CN117130025A - On-orbit reference frequency stability estimation method for inter-satellite link system - Google Patents
On-orbit reference frequency stability estimation method for inter-satellite link system Download PDFInfo
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/40—Correcting position, velocity or attitude
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/25—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS
- G01S19/256—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS relating to timing, e.g. time of week, code phase, timing offset
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/35—Constructional details or hardware or software details of the signal processing chain
- G01S19/37—Hardware or software details of the signal processing chain
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- General Physics & Mathematics (AREA)
- Signal Processing (AREA)
- Position Fixing By Use Of Radio Waves (AREA)
Abstract
The application discloses a method for estimating the stability of an on-orbit reference frequency of an inter-satellite link system, which comprises the following steps: calculating a combined phase measurement Θ from the bidirectional phase measurement Θ (t) without time scale correction p (t); calculating the relative frequency error δf i ‑δf j The method comprises the steps of carrying out a first treatment on the surface of the Calculating relative frequency error sample valuesRepeating at nominal sampling frequency, sampling at equal sampling intervals, and calculating relative Allen varianceThe application is improved based on the calculation formula of the Arrhenius variance, and can accurately estimate the relative frequency between two stars of the inter-satellite linkStability, and further estimating single star frequency stability.
Description
Technical Field
The application belongs to the technical field of links between satellites, and particularly relates to post-processing of output data of a ranging and time-frequency transmission system, and stability of a satellite-borne reference frequency source is calculated.
Background
In applications in the fields of gravity measurement satellite micron-scale precision ranging systems (KBR), three-dimensional reconnaissance satellite inter-satellite link systems, beidou constellation inter-satellite link systems and other scientific measurement, a crystal oscillator (or atomic clock) is a key device of an inter-satellite link load system, is a time and frequency reference of signal processing equipment and even the whole load, and all measurement moments are referenced by the reference frequency output by a frequency source. The stability of the output frequency is changed due to the influence of various factors such as temperature, radiation, ageing of devices and the like in the on-orbit running process of the frequency source, so that the inter-satellite time-frequency synchronization and the accuracy of measured data are further influenced.
Based on engineering development of low tracking gravity measurement satellites in China, a KBR system under development uses an ultra-stable crystal oscillator USO, which is a time and frequency reference of a KBR and a GNSS receiver, and the frequency stability index directly determines the accuracy of inter-satellite ranging and speed measurement. Against the background of the application, no directly related patent is available at present, and the existing patent only covers related methods of ground direct test and ground indirect data analysis, and typical methods include the following:
(1) The application patent of China academy of sciences national time service center, namely a real-time frequency stability analysis method, provides a real-time frequency stability analysis method applied to a ground test environment, and sequentially judges coarse errors, records states, performs data fitting interpolation, adaptively determines sampling intervals and iterates data to finally obtain the frequency stability represented by the Allen variance. The application can realize the real-time analysis of the frequency stability, and simultaneously can output and display the analysis result in real time, thereby simplifying the work of users. The application also designs a data preprocessing method according to the characteristic of frequency stability analysis, enhances the fault tolerance of the system, and provides a solution for realizing frequency standard real-time stability analysis based on common equipment such as a frequency meter, a phase meter and the like with low cost.
(2) Jiang Handa discloses a signal frequency stability measuring method and device, belonging to the field of atomic frequency standard. The method comprises the following steps: measuring the output frequency of a measured frequency source and a compensation detection source simultaneously by adopting a first frequency measuring instrument; judging whether an abnormal jump point appears at the same time of the output frequency value of the frequency of the measured frequency source and the output frequency value of the compensation detection source; if abnormal jump points occur at the same time, deleting the abnormal jump points in the frequency measurement result of the measured frequency source; and calculating the frequency stability of the measured frequency source. The application judges whether the output frequency value in the frequency measurement result of the measured frequency source and the frequency measurement result of the compensation detection source simultaneously generates abnormal jump points, and when the abnormal jump points simultaneously generate, the abnormal jump points in the frequency measurement result of the measured frequency source are deleted; the workload is reduced, and the measurement accuracy of the frequency stability is improved.
