| 摘要 |
An antenna input circuit for an electronic tuning type AM receiver for automobiles, which is connected to a capacitive antenna represented by an equivalent circuit composed of an antenna capacitance connected in series with an antenna electromotive force and a cable capacitance connected in parallel with them. A tuning transformer and a variable capacitance diode are connected in series with the capacitive antenna, and an additional capacitance is connected to the tuning transformer so that the current flowing in the additional capacitance also flows in one part of the tuning transformer, thereby providing an improved S/N ratio in the medium-frequency receiving band. Another capacitance is connected to the output terminal of the antenna input circuit, to reduce its output impedance. A capacitance for image interference ratio improving use is connected to the additional capacitance and the output impedance reducing capacitance. |
