CN108551378B - A kind of radiofrequency signal remote transmission method - Google Patents
A kind of radiofrequency signal remote transmission method Download PDFInfo
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- CN108551378B CN108551378B CN201810128312.9A CN201810128312A CN108551378B CN 108551378 B CN108551378 B CN 108551378B CN 201810128312 A CN201810128312 A CN 201810128312A CN 108551378 B CN108551378 B CN 108551378B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/0635—Clock or time synchronisation in a network
- H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
- H04J3/0658—Clock or time synchronisation among packet nodes
- H04J3/0661—Clock or time synchronisation among packet nodes using timestamps
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
- H04L1/0006—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission format
- H04L1/0007—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission format by modifying the frame length
- H04L1/0008—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the transmission format by modifying the frame length by supplementing frame payload, e.g. with padding bits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L49/00—Packet switching elements
- H04L49/90—Buffering arrangements
- H04L49/9057—Arrangements for supporting packet reassembly or resequencing
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Abstract
The present invention provides a kind of radiofrequency signal remote transmission methods.Multiple channels radiofrequency signal to be transmitted is carried out down coversion, analog/digital conversion, low-pass filtering, extraction, digital AGC, quantification treatment by transmitting terminal, obtain N number of channel digital signal, N number of channel digital signal is packaged, serial data is formed using time-division multiplexing method, and send it to receiving end；Receiving end stores same channel data packet into reception buffer area, later, with according to packet serial number, out-of-order rearrangement processing is first carried out to the channel data packet received in buffer area and carries out packet loss filling again, obtain the continuous data packet of no packet loss random ordering, poll channel data packet, on the basis of at the time of expression by the timestamp in channel data packet, postpone set time T, corresponding channel digital signal is extracted according to quantization digit, interpolation, low-pass filtering, D/A switch, upconversion process are successively carried out to it, finally recover the radiofrequency signal of transmission.
Description
Technical field
It is mutual to be suitable for more networking satellite ground interconnections of dipper system for a kind of radiofrequency signal remote transmission method of the present invention
Logical multilink remote fiber docking test and other space mission Major Ground Tests, belong to technical field of electronic communication.
Background technique
With the construction of Chinese Beidou satellite navigation system, gradually from No. two area navigation systems of Beidou of the service Asian-Pacific area
System develops into No. three Global Navigation Systems of Beidou of Service Global, and maximum variation is exactly to introduce inter-satellite link technology, will
Multi-satellite interconnects information transmission and the exchange realized between satellite together, and function mainly allows between star and star and realizes
Communication, ranging, and then promote the autonomous controllable ability of navigation system.By inter-satellite link, big-dipper satellite whole world system will be realized
System independent navigation.Measurement track and time service precision are improved, and reduces the dependence to ground cloth station, the operation pipe of system is effectively reduced
Cost is managed, the anti-lethality of wartime system is greatly improved.
Before dipper system networking satellite launch, needs to carry out sufficient verification experimental verification on ground, just can guarantee Mission Success
Rate；Traditional single star single-link floor synthetic docking test is unable to complete inter-satellite link network layer and protocol layer authentication, it is necessary to open
The comprehensive docking test of Zhan Duoxing multilink.However the space flight Fifth Academy of Aerospace Industry, Liang Jia satellite population unit of dipper system, the Chinese Academy of Sciences is small defends
Star innovation research institute is located at Beijing and Shanghai, and the satellite to be measured of satellite assembly workshop and a large amount of mating guarantee equipment are being sent out
Thousands of kilometers are carried out before penetrating and moves the comprehensive docking test of development and unrealistic, need to solve remote (the thousands of public affairs of radiofrequency signal
In) transmission is just able to achieve the comprehensive docking in more star multilinks strange land and tests.
The dedicated large-scale ground test macro of dipper system is built in nine institute's computer room of space flight, apart from space flight Fifth Academy of Aerospace Industry satellite workshop
Several kilometers, apart from 1,000 Yu Gongli of Shanghai satellite workshop, a kind of radiofrequency signal remote transmission method is needed, space flight is just able to achieve
Comprehensive pair of more star multilinks of nine institute's Beidou ground testing systems and space flight Fifth Academy of Aerospace Industry satellite workshop, Shanghai satellite workshop satellite to be measured
Test is connect, dipper system inter-satellite link network layer and protocol layer authentication are completed.
Radiofrequency signal can be carried out Distance Transmission farther out by traditional simulation optical transmission method, but maximum transmission distance has
Limit, is usually no more than 100km, and needs exclusive single mode optical fiber；If the light for debugging signal by increasing adaptation simulated light is put
Big device realizes relay transmission, and maximum transmission distance can achieve 200~300km, but individually lays single mode optical fiber and build suitable
The at high cost of the light-repeating ship of light modulating signal should be simulated, enforcement difficulty is big；And optical transmission method is simulated with transmission range
Increase, noise and nonlinearity product are constantly accumulated, and transmitting radio frequency signal carrier-to-noise ratio can be deteriorated, and transmission range is longer, transmit radio frequency
Signal quality is poorer.Therefore, it no matter technically or in cost, is realized between Beijing-Shanghai using simulation light transmission scheme
The radio signal transmission of more than 1000 kilometers is infeasible.
Summary of the invention
Technology of the invention solves the problems, such as: being directed to above-mentioned dipper system mission requirements, proposes a kind of radiofrequency signal long distance
From transmission method, solve the problems, such as that dipper system carries out the comprehensive docking of the more star multilinks in strange land.
