JP2010278734A - Voltage controlled oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage controlled oscillator for reducing the influence of external noise input from a power supply line, or the like. <P>SOLUTION: A Colpitts oscillator is formed by connecting a first feedback capacitor 12 between the base-emitter of an oscillation transistor 11, connecting a second feedback capacitor 13 between the emitter-collector of the oscillation transistor 11 and connecting an inductor 14 between the base-collector of the oscillation transistor 11. A collector bias resistor 30 is connected between the collector of the oscillation transistor 11 and a direct current power supply terminal 18, and one end of the collector bias resistor 30 is grounded through a capacitor 19. A filter circuit with a choke inductor 31 and a capacitor 32 connected in series is connected between the collector and the base of the oscillation transistor 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a voltage controlled oscillator that performs voltage control of an oscillation frequency.

  Conventionally, a voltage-controlled oscillator that controls an oscillation frequency by a control voltage is known. FIG. 5 is a configuration diagram of a conventional voltage controlled oscillator. In the voltage controlled oscillator 10 shown in FIG. 1, a first feedback capacitor 12 is connected between the emitter and base of the oscillation transistor 11, and a second feedback capacitor 13 is connected between the collector and emitter of the oscillation transistor 11. An inductor 14 is connected between the base and collector of the oscillation transistor 11.

  The emitter of the oscillation transistor 11 is grounded via an emitter bias resistor 15 and connected to an output terminal 17 (OSCout) via a DC cut capacitor 16. The collector of the oscillating transistor 11 is connected to the DC power supply terminal 18 (Vcc) and grounded at a high frequency via a capacitor 19. The base of the oscillation transistor 11 is connected to a DC power supply terminal 18 via a voltage dividing resistor 20 and grounded via a voltage dividing resistor 21. A resonance circuit 23 is connected to the base of the oscillation transistor 11 via a DC cut capacitor 22.

  The resonance circuit 23 is configured as a parallel resonance circuit formed by connecting an inductor 14 configured by a stripline and a capacitor 24 in parallel. One end of the inductor 14 and one end of the capacitor 24 are connected, and the other end of the inductor 14 and the other end of the capacitor 24 are grounded. A varactor diode 26 is connected in parallel to the parallel resonant circuit 23 via a capacitor 25. A voltage control terminal 28 (Vctl) is connected to a connection point between the capacitor 25 and the varactor diode 26 via a choke inductor 27. The power control terminal 28 is grounded via a bypass capacitor 29.

  In the voltage controlled oscillator 10 configured as described above, the resonance frequency of the resonance circuit 23 is controlled in accordance with the voltage control signal Vctl applied to the cathode of the varactor diode 26, and the resonance signal is transmitted to the base of the oscillation transistor 11. To be applied. Then, an oscillation signal is output from the emitter of the oscillation transistor 11 via the DC cut capacitor 16.

  By the way, as a method for suppressing the spurious of the voltage controlled oscillator, there is known a voltage controlled oscillator that suppresses the occurrence of spurious by suppressing the change width of the control voltage applied to the varactor diode (see, for example, Patent Document 1).

JP 2006-352423 A

  However, the conventional voltage controlled oscillator cannot suppress the influence of external noise input from the power supply line connected to the collector of the oscillation transistor.

  The present invention has been made in view of this point, and an object thereof is to provide a voltage controlled oscillator that can reduce the influence of external noise input from a power supply line or the like.

  The voltage controlled oscillator of the present invention includes an oscillation circuit having an oscillation transistor, an emitter resistor connected between the emitter and ground of the oscillation transistor, a collector resistor connected between a collector and a power source of the oscillation transistor, and the collector A bypass capacitor provided between a resistor and a ground; and a filter circuit provided between a collector and a base of the oscillation transistor.

  According to this configuration, the noise component included in the oscillation signal can be canceled out by the noise component having a phase different from that of the noise component, so that the noise component of the oscillation signal can be reduced. Further, since the frequency band of the noise component passing through the filter circuit can be selected by adjusting the filter characteristics, the noise component can be reduced without attenuating the oscillation frequency component.

  The voltage controlled oscillator of the present invention includes an oscillation circuit having an oscillation transistor, an emitter resistor connected between the emitter and ground of the oscillation transistor, a collector resistor connected between a collector and a power source of the oscillation transistor, and the collector A bypass capacitor provided between the resistor and the ground and a filter circuit provided between the collector and the emitter of the oscillation transistor are provided.

