JP3106513B2 - Electronic tuning tuner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a television receiver,
The present invention relates to an electronic tunable tuner used for video equipment typified by a video tape recorder and the like, and an electronic tunable tuner used for an audio receiver such as a car audio, a mini component, and a CD radio cassette player.

[0002]

2. Description of the Related Art In recent years, audio receivers such as car audio and mini-components have been increasingly multifunctional and diversified, and miniaturization has been promoted as represented by mini-mini components. On the other hand, in FM broadcasting and the like, the number of broadcasting stations is increasing due to the opening rush and the like.

[0003] From such a background, as the number of broadcasting stations increases, the number of interfering signals affecting the receiver increases, and a small-sized electronically tunable tuner having high interference rejection capability has been desired.

A conventional electronic tuning tuner will be described below with reference to FIGS. FIG. 2 shows a block diagram of a general electronic tuning tuner.
In the figure, reference numeral 1 denotes an input terminal, 2 denotes an input single tuning circuit, 3 denotes a high-frequency amplifier circuit, 4 denotes an interstage single tuning circuit, 5 denotes a mixing circuit, 6 denotes a local oscillation circuit, 7 denotes an intermediate frequency single tuning circuit, and 8 denotes Each output terminal is shown.

FIG. 5 is a circuit diagram showing the configuration of a conventional typical single tuning circuit. In the drawing, reference numeral 9 denotes a capacitor forming a trap, and 10 denotes the same coil. 11 is a coupling capacitor with the previous stage, 12 is a tuning coil, 13 is a tuning variable capacitance diode, 14 is a DC cut capacitor, and 15 is a DC cut capacitor.
Denotes a resistor for supplying a tuning voltage, 16 denotes a tuning capacitor, and 17 denotes a coupling capacitor with a subsequent stage.

In the electronic tunable tuner thus configured, first, a signal input from the input terminal 1 shown in FIG. 2 passes through a trap formed by a capacitor 9 and a coil 10 and then returns to the state shown in FIG. The coupling capacitor 11 of the single tuning circuit shown in FIG. 5 arranged in the input single tuning circuit 2 shown in FIG.
The tuning circuit 12 is tuned to the desired reception frequency by the voltage supplied from the resistor 15 by the tank circuit formed by the tuning coil 12, the tuning variable capacitance diode 13 and the tuning capacitor 16, and the coupling capacitor 17 The signal is amplified by the high frequency amplifier circuit 3 shown in FIG. The selectivity characteristic at that time is as shown by a broken line 27 in FIG. Further, the amplified signals are represented by the above reference numerals 11 to 17
Are tuned to the desired reception frequency in accordance with the selectivity characteristics obtained by the interstage single tuning circuit 4 shown in FIG. You. Further, the local oscillation frequency generated by the local oscillation circuit 6 is also input to the mixing circuit 5, and is output from the mixing circuit 5 as an intermediate frequency equal to the difference.
An output waveform corresponding to the selectivity characteristic obtained by the intermediate frequency single tuning circuit 7 formed by a coil and a capacitor is output from the output terminal 8.

[0007]

However, in the above-mentioned conventional configuration, since the respective tuning circuits between the input and the stage are of a single tuning configuration, not only the desired frequency but also the interfering frequency is passed, and When the frequency is a strong input, there is a problem that interference is generated.

Further, in order to remove the interference signal, a trap fixed only at a certain frequency is formed by the capacitor 9 and the coil 10, which is not suitable for miniaturization.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide an electronic tunable tuner which eliminates interference caused by these interference frequencies and is downsized.

[0010]

In order to achieve this object, an electronic tunable tuner according to the present invention comprises:
First, second and third capacitors connected in series in order ;
First and second variable capacitance diodes are opposed to the coil and a cathode side connected in parallel to said second capacitor
And the anode side of the first and second variable capacitance diodes
Fourth, a fifth capacitor, said first supply resistor which tuning voltage is connected to the cathode side of the second variable capacitance diode is supplied respectively connected between the ground
A coil, and the first and second variable capacitances
Formed by a diode and the fourth and fifth capacitors.
The attenuation frequency of the Π-type filter is determined by the first capacitor.
C, the second capacitor, the coil, and the second capacitor.
Tuning circuit formed by first and second variable capacitance diodes
Is set at a frequency approximately 21.4 MHz higher than the frequency of
It is a thing.

