JPH0354920A - Loose coupling oscillator interlocking with reference radio wave receiver - Google Patents

Abstract

PURPOSE:To obtain a highly accurate frequency signal without using an expensive atomic frequency standard by variably controlling the frequency of an oscillation output obtained from a loose coupling oscillator based upon a phase difference obtained by comparison. CONSTITUTION:A standard radio wave received from as antenna 22 is applied to a phase comparator 30 through a high frequency amplifier 24 and an intermediate frequency amplifier 26 and compared with the phase-compared with an output signal from a voltage controlled type crystal oscilaltor (VCXO) 44 and the phase-adjusted signal is outputted to a digital phase comparator 34. The comparator 30 is driven by an output signal from a synchronism detector 28 for detecting synchronism between the output signals of a phase shifter 32 and an intermediate frequency amplifier 26 and phase synchronism is executed only in the mark part of the received wavelength reference radio wave. In addition to the output of the phase shifter 32, an output from the VCXO 44 is also inputted to the comparator 34, compares both the input signals in each 2 seconds and outputs the compared result to a digital filter 36.

Description

[Detailed Description of the Invention] <Industrial Application Fields> The invention relates to a weakly coupled oscillator linked to a phase-tracking standard radio wave receiver, and in particular corrects phase fluctuations due to radio wave propagation of standard radio waves, and ! This paper concerns the configuration of a weakly coupled oscillator to obtain a signal that is highly precisely synchronized with the vibration. (Prior art) Conventionally, when obtaining a highly accurate reference frequency for frequency measurement and calibration of various devices, a standard radio wave with the output of an atomic frequency standard as a modulation signal or carrier wave was received, and a comparison signal to be calibrated was received from that signal. There is a method of tracking the phase, and a method of receiving the output of the atomic frequency standard via a digital communication network and using a weakly coupled oscillator to reproduce stable and highly accurate output synchronized with the output of the atomic frequency standard. .

Standard radio waves are the reference frequencies for radio wave management, academic research, industrial activities, etc. Standard radio waves in Japan are created using the cesium beam frequency standard as a prototype, and their accuracy is 10 to 13. maintain high precision,
The frequency band is one long wave and five short waves.

In the case of the above-mentioned shortwave standard radio waves, the radio waves propagate through ionospheric propagation, so they have long range, but due to the Doppler effect caused by fluctuations in the propagation path, the signal reception accuracy remains at a frequency of 10-7 to 10. ing. On the other hand, in the case of long-wave standard radio waves, the propagation of radio waves f has a long wavelength, so there is little attenuation of surface waves, and spatial waves are also reflected at the lowest ionosphere (D layer), where they are most stable, so both frequency and intensity are stable. By correcting sudden phase fluctuations due to diurnal phase fluctuations or sudden onset ionospheric disturbances, highly accurate frequency comparisons of about 10 can be obtained in 24-hour comparisons. For the reasons mentioned above, when performing high-precision frequency measurements using standard radio waves, a phase-tracking type long-wave standard radio wave receiver is used, and the phase of the received standard radio wave is compared with the phase of the local standard frequency. A means is used to control the phase of the local standard frequency using a phase shifter so that the phases of the local standard frequencies always match. However, the accuracy of the method of obtaining high-precision output using standard radio waves is affected by the influence of the radio wave propagation path, and there are cases where the standard radio wave cannot be received by the receiver due to deterioration of the standard radio field strength or stoppage. etc. had the problem that it was not possible to obtain highly accurate frequency signals.

On the other hand, the method of directly extracting a reference clock from a digital communication four-wire network and using this clock signal to obtain a highly accurate output is different from the case of using standard radio waves as described above, and is not affected by the electric field layer, but the propagation Since phase fluctuations (jitter) are superimposed due to road effects, there is a problem that it cannot be used for direct communication devices. In order to eliminate this problem, the method of extracting the reference clock from the digital communication line and obtaining a highly accurate frequency signal is as follows.
By controlling the weakly coupled oscillator using this reference clock, the effects of system jitter etc. are removed. However, the method using the digital communication network described above requires a dedicated line and has the problem that a highly accurate standard frequency cannot be easily obtained at any location. (Objective of the Invention) The present invention has been devised in view of the conventional problems as described above, and has the advantage of radio wave propagation in that the standard radio wave can be captured at any position, and the reception strength of the standard frequency signal deteriorates. To provide a weakly coupled oscillator that is interlocked with a standard radio wave receiver, which can prevent direct influence even when the standard radio wave is stopped or when the standard radio wave is stopped, and can obtain extremely high-precision frequency signals. (Summary of the Invention) In order to achieve this purpose, the weakly coupled oscillator interlocked with the standard radio wave receiver of the present invention converts the phase tracking signal, which is the demodulated signal from the standard radio wave receiver, into the weakly coupled oscillator. and input the weakly coupled oscillator output to the standard radio wave receiver as an external reference signal of the standard radio wave receiver, and compare the phases of the weakly coupled oscillator output signal and the phase tracking signal in the weakly coupled oscillator. The present invention is characterized in that a signal synchronized with the standard radio wave signal is obtained by variably controlling the frequency of the oscillation output of the weakly coupled oscillator based on the phase difference obtained by the comparison.

