JP3169145B2 - Oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator using a resonator such as a quartz oscillator, and more particularly to an oscillator that can stabilize an oscillation frequency when the oscillation frequency is fixed.

[0002]

2. Description of the Related Art Generally, a video tape recorder (hereinafter, referred to as a video tape recorder)
An oscillator using a crystal resonator as a resonator used in a VTR is used as a variable oscillator to lock to a color subcarrier during recording, and is used as a fixed oscillator as a reference during reproduction.

FIG. 4 shows a block diagram of such a conventional oscillator.

[0004] In FIG. 4, an oscillator 50 is connected to a common terminal c of a changeover switch 51 by a resonator 5 using a quartz oscillator.
2, as well as connected to a first input terminal a1 of the switch 51 via the limiter amplifier 53 and resistors R11, the switching switch 51 the connection point of the limiter amplifier 53 resistors R11 through a phase shifter 54 and the resistor R12 2 is connected to the input terminal a2.

[0005] The changeover switch 51 is used for reproducing a VTR.
That second in the case of the oscillation frequency fixed mode first input terminal a1
It was connected to the common terminal c, the recording of the VTR, that is, connects the second input terminal a2 to the common terminal c when the oscillation frequency variable mode. Thus, when the oscillator 50 is in the oscillation frequency fixed mode, the oscillator 50 and the limiter amplifier 5
3 and the resistor R11 are connected in a loop, and in the case of the oscillation frequency variable mode, the resonator 52, the limiter amplifier 53, the phase shifter 54, and the resistor R12 are connected in a loop.

The phase shifter 54 has a phase shift amount controlled by a control voltage V11 supplied to an input terminal 55.

In such an oscillator 50, in the case of the fixed oscillation frequency mode, the signal passing through the resonator 52 is
The signal is fed back to the resonator 52 via the limiter amplifier 53 and the resistor R11. Thus, the oscillator 50 oscillates at the frequency fa at which no phase delay occurs in the resonance characteristics of the resonator 52 and the resistor R11.

In the case of the oscillation frequency variable mode, the signal passing through the resonator 52 returns to the resonator 52 via the limiter amplifier 53, the phase shifter 54 and the resistor R11. Thus, when the phase shift amount is controlled to A degrees by the phase shifter 54, the oscillator 50 oscillates at a frequency fx that causes a phase delay of A degrees in the resonance characteristics of the resonator 52 and the resistor R12.

Here, in order to widen the variable frequency range of the frequency fx in the variable oscillation frequency mode of the oscillator 50, the resistance value of the resistor R12 may be increased. Further, in order to prevent variation in the frequency fa in the oscillation frequency fixed mode of the oscillator 50, the resistance value of the resistor R11 may be reduced. However, if the resistance value of the resistor R11 is too small, the amplitude of a signal input to the resonator 52 becomes insufficient, driving of the resonator 52 becomes difficult, and waveform distortion easily occurs. The value is compromised. For this reason, the oscillator 50 is not provided with a filter so as to eliminate the phase rotation as much as possible. Accordingly, triple harmonic oscillation is likely to occur, and a countermeasure is required.

Furthermore, when such an oscillator 50 is integrated, an external resonator 52 is required, which requires two pins. Here, the only way to extract the oscillation output from the oscillator 50 is to provide one pin in addition to the two pins, or to use the terminal of the resonator 52 as an output terminal. The smaller the number of integrated circuit pins, the better the density of the integrated circuit.However, if the resonator terminal is shared with the oscillator output terminal to save pins, the oscillation frequency variable mode and the fixed oscillation frequency The level changes greatly depending on the mode. Switching amplification can be performed so that the level becomes the same. However, if an attempt is made to increase the amplitude in the oscillation frequency fixed mode having a low resonance impedance, a large drive current of the crystal as the resonator 52 is required. Is also undesirable because of increased leakage to

[0011]

In the above-described conventional oscillator, in order to prevent the frequency from fluctuating in the oscillation frequency fixed mode of the oscillator, the resistance of a resistor connected in a loop to the resonator may be reduced. . However, if the resistance of the resistor is too small, it becomes difficult to drive the oscillator, the amplitude of the signal input to the resonator becomes insufficient, and the waveform is likely to be distorted. For this reason, no filter is provided, and 3
Double harmonic oscillation is likely to occur. Furthermore, when the terminal of the resonator is shared with the output terminal of the oscillator in order to save pins in an integrated circuit, the level greatly changes between the oscillation frequency variable mode and the oscillation frequency fixed mode.

