JPH10282273A - Reference frequency generation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate a more accurate and stable reference frequency by allowing an estimation operation part being installed at an operation means for frequency control to receive the detection signal of a temperature in a device and correcting a frequency fluctuation due to a temperature fluctuation quickly. SOLUTION: An ambient temperature detection means 60 detects a temperature in a device and sends the temperature signal to an operation means 13 for controlling frequency. An estimation operation part 22 being installed at the operation means 13 for controlling frequency receives temperature data Tdnew from the ambient temperature detection means 60 and inputs temperature data Tdold that was subjected to temperature correction and was executed last time and then obtains the temperature difference between the both. When the temperature difference exceeds a specific temperature difference Tddiff , a condition is shifted from a normal control state to a temperature correction control state. Then, a relatively fast frequency control is performed to a degree for following a temperature change. Therefore, a frequency can be corrected even for a short frequency fluctuation accompanying a temperature fluctuation in a device, thus generating a further accurate and stable reference frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference frequency generator for receiving a radio wave from an artificial satellite having a built-in atomic frequency standard or an ultra-high-precision time signal similar thereto and generating a high-precision reference frequency. About.

[0002]

2. Description of the Related Art FIG. 7 shows a configuration diagram of a reference frequency generating apparatus for a prior art example. As a conventional known technology of a reference frequency generating device that receives a radio wave from an artificial satellite and generates a high-precision reference frequency, Japanese Patent Application Laid-Open No. 06-314192 is known.
There is a "reference frequency generator" in Japanese Patent Publication No.

[0003] As shown in FIG. 7, the configuration of this reference frequency generating device includes a satellite radio receiver 11 and a time interval measuring unit 1.
2, a frequency control operation unit 13, and a D / A converter 14
, A frequency divider 15, a frequency converter A17, a voltage-controlled oscillator 10, and a temperature sensor 29. According to the above-described configuration, the frequency control algorithm is performed by a digital filter having a long time constant by the estimation calculation unit in the frequency control calculation unit 13. In this control algorithm, there is a problem that the following control is not performed with respect to a relatively short-time frequency fluctuation of the voltage controlled oscillator 10 itself. Due to this short-term frequency fluctuation factor, it has not been possible to realize and improve a more accurate and stable frequency generator. The ambient temperature compensating means including the temperature sensor 29, the buffer memory in the frequency controlling computing means 13, the temperature fluctuation compensating computing section, and the adder B obtains the temperature characteristics of the individual voltage controlled oscillators 10 in advance. The temperature is corrected based on the temperature. However, this temperature correction method has a drawback in that it is necessary to obtain the temperature characteristics of each voltage-controlled oscillator 10 in advance, and further, the temperature correction is performed under the condition that the voltage-controlled oscillator 10 itself does not fluctuate with time. The temperature correction may not always be optimal.

[0004] By the way, satellite radio waves orbit around the earth orbit. For this reason, frequency synchronization is performed while sequentially switching to a satellite that can be captured. However, in rare cases, reception may not be possible depending on the installation location of the antenna. When the satellite radio wave cannot be received, the frequency output is performed while maintaining the current output frequency of the built-in voltage controlled oscillator 10. When the receiving state recovers, the satellite time signal S1pps is restored again.
The time interval between the internal clock signal V1pps and the internal time signal V1pps is measured by the time interval measuring unit 12, and the phase synchronization operation is restarted.

A typical cause of the above-mentioned relatively short-time frequency fluctuation is a fluctuation in the temperature around the voltage-controlled oscillator 10. The voltage-controlled oscillator 10 is a crystal oscillator whose temperature is stabilized by being put in a constant temperature bath. However, a voltage-controlled oscillator that requires ultra-high stability of about 1E-11 is affected by a slight change in environmental temperature. . Here, E means an exponential expression. Examples of the ambient temperature fluctuation include a heat generation effect from an adjacent device, a hot / cold air from a air conditioner, a heating device, and an radiant heat of direct sunlight. As a means for improving this, there are a method of using a voltage controlled oscillator 10 having a double-structured thermostat and an improvement method of using a thermostat for the entire device. However, the installation space is large and the device becomes large and heavy, and large consumption is required. There are drawbacks that require power and drawbacks that are expensive, and are not practically preferable as a device that requires portability.