(3) The application relates to a frequency stability measuring device, in particular to a frequency stability measuring device for measuring the frequency accuracy characteristics, the long-term stability characteristics of the frequency and the additional frequency instability of two port components such as an amplifier, a frequency multiplier and the like of a frequency source such as an atomic frequency standard, an internal crystal oscillator of electronic instrument equipment, a frequency synthesizer and the like. The measuring resolution of the device can reach 1E-14. The device based on the application can be further expanded into N channels (N is more than or equal to 2), so that (N+1) source synchronous tests to be tested are realized.
The analysis of the existing methods can summarize several disadvantages:
(1) No relevant method research is conducted for the application environment pertinence of satellite payloads on orbit.
(2) All data are obtained directly based on the actual measurement of the instrument, but are not obtained through the joint analysis of other related data, and are not suitable for on-orbit working conditions.
Disclosure of Invention
The application solves the technical problems that: the application starts from the principle of on-orbit satellite-to-satellite link bidirectional measurement and high-precision time difference correction, and further researches an indirect calculation method of the frequency stability of the frequency source. Based on the basic definition of the Allan variance, a formula for calculating the relative frequency error by the inter-satellite measurement value is given, and a relative Allan variance mathematical model is further established.
The technical scheme of the application is as follows:
an on-orbit reference frequency stability estimation method of an inter-satellite link system comprises the following steps:
1) Obtaining a bi-directional phase measurement Θ (t) without time scale correction;
2) Obtaining two-way phase measurements Θ (t) unified to the instant of iStar i )；
3) Calculating a combined phase measurement Θ from the bidirectional phase measurement Θ (t) without time scale correction p (t)；
4) The two-way phase measurement value Θ (t) obtained according to step 2) and unified to the instant of i stars i ) And the combined phase measurement Θ obtained in step 3) p (t) calculating the relative frequency error δf i -δf j ；
5) The relative frequency error δf obtained according to step 4) i -δf j Calculating a relative frequency error sample value
6) Repeating the steps 1) to 5) according to the nominal sampling frequency to obtain a relative frequency error sampling value corresponding to each frequency pointSampling value of relative frequency error corresponding to each obtained frequency point +.>Sampling at equal sampling intervals and calculating the relative Allen variance sigma y (τ)。
Preferably, the method for obtaining the bidirectional phase measurement Θ (t) without time-scale correction is specifically:
wherein,
f i the output frequency of the i star; f (f) j The output frequency of j stars;
propagation time for a signal to be transmitted from i star to j star;
propagation time for a signal to be transmitted from j to i;
δf i deviation of the output frequency of the i star from the nominal frequency; the nominal frequency is the theoretical frequency of the satellite-borne system receiving and transmitting signals;
δf j deviation of the output frequency of j stars from the nominal frequency;
Δt i the time difference between the i star measurement time and the nominal time is the time difference between the i star measurement time and the nominal time;
Δt j the time difference between the moment of measurement for j stars and the nominal moment.
Preferably, a bi-directional phase measurement Θ (t) unified to the instant of the i star is obtained i ) The method of (1) comprises the following steps:
preferably, the combined phase measurement Θ is calculated p The method of (t) is specifically as follows:
Θ p (t)＝Θ(t)+(f i -f j )(Δt i -Δt j )。
preferably, the relative frequency error δf is calculated i -δf j The method of (1) comprises the following steps:
preferably, the relative frequency error sample values are calculatedThe method of (1) comprises the following steps:
preferably, the relative Allen variance σ is calculated y The method of (tau) is specifically:
where k represents a sampling number, η represents a sampling interval, and N is a positive integer not less than 100.
Preferably, the nominal sampling frequency is 1Hz.
Preferably, the sampling interval η=10 R The method comprises the steps of carrying out a first treatment on the surface of the Wherein R is a positive integer and R is 0,4]。
Compared with the prior art, the application has the advantages that:
1) The method is based on the improvement of the computing formula of the Arrhenius variance, has simple mathematical model and low operation complexity, and is suitable for operation of an on-orbit embedded system.
2) The method can accurately estimate the relative frequency stability between two stars of the inter-satellite link to a certain extent, further estimate the single-satellite frequency stability, and has the condition of on-orbit real-time monitoring.
