| 摘要 |
PROBLEM TO BE SOLVED: To provide a multi-frequency branching filter that is more downsized than a conventional multi-frequency branching filter without deteriorating its electric characteristic and can reduce its loss. SOLUTION: The multi-frequency branching filter has a 1st band pass filter that passes a 1st high frequency signal with a wavelength ofλL, a 2nd band pass filter that is connected to a common terminal via a transmission line and passes a high frequency signal with a 2nd frequency higher than the 1st high frequency and whose wavelength isλHL, and a 3rd band pass filter that is connected to the common terminal via the transmission line and passes a high frequency signal with a 3rd frequency higher than the 2nd frequency and whose wavelength isλHH. The length of a coupling line in the 1st band pass filter is (λHL+λHH /8, the length of a coupling line in the 2nd band pass filter is (λHH/4), the length of a coupling line in the 3rd band pass filter is (λHL/4), and the length of the transmission line is (λLL/4)-(λHH/4).
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