JPH06140837A - Voltage controlled oscillator - Google Patents

Abstract

PURPOSE:To unnecessitate the setting of an oscillation frequency range from the outside or the adjustment of the lower limit and upper limit of each oscillation frequency range by automatically controlling a switching signal for the oscillation frequency range of the voltage controlled oscillator inside a system. CONSTITUTION:When there are the two steps of the current oscillation frequency range and a control voltage VT is equal to a threshold value VT1, for example, the oscillation frequency range is turned to three steps and lowered by oscillation frequency range switching elements 12 and 13. When the control voltage VT is equal to a threshold voltage VT2, the oscillation frequency range is increased by turning the oscillation frequency range to the first step. Namely, the oscillation frequency range of the voltage controlled oscillator is set by inputting a control voltage 4 and a threshold voltage 7 to a voltage comparator 8, inputting the output to a control circuit 9 and controlling the switching elements 12 and 13 with the circuit 9. Thus, since the oscillation frequency range of the voltage controlled oscillator is set, the oscillation frequency range can be automatically controlled over wide ranges inside the system without any control signal from the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillator having a wide oscillation frequency range by switching signals of the oscillation frequency range.

[0002]

2. Description of the Related Art In recent years, phase locked loop (hereinafter referred to as PLL) circuits have been used in various fields such as frequency synthesizers and demodulation circuits. Here, the voltage controlled oscillator plays an important role as an oscillator in this PLL circuit. Further, in recent years, demand for a voltage controlled oscillator having a wide oscillation frequency range as a frequency synthesizer is increasing.

A conventional method of switching the oscillation frequency range of a voltage controlled oscillator having a wide oscillation frequency range by a switching signal of the oscillation frequency range will be described below.

FIG. 6 is a block diagram of a conventional voltage controlled oscillator having a wide oscillation frequency range using a method of switching the oscillation frequency range. FIG. 6 shows the oscillation stage 1 and
It is composed of an amplification stage 2 and a buffer 3. Further, in FIG. 6, 4 is a control voltage of the voltage controlled oscillator, the output voltage from the buffer is 6, and the control signal from the outside for switching the oscillation frequency range of the oscillation stage 1 is 6. Further, FIG. 7 shows a circuit example of the oscillation stage 1 in FIG.

FIG. 7 shows a variable capacitance diode 10, a coil 11, and switching elements 12 and 1 for switching the oscillation frequency range.
3 and a transistor section. Further, in FIG. 7, the control voltage of the voltage controlled oscillator is 4, the output of the oscillation stage is 5,
16 control signals from outside to switch the oscillation frequency range
Is.

The operation of the voltage-controlled oscillator having the wide range of oscillation frequency constructed as above will be described below.

In FIG. 7, when the DC control voltage 4 is input to the oscillation stage 1, the capacitance C _{B of the} variable capacitance diode 10 is increased.
The inductor L of the coil 11 and the capacitances C ₁ and C _{2 of the} capacitors 14 and 15 form a resonator, and the output 5 of the oscillation stage 1 is obtained through the transistor section. Figure 6
As a result, the oscillation stage output 5 is amplified or attenuated by the amplification stage 2 to a desired magnification, and the oscillator output 6 is passed through the buffer 3.
To get

A method of changing the oscillation frequency of the voltage controlled oscillator will be described with reference to FIG. 3 showing the capacitance characteristic of the variable capacitance diode 10 in FIG. As shown in FIG. 3, since the capacitance C _B of the variable capacitance diode depends on the control voltage V _T ,
The oscillation frequency can be changed by changing the control voltage V _T. In order to obtain a wider oscillation frequency range, as shown in FIG. 7, the coils 11 are connected in multiple stages, and the oscillation frequency range switching elements 12 and 13 are attached to divide the coils. Hereinafter, an operation example of the voltage controlled oscillator when the coils 11 are connected in three stages will be described with reference to FIG. 7.

When the oscillating frequency of the voltage controlled oscillator is in the highest range, the oscillating frequency range switching element 12 is controlled by an external control signal 16 to make the element 12 conductive, and one of the three divided coils 11 is made. To form a resonator. Similarly, when the element 12 is made non-conductive and the element 13 is made conductive by the control signal 16 from the outside, the resonator is composed of two coils 11 divided into three. Further, when the oscillation frequency of the voltage controlled oscillator is in the lowest range, the elements 12 and 13 are connected to the control signal 16 from the outside.
Then, when both are in the non-conducting state, the resonator is configured by using all the coils 11 divided into three.

