CN115047748A - Time service device and method based on satellite navigation signals - Google Patents
Time service device and method based on satellite navigation signals Download PDFInfo
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- CN115047748A CN115047748A CN202210521896.2A CN202210521896A CN115047748A CN 115047748 A CN115047748 A CN 115047748A CN 202210521896 A CN202210521896 A CN 202210521896A CN 115047748 A CN115047748 A CN 115047748A
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- G04—HOROLOGY
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- G04R20/00—Setting the time according to the time information carried or implied by the radio signal
- G04R20/02—Setting the time according to the time information carried or implied by the radio signal the radio signal being sent by a satellite, e.g. GPS
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Abstract
The invention discloses a time service device and a time service method based on satellite navigation signals, wherein the device comprises a local reference source, a signal receiving and source difference measuring module, a controllable frequency division module, a parameter generating module and a controllable time delay module, wherein the signal receiving and source difference measuring module receives satellite navigation signals and carries out source difference measurement on the local reference signals to obtain the source difference value of the local reference signals; the local reference signal is also input into the controllable frequency division module to generate a main clock, the parameter generation module utilizes the source difference value of the local reference signal to generate an output frequency adjustment value, frequency division is carried out on the main clock to generate a pulse per second signal, and then the pulse per second signal is input into the controllable delay module to obtain controllable pulse per second output relative to satellite time calibration. The invention improves the metering accuracy of local second time by introducing the satellite navigation signal, and has the advantages of low realization cost, wide application range and the like under the same measuring precision.
Description
Technical Field
The invention belongs to the technical field of time-frequency testing, and particularly relates to a time service device and method based on satellite navigation signals.
Background
In the prior art, when a time-frequency signal is generated by using a satellite navigation signal, an independent satellite time service module is generally used for receiving the satellite navigation signal, measuring the deviation of a local reference frequency, adjusting the local reference frequency to enable the output reference frequency to be accurate, outputting a pulse per second signal, and simultaneously recording the adjustment information of a local reference source to discipline the local reference source.
Here, since the independent satellite timing module is not the same source as the local reference source, i.e., different references are usedThe source is mainly because the satellite time service module uses an independent reference source carried by the satellite time service module. The measurement portion for performing frequency difference measurement on the frequency difference between the local reference signal and the satellite navigation signal is heterogeneous with the adjustment portion for adjusting the local reference frequency. When time service output is carried out based on the principle, the generated second timing has larger quantization error, the precision is not high and can only reach 10 -8 To 10 -9 Is limited, as well as phase regulation of the occurrence of the pulse per second, there is a phase deviation of the pulse per second.
Disclosure of Invention
The invention mainly solves the technical problems of providing a time service device and a time service method based on satellite navigation signals, and solving the problems of different time-frequency measurement sources, low time service second pulse precision and limited phase deviation regulation in the prior art.
In order to solve the technical problems, the invention adopts a technical scheme that: the time service device based on the satellite navigation signal comprises a local reference source, a local frequency multiplier, a signal receiving and source difference measuring module, a controllable frequency dividing module, a parameter generating module and a controllable time delay module, wherein the local reference source outputs a local reference signal, the local reference signal is subjected to frequency multiplication by the local frequency multiplier and then is input to the signal receiving and source difference measuring module, the signal receiving and source difference measuring module receives the satellite navigation signal, source difference measurement is carried out on the local reference signal, a source difference value of the local reference signal is obtained, and then the source difference value is output to the parameter generating module; the local reference signal is further input to the controllable frequency division module as a main clock after being frequency-multiplied by the local frequency multiplier, the parameter generation module generates an output frequency adjustment value, the main clock is frequency-divided to generate a pulse per second signal, and the pulse per second signal is input to the controllable delay module to obtain a controllable pulse per second output which is calibrated relative to satellite time.
