| 摘要 |
PROBLEM TO BE SOLVED: To improve Tx-Rx isolation characteristics in both a frequency band having narrow Tx-Rx separation and a frequency band having wide Tx-Rx separation in the tunable filter of a mobile communication terminal.SOLUTION: The attenuation areas of a Tx filter and an Rx filter possessed by a tunable filer incorporating an antenna terminal, a Tx terminal and an Rx terminal are both made to be high impedance. The Rx filter is placed at the initial stage of a canceller and the Tx filter is placed at the last stage of the canceller. The Tx terminal and the Rx filter of the canceller are connected, and the Rx terminal and the Tx filter of the canceller are connected. A notch filter or a band-pass filter is placed between the Tx terminal and a PA output terminal and between the Rx terminal and an LNA input terminal, respectively. |
