JP2016119540A - Reference signal generation device and reference signal generation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reference signal generation device capable of maintaining accuracy of a reference signal even if a frequency of an oscillator generating a clock signal temporarily shifts.SOLUTION: A reference signal generation device 1 includes a temperature compensated oscillator 11, a positioning operation part 15, a voltage controlled oscillator 23, a phase comparing part 21, and a control part 22. The positioning operation part 15 detects clock drift representing a frequency variation of a clock signal, by performing a positioning operation based on a GNSS signal. The phase comparing part 21 compares the clock signal and a reference signal outputted by the voltage controlled oscillator 23. The control part 22 controls the voltage controlled oscillator 23 based on a comparison result from the phase comparing part 21, if a variation of a clock drift detected by the positioning operation part 15 does not exceed a threshold value, and controls the voltage controlled oscillator 23 so as to make influence of the comparison result become small, if the variation of the clock drift exceeds the threshold value.SELECTED DRAWING: Figure 1

Description

  The present invention mainly relates to a reference signal generator for supplying a reference signal to the outside.

  Conventionally, reference signal generators have been installed in wireless communication facilities such as mobile phone base stations and digital broadcast transmission stations. The reference signal generator outputs a reference signal with very accurate frequency and timing based on the signal acquired from the GNSS satellite. In the wireless communication facility, based on the reference signal, the timing for transmitting the signal is determined and the frequency of the signal is synchronized.

  The GPS receiver of Patent Document 1 includes a reference frequency source and a frequency synthesizer. The frequency synthesizer generates a local signal for down-converting the RF signal acquired from the GPS antenna and a clock signal based on the signal generated by the reference frequency source. The GPS receiver performs a positioning operation based on the down-converted RF signal and clock signal, and generates a reference signal (1PPS signal).

  The reference signal generator of Patent Document 2 includes a phase comparator, a voltage controlled oscillator, and a loop filter. The phase comparator compares the reference signal generated by the GPS receiver with the reference signal output by the voltage controlled oscillator and outputs a phase difference. The loop filter controls the voltage controlled oscillator based on the phase difference output from the phase comparator. Thereby, an accurate reference signal can be output to the outside.

JP 2011-247637 A JP 2010-88071 A

  Here, when a crack is generated in an impurity (flux or the like) contained in the solder that solders the voltage controlled oscillator to the substrate, the oscillation frequency of the voltage controlled oscillator may change abruptly due to the effect ( Hereinafter, it is referred to as generation of piezoelectric noise. In addition, the oscillation frequency of the voltage controlled oscillator may change abruptly due to vibration or a rapid temperature change. When such piezoelectric noise, vibration, or rapid temperature change occurs, it is conceivable that the frequency of the clock signal output from the reference frequency source of Patent Document 1 is temporarily shifted. When the frequency of the clock signal is deviated, processing using this clock signal cannot be performed properly, and therefore an accurate reference signal is not output. As a result, the phase difference output from the phase comparator increases. However, since the phase difference generated here is due to a temporary malfunction of the reference frequency source, the frequency of the reference signal is set by controlling the voltage controlled oscillator so as to reduce this phase difference. Deviation from the value.

  The present invention has been made in view of the above circumstances, and its main object is to generate a reference signal generator capable of maintaining the accuracy of a reference signal even when the frequency of an oscillator that generates a clock signal is temporarily shifted. Is to provide.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to a first aspect of the present invention, a reference signal generator having the following configuration is provided. That is, the reference signal generation device includes a clock signal oscillation unit, a positioning calculation unit, a signal correction unit, a reference signal oscillation unit, a comparison unit, and a control unit. The clock signal oscillating unit oscillates a clock signal or a signal for generating the clock signal. The positioning calculation unit detects a clock drift indicating a frequency variation of the clock signal by performing a positioning calculation based on the GNSS signal. The signal correction unit corrects the clock signal based on the clock drift detected by the positioning calculation unit. The reference signal oscillating unit oscillates a reference signal output to the outside. The comparison unit compares the corrected clock signal with the reference signal output from the reference signal oscillation unit. The control unit controls the reference signal oscillating unit based on a comparison result of the comparison unit when the change amount of the clock drift detected by the positioning calculation unit does not exceed a threshold value, and changes the clock drift. When the amount exceeds the threshold, the reference signal oscillating unit is controlled so that the comparison result has less influence on the control than when the amount of change in the clock drift does not exceed the threshold.

