JPH07298151A - Tuner - Google Patents

Abstract

(57) [Summary] [Object] To propose a tuner capable of eliminating interference such as image interference and intermodulation interference without narrowing the band of the reception range by simply adding a simple circuit to the conventional device. . A tuner provided with a frequency converter comprising a double balanced mixer 5 to which a received signal is supplied and a local oscillator signal to supply a local oscillation signal to the double balanced mixer 5,
The local oscillation signal is supplied to one pair of input terminals of the two pairs of input terminals of the double balanced mixer 5, and the other pair of input terminals 3
The receiving signal is supplied to one of the input terminals 31 of the input terminals 1 and 32, and the resonance circuit is connected between the other input terminal 32 and the reference potential point. The resonance frequency of the resonance circuit is set to be low.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tuner such as a television tuner.

[0002]

2. Description of the Related Art A conventional television tuner will be described with reference to FIG. The amplitude-modulated video signal (high-frequency video signal), which is the signal received from the antenna 1, is supplied to the high-frequency amplifier 3 through the input single tuning circuit 2 to be amplified, and then the inter-stage double tuning circuit 4 is provided. The frequency mixer 5 having a balanced mixer configuration is supplied. The input single tuning circuit 2 and the interstage double tuning circuit 4 work together to center the carrier frequency 6
It is configured to exhibit a bandpass characteristic such that the gain is substantially constant with respect to a received signal having a bandwidth of MHz or higher. The band pass center frequency is switched according to the switching of the oscillation frequency of the local oscillator 6 according to the channel switching.

A local oscillation signal from a local oscillator 6 whose oscillation frequency is switched according to channel switching is supplied to a frequency mixer 5, and an intermediate frequency amplitude-modulated video signal obtained from the frequency mixer 5 is an intermediate frequency. The intermediate frequency signal is obtained at the output terminal 8 by being supplied to and amplified by the amplifier 7.
The frequency mixer 5 and the local oscillator 6 constitute a frequency converter.

Next, with reference to FIG. 8, a specific circuit of the frequency mixer 5 having a double balanced mixer structure composed of an IC will be described. Q1 to Q6 are NPN type transistors. The transistors Q1 and Q2 form a first differential amplifier, the transistors Q3 and Q4 form a second differential amplifier, and the transistors Q5 and Q6 form a third differential amplifier. It constitutes a differential amplifier.

The operating voltage Vcc is applied to the collectors of the transistors Q1 and Q3 through the load resistor 33 and to the collectors of the transistors Q2 and Q4 through the load resistor 34. The output terminal 41 is derived from the collectors of the transistors Q1 and Q3, the output terminal 42 is derived from the collectors of the transistors Q2 and Q4, and the frequency mixed output from the output terminals 41 and 42 is supplied to the intermediate frequency amplifier 7. .

The input terminal 43 is derived from the bases of the transistors Q1 and Q4, and the transistors Q2 and Q3 are provided.
The input terminal 44 is derived from each of the bases, and the local oscillation signal from the local oscillator 6 is supplied to these input terminals 43 and 44.

The emitters of the transistors Q1 and Q2 are connected to the collector of the transistor Q5, and the collectors of the transistors Q3 and Q4 are connected to the collector of the transistor Q6. Input terminals 31, 32 are derived from the respective bases of the transistors Q5, Q6, and these input terminals 31,
An amplitude-modulated video signal (received signal) from the double tuning circuit 4 is supplied to 32.

A positive bias voltage from bias power supply 40 is applied to transistor Q through resistors 39 and 38, respectively.
5, Q6 applied to each base. Transistor Q5,
The emitters of Q6 are connected to each other through resistors 35 and 36, and the connection midpoint is grounded through a constant current circuit 37.

Next, with reference to FIG. 9, a specific circuit configuration of the interstage double tuning circuit 4 connected between the high frequency amplifier 3 and the frequency mixer 5 will be described. Reference numeral 11 is a MOS-FET that constitutes the high-frequency amplifier 3, and one of its gates has an AGC.
The AGC signal from the circuit is supplied, the amplitude-modulated video signal (received signal) from the input single tuning circuit 2 is supplied to the other gate, and the source is grounded through the parallel circuit of the resistor 12 and the capacitor 13. .

