The present invention relates to an antenna for mobile communications and to a radio communication apparatus including it.
Mobile radio communication apparatuses such as portable telephones and pagers are recently used widespread. A mobile radio communication apparatus has a built-in antenna in a case. The mobile radio communication apparatus is a portable telephone with the built-in antenna, e.g. an inverted-F antenna generally used. The portable telephone operates as a complex terminal, thus requiring an antenna desirably transmit and receive signals in plural frequency bands.
FIG. 10 shows a conventional inverted-F antenna. The inverted-F antenna 10 includes a ground plane 11, a conductive radiator 12, a shorting section 14 for short-circuiting the ground plane 11 and the conductive radiator 12, and a feeding section 15 for supplying power to the antenna. This inverted-F antenna has an antenna characteristic of a narrow frequency band as shown in FIG. 9.
A small antenna used for a mobile radio communication apparatus such as portable telephone operates in a broad frequency band and corresponds to plural frequency bands.
The antenna includes a first conductive radiator having a plane shape and a second conductive radiator having a helical shape. A feeding section is made of a planar element, is disposed between the first conductive radiator having the planer shape and a ground plane, and supplies power by electromagnetic coupling, thereby providing the antenna with a broader frequency band.