  As a result, even when the frequency of the clock signal is temporarily shifted due to piezoelectric noise, vibration, rapid temperature change, etc., the control unit controls the reference signal oscillation unit so that the influence of the comparison result of the comparison unit is reduced. Therefore, the accuracy of the reference signal can be maintained.

  In the reference signal generation device, it is preferable that the control unit controls the reference signal oscillation unit without using the comparison result when the change amount of the clock drift exceeds a threshold value.

  Thereby, since the comparison result is not taken into consideration at all, it is possible to almost eliminate the influence of the frequency shift of the clock signal on the reference signal.

  In the reference signal generator, when the amount of change in the clock drift exceeds a threshold value, the control unit is configured to reduce the influence of the comparison result as the amount of change in the clock drift increases. It is preferable to control the signal oscillation unit.

  As a result, the greater the amount of change in the clock drift, the higher the possibility that the clock signal is temporarily shifted, and the greater the influence of controlling the reference signal oscillation unit so that the phase difference or frequency difference becomes smaller. While it is possible to appropriately prevent the temporary disturbance, it is possible to consider the influence of the phase difference or the frequency difference to some extent when it is difficult to determine whether the disturbance is temporary.

  In the reference signal generation device, the control unit is configured to compare the clock drift when the clock drift change amount does not exceed the threshold value after a predetermined time has elapsed after the clock drift change amount exceeds the threshold value. It is preferable to control the reference signal oscillation unit based on the result.

  As a result, the control based on the comparison result can be automatically restarted after the temporary deviation of the frequency of the clock signal is settled.

  According to a second aspect of the present invention, a reference signal generator having the following configuration is provided. That is, the reference signal generator includes a reference signal oscillation unit, a comparison unit, and a control unit. The reference signal oscillating unit oscillates a reference signal output to the outside. The comparison unit compares the clock signal acquired from the outside with the reference signal output from the reference signal oscillation unit. The control unit acquires a clock drift indicating a frequency variation of the clock signal, and controls the reference signal oscillation unit based on a comparison result of the comparison unit when the amount of change in the clock drift does not exceed a threshold value When the clock drift change amount exceeds a threshold value, the reference signal oscillating unit is less affected by the comparison result on the control than when the clock drift change amount does not exceed the threshold value. To control.

  As a result, even when the frequency of the clock signal is temporarily shifted due to piezoelectric noise, vibration, rapid temperature change, etc., the control unit controls the reference signal oscillation unit so that the influence of the comparison result of the comparison unit is reduced. Therefore, the accuracy of the reference signal can be maintained.

  According to a third aspect of the present invention, a reference signal generator having the following configuration is provided. That is, the reference signal generation device includes a clock signal oscillation unit, a positioning calculation unit, a signal correction unit, a reference signal oscillation unit, a comparison unit, and a control unit. The clock signal oscillating unit oscillates a clock signal or a signal for generating the clock signal. The positioning calculation unit detects a clock drift indicating a frequency variation of the clock signal by performing a positioning calculation based on the GNSS signal. The signal correction unit corrects the clock signal based on the clock drift detected by the positioning calculation unit. The reference signal oscillating unit oscillates a reference signal output to the outside. The comparison unit compares the corrected clock signal with the reference signal output from the reference signal oscillation unit. The control unit controls the reference signal oscillation unit based on the comparison result of the comparison unit, and when the GNSS satellite cannot be detected, the comparison result has a small influence on the control of the reference signal oscillation unit. The reference signal oscillating unit is controlled as follows.

