JP2012242190A - Reference signal generation device and reference signal generating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reference signal generation device and a reference signal generating method which can improve the continuity of a reference signal.SOLUTION: The reference signal generation device 100 includes: a GPS receiver 120 for acquiring a GPS reception time; a standard radio wave receiver 110 for acquiring a standard radio wave reception time, a storage part 140 for storing a time difference between the GPS reception time and the standard radio wave reception time; a time difference comparator 130 for correcting the standard radio wave time on the basis of a time difference corresponding to the current date and time; and PLL 150 for synchronizing a reference signal with an input signal generated on the basis of a GPS signal when a GPS reception fault does not occur, while synchronizing the reference signal with an input signal generated on the basis of the corrected standard radio wave reception time when a GPS reception fault has occurred. When recovering from the GPS reception fault, the PLL 150 divides a phase difference between the input signal and the reference signal into multiple pulses to gradually reduce it.

Description

  The present invention relates to a reference signal generator and a reference signal generation method.

There is a need for a highly accurate reference signal with little error. In order to generate the reference signal, a crystal oscillator is often used, but the output of the crystal oscillator has a frequency stability of about 1 × 10 ⁻¹⁰ (that is, + −1 Hz per 10 ¹⁰ Hz) even at the highest accuracy. Therefore, it cannot be used in a scene where a highly accurate reference signal is required, such as transmission / reception of FM broadcasting.

  Therefore, in a situation where a highly accurate reference signal is required, a so-called PLL (Phase Locked Loop) that synchronizes the output of the crystal oscillator with a more accurate input signal is generally used. For example, Patent Document 1 discloses a standard radio wave receiver that synchronizes the output of an oscillator to a high-accuracy 1-second signal that is output every second by a GPS (Global Positioning System) receiver and a standard radio wave receiver. Yes.

JP 2002-071854 A

  Since the GPS receiver generates a 1-second signal based on the GPS signal received from the GPS satellite, it cannot output a 1-second signal when radio waves cannot be received from the GPS satellite (hereinafter, this state is referred to as “holdover”). ").

  The apparatus of Patent Document 1 synchronizes the reference signal with the 1-second signal of the standard radio receiver when it cannot receive radio waves from the GPS satellite. Therefore, even if a holdover occurs, the accuracy of the reference signal is extremely high. There is no decline. However, when a holdover occurs, the signal to be synchronized is switched from the 1 second signal of the GPS receiver to the 1 second signal of the standard radio wave receiver, so that there is a problem that the continuity of the reference signal decreases before and after the occurrence of the holdover .

  The present invention has been made in view of such problems, and an object of the present invention is to provide a reference signal generating apparatus and a reference signal generating method capable of improving the continuity of a reference signal.

In order to achieve the above object, a reference signal generator according to a first aspect of the present invention includes:
GPS reception time acquisition means for acquiring GPS reception time based on the GPS signal;
Standard radio wave reception time acquisition means for acquiring the standard radio wave reception time based on the standard radio wave,
Storage means for storing time difference information associated with the time difference between the GPS reception time and the standard radio wave reception time with the received month, day, or time;
Correction means for acquiring a time difference corresponding to the current month, day, or time from the time difference information, and correcting the standard radio wave time based on the acquired time difference;
It has an oscillator that outputs a reference signal, and when no GPS reception failure has occurred, the reference signal is synchronized with an input signal generated based on the GPS signal, and corrected when a GPS reception failure has occurred Phase synchronization means for synchronizing the reference signal to the input signal generated based on the standard radio wave reception time,
The phase synchronization means divides the phase difference between the input signal generated based on the GPS signal and the reference signal into a plurality of pulses and gradually shortens when the GPS reception failure is recovered,
It is characterized by that.

In order to achieve the above object, a reference signal generation method according to a second aspect of the present invention includes:
A GPS reception time acquisition step of acquiring a GPS reception time based on the GPS signal;
A standard radio wave reception time acquisition step for acquiring a standard radio wave reception time based on the standard radio wave;
Storing a time difference between the GPS reception time and the standard radio wave reception time, the time difference information associated with the received month, day, or time;
A correction step of acquiring a time difference corresponding to the current month, day, or time from the time difference information and correcting the standard radio wave time based on the acquired time difference;
When a GPS reception failure has not occurred, the reference signal output from the oscillator is synchronized with the input signal generated based on the GPS signal, and when a GPS reception failure has occurred, the corrected standard radio wave reception time is set. The reference signal output from the oscillator is synchronized with the input signal generated based on the reference signal, and further, when the GPS reception failure is recovered, the phase difference between the input signal generated based on the GPS signal and the reference signal is A phase synchronization step that divides into multiple pulses and gradually shortens,
It is characterized by that.

