JPH0583035A - Carrier wave generation circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] The oscillator itself can be built into the integrated circuit, and a high-quality modulated output can be obtained. [Structure] An oscillating means 11 by a multivibrator is built in an integrated circuit, and an oscillation output obtained from this oscillating means 11 is waveform-shaped by a time constant circuit 12, and the output of this time constant circuit 12 is made closer to a sine wave. Therefore, the waveform is shaped by the non-linear circuit 13 and used as a carrier for modulation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for converting an audio signal into a modulated wave in order to supply an output of a video tape recorder (hereinafter referred to as VTR) to a specific channel of a television receiver. Carrier generation circuit.

[0002]

2. Description of the Related Art When inputting the output of a VTR to a specific channel of a television receiver, a modulator for converting an audio signal into a modulated wave is used, which is then mixed with a video signal and then converted into a high frequency band. ing. Several M for voice modulator
Although a carrier in the Hz band is used, in the conventional modulator,
The carrier oscillator is provided outside the integrated circuit, and the modulator is provided inside the integrated circuit. For this reason, there are problems that the number of external parts is increased in the periphery of the integrated circuit and that assembly and adjustment are troublesome. Therefore, considering that the carrier oscillator is built in the integrated circuit, it cannot be simply incorporated. When an oscillator is provided inside the integrated circuit, a circuit that generates a rectangular wave is conceivable because a large coil or capacitor cannot be incorporated.
If this is modulated with a signal, a high frequency is naturally generated, and a low pass filter for extracting the modulated wave component is required.
Moreover, the characteristics of this low-pass filter must be such that the band can be rapidly cut, which is technically difficult at the analog level.

[0003]

Conventionally, it has been difficult to incorporate the carrier generating portion of a modulator into an integrated circuit.
Further, there is a problem that a good modulation output cannot be expected even if it is simply incorporated. Therefore, an object of the present invention is to provide a carrier wave generation circuit which can be incorporated in an integrated circuit and can obtain a high-quality modulated output.

[0004]

SUMMARY OF THE INVENTION The present invention provides an oscillating means by a multivibrator built in an integrated circuit, a time constant circuit for shaping the oscillation output obtained from the oscillating means, and a time constant circuit for the time constant circuit. And a non-linear circuit for shaping the waveform so as to bring the output closer to a sine wave.

[0005]

According to the above construction, since the carrier waveform becomes a sine wave due to the time constant circuit and the non-linear circuit, the generation of high frequency components is eliminated, and the low pass filter for extracting the modulated wave is also possible at the analog level. Become.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1A shows an embodiment of the present invention,
FIG. 6B shows the output signal waveform in each block of this embodiment. Reference numeral 11 denotes a monostable multivibrator integrated inside the integrated circuit, which generates a rectangular wave a. This rectangular wave a is input to the time constant circuit 12 in the next stage and undergoes waveform shaping. As a result, the output of the time constant circuit 12 becomes a signal b shown in FIG. This signal is input to the non-linear circuit 13 and is approximated to a sine wave. Therefore, the waveform of the output signal of the non-linear circuit 13 becomes the signal c shown in FIG. This signal c is input to the mixing circuit 14 as a modulation carrier. Mixing circuit 1
In 4, the carrier c is modulated by, for example, an audio signal input from the terminal 15, and an audio modulation signal is output to the output terminal 16.

As described above, the time constant and nonlinear circuit 12,
By making the carrier a sine wave by means of 13, the oscillation means by the monostable multivibrator 11 can be incorporated inside the integrated circuit, the generation of high frequency components can be eliminated, and the abrupt cut characteristic low range for extracting the modulated wave can be obtained. No pass filter is required, or the cutoff characteristic does not need to be so strict.

FIG. 1C shows another embodiment of the present invention, in which the output of the oscillator by the monostable multivibrator 11 is sequentially passed through the first and second waveform shaping circuits 22 and 23 to form a sine wave. , May be input to the mixing circuit 14. As the waveform shaping circuit, a transistor circuit that makes the waveform dull is used.

FIG. 2 is a concrete circuit example of the time constant circuit 12 of FIG. 1A or the waveform shaping circuit of FIG. 1C.
The rectangular wave a from the monostable multivibrator 11 is supplied to the terminal 101. Terminal 101 is transistor Q1
Connected to the base of. The transistors Q1 and Q2 form a differential pair, the common emitter is connected to the constant current source 102, and the collectors of the transistors Q1 and Q2 are connected via the diodes D1 and D2 (transistor diode connection) to the power supply line 10.
3 and also to the bases of transistors Q3 and Q4, respectively. The emitters of the transistors Q3 and Q4 are connected to the power supply line 103. The collector of the transistor Q4 is grounded via the diode D3 and is also connected to the base of the transistor Q5. The emitter of the transistor Q5 is grounded, and the collector is connected to the collector of the transistor Q3. Common collector of transistors Q3 and Q5 and bias power supply B1
A time constant circuit composed of a resistor R and a capacitor C is connected between them, and the output b is derived from the collector of the transistor Q3. This circuit can output a rectangular wave input a as a triangular wave output b.