  In general, since GNSS satellites transmit GNSS signals in a specific (specific) frequency band for each satellite, when the frequency of the signal oscillated by the clock signal oscillation unit is suddenly shifted, the GNSS satellite detects it suddenly. It becomes impossible. Therefore, the accuracy of the reference signal can be maintained by the GNSS satellite detecting the shift of the clock signal based on the detection result and reducing the influence of the comparison result of the comparison unit.

  In the reference signal generation device, the control unit is influenced by the comparison result based on whether or not the GNSS antenna functions normally and whether or not the GNSS satellites cannot be detected simultaneously. It is preferable to control the reference signal oscillating unit so as to be small.

  As a result, when the GNSS signal cannot be acquired due to a disconnection of the GNSS antenna or the GNSS satellite cannot be detected due to the movement of the satellite, the frequency of the clock signal is not necessarily abnormal. By performing control based on the comparison result, the accuracy of the reference signal can be maintained.

  According to a fourth aspect of the present invention, the following reference signal generation method is provided. That is, the reference signal generation method includes a clock signal oscillation process, a positioning calculation process, a signal correction process, a reference signal oscillation process, a comparison process, and a control process. In the clock signal oscillation step, a clock signal or a signal for generating the clock signal is oscillated. In the positioning calculation step, a clock drift indicating a frequency variation of the clock signal is detected by performing a positioning calculation based on the GNSS signal. In the signal correction step, the clock signal is corrected based on the clock drift detected in the positioning calculation step. In the reference signal oscillation step, the reference signal oscillation unit is controlled to oscillate a reference signal output to the outside. In the comparison step, the corrected clock signal is compared with the reference signal output in the reference signal oscillation step. In the control step, when the change amount of the clock drift detected in the positioning calculation step does not exceed a threshold value, the reference signal oscillation unit is controlled based on the comparison result in the comparison step, and the clock drift When the change amount exceeds the threshold value, the reference signal oscillating unit is controlled so that the comparison result has less influence on the control than when the clock drift change amount does not exceed the threshold value.

  As a result, even when the frequency of the clock signal is temporarily shifted due to piezoelectric noise, vibration, rapid temperature change, etc., the control unit controls the reference signal oscillation unit so that the influence of the comparison result of the comparison unit is reduced. Therefore, the accuracy of the reference signal can be maintained.

The block diagram which shows the structure of the reference signal generator which concerns on 1st Embodiment. The graph which shows the time change of a phase difference and a clock drift. The flowchart which shows the process which determines whether the control which considered the phase difference is performed. The graph which shows transition of the variation | change_quantity of a clock drift, and a threshold value. The flowchart which shows the process which determines whether the control which considered the phase difference based on a modification is performed. The flowchart which shows the process which determines whether the control which considered the phase difference based on 2nd Embodiment is performed.

  Next, a first embodiment of the present invention will be described with reference to the drawings. The reference signal generator 1 of the first embodiment is installed in a wireless communication facility such as a mobile phone base station or a terrestrial digital broadcast transmitter station.

  The GNSS antenna 2 is connected to the input unit 41 of the reference signal generator 1. The GNSS antenna 2 receives a positioning signal from a GNSS satellite (GPS satellite or the like), and outputs the positioning signal to the reference signal generator 1. The reference signal generator 1 generates a reference signal (a reference frequency signal, a reference timing signal, etc.) based on the positioning signal. The reference signal is output to each device of the wireless communication facility.

  The reference signal generator 1 includes a GNSS reception block 10 and a reference signal generation block 20. Note that the GNSS reception block 10 and the reference signal generation block 20 may be disposed inside the same housing, or may be disposed in separate housings and physically separated. When arranged in a separate housing, the GNSS receiving block 10 can be referred to as a GNSS receiver, and the reference signal generating block 20 can be referred to as a reference signal generating device.

