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error signal transmission occurred. In the one-point ground mode, each circuit is just grounded only and
they are connected at the same port. Since there is only one common port, there is no circuit and so, there
is no interference.
Multiple-point ground: In the following figure, you can see the internal circuit uses the chassis as the
common point. While at the same time, all devices chassis use the earthing as the common port. In this
connection, the ground structure can provide the lower ground resistance because when there are
multiple-point grounds; each ground cable is as short as possible. And the parallel cable connection can
reduce the total conductance of the ground conductor. In the high-frequency circuit, you need to use the
multiple-point ground mode and each cable needs to connect to the ground. The length shall be less than
the 1/20 of the signal wavelength.
Mixed ground: The mix ground consists of the feature of the one-point ground and multiple-point ground.
For example, the power in the system needs to use the one-point ground mode while the radio frequency
signal requires the multiple-point ground. So, you can use the following figure to earth. For the direct
current (DC), the capacitance is open circuit and the circuit is one-point ground. For the radio frequency
signal, the capacitance is conducive and the circuit adopts multiple-point ground.
When connecting devices of huge size (the device physical dimension and connection cable is big
comparing with the wave path of existed interference), then there are possibility of interference when the
current goes through the chassis and cable. In this situation, the interference circuit path usually lies in the
system ground circuit.
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