Folded antenna

A folded antenna comprising:

• a dielectric base;
• a ground conductor film which is provided on at least a part of one surface of the dielectric base as a ground plate;
• and
• an antenna element having a plurality of turning parts and a plurality of segments formed between the turning parts, the segments being formed by being turned back in a zigzag manner in parallel to an end face of the ground conductor film at the turning parts, the antenna element extending perpendicularly to the end face of the ground conductor film,
• wherein a length of one segment or a length of a set of segments, which is a pair of arbitrary two adjacent segments having the same length, is shorter on a side of the ground conductor film and increases gradually as the segment or the set of segments is away from the ground conductor film, and
• wherein the antenna element is formed such that the folded antenna resonates at two or more frequency bands and has a fractional bandwidth of 4% or more of a frequency in a first frequency band and a fractional bandwidth of 15% or more of a frequency in a second frequency band, by adjusting lengths of the segments or sets of segments having the same length, and intervals between adjacent segments, and a face opposed to the antenna element is free of any ground conductor.