  The GNSS receiving block 10 includes a temperature compensated oscillator (TCXO, clock signal oscillation unit) 11, a synthesizer 12, a down converter unit 13, a baseband processing unit 14, a positioning calculation unit 15, a signal correction unit 16, Is provided.

  The temperature compensated oscillator 11 is an oscillator that uses a crystal resonator as a resonator. The temperature compensated oscillator 11 generates a signal having a preset frequency and outputs the signal to the synthesizer 12.

  The synthesizer 12 generates a demodulation signal and a clock signal based on the signal generated by the temperature compensated oscillator 11. The synthesizer 12 outputs a demodulation signal to the down converter unit 13 and outputs a clock signal to the down converter unit 13, the baseband processing unit 14, the positioning calculation unit 15, and the signal correction unit 16.

  The down converter unit 13 receives a positioning signal from the GNSS antenna 2 and a demodulation signal from the synthesizer 12. The down-converter unit 13 down-converts the positioning signal using the demodulation signal and converts it into an IF signal. The down converter unit 13 outputs the IF signal to the baseband processing unit 14.

  The baseband processing unit 14 demodulates the IF signal using the clock signal output from the synthesizer 12 as a sampling frequency and converts it to a baseband signal. The baseband processing unit 14 outputs a baseband signal to the positioning calculation unit 15.

  The positioning calculation unit 15 reads the navigation message based on the baseband signal input from the baseband processing unit 14 to obtain the orbit of the satellite, and knows the position of the own aircraft and the error of the clock on the own aircraft side. Calculate with the method. The positioning calculation unit 15 can obtain an accurate time synchronized with a high-precision clock mounted on the GNSS satellite by this positioning calculation. In addition, the positioning calculation unit 15 calculates a clock offset (timing error) and a clock drift (frequency fluctuation) of the clock signal by performing a positioning calculation. The positioning calculation unit 15 outputs the timing error and the clock drift to the signal correction unit 16 and further outputs the clock drift to the control unit 22 (details will be described later).

  The signal correction unit 16 corrects the clock signal based on the clock offset and clock drift input from the positioning calculation unit 15. Specifically, the signal correcting unit 16 corrects the rising timing of the clock signal based on the timing error and corrects the frequency based on the clock drift. The signal correction unit 16 has a function of a frequency divider, and generates a 1 PPS signal by dividing the corrected clock signal. A frequency divider may be provided separately from the signal correction unit 16. The signal correction unit 16 outputs a 1PPS signal obtained by correcting and dividing the clock signal to the reference signal generation block 20.

  The reference signal generation block 20 includes a phase comparison unit (comparison unit) 21, a control unit 22, a voltage controlled oscillator (reference signal oscillation unit) 23, and a frequency division unit 24.

  The voltage controlled oscillator 23 is a VCXO that uses a crystal resonator as a resonator, and is configured such that the output frequency can be changed according to the level of the control voltage applied from the outside. The reference frequency signal output from the voltage controlled oscillator 23 is output from the output unit 42 to an external system.

  The frequency divider 24 divides the reference frequency signal input from the voltage controlled oscillator 23 and converts the reference frequency signal from a high frequency to a low frequency and outputs it to the phase comparator 21. The reference frequency signal converted to a low frequency is output from the output unit 43 to the outside as a reference timing signal (1PPS signal). In the following description, the reference frequency signal and the reference timing signal are collectively referred to as a reference signal.

  The phase comparison unit 21 compares the reference timing signal output from the frequency division unit 24 and the 1PPS signal output from the signal correction unit 16 to calculate a phase difference. The phase difference calculated by the phase comparison unit 21 is output to the control unit 22.

  Based on the phase difference input from the phase comparison unit 21, the control unit 22 controls the voltage controlled oscillator 23 by determining a control voltage so that the phase difference approaches zero. As a result, the reference signal of the reference signal generator 1 can be maintained with high accuracy even if the characteristics of the voltage controlled oscillator 23 fluctuate due to changes over time or ambient temperature. As described above, the clock drift is input from the positioning calculation unit 15 to the control unit 22. The control unit 22 controls the voltage controlled oscillator 23 based on this clock drift (details will be described later).