  It is possible to provide a reference signal generation device and a reference signal generation method capable of improving the continuity of the reference signal.

1 is a block diagram of a reference signal generator according to an embodiment of the present invention. It is a figure for demonstrating the time difference calculated from GPS reception time and standard radio wave reception time. It is a figure which shows the example of the time-dependent change characteristic which plotted the time difference of GPS reception time and standard radio wave reception time for 1 hour in the table | surface. It is a figure which shows the example of the time change characteristic which plotted the time average of the time difference of GPS reception time and standard radio wave reception time for 1 day in the table | surface. It is a figure which shows the example of the secular variation characteristic which plotted the daily average of the time difference of GPS reception time and standard radio wave reception time for one year in the table | surface. It is a figure for demonstrating that the phase difference has generate | occur | produced between 1 Hz signal and 1 pps signal when GPS reception failure generate | occur | produces. It is a figure which shows a mode that a reference signal is gradually synchronized with a 1pps signal after GPS reception failure recovery.

  A reference signal generator according to an embodiment of the present invention will be described with reference to the drawings. The reference signal generator 100 is a device for generating a 10 MHz reference signal. As shown in FIG. 1, the standard radio wave receiver 110, the GPS receiver 120, the time information comparator 130, the storage unit 140, PLL150.

  The standard radio wave receiver 110 includes, for example, a receiver that receives a standard radio wave transmitted from a standard frequency time signal station operated by the National Institute of Information and Communications Technology. When receiving the standard radio wave, the standard radio wave receiver 110 acquires the standard radio wave reception time included in the standard radio wave and sequentially outputs it to the time information comparator 130. In the following description, it is assumed that the “standard radio wave reception time” is output from the standard radio wave receiver 110 every minute.

  The GPS receiver 120 includes a receiver that receives a GPS signal transmitted from a GPS satellite. When receiving the GPS signal, the GPS receiver 120 acquires the GPS reception time and 1 pps (Pulse Per Second) signal from the GPS signal, and sequentially outputs them to the time information comparator 130 and the phase comparator 151. Here, “GPS reception time” refers to time information with extremely high accuracy generated by an atomic clock mounted on a GPS satellite. The “1 pps signal” refers to a signal generated every second in synchronization with the GPS reception time, which is generated based on the GPS signal. The GPS reception time is output to the time information comparator 130, and the 1 pps signal is output to the phase comparator 151. The GPS receiver 120 stops outputting the GPS reception time and the 1 pps signal when the GPS reception failure occurs and the GPS signal cannot be received (hereinafter, this state is referred to as “holdover”).

  The time information comparator 130 includes an analog / digital processor for comparing the standard radio wave reception time and the GPS reception time. The time information comparator 130 associates the time difference ΔT (“ΔT1” and “ΔT2” shown in FIG. 2) between the standard radio wave reception time (tS) and the GPS reception time (tG) with the current date and time in the time difference database 141. Store. Further, the time information comparator 130 corrects the standard radio wave reception time based on the information stored in the time difference database 141, further generates a pseudo 1 pps signal based on the corrected standard radio wave reception time, and compares the phase. To the device 151. Here, the “pseudo 1 pps signal” is generated by dividing the standard radio wave reception time output every minute into signals per second using a built-in crystal oscillator (not shown), for example. This is a pseudo 1 pps signal.

  The storage unit 140 includes a storage device such as a hard disk, and stores various data such as a time difference database 141 and setting parameters 142.