Preferably, the signal receiving and source difference measuring module includes a frequency conversion sub-module, a demodulation sub-module and a source difference calculating module, and the frequency conversion sub-module is based on the actual frequency value f of the local reference signal 0 ', actual frequency value f of frequency multiplied local carrier signal c '＝Mf 0 ', wherein M denotes a frequency multiplier, for an incoming satellite navigation signal f sz Performing down-conversion processing to obtain a low-intermediate frequency signal, inputting the low-intermediate frequency signal into a demodulation submodule, and outputting a carrier frequency difference delta f by the frequency conversion submodule c ', the demodulation sub-module performs carrier loop tracking demodulation by using the local carrier signal to obtain demodulation information, and the demodulation sub-module further outputs a tracking frequency difference Δ f c ", the carrier frequency difference and the tracking frequency difference are added by Δ f c '+Δf c ”＝f c '-f sz And then the source difference value of the local reference signal is calculated by a source difference calculating module
Wherein, f 0 Nominal frequency, f, of a local reference source 0 '＝f c '/M＝(Δf c '+Δf c ”+f sz )/M。
Preferably, the controllable frequency dividing module includes a first adder and a delay register, the frequency adjustment value from the parameter generating module is input to the first adder, and is periodically accumulated with an accumulated value stored in the delay register, and after the accumulated value is accumulated to a second period, the first adder updates the input frequency adjustment value and continues accumulating, the first adder is further cascaded with an edge detector for detecting edge transition of an output waveform, and the edge detector outputs the pulse per second signal.
Preferably, the controllable frequency division module further includes a second adder in cascade between the first adder and the edge detector, and the second adder receives the phase adjustment value output from the signal receiving and measuring module, and outputs the pulse-per-second signal after adding the result output by the first adder and performing edge detection by the edge detector.
Preferably, the parameter generation module obtains a source difference σ of the local reference signal s Actual frequency value f 'of local reference signal' 0 ＝f 0 (σ s +1), K times to obtain the actual frequency of the master clock Kf' 0 When it comes toGenerating a period of T x The corresponding obtained frequency adjustment value is 2 N /Kf′ 0 T x And N represents the word length of the phase accumulator of the DDS.
Preferably, the controllable frequency division module outputs the local pulse per second and the phase difference to the controllable delay module, and the controllable delay module uses the phase difference to delay and regulate the local pulse per second to be consistent with the satellite time and output.
Based on the same conception, the invention also provides a time service method based on the satellite navigation signal, which comprises the following steps: measuring and receiving, namely receiving a satellite navigation signal, and performing source difference measurement on the local reference signal by using the satellite navigation signal to obtain a source difference value of the local reference signal; controllable frequency division, wherein the frequency is adjusted by utilizing the source difference value of the local reference signal, and local pulse per second is generated through the controllable frequency division; and (4) time delay calibration, namely performing time delay regulation on the local pulse per second to obtain controllable pulse per second output relative to satellite time calibration.
Preferably, in the measurement receiving step, the method for performing source difference measurement on the local reference signal by using the satellite navigation signal includes:
the method comprises the steps of carrying out frequency multiplication on a local reference signal to obtain a local carrier signal, utilizing the local carrier signal to demodulate and receive the satellite navigation signal, obtaining the actual frequency difference between the local carrier signal and the satellite navigation signal in real time, utilizing the actual frequency of the satellite navigation signal and the actual frequency difference to calculate the actual frequency of the local carrier signal, further obtaining the actual frequency of the local reference signal, and utilizing the actual frequency and the nominal frequency of the local reference signal to calculate the source difference value of the local reference signal.
Preferably, in the controllable frequency dividing step, the source difference σ of the local reference signal s Actual frequency value f 'of local reference signal' 0 ＝f 0 (σ s +1), K times to obtain the actual frequency of the master clock Kf' 0 When a period T is generated x The corresponding frequency adjustment value is obtained as2 N /Kf′ 0 T x And N represents the word length of the phase accumulator of the DDS. Preferably, in the step of calibrating the delay, the phase difference between the local pulse per second and the satellite time is measured, and then the phase difference is used to regulate the local pulse per second to be consistent with the satellite time in a delay manner and output the consistent time.
The invention has the beneficial effects that: the invention discloses a time service device and a time service method based on satellite navigation signals, wherein the device comprises a local reference source, a signal receiving and source difference measuring module, a controllable frequency division module, a parameter generating module and a controllable time delay module, wherein the signal receiving and source difference measuring module receives satellite navigation signals and carries out source difference measurement on the local reference signals to obtain source difference values of the source difference value local reference signals; the local reference signal is also input into the controllable frequency division module to generate a main clock, the parameter generation module utilizes the source difference value of the local reference signal to generate an output frequency adjustment value, the main clock is subjected to frequency division to generate a pulse per second signal, and then the pulse per second signal is input into the controllable delay module to obtain controllable pulse per second output relative to satellite time calibration. The invention improves the metering accuracy of local second time by introducing the satellite navigation signal, and has the advantages of low realization cost, wide application range and the like under the same measuring precision.
