JPH0242817A - Stabilized voltage controlled oscillator - Google Patents

Abstract

PURPOSE:To prevent an influence due to a leading-in phenomenon and to stabilize a frequency by providing first and second voltage controlled oscillators, and suppressing fluctuation of the oscillatiion central frequency of the first oscillator on the basis of the fluctuation part of an oscillating frequency to be obtained with a phase comparing means. CONSTITUTION:A second voltage controlled oscillator(VCO)3 is operated by a timer circuit 4 in each prescribed time. In each prescribed time, the oscillation part of the oscillation central frequency of the VCO3 is obtained by a phase comparing means 5 and this fluctuation part is defined as a direct current voltage V by an LPF6 and held by a hold circuit 8 for a prescribed time. Since the fluctuation part V can be regarded as the oscillation part of the central frequency of the VCO2, it is added through an LPF9 to the input signal of the VCO2. Thus, the oscillation centrol frequency of the VCO2 is exactly controlled samelly as the input signal and oscillation fluctuation at the time of inputting power source or converting temperature can be suppressed. Since the fluctuation part of the frequency is obtained in each prescribed time, the influence of leading-in phenomenon can be prevented between the both VCOs.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is based on PLL (Phasa Locked
Voltage Controlled Oscillator (VCO) used in loop) circuits, FM modulation, etc.
The present invention relates to a stabilized voltage controlled oscillator whose oscillation frequency can be stabilized.

[Conventional Example] In recent years, with the development of LSI technology, various types of ICs have been proposed, and, for example, voltage controlled oscillators used in PLL circuits and FM modulation have also come to be formed monolithically within semiconductor packages. Furthermore, it has been proposed that two circuits of the voltage controlled oscillator are formed on the monolith, and the two circuits of the voltage controlled oscillator can be controlled at different oscillation center frequencies.

[Problem to be Solved by the Invention] By the way, as shown in FIG. 3, the voltage controlled oscillator formed monolithically has an oscillation frequency (center frequency) that fluctuates from the time the power is turned on until a predetermined time T. There was a problem.

Furthermore, as shown in FIG. 4, there is a problem in that the oscillation center frequency of the voltage controlled oscillator fluctuates due to changes in ambient temperature.

Further, when two oscillators are close to each other and the oscillation center frequencies of these oscillators are close, a pull-in phenomenon occurs and they influence each other, making the oscillation frequencies of these oscillators unstable. This is the 2nd layer formed on the monolithic
The same is true for the two vCOs.

This invention was made in view of the above problems, and its purpose is to be able to keep the oscillation frequency stable regardless of external factors such as ambient temperature, and to prevent the effects of the pull-in phenomenon, thereby achieving higher accuracy. An object of the present invention is to provide a stabilized voltage controlled oscillator that can stabilize the frequency.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a first voltage control oscillator used for transmitting an input signal of two voltage controlled oscillators formed on one monolithic circuit. A controlled oscillator, a second voltage controlled oscillator used to control the oscillation frequency of the first voltage controlled oscillator, and a time control for controlling the operation of the second voltage controlled oscillator at predetermined time intervals. The output signal of the second voltage controlled oscillator is delayed by a predetermined time, and this delayed signal is compared with the currently output signal to determine the variation in the oscillation frequency of the second voltage controlled oscillator. a first filter that smoothes the fluctuation signal obtained as a result of the comparison to convert it into a DC voltage; and a hold unit that holds the DC voltage for a predetermined period of time determined by the timer means. , is provided between the inputs of the first and second voltage controlled oscillators, and uses the held DC voltage as a correction value for the first voltage controlled oscillator, and uses the input signal of the second voltage controlled oscillator as a correction value. and a second filter for preventing contamination, and is configured to suppress fluctuations in the oscillation center frequency in the first voltage controlled oscillator based on the fluctuation amount.

Further, according to the present invention, a differential amplifier is used in place of the second filter, and the differential amplifier adds or subtracts the input signal and the DC voltage held by the holding means, This result is amplified to a predetermined value and input to the first voltage controlled oscillator.

[Function] With the above configuration, the second voltage controlled oscillator (VCO)
is activated at predetermined time intervals by timer means. At each predetermined time period, the phase comparator obtains the oscillation fluctuation of the oscillation center frequency of the second VCO.