On the other hand, if the time constant (for example, time constant = 3 hours) of a long digital filter is reduced by a conventional frequency control algorithm so as to correspond to a relatively short-time frequency fluctuation, the artificial satellite needs to be changed. Radio wave propagation noise superimposed on radio waves and disturbance caused by intentionally changing an ultra-high-precision time signal cannot be removed, and on the contrary, output frequency becomes unstable, which is not preferable.

[0007]

SUMMARY OF THE INVENTION Therefore, the problem to be solved by the present invention is to correct the frequency of a relatively short-time frequency fluctuation caused by a temperature fluctuation in the apparatus by following the frequency fluctuation, thereby achieving a higher frequency. An object of the present invention is to realize an accurate and stable reference frequency generator.

[0008]

FIGS. 1 and 3 show a solution according to the present invention. First, in order to solve the above-mentioned problem, in the configuration of the present invention, an ambient temperature detecting means 60 for detecting the temperature inside the apparatus and supplying the detected temperature to the frequency control calculating means 13 is provided. A temperature fluctuation correcting means for correcting a frequency fluctuation caused by a temperature fluctuation in a short time in response to a signal is added to the frequency control calculating means 13 as a constituent means. Accordingly, it has a voltage-controlled oscillator 10 whose oscillation frequency is controlled by an applied DC voltage, and has a receiver 11 which receives a high-precision reference frequency signal from the outside and demodulates it into an input time signal. A time interval measuring unit for measuring a time interval between the internal time signal V1pps obtained by dividing the output frequency of the control oscillator by the frequency divider and an input time signal; and voltage control based on the measured value of the time interval measuring unit. A frequency control operation means for synchronizing the oscillation frequency of the oscillator;
In the reference frequency generator that controls the voltage control input terminal of the voltage controlled oscillator 10, the frequency is corrected in accordance with the relatively short-time frequency fluctuation due to the temperature fluctuation in the apparatus, thereby achieving higher accuracy. And realizes a stable reference frequency generator.

FIG. 1 and FIG. 3 show a solution according to the present invention. Secondly, in order to solve the above problem, in the configuration of the present invention, an ambient temperature detecting means 60 for detecting the temperature inside the apparatus and supplying the detected temperature to the calculating means 13 for frequency control is provided. A temperature fluctuation correcting means for correcting a frequency fluctuation caused by a temperature fluctuation in a short time in response to a signal is added to the frequency control calculating means 13 as a constituent means. Thus, a satellite radio receiver 11 having a voltage-controlled oscillator 10 whose oscillation frequency is controlled by an applied DC voltage, receiving a radio wave of an artificial satellite having a built-in atomic frequency standard, and demodulating an input time signal is provided. A time interval measuring unit 12 for measuring a time interval between the internal time signal V1pps obtained by dividing the output frequency of the voltage controlled oscillator 10 by the frequency divider 15 and the satellite time signal S1pps;
From the measured value of the frequency control oscillator 10 for calculating a digital control value for synchronizing the oscillation frequency of the voltage controlled oscillator 10 with the frequency of the atomic frequency standard device of the artificial satellite. In a reference frequency generator having a D / A converter 14 for receiving a digital control value and converting it into a DC voltage to be supplied to a voltage control input terminal of a voltage controlled oscillator 10, a relatively short time The frequency is corrected in accordance with the fluctuation, thereby realizing a more accurate and stable reference frequency generator.

