Patent ID: 7242268

Claim:
A balanced-unbalanced multiband filter module comprising a high-frequency antenna switch for switching the connection of an antenna to a transmitting circuit and the connection of said antenna and a receiving circuit and usable in a multiband mobile phone for the pluralities of communications systems using close frequency bands, said balanced-unbalanced multiband filter module comprising three high-frequency switches each comprising a switching element, and two balanced-unbalanced bandpass filters having different transmitting frequency bands, a first high-frequency switch comprising a first port connected to an unbalanced port of said module, a second port connected to an unbalanced port of the first balanced-unbalanced bandpass filter, and a third port connected to an unbalanced port of a second balanced-unbalanced bandpass filter; a second high-frequency switch comprising a first port connected to the first balanced port of said module, a second port connected to the first balanced port of the first balanced-unbalanced bandpass filter, and a third port connected to the first balanced port of the second balanced-unbalanced bandpass filter; and a third high-frequency switch comprising a first port connected to the second balanced port of said module, a second port connected to the second balanced port of the first balanced-unbalanced bandpass filter, and a third port connected to the second balanced port of the second balanced-unbalanced bandpass filter; and being disposed on a transmitting side and/or a receiving side of said high-frequency circuit, on said transmitting side, an unbalanced port of said balanced-unbalanced multiband filter module being connected to a high-frequency amplifier connected to a transmitting port of said high-frequency antenna switch, on said receiving side, an unbalance port of said balanced-unbalanced multiband filter module being connected to a receiving port of said high-frequency antenna switch, and said first and second balanced ports of said module being connected to the balanced ports of said filter module connected to a low-noise amplifier, said first to third high-frequency switches being switched depending on a passing high-frequency signal, whereby a high-frequency signal of the first or second communication system input into an unbalanced port of said module is output to said low-noise amplifier from the first and second balanced ports, and a high-frequency signal of the first or second communication system input into said first and second balanced ports is output to said high-frequency amplifier from an unbalanced port of said module.