This variation is made into a DC voltage by the first filter, and is held for a predetermined time by the holding means. The variation is
Since it can be regarded as an oscillation fluctuation in the center frequency of the first voltage controlled oscillator (VCO), it is added to the input signal of the first VCO via the second filter. Thereby, the oscillation center frequency of the first VCO is accurately controlled according to the input signal, and oscillation fluctuations due to power-on or temperature conversion can be suppressed. Furthermore, since the frequency fluctuation is obtained at predetermined intervals, it is possible to prevent the influence of the pull-in phenomenon between the first VCO and the second VCO.

[Example] Hereinafter, an embodiment of the present invention will be described based on FIG.

In the figure, a first vCO (Volta
ge Controlled 0scillator)
2 and a second vCO3 are formed. 1st vC
O2 is for outputting a signal with an oscillation frequency corresponding to the input signal, that is, for transmitting the input signal. On the other hand, the second v
The CO3 is operated at every set time by the timer circuit 4, and the output signal at the time of its operation is input to the phase comparison means 5. The phase comparison means 5 includes a delay circuit 5a that delays the output signal by, for example, approximately 1/4 of the oscillation period of the second vCO3, and a delay circuit 5a that delays the output signal by approximately 1/4 of the oscillation period of the second vCO3, and a delay circuit 5a that delays the output signal by approximately 1/4 of the oscillation period of the second vCO3, and combines this delayed signal with the signal currently output from the second vCO3. A 2Ex-OR circuit 5b that outputs a rectangular wave signal according to the phase difference of is provided. Note that other logic circuits such as a 2-AND circuit may be used as the phase comparison means 5. In this way, from the phase comparison means 4, LL Hlj
, 11 L Rectangular wave signals with different periods of 1 level are output.

This rectangular wave signal is integrated and smoothed by a first LPF (low-pass filter) 6 and converted into a DC voltage. This DC voltage changes in response to fluctuations in the oscillation frequency when the power is turned on and in response to changes in ambient temperature, and is obtained intermittently at each time of the timer circuit 4. In this way, the DC voltage (frequency fluctuation) obtained intermittently is transferred to the amplifier 7.
The signal is amplified to a predetermined level and held by the hold circuit 8. The DC voltage held in the hold circuit 8 is
is fed back to the input of the second vCO3, and the second LP
It is added to the input signal of the first vCO2 via F (low pass filter) 9. Note that the second LPF 9 functions to prevent the input signal from being mixed into the input of the second vCO3.

Next, the operation of the stabilized voltage oscillator having the above configuration will be explained.

First, it is assumed that the first and second vCOs 2 and 3 are set to oscillate at the same center frequency. Here, when the power is turned on to the semiconductor element in which the first and second vCO2 and 3 are formed, a signal of a predetermined oscillation frequency is intermittently outputted from the output of the second vCO3 by the timer circuit 4. be done. At this time, as shown in Figure 2,
If the center of the oscillation frequency obtained intermittently fluctuates, the phase comparison means 5 outputs a rectangular wave signal corresponding to the fluctuation, and this rectangular wave signal is transmitted to the first LPF 6.
The voltage is integrated and smoothed to obtain a DC voltage ΔV. This straight A! The pressure Δ■ is brought to a predetermined level by the amplifier 7 and held by the hold circuit 8. The hold circuit 8 stores the second vCO3 every time the second vCO3 operates intermittently.
A DC voltage corresponding to the variation in the oscillation center frequency at O3 is held. This held DC voltage is the second vC
It is used as a correction value for the oscillation frequency of O3, and the first vC
It is used as a correction value for the oscillation frequency of O2. That is, since the oscillation condition of the center frequency of the first vCO2 is the same as that of the second vCO3, it can be said that the correction value corresponds to the fluctuation of the center frequency of the first vCO2.

Further, in the above description, the case when the power is turned on is explained as an example, but even if the oscillation of the center frequency fluctuates due to a change in the ambient temperature or the passage of time, the correction value can be obtained in exactly the same way.

In this way, the fluctuation of the center frequency becomes the second vCO3
A value for correcting the variation is obtained by the phase comparator 5 and the first LPF 6. When there is an input signal to the first vCO2, the first vCO2 oscillates at a center frequency according to the input signal, but the input signal is supplied with a correction value (DC voltage) via the second LPF 7. , the first vCO2 outputs a signal with an oscillation center frequency corresponding to the correction value and the input signal. Moreover, the correction value changes depending on various external factors and changes to a value that keeps the oscillation center frequency of the first vCO2 constant, so that the oscillation of the first vCO2 is made stable. Furthermore, a second vc for obtaining the correction value
Since oa is operated intermittently by the timer circuit 4,
It is possible to prevent the occurrence of the entrainment phenomenon due to mutual influence between the first vCO2 and the first vCO2.