As shown in FIG. 4, a frequency converter A17 for converting the output frequency of the voltage controlled oscillator 10 into a predetermined frequency (for example, a synthesizer or a DDS (Direct Digital
Synthesizer) is provided, and in this case, a high-precision reference frequency generator capable of outputting an arbitrary output frequency fout can be realized.

As shown in FIG. 5, instead of the above-mentioned satellite radio receiver 11, a standard radio receiver 11b for receiving a national standard radio wave, and a reference time signal demodulated upon receiving this radio signal. There is a configuration means of the reference frequency generating device to be described. As shown in FIG. 6, instead of the above-described satellite radio receiver 11, a reference frequency signal generator which receives a reference frequency signal distributed through a communication network or a broadcast network and converts it into a reference time signal is used. There is a configuration means of the device.

As the temperature fluctuation correcting means for correcting the frequency fluctuation caused by the temperature fluctuation in a short time, the number N of data of the digital filter having a long time constant by the estimating operation unit 22 of the frequency control operation means 13 is used. There is means for reducing the frequency and correcting the short-term temperature fluctuation by increasing the proportional constant P and the integral constant I. The setting conditions for the number of data N, the proportionality constant P, and the integration constant I, which are the respective elements of the digital filter, are within the range that does not hinder the influence of the disturbance of the satellite time signal S1pps. May be used. As a result, a temperature correction that can follow a relatively short-time frequency fluctuation due to a temperature fluctuation in the apparatus is realized.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings together with embodiments.

FIG. 1 is a block diagram of the reference frequency generator of FIG. 1, FIG. 2 is a diagram showing control conditions of seven stages and setting conditions of each mode, and FIG. 3 is an example of convergence time characteristics to a target phase point. Will be described. Elements corresponding to the conventional configuration are denoted by the same reference numerals.

As shown in FIG. 1, the configuration of the present invention comprises a satellite radio receiver 11, a time interval measuring unit 12, a frequency control arithmetic unit 13, a D / A converter 14, and a frequency divider 15
, A voltage-controlled oscillator 10, a temperature sensor 29, and an ambient temperature detecting means 60. In this configuration, the ambient temperature detecting means 60 and the estimation calculating section 22 in the frequency controlling calculating means 13
Except for the above, the rest is the same as the conventional configuration.

Here, a conventional frequency control algorithm will be briefly described. Immediately after the power is turned on or when the radio wave of the artificial satellite cannot be received for a long time, 7 in FIG.
As shown in Mode 1 of the control mode of the stages, in order to perform the frequency pull-in operation in a short time, the number N of data to be averaged used in the estimation calculation is set to the minimum of N = 4 to shorten the loop response time. Eventually, as shown in the range value of the change amount DFf of the time interval measurement data in FIG. 2, when the change amount DFf becomes smaller, the conditions are sequentially switched to the corresponding condition settings of mode 1 to mode 7, and the frequency pull-in gradually becomes longer. Moving in the time direction, an ultra-stable output frequency fout which is not affected by disturbance is generated. If the radio wave of the artificial satellite cannot be received for a moment or temporarily, the output frequency fout immediately before is held, and after the return, the frequency is changed in the modes 1 to 7 corresponding to the change amount DFf of the time interval measurement data. By controlling, even if there is no reference frequency signal instantaneously or temporarily, a highly stable reference frequency can be continuously generated without any trouble.

Next, control relating to temperature correction according to the present invention will be described. In the present invention, control means for additionally correcting the frequency by making it possible to follow the temperature fluctuation even in a relatively short time due to the temperature fluctuation in the apparatus is provided.

The ambient temperature detecting means 60 shown in FIG. 1 has a temperature detecting element disposed near the voltage controlled oscillator 10 to detect the temperature around the voltage controlled oscillator, converts the temperature into digital code data, It is supplied to the estimation operation section 22 of the control operation means 13.