  Next, a case where the frequency of the clock signal output from the temperature compensated oscillator 11 is temporarily shifted greatly due to piezoelectric noise, vibration, or a sudden temperature change will be described with reference to FIGS.

  FIG. 2 is a graph showing temporal changes of the phase difference output from the phase comparison unit and the clock drift calculated by the positioning calculation unit. This graph is data obtained using the reference signal generator in an environment where the ambient temperature is rapidly increased or decreased. As shown in FIG. 2, the clock drift changes rapidly before and after time T1. Considering that the number of satellites acquired by the reference signal generator before and after time T1 is sufficient, a rapid change in clock drift occurs due to piezoelectric noise, vibration, or a rapid temperature change. This is considered to be a temporary error. Note that the rapid deterioration of the frequency of the clock signal occurs at the timing when the ambient temperature is lowered.

  Further, it can be seen from the graph of FIG. 2 that the phase difference changes (deteriorates) abruptly at substantially the same timing as the clock drift changes abruptly. This is presumably because the count of each part of the reference signal generation block 20 is disturbed due to a sudden change in the frequency of the clock signal. When the phase difference increases, the voltage controlled oscillator is controlled to reduce this phase difference. However, this phase difference is a phase difference caused by a temporary malfunction of the temperature compensated oscillator. Therefore, by controlling the voltage controlled oscillator so that this phase difference is close to zero, the frequency of the reference frequency signal is deviated from the set value.

  Thereafter, when the temporary frequency shift of the temperature compensated oscillator is recovered, the frequency of the reference frequency signal is controlled to approach the set value. However, since the frequency of the reference frequency signal cannot be changed rapidly, it takes a little time for the frequency of the reference frequency signal to approach the set value. As described above, the conventional control cannot appropriately cope with the temporary frequency deviation of the temperature compensated oscillator.

  In this regard, the control unit 22 of the present embodiment can cope with a temporary frequency shift of the temperature compensated oscillator 11 by performing the control shown in the flowchart of FIG. This will be specifically described below. Note that the processing shown in FIG. 3 and the subsequent flowcharts is an example, and addition, deletion, order change, and the like of the processing can be appropriately performed.

  The control unit 22 acquires the clock drift from the positioning calculation unit 15 (S101). The control unit 22 calculates the obtained amount of change in clock drift (S102). Specifically, the change amount of the clock drift is calculated by obtaining the difference between the clock drift acquired most recently and the clock drift acquired this time. When the clock drift increases, the change amount becomes positive, and when the clock drift decreases, the change amount becomes negative. Note that the method of calculating the amount of change in clock drift is arbitrary, and may be determined in consideration of not only the most recently acquired clock drift but also the previously acquired clock drift.

  Next, the control unit 22 determines whether or not the absolute value of the change amount calculated in S102 exceeds a threshold value (S103). Here, the graph of FIG. 4 is a graph showing the amount of change in clock drift and the threshold value under the conditions of FIG. In the reference signal generator 1, a positive threshold value and a negative threshold value are set, and the control unit 22 determines that “the threshold value is not exceeded” when the amount of change in the clock drift is between the positive threshold value and the positive threshold value. If it is greater than the threshold or less than the negative threshold, it is determined that “the threshold has been exceeded”. As shown in FIG. 4, immediately after time T1, the amount of change in clock drift exceeds the threshold value.

  When the control unit 22 determines that the amount of change in the clock drift exceeds the threshold, the control of the voltage controlled oscillator 23 considering the phase difference detected by the phase comparison unit 21 is temporarily interrupted to fix the control voltage ( S104). This is because if the amount of change in clock drift exceeds the threshold value, it is considered that a phase difference is caused due to a temporary malfunction of the temperature compensated oscillator 11. By performing the process of S104, it is possible to prevent the frequency of the reference frequency signal from deviating from the set value.