Drawings
FIG. 1 is a schematic diagram illustrating an embodiment of a time service apparatus based on satellite navigation signals according to the present invention;
FIG. 2 is a schematic diagram illustrating a signal receiving and source difference measuring module in another embodiment of the time service apparatus according to the invention;
FIG. 3 is a schematic diagram illustrating a controllable frequency division module in another embodiment of the time service apparatus according to the present invention;
FIG. 4 is a schematic waveform diagram illustrating the generation of a controllable frequency division module in another embodiment of the time service apparatus based on satellite navigation signals according to the present invention;
FIG. 5 is a schematic timing diagram illustrating second time calibration in another embodiment of the time service apparatus according to the invention based on satellite navigation signals;
FIG. 6 is a schematic diagram of a controllable delay timing sequence in another embodiment of the time service apparatus based on satellite navigation signals according to the present invention;
FIG. 7 is a flowchart illustrating a time service method based on satellite navigation signals according to an embodiment of the present invention.
Detailed Description
In order to facilitate an understanding of the invention, reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It is to be noted that, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The embodiments will be described in detail below with reference to the accompanying drawings.
Fig. 1 is a schematic composition diagram of an embodiment of a time service device based on satellite navigation signals. As can be seen from fig. 1, the time service device based on the satellite navigation signal includes a local reference source 11, a signal receiving and source difference measuring module 12, a controllable frequency dividing module 14, a parameter generating module 13, and a controllable delay module 15, where the local reference source 11 outputs a local reference signal and inputs the local reference signal to the signal receiving and source difference measuring module 12, and the signal receiving and source difference measuring module 12 receives the satellite navigation signal, performs source difference measurement on the local reference signal to obtain a source difference value of the local reference signal, and outputs the source difference value to the parameter generating module 13;
the local reference signal is further input to the controllable frequency division module 14 to generate a master clock, the parameter generation module 13 generates an output frequency adjustment value, the master clock is subjected to frequency division to generate a pulse per second signal, and the pulse per second signal is input to the controllable delay module 15 to obtain a controllable pulse per second output calibrated relative to the satellite.
Preferably, in practical applications, the signal receiving and source difference measuring module 12 and the controllable frequency dividing module 14 may respectively include frequency multipliers, frequency multiplication of the local reference signal input by the local reference source 11 may be respectively implemented inside the signal receiving and source difference measuring module 12 and the controllable frequency dividing module 14, the frequency multiplication values may be different, and frequency synthesis may be performed based on the local reference signal to generate multiple required frequency components. However, these frequency components are all referenced to the local reference signal, and therefore have the same nature and the same frequency accuracy.
Preferably, for the signal receiving and source difference measuring module 12, it receives the satellite navigation signal through the satellite antenna, and performs down-conversion and demodulation on the satellite navigation signal to obtain the satellite navigation signal, and in the receiving process, the local reference signal output by the local reference source is used for down-conversion and demodulation, and the carrier loop tracking is performed. Therefore, the signal receiving and source difference measuring module 12 receives signals by using the local reference signal output by the local reference source 11 as a source signal, and the local reference source 11 also provides a signal source for the controllable frequency dividing module in the device, thereby ensuring that the local reference source 11 in the device is a uniform reference source and ensuring the homology of each module generating pulse per second.
With the popularization and use of the satellite navigation positioning modules and chips such as the GPS, the Beidou and the like, the satellite navigation positioning module has lower market price, and the cost of the signal receiving and source difference measuring module 12 can be obviously reduced. Meanwhile, the precision requirement on the local reference source for generating the local reference signal is not high, and only a constant-temperature crystal oscillator and a temperature compensation crystal oscillator are needed, and an atomic clock with higher price is not needed, so that the price can be reduced.
For the purposes of the present invention, the local reference source 11 includes a quartz crystal, a constant temperature crystal oscillator, a temperature compensated crystal oscillator, and other low-cost common reference sources, which may have aging and drift problems, that is, a problem of frequency change over time, or a problem of frequency stability, for example, the frequency stability of the quartz crystal may reach 10 -9 Day, even 10 -11 Day, for a 10MHz quartz crystal, the frequency will typically not vary by more than 0.1Hz within a day.The frequency stability of the quartz crystal is lower than that of the oven controlled crystal oscillator, which is indicated in that the frequency of the quartz crystal changes more or faster than that of the oven controlled crystal oscillator along with the time, so that for the problem of dynamic frequency change of the reference source, the actual frequency value needs to be accurately measured, and the dynamic and real-time performance of the measurement can be maintained.
