Patent ID: 8180288

Claim:
A communication system provided with a transmitter for applying a transmission signal to a transmission medium as an electric field, and a receiver for receiving the transmission signal by detecting the electric field via the transmission medium, wherein the receiver includes: a reception electrode located opposite the transmission medium; a resonance circuit provided on the circuit substrate, the resonance circuit being formed of a resonance inductor and a resonance capacitor; a coupling capacitor for capacitively coupling the reception electrode and the resonance circuit, the coupling capacitor having a first electrode at the reception electrode side formed on the circuit substrate; a demodulation circuit side wiring formed on the circuit substrate; and a ground side wiring formed on the circuit substrate; wherein the coupling capacitor is formed by a capacitive coupling between the first electrode at the reception electrode side and the resonance inductor, and has a capacitance which is equal to or smaller than a value of a capacitance between the receiver and the transmission medium when the receiver moves away from the transmission medium up to a maximum distance within which the receiver can perform communication, and wherein the demodulation circuit side wiring and the ground side wiring are formed such that a capacitance between the first electrode and the demodulation circuit wiring becomes larger than the capacitance between the first electrode and the ground side wiring.