1. Field of the Invention
This invention relates to a chip antenna used for electronic equipment with a communication function, such as cellular phone, personal digital assistant equipment. Furthermore, this invention relates to an antenna system and communication equipment using this chip antenna.
2. Description of the Related Art
The frequency range in communication equipment, such as a cellular phone and wireless LAN, ranges from hundreds of MHz to several GHz. It is required for this frequency range to be wide and for the efficiency in this range to be high. Therefore, the antenna used for this communication equipment also needs to be high gain in this frequency range, it is needed to be small and to be thin also. In the ground digital broadcasting started in recent years, the frequency range in the television broadcasting in Japan is 470 MHz-770 MHz, for example. When it corresponds to all the channels, it is required that this antenna can receive such a wide frequency range. Conventionally, a chip antenna using dielectric ceramics as a small antenna suitable for mobile communications has been offered (for example, see Japanese Patent No. H10-145 123). When setting frequency constant, miniaturization of a chip antenna can be attained by using dielectrics with a higher dielectric constant. In art given in this document, this wavelength is shortened by providing a meander shaped electrode. Moreover, the antenna aiming at miniaturization is also proposed by shortening a wavelength 1/(εr·μr)1/2 times using the magnetic material with large relative permittivity εr and large relative magnetic permeability μr (for example, see Japanese Patent No. S49-40046).
Moreover, for example with a small liquid crystal television, the whip antenna using the metal stick is generally used as a receiving antenna currently used for television or radio. This system is beginning to be used also for the cellular phone with television function. Furthermore, the electric wire which is a part of earphones used with a cellular phone, may be used as a receiving antenna of radio or television.
Although the above-mentioned dielectric chip antenna is advantageous for a miniaturization and thinning, there are the following problems to making bandwidth of a frequency range wide. For example, when using a helical-type radiation electrode as an electrode, if a number of turns increases, the capacitance between electric wires will increase and Q value will become high. Therefore, bandwidth becomes narrow and it becomes difficult to apply to uses, such as ground digital broadcasting as which wide bandwidth is required.
Making bandwidth wide and a miniaturization, are possible, with the above-mentioned magnetic material chip antenna. However, the mounting space for electronic parts in communication equipment, especially in portable communication equipment, is restricted. Therefore, it is further necessary to reduce the mounting space which an antenna occupies. However, this chip antenna is generally making rectangular parallelepiped shape, and its size is also large compared with other electronic parts. Therefore, it may be unable to be mounted efficiently spatially.
For example, generally the case of a cellular phone has curved surface shape. Therefore, when arranging the chip antenna of rectangular parallelepiped shape at the end of a case, a spatial loss may arise.
So, this invention aims at offering a chip antenna suitable for efficient mounting within communication equipment in this invention. Also it aims at offering the antenna system and communication equipment using this chip antenna.