JP2855449B2 - Standard frequency signal generator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a weak-coupled oscillator linked to a phase tracking type standard radio receiver, and in particular, corrects phase fluctuations caused by radio wave propagation of a standard radio wave, and The present invention relates to a configuration of a standard frequency signal generation device for obtaining a signal synchronized with the original vibration with high accuracy.

(Prior art) Conventionally, when obtaining a high-precision reference frequency for measuring and calibrating the frequency of various devices, a standard signal with the output of an atomic frequency standard device as a modulation signal or a carrier wave is received and a comparison signal for calibration is obtained. There is a method of tracking the phase and a method of receiving the output of the atomic frequency standard through a digital communication network and reproducing a stable and highly accurate output synchronized with the output of the atomic frequency standard using a weakly coupled oscillator. .

Standard radio waves are used as reference frequencies for radio wave management, academic research, and industrial activities.Standard radio waves in Japan are created using cesium beam frequency standards as standard equipment, and their accuracy is as high as ^10-13 units. Accuracy is maintained, and the frequency band is transmitted as one long wave and five short waves.

In the case of the above-mentioned short-wave standard radio wave, since radio wave propagation is performed by ionospheric propagation, the signal reception accuracy is limited to 10 ^-7 to 10 ^-8 in frequency due to the Doppler effect caused by fluctuation of the propagation path, although there is a long reach. ing.

On the other hand, in the case of the longwave standard radio wave, the radio wave propagation has a long wavelength, so that the attenuation of the surface wave is small, and the spatial wave is also reflected at the lowest stable ionosphere (D layer), so that both the frequency and the intensity are stable. By correcting sudden phase fluctuations due to diurnal phase fluctuations or sudden ionospheric disturbances, a highly accurate frequency comparison of about 10 ^{-11 in a} 24-hour comparison can be obtained.

When performing high-precision frequency measurement using a standard radio wave for the above-described reason, a phase tracking long-wave standard radio receiver is used, and the phase of the received standard radio wave is compared with the phase of the local standard frequency. For controlling the phase of the local standard frequency by a phase shifter so that the phase of the local standard frequency always coincides.

However, the method of obtaining high-precision output using the standard radio wave depends on the influence of the radio wave on the propagation path, and the accuracy is influenced by the standard radio wave. And the like have a problem that a highly accurate frequency signal cannot be obtained.

On the other hand, a method of directly extracting a reference clock from a digital communication network and obtaining a high-precision output using the clock signal is different from the case of using a standard radio wave as described above, although it is not affected by an electric field layer, but on a propagation path. There is a problem that the phase fluctuation (jitter) is superimposed due to the influence of the above and cannot be used for a direct communication device or the like.

In order to eliminate this problem, a method of extracting a reference clock from a digital communication network and obtaining a high-precision frequency signal removes the influence of system jitter and the like by controlling a weakly coupled oscillator using the reference clock. ing.

However, the method using the digital communication line network has a problem that a dedicated line is required and a high-precision standard frequency cannot be easily obtained at an arbitrary place.

(Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and has the advantage of radio wave propagation of capturing a standard radio wave at an arbitrary position, and the reception strength of a standard frequency signal is deteriorated. Provide a standard frequency signal generator linked to a standard radio receiver that can obtain an extremely high-precision frequency signal by preventing the direct influence of the standard radio wave even when the standard radio wave is interrupted or when the standard radio wave stops. The purpose is to do.

(Summary of the Invention) In order to achieve this object, the invention according to claim 1 of the standard frequency signal generating apparatus according to the present invention comprises a standard radio receiver and a weakly coupled oscillator operating in conjunction with the standard radio receiver. And generating a phase tracking signal in which the output of the weakly coupled oscillator is synchronized with the standard time signal in the standard radio receiver, and the phase of the output signal of the weakly coupled oscillator and the phase tracking signal in the weakly coupled oscillator. A signal synchronized with the signal of the standard radio wave is obtained by variably controlling the phase or frequency of the oscillation output of the weakly coupled oscillator based on the phase difference obtained by the comparison.