The invention obtains accurate carrier frequency of satellite navigation signals by utilizing carrier demodulation and telegraph text ephemeris of received satellite navigation signals, and the accuracy of the carrier frequency is 10 -13 To 10 -14 Of the local reference signal, the source difference σ of the local reference signal being obtainable using the high-precision level of the measurement signal s Can reach 10 -11 To 10 -12 Of the order of magnitude of (d). Although the local reference sources have the problem of low frequency stability, and the frequencies of the reference sources drift along with the time, the method of the invention can measure the actual frequency with high precision, so as to obtain an actual frequency measurement value with very high precision, and the measurement has real-time property.
Preferably, referring to fig. 2, the signal receiving and source difference measuring module includes a frequency conversion sub-module 121 and a demodulation sub-module 122, the frequency conversion sub-module 121 performs frequency down-conversion processing on an input satellite navigation signal by using a local carrier signal that is frequency-multiplied based on the local reference signal, so as to obtain a low-intermediate frequency baseband signal, the low-intermediate frequency baseband signal is input to the demodulation sub-module 122, the frequency conversion sub-module 121 further outputs a carrier frequency difference, the demodulation sub-module 122 performs carrier loop tracking demodulation by using the local carrier signal, so as to obtain demodulation information, the demodulation sub-module 122 further outputs a tracking frequency difference, and the carrier frequency difference and the tracking frequency difference are added by an adder 123 and then calculated by a source difference calculating module 124, so as to obtain the source difference.
Preferably, the carrier is generally in the L band for satellite navigation signals, and the frequency conversion sub-module 121 receives the local reference signal f from the local reference source 11 0 ' (actual frequency value) and then frequency multiplication is carried out in the carrier signal to obtain a local carrier signal f c ' (actual frequency value), then there is f c '＝Mf 0 ', where M denotes the frequency multiplier, then with the carrier f of the satellite navigation signal sz Mixing is performed (note that here the carrier f of the satellite navigation signal sz Is an actual value, since the satellite navigation signal has very high accuracy, the frequency value is a high-accuracy frequency value, and can be accurately obtained through ephemeris and link calculation in the demodulation information, and also represents a true value of the carrier frequency of the satellite navigation signal). The obtained low-intermediate frequency baseband signal is output to the demodulation sub-module 122, and the frequency conversion sub-module 121 outputs a carrier f relative to the satellite navigation signal sz Carrier frequency difference Δ f of c ' corresponding to the coarse frequency difference, the demodulation sub-module 122 performs demodulation loop tracking processing on the input low-intermediate frequency baseband signal, and further obtains the tracking frequency difference Δ f between the local carrier signal and the satellite navigation signal carrier in real time c ", which corresponds to the fine frequency difference, and then the carrier frequency difference is added to the tracking frequency difference by Δ f by the adder 123 c '+Δf c ", which is equivalent to the addition of the coarse frequency difference and the fine frequency difference, so as to obtain the actual frequency difference Δ f of the local carrier signal relative to the carrier frequency of the satellite navigation signal c ＝f c '-f sz ＝Δf c '+Δf c ". Δ f herein c ' and Δ f c "can be positive or negative, depending on the actual deviation.
Further, for a local reference source, the frequency of the local reference signal that it actually outputs should be f 0 '＝f c '/M＝(Δf c '+Δf c ”+f sz ) If the source difference value of the local reference signal is/M, the source difference value of the local reference signal is
Wherein f is 0 Representing the nominal frequency of the local reference source. In fig. 2, the source difference σ of the local reference signal s The source difference calculating module 124 calculates and outputs the actual frequency difference output by the adder 123.
Further, the source difference σ s The output is updated at second intervals, so that the error adjustment can be carried out at second intervals when the second clock of the controllable frequency division module 14 is outputThus, it is possible to ensure that a high-precision second clock output can be obtained without long-time observation.
Further, the parameter generation module 13 in fig. 1 generates the source difference σ according to the source difference σ s The frequency adjustment value required for the controllable frequency division module 14 to output the pulse per second is generated. How to depend on the source difference σ is further explained below in conjunction with the composition of the controllable frequency-dividing module 14 s The control outputs pulses per second.
