JPS6132603A - Voltage-controlled oscillation circuit - Google Patents

Abstract

PURPOSE:To secure a necessary control voltage range by providing a means which rectifies part of the output of the voltage-controlled oscillation circuit and generates an output voltage, and supplying the output voltage or voltage obtained by adding a source voltage to said output voltage to a control element as a bias voltage. CONSTITUTION:Part of the oscillation output is rectified through diodes D2 and D3 and smoothed by a capacitor C1 to develop a voltage V2 which has the opposite polarity of the source voltage across a load resistance R2. A varactor diode D1 is applied with a voltage equal to +V1 at its cathode through a bias resistance R1 and also applied with a voltage -V2 at its anode. A bias voltage to the varactor diode is therefore V1+V2 and a control input is given a voltage range from +V1 to -V2. Therefore, when the source voltage +V1 is supplied from, for example, a single power source and extremely low, a sufficient bias voltage is applied to the varactor diode and the circuit is used in an excellent linearity state.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a voltage controlled oscillation circuit (VCO) whose frequency can be controlled by voltage input, and particularly to a voltage controlled oscillation circuit with an expanded control voltage range. It is.

[Conventional technology]

A voltage controlled oscillator circuit changes the capacitance of a control element, such as a variable capacitance diode, in response to a voltage input, thereby controlling the oscillation frequency, and has already been widely used.

Generally, in a voltage controlled oscillator circuit, the oscillation frequency is determined by applying a fixed bias voltage to a variable capacitance diode, which is the control element, or the oscillation frequency is modulated by adding an alternating current signal superimposed on this bias voltage. I am trying to generate output using

Conventionally, a part of the power supply voltage has often been divided and used as a bias power supply for such a voltage controlled oscillation circuit. However, the control voltage vs. oscillation frequency characteristic of variable capacitance diodes generally forms a certain curve, and the range in which good linearity can be ensured is limited, requiring a relatively large bias voltage value of, for example, several volts. There are many cases.

Therefore, if the power supply voltage is low and only a low value can be given as the bias voltage, not only will linearity be degraded, but the control input cannot be applied beyond the bias voltage value, so the desired control range cannot be adjusted. The problem was that it could not be secured.

For example, in portable devices using a single power supply,
If only a relatively low value is available for the power supply voltage, use a separate D as a bias power supply for the voltage controlled oscillator circuit.
Methods such as providing a C-DC converter have been used, but this naturally complicates the configuration of the device and is inevitably disadvantageous in terms of cost.

[Problem that the invention seeks to solve]

The present invention aims to solve the problems of the prior art as described above, and in a voltage controlled oscillator circuit using a control element whose value changes depending on the control voltage, a separate DC-DC converter is required even when the power supply voltage is low. The purpose of this invention is to provide a sufficient bias voltage to the control element to ensure a required control voltage range without using a control element.

[Means for solving problems]

In the voltage controlled oscillator circuit of the present invention, a part of the oscillation output is rectified to generate a voltage, which is applied to the control element as a bias power supply, or this voltage is added to the power supply voltage and used as the bias voltage of the control element. use.

[For production]

In the voltage controlled oscillator circuit of the present invention, the voltage obtained by rectifying a part of the oscillation output or the voltage obtained by adding this voltage to the power supply voltage is used as the bias voltage of the control element, so the voltage control The control voltage range in the oscillation circuit is expanded.

〔Example〕

FIG. 1 shows the configuration of an embodiment of the voltage controlled oscillation circuit of the present invention. In the same figure, TRI is a transistor, D
l is a variable capacitance diode, D2. D3 is a diode, L
1 is a coil, R1-R5 are resistors, and 01 to C6 are capacitors.

In Fig. 1, the collector of the transistor TRI is grounded in an AC manner, and by dividing the AC voltage between its base and ground by capacitors C3 and C4 and feeding it back to the emitter, the inductance and variable capacitance of the coil L1 are An oscillation output with a frequency approximately determined by the capacitance of the diode D1 is generated at the emitter. At this time, +1 is applied to the transistor TRI as a power source.

Generates polarity voltage -■2. Variable capacitance diode D1
A voltage equal to +7 times is applied to one electrode (cathode) through a bias resistor R1, and a voltage -V2 is applied to the other electrode (anode).

In the circuit shown in Figure 1, the bias voltage for the variable capacitance diode is (v, +v2), and the control inputs are +■,
Therefore, even if the power supply voltage +V is extremely low due to a single power supply, a sufficient bias voltage can be given to the variable capacitance diode to ensure linearity. Can be used in good condition.

In other words, in FIG. 1, if a single power supply voltage 10.1 is also supplied to the preceding stage control circuit (not shown) connected to the control input, the maximum voltage that can be output from that control circuit is from +1 to ground. There is a range of levels. Therefore, when the control voltage is close to +1, a sufficient bias voltage is applied to the variable capacitance diode D1, and good linearity is maintained. Also, even if the control voltage approaches the ground level, -
Since the bias voltage v2 is applied, the linearity can still be maintained in a region with good linearity. As described above, according to the circuit shown in FIG. 1, a voltage controlled oscillation circuit with good linearity can be constructed.

FIG. 2 shows the configuration of another embodiment of the voltage controlled oscillation circuit of the present invention. In this figure, the same parts as in FIG. 1 are indicated by the same symbols, and R6 is a resistor.

In the circuit of Fig. 2, capacitor C1, resistor R2,
One end of diode D3 is connected to the power supply voltage +■ instead of being grounded.
Connected to 1. Also, diode D3. D4 is the first
It is connected in the opposite direction to the circuit shown in the figure, and rectifies the output to generate a voltage of +v2 across the load resistor R2.

Therefore, a bias voltage of (v, +v2) is applied to the variable capacitance diode D1. In the circuit of Figure 2, a voltage range from (V 1 + V 2 ) to ground level can be given as a control input, and in this case, even when the supply voltage +V1 is very low, the voltage range for the variable capacitance diode is It can be used with good linearity by applying a sufficient bias voltage.

In the above embodiments, the case where a variable capacitance diode is used as a control element has been described, but the present invention is not limited to this case. Needless to say, the present invention can be applied to voltage controlled oscillation circuits.

Further, it is natural that the bias voltage of the control element that can be used is not limited to the voltage obtained by adding the power supply voltage to the rectified voltage of the oscillation output, but only the rectified voltage of the output may be used.

〔Effect of the invention〕

As explained above, according to the voltage controlled oscillator circuit of the present invention, the bias voltage applied to the control element can be increased to exceed the power supply voltage, and therefore the control voltage range in the voltage controlled oscillator circuit can be expanded, and even over a wide range. It is possible to improve linearity over the period.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are diagrams each showing the configuration of an embodiment of the voltage controlled oscillation circuit of the present invention.

Claims (1)

[Claims] In a voltage controlled oscillation circuit that includes a control element whose value changes according to a control input voltage and whose oscillation frequency is controlled by the control element, a part of the output of the voltage controlled oscillation circuit is rectified to adjust the output voltage. A voltage controlled oscillator circuit comprising means for generating the output voltage or a voltage obtained by adding the output voltage and a power supply voltage to the control element as a bias voltage.