  The time difference database 141 is a database that stores the time difference calculated by the time information comparator 130 and the calculated date and time in association with each other. The time difference database 141 stores “time-varying characteristic information” in which the time difference between the standard radio wave reception time and the GPS reception time is stored in association with the current date every minute, and the time difference between the standard radio wave reception time and the GPS reception time. "Daily change characteristic information" in which the average value of the day is stored in association with the date, and "annual change characteristic information" in which the average value for one month of the time difference from the GPS reception time is stored in association with the month; Are stored ("Aging characteristics information", "Aging characteristics information", and "Aging characteristics information" will be described later).

  The setting parameter 142 is a value for designating the magnitude of “time synchronization time” required for the reference signal to synchronize with the input signal after the GPS reception failure is recovered, and at the manufacturing stage of the reference signal generator 100, It is stored in advance by a manufacturer or the like.

  Here, the “time synchronization time” is calculated based on the time required for recovery from the GPS reception failure after the GPS reception failure (hereinafter referred to as “holdover time”) and the setting parameter 142. It is a value. For example, if the holdover time is Th and the value of the setting parameter 142 is m, the time synchronization time is Th / m obtained by dividing Th by m. In this case, the reference signal is quickly synchronized with the input signal as m is large, and is slowly synchronized with the input signal as m is small (that is, the continuity of the reference signal is low as m is large, and the reference signal is small as m is small). Continuity increases).

The setting parameter 142 is a positive integer value (that is, a value of 1 to a) determined within a predetermined upper limit value a. The upper limit value a is a value determined so that the frequency stability of the reference signal immediately after the restoration of the GPS reception failure satisfies the frequency stability allowed by the external device using the reference signal. More specifically, the frequency stability of the reference signal when a holdover occurs is maintained at the worst because the reference signal generator 100 uses the standard radio wave. Therefore, when the holdover occurs, the reference signal is allowed by the external device after the GPS reception failure is recovered even if the reference signal is far from the GPS reception time because it is almost full of the upper limit of the frequency stability of the standard radio wave reception time. A limit value that smoothly changes so as to satisfy the frequency stability is the upper limit value a. For example, if the frequency stability of the standard radio wave is 1 × 10 ⁻¹¹ and the frequency stability allowed by the external device is 50 × 10 ⁻⁹ , the upper limit value a is 50 × 10 ⁻⁹ 1 × 10 It is 5000 divided by ^-11 . In this case, the setting parameter 142 is a value in the range of 1 to a = 1 to 5000.

  The PLL 150 synchronizes the phase of the output signal (“reference signal” shown in FIG. 1) with the input signal (“1 pps signal” and “pseudo 1 pps signal” shown in FIG. 1) to change the accuracy of the output signal to that of the input signal. And includes a phase comparator 151, a loop filter 152, a VCO (Voltage Controlled Oscillator) 153, and a frequency dividing circuit 154.

  The phase comparator 151 includes a processor, a time interval counter, and the like. The phase comparator 151 compares the “input signal” from the GPS receiver 120 or the time information comparator 130 with the “1 Hz signal” from the frequency dividing circuit 154, and compares them. The phase difference of the signal is output to the loop filter 152 as a “phase difference signal”. Here, the “1 Hz signal” refers to a signal every second (that is, 1 Hz) generated by dividing a 10 MHz reference signal. The phase comparator 151 compares the 1 pps signal with the 1 Hz signal to generate a phase difference signal when the holdover does not occur, and generates the phase difference signal with the pseudo 1 pps signal and 1 Hz when the holdover occurs. The signal is compared to generate a phase difference signal. Further, the phase comparator 151 has a timer (not shown) inside, and measures the time from when the holdover occurs until it recovers.

  The loop filter 152 is composed of a low-pass filter or the like, and removes an unnecessary short-cycle signal from the phase difference signal and converts it into a clean DC signal with few AC components. The converted signal is output to the VCO 153 as a “control signal” for controlling the VCO 153.

  The VCO 153 is composed of a voltage controlled oscillator incorporating a crystal oscillator or the like. The VCO 153 can control the transmission frequency according to the magnitude of the input voltage, and generates a 10 MHz reference signal based on the control signal input from the loop filter 152.

  The frequency dividing circuit 154 includes a flip-flop and the like, and divides a 10 MHz reference signal to generate a 1 Hz signal synchronized with the reference signal. The generated 1 Hz signal is output to the phase comparator 151.

  Next, the operation of the reference signal generator 100 having such a configuration will be described. First, the operation when no GPS reception failure has occurred will be described.

