JPH04312018A - High-precision variable frequency oscillator, high-accuracy oscillator, and synchronous oscillator - Google Patents

Abstract

PURPOSE:To obtain the high-precision variable the frequency oscillator which is simple in its configuration and is capable of executing highly precise frequency control. CONSTITUTION:Bias voltage V generated by a variable voltage source 13 is controlled by an external control signal, and the bias voltage V and a frequency discrimination signal are summed by an addition circuit 14. At that time, the change portion (relative value) of the output frequency of an atomic oscillator becomes (KvRb0<-1> V. Here, K is frequency discrimination sensitivity. Accordingly, the change of the output frequency to the bias voltage V becomes linear.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a high-precision variable frequency oscillator, a high-precision oscillator, and a high-precision variable oscillator that can vary the frequency, improve accuracy, and synchronize a highly stable oscillator such as an atomic oscillator.
and regarding synchronous oscillators.

0002

[Background Art] As atomic oscillators have become smaller and cheaper in recent years, the frequency or phase of small atomic oscillators (mainly rubidium atomic oscillators) has been changed to other frequency standards (mainly rubidium atomic oscillators) that have better accuracy and long-term stability. Synchronization with cesium atomic oscillators and standard radio waves is used in the fields of digital communications and TV broadcasting. By the way, an atomic oscillator is an oscillator that generates highly stable and accurate frequencies by utilizing transitions between energy levels of atoms, molecules, ions, etc. Therefore, it is generally not easy to change the frequency, but two methods described below are currently in practical use.

The first method is a method using the Zeeman effect. The configuration of an apparatus using this method is shown in FIG. In the figure, the output (frequency; v0) of a voltage controlled crystal oscillator (VCXO) 1 is connected to a synthesizer 2 (frequency synthesis; N1
/N2), the frequency becomes v0·(N1/N2) and is supplied to one input terminal of the mixer 4. Further, the output signal of the voltage controlled crystal oscillator 1 is modulated by the frequency modulator 6 and then supplied to the other input end of the mixer 4 via the frequency multiplier 3 (multiplying ratio: M1). The frequency modulator 6 receives the output signal (frequency; f
) is supplied. Then, the output signal of the voltage controlled crystal oscillator 1 is converted into a microwave (frequency: v
μ1=(M1+N1/N2)v0). This microwave is input to the rubidium resonator 7 and interacts with rubidium atoms (resonance frequency: vRb). A DC magnetic field H is applied to the rubidium resonator 7 by a magnetic field generating coil 8 . Then, by detecting the output of the rubidium resonator 7 with a phase sensitive detector (PSD) 9, a frequency discrimination signal proportional to vμ1-vRb is obtained. Next, the fluctuation component of the frequency discrimination signal is removed by the integrating circuit 10 and fed back to the voltage controlled crystal oscillator 1, so that the output frequency of this atomic oscillator is v0=(M1+N
1/N2)-1vRb. According to the above configuration, between the resonance frequency vR and the applied magnetic field H, vRb=v
There is a relationship of Rb0+αH2. Here, vRb0 is the resonance frequency in the absence of a magnetic field, and α is a constant. Therefore, by controlling the current supplied by the variable current source 11 to the magnetic field generating coil 8 using an external control signal, the output frequency of the atomic oscillator can be changed.

The second method is to change the synthesis ratio of the synthesizer. The configuration of an apparatus to which this method is applied is shown in FIG. The basic operation of the device shown in this figure as an atomic oscillator is the same as that shown in FIG. However, in the device shown in this figure, a table written in the ROM 12 is read by an external control signal, and the frequency division ratios N1 and N2 in the synthesizer 2 are changed according to this table, thereby controlling the frequency.

[0005]

[Problems to be Solved by the Invention] By the way, although the device according to the first method described above has a simple configuration,
Since the frequency changes in proportion to the square of the magnetic field (current),
It was difficult to obtain linearity over a wide range, and there were drawbacks in terms of frequency control accuracy. Further, in the device according to the second method, the frequency can be changed with high precision, but in order to do so, it is necessary to use a variable frequency divider with a large number of digits as the frequency divider in the synthesizer 2. A problem arises in that the phase comparator and loop filter also become complicated. The present invention was made in view of the above-mentioned circumstances, and
The purpose of this invention is to realize a high-precision variable frequency oscillator that has a simple configuration and can perform frequency control with high precision. In addition, the purpose of this high-precision variable frequency oscillator is to make it a high-precision oscillator using a more accurate and highly stable oscillator as a master oscillator, and furthermore, a synchronous oscillator in which the high-precision variable frequency oscillator is synchronized with an external input signal is provided. The purpose is to provide.

