CN115955287A - High-precision time-frequency synchronization method for distributed interference - Google Patents
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Abstract
The invention discloses a high-precision time-frequency synchronization method for distributed interference, which is used for providing uniform time reference and frequency reference for a distributed interference system of a maneuvering platform. The invention comprises the following steps: based on a high-stability atomic clock, the slave node calculates the carrier frequency difference between the slave node and the master node by capturing and tracking the signal transmitted by the master node, adjusts the clock frequency of the slave node and keeps frequency synchronization with the master node; based on a bidirectional time comparison method, the sharp characteristic of the peak value of the correlation result of the narrow pulse signal is utilized to accurately obtain the time interval between the high-precision transmitting signal and the high-precision receiving signal; and adjusting the clocks of the slave nodes according to the obtained time synchronization errors of the master node and the slave nodes, so as to realize the time synchronization of the master node and the slave nodes.
Description
Technical Field
The invention belongs to the technical field of time frequency synchronization, and particularly relates to a high-precision time frequency synchronization method for distributed interference.
Background
In order to adapt to increasingly complex electromagnetic environments, the existing interference equipment is rapidly developed towards miniaturization, distribution and coordination, so that the mobility and the anti-strike capability of the equipment are improved. The time-frequency synchronization provides a uniform time reference and a uniform frequency reference for the distributed interference equipment, which is a basis for realizing the efficient coordination of the distributed interference equipment, and the higher the time-frequency synchronization precision is, the stronger the coordination capability of the distributed interference equipment is, for example, when the time synchronization precision reaches 0.1 time of the signal wavelength, the signal level coordination of the distributed interference system can be realized.
The time synchronization precision based on the optical fiber can reach ps magnitude, but the network distribution is tedious, and the use scene is limited. For airborne mobile platforms, wireless time-frequency synchronization techniques must be used. Common wireless time-frequency synchronization techniques include satellite-based time synchronization techniques and microwave-based time synchronization techniques. Satellite-based time synchronization techniques include satellite one-way time alignment, satellite common view, and satellite two-way time alignment. The precision of satellite one-way time comparison is related to factors such as receiver antenna coordinate error, satellite orbit error, observation station coordinate error and the like, and the precision is about 20 ns; the satellite common-view method eliminates the influence of a satellite clock and the influence of most path delay, the time comparison precision is about 5ns, but the method requires that two parties performing comparison receive the same navigation satellite signal, and has certain limitation; the satellite bidirectional time comparison method has the advantages that the propagation path is symmetrical, the propagation path delay can be almost completely offset, the time comparison precision is improved, and the equipment is complex and high in cost. According to the microwave-based two-way time comparison method, microwave communication is utilized, time comparison is carried out on two terminals by sending ranging signals mutually, and due to the fact that two-way propagation paths are almost completely the same, propagation delay can be offset, time comparison accuracy is improved, convenience and flexibility are achieved, but the method is limited by time difference measurement accuracy, and time synchronization accuracy is difficult to further improve.
In summary, how to improve the time-frequency synchronization precision between mobile platforms and realize the efficient coordination of the distributed interference system is a problem to be solved urgently by those skilled in the art.
Disclosure of Invention
The invention aims to provide a high-precision time-frequency synchronization method for distributed interference, which overcomes the defect of limited wireless time-frequency synchronization precision and realizes the improvement of high-precision time-frequency synchronization among mobile platforms in the air.
In order to achieve the above object, the present invention provides a high-precision time-frequency synchronization method for distributed interference, which includes the following steps:
step 1: the master node transmits a single-carrier signal to the slave node, the slave node captures and tracks the single-carrier signal transmitted by the master node, calculates the carrier frequency difference value between the slave node and the master node, and adjusts the clock frequency of the slave node to ensure that the master node clock and the slave node clock keep frequency synchronization;
step 2: the master node and the slave node adopt a bidirectional time comparison method to obtain time synchronization errors of the master node and the slave node;
and step 3: and adjusting the clocks of the slave nodes according to the obtained time synchronization errors of the master node and the slave nodes, so that the master node and the slave nodes are time synchronized.
Preferably, the specific method for obtaining the time synchronization error of the master node and the slave node by the master node and the slave node using the bidirectional time comparison method is as follows:
the transmitting signal adopts a narrow pulse signal, and the peak value of the correlation result of the transmitting signal and the receiving signal is extracted by utilizing the sharp characteristic of the peak value of the correlation result of the narrow pulse signal, so as to obtain the time interval.