The estimating operation section 22 in the frequency control operation means 13 receives the temperature data T from the ambient temperature detection means 60.
Receiving Dnew and receiving the previously executed temperature data TDold which was previously subjected to temperature correction, calculates the temperature difference between the two, and when this temperature difference exceeds a predetermined temperature difference TDdiff, changes the temperature from the normal control state to the temperature correction control state. Move to. Here, the set value of the predetermined temperature difference TDdiff can be arbitrarily set in 0.1 ° C. steps from 0.1 ° C. to 10.0 ° C., for example.
Operate at 0 ° C set value. First, the current temperature data TDnew
Is updated and stored in the table of the previous execution temperature data TDold, and stored for the next comparison. Here, it is assumed that the current control mode is operating in mode 7, which is the longest time constant shown in FIG. The time constant of this mode 7 is a long time constant of several hours, for example.

The frequency control algorithm added in the present invention is a technique for forcibly shifting the control modes 1 to 7 shown in FIG. 2 to a mode position corresponding to a predetermined temperature difference TDdiff. For example, assuming that the current time is Mode 7, the mode is forcibly shifted to Mode 5, and various proportional constants P of Mode 5 are set.
Using the integration constant I and the number N of data, relatively fast frequency correction control is performed so as to follow a temperature change. Then, according to the magnitude of the temperature gradient ΔT, as shown in FIG. 3, the control mode is switched stepwise to M5, M6, M7. FIG. 3 shows that the mode is switched from the mode 5 (M5) to the mode 6 (M6), and the convergence state is reached in a relatively short time T1end while moving up and down the target phase point 0 in the mode 6.
Eventually, by returning to the normal control state, the control state is shifted to the control state with a long time constant in mode 7. As shown in the convergence characteristic diagram of FIG. 3, according to the present invention, since the deviation from the target phase point 0 converges in a relatively short time, the temperature follows the relatively short-time frequency fluctuation accompanying the temperature fluctuation in the apparatus. As a result,
The advantage that the generation of the output frequency fout with higher accuracy is realized is obtained.

On the other hand, as an example of detecting the return to the normal control state, the temperature data TDne
w is obtained at regular time intervals, and it is checked whether the temperature fluctuation with the immediately preceding temperature data TDnew is less than a predetermined temperature gradient ΔT. Eventually, when a temperature gradient less than the predetermined temperature gradient ΔT is detected, the predetermined waiting time T
After the elapse of the wait, the control returns from the temperature correction control state to the normal control state and ends. Note that the predetermined waiting time Twait for returning to the normal control state may not be longer than desired.

In addition to the method of switching the control mode to the short time constant as described above and correcting the temperature, there is also the following method. That is, the number N of the number N of data to be averaged is determined by a predetermined divisor Dx.
There is a method using an integer value of N / Dx divided by the following. For example, when the predetermined divisor Dx = 20, the N value in mode 7 = 2
Since it is 56, 256/20 = 12 values are used as the number N of data to be averaged. Thereafter, the return to the normal control state is the same as described above. As a result, the loop response time is shortened corresponding to the predetermined divisor Dx, and it becomes possible to follow a relatively short-time frequency fluctuation caused by a temperature fluctuation in the apparatus. In addition to the above-described temperature correction method, there is a method of shifting the value of the proportional constant P and the value of the integration constant I shown in FIG. 2 to predetermined condition values. As a result, the loop gain is increased, the loop response time is shortened, and a relatively short-time frequency change due to a temperature change is also corrected. Thereafter, the return to the normal control state is the same as described above. The conditions for setting the number of data N, the proportionality constant P, and the integration constant I, which are the elements of the digital filter having the long time constant, are affected by disturbance that may have about several hundred seconds of the satellite time signal S1pps. Alternatively, a temperature correction method using a combination of desired filter conditions that causes the output frequency fout to fluctuate below the allowable range due to the disturbance may be used.

