Patent ID: 8190086

Claim:
A transmission method of performing a signal transmission in a non-contact manner through an electromagnetic induction based on a magnetic field signal output by a transmission coil, wherein said transmission coil outputs a triangular or roughly triangular magnetic field signal; said magnetic field signal is generated by providing said transmission coil with a current signal shaped through current switch processing performed by a transmission circuit connected to said transmission coil; said current switch processing is performed by a circuit which comprises a plurality of variable current sources and a plurality of switches connected to said variable current sources respectively; said plurality of variable current sources have the same current flowing through each of the variable current sources: said current signal is generated by adding currents from the variable current sources, which are connected to the switches that are turned on, from among the plurality of variable current sources; said plurality of switches open and close, such that an absolute value of the amount of current of the current signal becomes a minimum value at the start of a single data width of a transmission signal, then the absolute value gradually becomes greater in accordance with a time course, then the absolute value becomes a maximum value at a center of the single data width, then the absolute value gradually becomes smaller in accordance with the time course, then the absolute value becomes the minimum value at the end of the single data width; and said transmission circuit changes the direction of the current signal, which flows through the transmission coil, in accordance with changing a data level of the transmission signal.