The invention according to claim 2 of the standard frequency signal generating device according to the present invention is characterized in that the standard radio wave receiving means for receiving a standard radio wave, the oscillation means capable of controlling the oscillation frequency, the output signal of the oscillation means and the standard A first phase comparison unit that receives a standard radio signal from the radio wave reception unit and compares the phases of the two; and a phase tracking signal that synchronizes the output of the oscillation unit with the standard radio signal based on the output of the comparison unit. A second phase comparing means for comparing the phase tracking signal output from the phase shifting means with the oscillating means output means; A first filter means for detecting control phase data which suppresses the short-period phase fluctuation and an output from the first filter means, and detects medium- and long-period phase fluctuations. Detecting, and And a second filter means for outputting control data suppress phase variation period, the second
Wherein the phase or oscillation frequency of the oscillation means output is controlled by the filter means output.

(Examples) Hereinafter, the present invention will be described in detail based on examples shown in the drawings.

First, a standard frequency receiving method using a standard radio wave receiver and a method of obtaining a standard frequency signal using a digital communication network will be briefly described to assist understanding of the present embodiment.

FIG. 2 is a block diagram showing a circuit configuration of a device for measuring a relative frequency deviation using a conventionally used long-wave standard radio wave receiver. In FIG. 2, reference numeral 1 denotes an antenna, The received standard radio wave is input to the phase comparator 6 via the high frequency amplifier 2 and the intermediate frequency amplifier 3 to measure the amount of phase change of the signal under measurement with reference to the input signal. The phase shifter 5 controls the amount of phase shift of the signal under measurement according to the output of the phase comparator 6, outputs the signal as a phase tracking signal output, and, if necessary, outputs the phase shifter 5 Control amount in D /
The signal is output as an analog signal via the A converter 7.

The standard radio wave is, for example, a signal obtained by modulating a carrier wave of 40 kHz with a modulation wave (time code) of 1 Hz, and the carrier wave of 40 kHz repeats intermittently every 500 ms. By inputting the standard radio signal and the output signal of the phase shifter 5 to the synchronous detector 4, the synchronous detector 4 allows the phase comparator 6 to operate only when a 40 kHz signal, which is a marking part of the standard radio signal, arrives. It operates so as to stop when a space part is input.

The phase tracking type (phase pull-in type) phase synchronization method described above uses another method, such as a flip-flop type phase comparison receiver or a PLL type receiver, among standard frequency signal means using a long-wave standard radio wave. Compared to the conventional method, there is no need for gate circuit control and filters, so even if the level of the standard radio wave falls below the noise level, it is possible to compare frequencies with high accuracy and obtain a highly stable standard frequency. Have

On the other hand, means using a weakly coupled oscillator for obtaining a standard frequency using a digital communication network is, as shown in FIG. 3, a digital phase comparator 10, a microprocessor 12, a digital filter 14, a digital / analog converter 16 and a voltage controlled crystal. An oscillator (hereinafter referred to as VCXO) 18 is provided.

VCXO18 with synchronous clock signal from digital communication network
Is output to a digital phase comparator 10, and the digital phase comparator 10 detects the phase difference between
The output is detected every millisecond and its output is supplied to the digital filter 14 at the next stage.

The digital filter 14 supplies data for 8.192 seconds output from the digital phase comparator 10 every 2 milliseconds, that is, 4096 phase difference data to the microprocessor 12, and the microprocessor 12 outputs the data for 8.192 seconds. The average value of the phase difference data is calculated, and the difference between the average values is also calculated. The result is output to the next-stage digital-to-analog converter 16 via the digital filter 14.

The digital-analog converter 16 generates a DC voltage based on the control signal generated according to the phase difference average value for 8.192 seconds applied from the digital filter 14, applies the DC voltage to the next-stage VCXO 18, and as a result, The output of the VCXO 18 is corrected for a phase difference from a synchronous clock supplied from a communication network, and oscillates an output signal accurately synchronized with the synchronous clock.

Therefore, in order to control the weakly coupled oscillator with the standard frequency signal extracted from the long wave standard radio wave and obtain a highly accurate frequency signal, the phase tracking signal output from the phase shifter 5 shown in FIG. Although it may be used as the synchronization clock in the figure, the input phase fluctuation (jitter) suppression period in the weakly coupled oscillator is generally set to be about 8 seconds to 10 seconds or less in order to suppress the jitter caused by the digital network. Tens of minutes due to radio wave propagation caused by standard radio waves
The phase fluctuation of several hours is supplied as a synchronous clock of the weakly coupled oscillator while being superimposed on the demodulated signal of the long wave standard radio receiver, and there is a problem that it cannot be suppressed.