According to the configuration of the present invention, the ambient temperature detecting means 60 is provided, and the estimation calculating section 22 in the frequency controlling calculating means 13 corrects the frequency fluctuation for a relatively short time caused by the temperature fluctuation in the apparatus. By providing the control algorithm, a relatively short-time frequency variation due to a temperature variation is also corrected. As a result, a remarkable advantage that a more accurate generation of the output frequency fout is realized is obtained.

In the description of the above embodiment, the specific configuration example shown in FIG. 1 has been described. If desired, as shown in FIG. 4, a frequency converter for converting the output of the voltage controlled oscillator 10 to a predetermined frequency A17 (for example, a synthesizer or DDS) may be provided. In this case, the frequency converter A
17 has the advantage that an arbitrary output frequency fout can be generated, and the convenience as an arbitrary ultra-high precision reference frequency source is further improved.

In the description of the above embodiment, the specific configuration example shown in FIG. 1 has been described. However, as shown in FIG. There is a means for providing a standard radio wave receiver 11b for receiving a standard radio wave and using it as a reference time signal. in this case,
Output frequency fout with accuracy corresponding to national standard radio wave
Is obtained.

In the description of the above embodiment, the specific configuration example shown in FIG. 1 has been described. However, as shown in FIG. There is a means for providing a communication / broadcasting network receiving / demodulating device 11c for receiving a reference frequency signal to be reproduced, reproducing a clock by a clock extracting circuit, and dividing the clock by a frequency divider to obtain a reference time signal. In this case, the output frequency fout can be generated with an accuracy corresponding to the reference frequency signal distributed on the communication network or the broadcast network. Further, there is obtained an advantage that a high-purity frequency signal in which jitter and wander due to the transmission line of the communication network are sufficiently suppressed can be generated.

[0027]

According to the present invention, the following effects can be obtained from the above description. According to the configuration of the present invention, the present invention enables stable and accurate generation of the output frequency fout even in an operation under a condition where the environmental temperature fluctuates. That is, as a result of correcting the frequency fluctuation in a relatively short time due to the temperature fluctuation in the apparatus, the output frequency fou with higher accuracy is corrected.
A remarkable effect of realizing the occurrence of t is obtained. In addition, since a large-sized constant temperature bath is not required, it is possible to obtain an advantage that it can be configured at a low cost, and that it can be easily reduced in size and weight and can be easily transported.

[Brief description of the drawings]

FIG. 1 is a configuration example of a reference frequency generation device according to the present invention.

FIG. 2 shows a seven-stage control mode and an example of setting conditions thereof.

FIG. 3 is an example of a convergence time characteristic to a target phase point.

FIG. 4 is a configuration example of another reference frequency generation device according to the present invention.

FIG. 5 is a configuration example of another reference frequency generation device according to the present invention.

FIG. 6 is a configuration example of another reference frequency generation device according to the present invention.

FIG. 7 is a configuration example of a conventional reference frequency generator.

[Explanation of symbols]

 Reference Signs List 10 voltage controlled oscillator 11 satellite radio receiver 11b standard radio receiver 11c communication network / broadcast network reception demodulator 12 time interval measurement unit 13 frequency control arithmetic unit 14 D / A converter 15 frequency divider 17 frequency converter A ( (Synthesizer) 22 estimation calculation unit 29 temperature sensor 60 ambient temperature detection means

Claims (9)

