Television tuner for balance-inputting signal to balanced mixer

• US 20050190305A1
• Filed: 02/17/2005
• Published: 09/01/2005
• Est. Priority Date: 02/26/2004
• Status: Active Grant

• Current Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Yamamoto, Masaki
• Granted Patent: US 7,365,804 B2
• Time in Patent Office: Days
• US Class Current: 348/731
• CPC Class Codes: H03J 3/08 by varying a second parameter simultaneously with the tuning, e.g. coupling bandpass filter
• CPC Class Codes: H03J 3/20 of single resonant circuit by varying inductance only or capacitance only

Abstract

A television tuner includes an unbalanced tuning circuit and a balanced mixer provided at the next stage of the tuning circuit. An output port of the tuning circuit is grounded through a serial circuit composed of an inductive element and a capacitive means. The output port of the tuning circuit is connected to one input port of the mixer. A connection point provided between the inductive element and the capacitive means is connected to the other input port of the mixer. This permits phases of the signals input to two input ports of the mixer to be inverted to each other.

Claims

1. A television tuner comprising:

an unbalanced tuning circuit; and

a balanced mixer provided at a next stage of the tuning circuit,

wherein an output port of the tuning circuit is grounded through a serial circuit composed of an inductive element and a capacitive means having a variable capacitance value, the output port of the tuning circuit is connected to one input port of the mixer, and a connection point provided between the inductive element and the capacitive means is connected to another input port of the mixer.

2. The television tuner according to claim 1,

wherein the inductive element is provided at an output port side of the tuning circuit, the capacitive means is provided at a ground side, and a serial resonance frequency of the inductive element and the capacitive means is lower than a frequency of a signal input to the mixer from the tuning circuit.

3. The television tuner according to claim 1,

wherein the capacitive means is provided at an output port side of the tuning circuit, the inductive element is provided at a ground side, and a serial resonance frequency of the inductive element and the capacitive means is higher than a frequency of a signal input to the mixer from the tuning circuit.

4. The television tuner according to claim 2,

wherein a capacitance value of the capacitive means decreases as a tuning frequency of the tuning circuit increases.

5. The television tuner according to claim 4,

wherein the tuning circuit includes a first varactor diode applied with a tuning voltage for changing the tuning frequency, the capacitive means includes at least a second varactor diode, and the second varactor diode is applied with the tuning voltage.

6. The television tuner according to claim 5,

wherein the capacitive means includes a capacitance element serially connected to the second varactor diode.

7. The television tuner according to claim 3,

wherein a capacitance value of the capacitive means decreases as the tuning frequency of the tuning circuit increases.

8. The television tuner according to claim 7,

wherein the tuning circuit includes a first varactor diode applied with a tuning voltage, for changing the tuning frequency, the capacitive means includes at least a second varactor diode, and the second varactor diode is applied with the tuning voltage.

9. The television tuner according to claim 8,

wherein the capacitive means includes a capacitance element serially connected to the second varactor diode.