Patent ID: 8188933

Claim:
An antenna unit, comprising: a coil section formed on a magnetic sheet; a transmission circuit in which an inductor, a first capacitor, and the coil section are connected in series; and a reception circuit in which the coil section, the first capacitor, a resistance part, and a second capacitor are connected in series; wherein the coil section is formed as one turn and the size of the coil and the resistance part involves the following relationship: R =( S×μe×H×Q× 2 πf ) 2 /W where S: Product of dimensions of length and width of the coil section, R: Resistance value of the resistance part, W: Drive power at the IC chip receiving time, H: Magnetic field strength in the coil section, Q: Antenna performance, μe: Effective magnetic permeability of the magnetic sheet, and f: Frequency at the transmitting-receiving time.