Reference numerals 16 and 17 denote primary and secondary coils constituting a transformer, one end of which is a MOS-F.
It is connected to the drain of ET11 and its drain is grounded through a series circuit of a capacitor 14 and a voltage variable capacitance diode 15. The anode of the diode 15 is grounded, and the control voltage VC is applied to the cathode of the diode 15 through the resistor 21. The other end of the primary coil 16 is grounded through a bypass capacitor 18, and the other end has a DC voltage + for operating the MOS-FET 11.
B is applied. The primary coil 16, the capacitor 14, and the voltage variable capacitance diode 15 form a primary side resonance circuit.

Although not shown, a local oscillation signal from a local oscillator 6 is supplied to one pair of input terminals of the two pairs of input terminals of the frequency mixer 5, and the other pair of input terminals 31,
One input terminal 31 of the secondary coil 17 is connected to one end of the secondary coil 17 through the coupling capacitor 23, and the other input terminal 32 is grounded through the coupling capacitor 24. One end of the secondary coil 17 is grounded through a series circuit of the voltage variable capacitance diode 19 and the capacitor 20, and the other end of the secondary coil 17 is grounded. The anode of the voltage variable capacitance diode 19 is connected to one end of the primary coil 17, and the control voltage VC is applied to the cathode thereof through the resistor 22. The secondary coil 17, the voltage variable capacitance diode 19, and the capacitor 20 form a secondary side resonance circuit.

[0012]

With the widespread use of cable television in recent years, a television receiver and a television tuner of a VTR are required to have a wider receiving range. Also, with the increase in the number of receiving channels, it has been required to improve the ability to eliminate interference. When the tuner reception range is widened, the selectivity characteristic is deteriorated and the interference rejection capability is lowered. Therefore, the reception range bandwidth and the interference rejection capability conflict with each other.

In a television tuner, interference often occurs in a frequency mixer, and the interference is image interference, intermodulation interference, or the like. In order to eliminate these interferences, the selectivity characteristics of the input single tuning circuit, the high frequency amplifier, the interstage double tuning circuit and the frequency mixer must be improved conventionally, but if so, the band of the reception range is increased. It was difficult to achieve because it would be narrowed.

In view of such a point, the present invention is a television capable of eliminating interference such as image interference and intermodulation interference without narrowing the band of the reception range by simply adding a simple circuit to the conventional device. The idea is to propose a tuner.

[0015]

A first aspect of the present invention is a frequency converter comprising a double balanced mixer 5 to which a received signal is supplied and a local oscillator 6 which supplies a local oscillation signal to the double balanced mixer 5. In a tuner equipped with a mixer, one of two pairs of input terminals 43, 44; 31, 32 of the double-balanced mixer 5
A local oscillation signal is supplied to the pair of input terminals 43 and 44, a reception signal is supplied to one input terminal 31 of the other pair of input terminals 31 and 32, and a reception signal is supplied between the other input terminal 32 and the reference potential point. A resonance circuit is connected to, so that the conversion gain for the interfering wave signal is lower than the conversion gain for the received signal,
A tuner characterized in that a resonance frequency of a resonance circuit is set.

The second aspect of the present invention is the same as the first aspect of the present invention.
The resonance circuit is a parallel resonance circuit, and its resonance frequency is set so as to trap an interfering wave signal.

A third aspect of the present invention is the same as the first aspect of the present invention.
The resonance circuit is a series resonance circuit, and the resonance frequency of the resonance circuit is set so as to pass the received signal.

In a fourth aspect of the present invention according to the first, second or third aspect of the present invention, the resonant circuit is provided with variable reactance means 27 or 30 for switching the resonant frequency of the resonant circuit in response to switching of the receiving frequency. It is a tuner characterized by that.

[0019]

According to the first aspect of the present invention, the conversion gain for the interfering wave signal becomes lower than the conversion gain for the received signal due to the resonance circuit connected between the input terminal 32 and the reference potential point.