The present invention eliminates the above-mentioned problems, and in a fixed oscillation frequency mode of an oscillator, the amplitude of a signal input to a resonator can be reduced even when the resistance of a resistor connected in a loop to the resonator is lowered. When the resonator terminal is shared with the oscillator output terminal to save pins, the difference in level between the variable oscillation frequency mode and the fixed oscillation frequency mode is suppressed with a simple circuit configuration. It is an object of the present invention to provide an oscillator that can perform the operation.

[0013]

According to a first aspect of the present invention, an oscillator according to the present invention includes a limiter amplifier for amplifying an input signal and limiting the amplitude of the input signal, the input signal input to the limiter amplifier, and the output output from the limiter amplifier. An adder that performs signal addition, a resonator that outputs a resonance signal from the other end when an output signal from the adder is supplied to one end,
A resonance signal from the resonator is supplied to an input electrode, the input signal to be input to the limiter amplifier is supplied to a common electrode, and an output from an output electrode or a transistor that returns an output equivalent to the output to a limiter amplifier. It is characterized by having.

According to a second aspect of the present invention, there is provided an oscillator according to the present invention, wherein first and second limiter amplifiers for amplifying and limiting the amplitude of an input signal, and wherein the input signal input to the first limiter amplifier and the limiter amplifier An adder for adding the output signal to be output, and an output signal from the adder and a second
An output signal from the limiter amplifier is supplied to one end, a resonator that outputs a resonance signal from the other end, and a resonance signal from this resonator is supplied to the emitter, and an input signal that is input to the first limiter amplifier is A first transistor which is supplied to a base and outputs an output from a collector or an equivalent output to the first limiter amplifier, a resonance signal from the resonator is supplied to an emitter, and a DC voltage is supplied to a base A second transistor for returning an output from the collector or an equivalent output to the second limiter amplifier, and an output from the collector of the second transistor or an equivalent output to the second limiter. The phase shifter is provided on a path returning to the amplifier, and is capable of adjusting the output from the collector of the second transistor or an equivalent output thereof. And a path for supplying the output signal from the adder and the output signal from the second limiter amplifier to the resonator. In the case of the fixed oscillation frequency mode, First switching means for guiding an output signal to the resonator and, in the case of the oscillation frequency variable mode, an output signal from the second limiter amplifier to the resonator;
And a path for supplying to the second transistor. In the case of the oscillation frequency fixed mode, the resonance signal from the resonator is guided to the first transistor. In the case of the oscillation frequency variable mode, the resonance signal from the resonator is supplied. And second switching means for guiding a resonance signal to the second transistor.

[0015]

According to the configuration of the first aspect, the adder adds the input signal input to the limiter amplifier and the output signal output from the limiter amplifier, and the output signal from the adder is connected to one end of the resonator. Since it is supplied, the amplitude of the signal input to the resonator can be sufficiently ensured.

According to the configuration of the second aspect, in the case of the fixed oscillation frequency mode, the adder adds the input signal input to the first limiter amplifier and the output signal output from the first limiter amplifier. In this case, the first switch guides the output signal from the adder to the resonator, and the second switch guides the resonance signal from the resonator to the first transistor. On the other hand, in the case of the oscillation frequency variable mode, the first switch means guides the output signal from the second limiter amplifier to the resonator, and the second switch means transfers the resonance signal from the resonator to the second transistor. Lead. Thus, when the terminal of the resonator is shared with the output terminal of the oscillator in order to save pins, a difference in level between the variable oscillation frequency mode and the fixed oscillation frequency mode can be suppressed with a simple circuit configuration.

[0017]

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

FIG. 1 is a circuit diagram showing an embodiment of an oscillator according to the present invention, which is applied to a crystal oscillator dedicated to a fixed mode.