Also, if the average value calculation cycle of the digital filter unit in the weakly coupled oscillator is lengthened to suppress phase fluctuation due to radio wave propagation, the VCXO control interval becomes too long, and short-term frequency stability is lost. There was a problem that it would.

In order to eliminate these problems described above, a weakly coupled oscillator using the standard radio wave receiver according to the present invention is configured as shown in FIG. 1, for example.

In the figure, 22 is an antenna, 24 is a high-frequency amplifier, 26
Is an intermediate frequency amplifier, 28 is a synchronous detector, 30 is a phase comparator as first phase comparing means, 32 is a phase shifter as phase shifting means,
34 is a digital phase comparator as a second phase comparing means, 35
Is a first filter means, 37 is a second filter means, 36 and 38 are digital filters, 40 and 41 are microprocessors, 42 is a digital-to-analog converter, 44 is a voltage crystal oscillator (VCXO) which is an oscillating means, The high-frequency amplifier
The reference numeral 24 and the intermediate frequency amplifier 26 are a part of standard radio wave receiving means for receiving a standard radio wave.

In the device configured as described above, the standard radio wave received from the antenna 22 is transmitted to the high frequency amplifier 24 and the intermediate frequency amplifier 26.
The phase comparison is performed with the output signal of the VCXO 44 provided to the phase comparator 30 via the
, And adjusts the phase of the output of the VCXO 44, and outputs the adjusted phase tracking signal to the digital phase comparator 34.

The synchronous detector 28 synchronously detects the output of the intermediate frequency amplifier 26 using the output of the phase shifter 32 and demodulates the time code (modulated wave) superimposed on the standard radio signal.

By operating based on the output of the synchronous detector 28, the phase comparator 30 performs the phase comparison only at the mark portion of the received long-wave standard radio wave, that is, at the timing at which the carrier signal of 40 kHz exists.

The digital phase comparator 34 also receives an output signal from the VCXO 44 in addition to the output of the phase shifter 32, compares the phases of both input signals every 2 milliseconds, and outputs the result to the digital filter 36. .

In the digital filter 36, a phase difference signal input every 2 milliseconds is given to a microprocessor 40 for performing arithmetic processing, and the microprocessor 40 calculates an average value by inputting 4096 (8.192 seconds) phase difference signals. The output of the digital filter 36 is controlled based on the calculated value.

That is, the digital filter 36 suppresses short-period jitter, and its output is average phase difference comparison data for 8.192 seconds.

The output of the digital filter 36 is input to a digital filter 38 in the next stage, and the digital filter 38 outputs the signal to a microprocessor 41.

The microprocessor 41 accumulates data for “T” time in order to further smooth the average phase difference comparison data for 8.192 seconds, and calculates a moving average value for “T” time every 8.192 seconds, The calculated value is converted into control data and D /
Output to A converter 42.

That is, the digital filter 38 is a number generated by radio wave propagation.
The time may be set so as to sufficiently suppress long-period phase fluctuations from 10 minutes to several hours, and the “T” time may be set to, for example, about 10 hours.

The output of the digital filter 38 outputs control data in which the short-cycle, middle- and long-cycle phase fluctuations are suppressed to the D / A converter 42 at the next stage, and the D / A converter 4 that receives the control data.
2 converts the input digital signal to DC voltage and controls the VCXO44 to synchronize with the oscillation frequency of the cesium beam frequency standard device, which is the standard device of the standard radio wave, with high accuracy.