[Claims] A voltage-controlled oscillator whose oscillation frequency is controlled by an applied DC voltage; a receiver that receives a highly accurate reference frequency signal from the outside and demodulates the signal into an input time signal; A time interval measuring unit for measuring a time interval between the internal time signal obtained by dividing the output frequency of the voltage controlled oscillator by the frequency divider and the input time signal, and determining the voltage controlled oscillator from the measured value of the time interval measuring unit A reference frequency generator for controlling a voltage control input terminal of the voltage-controlled oscillator by the frequency control operation means, the ambient temperature detection means for detecting an internal temperature of the apparatus; Temperature fluctuation correction means for receiving a temperature signal from the ambient temperature detection means and correcting the frequency fluctuation accompanying the temperature fluctuation in a short time is additionally provided to the frequency control arithmetic means; To Characteristic reference frequency generator. 2. A satellite radio receiver having a voltage-controlled oscillator whose oscillation frequency is controlled by an applied DC voltage, receiving a radio wave of an artificial satellite having a built-in atomic frequency standard, and demodulating an input time signal. A time interval measuring unit for measuring a time interval between the internal time signal obtained by dividing the output frequency of the voltage controlled oscillator by a frequency divider and the satellite time signal, from a measured value of the time interval measuring unit. A frequency control calculating means for calculating a digital control value for synchronizing the oscillation frequency of the voltage controlled oscillator; receiving the digital control value calculated by the frequency controlling calculating means, A reference frequency generator having a D / A converter for converting a DC voltage to be supplied to an end; an ambient temperature detecting means for detecting an internal temperature of the apparatus; Reference frequency generator provided the temperature variation correction means adds the frequency control computation section, and characterized in that it comprises more than to correct the short time frequency variation accompanying. 3. A voltage-controlled oscillator having an oscillation frequency controlled by an applied DC voltage, and a frequency converter A for converting an output frequency of the voltage-controlled oscillator into a predetermined frequency,
Receiving the radio waves of artificial satellites with a built-in atomic frequency standard,
A time interval measuring unit for measuring a time interval between an internal time signal obtained by dividing an output frequency of the frequency converter A by a frequency divider and the satellite time signal, the receiver having a satellite radio receiver for demodulating a satellite time signal; A frequency control arithmetic means for calculating a digital control value for synchronizing the oscillation frequency of the voltage-controlled oscillator from a measured value of the time interval measuring unit, and a digital control value calculated by the frequency control arithmetic means A reference frequency generator having a D / A converter for converting the received voltage into a DC voltage supplied to a voltage control input terminal of the voltage controlled oscillator; Temperature fluctuation correction means for receiving the temperature signal from the means and correcting the frequency fluctuation accompanying the temperature fluctuation in a short time in addition to the frequency control arithmetic means, and comprising: The reference frequency generator. 4. A temperature fluctuation correcting means for correcting a frequency fluctuation caused by a temperature fluctuation in a short time by reducing the number N of data of a digital filter having a long time constant by an estimating operation part of an operation means for frequency control, and 4. The reference frequency generator according to claim 1, wherein the constant P is increased and the integral constant I is decreased to correct the frequency of short-time temperature fluctuation. 5. A temperature fluctuation correcting means for correcting a frequency fluctuation due to a temperature fluctuation in a short time by reducing the number N of data of a digital filter having a long time constant by an estimating operation section of an operation means for frequency control. 4. The reference frequency generator according to claim 1, wherein the frequency is corrected in response to a time-dependent temperature change. 6. A temperature fluctuation correcting means for correcting a frequency fluctuation caused by a temperature fluctuation in a short time by increasing a proportional constant P of a digital filter having a long time constant by an estimating operation unit of a frequency control operation means. 4. The reference frequency generator according to claim 1, wherein the frequency is corrected in response to a time-dependent temperature change. 7. A temperature fluctuation correcting means for correcting a frequency fluctuation due to a temperature fluctuation in a short time by reducing an integral constant I of a digital filter having a long time constant by an estimating operation unit of a frequency control operation means. 4. The reference frequency generator according to claim 1, wherein the frequency is corrected in response to a time-dependent temperature change. 8. The reference frequency generator according to claim 2, wherein a standard radio wave receiver for receiving a national standard radio wave is used instead of the satellite radio wave receiver. 9. A frequency divider which receives a reference frequency signal distributed through a communication network or a broadcast network and converts it into a reference time signal, instead of the satellite radio wave receiver. Reference frequency generator as described.