The straight bus bar simulation was rerun with solid aluminum plates placed above and below the devices. The distance from the top of the bus bar to the edge of the aluminum, X, was swept from 7-24 mm. The ICs are placed in the same location relative to the bus bars as they were in Figure 3-2.

Figure 4-1 Straight Bus Bar Surrounding Metal - Side View

Figure 4-2 Straight Bus Bar Surrounding Metal - 3D

The error vs distance plots, Figure 4-3, for the straight bus bar configuration show that error grows monotonically as a conductor approaches the bus bar. More importantly, the error gradient is steepest at closer distances—the difference in error between 7 mm and 10 mm spacing is substantially larger than the difference between 20 mm and 23 mm spacing. When there is a conductor above and below or only above the bus bar, even when a conductor is only 7-10 mm away, the error impact is minimal. When the conductor is only below the bus bar a larger keep-out area is needed, approximately 15-20 mm.

Figure 4-3 Straight Bus Bar Error vs Distance from Surrounding Metal

To get an idea of the impact of surrounding conductors over frequency the error vs frequency is recorded in Figure 4-4 for different distances of the aluminum plate from the bus bar. Significant amplitude and phase errors persist over frequency when there is a conductor only below the bus bars, but this impact decreases as that conductor is moved farther away from the bus bars (red lines the conductor is very close and the blue lines the conductor is much farther).

Figure 4-4 Straight Bus Bar Error vs Frequency