The technical solution of the invention is as follows: a kind of radiofrequency signal remote transmission method, this method include transmitting terminal
The step of step and receiving end, in which:
Steps are as follows for transmitting terminal:
(1), N number of channel radiofrequency signal to be transmitted is subjected to down coversion and obtains intermediate-freuqncy signal, later to intermediate-freuqncy signal into
Row analog/digital conversion, low-pass filtering, extraction, digital AGC, quantification treatment obtain N number of channel digital signal, N >=1；
(2), N number of channel digital signal is packaged and constitutes N number of channel data packet, each channel data packet includes packet header and right
Channel digital signal is answered, middle wrapping head includes packet serial number, channel number, timestamp, quantization digit, and the timestamp is channel data
Packet is packaged the moment, and the packet numeric order is incremented by；
(3), N number of channel data packet is formed serial data by time-division multiplexing method by transmitting terminal, and is sent it to and connect
Receiving end；
Receiving end parses the serial data received, N number of channel data packet is obtained, and according to channel number, by same channel
Data packet is stored to receiving in buffer area, and later, receiving end executes following steps to the channel data packet in each channel:
(4), channel data packet is parsed, packet serial number is obtained, it is first to the channel data packet received in buffer area according to packet serial number
It carries out out-of-order rearrangement processing and carries out packet loss filling again, obtain the continuous data packet of no packet loss random ordering, and stored slow to output
Rush area；
(5), the channel data packet in poll output buffer, parses timestamp information and quantization digit, with port number
On the basis of the time indicated according to the timestamp in packet, postpone set time T, corresponding channel number word is extracted according to quantization digit and is believed
Number, interpolation, low-pass filtering, D/A switch and upconversion process are successively carried out to it, recover the radiofrequency signal of transmission.
The transmitting terminal has synchronous reference time frequency signal with receiving end, and the reference time frequency signal includes clock signal
And second pulse signal, clock signal are used to guarantee that transmitting terminal is synchronous with the sampling clock of receiving end, pulse per second (PPS) is sent for guaranteeing
The time synchronization at end and receiving end.
The set time T is greater than maximum transmission time of the serial data from transmitting terminal to receiving end.
The transmitting terminal and receiving end are communicated by optical fiber or commercial data line.
When transmitting terminal and receiving end are communicated by optical fiber, the reference time frequency signal of the synchronization passes through data clock
The method of recovery is realized.
When transmitting terminal and receiving end are communicated by commercial data, the reference time frequency signal of the synchronization passes through satellite
The method regarded altogether is realized.
Out-of-order rearrangement treatment process in step (4) are as follows:
(4.1), according to the principle of first in, first out, the channel data packet received in buffer area is extracted, deposit can be held
Receive in first extra buffer of M channel data packet, the M be greater than two neighboring packet serial number channel data packet it is out-of-order after
Maximum spacing, and the value for initializing expected packet serial number is 0；
(4.2), according to the value of expected packet serial number, the packet header of each channel data packet in the first extra buffer is traversed,
To check the corresponding channel data packet of expected packet serial number whether in the first extra buffer, if expected packet serial number is corresponding
Channel data packet in the first extra buffer, then the channel data packet is read from the first extra buffer deposit second
In extra buffer, then next channel data packet is read from reception buffer area and inserted in the first extra buffer, insert position
It sets as the position of newest read-out channel data packet, enters step (4.3), otherwise, be directly entered step (4.3)；
(4.3), expected packet serial number is updated, is repeated step (4.2)~step (4.3), until receiving complete in buffer area
Portion's channel data packet is all disposed.
Packet loss described in step (4) fills treatment process are as follows:
(4.4), it is successively read channel data packet from the second extra buffer, judges current channel data packet serial number and expected
Whether packet serial number is identical, identical, then current channel data packet is stored in output buffer, enters step (4.5)；Otherwise, will recognize
To there is packet drop appearance, inserting a bag data at this time is the data packet of full 0 to output buffer, enters step (4.5)；
(4.5), expected packet serial number is updated, is repeated step (4.4)~step (4.5), until will be in second buffering area
Channel data packet is all arranged in output buffer.
In step (5) on the basis of the time that the timestamp in channel data packet indicates, postpone the specific side of set time T
Method are as follows: firstly, sending control instruction data packet in synchronization to transmitting terminal and receiving end respectively and receiving director data
Packet, transmitting terminal start after acquiring AD conversion when receiving a second pulse signal after receiving transmission control instruction data packet
Data and organize packet send；Receiving end then receive receive control instruction after receive a second pulse signal after, be with pulse per second (PPS)
Benchmark waits fixed delay T to start for the channel digital signal in output buffer to be sent to D/A converter progress DA conversion again,
In this period of waiting, if receiving end has received the data that transmitting terminal is sent, then it is temporarily stored in output buffer and does not bother to see me out
DA conversion is carried out toward D/A converter.
Compared with the prior art, the invention has the advantages that:
(1), the present invention is using when receiving end adds the method for data receiver buffer area, solves the transmission in fiber optic communication
Prolong instability problem.
(2), the present invention solves the problems, such as transmission data packet packet loss using packet loss fill method.
(3), the present invention solves the problems, such as transmission data packet disorder using in out-of-order rearrangement method.
Detailed description of the invention
Fig. 1 is that the present invention is based on the sampling restorer schematic diagrams that optical fiber transmits；
Fig. 2 is that the present invention is based on the sampling restorer schematic diagrams of commercial premises data transfer；
Fig. 3 is that the embodiment of the present invention transmits data packet disorder rearrangement process；
Fig. 4 is that the embodiment of the present invention transmits data packet packet loss filling process；
Fig. 5 is propagation delay time of embodiment of the present invention control principle；
Fig. 6 is satellite common vision of embodiment of the present invention Data processing of receiver process；
Fig. 7 is that the embodiment of the present invention is formed based on the radiofrequency signal distance transmission system of optical fiber；
Fig. 8 is that the embodiment of the present invention is formed based on the radiofrequency signal distance transmission system of commercial data special line.
Specific embodiment
Below in conjunction with specific embodiment and Figure of description, the present invention is described in detail.