As described above, the conventional voltage-controlled oscillator having a wide oscillation frequency range based on the oscillation frequency range switching signal controls the oscillation frequency range switching signal from the outside when switching the oscillation frequency range. I was going.

[0011]

However, in the conventional configuration as described above, it is necessary to control the oscillation frequency range switching signal from the outside to set the oscillation frequency range. In addition, the user must predict the oscillation frequency of the voltage controlled oscillator in advance and set the oscillation frequency range, which makes control complicated. Also,
As an example, a certain oscillation frequency range is 50 MHz to 10
When the specifications of 0 MHz and 80 MHz to 150 MHz are used, in the conventional oscillation frequency range control method, the oscillation frequency range is set by external control, so the lower and upper limits of each oscillation frequency range must be adjusted before use. Met.

The present invention solves the above-mentioned conventional problems. The switching frequency range switching signal of the voltage controlled oscillator is automatically controlled in the system without being controlled from the outside, and thus the oscillation frequency range is controlled. The purpose is to eliminate the need for the setting of, and the adjustment of the lower and upper limits of each oscillation frequency range.

[0013]

To achieve the above object, a voltage controlled oscillator according to the present invention comprises a voltage comparator for comparing a control voltage input to the voltage controlled oscillator with an arbitrary threshold voltage. By providing a control circuit for controlling the oscillation frequency range of the voltage controlled oscillator using the output of the voltage comparator as an input, the desired oscillation frequency range is set by this control circuit.

[0014]

According to the configuration of the present invention, the oscillation frequency range of the voltage controlled oscillator which has been conventionally set by the external control signal is automatically controlled in the system.
It is not necessary to set the oscillation frequency range and adjust the lower and upper limits of each oscillation frequency range, which facilitates control of the voltage-controlled oscillator.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a voltage controlled oscillator having a wide oscillation frequency range by an oscillation frequency range switching signal according to the present invention. FIG. 1 includes an oscillation stage 1, an amplification stage 2, and a buffer 3. The control voltage is 4, the output of the oscillation stage is 5, and the oscillator output is 6. The present invention is an invention of a voltage controlled oscillator which is characterized in that an external control signal for controlling a switching signal of the oscillation frequency range is unnecessary as compared with the conventional voltage controlled oscillator having a wide oscillation frequency range.

The operation of the voltage-controlled oscillator having a wide oscillation frequency range by the oscillation frequency range switching signal of the present invention constructed as above will be described below.

A circuit example of the oscillation stage 1 of FIG. 1 is shown in FIG. In FIG. 2, the oscillation stage 1 includes a variable capacitance diode 10 and
It includes a coil 11, a transistor 17 section, a voltage comparator 8 for setting an oscillation frequency range, a control circuit 9, and oscillation frequency range switching elements 12 and 13. Also,
In FIG. 2, the control voltage is 4, the oscillation stage output is 5, the voltage comparator is 8, and the threshold voltage to be compared with the control voltage 4 is 7.

In FIG. 2, when a DC control voltage 4 is input to the oscillating stage 1, the resonator operates as a variable capacitance diode 10
Of the capacitor C _B , the inductor L of the coil 11, and the capacitors C ₁ and C _{2 of the} capacitors 14 and 15,
The oscillation stage output 5 is obtained through the transistor section 17. From FIG. 1, this oscillation stage output 5 is amplified or attenuated by the amplification stage 2 to a desired magnification, and the oscillator output 6 is obtained through the buffer 3.

The method of setting the oscillation frequency range of the voltage controlled oscillator, the capacitance characteristic of the variable capacitance diode 10 in FIG. 2, as shown in FIG. 3, the capacitance C _B of the variable capacitance diode,
Because it relies on the control voltage V _T, it is possible to vary the oscillation frequency by changing the control voltage V _T.
Further, in order to obtain a wide oscillation frequency range, there is a method in which the coils 11 are connected in multiple stages and divided by the oscillation frequency range switching elements 12 and 13, respectively, as shown in FIG.

In FIG. 2, the coil 11 is connected in three stages by two oscillation frequency range switching elements, but in principle, the same characteristics can be obtained by connecting any number of stages. Further, the same characteristics are obtained not by the multi-stage connection of the coil 11 but also by the multi-stage connection of the variable capacitance diode 10. The input / output characteristics in FIG. 2 are shown in FIG.

