| 摘要 |
PURPOSE:To attain effective tracking adjustment by correcting the capacitance characteristic of a varactor diode of a main tuning circuit in response to the decreasing change in a channel selection voltage through the provision of a voltage variable circuit. CONSTITUTION:An antenna circuit is formed by a main tuning circuit 1 and an auxiliary tuning circuit 4 using varactor diodes 2, 6 respectively as variable tuning components, and a voltage variable circuit 7 is connected to the circuit 1. If the channel selection voltage applied to the cathode of the diode 2 of the circuit 1 is decreasing at a small voltage region, a transistor 9 of the circuit 7 is operated and the potential of the anode of the diode 2 is changed in the increasing direction. Thus, the apparent channel selection voltage is lowered and the deficiency of the combined capacitance by the circuits 1, 4 is corrected and the change in the combined capacitance is increased, the linearity of the combined capacitance characteristic is maintained to apply effective tracking adjustment.
|