[0011]

According to this structure, the frequency input from the input terminal is applied to the cathode connected to the coil connected in parallel with the second capacitor through the first capacitor connected in series to the input terminal. By applying a tuning voltage corresponding to the desired frequency to the supply resistor connected to the cathode side of the first and second variable capacitance diodes, the desired resistance is tuned to obtain a certain selectivity characteristic. In addition, a π-type filter is formed by the combined capacitance of the coil and the fourth capacitor, and the capacitance of the fifth capacitor and the first and second variable capacitance diodes. The frequency band is attenuated, so that a high-frequency amplifier circuit or a tuning circuit effective against interference caused by the mixing circuit can be provided.

Further, in this configuration, the capacitance of the element component that determines the characteristics of the π-type filter is a combined capacitance of the first and second variable capacitance diodes for tuning and the fourth and fifth capacitors. Each variable capacitance diode is configured such that the capacitance is varied by applying a tuning voltage according to the reception frequency and can be tuned to the reception frequency. The cutoff frequency of the type filter can be changed at the same time.
In other words, since a wideband trap that follows the ratio of the combined capacitance is formed in accordance with the reception frequency, unnecessary interference frequencies can be attenuated regardless of which reception frequency is selected.
A stable reception state is always obtained. Further, since the trap is a broadband trap, it is not necessary to form a trap fixed only at a specific frequency, which is advantageous for miniaturization.

[0013]

(Embodiment 1) An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram showing a configuration of an input single tuning circuit of an electronic tuning tuner according to a first embodiment of the present invention. In FIG. 1, reference numeral 18 denotes a first capacitor, 19 denotes a second capacitor, and 20 denotes The third capacitor, 21 is the fourth capacitor, 22 is the fifth capacitor
, A first variable capacitance diode, 24
Denotes a second variable capacitance diode, 25 denotes a coil, and 26 denotes a tuning voltage supply resistance.

In the electronic tunable tuner according to the present invention thus constructed, first, the frequency input from the input terminal 1 shown in FIG. 2 is input to the first capacitor 18 shown in FIG. The frequency is the second capacitor 19
By applying a tuning voltage corresponding to a desired frequency to a coil 25 connected in parallel with the coil and a supply resistor 26 connected to the cathode side of the first and second variable capacitance diodes 23 and 24 whose cathode sides are opposed to each other. Tuning to the desired frequency, the coil 25, the fourth capacitor 21, the fifth capacitor 22, and the first and second variable capacitance diodes 2
By forming a π-type filter by the combined capacitance with the capacitance values of 3, 24, a pass characteristic as shown by the solid line 28 in FIG. 3 is obtained, unnecessary interference frequencies are attenuated, and the high-frequency amplification shown in FIG. A tuning circuit capable of performing an effective operation against interference caused by the circuit 3 and the mixing circuit 5 is provided.

For example, in the case of an upper heterodyne system in a voice tuner in the FM band, image interference, which is interference twice as high as the intermediate frequency, often causes a problem. This can be dealt with by determining the capacitance of each capacitor so that it can be set to a frequency 21.4 MHz higher than the frequency and forming a wideband variable image trap.

FIG. 3 shows comparison data of the selectivity characteristics when the constant is set so as to follow the image frequency in the above-mentioned upper heterodyne type FM tuner and the selectivity characteristics in the conventional circuit. FIG. 4 shows the data of the image disturbance ratio at that time. The dotted line shows the image disturbance characteristics by the conventional single tuning circuit, and the solid line shows the image disturbance characteristics by the present invention. It can be seen that the single tuned circuit of the present invention has much better performance in eliminating interference than the circuit.

(Embodiment 2) As an electronic tuning type tuner according to a second embodiment of the present invention, there is a case where the single tuning circuit of FIG. 1 described in the first embodiment is arranged in an interstage circuit. As a side effect when placed in the input circuit, FIG.
As a solution in the case where the deterioration of the transmission characteristic becomes a problem due to the matching with the load impedance of the rod antenna or the external antenna connected to the input terminal 1 shown in FIG.
A single tuning circuit is arranged in an interstage circuit. This embodiment is not suitable for the interference caused by the high frequency amplifier circuit 3 shown in FIG. 2, but the same effect as that of the first embodiment can be obtained for the interference caused by the mixing circuit 5. Therefore, it is the most practical circuit method as a method for eliminating the side effects.