  According to this configuration, the noise component included in the oscillation signal can be canceled by the noise component having a phase different from that of the noise component, so that the noise component of the oscillation signal can be reduced. Further, since the frequency band of the noise component passing through the filter circuit can be selected by adjusting the filter characteristics, the noise component can be reduced without attenuating the oscillation frequency component.

  In the voltage controlled oscillator according to the present invention, the oscillation circuit includes a first feedback capacitor connected between a base and an emitter of the oscillation transistor and a second feedback capacitor connected between the emitter and the ground of the oscillation transistor. This is a Colpitts type oscillation circuit comprising a feedback capacitor and an inductor connected between the base and ground of the oscillation transistor.

  According to this configuration, since it can be configured by a Colpitts type oscillation circuit, an oscillation signal having a waveform close to a sine wave can be obtained.

  In the voltage controlled oscillator according to the present invention, the oscillation circuit includes a base capacitor provided between a base and a ground of the oscillation transistor, and a first feedback capacitor connected between a base and an emitter of the oscillation transistor. A Colpitts oscillation circuit comprising a second feedback capacitor connected between the emitter and ground of the oscillation transistor and an inductor connected between the collector and ground.

  According to this configuration, even in the grounded Colpitts oscillation circuit, the noise component included in the oscillation signal can be canceled by the noise component having a phase different from that of the noise component, so that the noise component of the oscillation signal is reduced. be able to.

  In the voltage-controlled oscillator according to the present invention, the filter circuit is a band-pass filter that passes a frequency band of noise.

  According to this configuration, since the frequency band of the noise component can be selectively passed, the attenuation of the oscillation frequency can be suppressed and the noise component overlapping the oscillation signal can be canceled.

  In the voltage-controlled oscillator according to the present invention, the filter circuit includes a series resonance circuit in which a filter inductor, a filter capacitor, and the collector resistor are connected in series.

  According to this configuration, since the frequency band that can be removed by the series resonance circuit can be expanded, the frequency band from which noise can be removed can be expanded.

  In the voltage controlled oscillator according to the present invention, the filter circuit is a band elimination filter that cuts off a band of an oscillation frequency.

  According to this configuration, since the oscillation frequency band can be selectively removed, the attenuation of the oscillation signal can be suppressed and the noise component can be canceled.

  In the voltage controlled oscillator according to the present invention, the filter circuit may include a filter inductor and a filter capacitor constituting the band elimination filter connected in series between the signal line and the ground. According to this configuration, the band elimination filter circuit can be configured with a simple circuit configuration.

  An object of the present invention is to provide a voltage controlled oscillator that can reduce the influence of external noise input from a power supply line or the like.

1 is a configuration diagram of a voltage controlled oscillator according to a first embodiment of the present invention. FIG. It is a block diagram of the voltage controlled oscillator which concerns on the modification of the 1st Embodiment of this invention. It is a block diagram of the voltage controlled oscillator which concerns on the other modification of the 1st Embodiment of this invention. It is a block diagram of the voltage controlled oscillator which concerns on the 2nd Embodiment of this invention. It is a block diagram of the voltage control oscillator of a prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a configuration diagram of a voltage controlled oscillator according to the first embodiment. As shown in the figure, a voltage controlled oscillator 1 according to the present embodiment includes an oscillation transistor 11, a first feedback capacitor 12 connected between the emitter and base of the oscillation transistor 11, and the emitter and base of the oscillation transistor 11. The circuit is configured as a collector-grounded Colpitts oscillation circuit including a second feedback capacitor 13 connected between the collectors and an inductor 14 connected between the collector and base of the oscillation transistor 11. However, the present invention is not limited to the Colpitts type oscillation circuit, and can be applied to any oscillation circuit including an oscillation transistor.

  A collector bias resistor 30 is connected between the collector of the oscillation transistor 11 and the power supply terminal 18 (Vcc). One end of the collector bias resistor 30 is connected to the collector of the oscillation transistor 11, and the other end is connected to the power supply terminal 18 and grounded via the capacitor 19. The collector of the oscillation transistor 11 is connected to the base of the oscillation transistor 11 via the filter circuit 31. The filter circuit 31 includes a choke inductor 32 having one end connected to the collector of the oscillation transistor 11, one electrode connected to the other end of the choke inductor 32, and a capacitor 33 having the other electrode connected to the base of the oscillation transistor 11. It is comprised by the series resonance circuit which consists of. Thus, the voltage controlled oscillator 1 is provided with a path for feeding back a signal whose phase is inverted between the collector and base and between the emitter and base of the oscillation transistor 11.