The microprocessors 40 and 41 cyclically store the extracted data in their internal memory or an external memory (not shown), and obtain a phase tracking signal from the receiver due to deterioration of electric field strength or wave interruption. May not be possible, the voltage-controlled crystal oscillator may continue to output in the free-running state with the control data input immediately before as the initial value, and further, the phase tracking signal may be output from the receiver. When output again, the phase difference of the weakly coupled oscillation output with respect to the phase tracking signal is corrected so that the phase tracking signal has the same value as the phase difference immediately before it is not obtained due to the stoppage of the wave or the deterioration of the electric field strength, If control is started again so as to synchronize with the standard radio wave, it is effective to correct the phase difference generated during the free-running period of the voltage-controlled oscillator and to advance the cycle of the standard radio wave to be re-input. You.

Therefore, when receiving the standard radio signal,
Corrects medium and long-period phase difference fluctuations to obtain a weakly-coupled signal output that is frequency-synchronized with high precision, and if the standard radio signal cannot be obtained for any reason, the data stored in the microprocessor , The voltage-controlled crystal oscillator runs on its own, so that a substantially stable output can be obtained.

In the embodiment of the present invention, the description has been made using two microprocessors. However, the present invention is not limited to this. One microprocessor may perform both arithmetic processing, or a day, month, year, etc. It would also be useful to cascade filter blocks that calculate the average phase change for each period to accommodate three or more different periodic variations.

Also, the case where the long wave standard radio wave is received as the standard radio wave has been described. However, the present invention is not limited to this, and the same effect can be obtained by applying to the radio wave using the short wave standard radio wave.

In addition, signals based on other atomic frequency standards,
For example, by extracting a television synchronization signal and using the synchronization signal as a phase tracking signal, a highly accurate and highly stable signal can be similarly produced. Also, a voltage-controlled crystal oscillator is used as a weak coupling oscillator. As described above, it is clear that other types of oscillators can be used as long as the oscillators can control the oscillation frequency.

(Effect of the Invention) As described above, the standard frequency signal generation device of the present invention performs stable short-coupling by performing synchronization control in a short period while suppressing phase fluctuations having various time periods due to radio wave propagation. It is an expensive atomic frequency standard because it can output a signal and can output a relatively stable frequency signal by self-propelled even while a phase tracking signal cannot be obtained due to deterioration of electric field strength or stoppage. There is a remarkable effect in obtaining a high-precision frequency signal without using a signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a block diagram of an apparatus for measuring a relative frequency deviation using a conventional long-wave standard radio receiver, and FIG. FIG. 2 is a block diagram of a device for obtaining a standard frequency by using the system shown in FIG. 1, 22 ... antenna, 2, 24 ... high frequency amplifier, 3, 26
…… Intermediate frequency amplifier, 4, 28 …… Synchronous detector, 6, 30…
... Phase comparator, 5, 32 ... Phase shifter, 7, 16, 42 ... Digital-to-analog converter, 10, 34 ... Digital phase comparator, 12, 40, 41 ... Microprocessor, 14, 36, 38 …
… Digital filter, 18, 44 …… Voltage controlled crystal oscillator

Claims (2)

(57) [Claims] 1. A phase tracking signal comprising a standard radio receiver and a weakly coupled oscillator operating in conjunction with the standard radio receiver, wherein the output of the weakly coupled oscillator is synchronized with a standard radio signal in the standard radio receiver. And comparing the phases of the weakly coupled oscillator output signal and the phase tracking signal in the weakly coupled oscillator, and based on the phase difference obtained by the comparison, determines the phase or frequency of the transmission output of the weakly coupled oscillator. A standard frequency generator, wherein a signal synchronized with a signal of a standard radio wave is obtained by performing variable control. 2. A standard radio wave receiving means for receiving a standard radio wave,
The transmitting frequency control receives the transmitting means, the output signal of the transmitting means and the standard radio signal from the standard radio receiving means,
First phase comparing means for comparing the phases of the two, phase shifting means for generating a phase tracking signal in which the output of the transmitting means is synchronized with the standard radio signal based on the output of the comparing means, and output by the phase shifting means Second phase comparing means for comparing the obtained phase tracking signal with the transmitting means output means, and inputting the output of the second phase comparing means to detect short-period phase fluctuations, First filter means for outputting control data with fluctuations suppressed, and an output from the first filter means being input to detect medium- and long-period phase fluctuations and to detect medium- and long-period phase fluctuations A second filter for outputting suppressed control data, wherein the output of the second filter controls the phase or the oscillation frequency of the output of the transmitting means.