  Next, when it is determined that the predetermined time (about several seconds) has elapsed since the process of S104 (S105), the control unit 22 determines again whether or not the amount of change in the clock drift exceeds the threshold (S106). Here, when the change amount of the clock drift does not exceed the threshold value, it is determined that the temperature compensated oscillator 11 has returned to normal, and the control of the voltage controlled oscillator 23 in consideration of the phase difference is resumed (S107).

  By repeating the above processing, even if the frequency of the clock signal generated by the temperature compensated oscillator 11 is temporarily shifted, the frequency shift of the reference frequency signal can be prevented. Therefore, when the control according to the present embodiment is performed under the conditions shown in FIG. 2, the control considering the phase difference is interrupted before and after the time T1, so the frequency of the reference frequency signal does not change. Can be prevented from deviating from the set value.

  Next, a modification of the first embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing the control performed by the control unit 22 of this modification. Note that the processes other than S204 and S207 in FIG. 5 are the same as those in the flowchart shown in FIG.

  In the above embodiment, when the amount of change in the clock drift exceeds the threshold value, the voltage controlled oscillator 23 is controlled without considering the phase difference at all (in other words, the influence of the phase difference on the control becomes zero). In this regard, the control unit 22 of this modification controls the voltage controlled oscillator 23 so that the influence of the phase difference is reduced as the amount of change in clock drift increases. As a method of adjusting the influence of the phase difference, for example, there is a method of changing the multiplier of the control unit 22 (loop filter).

  Here, when the amount of change in the clock drift is large, the frequency output from the temperature compensated oscillator 11 is changing abruptly, so there is a high possibility that the frequency is temporarily disturbed. Therefore, by performing the control as in the present modification, the influence of the phase difference can be considered to some extent when it is difficult to determine whether the disturbance is temporary while appropriately preventing the temporary disturbance.

  As described above, the reference signal generator 1 according to the first embodiment includes the temperature compensation oscillator 11, the positioning calculation unit 15, the signal correction unit 16, the voltage control oscillator 23, the phase comparison unit 21, And a control unit 22. The temperature compensated oscillator 11 oscillates a signal for generating a clock signal. The positioning calculation unit 15 detects a clock drift indicating a frequency variation of the clock signal by performing a positioning calculation based on the GNSS signal. The signal correction unit 16 corrects the clock signal based on the clock drift detected by the positioning calculation unit 15. The voltage controlled oscillator 23 oscillates a reference signal output to the outside. The phase comparison unit 21 compares the corrected clock signal with the reference signal output from the voltage controlled oscillator 23. When the change amount of the clock drift detected by the positioning calculation unit 15 does not exceed the threshold value, the control unit 22 controls the voltage controlled oscillator 23 based on the comparison result of the phase comparison unit 21, and the change amount of the clock drift is When the threshold value is exceeded, the voltage controlled oscillator 23 is controlled so that the comparison result has less influence on the control than when the clock drift change amount does not exceed the threshold value.

  As a result, even when the frequency of the clock signal is temporarily shifted due to piezoelectric noise, vibration, sudden temperature change, or the like, the control unit 22 is set to voltage so that the influence of the comparison result of the phase comparison unit 21 is reduced. Since the control oscillator 23 is controlled, the accuracy of the reference signal can be maintained.

  Next, a second embodiment will be described with reference to FIG. In the first embodiment, the clock drift is used to detect that the frequency of the signal output from the temperature compensated oscillator 11 is temporarily shifted greatly. In contrast, in the second embodiment, this frequency shift is detected based on whether or not a GNSS satellite has been detected (searched).

  Specifically, a specific frequency band is used for each GNSS satellite, and the GNSS satellite is detected by generating a corresponding frequency band on the receiver side. Therefore, when the frequency of the clock signal is temporarily shifted due to piezoelectric noise, vibration, rapid temperature change, or the like, different frequency bands are generated even if a constant frequency band is intended to be generated. As a result, the GNSS satellite cannot be detected. As other factors that make it impossible to detect the GNSS satellite, it is conceivable that the GNSS antenna 2 is disconnected or the GNSS satellite moves due to the passage of time.