  The filter circuit 31 is composed of an LC series resonance circuit, and adjusts the pass band to match the band of external noise input from the power supply line to the emitter of the oscillation transistor 11. When the filter circuit 31 is configured with a low-pass filter, a frequency lower than the oscillation frequency may be passed. Since other configurations are the same as those of the voltage controlled oscillator 10 shown in FIG. 5, the same reference numerals are given and the description thereof is omitted.

  Next, the operation of the voltage controlled oscillator 1 according to the present embodiment will be described. A resonance frequency signal corresponding to the voltage control signal Vctl applied to the resonance circuit 23 is applied to the base of the oscillation transistor 11. The oscillation transistor 11 oscillates by a resonance signal applied to the base. A current corresponding to the resonance signal applied to the base flows between the collector and emitter of the oscillation transistor 11, and the oscillation signal is extracted from the emitter. At this time, part of the oscillation signal is fed back to the base of the oscillation transistor 11 via the capacitor 12 provided on the emitter side of the oscillation transistor 11. External noise input from the power supply line is phase-inverted between the collector and emitter of the oscillation transistor 11 and input to the base via the capacitor 12. At this time, the external noise input from the power supply line and branched to the filter circuit 31 side is input to the base through the filter circuit 31 without being phase-inverted.

  Since the external noise input to the base through the filter circuit 31 is not phase-inverted, the phase-inverted external noise input to the base via the feedback circuit and the external noise input to the base via the filter circuit 31 are canceled out. The As a result, external noise is removed from the resonance signal applied to the base of the oscillation transistor 11, and an oscillation signal that is not affected by the noise is output via the DC cut capacitor 16. Since the filter circuit 31 is set to pass only the frequency band of the noise component, the oscillation frequency component is not attenuated and only the noise component can be removed.

  Thus, in the present embodiment, the external noise input from the power supply line is input to the base of the oscillation transistor 11 via the filter circuit 31 without phase inversion. For this reason, since the external noise fed back to the base in the state of phase inversion through the oscillation transistor 11 can be canceled by the external noise that does not invert the phase, the external noise can be suppressed and the voltage controlled oscillator 1 that is not affected by the external noise can be provided. Can be configured.

  Next, a modification of the oscillation control circuit will be described with reference to FIG. The voltage controlled oscillator 2 is an example in which a filter circuit 34 is connected between the collector and emitter of the oscillation transistor 11. The filter circuit 34 is configured as an LC series resonance circuit including an inductor 35 and a capacitor 36. One end of the inductor 35 is connected to the collector of the oscillation transistor 11, and the other end is connected to one electrode of the capacitor 36. The other electrode of the capacitor 36 is connected to the emitter of the oscillation transistor 11. The filter circuit 34 has the same filter characteristics as the filter circuit 31. The other parts are configured in the same manner as the voltage controlled oscillator 1 shown in FIG.

  Next, the operation of the voltage controlled oscillator 2 will be described. External noise input from the power supply line passes through between the collector and emitter of the oscillation transistor 11 and is phase-inverted. A part of the external noise is transmitted to the emitter side through the filter circuit 34 without passing through the oscillation transistor 11. The external noise accompanying phase inversion output from the emitter side of the oscillation transistor 11 and the external noise transmitted to the emitter side without phase inversion via the filter circuit 34 are canceled out. As a result, external noise is removed from the resonance signal applied to the base of the oscillation transistor 11, and an oscillation signal that is not affected by the noise is output via the DC cut capacitor 16.

  As described above, even when the filter circuit 34 is connected between the collector and the emitter of the oscillation transistor 11, the external noise that is phase-inverted by transmitting a part of the external noise input from the power supply line to the emitter side without phase-inversion. Since it can cancel out, external noise can be removed from the signal fed back to the base of the oscillation transistor 11.

