Reader/writer having coil arrangements to restrain electromagnetic field intensity at a distance

A reader/writer comprising:

• a power supply portion which generates a voltage as a power transmission signal to be supplied to an IC card;
• an encoder circuit which encodes an input communication data and outputs an encoded communication signal to be transmitted to the IC card;
• an amplitude-modulator which superimposes a signal being amplitude modulated by the encoded communication signal outputted from said encoder circuit on the signal generated from said power supply portion and outputs an amplitude-modulated signal;
• a feeding circuit which feeds the amplitude-modulated signal outputted from the amplitude-modulator as a current signal;
• an antenna which generates an electromagnetic wave to perform transmission of both operating power and communication to the IC card;
• and
• wherein said antenna comprises a main coil which generates an electromagnetic field used for transmission of both said operating power and said communication by feeding the current signal from the feeding circuit and a plurality of auxiliary coils which are disposed with substantially symmetry with respect to said main coil and which generate axial magnetic fields in a direction opposite to a magnetic field generated by said main coil by feeding the current signal from the feeding circuit to thereby restrain an intensity of the electromagnetic field at a distance.

A reader/writer comprising:

• a power supply portion which generates a voltage as a power transmission signal to be supplied to an IC card;
• an encoder circuit which encodes an input communication data and outputs an encoded communication signal to be transmitted to the IC card;
• an amplitude-modulator which superimposes a signal being amplitude-modulated by the encoded communication signal outputted from said encoder circuit on the signal generated from said power supply portion and outputs an amplitude-modulated signal;
• a feeding circuit which feeds the amplitude-modulated signal outputted from the amplitude-modulator as a current signal;
• an antenna which generates an electromagnetic wave to perform transmission of both operating power and communication to the IC card;
• and
• wherein said antenna comprises a main coil which generates an electromagnetic field used for transmission of both said operating power and said communication by feeding the current signal from the feeding circuit and a plurality of auxiliary coils which are disposed with substantially symmetry with respect to said main coil and which generate magnetic fields by feeding the current signal from the feeding circuit so as to restrain an intensity of the electromagnetic field at a distance.

A reader/writer comprising:

• a power supply portion which generates a voltage as a power transmission signal to be supplied to an IC card;
• an encoder circuit which encodes an input communication data and outputs an encoded communication signal to be transmitted to the IC card;
• an amplitude-modulator which superimposes a signal being amplitude-modulated by the encoded communication signal outputted from said encoder circuit on the signal generated from said power supply portion and outputs an amplitude-modulated signal;
• a feeding circuit which feeds the amplitude-modulated signal outputted from the amplitude-modulator as a current signal;
• an antenna which generates an electromagnetic wave to perform transmission of both operating power and communication to the IC card;
• and
• wherein said antenna comprises a main coil which generates an electromagnetic field used for transmission of both said operating power and said communication by feeding the current signal from the feeding circuit and a plurality of auxiliary coils which are disposed with substantially symmetry for said main coil and which generate magnetic fields by feeding the current signal from the feeding circuit so as to enlarge an area extending in a traverse direction of a magnetic-field intensity distribution being generated by said main coil.

A reader/writer comprising:

• a power supply portion which generates a voltage as a power transmission signal to be supplied to an IC card;
• an encoder circuit which encodes an input communication data and outputs an encoded communication signal to be transmitted to the IC card;
• an amplitude-modulator which superimposes a signal being amplitude-modulated by the encoded communication signal outputted from said encoder circuit on the signal generated from said power supply portion and outputs an amplitude-modulated signal;
• a feeding circuit which feeds the amplitude-modulated signal outputted from the amplitude-modulator as a current signal;
• a spiral antenna which generates an electromagnetic wave to perform transmission of both operating power and communication to the IC card;
• and
• wherein said spiral antenna has a plurality of portions having phase inverse portions of current distribution by reversing direction of turning of said spiral antenna by feeding the current signal from the feeding circuit so that a current flowing in each of said portions has a reverse phase with each other, and an axial magnetic field being generated by flowing the current in each of portions is identical in phase with each other.