JPH01170212A - Electronic tuner - Google Patents

Abstract

PURPOSE:To reduce the coupling due to stray capacitance between tuning circuits by constituting the tuner by a VHF circuit or a UHF circuit where variable capacitance diodes are composed to be stored into one package and the polarity of the variable capacitance diodes is arranged opposite. CONSTITUTION:The variable capacitance diodes A-G being tuning variable elements of an electronic tuner provided with a high frequency amplifier circuit, a mixing circuit and a local oscillation circuit are made composite and stored in one package. In this case, the polarity of the variable capacitance diodes arranged side by side are located to be opposite without fail. Through the constitution above, the stray capacitance between adjacent cathodes of the variable capacitance diodes A-G is negligible. Then, the coupling between hot points of each tuning circuit due to stray capacitor can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electronic tuning tuner for televisions and VTRs using varicap diodes.

(Prior Art) In recent years, electronic tuning tuners for televisions and VTRs have entered an era of becoming lighter, thinner, and smaller, and are becoming increasingly smaller, multifunctional, and diversified. In particular, the trend toward miniaturization of portable type displays has become more compact due to advances in display technology, which have led to liquid crystal displays.
They are becoming thinner. Naturally, the parts used need to respond to the need for miniaturization, and electronic tuning tuners for televisions are also desired to be smaller and thinner than before, especially for portable TV tuners. They are becoming even more powerful, and we are currently pushing the circuit configuration to its limits, reducing the number of parts, and converting all parts into chips in order to make them significantly thinner.

Conventionally, this type of electronic tuning tuner is shown in Fig. 3(a), (
The configuration was as shown in b). FIG. 3(a) shows a standard tuner circuit, and FIG. 3(b) shows a circuit configuration of a low-cost tuner. Conventionally, varicap diodes used in electronic tuning tuners are used in each tuning circuit, that is, in the input tuning circuit 11, the interstage double tuning circuit 29, and the local oscillation circuit 3.Moreover, the varicap diodes used in the same tuner are as follows: Reverse voltage vs. capacitance characteristics must be aligned within a limited tolerance range.

Therefore, in terms of mounting, the components supplied in pairs from the manufacturer must be mounted on the board one by one without breaking the pairs, which increases the amount of management man-hours during the manufacturing process.

The current situation is that the number of man-hours required for mounting is significantly greater than for general parts.

Varicap diodes are used as variable capacitors in each tuned circuit, as shown in Figures 4 and 5, but generally the cathode side is connected to the hot point of each tuned circuit. The circuit is configured in this state. In other words, the original performance of the tuner (for example, leakage of local components to the antenna terminal, stable operation of the amplifier circuit, Although this is an extremely important and basic design concept to ensure performance (such as selectivity), the conventional method shown in Figure 2, that is, packaging each varicap diode in the same direction. The reality is that the methods that do this do not provide sufficient characteristics regarding the performance of the above-mentioned content.

In addition, the mounting method requires that the diodes supplied in pairs from the manufacturer be mounted one by one on the mounting board without breaking the pair, which requires less management and mounting time in the production process than for varicap diodes. It cost a lot more than parts. For the purpose of this improvement, four to three varicap diodes that function as variable capacitance elements of each tuning circuit shown in Figs. 4 and 5 are enclosed in one package as shown in Fig. 2. It has been used as This was mainly aimed at improving the manufacturing process and downsizing.

(Problems to be Solved by the Invention) In such a conventional configuration, each tuning circuit has a stray capacitance Jt (
a) (Fig. 2), there was a problem in that electrical coupling was easy to occur. That is, each tuning circuit of an electronic tuning tuner is generally constructed such that the cathode side is the hot point of each tuning circuit, as shown in FIGS. 4 and 5. However, in the conventional encapsulated state of varicap diodes as shown in FIG. 2, the hot points of each tuning circuit are coupled due to the stray capacitance between the terminals of each varicap diode. This stray capacitance is unavoidable in a type that encapsulates a varicap diode in the same package.

As a result of this, due to the coupling between the tuned circuit of the oscillator circuit and the input tuned circuit close to the antenna.

There was a problem of deterioration due to leakage of oscillation frequency components to the antenna.

Furthermore, there is a problem in that the amplification operation of the high frequency amplification transistor becomes unstable due to the coupling between the input tuning circuit and the interstage primary side tuning circuit.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and it is an object of the present invention to provide an electronic tuning tuner equipped with varicap diodes that can ensure sufficient isolation between each tuning circuit.

(Means for Solving the Problems) In order to achieve the above objects, the present invention uses a varicap diode which is a variable tuning element of an electronic tuning tuner having a high frequency amplifier circuit, a mixing circuit, 9 local oscillation circuits. VH that is combined and housed in one package, and the polarity of adjacent varicap diodes is alternately reversed.
It consists of an F circuit or a UHF circuit.

(Function) With the above-described configuration, the present invention was able to reduce coupling due to stray capacitance between each tuning circuit.

(Embodiment) FIG. 1 shows a method of arranging a varicap diode sealed in a package according to an embodiment of the present invention. 1-1 in Fig. 1 is a 4-piece enclosed type.

Similarly, 1-2 represents the three-packed type. (A) to (G) are varicap diodes. (a) represents the stray capacitance between each terminal.

FIG. 2 shows a conventional method. 2-1 in Figure 2,
In both cases 2-2, the polarities of the varicaps are arranged in the same direction.6 On the other hand, in the embodiment of FIG. 1, adjacent varicap diodes are arranged so that they always have opposite polarities.

With the above configuration, the 't% free capacitance between adjacent cathodes of each varicap diode becomes a negligible value. Therefore, it is possible to reduce coupling due to stray capacitance between hot points of each tuned circuit.

(Effects of the Invention) As described above, according to the present invention, the coupling between each tuning circuit becomes loose, preventing leakage of local components to the antenna terminal, and various interferences due to improvement of stable operation 9 selectivity characteristics of the amplifier circuit. The effect is that important and basic performance improvements regarding television tuners can be realized, such as improvements in performance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an arrangement of varicap diodes sealed in a package according to an embodiment of the present invention, FIG. 2 is a diagram showing varicap diodes sealed by a conventional packaging method, and FIG. Basic block diagram of a television tuner. 4 and 5 show circuit diagrams of the television tuner. Figure 1

Claims (1)

[Claims] Variable capacitance diodes (hereinafter referred to as varicap diodes), which are variable tuning elements of an electronic tuning tuner having a high frequency amplification circuit, a mixing circuit, and a local oscillation circuit, are combined and housed in one package, and adjacent varicap diodes are An electronically tuned tuner consisting of a VHF circuit or a UHF circuit whose polarity is alternately reversed.