[0020]

Embodiments of the present invention applied to a television tuner will be described in detail below with reference to the drawings. The overall configuration of the television tuner is the same as that of the conventional television tuner of FIG. 7, and the configuration of the double balanced mixer constituting the frequency mixer 5 is the same as that of the conventional double balanced mixer of FIG. Since the configurations are the same, their illustration and description are omitted.

Next, with reference to FIG. 1, a specific circuit of the interstage double-tuned circuit 4 connected between the high frequency amplifier 3 and the frequency mixer 5 as the embodiment (1) of the present invention will be described. To do. Two pairs of input terminals 43, 44; one pair of input terminals 4 of 31, 32 of the frequency mixer having a double balanced mixer configuration
Local oscillation from the local oscillator 6 is supplied to 3, 44, one input terminal 31 of the other pair of input terminals 31, 32 is connected to one end of the secondary coil 17 through the coupling capacitor 23, and the other The input terminal 32 is connected to one end of a parallel resonant circuit including an inductor (coil) 25 and a capacitor 26 through the coupling capacitor 24, and the other end is grounded.

In this case, the parallel resonance frequency f ₀ determined by the inductance L of the inductor 25 and the capacitance C ₁ of the capacitor 26 is set equal to the center frequency of the image interference wave signal to trap the image interference wave signal. You can The frequency characteristic of the conversion gain in this case exhibits a trap characteristic in which the frequency f ₀ is the trap frequency as shown in FIG. The capacitance C _{2 of the} capacitor 24 is set sufficiently larger than the capacitance C _{1 of the} capacitor 26.

Reference numeral 11 denotes a MOS- which constitutes the high frequency amplifier 3.
FET, AGC from AGC circuit to one of its gates
The signal is supplied and the other gate receives the input single tuning circuit 2
The amplitude-modulated video signal (received signal) from is supplied, and its source is grounded through the parallel circuit of the resistor 12 and the bypass capacitor 13.

Reference numerals 16 and 17 denote primary and secondary coils constituting a transformer, one end of which is a MOS-F.
It is connected to the drain of ET11 and its drain is grounded through a series circuit of a capacitor 14 and a voltage variable capacitance diode 15. The anode of the diode 15 is grounded, and the control voltage VC is applied to the cathode of the diode 15 through the resistor 21. The other end of the primary coil 16 is grounded through a bypass capacitor 18, and a DC voltage + B which is the operating voltage of the MOS-FET 11 is applied to the other end. The primary coil 16, the capacitor 14, and the voltage variable capacitance diode 15 form a primary side resonance circuit.

One end of the secondary coil 17 is a coupling capacitor 2
Connected to the input terminal 31 of the frequency mixer 5 through 3,
One end thereof is grounded through a series circuit of the voltage variable capacitance diode 19 and the capacitor 20, and the other end of the secondary coil 17 is grounded. The anode of the voltage variable capacitance diode 19 is connected to one end of the primary coil 17, and the control voltage VC is applied to the cathode thereof through the resistor 22. The secondary coil 17, the voltage variable capacitance diode 19, and the capacitor 20 form a secondary side resonance circuit.

Next, with reference to FIG. 3, a specific circuit of the interstage double-tuned circuit 4 connected between the high frequency amplifier 3 and the frequency mixer 5 as the embodiment (2) of the present invention will be described. However, the portions corresponding to those in FIG.

The input terminal 32 of the frequency mixer 5 of the double balanced mixer configuration is connected to one end of the parallel resonance circuit of the series circuit of the inductor (coil) 25 and the voltage variable capacitance diode 27 and the capacitor 28 through the coupling capacitor 24. And the other end is grounded. In this case, the anode of the voltage variable capacitance diode 27 is on the side of the midpoint of connection between the capacitor 24 and the inductor 25, and the resistor 29 is provided on the cathode thereof.
A control voltage VC is applied through the.

