| 摘要 |
PURPOSE:To perform the separation filtering of a transmission and a reception frequency efficiently without any variation in impedance depending upon the extension and contraction of a rod antenna by matching impedance through a lambda/ 4LC type filter and a band-pass filter. CONSTITUTION:The transmission frequency f1 is attenuated slightly by a receiving lambda/4 tuning filter 3 turned to lambda/4 as large as the wavelength of the reception frequency f2. The band-pass filter 5 tunes to only the f2, so the impedance at a point (b) is zero for the f1 and a short-circuit state is entered, so that the f1 does not enter its reception-side RX. An f2 radiated from a base, on the other hand, etners the band-pass filter 5 through a base lambda/4 tuning filter 2. The band- pass filter 5 tunes to the f2. The f2 from a base point (a) is attenuated through the lambda/4 tuning filter and a leaking f2 is in a short-circuit state. Namely, the filter 4 has zero impedance at a point (c) to the f2, which is cut off. |
