How to avoid ground loops in a concentrator with mixed grounding?

In concentrator systems, low-frequency circuits require single-point grounding, while high-frequency circuits and shielding layers require multi-point grounding. A hybrid grounding strategy resolves this conflict and avoids ground loops. For the signal cable shielding layer, a capacitor (e.g., 1nF/2kV) is connected to the chassis ground at the concentrator end to achieve high-frequency multi-point grounding; simultaneously, a 100kΩ resistor is connected in parallel with a CMZ2012A-900T common-mode inductor to the internal signal ground to achieve low-frequency single-point grounding.

On the PCB, analog circuits use a single-point star grounding, while digital circuits use a grid ground plane, connected at one point via a PBZ1608E600Z0T ferrite bead. The power ground (PGND) is directly connected to the chassis ground through a 0Ω resistor. This structure prevents power frequency ground loop currents and provides a low-impedance discharge path for high-frequency noise. Hybrid grounding can reduce the noise voltage induced by ground loops on signal lines by 40dB, while ensuring that the shielding layer's ground impedance is less than 1Ω at 100MHz.