In capacitive coupling, it is the electric field imposed between an external pair of conductors or TX electrodes that induces displacement currents travelling all the way (or partly) in the direction of the RX electrodes on the body, without requiring any physical medium for signal propagation, as opposed to conduction currents (Figure 2 B).
Usually, the capacitive coupling of a CPT system is represented as a pair of capacitors in series as shown in Figure 3. However, this representation is not always suited for simulation purposes. First, it makes it difficult to analyze primary and secondary sides separately as they are connected by the equivalent coupling capacitor.
Coupling capacitors (or dc blocking capacitors) are use to decouple ac and dc signals so as not to disturb the quiescent point of the circuit when ac signals are injected at the input. Bypass capacitors are used to force signal currents around elements by providing a low impedance path at the frequency.
Every load change changes the voltage output of the compensation circuit which may cause the capacitive coupling to become less effective. A solution for variable capacitive coupling, e.g., variable charging distance, in is suggested.
A coupling capacitor's ability to prevent a DC load from interfering with an AC source is particularly useful in Class A amplifier circuits by preventing a 0 volt input being passed to a transistor with additional resistor biasing; creating continuous amplification.
An equivalent couplin g capacitor is made up of electrical poles, clothing and human skin. As is shown in Figure 4. Through th e coupling of capacitance, the electrical signals on the skin surface are transmitted to the pad of capacitively coupling electrode.