When (such as in same city) it is within 100km that radiofrequency signal, which needs transmission range, laying or rental single mode are naked
Cost is relatively low for optical fiber, and can recover Time-Frequency Information from the data that optical fiber transmits；Transmitting terminal utilizes acquisition restorer
Analog radio-frequency signal to be transmitted is converted digital signal by modulus (A/D) converter, transmits in single mode bare fibre, receiving end
The digital signal received is reverted into analog radio-frequency signal using digital-to-analogue (D/A) converter of acquisition restorer, realization is penetrated
Frequency signal transmits at a distance.Its core technology is that transmitting terminal is consistent with the sampling of receiving end and recovered clock, extensive using data
Transmission recovered clock data while multiple clock method transmit digital signal in optical fiber, for both ends analog-to-digital conversion device (A/D) and
Digital analog converter (D/A) uses identical clock.Therefore it is based on the remote transmitting radio frequency signal of optical fiber, may be implemented in same city
(within distance 100km) different testing locations carry out the comprehensive docking test of radio frequency link.
When (such as in different cities) it is several hundred kms or more that radiofrequency signal, which needs transmission range, laying or rental single mode
Bare fibre cost is high, and the commercial data special line cost for only renting certain bandwidth is just subjected to；Using commercial data special line without
Method recovered clock signal realizes strange land Time and Frequency Synchronization (the transmission range upper limit is 100km), but can use satellite common vision side
Method realizes strange land Time and Frequency Synchronization (for transmission range without limitation, cost is slightly higher)；Transmitting terminal utilizes the modulus (A/D) for acquiring restorer
Analog radio-frequency signal to be transmitted is converted digital signal by converter, transmits in commercial data special line, and receiving end utilizes and adopts
The digital signal received is reverted to analog radio-frequency signal by digital-to-analogue (D/A) converter for collecting restorer, realizes radiofrequency signal
Remote transmission.Its core technology is that transmitting terminal is consistent with the sampling of receiving end and recovered clock, utilizes satellite common vision technology
It realizes strange land Time and Frequency Synchronization, uses identical clock for both ends analog-to-digital conversion device (A/D) and digital analog converter (D/A).Therefore, base
In commercial data special line transmitting radio frequency signal, it is comprehensive that strange land (no distance limitation) different testing location development radio frequency links may be implemented
Close docking test.But commercial data special line transmission data delay is unstable, in fact it could happen that transmission data packet packet loss and random ordering.
The present invention is based on the feasibility of above-mentioned optical fiber or the radiofrequency signal remote transmission method of commercial data special line and deposit
Difficulty, propose a kind of radiofrequency signal remote transmission method, this method adds data receiver buffer area using receiving end
Method solves propagation delay time instability problem；Data packet disorder is solved the problems, such as using out-of-order reordering technique；Utilize packet loss filling side
Method solves the problems, such as packet loss；The strange land video of remote (the being not more than 100km) transmission of optical fiber is realized using data recovery clock method
It is synchronous；The strange land Time and Frequency Synchronization of remote (the being greater than 100km) transmission of commercial data special line is realized using satellite common vision method.Using
The method achieve nine institute's Beidou ground test computer room (Beijing) of space flight and space flight Fifth Academy of Aerospace Industry satellite workshop, Shanghai satellite workshop are to be measured
The comprehensive docking test of more star multilinks of satellite, effectively demonstrates No. three inter-satellite link network layers of Beidou and protocol layer, to Beidou
System Construction is of great significance, and can also be generalized in other space flight model tasks.
A kind of specific implementation of above-mentioned radiofrequency signal remote transmission method includes the steps that the step of transmitting terminal and receiving end
Suddenly, the transmitting terminal has synchronous reference time frequency signal with receiving end, and the reference time frequency signal includes clock signal and second
Pulse signal, clock signal for guaranteeing that transmitting terminal is synchronous with the sampling clock of receiving end, use by second pulse signal (1PPS signal)
In the time synchronization for guaranteeing transmitting terminal and receiving end.Wherein:
Steps are as follows for transmitting terminal:
(1), N number of channel radiofrequency signal to be transmitted is subjected to down coversion and obtains intermediate-freuqncy signal, later to intermediate-freuqncy signal into
Row analog/digital conversion, low-pass filtering, extraction, digital AGC, quantification treatment obtain N number of channel digital signal, N >=1；
Low-pass filtering treatment is used to anti-signal aliasing, extracts and is used to realize the down-sampled of signal, and digital AGC is used to realize letter
Number power control, the purpose of quantization be then in order to convert data to suitable message transmission rate, when transmission bandwidth affluence,
Using high quantization digit, radio signal transmission quality is improved；When transmission bandwidth anxiety, using low quantization digit, transmission is reduced
Bandwidth demand.
If transmitted using single mode optical fiber, transmission rate is up to 10Gbps, therefore full scale can be used in each channel
12bit quantization digit is transmitted；If transmitted using commercial data special line, consider that (transmission rate is got over from funds feasibility
Height, Leased line lease expenses are higher), transmission rate is far below 10Gbps, it is therefore necessary to be used according to the case where each channel
Different bit quantization digit is transmitted.
Quantify the strategy used to be transmitted for the interception A/D high position sent, the mode that low level is directly cast out, such as using
4bit quantization, then only intercept high 4bit, low 8bit directly casts out.When receiving end reverts to the 12bit data for giving D/A, then
It need to be in low 8bit zero padding.
Due to using quantization strategy, it is therefore desirable to carry out digital AGC, signal is amplified to full scale as far as possible, to ensure
The case where signal amplitude is less than quantizing range will not be gone out in bit quantization.AGC module carries out function to the signal that sampling is come in first
Rate estimation, compares the amplitude size of itself and full scale signal；If signal power is much smaller than full scale signal amplitude, amplify letter
Number, guarantee that amplified signal reaches 50% or more of full scale signal amplitude.
(2), N number of channel digital signal is packaged and constitutes N number of channel data packet, each channel data packet includes packet header and right
Channel digital signal is answered, middle wrapping head includes packet serial number, channel number, timestamp, quantization digit, and the timestamp is channel data
Packet is packaged the moment；
After starting transmission, transmitting terminal one data packet of every transmission, packet sequence number field increases 1 certainly.
