JP3093355U - Voltage controlled oscillator - Google Patents

Abstract

[PROBLEMS] To increase the stability of the oscillation frequency and the linearity of the change of the oscillation frequency with respect to the tuning voltage even if the tuning voltage applied to the varactor diode is lowered, and to increase the C / N of the oscillation signal. I do. SOLUTION: A rectifying circuit 8 including an oscillation transistor 1, a resonance circuit 4 having a varactor diode 4b and coupled between a base and a collector of the oscillation transistor 1, and outputting a negative voltage from an oscillation signal is provided. While applying a negative voltage to the anode of the varactor diode 4b,
A tuning voltage for setting the oscillation frequency was applied to the cathode.

Description

[Detailed description of the device]

[0001]

[Technical field to which the device belongs]

  This invention relates to a voltage controlled oscillator used in a mobile phone or the like.

[0002]

[Prior art]

  A conventional voltage controlled oscillator is shown in FIG. The collector of the oscillation transistor 31 has a high frequency. Wave grounded, between the base and emitter, and between the emitter and ground Capacitance elements 32 and 33 for feedback are respectively connected. In addition, the base has a resonance circuit. One end of 34 is coupled and the other end is grounded. The resonance circuit 34 is an inductance element 34a and a varactor diode 34b connected in parallel thereto, The anode of the ion 34b is grounded. Cathode of varactor diode 34b A tuning voltage V for setting the oscillation frequency is applied from the tuning voltage terminal 35.

[0003]   With the above configuration, the characteristic of the voltage-capacitance value of the varactor diode 34b is shown in FIG. As shown in B, as the tuning voltage V becomes lower, the capacitance value rapidly increases. When the tuning voltage changes in the range of V1 to V2, the change of the capacitance value becomes ΔCa. This The oscillation frequency changes according to the change in the capacitance value of.

[0004]

[Problems to be solved by the device]

  In recent years, the power supply voltage of mobile phones and the like has been lowered to save power. Correspondingly, the power supply voltage used for the voltage controlled oscillator is also low. for that reason , The tuning voltage is inevitably low. As a result, various problems occur. First, , The rate of change of the capacitance value with respect to the voltage is large, so the stability of the oscillation frequency is poor. Turn into. Secondly, the Q of the varactor diode may decrease as the capacitance value increases. Since the quality is high, the C / N of the oscillation signal is deteriorated. Third, the tuning voltage is low As the change in capacitance value becomes more non-linear, the oscillation frequency becomes less linear. .

[0005]   The present invention solves these problems by applying a tuning applied to a varactor diode. Even if the voltage is lowered, the stability of the oscillation frequency and the direct change of the oscillation frequency with respect to the tuning voltage It is intended to improve the linearity and increase the C / N of the oscillation signal.

[0006]

[Means for Solving the Problems]

  As a means for solving the above problems, the present invention is directed to an oscillation transistor and a varactor. It has a diode and is connected between the base and collector of the oscillation transistor. And a rectifier circuit that outputs a negative voltage from the oscillation signal. The negative voltage is applied to the anode of the varactor diode, and the negative voltage is applied to the cathode. A tuning voltage for setting the vibration frequency was applied.

[0007]   Further, a buffer amplifier for amplifying the oscillation signal is provided, and the buffer amplifier is Therefore, the amplified oscillation signal was rectified by the rectification circuit.

[0008]   Also, ground the collector of the oscillation transistor at high frequency and The applied oscillation signal was input to the buffer amplifier.

[0009]

[Embodiment of device]

  The voltage controlled oscillator of the present invention is shown in FIG. The collector of the oscillation transistor 1 has a high frequency. Wave grounded, between the base and emitter, and between the emitter and ground Capacitance elements 2 and 3 for feedback are respectively connected. The base of the resonance circuit 4 One end is coupled and the other end is grounded. Therefore, the resonance circuit 4 has a base and a collector. Is bound in between. The resonance circuit 4 is connected in parallel with the inductance element 4a. Has a varactor diode 4b, and the anode of the varactor diode 4b is for grounding It is grounded at a high frequency by the capacitive element 4c. Cascade of varactor diode 4b A tuning voltage V for setting the oscillation frequency is applied to the mode from the tuning voltage terminal 5.

[0010]   The oscillation signal output from the emitter of the oscillation transistor 1 is sent to the buffer amplifier 6. Therefore, it is amplified and supplied to other circuits. Also, it is amplified by the buffer amplifier 6. The generated oscillation signal is input to the rectifier circuit 8 via the coupling capacitive element 7. Oscillation Since the buffer amplifier 6 is interposed between the transistor 1 and the rectifier circuit 8, the rectifier circuit There is no load variation on the oscillation transistor 1 due to 8.

