# Shielding Grounding Optimization Method for Spaceborne Multi-Cable
## 4 Results and Analysis
### Interference Path Analysis  
Path 1 in Figure 9 shows the flow of interference signals when the near end of the angle measurement cable shield is grounded. Each device is connected to the same reference ground, and since the actual grounding is not fully ideal, the interference is not immediately released through the ground, and various parts of the system are coupled to each other. When one end of the angle measurement cable shield is grounded, it is subject to interference from the motor side, the circuit box side, other cables, and many other  
Figure 8: Scanning mirror angle accuracy test results for 64 states: (“unable to point” means that the interference has increased to such a high level that the scanner cannot complete the pointing command and thus cannot measure the angle accuracy). sources. The interference flows into the angle measurement cable shield and affects the inner core of the cable, resulting in too much interference in the inner core and making the scanner unable to complete the pointing command, as shown in accuracy level 3 in Figure 8. Additional experimental testing also proved the following explanation: For the near end of the angle measurement cable shield ground, \(R_{AN}\) needs to be increased to 1 k\(\Omega\) from 0 \(\Omega\), and the scanner can then complete the fixed-point pointing command. At this point, if the near end of the motor drive cable shield is grounded, then \(R_{AN}\) needs to be increased to 2 k\(\Omega\), and the scanning mirror can then complete the fixed-point pointing command. At this point, if the field excitation cable shield is grounded near the end, \(R_{AN}\) needs to be increased to 3 k\(\Omega\) for the scanning mirror to complete the pointing command. As more equipment grounding leads to greater interference in the shield of the angle measurement cable, the increase in \(R_{AN}\) can reduce the interference signal on the shield, which in turn reduces the interference in the core of the angle measurement cable. When \(R_{AN}\) increases to infinity, which is equivalent to no grounding, the angle accuracy becomes smaller, as shown in accuracy level 1. Path 2 in Figure 10 shows the flow of interference signals when the near end of the driver cable shield is grounded. Due to the high voltage and frequency of the drive signal, a large source of interference is generated on its shield, which is externally released through the coupling path, including flowing to the ground plane of the PCB inside the circuit box and on the shield of other cables. This results in poorer angle accuracy when at least one end of the motor drive cable shield is grounded compared to when the motor drive cable shield is not grounded, as shown for accuracy level 2 in Figure 8.  
Figure 10: Schematic diagram of the motor drive cable releasing interference to the outside. Figure 9: Schematic diagram of the angle measurement cable subject to external interference. The error states 10 and 14 in Figure 8 should theoretically have a level 2 angle accuracy, but the actual scanning mirror cannot complete the fixed-point pointing command. The reason for this could be that states 10 and 14 correspond to \"001001\" and \"001101\", respectively, which means that the angle measurement cable shield is not grounded, the near end of the motor drive cable shield is grounded, and the far end of the field excitation shield is grounded; therefore, the scanning mirror cannot complete the fixed-point pointing command. Figure 10 shows that the interference path flows to the branch of the induction synchronizer. The sending end of the drive signal is on the circuit box side, and the near end has a larger interference signal. The receiving end of the field excitation cable signal is on the side of the scanning mirror mechanism, and this end is more susceptible to interference. The interference on the shield of the motor drive cable affects the induction synchronizer on the mechanism side, which in turn affects the angle measurement signal.