[0006]

Means for Solving the Problems In order to solve the above problems, the invention according to claim 1 provides a variable frequency oscillator that oscillates at a frequency depending on the level of a supplied signal; a reference oscillation device that is supplied with a signal of a frequency corresponding to the output frequency and outputs a signal containing a difference component between this signal and a reference signal; and a signal of a level corresponding to the difference component is supplied to the variable frequency oscillator; Accordingly, in an oscillator having a frequency control means for controlling the oscillation frequency of the variable frequency oscillator so that the difference component becomes small, a bias value corresponding to an external control signal is superimposed on the output signal of the frequency control means. Alternatively, it is characterized in that it has a plurality of bias value applying means, and by changing the bias value of the bias value applying means, the oscillation frequency is changed.

[0007] Furthermore, in the invention according to claim 2,
A high precision variable frequency oscillator according to claim 1; and claim 1.
a second reference oscillation device that is supplied with a signal having a frequency corresponding to the output frequency of the high precision variable frequency oscillator described in , and outputs a second difference component corresponding to the difference between this signal and the second reference signal; , and a second frequency control means having a longer time constant than the frequency control means according to claim 1 and outputting a signal at a level corresponding to the second difference component, and the second frequency control means according to claim 1 It is characterized in that the output signal of the second frequency control means is supplied to the bias value applying means in place of the external control signal.

Furthermore, in the invention according to claim 3, the frequency difference between the high precision variable frequency oscillator according to claim 1 and the output of the high precision variable frequency oscillator according to claim 1 and an external input signal or Comparing means for detecting and outputting a phase difference; and a signal having a time constant longer than the time constant of the frequency control means according to claim 1, and having a level corresponding to the frequency difference or phase difference detected by the comparing means. and third frequency control means for outputting the external control signal, and the bias value applying means according to claim 1 receives the third
It is characterized in that it supplies an output signal of the frequency control means.

[0009]

[Operation] The present invention realizes a frequency change by changing the bias value superimposed by the bias value applying means. In this case, since the bias value and the amount of frequency change are proportional, high accuracy can be obtained. Furthermore, the superposition of bias values can be realized by an addition circuit using an operational amplifier or the like in an analog control system, and by a simple addition algorithm in software in a digital control system, so the configuration is simple.

0010

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. (1) First Embodiment FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention. In this figure, the same reference numerals are given to the parts corresponding to the parts shown in FIG. 5 described above, and the explanation thereof will be omitted. In this embodiment, an adder circuit 14 is provided to add the output signal of the variable voltage source 13 and the output signal of the phase sensitive detector 9, and the output signal of the adder 14 is supplied to the integrator 10. ing. Further, the output bias voltage of the variable voltage source 13 is controlled by an external control signal.

The basic operation of this embodiment with the above-described configuration is the same as that of the conventional device shown in FIG. However, in this embodiment, the bias voltage ΔV generated by the variable voltage source 13 is controlled by an external control signal, and the bias voltage ΔV and the frequency discrimination signal are added together by the adder circuit 14. At this time, the change in the output frequency of the atomic oscillator (relative value)
is (KvRb)-1ΔV. Here, K is frequency discrimination sensitivity. Therefore, in this example:
The output frequency changes linearly with respect to the bias voltage ΔV.

(2) Second Embodiment FIG. 2 is a block diagram showing the configuration of a second embodiment of the present invention. The difference between this embodiment and the first embodiment is that an adder 14 and a variable voltage source 13 are provided on the output side of the integrating circuit 10. The basic operation of the atomic oscillator in this embodiment is the same as that in the first embodiment shown in FIG. 1, but the change (relative value) in the output frequency of the atomic oscillator is [
{1+G(0)}KvRb]-1ΔV. here,
G(0) is the DC value of the open loop transfer function. Therefore, also in this embodiment, the change in the output frequency with respect to the bias voltage ΔV is linear. As can be seen from the above, in order to obtain the effects of the first and second embodiments, the integration circuit 1
It is sufficient to superimpose the bias component on the zero output signal, and the superimposition position does not matter before or after the integrating circuit 10.

(3) Third Embodiment FIG. 3 is a block diagram showing the configuration of a third embodiment of the present invention. In the figure, the configuration of elements 1 to 14 is the same as that of the first embodiment shown in FIG. 1, and constitutes a variable frequency rubidium atomic oscillator A. In FIG. 3, the output (frequency; v0=(M1+N
1/N2)-1[vRb+{{1+G(0)}-1ΔV
]) is the synthesizer 15 (frequency synthesis ratio; L1/L2
), the frequency is vμ2=(M2+L1/L2)
v0 and is supplied to one input terminal of the mixer 17. Further, the output signal of the variable frequency rubidium atomic oscillator A is modulated by the frequency modulator 19 and then supplied to the other input end of the mixer 17 via the frequency multiplier 16 (multiplying ratio: M2). The frequency modulator 19 is supplied with the output signal (frequency: f') of the modulation signal generator 18 . Then, the output signal of the variable frequency rubidium atomic oscillator A is converted into a microwave by the mixer 17. This microwave is input to the cesium beam tube 20 and interacts with cesium atoms (resonance frequency: vCs). Then, by detecting the output of the cesium beam tube 20 with the phase sensitive detector 21, a frequency discrimination signal proportional to vμ2-vCs is obtained. By removing the fluctuation component of the frequency discrimination signal in the integrating circuit 22 and feeding it back to the variable voltage source 13, the output frequency of the rubidium atomic oscillator A becomes v0=(M2+L1/
L2)-1vCs. By making the time constant of the integrating circuit 22 sufficiently longer than the time constant of the integrating circuit 10, this embodiment can have both the short-term frequency stability of a rubidium atomic oscillator and the frequency accuracy and long-term stability of a cesium atomic oscillator.