Referring to fig. 1, for the controllable frequency division module 14, the local reference signal is input to the controllable frequency division module and multiplied by the local frequency multiplier to be used as a main clock, and the second pulse output can be obtained by controlling the frequency division of the main clock, but since the accuracy and stability of the local reference signal need to be corrected according to the error of the satellite navigation signal, the error needs to be corrected according to the obtained source difference σ s The second pulse with high precision can be ensured to be output only by dynamically correcting the local reference signal.
Preferably, the controllable frequency divider module 14 uses a Direct Digital Synthesizer (DDS) as a core device, the DDS divides an input main clock to obtain a pulse per second, or the DDS accumulates at fixed phase intervals to obtain a period per second, and the phase intervals need to be adjusted according to an actual frequency of the local reference signal. For example, according to the foregoing, the nominal frequency of the local reference signal is f 0 Measured source difference σ s Then the actual frequency f 'of the local reference signal' 0 ＝f 0 (σ s +1), after the local multiplier, the multiplier value is K, and the actual frequency of the master clock is Kf' 0 When the actual frequency Kf 'of the master clock is used' 0 When frequency division is carried out, N represents the word length of a phase accumulator of the DDS, and the minimum phase interval is 2 pi/2 N For example, when a divide-by-two of the master clock is to be implemented, the frequency adjustment value is 2 N-1 The corresponding phase accumulation step is pi, and when the frequency division is performed on the master clock, the corresponding frequency adjustment value is 2 N-2 The corresponding phase accumulation step is pi/2, and so on.
Thus, when the exact actual frequency of the master clock, Kf ', is obtained' 0 Then, to generateOne period is T x The corresponding frequency adjustment value can be calculated to be 2 N /Kf′ 0 T x The corresponding phase accumulation step is 2 π/Kf' 0 T x 。
Therefore, with the master clock as the clock source, one step 2 is accumulated every master clock cycle N /Kf 0 (σ s +1), then via Kf 0 (σ s +1) master clocks can output one second pulse. But due to the actual frequency f 'of the local reference signal' 0 If there is a deviation, it is necessary to continuously perform a deviation measurement, that is, to output the source difference value σ once every second measurement s By continuously updating the source difference σ every second s To dynamically adjust the accumulated step interval 2 N /Kf 0 (σ s +1). The parameter generation module 13 in FIG. 1 is 2 N /Kf 0 (σ s +1) to the frequency adjustment value of the DDS in the controllable frequency divider module 14 and maintaining a high numerical accuracy, e.g. representing the frequency adjustment value by a binary number of 16 to 32 bits, 2 of which N /Kf 0 (σ s The value of N in +1) represents different numbers of binary bits.
In practical applications, there will be 2 N /Kf 0 (σ s +1) value is smaller, i.e. 2 N Has a limited value, and Kf 0 (σ s +1) is of a large value, in which case the output second pulse is not generated directly, but rather a periodic pulse with a short output period is generated, i.e. the aforementioned generation of one period T x The corresponding frequency adjustment value can be calculated to be 2 N /Kf′ 0 T x For example, FTF (Fundamental time frame) pulses of 10ms period, and then every 100 FTF pulses with a sequence number is selected as a pulse per second to be output.
Fig. 3 and 4 further show the internal components of the controllable frequency-dividing module 14 and the internal waveform generation schematic. Preferably, the controllable frequency dividing module includes a first adder 141 and a delay register 142, the frequency adjustment value from the parameter generating module is input to the first adder 141, and is periodically accumulated with the accumulated value stored in the delay register 142, and after the accumulation reaches a second period, the delay register 142 naturally overflows, then the first adder 141 updates the input frequency adjustment value and continues accumulation, the first adder 141 is further cascaded with an edge detector 144 for detecting edge transition of the output waveform, and the edge detector 144 outputs the second pulse signal.
Further preferably, the controllable frequency division module further includes a second adder 143 cascaded between the first adder 141 and the edge detector 144, and the second adder 143 receives the phase adjustment value output by the signal receiving and source difference measuring module, and outputs the pulse-per-second signal after performing edge detection by the edge detector after adding the phase adjustment value to the result output by the first adder 141.
