| 摘要 |
The present invention provides a thin film balun capable of preventing a resonant frequency from being increased to a high frequency due to size and thickness reductions and maintaining a preferable passage characteristic, while improving a balance characteristic. A thin film balun 1 includes: an unbalanced transmission line 2 having a first coil portion C1 and a second coil portion C2; and a balanced transmission line 3 having a third coil portion C3 and a fourth coil portion C4 which are magnetically coupled with the first coil portion C1 and the second coil portion C2, respectively. The first coil portion C1 is connected to an unbalanced terminal T0, and the second coil portion C2 is connected to a ground terminal G (ground potential) via a capacitor D (C component). The third coil portion C3 is connected to a balanced terminal T1 and the fourth coil portion C4 is connected to a second balanced terminal T2. At least a part of the capacitor D is contained in a second magnetic coupling area R2 formed by the coil portions C2 and C4.
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