  Next, another modification will be described with reference to FIG. In the voltage controlled oscillator 3 of this modification, a trap circuit 37 is connected between the collector and base of the oscillation transistor 11. The trap circuit 37 includes capacitors 38 and 39 connected in series, and a series circuit including an inductor 40 and a capacitor 41 connected in series between a connection point between the capacitors 38 and 39 and the ground. . One electrode of the capacitor 38 is connected to the collector of the oscillation transistor 11, and the other electrode is connected to one electrode of the capacitor 39. The other electrode of the capacitor 39 is connected to the base of the oscillation transistor 11. One end of the inductor 40 is connected to a connection point between the other electrode of the capacitor 38 and one electrode of the capacitor 39, and the other end is grounded via the capacitor 41 at a high frequency. The trap circuit 37 has a trap position set at the oscillation frequency, and passes signals other than the oscillation frequency component to the base side of the oscillation transistor 11. The other parts are configured in the same manner as the voltage controlled oscillator 1 shown in FIG.

  Next, the operation of the voltage controlled oscillator 3 will be described. External noise input from the power supply line is phase-inverted between the collector and emitter of the oscillation transistor 11 and input to the base via the feedback capacitor 12. Further, part of the external noise input from the power supply line is input to the trap circuit 37. The trap circuit 37 suppresses and blocks the oscillation frequency component, and external noise existing in a band other than the oscillation frequency is input to the base of the oscillation transistor 11 through the trap circuit 37.

  Since the external noise input to the base through the trap circuit 37 is not phase-inverted, the phase inversion noise input to the base via the feedback circuit and the external noise input to the base via the trap circuit 37 are canceled out. As a result, an oscillation signal from which external noise has been removed from the emitter of the oscillation transistor 11 is output via the DC cut capacitor 16. Further, by setting the trap circuit 37 as a filter characteristic to trap the oscillation frequency band, only the noise component can be removed without canceling the oscillation signal.

  Thus, even when the trap circuit 37 is connected between the collector and base of the oscillation transistor, it is possible to suppress external noise input from the power supply line.

  Further, in the first embodiment of the present invention, a frequency band that can be removed by a series resonance circuit by connecting a series resonance circuit (filter circuit) and a collector bias resistor in series and adjusting the resistance value of the collector bias resistor. Can be enlarged.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 4 is a configuration diagram of the voltage controlled oscillator 4 according to the second embodiment of the present invention. As shown in the figure, the voltage-controlled oscillator 4 is configured as a grounded-base Colpitts oscillation circuit, and is configured in the same manner as the voltage-controlled oscillator 1 with respect to the portion preceding the resonance circuit 23.

  In the present embodiment, the base of the oscillation transistor 51 is grounded at a high frequency via a grounding capacitor 54. The collector of the oscillation transistor 51 is connected to the resonance circuit 23 via the capacitor 22, and the emitter of the oscillation transistor 51 is connected to the output terminal 53 via the DC cut capacitor 52. The base of the oscillation transistor 51 is connected to the power supply terminal 18 via a voltage dividing resistor 55 and grounded via a voltage dividing resistor 56. The emitter and base of the oscillation transistor 51 are connected via a capacitor 57. The collector and base of the oscillation transistor 51 are connected via a capacitor 58. The collector and emitter of the oscillation transistor 51 are connected via a capacitor 59.

  The collector of the oscillation transistor 51 is connected to the power supply 18 via an inductor 60 and a collector bias resistor 61 in series. One end of the inductor 60 is connected to the collector of the oscillation transistor 51, and the other end is connected to one end of the collector bias resistor 61. The other end of the collector bias resistor 61 is connected to the power supply terminal 18 and is grounded at a high frequency via a capacitor 62.

  A connection point between the collector bias resistor 61 and the inductor 60 is connected to the emitter of the oscillation transistor 51 via the filter circuit 63. The filter circuit 63 is configured as an LC series resonance circuit including an inductor 64 and a capacitor 65. The filter circuit 63 has a filter characteristic that matches the filter characteristic with a band of external noise input from the power supply line to the emitter of the oscillation transistor 51. The connection point between the inductor 64 and the capacitor 65 is connected to one end of a resistor 66 and the other end of the resistor element 66 is grounded.

  Next, the operation of the voltage controlled oscillator 4 according to the second embodiment will be described. The resonance circuit 23 applies a signal having a resonance frequency corresponding to the voltage control signal Vctl to the collector of the oscillation transistor 51. The oscillation transistor 51 oscillates by a resonance signal applied to the collector.

  External noise input from the power supply line passes through the collector-emitter of the oscillation transistor 51 via the collector bias resistor 61 and the inductor 60 and is output from the emitter side. At this time, the external noise that has been input from the power supply line and branched to the filter circuit 63 is transmitted to the emitter side of the oscillation transistor 51 through the filter circuit 63. Since the filter circuit 63 has a filter characteristic that passes only the noise component and blocks the oscillation frequency component, it passes noise from the power supply line, but blocks the passage of the oscillation frequency component on the collector side.