Preferably, the specific method for obtaining the time synchronization error of the master node and the slave node by the master node and the slave node using the bidirectional time comparison method is as follows:
the master node and the slave nodes are respectively provided with respective timers, the master node transmits a narrow pulse synchronization signal, records transmission time, takes the transmission time as a door opening signal of the master node timer, performs relevant processing on the synchronization signal after receiving the synchronization signal transmitted by the slave node, takes the generated relevant pulse as a door closing signal, and obtains a receiving and transmitting time difference of the master node according to the time difference of the door opening signal and the door closing signal;
the slave node transmits a narrow pulse synchronization signal, records the transmission time, takes the transmission time as a door opening signal of the slave node timer, performs related processing on the synchronization signal after receiving the synchronization signal transmitted by the master node, takes the generated related pulse as a door closing signal, and obtains a receiving and transmitting time difference of the slave node according to the time difference of the door opening signal and the door closing signal;
and the slave node calculates the time difference between the slave node and the master node according to the master node transmission time delay, the master node receiving time delay, the slave node transmission time delay and the slave node receiving time delay.
Preferably, the master node has a difference T in the transmission and reception times 1 The method specifically comprises the following steps:
T 1 ＝Δt+τ B +T BA +τ′ A
in formula (II) is τ' A For receiving time delay of the master node, delta t is the clock difference of signals transmitted by the master node and the slave node in a transceiving period, and tau B For transmitting time delay from node, T BA Is the transmission time.
Preferably, the transceiving time difference T of the slave node 2 The method specifically comprises the following steps:
T 2 ＝-Δt+τ A +T AB +τ′ B
where Δ t is the clock difference between the signals transmitted from the master node and the slave node in a transceiving period, and τ A For transmission delay of the master node, T AB Is transmission time, τ' B To receive the delay from the node.
Preferably, the pulse width of the narrow pulse signal is in the order of 100 ps.
Compared with the prior art, the invention has the following advantages:
(1) Based on a high-stability atomic clock, the method realizes high-precision time interval extraction by utilizing the sharp characteristic of a narrow pulse signal correlation result peak value, has high time-frequency synchronization precision, and can be used for realizing signal level cooperation of a distributed interference system;
(2) The method is independent of any satellite terminal and can be applied to a mobile platform.
Drawings
Fig. 1 is a flow chart of high-precision time-frequency synchronization.
Fig. 2 is a schematic block diagram of master-slave node frequency synchronization with high-precision time-frequency synchronization.
Fig. 3 is a schematic diagram of bidirectional time comparison between master and slave nodes in high-precision time-frequency synchronization.
Fig. 4 is a time domain waveform diagram of two narrow pulse signals.
Fig. 5 is a waveform diagram of two narrow pulse signals after correlation processing.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The technical scheme of the invention is explained in detail in the following with reference to the attached drawings.
The invention provides a high-precision time frequency synchronization method for distributed interference, which provides a unified time reference and frequency reference for an aerial mobile platform, and FIG. 1 is a flow chart for realizing the high-precision time frequency synchronization. The method specifically comprises the following steps:
1) The master node transmits a single carrier signal to the slave node, the slave node captures and tracks the single carrier signal transmitted by the master node, calculates the carrier frequency difference between the slave node and the master node, adjusts the clock frequency of the slave node, realizes the acclimation of the master node to the slave node, and enables the master node clock and the slave node clock to keep frequency synchronization;
2) On the basis of frequency synchronization, the master node and the slave node perform time synchronization by adopting a bidirectional time comparison method. The master node and the slave nodes are respectively provided with respective high-precision timers, the master node transmits a synchronization signal, records the transmission time of the synchronization signal, takes the transmission time as a door opening signal of the master node high-precision timer, performs related processing on the synchronization signal after receiving the synchronization signal transmitted by the slave nodes, takes the generated related pulse as a door closing signal, and obtains the receiving and transmitting time difference of the master node according to the time difference between the door opening signal and the door closing signal; and similarly, the slave node transmits a synchronization signal, records the transmission time of the synchronization signal, takes the transmission time as a door opening signal of the slave node high-precision timer, performs relevant processing on the synchronization signal after the slave node receives the synchronization signal transmitted by the master node, takes the generated relevant pulse as a door closing signal, and obtains the transceiving time difference of the slave node according to the time difference between the door opening signal and the door closing signal. According to the two-way time comparison principle, the time synchronization error of the master node and the slave node can be obtained;
3) And adjusting the clocks of the slave nodes according to the obtained time synchronization errors of the master node and the slave nodes, so that the master node and the slave nodes are time synchronized.
