JPS623924Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an oscillation circuit particularly suitable for integration into an integrated circuit, and is a circuit in which the oscillation frequency for multiple channels is switched using an electronic switch controlled by direct current.

When the output of video equipment such as a video tape recorder is monitored by a television receiver, it is usually modulated by a high frequency modulator and sent out.
This high-frequency modulator is a device that converts the output signal in a video tape recorder into a high-frequency wave similar to that of broadcast waves, and is usually configured to be able to switch between two channels, so that viewers can watch the actual broadcast. The output from the video tape recorder can be switched and input to a channel where there is no broadcast wave from the station.

As shown in FIG. 1, the high frequency modulator clamps the video signal of the video tape recorder in a video signal clamp circuit 11, and then uses the modulator 12 to clamp the video signal from the video tape recorder.
It is modulated and output to the output terminal 13 as a video high frequency signal. Further, the audio signal of the video tape recorder is frequency modulated in the frequency speed modulator 14,
The converter 15 converts the signal into a high frequency signal and outputs it to an output terminal 16 as an audio high frequency signal. The high frequency signal is input to the antenna terminal of the television receiver, and is tuned and received in the same way as broadcast waves. For this reason, high stability is required for the carrier wave, that is, the oscillation frequency. This carrier wave differs depending on the region, but in Japan, the first channel is used by switching to one of the second channels. Therefore, the carrier oscillator 17 uses the changeover switch 18 to switch the resonator 1 for one channel.
It is used by being connected to either the 9- or 2-channel resonator 20.

Conventionally, there is a circuit as shown in FIG. 2 as an oscillation circuit capable of switching carrier waves.

21 and 22 are surface acoustic wave resonators that can directly oscillate high frequencies of about 100 MHz.
Together with transistor _Q1 , it forms a grounded-emitter modified Colpitts oscillator circuit. To switch channels, a mechanical switch 23 is used to select either terminal ch ₁ or ch ₂ . For example, when terminal ch ₁ is selected, the output terminal 24 receives a carrier wave output at a frequency for the first channel, and when terminal ch ₂ is selected, a carrier wave output at a frequency for the second channel is obtained. is obtained. Although the switch 23 is configured as described above using a conventional oscillation circuit, a high-frequency current flows through the switch 23 itself, so when the switch 23 is physically configured, it must be placed as close as possible to the circuit part. . For this reason, it is impossible to remotely control channel switching by providing only the switch 23 at a different position.

This idea was made in view of the above circumstances, and in an oscillation circuit that uses multiple oscillators such as surface wave resonators and oscillates by switching them and setting channels, the channel switching is performed using direct current. An object of the present invention is to provide an oscillation circuit suitable for integration by enabling remote control of channel switching by using an electronic switch circuit that can be controlled manually.

Examples of this invention will be described below with reference to the drawings.

In FIG. 3, 31 is a surface acoustic wave resonator for the first channel, and 32 is a surface acoustic wave resonator for the second channel. One terminal of each surface acoustic wave resonator is connected in common with the collectors of transistors Q ₁₁ and Q ₁₂ , connected to an oscillation output terminal 33 , and further connected to a power supply terminal 35 via a resistor 34 . Also,
The other terminals of the surface wave resonators 31 and 32 are connected to the bases of transistors Q ₁₁ and Q ₁₂ , respectively. The emitters of the transistors Q ₁₁ and Q ₁₂ are commonly connected and connected to a reference potential terminal via a parallel circuit including a resistor 36 and a capacitor 37. transistor
Q ₁₁ and Q ₁₂ also function as differential switches,
The base of transistor Q ₁₂ is connected to the emitter of transistor Q 13 through resistor 38, and also to the emitter of transistor Q ₁₃ through resistor 38.
The base of _Q11 is connected to the transistor via resistor 39.
Connected to emitter of _Q14 .

A bias circuit consisting of a resistor 41, diodes D ₁ , D ₂ , and a resistor 42 is connected to the base of the transistor Q ₁₃ , and a bias circuit consisting of a resistor 43 , diodes D ₃ , D ₄ , and a resistor 44 is connected to the base of the transistor Q ₁₄ . It is connected. Also transistor
The collectors of Q ₁₃ and Q ₁₄ are connected to a power supply terminal, and the emitters are connected to a reference potential terminal via resistors 45 and 46, respectively. Furthermore, the transistor
These transistors are at the base of Q ₁₃ and Q ₁₄ .
In order to differentially control on/off of Q ₁₃ and Q ₁₄ , the collectors of transistors Q ₁₅ and Q ₁₆ are connected, respectively. The emitter of the transistor Q ₁₅ is connected to the reference potential terminal, and the base is connected to the reference potential terminal via a resistor 47 and to the output terminal ₅₀₁ of the changeover switch 50 via a resistor 48 . On the other hand, the emitter of the transistor _Q16 is connected to the reference potential terminal, and the base is connected to the power supply terminal 35 via the resistor 51 and to the collector of the transistor _Q17 . and this transistor
The emitter of _Q17 is connected to the reference potential terminal, the base is connected to the reference potential terminal via a resistor 52, and the selector switch 50 is connected via a resistor 53.
is connected to the output terminal 501 _of . Changeover switch 5
One input terminal ch ₁ of 0 is connected to the power supply terminal 35, and the other input terminal ch ₂ is connected to the reference potential terminal.