  Since the external noise transmitted to the emitter side of the oscillation transistor 51 through the filter circuit 63 is not phase-inverted, the phase-inversion external noise output via the oscillation transistor 51 and the external noise input via the filter circuit 63 Is offset. As a result, an oscillation signal from which external noise has been removed is output via the DC cut capacitor 52. Note that the filter circuit 63 can remove only the noise component without canceling the oscillation signal by setting so that only the frequency band of the noise component passes.

  As described above, even in the voltage controlled oscillation circuit constituted by the base-grounded Colpitts oscillation circuit, the external noise entering from the power supply line can be suppressed, and the voltage controlled oscillator which is not affected by the external noise can be configured.

  In the present embodiment, since the inductor 64 used for the grounded emitter of the oscillation transistor 51 is used as the inductor 64 of the filter circuit 63, the number of parts can be reduced. Further, by adjusting the ratio of the resistance values of the collector-side inductor 60 and the emitter-side inductor 64, the noise input from the power supply line can be adjusted, so that the noise removal efficiency can be improved.

  Further, in the second embodiment of the present invention, a frequency band that can be removed by a series resonance circuit by connecting a series resonance circuit (filter circuit) and a collector bias resistor in series and adjusting the resistance value of the collector bias resistor. Can be enlarged.

  In the voltage controlled oscillators 1 to 4 described above, the feedback capacitor is not a discrete component but can be configured by a substrate pattern or a capacitance difference between the collector and the emitter of the oscillation transistor 11. For this reason, the circuit can be configured at low cost and can be configured simply.

  The present invention is not limited to the above-described embodiment and its modifications. In addition, various modifications can be made without departing from the scope of the present invention.

1, 2, 3, 4, 10 Voltage controlled oscillator 11, 51 Oscillation transistor 12, 13 Feedback capacitor 14, 27, 32, 35, 40, 60, 64 Inductor 15, 20, 21, 30, 55, 56, 61, 66 Resistance 16, 19, 22, 24, 25, 29, 33, 36, 38, 39, 41, 52, 54,
57 to 59, 62, 65 Capacitor 17, 53 Output terminal 18, 28 Power supply terminal 23 Resonant circuit 26 Varactor diode 31, 34, 63 Filter circuit 37 Trap circuit

Claims (8)

An oscillation circuit having an oscillation transistor;
An emitter resistor connected between the emitter and ground of the oscillation transistor;
A collector resistor connected between a collector and a power source of the oscillation transistor;
A bypass capacitor provided between the collector resistor and the ground;
And a filter circuit provided between a collector and a base of the oscillation transistor. An oscillation circuit having an oscillation transistor;
An emitter resistor connected between the emitter and ground of the oscillation transistor;
A collector resistor connected between a collector and a power source of the oscillation transistor;
A bypass capacitor provided between the collector resistor and the ground;
And a filter circuit provided between a collector and an emitter of the oscillation transistor. The oscillation circuit is
A first feedback capacitor connected between the base and emitter of the oscillation transistor;
A second feedback capacitor connected between the emitter and ground of the oscillation transistor;
3. The voltage controlled oscillator according to claim 1, wherein the voltage controlled oscillator is a Colpitts oscillation circuit including an inductor connected between a base of the oscillation transistor and a ground. The oscillation circuit is
A base capacitor provided between the base and ground of the oscillation transistor;
A first feedback capacitor connected between the base and emitter of the oscillation transistor;
A second feedback capacitor connected between the emitter and ground of the oscillation transistor;
3. The voltage controlled oscillator according to claim 1, wherein the voltage controlled oscillator is a Colpitts oscillation circuit including an inductor connected between the collector and the ground.   5. The voltage controlled oscillator according to claim 1, wherein the filter circuit is a band-pass filter that passes a frequency band of noise.   6. The voltage controlled oscillator according to claim 5, wherein the filter circuit comprises a series resonance circuit in which a filter inductor, a filter capacitor, and the collector resistor are connected in series.   5. The voltage controlled oscillator according to claim 1, wherein the filter circuit is a band elimination filter that cuts off a band of an oscillation frequency. 8. The voltage controlled oscillator according to claim 7, wherein in the filter circuit, a filter inductor and a filter capacitor constituting the band elimination filter are connected in series between a signal line and a ground.

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