<<Example>> Hereinafter, the present invention will be explained in detail based on an example shown in the drawings. First, in order to facilitate understanding of this embodiment, a standard frequency reception method using a conventionally used standard radio wave receiver and a method for obtaining a standard frequency signal using digital communication [ilOEJi KN] will be briefly explained.

FIG. 2 is a block diagram showing the circuit configuration of a device for measuring relative frequency deviation using a conventional long-wave standard radio wave receiver, in which 1 is an antenna;
The standard radio waves received through the antenna are transmitted to the high frequency amplifier 2.
and input to the phase comparator 6 via the intermediate frequency amplifier 3,
The amount of phase change of the signal under test is measured using the input signal as a reference, and the output of the phase comparator 6 is given to the next stage phase shifter 5, and the phase shifter 5 responds to the output of the phase comparison i}36. Controls the shift of the signal under test, outputs it as a phase tracking signal output, and if necessary, changes the control amount in the phase shifter 5 to D.
/A converter 7 and output as an analog signal. Further, the carrier wave of the AM radio wave is, for example, 40k}l2,5
0 0 nas is an intermittent IHz signal, and by inputting the standard radio wave signal and the phase shifter 5 output signal to the synchronous detector 4, the phase comparator is controlled to operate only in the marking part of the standard radio wave signal. ．． The phase tracking type (phase pull type) phase synchronization method as described above is
Compared to other methods of standard frequency signal means using radio waves, such as methods using flip-flop phase comparison receivers or PLL receivers, standard frequency signals do not require gate circuit control or filters. It has the advantage of being able to perform highly accurate frequency comparisons even when the signal level is below the noise level, and obtaining a highly stable standard frequency. On the other hand, means using a weakly coupled oscillator to obtain a standard frequency using a digital communication network is as shown in FIG. The oscillator (hereinafter referred to as vCX○) 18 has been warned. The synchronized clock signal from the digital communication circuit network and the output signal from the VCX○18 are input to the digital phase comparator 10, and the digital phase comparator 10 detects the phase difference between them every 2 milliseconds, for example. The output is given to the next stage digital filter 14. The digital filter 14 provides the microprocessor 12 with 8.192 seconds worth of data output from the digital phase comparator 10 every 2 milliseconds, that is, 4096 pieces of phase difference data.
The average value of the phase difference data for 2 seconds is calculated, and the difference between the average values is also calculated, and the result is outputted to the next-stage digital-to-analog converter 16 via the digital filter 14. The digital-to-analog converter 16 generates a DC voltage based on a control signal generated according to the average value of the phase difference for 8y1.92 seconds applied by the digital filter 14, and applies this to the next stage VCXO 18, the result,
The output of the VCXO 18 is corrected for the phase difference with the synchronous clock supplied from the communication network, and oscillates an output signal precisely 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 which is the output of the phase shifter 5 shown in FIG. It can be used as the synchronized clock shown in the figure, but in order to suppress jitter caused by the digital line network, the input phase fluctuation (jitter) suppression period of the weakly coupled oscillator G is generally about 8 to 10 seconds or less. Because of this setting, phase fluctuations with a period of several tens of minutes to several hours due to radio wave propagation that occur due to standard radio waves are superimposed on the demodulated signal of the long wave standard radio wave receiver and are supplied as the synchronization clock of the weakly coupled oscillator. The problem was that it could not be suppressed.

In addition, if the average value calculation period of the digital filter section in the weakly coupled oscillator is lengthened in order to suppress phase fluctuations due to radio wave propagation, the interval for controlling the VCXO becomes too long, resulting in loss of short-term frequency stability. There was a problem with it being put away.

In order to eliminate these above-mentioned problems, a weakly coupled oscillator using a 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, 32 is a phase shifter, 34 is a digital phase comparator, 3
6 and 38 are digital filters, 40 and 41 are microprocessors, 42 is a digital to analog converter, 4
4 is a voltage controlled crystal oscillator (VCXσ).

In the device configured as described above, the standard radio wave received from the antenna 22 is given to the phase comparator 30 via the high frequency amplifier 24 and the intermediate frequency amplifier 26, and the phase is compared with the output signal of the VCXO 44. Based on the comparison result, the following is performed. It controls the phase shifter 32 in the stage, adjusts the phase of the output of the VCXO 44, and outputs the phase-adjusted signal to the digital phase comparator 34.

The phase comparator 30 includes a phase shifter 32 and an intermediate frequency amplifier 26.
It operates based on the output of the synchronous detector, and phase synchronization is performed only in the mark portion of the received long-wave standard radio wave.