The method for realizing high-precision time-frequency synchronization for distributed interference of the present invention is further described below.
Fig. 2 is a schematic diagram of the master-slave node frequency synchronization for high-precision time-frequency synchronization of distributed interference according to the present invention.
The method comprises the steps that a main node transmits a single carrier signal with fixed frequency, the single carrier signal is received by a slave node after being transmitted in space, the slave node performs frequency mixing on the received signal to obtain an intermediate frequency signal and performs digital sampling on the intermediate frequency signal, meanwhile, the slave node performs Doppler estimation according to a received synchronization signal and an attitude parameter, obtains a frequency difference between the slave node and the main node according to a Doppler estimation result and a frequency measurement result of the received signal, and adjusts the output frequency of an atomic clock according to the frequency difference to discipline the atomic clock so as to realize frequency synchronization with the main node. It should be noted that the atomic clock used herein is a high-stability rubidium atomic clock, the second stability of the atomic clock can reach 2E-12@1s, the frequency adjusting precision can reach 1E-13, the atomic clocks at the master node and the slave node operate independently after initial calibration, and the frequency difference is mainly caused by the frequency drift of the atomic clock along with time, so that the higher the frequency stability of the atomic clock is, the slower the frequency drift along with time is, and the smaller the frequency adjustment amount required within a certain time is.
Fig. 3 is a schematic diagram of bidirectional time comparison between master and slave nodes for high-precision time-frequency synchronization of distributed interference according to the present invention.
The master node and the slave node are respectively controlled by respective local clocks and independently face each otherAnd sending a synchronization signal, and marking the time points of the transmitting time and the receiving time respectively. The transmission time of the main node is recorded as TA, and the transmission time delay is tau A After the transmission time TAB, the data arrives at the slave node at the time TB2, and the receiving time delay of the slave node is tau' B . In the same transceiving period, the transmitting time of the slave node is T B1 Clock difference with the master node is delta t, and emission time delay of the slave node is tau B Over a transmission time T BA In T at A2 The time reaches the master node, and the receiving time delay of the master node is tau' A . In fig. 3, the total time delay of master node transceiving is T 1 Total time delay of receiving and transmitting from the slave node is T 2 . Obviously, there are:
T 1 ＝Δt+τ B +T BA +τ′ A
T 2 ＝-Δt+τ A +T AB +τ′ B
because the master node and the slave node respectively transmit signals independently, the clock difference delta t exists between the two transmitted signals in each transceiving period, and the transmission time delay tau of the master node A Receiving time delay tau 'by the main node' A Emission time delay tau from node B Receiving time delay tau 'from node' B Can be measured by calibration, T 1 Time difference, T, between transmitted and received signals measured for the master node 2 The time difference between the transmitted signal and the received signal measured by the slave node is that the movement speed of the master node and the slave node is much less than the propagation speed of the electromagnetic wave, and assuming that the relative movement speed of the master node and the slave node is 30m/s and the distance between the master node and the slave node is 3km, the distance between the master node and the slave node changes by 0.3mm in the process of transmitting the signal from the master node to the slave node, so that it can be considered that T is the time difference between the transmitted signal and the received signal BA And T AB Substantially equal, it is obvious that the clock difference Δ t between the master node and the slave node can be obtained as follows:
according to the clock difference obtained by measurement, the slave node adjusts the time of the clock of the slave node, and the clock time adjustment between the slave node and the master node is realizedAnd (5) time synchronization. Obviously, the time synchronization accuracy is transmitted by the master node with a time delay τ A Receiving time delay tau 'of main node' A Emission time delay tau of slave node B Receiving time delay tau 'from node' B Calibration precision, and time difference T between transmitting signal and receiving signal of main node 1 And the time difference T between the transmission and reception of signals from the node 2 Wherein the master node transmission delay τ is determined by the measurement accuracy of A Receiving time delay tau 'of main node' A Emission time delay tau from node B Receiving time delay tau 'from node' B The calibration precision of the inherent error of the slave node transceiver of the master node transceiver can reach ps magnitude under laboratory conditions, and the time difference T between the transmitting signal and the receiving signal of the master node 1 And the time difference T between the transmission signal and the reception signal from the node 2 Typically by counting the respective operating clocks of the master and slave nodes. In the invention, in order to realize high-precision time-frequency synchronization, the main node transmitting signal and the slave node transmitting signal both adopt narrow pulse signals, the main node transmitting signal and the received slave node transmitting signal are subjected to correlation processing, and the peak value of the correlation result of the narrow pulse signals is extracted to obtain the accurate time difference between the transmitting signal and the receiving signal.