In this case, the resonance frequency f ₀ determined by the inductance L of the inductor 25 and the combined capacitance C ₁ of the voltage variable capacitance diode 27 and the capacitor 28 is set to be equal to the center frequency of the image interfering wave signal according to the channel switching. By tracking in conjunction with the tracking of the pass band of the double tuning circuit 4, the image interfering wave signal can be trapped. The frequency characteristic of the conversion gain in this case exhibits the trap characteristic shown in FIG. The capacitance C _{2 of the} capacitor 24 is the series capacitance C of the capacitor 28 and the voltage variable capacitance diode 27.
Set sufficiently larger than ₁ .

Next, with reference to FIG. 4, a specific circuit of the interstage double-tuned circuit 4 connected between the high frequency amplifier 3 and the frequency mixer 5 as the embodiment (3) of the present invention will be described. However, the portions corresponding to those in FIG.

The input terminal 32 of the frequency mixer 5 having a double balanced mixer configuration is grounded through a series resonance circuit composed of a capacitor 24 and an inductor (coil) 25.

In this case, the resonance frequency f ₁ determined by the inductance L of the inductor 25 and the capacitance C ₂ of the capacitor 24 is set to be equal to the center frequency of the reception signal, so that the reception signal is passed. 5
It is possible to realize the selectivity characteristic shown in (1) and improve the interference characteristics of the intermodulation interference wave signal, the image interference wave signal, and the like.

Next, with reference to FIG. 6, a concrete circuit of the interstage double tuning circuit 4 connected between the high frequency amplifier 3 and the frequency mixer 5 as the embodiment (3) of the present invention will be described. , Parts corresponding to those in FIG.

The input terminal 32 of the frequency mixer 5 having a double balanced mixer configuration is grounded through a series resonance circuit composed of a capacitor 24, a variable voltage capacitance diode 30 and an inductor (coil) 25. In this case, the anode of the voltage variable capacitance diode 30 is placed on the inductor 25 side, and the cathode of the voltage variable capacitance diode 30 is connected to the control voltage V through the resistor 20.
Apply C.

In this case, the inductance L of the inductor 25, the capacitor 24 and the voltage variable capacitance diode 3
The resonance frequency f ₁ determined by the combined capacitance C ₂ of 0 is linked to the tracking of the pass band of the double tuning circuit 4 according to the channel switching so that the resonance frequency f ₁ becomes equal to the center frequency of the received signal. It is possible to realize the selectivity characteristic shown in FIG. 5 so that the signal is allowed to pass, and it is possible to improve the interference characteristics of the intermodulation interference wave signal, the image interference wave signal, and the like.

According to the first tuner (television tuner) of the embodiment, the double balanced mixer 5 to which the received signal is supplied.
And a tuner provided with a frequency converter comprising a local oscillator 6 for supplying a local oscillation signal to the double-balanced mixer 5 thereof, two pairs of input terminals 43, 44 of the double-balanced mixer 5;
A local oscillation signal is supplied to one pair of input terminals 43 and 44 of the pair of input terminals 31 and 32, a reception signal is supplied to one input terminal 31 of the pair of input terminals 31 and 32 of the other pair, and the other input terminal 32 The resonance frequency of the resonance circuit is set so that the conversion gain for the interfering wave signal is lower than the conversion gain for the received signal by connecting the resonance circuit between the reference voltage point and the reference potential point. It is possible to obtain a television tuner capable of eliminating interference such as image interference and intermodulation interference without narrowing the band of the reception range simply by adding.

According to the second tuner (television tuner) of the embodiment, in the first tuner, the resonance circuit is a parallel resonance circuit, and its resonance frequency is set so as to trap the interference wave signal. Therefore, by adding a simple circuit to the conventional device, the image interference wave signal can be eliminated without narrowing the band of the reception range.

According to the third tuner (television tuner) of the embodiment, in the first tuner, the resonance circuit is a series resonance circuit, and its resonance frequency is set so as to pass the received signal. Since the frequency mixer 5 having the double-balanced mixer 5 can be provided with selectivity characteristics, it is possible to add a simple circuit to the conventional device and to mix the band without narrowing the reception range band. Modulated jammer signal,
It is possible to improve the interference characteristics of the image interference wave signal and the like.

