Patent ID: 7439933

Claim:
A signal processing circuit comprising an IC including an RF circuit and a rectangular spiral antenna being a planar coil and communicating by using at least two carrier frequencies; wherein when the two carrier frequencies are taken as f 1 and f 2 (where, f 1 <f 2 ) and wavelengths corresponding to the carrier frequencies f 1 and f 2 are taken as λ 1 and λ 2 (where λ 1 >λ 2 ) respectively, the line length L of the rectangular spiral antenna satisfies a relationship of L<<λ 1 , and the outer and the inner dimension L xo and L xl in the longitudinal direction of the antenna and the outer and the inner dimension L yo and L yi in the widthwise direction thereof satisfy a relationship of 2×( L xi +L yi )<λ 2 <2×( L xo +L yo ).