As shown in fig. 4, it is a time domain waveform diagram of two narrow pulse signals in the present invention, the pulse width is 100ps, and the time interval is 50ps.
As shown in fig. 5, which is a waveform diagram of two narrow pulse signals with a time interval of 50ps after correlation processing in the present invention, it can be seen that, after the two narrow pulse signals with a time interval of 50ps are subjected to correlation processing, the time interval of the two narrow pulse signals can be accurately obtained through peak extraction of a correlation result.
Claims (6)
1. A high-precision time-frequency synchronization method for distributed interference is characterized by comprising the following steps:
step 1: the method comprises the steps that a master node transmits a single-carrier signal to a slave node, the slave node captures and tracks the single-carrier signal transmitted by the master node, calculates the carrier frequency difference value between the slave node and the master node, and adjusts the clock frequency of the slave node to enable the master node clock and the slave node clock to keep frequency synchronization;
step 2: the master node and the slave node adopt a bidirectional time comparison method to obtain time synchronization errors of the master node and the slave node;
and step 3: and adjusting the clocks of the slave nodes according to the obtained time synchronization errors of the master node and the slave nodes, so that the master node and the slave nodes are time synchronized.
2. The high-precision time-frequency synchronization method for distributed interference according to claim 1, wherein the specific method for obtaining the time synchronization error of the master node and the slave node by the bidirectional time comparison method is as follows:
the transmitting signal adopts a narrow pulse signal, and the peak value of the correlation result of the transmitting signal and the receiving signal is extracted by utilizing the sharp characteristic of the peak value of the correlation result of the narrow pulse signal, so as to obtain the time interval.
3. The high-precision time-frequency synchronization method for distributed interference according to claim 1 or 2, wherein the specific method for obtaining the time synchronization error of the master node and the slave node by the bidirectional time comparison method is as follows:
the master node and the slave nodes are respectively provided with respective timers, the master node transmits a narrow pulse synchronization signal, records transmission time, takes the transmission time as a door opening signal of the master node timer, performs related processing on the synchronization signal after receiving the synchronization signal transmitted by the slave node, takes the generated related pulse as a door closing signal, and obtains a receiving and transmitting time difference of the master node according to a time difference between the door opening signal and the door closing signal;
the slave node transmits a narrow pulse synchronization signal, records transmission time, takes the transmission time as a door opening signal of a slave node timer, performs related processing on the synchronization signal after receiving the synchronization signal transmitted by the master node, takes the generated related pulse as a door closing signal, and obtains a transceiving time difference of the slave node according to a time difference between the door opening signal and the door closing signal;
and the slave node calculates the time difference between the slave node and the master node according to the master node transmission time delay, the master node receiving time delay, the slave node transmission time delay and the slave node receiving time delay.
4. The method for high precision time-frequency synchronization of distributed interference as claimed in claim 3, wherein the T-T time difference of the master node 1 The method specifically comprises the following steps:
T 1 ＝Δt+τ B +T BA +τ A
in the formula (1), tau' A For receiving time delay of the master node, delta t is the clock difference of signals transmitted by the master node and the slave node in a transceiving period, and tau B For transmitting time delays, T, from nodes BA Is the transmission time.
5. A high precision time-frequency synchronization method for distributed interference according to claim 3 characterized in that the T-T time difference of the slave nodes 2 The method specifically comprises the following steps:
T 2 ＝-Δt+τ A +T AH +τ B
where Δ t is the clock difference between the signals transmitted from the master node and the slave node in a transceiving period, and τ A For transmission delay of the master node, T AB Is transmission time, τ' B To receive the delay from the node.
6. A high accuracy time-frequency synchronization method for distributed interference according to claim 3, characterized in that the pulse width of the narrow pulse signal is in the order of 100 ps.
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