  When receiving a GPS signal from a GPS satellite, the GPS receiver 120 extracts a GPS reception time from the GPS signal and transmits the GPS reception time to the time information comparator 130. Further, the GPS receiver 120 generates a 1 pps signal based on the GPS signal and outputs it to the phase comparator 151.

  When the phase comparator 151 receives the 1 pps signal, the phase comparator 151 generates a “phase difference signal” from the phase difference between the 1 pps signal and the 1 Hz signal from the frequency dividing circuit 154, and outputs it to the loop filter 152.

  When the loop filter 152 receives the phase difference signal, the loop filter 152 removes an unnecessary short-cycle signal from the phase difference signal, generates a “control signal”, and outputs it to the VCO 153.

  When the VCO 153 receives the control signal from the loop filter 152, the VCO 153 generates a 10 MHz reference signal by raising or lowering the output frequency of the built-in crystal oscillator based on the control signal, and outputs the reference signal to an external device.

  The frequency dividing circuit 154 divides the reference signal generated by the VCO 153 to generate a 1 Hz signal and feeds it back to the phase comparator 151. The phase comparator 151 again compares the 1 Hz signal with the 1 pps signal.

  The PLL 150 (the phase comparator 151, the loop filter 152, the VCO 153, and the frequency dividing circuit 154) repeats these operations and continues to generate a highly accurate 10 MHz reference signal.

  When the standard radio wave receiver 110 receives the standard radio wave transmitted from the standard frequency time signal station, the standard radio wave receiver 110 extracts the standard radio wave reception time from the standard radio wave and transmits it to the time information comparator 130.

  When receiving the standard radio wave reception time tS from the standard radio wave receiver 110, the time information comparator 130 compares these with the GPS reception time tG received from the GPS receiver 120, and calculates these time differences ΔT. Then, the calculated time difference ΔT is stored in the time difference database 141 in association with the current date and time.

  Specifically, as shown in FIG. 2, the time information comparator 130 calculates the time difference ΔT between the standard radio wave reception time tS and the GPS reception time tG once every minute. Then, the time information comparator 130 stores the time difference ΔT in the time difference database 141 as “time-varying characteristic information” in association with the current month, day, hour, and minute. When this time-dependent change characteristic information is plotted in a table with the time difference ΔT on the vertical axis and the time t on the horizontal axis, for example, FIG. 3 is obtained. Note that the time information comparator 130 stores the time difference ΔT for the most recent year in the time difference database 141. The time difference ΔT after one year has been deleted as needed.

  In addition, when the time information comparator 130 stores the time difference ΔT for one hour, that is, 60 time differences ΔT continuously in the time difference database 141, the time information comparator 130 calculates an average value ΔTh of the 60 time differences ΔT. The average value ΔTh is stored in the time difference database 141 as “time-varying characteristic information” in association with the current month, day, and time. FIG. 4 shows, for example, plots of this daily change characteristic information in a table with the vertical axis representing time average ΔTh and the horizontal axis representing time. Note that the time information comparator 130 stores the time average ΔTh for the most recent year in the time difference database 141. The time average ΔTh after one year has been deleted as needed.

  Further, when the time information comparator 130 stores the time average ΔTh for one day, that is, 24 time averages ΔTh continuously in the time difference database 141, the time information comparator 130 calculates the average value ΔTd of the 24 ΔThs, The average value ΔTd is stored in the time difference database 141 as “aging characteristic information” in association with the current month, day, and time. When this aging characteristic information is plotted in a table, for example, FIG. 5 is obtained. Note that the time information comparator 130 stores the daily average ΔTh for the most recent year in the time difference database 141. The time average ΔTh after one year has been deleted as needed.

Further, the time information comparator 130 obtains information corresponding to the current date and time, that is, the same month, same day, same time of the previous year, time difference ΔT, time average ΔTh, and daily average ΔTd from the time difference database 141, and Based on the value, a correction amount ΔTc that satisfies the following (formula 1) is calculated. Here, A1, A2, and A3 are predetermined constants.
ΔTc = (A1ΔT + A2ΔTh + A3ΔTd) / 3 (Equation 1)

Furthermore, the time information comparator 130 generates a pseudo GPS reception time that satisfies the following (Equation 2). Here, tP is the generation time of the pseudo GPS reception time, and tS is the reception time of the standard radio wave time.
tP = tS−ΔTc (2)

  Since the standard radio wave reception time is output every minute, the pseudo GPS reception time is also output every minute. Therefore, the time information comparator 130 divides the pseudo GPS reception time into signals per second and generates a pseudo 1 pps signal. The time information comparator 130 outputs the generated pseudo 1 pps signal to the phase comparator 151.

