JPH0525807U - Voltage controlled oscillator - Google Patents

Abstract

(57) [Abstract] [Purpose] In a voltage controlled oscillator that applies a reverse bias voltage to a varactor diode and changes the oscillation frequency by changing the capacitance of the varactor diode due to changes in the bias voltage, even if noise is mixed in the reverse bias voltage. An object is to provide a voltage controlled oscillator that can obtain a stable oscillation frequency. [Structure] The voltage applied to the cathode end and the anode end of the varactor diode is divided into a positive voltage and a negative voltage and applied so that noises at both ends of the varactor diode are canceled.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a means for reducing the influence of noise particularly in a voltage controlled oscillator (VCO) configured to apply a reverse bias voltage to a varactor diode and change the oscillation frequency by the reverse bias voltage.

[0002]

[Prior Art]

 FIG. 3 shows an example of the configuration of a conventional VCO of this type, where 1 is a frequency control voltage input terminal, 2 is an RF output terminal, 3 is a power supply input terminal, 4 is a control power supply, and C is a power supply input terminal.₁, C₂, C₃, C_Four, C_Five, C₆Is a capacitor, D₁Is a varactor diode, L₁Is a coil, Q₁Transistor, R₁, R₂, R₃, R_FourIs resistance. The capacitor that determines the oscillation frequency in the LC oscillator is a varactor diode D. ₁ Instead of this varactor diode D₁Reverse bias voltage is applied to the varactor diode D by changing the reverse bias voltage.₁The configuration is such that the oscillation frequency can be changed by changing the capacitance of.

[0003]

[Problems to be solved by the device]

In the conventional VCO of this type, as described above, since the reverse bias voltage of the varactor diode D ₁ is applied only to one electrode end, the reverse bias voltage has a noise as shown in the figure. When 5 is mixed, if the oscillation frequency fluctuates due to this noise 5 or if the noise 6 shown in the figure occurs in the control power supply 4, the noise 6 is directly applied to the varactor diode D ₁ and the oscillation signal is generated. However, there was a problem that the C / N ratio of was deteriorated. The present invention has been made in order to solve the above problems, and the noise mixed in the reverse bias voltage or the noise generated in the control power supply causes the oscillation frequency to fluctuate drastically and the C / N ratio of the oscillation signal to deteriorate sharply. The goal is to provide a VCO that is free of charge.

[0004]

[Means for Solving the Problems]

 In order to achieve the above object, the VCO of the present invention can apply a positive voltage and a negative voltage as reverse bias voltages to the cathode end and the anode end of a varactor diode, respectively, and change the potential difference between the cathode end and the anode end. This is a configuration that can be done.

[0005]

[Action]

 With the above configuration, when the noise 5 is mixed in the reverse bias voltage, the varactor diode D₁In-phase noise is applied to both ends of the varactor diode D ₁ Since the potential difference between the cathode end and the anode end of does not change, the oscillation frequency does not change. Further, when noise is generated in the control power supply, noise on the positive voltage side and noise in-phase component on the negative voltage side are similarly canceled, and deterioration of the C / N ratio of the oscillation signal is reduced.

[0006]

【Example】

FIG. 1 shows the structure of an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 3 indicate the same or corresponding ones, 1a and 1b are frequency control voltage input terminals, 4a is a control power source, C ₇ and C ₈ are capacitors, and R ₅ and R ₆ are resistors. is there. A positive voltage and a negative voltage are supplied from the control power source 4a to the frequency control voltage input terminals 1a and 1b, respectively, and the supplied positive voltage and negative voltage are supplied to the cathode terminal of the varactor diode D ₁ via the resistors R ₅ and R ₆ , respectively. Is applied to the anode end and the potential difference between the cathode end and the anode end can be changed by the control power supply 4a. The capacitors C ₇ and C ₈ are RF bypass capacitors.

When the reverse bias voltage application configuration as described above is adopted, when noise 5 is mixed between the control power supply 4a and the frequency control voltage input terminals 1a and 1b, noise of the same phase is generated at both ends of the varactor diode D _1. It is applied and the noise component is canceled. In this case, it is necessary to arrange the reverse bias voltage application line in the same path. When noise is generated in the control power supply 4a, the in-phase component of noise on the positive voltage side and noise on the negative voltage side are canceled. In this case, if the individual power supplies of the control power supply 4a have the same configuration, the generated noise components have the same tendency, and the effect is great.

FIG. 2 shows an example of the configuration of the reverse bias voltage application circuit portion in the embodiment using two varactor diodes.

[0009]

[Effect of the device]

 As described above, according to the present invention, it is possible to reduce the influence of noise mixed in the bias voltage control system and noise generated in the control power supply, and it is possible to achieve the effects of low noise and high C / N. Is large.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the structure of an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a configuration of a reverse bias voltage applying circuit portion in an embodiment using two varactor diodes.

FIG. 3 is a circuit diagram showing a configuration of an example of a conventional VCO of this type.

[Explanation of symbols]

1a, 1b Frequency control voltage input terminal 2 RF output terminal 3 Power supply input terminal 4a Control power supply 5, 6 Noise C ₂ , C ₃ , C ₄ , C ₅ , C ₆ , C ₇ , C ₈ Capacitor D ₁ Varactor diode L ₁ Coil Q ₁ transistor R ₂ , R ₃ , R ₄ , R ₅ , R ₆ resistance

Claims (1)

[Scope of utility model registration request] 1. A voltage-controlled oscillator having a structure in which a reverse bias voltage is applied to a varactor diode and the oscillation frequency can be changed by the reverse bias voltage, wherein a positive bias voltage is applied to the cathode end and an anode end of the varactor diode, respectively. A voltage-controlled oscillator characterized in that a voltage and a negative voltage are applied and a potential difference between the cathode end and the anode end can be changed.