The length of each channel data packet is identical, and quantization digit is low, and the data volume in the unit time is few, in each data packet
It is long comprising data time；Quantization digit is high, and the data packet in the unit time is more, short comprising data time in each data packet.
(3), N number of channel data packet is formed serial data by time-division multiplexing method by transmitting terminal, and is sent it to and connect
Receiving end.Specifically: N number of channel data packet is time-multiplexed by way of poll and forms serial data, some channels by transmitting terminal
Quantization digit is low, and total amount of data is small, and data packet is few in the unit time, and poll often makes a turn the transmission of no data packet and directly skips；Have
Channel quantization digit it is high, total amount of data is big, data packet is more in the unit time, and poll often has data packet transmission.
As depicted in figs. 1 and 2, the transmitting terminal and receiving end can be communicated by optical fiber or commercial data line.Work as biography
When defeated route is single mode optical fiber, serial data is converted to optical signal by standard commercial optical module (such as 10Gbps optical module),
Receiving end is sent to by single mode optical fiber；When transmission line is commercial data special line, serial data is according still further to standard UDP protocol
It carries out being packaged encapsulation again, send to interchanger, receiving end is sent to by commercial data special line.
Receiving end parses the serial data received, N number of channel data packet is obtained, and according to channel number, by same channel
Data packet is stored into reception buffer area (FIFO)；
When transmission line is single mode optical fiber, receiving end receives optical signal and passes through standard commercial optical module (such as 10Gbps
Optical module) be converted to serial data；When transmission line is commercial data special line, end switch output data is received according to standard
Udp protocol unpacking is converted to serial data.
Later, receiving end executes following steps to the channel data packet in each channel:
(4), channel data packet is parsed, packet serial number is obtained, it is first to the channel data packet received in buffer area according to packet serial number
It carries out out-of-order rearrangement processing and carries out packet loss filling again, obtain the continuous data packet of no packet loss random ordering, and stored slow to output
Rush area.
Due to will lead to the generation of out-of-order and packet loss in transmission process, receiving end must arrange again data packet
Sequence and packet loss supplement, to guarantee that propagation delay time is stablized.
An expectation packet serial number register is safeguarded in receiving end, and after often receiving a data packet, which increases 1 certainly.Data
The out-of-order rearrangement treatment process of packet is as shown in Figure 3:
(4.1), according to the principle of first in, first out, the channel data packet received in buffer area is extracted, deposit can be held
It receives in first extra buffer (such as RAM) of M channel data packet, the M is greater than the channel data packet of two neighboring packet serial number
Maximum spacing after random ordering, and the value for initializing expected packet serial number is 0；
(4.2), according to the value of expected packet serial number, the packet header of each channel data packet in the first extra buffer is traversed,
To check the corresponding channel data packet of expected packet serial number whether in the first extra buffer, if expected packet serial number is corresponding
Channel data packet in the first extra buffer, then the channel data packet is read from the first extra buffer deposit second
In extra buffer, then next channel data packet is read from reception buffer area and inserted in the first extra buffer, insert position
It sets as the position of newest read-out channel data packet, enters step (4.3), otherwise, be directly entered step (4.3)；
(4.3), expected packet serial number is updated, is repeated step (4.2)~step (4.3), until receiving complete in buffer area
Portion's channel data packet is all disposed.
It is as shown in Figure 4 that data packet packet loss fills treatment process:
(4.4), it is successively read channel data packet from the second extra buffer, judges current channel data packet serial number and expected
Whether packet serial number is identical, identical, then current channel data packet is stored in output buffer, enters step (4.5)；Otherwise, will recognize
To there is packet drop appearance, inserting a bag data at this time is the data packet of full 0 to output buffer, enters step (4.5)；
(4.5), expected packet serial number is updated, is repeated step (4.4)~step (4.5), until will be in second buffering area
Channel data packet is all arranged in output buffer.
(5), the channel data packet in poll output buffer, parses timestamp information and bit quantization digit, with channel
On the basis of the time that timestamp in data packet indicates, postpone set time T, corresponding channel is extracted according to bit quantization digit
Digital signal successively carries out interpolation, low-pass filtering, D/A switch to it and obtains intermediate-freuqncy signal, then by intermediate-freuqncy signal up-conversion,
The radiofrequency signal of transmission is finally recovered, the set time T is greater than maximum transmitted of the serial data from transmitting terminal to receiving end
Time.
Due to affected by various factors in the transmission process of data packet, the end-to-end time delay of data packet wave will lead to
It is dynamic.In order to realize that propagation delay time accurately controls, therefore need to be guaranteed by a kind of mechanism from number transmitting terminal A/D to receiving end D/A
The propagation delay time of word signal is stable.
On the basis of the time that the timestamp in channel data packet indicates, delay set time T's method particularly includes: first
First, in synchronization, control instruction data packet is sent to transmitting terminal and receiving end respectively and receives director data packet, is sent
End starts to acquire the data after AD is converted simultaneously when receiving a second pulse signal after receiving transmission control instruction data packet
Group packet is sent；Receiving end then receive receive control instruction after receive a second pulse signal after, on the basis of pulse per second (PPS), wait
Fixed delay T starts for the channel digital signal in output buffer to be sent to D/A converter progress DA conversion again, in this of waiting
In the section time, if receiving end has received the data that transmitting terminal is sent, then it is temporarily stored in output buffer without being sent to DA conversion
Device carries out DA conversion.Propagation delay time control principle is as shown in Figure 5.When the transmission of transmitting terminal is enabled draws high, start the letter of A/D
It number is packaged and to be transmitted into data packet；When the reception of receiving end is enabled draws high, the data for starting to receive are sent to D/A.
According to this operation, after receiving end starts to transmit data to D/A, as long as the data in the FIFO of buffer area are not empty not
Full, then the propagation delay time from A/D to D/A remains fixed delay T, to realize the strict control of propagation delay time.Due to
The clock frequency of A/D and D/A sampling is strictly with frequency, therefore in normal transmission, data in the FIFO of buffer area should be
It is fluctuated in the range of one very little.