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

In the digital filter 36, the phase difference signal input every 2 milliseconds is sent to the microprocessor 40 which performs arithmetic processing, and the microprocessor 40 calculates the average value by inputting 4096 phase difference signals (8.192 seconds). 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 the next stage digital filter 38, and the digital filter 38 outputs the signal to the microprocessor 41. The microprocessor 4l processes ゜゜T' in order to further smooth the average phase difference comparison data for the 8.192 seconds.
MM of data for ゜ hours, calculates a moving average value for "T'' hours every 8.192 seconds, converts the calculated value into control data, and outputs it to the D/A converter 42. That is, The digital filter 38 is set to a time that sufficiently suppresses long-period phase fluctuations within several tens of minutes to several hours caused by radio wave propagation, and the "T" time may be, for example, about 10 hours.

The digital analog filter 38 outputs control data with suppressed short-cycle, medium-, and long-cycle phase fluctuations to the next stage D/A.
D that outputs the control data to the A converter 42 and inputs the control data.
The /A converter 42 converts the input digital signal into a DC voltage and controls the VCXO 44 to convert the standard radio wave i
It can be synchronized with high precision to the oscillation frequency of the cesium beam frequency marker. Note that the microprocessors 40 and 4l cyclically store the extracted data in their internal memory or external memory as shown in the figure, and can obtain a phase tracking signal from the receiver depending on the deterioration of the electric field strength or the stoppage of the electric field. Even if this is not possible, the voltage-controlled crystal oscillator may continue to output in a free-running state using the control data input immediately before as an initial value, and the receiver may also output a phase tracking signal. When the signal is output again, the phase difference between the weakly coupled oscillation output and the phase tracking signal is corrected so that it becomes the same value as the phase difference just before the phase tracking signal stopped or became unobtainable due to deterioration of the electric field strength, etc. If control is started again to synchronize with the standard radio wave, it is effective to correct the phase difference that occurred during the free-running period of the voltage-controlled oscillator and to speed up the cycle for the standard radio wave that is re-input. Therefore, when receiving a standard radio wave signal, it is possible to correct short, medium and long period phase difference fluctuations, and obtain a weakly coupled signal output with highly accurate frequency synchronization. If this is not possible, the voltage-controlled crystal oscillator is made to run freely based on the data stored in the microprocessor, making it possible to obtain a nearly stable output. Although the embodiments of the present invention have been described using two microprocessors, the present invention is not limited to this, and a single microprocessor may perform the arithmetic processing for both, or the day, month, year, etc. In order to accommodate three or more different period fluctuations, it may be useful to cascade-connect filter blocks that calculate the average phase change for each period.

Further, although the case where a long wave standard radio wave is received as the standard radio wave has been described, the present invention is not limited to this, and the same effect can be obtained even if the present invention is applied to a case using a short wave standard radio wave.

Furthermore, even if a signal based on another atomic frequency standard is extracted, for example a television synchronization signal, and the synchronization signal is used as a phase tracking signal, a highly accurate and highly stable signal can be similarly created. Although the explanation has been given using a voltage-controlled crystal oscillator as a weakly coupled oscillator, it is clear that other types of oscillators may be used as long as the oscillation frequency can be controlled. (Effects of the Invention) As explained above, the weakly coupled oscillator interlocked with the standard radio wave receiver of the present invention does not have various time periods due to radio wave propagation, and can perform synchronous control in short periods while suppressing phase fluctuations. It is possible to obtain a stable weakly coupled signal output, and even when a phase tracking signal cannot be obtained due to deterioration of electric field strength or signal stoppage, it is possible to output a relatively stable frequency signal by free running, so it is expensive. This method has a remarkable effect on obtaining highly accurate frequency signals without using a standard atomic frequency standard.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a block diagram of a device for measuring relative frequency deviation using a conventional long-wave standard radio wave receiver, and Fig. 3 is a diagram showing an apparatus for measuring relative frequency deviation using a conventional long-wave standard radio wave receiver. Fig. 2 is a block diagram of a device for obtaining standard frequencies. 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 analog converter, 10, 34...Digital phase comparator, 12, 40
, 41... microprocessor, 14, 36, 38...
Digital filter, 18, 44...voltage controlled holy crystal oscillator

Claims (1)

[Claims] It consists of a standard radio wave receiver and a weakly coupled oscillator that operates in conjunction with the standard radio wave receiver, and in the standard radio wave receiver, the output of the weakly coupled oscillator is synchronized with the standard radio wave signal to generate a phase tracking signal. , Comparing the phases of the weakly coupled oscillator output signal and the phase tracking signal in the weakly coupled oscillator, and variably controlling the phase or frequency of the oscillation output of the weakly coupled oscillator based on the phase difference obtained by the comparison. A weakly coupled oscillator linked with a long wave standard radio wave receiver, characterized in that a signal synchronized with a standard radio wave signal is obtained by