Reception antenna, core, and portable device

A core around which electric wire is wound to form each of three antenna coils, the core that has a shape of at least one of a cylinder and a prism whose section is symmetrical to a point where a center axis of the core passes through, the core comprising:

• a first groove member that is formed on a surface of the core and orbits along a perimeter of a first virtual sectional plane, which includes the center axis of the core;
• a second groove member that is formed on the surface of the core and orbits along a perimeter of a second virtual sectional plane, which includes the center axis of the core, wherein the second virtual sectional plane is orthogonal to the first virtual sectional plane;
• and
• a third groove member that is formed on the surface of the core and orbits along a perimeter of a third virtual sectional plane that is orthogonal to the central axis, the perimeter of the third virtual sectional plane is on a curved surface that is disposed between base surfaces of the core, the base surfaces which are symmetrical to the point where the center axis passes through.

A portable device comprising:

• a reception antenna-that includes,
• three antenna coils whose center axes mutually orthogonally intersect at an intersecting point and each of which is symmetrical to the intersecting point;
• and
• a core around which electric wire is wound to form each of the three antenna coils,
• wherein a first antenna coil of the three antenna coils is most inwardly formed and a third antenna coil is most outwardly formed,
• wherein a second antenna coil is formed between the first antenna coil and the third antenna coil,
• wherein the second antenna coil and one of the first antenna coil and the third antenna coil- constitutes a pair of selected antenna coils, and
• wherein a terminating end of winding electric wire of an inwardly-located antenna coil of the pair of the selected antenna coils is connected with a starting end of winding electric wire of an outwardly-located antenna coil of the pair of the selected antenna coils;
• a reception circuit that receives, through the three antenna coils, a signal to demodulate into a digital signal;
• and
• a control circuit that executes a control based on the digital signal demodulated in the reception circuit.