In FIG. 4, the first stage shows when the oscillation frequency range switching element 12 is in the conducting state, and the second stage shows the element 1.
2 indicates a non-conducting state, 13 indicates a conducting state, and 3rd stage indicates a time when both elements 12 and 13 are non-conducting states.
From FIG. 4, it can be seen that a wide range of oscillation frequencies can be obtained by connecting the coils in multiple stages and providing each with an oscillation frequency range switching element. A method of switching the oscillation frequency range from the first stage to the third stage will be described below with reference to FIGS. 2 and 4.

In FIG. 4, for example, if the control voltage V _T is equal to the threshold voltage V _T1 when the current oscillation frequency range is two stages, the oscillation frequency range switching element sets the oscillation frequency range to three stages. Lower the oscillation frequency range.
When the control voltage V _T becomes equal to the threshold voltage V _T2 , the oscillation frequency range is set to the first stage and the oscillation frequency range is increased. Set the oscillation frequency range as described above,
A flow chart is shown in FIG.

In FIG. 5, the voltage comparison of the control voltage V _T is performed twice, but whichever comes first, the same result is obtained. Moreover, since the voltage comparison of the control voltage V _T is performed in an infinite loop, resetting is not necessary every time the oscillation frequency range is set. FIG. 2 shows an example of a voltage controlled oscillator using such an oscillation frequency range setting method. The control voltage 4 and the threshold voltage 7 are input to the voltage comparator 8, and the output thereof is used as the input of the control circuit 9, and the control circuit 9 controls the oscillation frequency range switching elements 12 and 13. As an example of the control circuit 9, there is a method in which the output of the voltage comparator 8 is input to the clock of the up / down counter and the lower 2 bits of the up / down counter are used as control signals for the oscillation frequency range switching elements 12 and 13.

As described above, according to this embodiment, as shown in FIG. 2, when the oscillation frequency range of the voltage controlled oscillator is set,
A wide range of oscillation frequency can be automatically controlled within the system without external control signals.

[0026]

As described above, according to the present invention, a voltage controlled oscillator having a wide oscillation frequency range and a voltage comparator for comparing the control voltage with an arbitrary threshold voltage by a switching signal of the oscillation frequency range. By providing a control circuit for controlling the oscillation frequency range of the voltage controlled oscillator with the output of the voltage comparator as an input, the oscillation frequency range can be automatically controlled in the system. .

With such a configuration of the voltage controlled oscillator, the oscillation frequency range switching signal has been conventionally externally controlled, but since it can be automatically controlled in the system, it is not necessary for the user to specify the oscillation frequency range. became. This eliminates the need for the user to predict the oscillation frequency of the voltage controlled oscillator in advance, and the adjustment of the lower limit and the upper limit of each set frequency range becomes unnecessary because the oscillation frequency range can be automatically controlled.

[Brief description of drawings]

FIG. 1 is a block diagram of a voltage controlled oscillator having a wide variable frequency range according to an embodiment of the present invention.

2 is a circuit example of an oscillation stage 1 in FIG.

FIG. 3 is a diagram showing a capacitance characteristic of a variable capacitance diode.

FIG. 4 is a diagram showing input / output characteristics of the oscillation stage in FIG.

FIG. 5 is a flowchart of a method of switching the oscillation frequency range according to the present invention.

FIG. 6 is a block diagram of a conventional voltage controlled oscillator having a wide variable frequency range.

7 is a circuit example of the oscillation stage 1 in FIG.

[Explanation of symbols]

1 oscillation stage 4 control voltage 7 threshold voltage 8 voltage comparator 9 control circuit for setting oscillation frequency range 10 variable capacitance diode 11 coil 12 oscillation frequency range switching element 13 oscillation frequency range switching element 16 oscillation frequency range switching signal External control signal to control

Claims (1)

[Claims] 1. An oscillation frequency range switching signal
A voltage-controlled oscillator whose oscillation frequency range is switched, a voltage comparator for comparing a control voltage input to the voltage-controlled oscillator with an arbitrary threshold voltage, and the voltage control using the output of the voltage comparator as input. A voltage-controlled oscillator including a control circuit that controls an oscillation frequency range switching signal of the oscillator.