3) The method can be used for estimating the star carrier frequency source for any inter-satellite link system which has a measurement link between two satellites and can output a distance measurement value, and has wide adaptability.
Drawings
FIG. 1 is a flow chart of the method of the present application.
Detailed Description
In order to assist ground data processing, load performance evaluation, abnormal problem analysis and other purposes, the requirement of monitoring the frequency stability of the on-orbit frequency source in real time is provided, and a specific estimation algorithm is researched.
The application relates to a method for estimating the stability of an on-orbit reference frequency of an inter-satellite link system, which is shown in figure 1 and comprises the following steps:
1 inter-satellite link direct measurement
In general, signals transmitted by the inter-satellite link system are designed to be different frequency points. Two satellites participating in the network are respectively numbered i and j, and the transmitting frequencies of the satellites are respectively f i And f j Denoted by f i ≠f j . The dual star receives the rf signal and independently measures the rf signal carrier phase, and the bi-directional phase measurement Θ (t) is based on a combination of two independent measurements, where Θ (t) can be expressed as:
wherein,
f i : output frequency of i star; f (f) j : output frequency of j star; the frequency in the embodiment of the application is as follows: f (f) i ＝32.703GHz，f j ＝32.702GHz；
j stars are transmitted to i stars, and carrier phases are measured by the i stars;
Δt i : i time difference of star measurement time relative to nominal time;
the i star transmits to the j star, and the carrier phase obtained by the measurement of the j star;
Δt j : j time difference of star measurement time relative to nominal time;
signal emission from i starGiving the propagation time of j stars;
propagation time of signal transmitted from j-star to i-star;
δf i : i deviation of the output frequency of the star from the nominal frequency;
δf j : deviation of the output frequency of j stars from the nominal frequency;
e: the sum of the system measurement errors can be set to zero.
Accordingly, at the nominal time t, the double star distance measurement R (t) is obtained as:
R(t)＝λΘ(t)， λ＝c/(f i +f j ) (2)
wherein:
lambda: two-way combination of equivalent wavelengths;
c is the speed of light under vacuum: nominal under vacuum is 299792458 (m/s).
2 measurement based on double star time scale correction
Based on time difference information generated by inter-satellite measurement, i.e. Δt in equation (1) i -Δt j (inter-satellite link internal time difference measurement value), the local measurement data time scale of the satellite j is precisely adjusted, so that the time scale of the double satellites is unified to the measurement time of the i satellite, and then the measurement values of the i and j are recombined, so that the bidirectional phase measurement value theta (t) unified to the time of the i satellite can be obtained i ) (i.e., standard corrected bi-directional phase measurement):
3 relative frequency error estimation
Equation (3) minus equation (1), neglecting small amounts, yields:
Θ(t i )-Θ(t)＝(f i -f j )(Δt i -Δt j )+(δf i -δf j )(Δt i -Δt j ) (4)
defining the combined phase measurement Θ p (t), direct calculation:
Θ p (t)＝Θ(t)+(f i -f j )(Δt i -Δt j ) (5)
by differentiating the formula (5) with the formula (4)
Θ(t i )-Θ p (t)＝(δf i -δf j )(Δt i -Δt j ) (6)
Thus, the relative frequency error is obtained as
4 relative Aren variance calculation
The Arrhenius variance criterion for estimating the frequency stability of a signal is defined as
Wherein:
n: frequency sampling points used to estimate the alembic variance; n is a positive integer not less than 100.
η: a time interval between two adjacent frequency difference sampling points; η=10 R R is a positive integer, and R.epsilon.0, 4]The method comprises the steps of carrying out a first treatment on the surface of the This data is typically five typical values of 1 second, 10 seconds, 100 seconds, 1000 seconds, and 10000 seconds.
y k+1 : first, the k +1 frequency difference sample values;
y i : the i-th frequency difference sample value. I.e. at nominal sampling frequency, y is calculated from the sequence data of inter-satellite phase measurements i Is a sequence data of (a) in a sequence data set.
In the embodiment of the application, the nominal sampling frequency of Θ (t) is 1Hz.
