| 摘要 |
PROBLEM TO BE SOLVED: To reduce a cost by a method wherein the mutual transformation between a balanced state and an unbalanced state is realized with a simple structure and the structure is shared for a receiving mode and a transmission mode. SOLUTION: A balanced double-tuning circuit 3 is provided between a switching circuit 2 and a receiving circuit 4/a transmission circuit 5, the double- tuning circuit 3 is approximately tuned with frequencies of a receiving signal and a transmission signal, and the receiving circuit 4 and the transmission circuit 5 are connected in parallel with the secondary tuning circuit 3s of the double-tuning circuit 3. In a receiving mode, one end 3p1 of a primary tuning circuit 3p of the double-tuning circuit 3 is connected to the a signal I/0 terminal 1 and the other end 3p2 is grounded by the switching circuit 2 and, in a transmission mode, the one end 3p1 is grounded and the other end 3p2 is connected to the signal I/0 terminal 1 by the switching circuit 2.
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