JPS63121978U

JPS63121978U -

Info

Publication number: JPS63121978U
Application number: JP1395987U
Authority: JP
Priority date: 1987-02-02
Filing date: 1987-02-02
Publication date: 1988-08-08

Description

[Brief explanation of the drawing]

第１図は、本考案のテレビチユーナのＦＭ放送
帯域減衰回路の一実施例の回路図であり、第２図
は、第１図の減衰特性を示す図であり、第３図は
、本考案の他の実施例の回路図であり、第４図は
、第３図の減衰特性を示す図であり、第５図は、
アメリカで使用されるテレビチユーナのブロツク
回路図であり、第６図は、従来のテレビチユーナ
のＦＭ放送帯域減衰回路の回路図であり、第７図
は、第６図の減衰特性を示す図である。４０：信号線路、４１：第１の可変容量ダイオ
ード、４５：並列共振回路、４７：第２の可変容
量ダイオード、４９：直列共振回路、５０，５１
，５３〜５６，５８，５９：抵抗、５２：第１の
制御電圧端子、５７：第２の制御電圧端子。 FIG. 1 is a circuit diagram of an embodiment of the FM broadcast band attenuation circuit of the television tuner of the present invention, FIG. 2 is a diagram showing the attenuation characteristics of FIG. 1, and FIG. FIG. 4 is a diagram showing the attenuation characteristics of FIG. 3, and FIG. 5 is a circuit diagram of another embodiment.
6 is a block circuit diagram of a television tuner used in the United States, FIG. 6 is a circuit diagram of an FM broadcast band attenuation circuit of a conventional television tuner, and FIG. 7 is a diagram showing the attenuation characteristics of FIG. 6. 40: Signal line, 41: First variable capacitance diode, 45: Parallel resonant circuit, 47: Second variable capacitance diode, 49: Series resonant circuit, 50, 51
, 53 to 56, 58, 59: resistor, 52: first control voltage terminal, 57: second control voltage terminal.

Claims

[Claims for Utility Model Registration] (1) A parallel resonant circuit including a first variable capacitance diode is interposed in the signal line, and a series resonant circuit including a second variable capacitance diode is interposed between the signal line and ground. F in these parallel and series resonant circuits.
An FM broadcast band attenuation circuit for a television tuner, characterized in that the FM broadcast band attenuation circuit for a television tuner attenuates the M broadcast band and applies control voltages to the first and second variable capacitance diodes through high resistances. (2) The control voltage applied to the first control voltage terminal is divided by a high resistance and applied to the first variable capacitance diode, and the control voltage applied to the second control voltage terminal is applied to the second variable capacitance diode. The first and second control voltage terminals are connected by a resistor, and the same voltage is selectively applied to either one of the first and second control voltage terminals. An attenuation circuit for an FM broadcast band of a television tuner according to claim 1, characterized in that a control voltage is applied thereto.