Capacitive coupling is referred to in electronics as the transfer of a common energy to different devices linked together through an electrical network. The transfer of energy is done by using different capacitors between circuits. It may also be done in sequence to the original power signal that is intended for coupling.
In an analog circuit, the purpose of capacitive coupling is to interrupt a DC circuit, which is why the capacitor used is referred to as a DC-blocking capacitor. In digital circuits, capacitive coupling is most often used in different types of communications devices as a way to block any chance of interference with a signal or to avoid the formation of any type of voltage or power imbalance. These imbalances are often associated with signal amplifiers, especially when the input and output leads couple, which causes what users might hear as feedback.
Capacitive coupling can also occur unintentionally, when a circuit has a frequency running through it and another wire is close in proximity. In such cases, the powered wire may couple with the wire that is projecting bandwidth or frequency and either intercept or simply interfere with the signal of the original wire. The opposite can also occur, wherein the powered wire interferes with the frequency, causing noise or interference with the incoming signal being processed.
When the capacitive coupling occurs on an unintentional basis, usually because two wires powered at different bandwidths or voltages are too close to each other, an unwanted effect called electrical noise occurs. This noise may manifest in either signal interruption of the product’s incoming or outgoing signal or background noises such as high-pitched hissing. Alternatively, the product may simply not work the way it was originally intended. When this occurs in the manufacturing process, most product manufacturers correct the problem by either separating the wires in the wiring schematic or by creating a nonconductive wall between the two wires.
When a coupling effect is desired in an electrical bandwidth device, however, the two wires that would typically be separated are placed within a close proximity of each other. It may also be planned in the schematic that the two wires wind around each other to create the environment where the highest amount of coupling is desired. When the coupling effect is desired between both digital or analog circuits, they are coupled together through the use of capacitors that function separately, depending on whether the signal being powered is digital or analog.