In FIG. 1, an oscillator 10 includes a limiter amplifier 11, an adder 12, a resonator 13 using a quartz oscillator,
The emitter-collector path of the transistor Tr1 and a band-pass filter (hereinafter, referred to as BPF) 14 are connected in a loop, and the output of the BPF 14 is directly added to the adder 1.
2 to form an oscillation loop.

The oscillator 10 will be described in more detail.
The output signal a1 of the PF14 is an NPN transistor Tr1
And an input terminal of the adder 12 while being amplified and amplitude-limited by the limiter amplifier 11 and supplied to the other input terminal of the adder 12 as an output signal b1. Output signal c1 from the output terminal of adder 12
Is guided to an output terminal 15 for extracting an oscillation output, and is supplied to one end of a resonator 13. Resonator 13
From the other end is guided to the emitter of the NPN transistor Tr1. The emitter of the NPN transistor Tr1 is connected to the DC current source I1. NPN
The collector of the transistor Tr1 is connected to the power supply line via the resistor R1 and to the input terminal of the BPF. As a result, the output signal d1 from the collector of the transistor Tr1 is fed back to the BPF 14.

The BPF 14 performs band filtering of a signal supplied to its input terminal with the center frequency fixed.
The band-filtered signal is output as an output signal a1.

FIG. 2 is a timing chart showing the operation of the oscillator 10. FIG. 2A shows the output signal a1 of the BPF 14, and FIG.
2C shows the output signal c1 of the adder 12, and FIG. 2D shows the output signal d1 from the collector of the transistor Tr1.

The output signal a1 of the BPF 14 is shown in FIG.
As shown in FIG. This output signal a1
Is amplified and amplitude-limited by the limiter amplifier 11,
As shown in FIG. 2B, a rectangular output signal b1 is obtained. This output signal b1 is output by the adder 12 to the output signal a1.
Is added, a sine-wave output signal c1 in which up-shifting and down-shifting are alternately repeated for each half wavelength shown in FIG. 2C is obtained. The resonator 13 is driven by such an output signal c1, and the resonance signal of the resonator 13 is supplied to the emitter of the transistor Tr1. This allows
A resonance signal of the resonator 13 is obtained by a common base amplifier including a transistor Tr1 having an equivalent emitter resistance and a resistance component of the resonator 13 as an emitter resistance Re1 (R1 / Re1).
(R1 is the resistance value of the emitter resistance R1, and Re1 is the resistance value of the collector resistance Re1).
As shown in FIG. 2 (d), the collector signal is fed back to the BPF 14 as a sine wave output signal d1.

According to such an oscillator 10, the adder 1
2, the output signal a1 output from the BPF 14 is added to the output signal b1 output from the limiter amplifier 11, and the output signal c1 from the adder 12 is supplied to one end of the resonator 13. The amplitude of the input signal can be sufficiently ensured. Thus, the resonator 13 of the oscillating resistance co equivalent emitter resistance of the transistor oscillator 13
Only the emitter resistance Re1 due to the above resistance component is sufficient, and it can be made very small. Thus, it is possible to prevent a variation in the oscillation frequency in the oscillation frequency fixed mode, and the frequency is maintained with high accuracy despite the provision of the BPF 14. Since the loop gain is suppressed by the BPF 14, triple harmonics do not oscillate.

FIG. 3 is a circuit diagram showing another embodiment of the oscillator according to the present invention.

In FIG. 3, the oscillator 20 includes a switch 4
By switching between 1 and 42, in the case of the fixed oscillation frequency mode, the limiter amplifier 21, the adder 22, the resonator 23 including the crystal oscillator, the emitter / collector path of the transistor Tr2, and the BPF 24 are connected in a loop to change the oscillation frequency. In the case of the mode, the limiter amplifier 31, the resonator 23 including the crystal oscillator, the emitter / collector path of the transistor Tr3, and the BPF 24 are connected in a loop, so that both the fixed oscillation frequency mode and the oscillation frequency variable mode are used. It is made to correspond to.

