| 摘要 |
PROBLEM TO BE SOLVED: To widen the tuning frequency range of an UHF input tuning circuit without using any expensive and special varactor diode. SOLUTION: A tuner is equipped with an inductance element 3a and a tuning varactor diode which is applied with a tuning voltage at its cathode and connected in parallel to the inductance element in terms of high frequency; and the tuning varactor diode is composed of two varactor diodes 3b and 3c which have their cathodes connected to each other and one end of the inductance element 3a is grounded in terms of high frequency by a DC cutting capacitor 3f. The anode of one tuning varactor diode 3b is connected to the other end of the inductance element 3a and also connected to the anode of a switch diode 2f in terms of direct current, and the anode of the other varactor diode 3c is grounded by a capacitor 3d for tuning frequency correction and also connected to the connection point between the inductance element 3a and DC cutting capacitor 3f by a resistance 3e.
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