  Hereinafter, the control performed in the second embodiment will be described with reference to the flowchart of FIG. The reference signal generator 1 determines whether or not the GNSS satellites can no longer be detected all at once (S301). When the GNSS satellite moves over time, the GNSS satellite cannot be detected little by little. For this reason, when the GNSS satellites cannot be detected all at once, it is considered that the frequency of the signal output from the temperature compensated oscillator 11 has temporarily shifted greatly or the GNSS antenna 2 has been disconnected.

  When the GNSS satellites cannot be detected all at once, the reference signal generator 1 determines whether or not the connection state of the GNSS antenna 2 is normal (S302). This determination can be made using the antenna detection function. The antenna detection function is a function of detecting whether or not the GNSS antenna is connected with reference to the antenna current. Note that the processing of S302 may determine not only the connection state of the GNSS antenna 2 but also whether the GNSS antenna 2 itself is normal.

  Here, when the connection state of the GNSS antenna is normal, it is considered that the frequency of the signal output from the temperature compensated oscillator 11 has temporarily shifted greatly. Therefore, in this case, the control of the voltage controlled oscillator 23 in consideration of the phase difference is interrupted as in the first embodiment (S303). Thereafter, when it is determined that a predetermined time has elapsed (S304), the reference signal generator 1 determines whether or not a plurality of GNSS satellites have been detected (S305). If a plurality of GNSS satellites can be detected, it is considered that the signal output from the temperature compensated oscillator 11 has returned to normal, so the control of the voltage controlled oscillator 23 in consideration of the phase difference is resumed (S306).

  Although it has been described that the GNSS satellites cannot be detected all at once in step S301, it is considered an abnormal situation when the number of detected GNSS satellites gradually decreases and the GNSS satellites cannot be detected. It is also considered appropriate to perform the process of interrupting the control of the voltage controlled oscillator 23 in consideration of the phase difference (S303). Therefore, the limitation of “all at once” may be removed from step S301.

  Similarly, in step S302, if the connection state of the GNSS antenna 2 is not normal, it is considered an abnormal situation. In this case, the process of interrupting the control of the voltage controlled oscillator 23 in consideration of the phase difference (S303) may be performed. It is considered reasonable. Therefore, the process of step S302 may be omitted.

  The preferred embodiments and modifications of the present invention have been described above, but the above configuration can be modified as follows, for example.

  In the above embodiment, whether or not the phase difference can be used is determined based on the amount of change in the clock drift, but whether or not the phase difference can be used is determined based on an equivalent parameter (such as a second-order differential of the clock bias). good.

  In the above embodiment, the phase comparison unit 21 that compares the phases of the two signals is used. However, a frequency comparison unit that compares the frequencies of the two signals may be provided instead of the phase comparison unit 21.

  In the above embodiment, the temperature compensated oscillator 11 is used as the clock signal oscillating unit and the voltage controlled oscillator 23 is used as the reference signal oscillating unit. However, other oscillators may be used. For example, OCXO (a crystal oscillator with a thermostatic bath), an atomic oscillator other than a crystal (such as a rubidium oscillator), an LC oscillator composed of a coil and a capacitor, or the like can be used.

  Each unit included in the reference signal generating device 1 can be configured as software instead of hardware.