The oscillator 20 will be described in more detail.
The output signal a2 of the PF24 is an NPN transistor Tr2
And an input terminal of the adder 22 while being amplified and limited in amplitude by the limiter amplifier 21 and supplied to the other input terminal of the adder 22 as an output signal b2. Output signal c2 from the output terminal of adder 22
Is guided to the first input terminal a1 of the changeover switch 41. The output signal a2 from the BPF 24 is amplified and amplitude-limited by the limiter amplifier 31, and is guided as an output signal b3 to the second input terminal a2 of the changeover switch 41.

The changeover switch 41, the oscillation frequency in the case of variable mode a first input terminal a1 connected to the common terminal c, the second input terminal a2 when the oscillation frequency fixed mode
To the common terminal c.

The common terminal c of the changeover switch 41 is connected to the output terminal 25 for taking out the oscillation output and to one end of the resonator 23. The other end of the resonator 23 is connected to the common terminal c of the changeover switch 42.

The changeover switch 42, the oscillation frequency when the variable mode connects the common terminal c to the first output terminal a1, the oscillation frequency of the common terminal c to the case of the fixed mode second
Output terminal a2.

The first output terminal a1 of the changeover switch 42
Is connected to the emitter of the NPN transistor Tr2.
The emitter of the NPN transistor Tr2 is connected to the DC current source I
2 are connected. The collector of the NPN transistor Tr2 is connected to the power supply line via the resistor R2 and to the input terminal of the BPF 24.

The second output terminal a2 of the changeover switch 42
Is connected to the emitter of the NPN transistor Tr2 via the resistor R3. The emitter of the NPN transistor Tr3 is connected to the DC current source I3. The DC voltage V from the input terminal 27 is connected to the base of the NPN transistor Tr3.
2 are supplied. The collector of the NPN transistor Tr3 is connected to the input terminal of the BPF 24.

The BPF 24 performs band filtering of the signal supplied to the input terminal while the center frequency is controlled by the control voltage V1 from the input terminal 26, and outputs the band-filtered signal as an output signal a2. .

The operation of such an embodiment will be described below.

In the case of the fixed oscillation frequency mode, the changeover switch 41 connects the first input terminal a1 to the common terminal c, and the changeover switch 42 connects the first output input terminal a1 to the common terminal c. Thereby, the oscillator 20
The limiter amplifier 21, the adder 22, the resonator 23, the emitter / collector path of the transistor Tr2 and the BPF 24 are connected in a loop, and the output of the BPF 24 is directly supplied to the adder 12, thereby forming an oscillation loop. Further, the control voltage V1 supplied to the input terminal 26 is kept constant, so that the center frequency of the BPF 24 is kept constant. As a result, circuit connection similar to that of FIG.
The same operation as is performed.

[0036] When the oscillation frequency variable mode, the changeover switch 41 connects the second input terminal a2 to the common terminal c, the changeover switch 42 connects the second output terminal a2 to the common terminal c. Thereby, the BPF 24, the limiter amplifier 31, the resonator 23, the resistor R3, the transistor T
The emitter - collector path of r3 is connected in a loop.
Further, by making the control voltage V1 supplied to the input terminal 26 variable, the center frequency of the BPF 24 can be made variable and the BPF 24 can be used as a phase shifter. The transistor Tr3 is substantially of a grounded base type, and the resonance signal of the resonator 23 supplied via the resistor R3 is represented by the equivalent emitter resistance and the resistance of the resonator 23 as the emitter resistance Re2 (R2 / R
e2) Amplify it by a factor of two (R2 is the resistance value of the collector resistor R2) and output it to the BPF 24. The output of the BPF 24 is fed back to the resonator 23 via the limiter amplifier 31. In this state, when the phase shift amount of the BPF 24 is controlled to A degrees by changing the voltage V1 supplied to the BPF 24, the oscillator 20 generates a frequency that causes a phase delay of A degrees in the resonance characteristics of the resonator 23 and the resistor R3. Oscillates at fX.