  Next, the operation when a GPS reception failure occurs will be described.

  When the GPS receiver 120 becomes unable to receive a GPS signal from a GPS satellite, the GPS receiver 120 stops outputting the GPS reception time and the 1 pps signal.

  When the phase comparator 151 cannot receive a 1 pps signal from the GPS receiver 120, the phase comparator 151 starts counting an internal timer and measures an input signal for phase comparison in order to measure the time during which the holdover occurs. Is switched from a 1 pps signal to a pseudo 1 pps signal. The phase difference between the pseudo 1 pps signal and the 1 Hz signal is output to the loop filter 152 as a “phase difference signal”. The other operations are the same as the operations when no GPS reception failure has occurred, and thus description thereof is omitted.

  Finally, the operation when the GPS receiver 120 recovers from a GPS reception failure will be described.

  When the GPS receiver 120 is ready to receive a GPS signal from a GPS satellite, it resumes the GPS reception time and the output of the 1 pps signal.

When the phase comparator 151 receives the 1 pps signal from the GPS receiver 120, the phase comparator 151 immediately stops counting the internal timer and acquires the timer value as the holdover time Th ("holdover time" shown in FIG. 6). Then, the phase comparator 151 calculates a time synchronization time Ty (“time synchronization time” shown in FIG. 6) that satisfies the following (Equation 3) based on the holdover time Th and the value m of the setting parameter 142. Note that m is a positive integer value of 1 to a.
Ty = Th / m (3)

The phase comparator 151 calculates the pulse number n of the 1 pps signal until the reference signal is synchronized with the 1 pps signal (for example, the time synchronization time Ty is calculated by dividing the pulse interval of the 1 pps signal by 1 second). Furthermore, the phase comparator 151 acquires the phase difference (ΔTd shown in FIG. 6) between the 1 Hz signal and the 1 pps signal synchronized with the reference signal, for example, using a built-in time interval counter (not shown). Then, based on the phase difference ΔTd and the number of pulses n, a correction amount that satisfies the following (Equation 4) (ΔTe shown in FIG. 7: a correction amount for correcting the reference signal per pulse of 1 pps signal) is acquired.
ΔTe = ΔdT / n (4)

  As shown in FIG. 7, the phase comparator 151 synchronizes the reference signal with the signal obtained by adding / subtracting ΔTd to the 1 pps signal to the signal obtained by subtracting / adding ΔTe for each pulse, thereby generating a time synchronization time. Apply Ty (ie, n pulses) and gradually synchronize the reference signal with the 1 pps signal.

  According to the present embodiment, the time-dependent deviation between the GPS reception time and the standard radio wave reception time in the last year (that is, the seasonal trend in the last year at the place where the reference signal generator 100 is installed, the trend of day and night) The time information comparator 130 corrects the “pseudo GPS reception time very close to the GPS reception time even when the GPS reception time cannot be obtained from the GPS receiver 120. Can be obtained. As a result, the time information comparator 130 can generate a “pseudo 1 pps signal” that is very close to the “1 pps signal”, so that the reference signal generator 100 uses the pseudo 1 pps signal even if a holdover occurs. A reference signal having the characteristics can be generated.

  In addition, since the pseudo GPS reception time is generated based on the standard radio wave reception time, the frequency stability of the reference signal generated by the reference signal generator 100 during the holdover occurrence is, at worst, the frequency stability of the standard radio wave. It can be the same level. In addition, since the standard radio wave reception time is corrected based on the chronological deviation over the last year, the reference signal generator 100 has a frequency stability higher than the frequency stability of the standard radio wave even if a holdover occurs. The reference signal can be generated.

  Moreover, since the reference signal generator 100 gradually shortens the phase difference between the reference signal and the 1 pps signal over the time synchronization time when the GPS reception failure is recovered, the reference signal after the GPS reception failure is recovered. Signal continuity can be increased.