[0018]

As described above, in the electronic tunable tuner according to the present invention, the first, second, and third capacitors are connected in series from the input side, and the coil and the cathode side are opposed to the second capacitor. The first and second variable capacitance diodes are connected in parallel, and the anode sides of the first and second variable capacitance diodes are grounded via fourth and fifth capacitors, respectively. By providing a single tuning circuit having a configuration in which a supply resistor for supplying a tuning voltage is connected to the cathode side of the variable capacitance diode, it is possible to improve the ability to eliminate interference caused by an unnecessary interference frequency.

Further, in this configuration, the capacitance of the element component that determines the characteristics of the π-type filter is the combined capacitance of the first and second variable capacitance diodes for tuning and the fourth and fifth capacitors. Each variable capacitance diode has a variable capacitance and can be tuned to the reception frequency by applying a tuning voltage corresponding to the reception frequency. The cutoff frequency can also be changed at the same time. In other words, it is possible to trap in accordance with the ratio of the combined capacitance according to the reception frequency, so that even if tuned to any reception frequency, unnecessary interference frequencies can be attenuated, and a fixed trap that attenuates only a certain frequency Can be eliminated, and a small and high-performance electronic tuner can be realized, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an input single tuning circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of the electronic tunable tuner of the present invention and a conventional example.

FIG. 3 is a graph showing selectivity characteristics;

FIG. 4 is an image interference characteristic diagram.

FIG. 5 is a circuit diagram showing a configuration of a conventional typical single tuning circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input terminal 2 Input single tuning circuit 3 High frequency amplifier circuit 4 Interstage single tuning circuit 5 Mixing circuit 6 Local oscillation circuit 7 Intermediate frequency single tuning circuit 8 Output terminal 18 First capacitor 19 Second capacitor 20 Third capacitor 21 Fourth capacitor 22 Fifth capacitor 23 First variable capacitance diode 24 Second variable capacitance diode 25 Coil 26 Tuning voltage supply resistance

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Sho-59-20744 (JP, U) Japanese Utility Model Sho 55-173631 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H03J 3/20 H04B 1/18

Claims (2)

(57) [Claims] An input terminal and an input terminal connected to the input terminal.
And power single-tuned circuit, a high frequency amplifier circuit connected to the input single tuning circuit, a mixing circuit and a local oscillator circuit connected through the interstage circuit of the double tuned or single-tuned to the high frequency amplifier circuit, the mixing Intermediate frequency connected to the output of the circuit
Connect to single tuned circuit and the output of this intermediate frequency single tuned circuit
Is provided with an output terminal, the input single tuning circuit, wherein
First, second from the input terminal side are connected in series in this order, is connected to the third capacitor, in parallel with the second capacitor
First and second variable capacitance diodes with their coils and cathodes facing each other, and fourth and fifth capacitors respectively connected between the anode side of these first and second variable capacitance diodes and ground. And the tuning voltage is connected to the cathode side of the first and second variable capacitance diodes.
A supply resistance to be supplied, the coil,
The first and second variable capacitance diodes and the fourth and fifth cores;
The attenuation frequency of the Π-type filter formed with the capacitor
The first capacitor, the second capacitor,
The coil and the first and second variable capacitance diodes.
About 21.4 MHz higher than the frequency of the tuning circuit to be formed
Electronically tuned tuner set to frequency . 2. An input terminal and an input terminal connected to the input terminal.
And power single-tuned circuit, a high frequency amplifier circuit connected to the input single tuning circuit, a mixing circuit and a local oscillator circuit connected via a single-tuned circuit between stages to the high frequency amplifier circuit, the mixing
An intermediate frequency single tuned circuit connected to the output of the
And an output terminal connected to the output of the intermediate frequency single tuned circuit , wherein the interstage single tuned circuit is arranged in order from the input terminal side.
First, a second, a third capacitor connected in series, before
First and second variable capacitance diodes are opposed to the coil connected and a cathode-side in parallel to the serial second capacitor
And the anode side of the first and second variable capacitance diodes
Fourth, a fifth capacitor, said first supply resistor which tuning voltage is connected to the cathode side of the second variable capacitance diode is supplied respectively connected between the ground
A coil, and the first and second variable capacitances
Formed by a diode and the fourth and fifth capacitors.
The attenuation frequency of the Π-type filter is determined by the first capacitor.
C, the second capacitor, the coil, and the second capacitor.
Tuning circuit formed by first and second variable capacitance diodes
An electronically tunable tuner set at a frequency approximately 21.4 MHz higher than the frequency of the electronic tuner.