The setting of propagation delay time T must satisfy the following conditions: (1) it is greater than the propagation delay time of transmitting-receiving both ends data packet, so as to
When receiving end, which is opened, receives enabled, there are data in the FIFO of buffer area；(2) time delay cannot be too big, to prevent from opening in receiving end
When receiving enabled, buffer area FIFO completely causes loss of data.
The effect of interpolation is a liter sampling, and low-pass filtering is to eliminate the high frequency images occurred in frequency spectrum interference.
From the foregoing, it will be observed that the reception of receiving end buffers if the clock reference frequency different frequencies that transmitting terminal and receiving end use
Area FIFO reads empty or overflows, and will lead to and restores spectrum of radio frequency signals distortion.Pulse per second (PPS) be used to guarantee transmitting terminal and receiving end when
Between it is synchronous, so that transmitting terminal and receiving end is sampled restorer and start to execute movement in synchronization, if transmitting terminal and receiving end
The time irreversibility used, will lead to the non-setting value of radio signal transmission time delay, the reception buffer area FIFO of receiving end read it is empty or
It overflows.
When transmitting terminal and receiving end are communicated by optical fiber, the reference time frequency signal of the synchronization passes through data clock
The method of recovery is realized.Data clock restoration methods rely primarily on the clock recovery circuitry of FPGA high speed serial transceiver into
Row.
The 10Gbps serial digital signal that optical fiber is sent is after amplitude adjusts, edge and centre of the sampling clock to data
Position is sampled.Signal after sampling is sent into clock recovery circuitry, which adjusts according to the information of sampled signal and sample
The phase of clock makes sampling clock just sample the medium position of data.It in this way can be by local sampling clock
It adjusts to identical as transmitting terminal data phase, is sent after the sampling clock is divided to FPGA and used.
Since whole flow process carries out under the rate of 10Gbps, and recovered clock is identical as transmitting terminal data phase, because
Phase deviation between this recovered clock and data is not more than the transmission time of a bit, i.e. 100ps.
The 10GHz clock recovered under 10Gbps rate and the clock jitter of source are less than 100ps, however when 10GHz
10MHz clock needed for clock need to can just obtain sampling restorer after dividing twice, divide operation can cause to connect twice for this
There is deviation in the 10MHz clock of receiving end and the 10MHz clock phase of transmitting terminal.
The work clock of the high speed serialization transceiver of FPGA is 250MHz, and the 250MHz clock of transmitting terminal is directly by 10MHz
Frequency multiplication obtains, therefore the uncertainty of phase is not present；The 250MHz clock that receiving end is restored is due to being divided from 10GHz
, therefore with the 250MHz clock of transmitting terminal there are phase indeterminacy, counting the time is Δ T1.After obtaining 250MHz clock,
It need to divide again to 10MHz so that sampling restorer uses, introduce phase indeterminacy again at this time, counting the time is Δ T2.
The core that recovered clock keeps phase to determine is to eliminate Δ T1 and Δ T2, and the phase error for contributing it is within 1ns.
High speed serialization transceiver is encoded in transmission using 8B/10B, and data bit width used when inter-process is after coding
40bit.Receiving end when receiving data, can confirm the boundary of serial data, by comma alignment first to carry out serial number
According to the conversion for arriving parallel data.
The high speed serialization transceiver of FPGA when carrying out comma alignment, will record lower comma alignment at the time of relative to
The delay of 250MHz rising edge, the numerical value which is 0~39.Since comma sequence is the rising edge in 250MHz in transmitting terminal
It sends out, and the 250MHz of receiving end is with transmitting terminal that there are phase deviations, therefore when receiving comma sequence, comma sequence
Synchronization point and the rising edge of 250MHz there are errors.By reading the status register of high speed serialization transceiver, can read
The value out.Then by the phase shift function of FPGAMMCX, according to the digital baseband input signal of reading, by the 250MHz clock phase of receiving end
It is moved to identical with transmitting terminal.After the processing, the 250MHz for receiving and dispatching both ends can reach within 100ps with phase precision.
In clock phase alignment, 1PPS is mainly used for being aligned the 10MHz phase of transmitting terminal and receiving end.It has eliminated before
Phase does not know Δ T1, and eliminates Δ T2 and transmitting terminal and receiving end is then needed to have a time reference, which is
Synchronous 1PPS.
Transmitting terminal generates the 1PPS pulse under a 250MHz clock domain, is sent to receiving end in the rising edge of 10MHz.
The pulse is after optical fiber transmits, when recovering the 250MHz of 1PPS pulse and transmitting terminal by same data clock restoration methods
Clock, so as to generate the high speed serialization Transceiver Clock for the receiving end 250MHz being aligned with the 250MHz of transmitting terminal, in the height
Under the driving of fast serial transceiver clock, after transmitting terminal 1PPS rising edge of a pulse, after plaing a bat by local 250MHz clock,
It has obtained differing the 1PPS for being fixed as 4ns with transmitting terminal, the as 1PPS of receiving end.
The finally obtained 1PPS adjusted in receiving end differs fixed 4ns with the rising edge of transmitting terminal 10MHz.Therefore should
1PPS can be used for being aligned for subsequent receiving end 10MHz and transmitting terminal 10MHz.
The 250MHz clock and 1PPS with transmitting terminal with phase has been obtained in front, need in next step through the clock and
1PPS obtains the 10MHz clock with transmitting terminal with phase.
Receiving end divides 250MHz clock adjusted to 10MHz by MMCX, which can introduce phase error Δ
T2.By the 250MHz clock domain down-sampling of the 10MHz clock after frequency dividing after the adjustment, this makes it possible to obtain the risings of 10MHz clock
Edge.Then under 250MHz clock domain after the adjustment, the rising edge of 10MHz and 1PPS adjusted are subjected to phase bit comparison, it can
Obtain the phase difference between receiving end 10MHz clock and 1PPS adjusted.And due to 1PPS adjusted and transmitting terminal 10MHz
Phase fix, therefore this phase difference can reflect the phase difference of the 10MHz and transmitting terminal 10MHz of receiving end.
