PURPOSE: To obtain sufficient attenuation at the transmission band and also to reduce the insertion loss by providing a tuning circuit resonated at the transmission frequency and whose resonance frequency follows up the transmission frequency to an output side of a reception filter.
CONSTITUTION: An output terminal of a band pass filter 32 is provided with a tuning series resonance circuit 35 and the resonance frequency is made coincident with the transmission frequency, then an attenuation pole 41 is provided to the transmission band. Although the attenuation pole has a narrow band, a sufficient attenuation characteristic is obtained. Since the band is narrow, the insertion loss is decreased. Since the resonance frequency of a resonance circuit 35 follows up the transmission frequency, even if the attenuation pole itself has a narrow band, sufficient attenuation characteristic is given over the entire transmission band. Thus, sufficient attenuation is obtained at the transmission band and also the insertion loss is reduced.
SAGAWA MORIKAZU
YAMASHITA SADAHIKO
| JPS59232A | 1984-01-05 | |||
| JPS54148313A | 1979-11-20 | |||
| JP57204747B |