(4) Fourth Embodiment FIG. 4 is a block diagram showing the configuration of a fourth embodiment of the present invention. The operation of the variable frequency rubidium atomic oscillator A composed of elements 1 to 14 is the same as that in the first embodiment. In the device shown in this figure, the output of the variable frequency rubidium atomic oscillator A (frequency; v0 = (M1 + N1/N2)
By comparing -1[vRb+{(1+G)K}-1ΔV]) with the external input signal using the phase comparator 23, a phase difference signal proportional to the phase difference between the two is obtained. Then, by removing the fluctuation component of the phase difference signal in the integrating circuit 22 and feeding it back to the variable voltage source 13, the output frequency and phase of the rubidium atomic oscillator A are synchronized with the output frequency and phase of the external input signal. In this embodiment, when an external input signal is input, it can follow it with high precision, and when no external input signal is input, it can run with high stability.

(5) Modification In each of the above-mentioned embodiments, the case of a rubidium atomic oscillator was explained, but the present invention is applicable to other passive atomic oscillators (cesium atomic oscillator, passive hydrogen maser oscillator, ion ion oscillator, etc.). Trap oscillators, etc.), superconducting cavity stabilized oscillators (SCSOs), passive crystal stabilized oscillators (PDCS), and the like.

[0016]

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide a high-precision variable frequency oscillator that has a simple configuration and can perform frequency control with high precision.
This high-precision variable frequency oscillator can be made into a high-precision oscillator using a more accurate and highly stable oscillator as a master oscillator. Furthermore, the high precision variable frequency oscillator can be a synchronous oscillator synchronized with an external input signal. Therefore, it can be used in digital communication networks, TV broadcasting, and various radio wave systems.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a second embodiment of the invention.

FIG. 3 is a block diagram showing the configuration of a third embodiment of the invention.

FIG. 4 is a block diagram showing the configuration of a fourth embodiment of the invention.

FIG. 5 is a block diagram showing the configuration of a conventional variable frequency rubidium atomic oscillator using the Zeeman effect.

FIG. 6 is a block diagram showing the configuration of a conventional variable frequency rubidium atomic oscillator in which the synthesis ratio of the synthesizer is changed.

[Explanation of symbols]

1 Voltage controlled crystal oscillator (variable frequency oscillator) 7
Rubidium resonator (reference oscillator) 9 Phase sensitive detector (frequency control means) 10 Integrating circuit (frequency control means) 13 Variable voltage source (bias value provision means) 14 Addition circuit (bias value provision means) 20 Cesium beam tube ( Second reference oscillator) 21 Phase sensitive detector (second frequency control means) 22 Integrating circuit (second and third frequency control means) 23 Phase comparator (comparison means)

Claims (3)

[Claims] 1. A variable frequency oscillator that oscillates at a frequency corresponding to the level of a supplied signal, and a signal having a frequency corresponding to the output frequency of the variable frequency oscillator are supplied, and a difference component between this signal and a reference signal is a reference oscillator that outputs a signal containing the difference component; and a frequency that controls the oscillation frequency of the variable frequency oscillator so that the difference component is reduced by supplying a signal at a level corresponding to the difference component to the variable frequency oscillator. The oscillator has one or more bias value applying means for superimposing a bias value corresponding to an external control signal on the output signal of the frequency control means, and changing the bias value of the bias value applying means. A high-precision variable frequency oscillator characterized by changing the oscillation frequency by changing the oscillation frequency. 2. The high precision variable frequency oscillator according to claim 1 and a signal having a frequency corresponding to the output frequency of the high precision variable frequency oscillator according to claim 1 are supplied, and this signal and a second reference signal are supplied. and a second reference oscillation device that outputs a second difference component corresponding to the difference between and a second frequency control means for outputting a signal, and the bias value applying means according to claim 1 is supplied with an output signal of the second frequency control means in place of the external control signal. High accuracy oscillator. 3. The high precision variable frequency oscillator according to claim 1, and a comparison means for detecting and outputting a frequency difference or a phase difference between the output of the high precision variable frequency oscillator according to claim 1 and an external input signal. and third frequency control means having a time constant longer than the time constant of the frequency control means according to claim 1 and outputting a signal at a level corresponding to the frequency difference or phase difference detected by the comparison means. A synchronous oscillator comprising: a synchronous oscillator which supplies an output signal of the third frequency control means to the bias value applying means according to claim 1 in place of the external control signal.