According to the fourth tuner (television tuner) of the embodiment, in the first, second or third tuner, the variable reactance means (voltage variable capacitance diode 27 for switching the resonance frequency of the resonance circuit between the reception frequencies). Or 30) is provided in the resonance circuit, the first, second or third
In addition to the effect of the tuner, it is possible to ensure the elimination of the interfering wave signal according to the switching of the reception frequency.

The present invention can be applied not only to the TV tuner but also to a radio tuner.

[0040]

According to the first aspect of the present invention, a tuner provided with a frequency converter comprising a double balanced mixer to which a received signal is supplied and a local oscillator for supplying a local oscillation signal to the double balanced mixer. , The local oscillation signal is supplied to one pair of input terminals of the two pairs of input terminals of the double balanced mixer, the reception signal is supplied to one input terminal of the other pair of input terminals, and the other A resonance circuit is connected between the input terminal and the reference potential point, and the resonance frequency of the resonance circuit is set so that the conversion gain for the interfering wave signal is lower than the conversion gain for the received signal. Image interference without narrowing the band of the receiving range by simply adding a simple circuit.
It is possible to obtain a television tuner capable of eliminating interference such as intermodulation interference.

According to the second aspect of the present invention, in the first aspect of the present invention, the resonance circuit is a parallel resonance circuit, and its resonance frequency is set so as to trap the interfering wave signal. By adding a simple circuit, the image interference wave signal can be eliminated without narrowing the band of the reception range.

According to the third aspect of the present invention, in the first aspect of the present invention, the resonance circuit is a series resonance circuit, and its resonance frequency is set so as to pass the received signal.
Selectivity characteristics can be given to the frequency mixer with double balanced mixer configuration, so by adding a simple circuit to the conventional device, the intermodulation interference wave can be obtained without narrowing the band of the reception range. It is possible to improve the interference characteristics of a signal, an image interference wave signal and the like.

According to the fourth aspect of the present invention, in the first, second or third aspect of the present invention, the variable reactance means for switching the reception frequency of the resonance frequency of the resonance circuit is provided in the resonance circuit. In addition to the effect of the second or third aspect of the present invention, it is possible to ensure the elimination of the interfering wave signal according to the switching of the reception frequency.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment (1) of the present invention.

FIG. 2 is a characteristic curve diagram showing frequency characteristics of conversion gain.

FIG. 3 is a circuit diagram showing an embodiment (2) of the present invention.

FIG. 4 is a circuit diagram showing an embodiment (3) of the present invention.

FIG. 5 is a characteristic curve diagram showing frequency characteristics of conversion gain.

FIG. 6 is a circuit diagram showing an embodiment (4) of the present invention.

FIG. 7 is a block diagram showing a conventional TV tuner.

FIG. 8 is a circuit diagram showing a frequency mixer having a double balanced mixer configuration.

FIG. 9 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 1 antenna 2 input single tuning circuit 3 high frequency amplifier 4 interstage double tuning circuit 5 frequency mixer with double balanced mixer configuration 6 local oscillator 7 intermediate frequency amplifier 8 output terminal 24 capacitor 25 inductor 26 capacitor 27 voltage variable capacitance diode 28 capacitor 30 voltage variable capacitance diode

Claims (4)

[Claims] 1. A tuner provided with a frequency converter comprising a double balanced mixer to which a received signal is supplied and a local oscillator for supplying a local oscillation signal to the double balanced mixer, wherein: The local oscillation signal is supplied to one pair of input terminals of the two pairs of input terminals, the reception signal is supplied to one input terminal of the other pair of input terminals, and the other input terminal and a reference potential point A tuner characterized in that a resonance circuit is connected between and, and a resonance frequency of the resonance circuit is set so that a conversion gain for an interfering wave signal is lower than a conversion gain for the reception signal. 2. The tuner according to claim 1, wherein the resonance circuit is a parallel resonance circuit, the resonance frequency of which is set so as to trap the interfering wave signal. 3. The tuner according to claim 1, wherein the resonance circuit is a series resonance circuit, and its resonance frequency is set so as to allow the reception signal to pass therethrough. 4. The tuner according to claim 1, 2 or 3, wherein the resonant circuit is provided with variable reactance means for switching the resonant frequency of the resonant circuit according to switching of the reception frequency. Tuner.