FIG. 2 is a schematic circuit block diagram of a stabilized voltage controlled oscillator showing a modified embodiment of the present invention. In addition, in the figure, the first
Components that are the same as those in the figures are given the same reference numerals and repeated explanations will be omitted.

In this example, a differential amplifier 10 is used in place of the second filter 9. The differential amplifier 10 is an inverting amplifier. An input signal is input to the non-inverting input terminal of this inverting amplifier, a DC voltage of a predetermined level obtained by the amplifier 7 is input to the non-inverting input terminal, and the output terminal is input to the differential amplifier 10. The output of is the first
It is assumed that the voltage controlled oscillator 2 is operated manually. Note that a DC voltage of a predetermined level obtained by the amplifier 7 is input to the second voltage controlled oscillator 3.

Therefore, in the differential amplifier 10, the DC voltage ΔV corresponding to the variation obtained by the phase comparator 5 is added to or subtracted from the input signal.

Then, since the input signal is corrected by the amount of variation and input to the first voltage controlled oscillator 2, the variation in the oscillation center frequency of the first voltage controlled oscillator 2 is suppressed as in the previous embodiment.

Note that in the above two embodiments, the first and second voltage controlled oscillators 2 and 3 are formed on one monolith, but they may be separate. In other words, even if the first and second voltage controlled oscillators 2.3 are configured to be separated by several orders of magnitude, the surrounding environments can be considered to be the same.

[Effects of the Invention] As explained above, according to the stabilized voltage controlled oscillator of the present invention, one first vCO is used for signal transmission, and the other second vCO is used for control (oscillation stabilization). The control VCO is operated intermittently, the control VCO obtains the oscillation fluctuation of the center frequency, and the fluctuation is used to correct the oscillation of the center frequency of the signal transmission Co. 5. The oscillation frequency is more stable, and fluctuations in the oscillation center frequency due to power-on or changes in ambient temperature can be suppressed, and the control VCO does not have to be in constant operation, making it possible to They can be prevented from influencing each other, and the oscillation center frequency of the signal transmission VCO can be kept stable with high precision.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit block diagram of a stabilized voltage controlled oscillator showing one embodiment of the present invention, FIG. 2 is a schematic circuit block diagram of a stabilized voltage controlled oscillator showing a modified embodiment of the present invention, FIGS. 3 and 4 are graphs for explaining fluctuations in oscillation frequency by a conventional voltage controlled oscillator. In the figure, 1 is a semiconductor package, 2 is a first vCO (voltage controlled oscillator), 3 is a second vCO 14 is a timer circuit, 5
5a is a delay circuit, 5b is a 2Ex-OR
circuit, 6 is the first LPFC low-pass filter), 7 is the amplifier, 8 is the hold circuit, 9 is the second LPF (filter),
10 is a differential amplifier. Kenwaki 100 sea breambu

Claims (3)

[Claims] (1) Of the two circuits of voltage controlled oscillators, a first voltage controlled oscillator used to transmit an input signal, and a second voltage controlled oscillator used to control the oscillation frequency of this first voltage controlled oscillator; In order to control the operation of the second voltage controlled oscillator at predetermined time intervals, a timer means for controlling the time; and a timer means for delaying the output signal of the second voltage controlled oscillator by a predetermined time;
a phase comparison means for comparing the delayed signal with the currently output signal to obtain a variation in the oscillation frequency in the second voltage controlled oscillator; and a phase comparison means for smoothing the variation signal obtained as a result of this comparison. a first filter that converts the DC voltage into a DC voltage; a hold unit that holds the DC voltage for a predetermined period of time determined by the timer unit; a second filter that uses the DC voltage as a correction value for the first voltage controlled oscillator and prevents the input signal from being mixed into the second voltage controlled oscillator, A stabilized voltage controlled oscillator characterized in that fluctuations in the oscillation center frequency of the voltage controlled oscillator are suppressed. (2) A differential amplifier is used in place of the second filter, and this differential amplifier adds or subtracts the input signal and the DC voltage held by the holding means, and converts this result into a predetermined value. The stabilized voltage controlled oscillator according to claim 1, wherein the oscillator is amplified and input to the first voltage controlled oscillator. (3) The stabilized voltage controlled oscillator according to claim (1) or claim (2), wherein the first and second voltage controlled oscillators are formed on one monolith.