One embodiment of this invention is constructed as described above, and the circuit portions except the changeover switch 50 are integrated circuits. The current loop of the transistor Q ₁₁ and the surface wave resonator 31 constitutes a first emitter-grounded modified Colpittz oscillation circuit, and the current loop of the transistor Q ₁₂ and the surface wave resonator 32 constitutes a second
A modified Colpitts oscillator circuit with a grounded emitter is constructed.

Now, assuming that the changeover switch 50 is switched to the input terminal ch ₂ side, the transistors Q ₁₅ ,
Q ₁₇ is turned off and transistor Q ₁₆ is turned on. Therefore, transistor Q ₁₄ is turned off and transistor Q ₁₃ is turned on. By the way, transistor
A DC bias is applied to the base of _Q12 , turning on transistor _Q12 and turning off transistor _Q11 . Therefore, the surface wave resonator 32 and the transistor
The current loop of _Q12 forms an oscillation circuit, and a carrier wave output for the second channel is obtained at the output terminal 33. At this time, the base of the capacitor _Q11 is approximately at the reference potential, and the base and emitter are in a disconnected state. Therefore, the surface wave resonator 31 does not participate in the oscillation operation at this time.

On the other hand, when the changeover switch 50 is switched to the input terminal ch ₁ side, transistors Q ₁₅ and Q ₁₇ are turned on, transistor Q ₁₆ is turned off, and transistor Q ₁₄ is turned on.
is on and transistor _Q13 is off. Therefore, the transistor Q ₁₁ is turned on with a DC bias applied to its base, and the transistor Q ₁₂ is turned off with its base set to approximately the reference potential. As a result, the current loop of the transistor Q ₁₁ and the surface wave resonator 31 constitutes an oscillation circuit, and a carrier wave output for the first channel is obtained at the output terminal 33.
In this circuit, the oscillation output can be obtained across the resistor 34.

FIG. 4 shows an embodiment in which the number of switching channels is further increased, and the same parts as those in FIG. 3 are given the same reference numerals and the explanation thereof will be omitted. That is, this embodiment is an example in which the number of oscillation circuit loops for the third channel formed by the surface acoustic wave resonator 61 and the transistor _Q18 is further increased. In order to operate this oscillation circuit loop, the changeover switch 50 is
Switched to ch ₃ side. This turns off transistor _Q20 and turns on transistor _Q19 . Since the control terminal derived from this transistor _Q19 is connected to the base of the transistor _Q18 via the resistor 62, this transistor
Q ₁₈ turns on. Note that 66 to 70 are resistances,
D ₅ and D ₆ are diodes. In addition to this embodiment, the control circuit, ie, the control circuit using a transistor configuration for selecting an oscillation circuit loop, can be implemented in various other ways.

According to the above-described oscillation circuit of this invention, in order to switch and select a plurality of oscillation circuit loops, the transistors Q ₁₁ , Q ₁₂ , Q ₁₈ , etc. forming the oscillation loops themselves are operated by switching, and in this case, the mechanical This is done by switching the DC bias line from the control circuit, rather than by switching the DC bias line from the control circuit. Therefore, the changeover switch 50 that is operated may be located far away from the oscillation section, or may be replaced by electronic or remote control means. Further, a switch section for frequency switching in the oscillation circuit loop utilizes a transistor within the loop. As a result, the above oscillation circuit is suitable for circuit integration, and since the oscillation signal of the operated changeover switch oscillation section is not directly involved, it can be placed far away, making it suitable for remote control. becomes. Moreover, by configuring in this way, it becomes easy to increase the number of channels.

As explained above, this invention can provide an oscillation circuit that is suitable for integration and can be operated remotely.

[Brief explanation of the drawing]

Fig. 1 is a configuration explanatory diagram showing a high frequency modulator of a video tape recorder, Fig. 2 is a circuit diagram showing a conventional oscillation circuit, and Figs. 3 and 4 are circuit diagrams showing embodiments of this invention. . 31, 32, 61...Surface wave resonator, Q ₁₁ ~
Q ₂₀ ...transistor, 50...changeover switch.

Claims (1)

[Scope of utility model registration request] One terminal of the plurality of surface wave resonators is commonly connected to a power supply terminal via a resistor, and is also connected to an output terminal, and the one terminal is connected to the collector of each transistor corresponding to the surface wave resonator. are commonly connected, each other terminal of each surface wave resonator is connected to the base of each corresponding transistor, and the emitter of each transistor is commonly connected to a reference potential terminal via a parallel circuit of a capacitor and a resistor. a plurality of oscillation circuit loops, and a control circuit including a transistor, in which a DC bias output terminal is connected to each base of each of the transistors, and turns on any one transistor and turns off the other transistors. oscillation circuit.