In the prior art, a folded antenna 50, for example, shown in FIG. 10 has been introduced as an antenna suitable for transmitting and receiving signals of two or more frequency bands having approximately two times relationship (for example, cf. PATENT DOCUMENT 1). In the folded antenna 50, it is known that resonance at two or more frequency bands having approximately two times relationship can be achieved, since resonance frequencies can be adjusted by arranging intervals between adjacent segments 51, or the like. The antenna of this kind is formed on a surface of a cylindrical base made of, for example, dielectric materials or the like, mounted on a top part of a casing as an antenna for a portable telephone or the like, and used by setting the antenna element 51 located through a certain distance h to a ground face (a ground plate) 52 which is the casing of the portable telephone or the like.
PATENT DOCUMENT 1: Japanese Patent Application Laid-Open No. HEI10-13135