DESCRIPTION OF SYMBOLS 1 Reference signal generator 10 GNSS receiving block 11 Temperature compensation type | mold oscillator (clock signal oscillation part)
DESCRIPTION OF SYMBOLS 12 Synthesizer 13 Down converter part 14 Baseband process part 15 Positioning calculation part 16 Signal correction part 20 Reference signal generation block 21 Phase comparison part (comparison part)
22 control unit 23 voltage controlled oscillator (reference signal oscillation unit)
24 divider

Claims (8)

A clock signal oscillator for oscillating a clock signal or a signal for generating the clock signal;
A positioning calculation unit that detects a clock drift indicating a frequency variation of the clock signal by performing a positioning calculation based on a GNSS signal;
A signal correction unit for correcting the clock signal based on the clock drift detected by the positioning calculation unit;
A reference signal oscillator for oscillating a reference signal output to the outside;
A comparison unit that compares the corrected clock signal with the reference signal output from the reference signal oscillation unit;
When the change amount of the clock drift detected by the positioning calculation unit does not exceed the threshold value, the reference signal oscillation unit is controlled based on the comparison result of the comparison unit, and the change amount of the clock drift exceeds the threshold value A control unit that controls the reference signal oscillation unit so that the influence of the comparison result on the control is smaller than when the amount of change in the clock drift does not exceed a threshold value,
A reference signal generation device comprising: The reference signal generator according to claim 1,
The control unit controls the reference signal oscillation unit without using the comparison result when the change amount of the clock drift exceeds a threshold value. The reference signal generator according to claim 1,
When the amount of change in the clock drift exceeds a threshold, the control unit controls the reference signal oscillation unit so that the influence of the comparison result decreases as the amount of change in the clock drift increases. Reference signal generator. The reference signal generator according to any one of claims 1 to 3,
When the clock drift change amount does not exceed the threshold value after a predetermined time has elapsed since the clock drift change amount becomes equal to or greater than the threshold value, the control unit determines the reference signal oscillation unit based on the comparison result. And a reference signal generator. A reference signal oscillator for oscillating a reference signal output to the outside;
A comparison unit that compares a clock signal acquired from the outside and the reference signal output by the reference signal oscillation unit;
When the clock drift indicating the frequency variation of the clock signal is acquired and the amount of change in the clock drift does not exceed a threshold, the reference signal oscillation unit is controlled based on the comparison result of the comparison unit, and the clock drift The control unit that controls the reference signal oscillation unit so that the influence of the comparison result on the control is less when the change amount of the clock drift exceeds the threshold value than when the change amount of the clock drift does not exceed the threshold value When,
A reference signal generation device comprising: A clock signal oscillator for oscillating a clock signal or a signal for generating the clock signal;
A positioning calculation unit that detects a clock drift indicating a frequency variation of the clock signal by performing a positioning calculation based on a GNSS signal;
A signal correction unit for correcting the clock signal based on the clock drift detected by the positioning calculation unit;
A reference signal oscillator for oscillating a reference signal output to the outside;
A comparison unit that compares the corrected clock signal with the reference signal output from the reference signal oscillation unit;
The reference signal oscillation unit is controlled based on the comparison result of the comparison unit, and when the GNSS satellite cannot be detected, the reference result is reduced so that the influence of the comparison result on the control of the reference signal oscillation unit is reduced. A control unit for controlling the signal oscillation unit;
A reference signal generation device comprising: The reference signal generator according to claim 6, wherein
The control unit is configured to reduce the influence of the comparison result based on whether the GNSS satellites cannot be detected all at once and whether the GNSS antenna functions normally. And a reference signal generator. A clock signal oscillation step of oscillating a clock signal or a signal for generating the clock signal;
A positioning calculation step of detecting a clock drift indicating a frequency variation of the clock signal by performing a positioning calculation based on a GNSS signal;
A signal correction step of correcting the clock signal based on the clock drift detected in the positioning calculation step;
A reference signal oscillation process for controlling the reference signal oscillation unit to oscillate a reference signal output to the outside;
A comparison step of comparing the corrected clock signal with the reference signal output in the reference signal oscillation step;
When the change amount of the clock drift detected in the positioning calculation step does not exceed a threshold value, the reference signal oscillation unit is controlled based on the comparison result in the comparison step, and the change amount of the clock drift exceeds the threshold value. If exceeded, a control step of controlling the reference signal oscillation unit so that the influence of the comparison result on the control is less than when the amount of change in the clock drift does not exceed a threshold;
A method for generating a reference signal, comprising:

Images