Then, according to obtained phase difference, by 10MHz clock by the MMCX phase shift of FPGA to and transmitting terminal 10MHz phase
Position is identical, then receiving end has just obtained the reference clock with transmitting terminal 10MHz with phase.The in-phase clock sampling is supplied again to restore
Equipment uses, that is, can guarantee that the sampling clock phase relationship of transmitting terminal and receiving end determines.
When transmitting terminal and receiving end are communicated by commercial data, the reference time frequency signal of the synchronization passes through satellite
The method regarded altogether is realized.
" satellite common vision " is exactly the observer of two different locations, observes same or same group of satellite in synchronization.
It is meant that in the visual angle of one or one group satellite, the clock in any two place can use while receive same on the earth
Or the time signal of same group of satellite carry out time comparison.
Ideally, it is assumed that satellite receiver is respectively placed in two known locations A and B, observes in synchronization same
Satellite i.Then have:
The clock deviation formula (1) of Δ tiA=(ti-tA)=clock A and satellite i
The clock deviation formula (2) of Δ tiB=(ti-tB)=clock B and satellite i
Two formulas make the difference the clock deviation that can obtain two station A, B:
Δ tiA- Δ tiB=(ti-tA)-(ti-tB)=tB-tA=tAB formula (3)
If the clock time in the place A is tA, the clock time in the place B is tB, and satellite time is t satellite, and dA and dB arrive for satellite
A, the path delay of the two places B.The principle of precise measurement A, the B two places time difference is as follows:
The receiver of two places receives same satellite-signal in synchronization, receiver output is represented the second of satellite time
Pulse, the pulse per second (PPS) with the output of local clock compares, to obtain the time difference count value Δ tA of the two places A, B receiver and same satellite
Satellite and Δ tB satellite, are expressed as formula (4) and formula (5):
Δ tA satellite=tA- (t satellite+dA) formula (4)
Δ tB satellite=tB- (t satellite+dB) formula (5)
The data of the two places A, B are passed in the computer of other side by communication network, wherein dA and dB can pass through Satellite
It goes through and is calculated, then formula (4) and formula (5) subtract each other the time difference that can be obtained between two places, as shown in formula (6).
Δ tA satellite-Δ tB satellite=(tA-t satellite-dA)-(tB-t satellite-dB)=(tA-tB)-(dA-dB) formula (6)
Therefore, satellite common vision can remove the influence of Satellite clock, and eliminating most path additional time delay influences.
Satellite common vision receiver can receive GPS/ Big Dipper satellite signal, meanwhile, the satellite-signal that transmitting terminal is received
It is compared with the satellite-signal that receiving end receives, obtains the clock deviation between transmitting terminal and receiving end, then transmitting terminal is according to altogether
Find out offset depending on algorithm and be issued to receiving end, its rubidium clock second is constantly corrected according to the value in receiving end, it is final generate with
The total view second signal of transmitting terminal synchronization accuracy < 5ns.
Satellite common vision flow chart of data processing is as shown in fig. 6, its main flow is as follows:
(1) transmitting terminal/receiving end clock deviation calculates；
(2) receiving end uploads its clock deviation data to transmitting terminal；
(3) transmitting terminal motor synchronizing and issue receiving end amendment data；
(4) receiving end motor synchronizing；
(5) transmitting terminal and receiving end choose optimal satellite and carry out data acquisition, and calculate data；
(6) data, which calculate to finish, is followed by the data that receiving end uploads receiving end to transmitting terminal；
(7) transmitting terminal receives receive end data after regard satellite using total as the time complexity curve amount of criterion calculation receiving end and issue
To receiving end；
(8) receiving end synchronizes the accurate phase shift of progress of local second after receiving amendment data, is finally completed the total view of receiving end
Second output；
(9) the local second (atomic clock second) of transmitting terminal real-time measurement and receiver refer to the time difference of second, and are sent to time difference benefit
Unit is repaid, the tight tracking of local second and reference second are finally completed and generates the total view second of transmitting terminal.
This method is used by receiving-transmitting sides clock signal and is realized with the high precision clock of frequency, such as eats clock or caesium clock.
Embodiment 1:
Radiofrequency signal distance transmission system (be applicable in transmission range 100km within) composition based on optical fiber as shown in fig. 7,
The radiofrequency signal that the system is applied between nine institute's Beidou ground test computer room (Beijing) of space flight and space flight Fifth Academy of Aerospace Industry satellite workshop is remote
Distance Transmission.The system includes that main side computer room samples restorer, samples restorer, transmission line (single-mode optics from terminal room
It is fine), atomic clock, main side computer room clock recovery apparatus, from terminal room clock recovery apparatus.The main side computer room is nine institute of space flight north
Struggle against ground test computer room；It is space flight Fifth Academy of Aerospace Industry satellite workshop from terminal room.
The atomic clock of main side computer room provides 10MHz and 1PPS reference time frequency signal for clock recovery apparatus；It is extensive by clock
Multiple equipment makes main and slave terminal use synchronous second pulse signal as time reference, main and slave terminal is made to sample restorer
Start to execute movement in synchronization；Main and slave terminal uses the sampled clock signal of same frequency as frequency reference；Make main side and
Sampling from end sampling restorer is identical as clock signal frequency used is restored.