Preferably, the frequency adjustment value from the parameter generation module is input to the first adder 141, and is continuously added and output with the value accumulated in the delay register 142 under the driving of the main clock. Normally, exactly one second pulse is output after accumulating for one second period, and then the accumulated value in the delay register 142 continues to perform periodic accumulation on the input frequency adjustment value. And in each second period, the source difference value sigma is measured due to the signal receiving and source difference in the source difference measuring module s The correction is continuously obtained, and accordingly, the frequency adjustment value can be subjected to error correction, so that the output pulse per second is more accurate. Therefore, the contradiction that the measuring time length and the measuring precision can not be reconciled in the prior art is overcome.
In fig. 4, a schematic diagram T141 of a waveform of the signal of the accumulated value output after passing through the first adder 141 is shown, and it can be seen that the waveform T141 is a triangular wave with an accumulated period, that is, a period of one second, and if the waveform T141 is directly subjected to edge detection by the following edge detector 144, a pulse-per-second signal can be output.
Further preferably, a second adder 143 is further provided after the first adder 141 in fig. 3, and the second adder 143 adds the accumulated value output by the first adder 141 to the phase adjustment value output by the signal receiving and source difference measuring module, so as to further correct the phase error of the pulse per second output. The phase adjustment value is obtained by detecting a phase jitter occurring when the source difference measurement is performed on the local reference signal and the satellite carrier signal, and correspondingly, a waveform T143 output after passing through the second adder 143 is shown in fig. 4, and it can be seen that the waveform T143 performs phase adjustment based on the waveform T141, and the phase of the waveform T143 is slightly advanced from the phase of the waveform T141. Further shown in fig. 4 is an edge-detected waveform T144 for waveform T143 after passing through edge detector 144. By adding the phase adjustment value, the phase of the output pulse per second can be further subjected to error correction, so that the problem of phase jitter occurring in a local reference signal can be eliminated, and the accuracy of the output pulse per second can be improved.
Preferably, when the controllable frequency division module is implemented specifically, the frequency adjustment value is used as a step size, the master clock is used for accumulating, the FTF pulse with a period of 10ms is generated by natural overflow, and then the FTF pulse is counted in a modulo 100 manner, that is, the FTF pulse is output cyclically with the number of 0-99, wherein the FTF pulse with the number of 0 is designated as the pulse corresponding to the second time. Thus, there are 100 FTF pulses between two consecutive second instants.
Preferably, the standard satellite time, that is, the TOD information and the satellite time in the navigation message, can be obtained by demodulating the ephemeris information in the satellite navigation signal, and then the difference between the local time and the satellite time, that is, the clock difference, is obtained when the local time beat signal generated by local recovery is used to receive the satellite recovered by the source difference measurement module. And inputting a phase adjustment value of the controllable frequency division module by taking the clock difference value as a basis until the clock difference value is close to 0, and considering that the phase synchronization of the local time and the satellite time is established.
Therefore, with reference to fig. 1 and 5, after the controllable frequency division module generates the FTF pulse according to the frequency adjustment value, the FTF pulse is fed back to the signal receiving and source difference measurement module, and the difference value between the local time and the satellite time, i.e. the clock difference value, is input to the controllable frequency division module as a phase adjustment value to regulate and control the output phase of the FTF pulse corresponding to the counted local second time, which is mainly generated based on that the FTF pulse is generated by pushing the DDS by the master clock, and the output time is the local master clock time, and when the DDS pulse lags behind the satellite time (the accuracy is 1 master clock cycle), the delay can be corrected by the mantissa of the DDS transition edge, that is, the mantissa of the DDS transition edge is subjected to phase regulation by modifying the value of the step length accumulated therein. The correction process of the local time with respect to the satellite time can be seen schematically by the illustration of fig. 5.
Therefore, the accuracy of the output pulse per second frequency (or period) is determined for the frequency adjustment value output by the parameter generation module; the time accuracy of outputting the pulse per second is determined by the phase adjustment value output by the signal receiving and source difference measuring module.
Furthermore, as shown in fig. 6, since the controllable frequency division module divides the frequency of the master clock to obtain the pulse per second, the minimum precision of the output of the pulse per second is determined by the length of one cycle of the master clock, and if the clock difference or the phase difference of the local pulse per second time relative to the satellite time is less than the period of one master clock, a barrier effect is generated and it is difficult to regulate and control the local pulse per second time to approach the satellite time, and the problem is solved by the controllable delay module correspondingly.