  Further, since the reference signal generator 100 stores the setting parameter 142 for determining the length of the time synchronization time, the value of the setting parameter 142 can be changed in accordance with the frequency stability allowed by the external device. Thus, the length of the time synchronization time can be easily adjusted.

  The time information comparator 130 calculates the time difference ΔT by comparing the GPS reception time and the standard radio wave reception time every minute, but the standard radio wave reception time can be output from the standard radio wave receiver 110 at a shorter interval. Thus, the time difference ΔT may be calculated at shorter time intervals. The time information comparator 130 may calculate the time difference ΔT at a longer time interval.

  Further, in this embodiment, the daily average ΔTd, time average ΔTh, and time difference ΔT for one year are stored in the time difference database 141, and the time difference ΔT and its calculation date and time are calculated without calculating the daily average ΔTd and time average ΔTh. And may be stored in the time difference database. In this case, the time information comparator 130 may acquire the time difference ΔT corresponding to the current date and time from the time difference database, and correct the standard radio wave reception time with the acquired time difference ΔT.

  The time difference database 141 may store a daily average ΔTd, a time average ΔTh, and a time difference ΔT for a plurality of years. In this case, the time information comparator 130 may calculate the correction amount ΔTc based on the daily average ΔTd, time average ΔTh, and time difference ΔT for a plurality of years corresponding to the current time.

  Further, the time difference database 141 is generated by another device installed in advance at the installation location of the reference signal generator 100, and the time difference database 141 is stored in the storage unit 140 when the reference signal generator 100 is installed. May be. The reference signal generator 100 can generate a pseudo GPS reception time immediately after installation based on the time-dependent change in the GPS reception time and the standard radio wave reception time at the installation location.

  Further, an external interface such as a USB port may be provided so that the time difference database 141 and the setting parameter 142 can be stored from the outside.

  The PLL 150 may be a digital PLL in which the phase comparator 151, the frequency dividing circuit 154, etc. are configured by a digital processor or the like, or an analog PLL in which the phase comparator 151, the frequency dividing circuit 154, etc. are configured by an analog circuit. There may be.

  Further, the VCO 153 includes an OCVCXO (even-controlled voltage-controlled crystal oscillator), and a TCVCXO (temperature-compensated voltage-controlled crystal oscillator). It may be.

  A part or all of the above embodiments can be described as in the following supplementary notes, but is not limited thereto.

(Appendix 1)
GPS reception time acquisition means for acquiring GPS reception time based on the GPS signal;
Standard radio wave reception time acquisition means for acquiring the standard radio wave reception time based on the standard radio wave,
Storage means for storing time difference information associated with the time difference between the GPS reception time and the standard radio wave reception time with the received month, day, or time;
Correction means for acquiring a time difference corresponding to the current month, day, or time from the time difference information, and correcting the standard radio wave time based on the acquired time difference;
It has an oscillator that outputs a reference signal, and when no GPS reception failure has occurred, the reference signal is synchronized with an input signal generated based on the GPS signal, and corrected when a GPS reception failure has occurred Phase synchronization means for synchronizing the reference signal to the input signal generated based on the standard radio wave reception time,
The phase synchronization means divides the phase difference between the input signal generated based on the GPS signal and the reference signal into a plurality of pulses and gradually shortens when the GPS reception failure is recovered,
A reference signal generator.

(Appendix 2)
Measuring means for measuring a reception failure time from the occurrence of a GPS reception failure until recovery from the GPS reception failure,
The phase synchronization means includes
Based on the reception failure time, comprising a calculation means for calculating a synchronization time from the recovery of the GPS reception failure until the reference signal is synchronized with the input signal,
When recovering from a GPS reception failure, gradually reduce the phase difference between the reference signal and the input signal over the synchronization time,
The reference signal generator according to appendix 1, wherein:

(Appendix 3)
Setting value storage means for storing a setting value indicating the amount of time from when the GPS reception failure is recovered until the reference signal is synchronized with the input signal;
The calculating means calculates the synchronization time by dividing the reception failure time by the set value;
The reference signal generator according to appendix 2, characterized in that:

