 9 for the configurations of minimum-side lobe energy (\(\theta\) = 147.57\({}^{\circ}\) and gap = 7.3 mm) and in Figure 10 for the minimum main lobe width (\(\theta\) = 127.79\({}^{\circ}\) and gap = 32.6 mm). The images were obtained after the optimization of the beamforming parameters as described in [11], and using the point-targets of the shared FOV. The targets used for optimization are marked in Figures 9 and 10 with dashed lines. Note that, due to finite tolerances of the experimental setup, the spatial configurations slightly differ from the theoretical ones used in the simulations. In agreement with the simulations (Figure 2b) and due to a larger angle between transducers, the configuration of minimum-side lobe energy (Figure 9) produces images with a greater common FOV than the configuration of minimum main lobe width (Figure 10). Some of the artifacts resulting from direct transmissions between the arrays are indicated with red arrows in the first column (rectangular window). With a smaller gap between arrays (Figure 9), there are also less cross-talk artifacts as predicted in Figure 2c, and the hypoechoic cysts are easier to identify. For both configurations the wire targets within the common FOV of both arrays appear to have narrower main lobe width.  
Different apodization laws are compared in Figures 9 and 10, i.e., (Figures 9 and 10a,d) rectangular apodization on transmit, (Figures 9 and 10b,e) Tukey apodization on transmit, and (Figures 9 and 10c,f) Tukey apodization on transmit plus weighting halved for the trans-received data for weighted compounding. Comparing the different apodization laws on transmit, overall, the Tukey law reduces cross-talk artifacts in both configurations, which are more significant and affect more depth (37.5 mm vs. 49 mm) in the minimum main lobe width configuration (Figure 10). Adding weighted compounding further decreases the observed artifacts and helps to compensate for the differences in the brightness across the image.  
Figure 8: Example of direct transmissions between arrays detected in a water tank (PW at 0\({}^{\circ}\)). (**a**) Rectangular and (**b**) Tukey apodization used on transmit. Arrays positioned with \(\theta\) = 120\({}^{\circ}\) and gap = 9.6 mm at 40 mm depth.  
shown in Table 2. As expected, the minimum main lobe width configuration presents a thinner speckle size than the minimum-side lobe energy configuration, being the case with apodization in transmit plus weighted compounding the one with the smallest speckle size in both configurations.