| 摘要 |
PROBLEM TO BE SOLVED: To provide a protection circuit which reduces the size of a high-frequency circuit and reduces a power loss of a high-frequency signal while at the same time protecting the high-frequency circuit against overinput of high-frequency signal power. SOLUTION: The protection circuit comprises a 3/4 wavelength transmission line 13 whose electric length is 3/4 the wavelength of a high-frequency signal and which is arranged on a dielectric substrate; first and second terminal circuits which can be connected to both ends of the 3/4 wavelength transmission line; and a 1/4 wavelength transmission line 12 which transmits high-frequency signals and has a closed zone length which can be connected to each end of the 3/4 wavelength transmission line and the first and second terminal circuits via an RF-MEMS switch which is 1/4 the wavelength of a high-frequency signal. When the high-frequency power does not exceed a threshold value, the RF-MEMS switch does not connect the 1/4 wavelength transmission line to both ends of the 3/4 wavelength transmission line and the first and second terminal circuits, and when the high-frequency power exceeds the threshold value, the RF-MEMS switch connects the 1/4 wavelength transmission line to both ends of the 3/4 wavelength transmission line and the first and second terminal circuits to attenuate the high-frequency power. COPYRIGHT: (C)2008,JPO&INPIT
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