[0011]   The rectifier circuit 8 has a rectifier diode 8a, a smoothing capacitive element 8b, and a resistor 8c. Then, the cathode of the diode 8a is connected so as to be on the buffer amplifier side. Yo Thus, the rectifier circuit 8 outputs the negative voltage E. This negative voltage is the varactor diode Applied to the anode of the battery 4b.

[0012]   In the above configuration, the negative voltage E is applied to the anode of the varactor diode 4b. Therefore, the characteristic of the voltage-capacity value is as shown by the curve B in FIG. Ie car This is a characteristic obtained by shifting the conventional characteristic indicated by the curve A to the lower side by the voltage E. As a result, When the same tuning voltage as before is applied, the anode of the varactor diode 4b and the cathode The voltage applied to the node increases by E. And the capacity value is also reduced. Also In the voltage range from V1 to V2, the change (gradient) of the capacitance value is slower than before. As a result, the amount of change also decreases to ΔCb.

[0013]   Therefore, the Q of the varactor diode 4b increases and the C / N of the oscillation signal increases. In addition, the linearity of the oscillation frequency with respect to the tuning voltage is improved. In addition, the change in capacitance value is slow Being strict also improves the stability of the oscillation frequency with respect to the tuning voltage. The capacity value Although it becomes smaller, increase the inductance value of the inductance element 4a. By doing so, the oscillation frequency can be corrected.

[0014]

[Effect of device]

  As described above, in the present invention, the oscillation transistor and the varactor diode are used. And a resonance circuit coupled between the base and collector of the oscillation transistor. And a rectifier circuit that outputs a negative voltage from the oscillation signal. A negative voltage is applied to the anode of the cathode and a tuning voltage for setting the oscillation frequency is applied to the cathode. Since the voltage is applied, even if the same tuning voltage as before is applied, the varactor diode The voltage applied between the cathode and the cathode is high. And when the capacity value also decreases In both cases, the change (slope) of the capacitance value becomes slower than in the past.   Therefore, the Q of the varactor diode 4b increases and the C / N of the oscillation signal increases. In addition, the linearity of the oscillation frequency with respect to the tuning voltage is improved. In addition, the change in capacitance value is slow Being strict also improves the stability of the oscillation frequency with respect to the tuning voltage. Note that negative voltage Since it is obtained from the voltage controlled oscillator itself, the configuration is simplified. .

[0015]   In addition, a buffer amplifier that amplifies the oscillation signal is provided, Since the oscillated signal that has been widened is rectified by the rectifier circuit, when a large negative voltage is obtained In both cases, the rectifier circuit does not affect the oscillation transistor.

[0016]   Also, ground the collector of the oscillation transistor at high frequency and output from the emitter. The resonant circuit is affected by the rectifier circuit because the oscillation signal is input to the buffer amplifier. Absent.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a voltage controlled oscillator according to the present invention.

FIG. 2 is a characteristic diagram of change in capacitance value with respect to voltage of varactor diode.

FIG. 3 is a circuit diagram showing a configuration of a conventional voltage controlled oscillator.

[Explanation of symbols]

1 oscillation transistor 2,3 Feedback capacitive element 4 resonance circuit 4a Inductance element 4b Varactor diode 4c Grounding capacitive element 5 Tuning voltage terminal 6 buffer amplifier 7 Capacitive element for coupling 8 Rectifier circuit 8a rectifier diode 8b Smoothing capacitive element 8c Smoothing resistor

Claims (3)

[Scope of utility model registration request] 1. A rectifier circuit that includes an oscillating transistor and a resonant circuit that has a varactor diode and that is coupled between a base and a collector of the oscillating transistor, and that includes a rectifier circuit that outputs a negative voltage from an oscillating signal. The voltage-controlled oscillator, wherein the negative voltage is applied to the anode of and the tuning voltage for setting the oscillation frequency is applied to the cathode. 2. The voltage controlled oscillator according to claim 1, further comprising a buffer amplifier that amplifies the oscillation signal, and the oscillation signal amplified by the buffer amplifier is rectified by the rectifier circuit. 3. The voltage controlled oscillator according to claim 2, wherein a collector of the oscillation transistor is grounded at a high frequency, and an oscillation signal output from the emitter is input to the buffer amplifier.