According to this embodiment, the same effect as that of the embodiment of FIG. 1 can be obtained in the fixed oscillation frequency mode.
Variable oscillation frequency modes that can be switched on, while the oscillation in the case of fixed frequency mode by adding the output signal a 2 of the output signal b 2 and BPF24 of the limiter amplifier 21 by the adder 22 leading to an output terminal 25 , Oscillation frequency available
In the case of the variable mode, the output signal b3 of the limiter amplifier 31
Is guided to the output terminal 25 as it is, and the difference in level between the oscillation frequency variable mode and the oscillation frequency fixed mode can be suppressed with a simple circuit configuration.

[0038] In the embodiment of FIGS. 1 and 3, is provided with the BPF as a filter to prevent oscillation of the triple harmonic may be provided other than the filter for example, a low-pass filter. Further, in the embodiments of FIGS. 1 and 3, the output from the collector of the transistor is fed back to the limiter amplifier. However, the output from the collector of the transistor, that is, the output from the collector of the transistor may be used. The amplified output or the like may be fed back.

[0039]

According to the present invention, in the oscillation frequency fixed mode of the oscillator, even if the resistance value of the resistor connected in a loop to the resonator is reduced, the amplitude of the signal input to the resonator is sufficiently ensured. Therefore, variation in the oscillation frequency can be prevented, and the frequency can be maintained with high accuracy even when a filter is provided. Since the loop gain is pressed By providing the filter, it is possible to prevent the <br/> oscillation triple harmonics. When the terminal of the resonator is shared with the output terminal of the oscillator in order to save pins, a difference in level between the variable oscillation frequency mode and the fixed oscillation frequency mode can be suppressed with a simple circuit configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an oscillator according to the present invention.

FIG. 2 is a timing chart showing the operation of the oscillator shown in FIG.

FIG. 3 is a block diagram showing another embodiment of the oscillator according to the present invention.

FIG. 4 is a block diagram showing a conventional oscillator.

[Explanation of symbols]

 Reference Signs List 10 oscillator 11 limiter amplifier 12 adder 13 resonator Tr1 transistor 14 BPF

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-26726 (JP, A) JP-A-60-46101 (JP, A) JP-A-62-209907 (JP, A) 21560 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H03B 5/30-5/42

Claims (2)

(57) [Claims] A limiter amplifier for amplifying and limiting the amplitude of an input signal; an adder for adding the input signal input to the limiter amplifier and an output signal output from the limiter amplifier; and an output from the adder. A resonator that outputs a resonance signal from the other end when a signal is supplied to one end; a resonance signal from the resonator is supplied to an input electrode; and the input signal that is input to the limiter amplifier is supplied to a common electrode. A transistor that feeds back an output from an output electrode or an equivalent output to a limiter amplifier. 2. A first and a second limiter amplifier for amplifying and limiting an amplitude of an input signal, and adding the input signal input to the first limiter amplifier and an output signal output from the limiter amplifier. An adder, an output signal from the adder and an output signal from the second limiter amplifier are supplied to one end and a resonance signal is output from the other end, and a resonance signal from the resonator is supplied to the emitter An input signal input to the first limiter amplifier is supplied to a base, and an output from a collector or an output equivalent thereto is fed back to the first limiter amplifier; A resonance signal is supplied to the emitter, a DC voltage is supplied to the base, and an output from the collector or an equivalent output is fed back to the second limiter amplifier. An output from the collector of the second transistor or an output equivalent to the output from the collector of the second transistor; and an output from the collector of the second transistor or an output equivalent to the output from the collector of the second transistor. Phase shift means for performing a phase shift in an adjustable state, provided on a path for supplying an output signal from the adder and an output signal from the second limiter amplifier to the resonator, and in an oscillation frequency fixed mode. First switching means for guiding an output signal from the adder to the resonator in the case, and guiding an output signal from the second limiter amplifier to the resonator in the oscillation frequency variable mode; A path for supplying a resonance signal from the resonator to the first and second transistors. In the case of the fixed oscillation frequency mode, the resonance signal from the resonator is transmitted to the first transistor. Led to register, the oscillator in the case of variable oscillation frequency mode, characterized by comprising a second switch means for guiding the transistors of the second resonance signal from the cavity.