Sampling value is formed based on the relative frequency deviation of the double-star reference frequency source to obtain
By taking equation (9) into equation (8), the relative Allen variance equation (mathematical model) of the double-star reference frequency source can be obtained as
Since the reference frequency sources of the two stars are independently operated, the stability level of a single frequency source can be estimated as the combined stability level of two frequency sourcesNamely:
although the present application has been described in terms of the preferred embodiments, it is not intended to be limited to the embodiments, and any person skilled in the art can make any possible variations and modifications to the technical solution of the present application by using the methods and technical matters disclosed above without departing from the spirit and scope of the present application, so any simple modifications, equivalent variations and modifications to the embodiments described above according to the technical matters of the present application are within the scope of the technical matters of the present application. The embodiments of the present application and technical features in the embodiments may be combined with each other without collision.
What is not described in detail in the present specification is a well known technology to those skilled in the art.
Claims (9)
1. An on-orbit reference frequency stability estimation method of an inter-satellite link system is characterized by comprising the following steps:
1) Obtaining a bi-directional phase measurement Θ (t) without time scale correction;
2) Obtaining two-way phase measurements Θ (t) unified to the instant of iStar i )；
3) Calculating a combined phase measurement Θ from the bidirectional phase measurement Θ (t) without time scale correction p (t)；
4) The two-way phase measurement value Θ (t) obtained according to step 2) and unified to the instant of i stars i ) And the combined phase measurement Θ obtained in step 3) p (t) calculating the relative frequency error δf i -δf j ；
5) The relative frequency error δf obtained according to step 4) i -δf j Calculating a relative frequency error sampling value y;
6) Repeating the steps 1) to 5) according to the nominal sampling frequency to obtain a relative frequency error sampling value y corresponding to each frequency point; sampling the obtained sampling value y of the relative frequency error corresponding to each frequency point at equal sampling intervals, and calculating the relative Aren variance sigma y (τ)。
2. The method for estimating the stability of an on-orbit reference frequency of an inter-satellite link system according to claim 1, wherein the method for obtaining the bidirectional phase measurement value Θ (t) without time scale correction comprises the following steps:
wherein,
f i the output frequency of the i star; f (f) j The output frequency of j stars;
propagation time for a signal to be transmitted from i star to j star;
propagation time for a signal to be transmitted from j to i;
δf i deviation of the output frequency of the i star from the nominal frequency; the nominal frequency is the theoretical frequency of the satellite-borne system receiving and transmitting signals;
δf j deviation of the output frequency of j stars from the nominal frequency;
Δt i the time difference between the i star measurement time and the nominal time is the time difference between the i star measurement time and the nominal time;
Δt j the time difference between the moment of measurement for j stars and the nominal moment.
3. The method for estimating the stability of an on-orbit reference frequency of an inter-satellite link system according to claim 2, wherein a two-way phase measurement value Θ (t i ) The method of (1) comprises the following steps:
4. the method for estimating on-orbit reference frequency stability of an inter-satellite link system according to claim 2, wherein the combined phase measurement Θ is calculated p The method of (t) is specifically as follows:
Θ p (t)＝Θ(t)+(f i -f j )(Δt i -Δt j )。
5. the method for estimating on-orbit reference frequency stability of an inter-satellite link system according to claim 2, wherein the relative frequency error δf is calculated i -δf j The method of (1) comprises the following steps:
6. the method for estimating on-orbit reference frequency stability of an inter-satellite link system according to claim 2, wherein the relative frequency error sampling values are calculatedThe method of (1) comprises the following steps:
7. an on-orbit reference frequency stability estimation method for an inter-satellite link system according to any one of claims 2 to 6, wherein the relative alembic variance is calculatedThe method of (1) comprises the following steps:
where k represents a sampling number, η represents a sampling interval, and N is a positive integer not less than 100.
8. An on-orbit reference frequency stability estimation method for an inter-satellite link system according to claim 7, wherein the nominal sampling frequency is 1Hz.
9. The method for estimating on-orbit reference frequency stability of an inter-satellite link system according to claim 8, wherein said sampling interval η = 10 R The method comprises the steps of carrying out a first treatment on the surface of the Wherein R is a positive integer and R is 0,4]。
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