In the mobile telephone field, particularly in Europe, the GSM standard at 900 MHz and the DCS standard at 1800 MHz are known. The frequency bands at which a mobile telephone must radiate, both in transmission and reception, are thus clearly distinct. Moreover, for third-generation mobile telephones, in addition to the PCS standard at 2100 MHz, there is also the UMTS standard at 2200 MHz. In the course of manufacture, mobile telephones must therefore now have available a radiating element, if possible a single one, capable of radiating in these three distinct frequency bands. In passing, it will be noted that the latter bands (1800 MHz to 2200 MHz) form a broad band, in particular by encompassing the DECT standard of 1800 MHz to 1900 MHz.
For complete interactivity of wireless devices, the necessity of satisfying the Blue Tooth standard or the IEEE802.11 standard is now added to the complexity of creating an antenna capable of these three frequency bands. To obtain such a variety of frequencies with a single aerial antenna is a problem that is currently unresolved. We therefore turn to multiple antenna structures.
An antenna permitting radiating in two bands, typically the GSM band at 900 MHz and the DCS band at 1800 MHz, is known from the document of the prior art “Dual-Frequency Planar Inverted-F Antenna”, of Zi Dong Liu and Peter S. Hall in “IEEE Transactions on antennas and propagation,” Vol. 45, No. 10, October 1997, pages 1451 and following. The geometry of the antenna, which is particularly simple and which is envisioned for such a situation of radiation over two bands, has a metallized zone in the shape of the letter L overall and a rectangular metallized area able to be positioned in the open space of the L shape. On the one hand, this solution has separate feeds for the different antenna elements so that switching circuits must be added to the electronic circuit to which this antenna is coupled. These switching elements themselves create operating difficulties. On the other hand, high bands such as UMTS and very high bands such as Blue Tooth are not possible with such a network.
Such solutions are therefore poor. They require connection switches, which generate problems for transmission or reception.