| 摘要 |
PURPOSE:To obtain an antenna inputting circuit which is good in a sensitivity characteristic and image and spurious disturbance characteristics by providing a resonance circuit just behind an antenna terminal and in front of a high frequency amplifier, respectively, and connecting both the resonance circuits by a parallel conductor. CONSTITUTION:The first resonance circuit 5 which is provided just behind an antenna terminal 1, and the second resonance circuit 6 which is provided in front of a high frequency amplifier 2 are the LC parallel resonance circuit of a capacitor C1 and the inductance L1 and the LC series resonance circuit of an inductance L2 and a capacitor C2, respectively, and the resonance circuit 5 and 6 are connected by a parallel conductor 4 of + several cm. A capacitor C3 connected to both ends of the rear part of the parallel conductor 4 sets a constant so as to obtain a band pass characteristic by the two resonance circuits 5, 6 and the parallel conductor 4. In such a manner, even if the antenna terminal and the front end are separated from each other, a good band pass characteristic can be obtained without using a coaxial cable, and also the characteristic of a spurious disturbance, etc. can be improved. |