With reference to fig. 1 and 6, the PPS output by the controllable frequency division module is output by the FTF pulse period, and the phase difference output by the controllable frequency division module, which is the clock difference of local second time smaller than one master clock period relative to satellite time, is delayed by the controllable delay module, and then the delayed PPS output is output by the controllable delay module.
Based on the same conception, the invention also provides an embodiment of a time service method based on satellite navigation signals, and as can be seen from fig. 7, the time service method based on satellite navigation signals comprises the following steps:
step S1, measuring and receiving, receiving satellite navigation signals, and performing source difference measurement on the local reference signals by using the satellite navigation signals to obtain source difference values of the local reference signals;
step S2, controllable frequency division, frequency adjustment is carried out by using the source difference value of the local reference signal, and local pulse per second is generated by controllable frequency division;
and step S3, performing time delay calibration, namely performing time delay regulation on the local pulse per second to obtain controllable pulse per second output relative to satellite time calibration.
Preferably, in the measurement receiving of step S1, the method for performing source difference measurement on the local reference signal by using the satellite navigation signal includes:
the method comprises the steps of carrying out frequency multiplication on a local reference signal to obtain a local carrier signal, utilizing the local carrier signal to demodulate and receive the satellite navigation signal, obtaining the actual frequency difference between the local carrier signal and the satellite navigation signal in real time, utilizing the actual frequency of the satellite navigation signal and the actual frequency difference to calculate the actual frequency of the local carrier signal, further obtaining the actual frequency of the local reference signal, and utilizing the actual frequency and the nominal frequency of the local reference signal to calculate the source difference value of the local reference signal. Specifically, reference may be made to the foregoing description of the embodiment in fig. 2, which is not repeated herein.
Preferably, in the controllable frequency dividing step, the source difference σ of the local reference signal s Actual frequency value f 'of local reference signal' 0 ＝f 0 (σ s +1), K times to obtain the actual frequency of the master clock Kf' 0 When a period T is generated x The corresponding frequency adjustment value is 2 N /Kf′ 0 T x . Reference may be made to the foregoing description of the embodiments of fig. 3-4, which is not repeated herein.
Preferably, in the step of calibrating the delay, the phase difference between the local pulse per second and the satellite time is measured, and then the phase difference is used to regulate the local pulse per second to be consistent with the satellite time in a delay manner and output the consistent time. Reference may be made to the foregoing description of the embodiments of fig. 5 to 6, which is not repeated herein.
On the basis of the embodiment, the invention realizes accurate pulse per second output, greatly improves the accuracy of second period and second moment output, and can enable the accuracy and stability of second period output to reach 10 -12 Magnitude of the order。
Based on the description of the embodiment, the invention discloses a time service device and a method based on satellite navigation signals, the device comprises a local reference source, a signal receiving and source difference measuring module, a controllable frequency division module, a parameter generation module and a controllable delay module, wherein the signal receiving and source difference measuring module receives satellite navigation signals and carries out source difference measurement on the local reference signals to obtain source difference values of the local reference signals; the local reference signal is also input into the controllable frequency division module to generate a main clock, the parameter generation module utilizes the source difference value of the local reference signal to generate an output frequency adjustment value, frequency division is carried out on the main clock to generate a pulse per second signal, and then the pulse per second signal is input into the controllable delay module to obtain controllable pulse per second output relative to satellite time calibration. The invention improves the metering accuracy of local second time by introducing the satellite navigation signal, and has the advantages of low realization cost, wide application range and the like under the same measuring precision.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or applied directly or indirectly to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A time service device based on satellite navigation signals is characterized by comprising a local reference source, a signal receiving and source difference measuring module, a controllable frequency division module, a parameter generating module and a controllable time delay module, wherein the local reference source outputs local reference signals and inputs the local reference signals to the signal receiving and source difference measuring module;
the local reference signal is also input into the controllable frequency division module to generate a master clock, the parameter generation module generates an output frequency adjustment value, the master clock is subjected to frequency division to generate a second pulse signal, and the second pulse signal is input into the controllable delay module to obtain a controllable second pulse output relative to satellite time calibration.