FIG. 2B shows the non-linear circuit 1 of FIG.
3 is a specific circuit example of No. 3. The terminal 110 has a time constant circuit 1
The triangular wave output b from 2 is supplied. The terminal 110 is connected to the base of the transistor Q10. The transistors Q10 and Q12 form a differential pair, each emitter is connected to the constant current source 111 via the resistors R1 and R2, and each collector is connected to the power supply line 103 via the resistors R3 and R4. Has been done. Transistor Q11
A predetermined voltage V2 is supplied to the base of the. Now, assuming that the voltage input to the input terminal 110 is V1, the resistance R3,
When the currents flowing through R4 are I1 and I2, respectively, the characteristics of this circuit can be expressed as shown in FIG. This circuit operates differentially, and transistors Q10 and Q
A differential output is obtained between 11 collectors, the characteristics of which are designed to be used including the non-linear region of the transistor. As a result, the output c has a sine curve in the vicinity of the positive and negative peaks, and as a result, the output c has a waveform that approaches a sine wave.

FIG. 3 shows a concrete example of the mixing circuit 14.
The VTR may require an AM signal or an FM signal as an output. This mixing circuit is designed so that when integrated, it can take out either output.

Now, a case where an AM signal is obtained in the form shown in FIG. 1 will be described. A waveform-shaped sine wave is supplied between the input terminals 201 and 202. Terminal 201,
202 is connected to the bases of the transistors Q21, 22. The emitters of the transistors Q21 and Q22 pass through resistors R11 and R12, respectively, and then the constant current source 203
, Each collector of which is a diode D11,
It is connected to the power supply line 103 via D12. The collector of the transistor 22 is composed of the transistors Q23 and Q.
24, and the collector of the transistor Q21 is connected to the common bases of the transistors Q23 and Q25. The emitters of the transistors Q23 and Q24 are commonly connected to the collector of the transistor Q27, and the emitters of the transistors Q25 and Q26 are commonly connected to the collector of the transistor Q28. The emitters of the transistors Q27 and Q28 are connected to the constant current source 204, and the terminals 205 and 206 are provided between the respective bases.
Is provided, and an audio signal is supplied between these terminals. The collectors of the transistors Q23 and Q25 have a common resistor R1.
4 is connected to the power supply line 103, and the collectors of the transistors Q24 and Q26 are commonly connected to the power supply line 103 via the resistor R15. An output terminal 207 is provided on the collectors of the transistors Q24 and Q26. Transistors Q23 to Q28 form a double-bunlas type balanced modulator. Therefore, terminal 2
A carrier is supplied between 01 and 202, and terminals 205 and 20
When an audio signal is supplied between 6 and 6, an AM signal can be obtained at the output terminal 207.

When the FM output is taken out through this circuit, it is used as follows. That is, the terminals 201 and 202
An FM signal is supplied between them, and a DC voltage having a predetermined potential is supplied to the terminals 205 and 206. Then, the output terminal 20
The input FM signal is directly output to 7. The input FM signal is supplied from, for example, an FM modulator using a PLL, and the mixing circuit at this time is
It is used as a signal output stage and functions as an output matching unit.

[0015]

As described above, according to the present invention,
The oscillator itself can be incorporated inside the integrated circuit, and a high-quality modulated output can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG.
Is a block diagram of one embodiment, FIG. 3B is a signal waveform diagram, and FIG. 3C is a block diagram showing another embodiment.

FIG. 2 is a diagram showing a specific circuit of each part of FIG. 1A, where FIG. 2A is a specific circuit diagram of a time constant circuit, and FIG. 2B is a specific circuit diagram of a non-linear circuit; FIG. 3C is a characteristic diagram of this nonlinear circuit.

FIG. 3 is a diagram showing a specific circuit of a mixing circuit shown in FIG.

[Explanation of symbols]

11 ... Monostable multivibrator, 12 ... Time constant circuit,
13 ... Non-linear circuit, 14 ... Mixed circuit.

Claims (1)

[Claims] 1. An oscillating means using a multivibrator built in an integrated circuit, a time constant circuit for shaping the oscillation output obtained from the oscillating means, and an output of the time constant circuit for making the output closer to a sine wave. A carrier wave generation circuit comprising: a non-linear circuit for waveform shaping.