Radio signal transmission is shown in detailed process is as follows:
(1) radiofrequency signal to be transmitted enters transmitting terminal sampling restorer, which completes radiofrequency signal
Down coversion and ADC sampling, and filtering, extraction, digital AGC, quantization are sequentially completed according to radiofrequency signal bandwidth；
(2) for transmitting terminal by the digital signal handled according to the format group packet of agreement, every packet length is identical；Every number
Include packet header and the channel digital signal according to packet, middle wrapping head includes packet serial number (for the filling of subsequent packet loss, out-of-order rearrangement), leads to
Taoist monastic name (for receiving end demultiplexing subchannel processing), timestamp (for counting propagation delay time), bit quantization digit are (for solving
Packet), the timestamp is the corresponding sampling instant of N number of channel digital signal；
(3), it after receiving transmission control instruction (receiving end obtains receive control instruction in the same time), opens to send and enable,
It is a channel by the data packet time division multiplexing in each channel, time division multiplexing strategy is by the way of timeslice poll, Mei Getong
There is identical priority in road, successively poll.If some channel data is ready to, the data in the channel are just sent, if inaccurate standby
It is good, just skip the channel.After one bag data has been sent, it is switched to next channel.
(4) serial data after channel multiplexing is converted to by standard commercial optical module (such as 10Gbps optical module)
Optical signal is sent to receiving end by single mode optical fiber；
(5) it receives optical signal and serial data is converted to by standard commercial optical module (such as 10Gbps optical module)；
(6) solve channel number in the packet header of each packet of serial data, exported respectively according to channel number to N number of channel into
Row parsing；
(7) data packet in each channel is sent respectively to the reception buffer area FIFO in each channel, in the packet header of each packet
In solve packet serial number, out-of-order reset and packet loss filling is (due to will lead to out-of-order and packet loss in transmission process is carried out according to packet serial number
Generation, therefore receiving end data packet must be carried out rearrangement and packet loss supplement, with guarantee propagation delay time stablize), obtain
Continuous data packet continuously without packet loss random ordering；
(8) after receiving reception control instruction (transmitting terminal obtains send control instruction in the same time), be delayed set time T (T
For the propagation delay time value of setting) it opens and receives enabled, bit quantization digit is solved in the packet header of each packet, is quantified according to bit
Digit unpacks；Interpolation (rising sampling) is successively carried out to the digital signal after unpacking, low-pass filtering (eliminates the high frequency occurred in frequency spectrum
Mirror image), D/A (D/A) conversion obtain intermediate-freuqncy signal；By intermediate-freuqncy signal up-conversion, the radiofrequency signal of transmission is finally recovered.
Embodiment 2:
Radiofrequency signal distance transmission system (being applicable in transmission range without limitation) composition such as Fig. 8 based on commercial data special line
Shown, which is applied to the radio frequency between nine institute's Beidou ground test computer room (Beijing) of space flight and Shanghai satellite workshop (Shanghai)
Signal transmits at a distance.The system includes that main side computer room samples restorer, samples restorer, transmission line from terminal room
(long-distance commercial data special line and two ends exchange machine), atomic clock, main side computer room satellite common vision receiver and antenna are defended from terminal room
Star common-view receiver and antenna.The main side computer room is nine institute's Beidou ground test computer room of space flight；It is Shanghai satellite from terminal room
Workshop.
The atomic clock of main side computer room provides 10MHz and 1PPS reference time frequency signal for satellite common vision receiver；It defends at both ends
Star common-view receiver receives Beidou or GPS satellite navigation signal by antenna, utilizes sampling restorer and commercial data special line
Clock deviation information is transmitted, realizes that both ends export 10MHz the and 1PPS signal of Time and Frequency Synchronization by satellite common vision method；Both ends sampling is extensive
The 10MHz and 1PPS that multiple equipment all uses satellite common vision receiver to export are as oneself reference clock, to keep master-salve clock
The consistency of frequency.
Radio signal transmission is shown in detailed process is as follows:
(1) radiofrequency signal to be transmitted enters sampling restorer, and sampling restorer completes the down coversion of radiofrequency signal
It is sampled with ADC, and filtering, extraction, digital AGC, bit quantization is sequentially completed according to radiofrequency signal bandwidth；
(2) by the digital signal handled according to the format group packet of agreement, every packet length is identical；Each data packet packet
Packet header and the channel digital signal are included, middle wrapping head includes packet serial number (for the filling of subsequent packet loss, out-of-order rearrangement), channel number
(for receiving end demultiplexing subchannel processing), timestamp (for counting propagation delay time), bit quantization digit (for unpacking),
The timestamp is the corresponding sampling instant of N number of channel digital signal；
(3) after receiving transmission control instruction (receiving end obtains receive control instruction in the same time) it, opens to send and enable, by
The data packet time division multiplexing in each channel is a channel, and time division multiplexing strategy is by the way of timeslice poll, each channel
There is identical priority, successively poll.If some channel data is ready to, the data in the channel are just sent, if not being ready to,
Just skip the channel.After one bag data has been sent, it is switched to next channel.
(4) serial data after channel multiplexing be packaged again according still further to standard UDP protocol and be encapsulated, sent to exchange
Machine is sent to receiving end by commercial data special line；
(5) it receives end switch output data and is converted to serial data according to standard UDP protocol unpacking；
(6) solve channel number in the packet header of each packet of serial data, exported respectively according to channel number to N number of channel into
Row parsing；
(7) data packet in each channel is sent respectively to the reception buffer area FIFO in each channel, in the packet header of each packet
In solve packet serial number, out-of-order reset and packet loss filling is (due to will lead to out-of-order and packet loss in transmission process is carried out according to packet serial number
Generation, therefore receiving end data packet must be carried out rearrangement and packet loss supplement, with guarantee propagation delay time stablize), obtain
Continuous data packet continuously without packet loss random ordering；
(8) after receiving reception control instruction (transmitting terminal obtains send control instruction in the same time), be delayed set time T (T
For the propagation delay time value of setting) it opens and receives enabled, bit quantization digit is solved in the packet header of each packet, is quantified according to bit
Digit unpacks；Interpolation (rising sampling) is successively carried out to the digital signal after unpacking, low-pass filtering (eliminates the high frequency occurred in frequency spectrum
Mirror image), D/A (D/A) conversion obtain intermediate-freuqncy signal；By intermediate-freuqncy signal up-conversion, the radiofrequency signal of transmission is finally recovered.