2. The satellite navigation signal-based time service device of claim 1, wherein the signal receiving and source difference measuring module comprises a frequency conversion sub-module, a demodulation sub-module and a source difference calculating module, wherein the frequency conversion sub-module is based on an actual frequency value f of the local reference signal 0 ', actual frequency value f of frequency multiplied local carrier signal c '＝Mf 0 ', wherein M denotes a frequency multiplier, for an incoming satellite navigation signal f sz Performing down-conversion processing to obtain a low intermediate frequency signal, inputting the low intermediate frequency signal into a demodulation submodule, and outputting a carrier frequency difference delta f by the frequency conversion submodule c ', the demodulation sub-module performs carrier loop tracking demodulation by using the local carrier signal to obtain demodulation information, and the demodulation sub-module further outputs a tracking frequency difference Δ f c ", the carrier frequency difference and the tracking frequency difference are added by Δ f c '+Δf c ”＝f c '-f sz Then the source difference value of the local reference signal is calculated by a source difference calculating module
Wherein f is 0 Nominal frequency, f, of a local reference source 0 '＝f c '/M＝(Δf c '+Δf c ”+f sz )/M。
3. The satellite navigation signal-based time service device according to claim 2, wherein the controllable frequency division module includes a first adder and a delay register, the frequency adjustment value from the parameter generation module is input to the first adder, and is periodically accumulated with an accumulated value stored in the delay register, and after the accumulated value reaches one second period, the first adder updates the input frequency adjustment value and continues accumulation, the first adder is further cascaded with an edge detector for detecting edge transition of an output waveform, and the edge detector outputs the pulse-per-second signal.
4. The satellite navigation signal based time service device according to claim 3, wherein the controllable frequency division module further includes a second adder cascaded between the first adder and the edge detector, the second adder receives the phase adjustment value outputted from the signal receiving and measuring module, and outputs the second pulse signal after performing edge detection by the edge detector after adding the result outputted from the first adder.
5. The satellite navigation signal-based time service device according to claim 3, wherein the parameter generation module obtains a source difference value σ of the local reference signal s Actual frequency value f of the local reference signal 0 '＝f 0 (σ s +1), the actual frequency of the generated master clock after K frequency multiplication in the controllable frequency division module is Kf 0 ', when a period T is generated x The parameter generation module correspondingly calculates to obtain a frequency adjustment value of 2 N /Kf′ 0 T x And N represents the word length of the phase accumulator of the DDS.
6. The time service device based on the satellite navigation signal according to claim 5, wherein the controllable frequency division module outputs a local pulse per second and a phase difference to the controllable delay module, and the controllable delay module uses the phase difference to delay and regulate the local pulse per second to be consistent with the satellite time and output the same.
7. A time service method based on satellite navigation signals is characterized by comprising the following steps:
measuring and receiving, namely receiving a satellite navigation signal, and performing source difference measurement on the local reference signal by using the satellite navigation signal to obtain a source difference value of the local reference signal;
the controllable frequency division is used for adjusting the frequency by utilizing the source difference value of the local reference signal and generating local pulse per second through the controllable frequency division;
and (4) time delay calibration, namely performing time delay regulation on the local pulse per second to obtain controllable pulse per second output relative to satellite time calibration.
8. The satellite navigation signal-based timing method according to claim 7, wherein in the measurement receiving step, the method of performing source difference measurement on the local reference signal using the satellite navigation signal includes:
frequency multiplication is carried out on the local reference signal to obtain a local carrier signal,
demodulating and receiving the satellite navigation signal by using the local carrier signal to obtain the actual frequency difference between the local carrier signal and the satellite navigation signal in real time,
calculating to obtain the actual frequency of the local carrier signal by using the actual frequency of the satellite navigation signal and the actual frequency difference, further obtaining the actual frequency of the local reference signal,
and calculating to obtain a source difference value of the local reference signal by using the actual frequency and the nominal frequency of the local reference signal.
9. The satellite navigation signal-based time service method according to claim 8, wherein in the controllable frequency dividing step, a source difference σ of a local reference signal s Actual frequency value f 'of local reference signal' 0 ＝f 0 (σ s +1), K times to obtain the actual frequency of the master clock Kf' 0 When a period T is generated x The corresponding obtained frequency adjustment value is 2 N /Kf′ 0 T x And N represents the word length of the phase accumulator of the DDS.
10. The time service method based on the satellite navigation signal according to claim 9, wherein in the time delay calibration step, the phase difference of the local second pulse relative to the satellite time is measured, and then the local second pulse is controlled to be consistent with the satellite time in a time delay mode and output by utilizing the phase difference.
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