| 摘要 |
<p>PROBLEM TO BE SOLVED: To share the high frequency circuit of a mobile machine between the digital automobile telephone system (FDD), the Japanese standard system, and the digital cordless telephone system (TDD). SOLUTION: In FDD, a transmission band (a) and a reception band (b) are used; and in TDD, a band (c) is shared between transmission and reception. An antenna A1 is used for transmission/reception of FDD and transmission of TDD, and an antenna A2 is used for diversity reception of FDD and reception of TDD. Each switch is switched to cope with FDD and TDD. In FDD, reception signals of antennas A1 and A2 are selected by an RBF(reception band filter) 2 and are inputted to a reception amplifier RA, and the output of a transmission amplifier SA is supplied to the antenna A1 through an SBF 2. In TDD, the reception signal of the antenna A2 is selected by an RBF 1 at the reception timing and is inputted to the reception amplifier RA, and the output of the transmission amplifier SA is supplied to the antenna A1 through the SBF 1 at the transmission timing. An SBEF (transmission band elimination filter) taking the reception band (b) as the stop band may be used instead of the SBF 2.</p> |