(Appendix 4)
The set value is a value having an upper limit value,
The upper limit value is a value calculated based on the frequency stability of the standard radio wave and the frequency stability allowed by an external device using the reference signal.
The reference signal generating device according to appendix 3, wherein

(Appendix 5)
A GPS reception time acquisition step of acquiring a GPS reception time based on the GPS signal;
A standard radio wave reception time acquisition step for acquiring a standard radio wave reception time based on the standard radio wave;
Storing a time difference between the GPS reception time and the standard radio wave reception time, the time difference information associated with the received month, day, or time;
A correction step of acquiring a time difference corresponding to the current month, day, or time from the time difference information and correcting the standard radio wave time based on the acquired time difference;
When a GPS reception failure has not occurred, the reference signal output from the oscillator is synchronized with the input signal generated based on the GPS signal, and when a GPS reception failure has occurred, the corrected standard radio wave reception time is set. The reference signal output from the oscillator is synchronized with the input signal generated based on the reference signal, and further, when the GPS reception failure is recovered, the phase difference between the input signal generated based on the GPS signal and the reference signal is A phase synchronization step that divides into multiple pulses and gradually shortens,
A method for generating a reference signal.

DESCRIPTION OF SYMBOLS 100 Reference signal generator 110 Standard radio wave receiver 120 GPS receiver 130 Time information comparator 140 Memory | storage part 141 Time difference database 142 Setting parameter 150 PLL
151 Phase comparator 152 Loop filter 153 VCO
154 Frequency divider

Claims (5)

GPS reception time acquisition means for acquiring GPS reception time based on the GPS signal;
Standard radio wave reception time acquisition means for acquiring the standard radio wave reception time based on the standard radio wave,
Storage means for storing time difference information associated with the time difference between the GPS reception time and the standard radio wave reception time with the received month, day, or time;
Correction means for acquiring a time difference corresponding to the current month, day, or time from the time difference information, and correcting the standard radio wave time based on the acquired time difference;
It has an oscillator that outputs a reference signal, and when no GPS reception failure has occurred, the reference signal is synchronized with an input signal generated based on the GPS signal, and corrected when a GPS reception failure has occurred Phase synchronization means for synchronizing the reference signal to the input signal generated based on the standard radio wave reception time,
The phase synchronization means divides the phase difference between the input signal generated based on the GPS signal and the reference signal into a plurality of pulses and gradually shortens when the GPS reception failure is recovered,
A reference signal generator. Measuring means for measuring a reception failure time from the occurrence of a GPS reception failure until recovery from the GPS reception failure,
The phase synchronization means includes
Based on the reception failure time, comprising a calculation means for calculating a synchronization time from the recovery of the GPS reception failure until the reference signal is synchronized with the input signal,
When recovering from a GPS reception failure, gradually reduce the phase difference between the reference signal and the input signal over the synchronization time,
The reference signal generator according to claim 1. Setting value storage means for storing a setting value indicating the amount of time from when the GPS reception failure is recovered until the reference signal is synchronized with the input signal;
The calculating means calculates the synchronization time by dividing the reception failure time by the set value;
The reference signal generator according to claim 2. The set value is a value having an upper limit value,
The upper limit value is a value calculated based on the frequency stability of the standard radio wave and the frequency stability allowed by an external device using the reference signal.
The reference signal generator according to claim 3. A GPS reception time acquisition step of acquiring a GPS reception time based on the GPS signal;
A standard radio wave reception time acquisition step for acquiring a standard radio wave reception time based on the standard radio wave;
Storing a time difference between the GPS reception time and the standard radio wave reception time, the time difference information associated with the received month, day, or time;
A correction step of acquiring a time difference corresponding to the current month, day, or time from the time difference information and correcting the standard radio wave time based on the acquired time difference;
When a GPS reception failure has not occurred, the reference signal output from the oscillator is synchronized with the input signal generated based on the GPS signal, and when a GPS reception failure has occurred, the corrected standard radio wave reception time is set. The reference signal output from the oscillator is synchronized with the input signal generated based on the reference signal, and further, when the GPS reception failure is recovered, the phase difference between the input signal generated based on the GPS signal and the reference signal is A phase synchronization step that divides into multiple pulses and gradually shortens,
A method for generating a reference signal.

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