JPH01276909A - Television tuner - Google Patents

Abstract

PURPOSE:To improve the disturbance eliminating capacity of a secondary distortion by giving an input signal to a tuning circuit whose parallel resonance circuit consists of a tuning coil component inserted in series with a tuning coil and a reverse bias capacitance of a varactor diode after being led to an impedance conversion circuit comprising a parallel resonance circuit and a coil. CONSTITUTION:Trap capacitors 119, 120 are connected in parallel with tuning coils 11, 14. The input signal is inputted from a terminal 1A. The trap capacitors 119, 120 are capacitors for parallel resonance. The capacitors 119, 120 are inserted in parallel with the tuning coils 11, 14 to attenuate 300-400 bands. Thus the secondary distortion at the reception of 150-440MHz is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a television tuner device used in the field of video equipment.

BACKGROUND OF THE INVENTION In recent years, with the development of television tuner devices (ATVs, etc.), there has been a demand for improvements in interference rejection capability as the number of channels increases.

An example of the above-mentioned conventional television tuner device will be described below with reference to the drawings.

FIG. 2 shows an input filter of a conventional television tuner device. In Figure 2, 2M is an input terminal, 2B is an output terminal, 2C is a first switching potential application terminal, 2
D is a second switching potential application terminal, 2] E is a tuning potential application terminal, 21.22.23.

24. 213, 218 are tuning coils, 26° 210.
214 is a coupling capacitor, 26, 28, 29 is a switch diode, 215, 216, 217 is a variable capacitance diode,
27,211.212. .

219 is a bias resistor.

The operation of the television tuner device configured as described above will be described below.

First, the input signal (VHF) is input from two terminals, but they are divided into three bands, each with two terminals.
The reception band can be set by setting the potential applied to 0.2H as shown in Table 1 below.

[Table 1] First, eoMHz ~ 1soMHzl reception is complete! J.K.
, switch diodes 26, 28, and 29 are all non-conductive. Therefore, the signals are transmitted to the tuning coils 21°, 22.23.
The tuning frequency of the circuit is determined by the tuning capacitance formed by the variable capacitance diode 216, 216, and 24. Tuning capacitance is connected to terminal 2 by variable capacitance diode 21
5, 216.

It is determined by the reverse bias potential applied to 217.

The tuned frequency is supplied from terminal 2B to the next stage high frequency amplification circuit. When receiving 150MHz to 220MHz, only the switch diode 26 is conductive, and the input signal is supplied from the terminal 2B to the next stage at a reception frequency corresponding to the resonance frequency determined by the tuning coils 21, 22゜24 and the resonance capacitance. Ru. In this band, the resonant frequency increases as the number of tuning coils decreases.

220Mflz to 460M11Zf: When receiving, all the switch diodes 26, 28.29 are conductive, so the tuning coils 21.22, 23.24 are bypassed, and only the tuning coil 213 is involved in tuning. Furthermore, the tuning frequency becomes higher.

Problems to be Solved by the Invention However, in the above configuration, 150MHz
~220Mtiz (from 300MHz to 4 when receiving D signal)
In some cases, the 40 MHz band was disturbed by secondary distortion, and the level of commercialization was not reached.

In view of the above problems, the present invention has been developed to
It is an object of the present invention to provide a television tuner device that has the ability to eliminate interference from second-order distortion even when receiving 11z.

Means for Solving the Problems In order to solve the above problems, the television tuner device of the present invention passes an input signal through an impedance conversion circuit including a parallel resonant circuit and a coil, and then converts the parallel resonant circuit into a tuning coil. This configuration uses a tuning circuit consisting of a tuning coil component inserted in series with a variable capacitance diode and a reverse bias capacitance of a variable capacitance diode.

Operation The present invention has the above-described configuration, so that the parallel resonant circuit acts as a trap in the 300 MHz to 440 MtlZO band.
It is possible to improve second-order distortion when receiving a signal.

Embodiment Hereinafter, a television tuner device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an input filter section of a television tuner circuit according to the present invention. In Figure 1, 1M is an input terminal, IB is an output terminal, 1C is a first switching terminal, 1D
is the second switching terminal, 11°12.13,14,113,1
18 is a tuning coil, 15, 110, 114 is a coupling capacitance, 16° 18.19 is a switch diode, 115, 1
16°117 is a variable capacitance diode, 17,111,1
12 is a bias resistor, and 119 and 120 are coils 11.

These are trap capacitors connected in parallel to the coils 14, respectively.

The operation of the input filter device of the television tuner device configured as described above will be described below with reference to FIG.

The input signal is input through terminal 1. The parts in FIG. 1 other than the trap capacitors 119 and 120 are the same as the conventional configuration shown in FIG. 2, and the operation is also the same, so a description of those parts will be omitted to avoid duplication.

Both trap capacitors 119 and 120 are capacitors for parallel resonance. These capacitors 119° and 120 are inserted in parallel with the tuning coils 11 and 14 as described above, and 30°
The 0MH2 to 440Ml1Z band is attenuated. Therefore, it is possible to reduce second-order distortion when receiving frequencies from 150M11Z to 220MHz.

Effects of the Invention As described above, the present invention provides
By installing a resonant capacitor in parallel with the tuning coil used for 0MH2 reception, for example, 300Mtlz to 440Mtlz
It is possible to provide a TVSILON tuner device that can attenuate signal components in the Mflz band and has a high ability to eliminate interference caused by second-order distortion.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a television tuner device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional television tuner device. 11.12,13,14,113,118...
Tuning coil, 15.11Q, 114... Coupling capacitance, 16, 18.19... Switch diode, 115.116, 117... Variable capacitance diode, 119, 120 ...Capacity for trap.

Claims (1)

[Claims] The input signal is divided into three, the first path is grounded via the first parallel resonant circuit and the first coil, and the coupling capacitance and the first path are connected from the intersection of the first parallel resonant circuit and the first coil. The first switch diode and the second coil are connected to the second path from the input terminal through the switch diode and the second coil.
The intersection of the coils is coupled to the variable capacitance diode via the second parallel resonant circuit to form a tuned circuit, and
A third path is grounded via a second switch diode and a third coil, and connected to the second parallel resonance via a third switch diode from the intersection of the second switch diode and the third coil. A television tuner device, characterized in that it is connected to an intersection between a circuit and the variable capacitance diode.