The above method can also transmit 1PPS signal.1PPS signal to be transmitted enters after sampling restorer, and sets
It is compared for the time synchronizing signal of itself, obtains the time difference between two signals.In the form of data by the time difference
The other end is transferred to by optical fiber and samples restorer, and other end sampling restorer adds on the time synchronizing signal of itself
The time difference, the 1PPS signal then restored in other end output.
Management and monitoring to sampling restorer are realized by upper computer software by Ethernet interface, achievable to radio frequency
Parameter configuration, bit quantization, propagation delay time control (setting propagation delay time T), transmitting-receiving enabled (assigning transmission instruction) etc., also can
Monitor transmission state, propagation delay time, packet loss, received signal power estimation etc..
It is not described in detail in this specification and partly belongs to common sense well known to those skilled in the art.
Claims (9)
1. a kind of radiofrequency signal remote transmission method, it is characterised in that the step of including the steps that transmitting terminal and receiving end,
In:
Steps are as follows for transmitting terminal:
(1), N number of channel radiofrequency signal to be transmitted is subjected to down coversion and obtains intermediate-freuqncy signal, later to intermediate-freuqncy signal carry out mould/
Number conversion, low-pass filtering, extraction, digital AGC, quantification treatment, obtain N number of channel digital signal, N >=1；
(2), N number of channel digital signal is packaged and constitutes N number of channel data packet, each channel data packet includes packet header and corresponds to logical
Road digital signal, middle wrapping head include packet serial number, channel number, timestamp, quantization digit, and the timestamp is that channel data packet is beaten
It wraps the moment, the packet numeric order is incremented by；
(3), N number of channel data packet is formed serial data by time-division multiplexing method by transmitting terminal, and sends it to receiving end；
Receiving end parses the serial data received, N number of channel data packet is obtained, and according to channel number, by same channel data
Packet is stored to receiving in buffer area, and later, receiving end executes following steps to the channel data packet in each channel:
(4), channel data packet is parsed, packet serial number is obtained, according to packet serial number, the channel data packet received in buffer area is first carried out
Out-of-order rearrangement processing carries out packet loss filling again, obtains the continuous data packet of no packet loss random ordering, and stored to output buffer；
(5), the channel data packet in poll output buffer, parses timestamp information and quantization digit, with channel data packet
In time for indicating of timestamp on the basis of, postpone set time T, corresponding channel digital signal extracted according to quantization digit,
Interpolation, low-pass filtering, D/A switch and upconversion process are successively carried out to it, recover the radiofrequency signal of transmission.
2. a kind of radiofrequency signal remote transmission method according to claim 1, it is characterised in that the transmitting terminal with connect
Receiving end has synchronous reference time frequency signal, and the reference time frequency signal includes clock signal and second pulse signal, clock signal
For guaranteeing that transmitting terminal is synchronous with the sampling clock of receiving end, pulse per second (PPS) is used to guarantee the time synchronization of transmitting terminal and receiving end.
3. a kind of radiofrequency signal remote transmission method according to claim 1, it is characterised in that the set time T is big
In maximum transmission time of the serial data from transmitting terminal to receiving end.
4. a kind of radiofrequency signal remote transmission method according to claim 2, it is characterised in that the transmitting terminal and connect
Receiving end is communicated by optical fiber or commercial data line.
5. a kind of radiofrequency signal remote transmission method according to claim 4, it is characterised in that when transmitting terminal and reception
When end is communicated by optical fiber, the reference time frequency signal of the synchronization is realized by the method that data clock restores.
6. a kind of radiofrequency signal remote transmission method according to claim 4, it is characterised in that when transmitting terminal and reception
When end is communicated by commercial data, the reference time frequency signal of the synchronization is realized by the method for satellite common vision.
7. a kind of radiofrequency signal remote transmission method according to claim 1, it is characterised in that the random ordering in step (4)
Reset treatment process are as follows:
(4.1), according to the principle of first in, first out, the channel data packet received in buffer area is extracted, deposit can accommodate M
In first extra buffer of channel data packet, the M is greater than the maximum after the channel data packet random ordering of two neighboring packet serial number
Spacing, and the value for initializing expected packet serial number is 0；
(4.2), according to the value of expected packet serial number, the packet header of each channel data packet in the first extra buffer is traversed, to look into
The corresponding channel data packet of expected packet serial number is seen whether in the first extra buffer, if expected packet serial number is corresponding logical
It is interim that the channel data packet is read deposit second by track data packet in the first extra buffer, then from the first extra buffer
In buffer area, then next channel data packet being read from reception buffer area and being inserted in the first extra buffer, filling position is
For the position of newest read-out channel data packet, (4.3) are entered step, otherwise, are directly entered step (4.3)；
(4.3), expected packet serial number is updated, is repeated step (4.2)~step (4.3), until the whole received in buffer area is logical
Track data packet is all disposed.
8. a kind of radiofrequency signal remote transmission method according to claim 7, it is characterised in that step is lost described in (4)
Packet filling treatment process are as follows:
(4.4), it is successively read channel data packet from the second extra buffer, judges current channel data packet serial number and expects Bao Xu
It is number whether identical, it is identical, then current channel data packet is stored in output buffer, enters step (4.5)；Otherwise, it will be considered that have
Packet drop occurs, and inserting a bag data at this time is the data packet of full 0 to output buffer, enters step (4.5)；
(4.5), expected packet serial number is updated, is repeated step (4.4)~step (4.5), until by the channel in second buffering area
Data packet is all arranged in output buffer.
9. a kind of radiofrequency signal remote transmission method according to claim 7, it is characterised in that in affiliated step (5) with
On the basis of the time that timestamp in channel data packet indicates, delay set time T's method particularly includes: firstly, in same a period of time
It carves, send control instruction data packet to transmitting terminal and receiving end respectively and receives director data packet, transmitting terminal is receiving
When receiving a second pulse signal after transmission control instruction data packet, starts to acquire the data after AD is converted and organize packet transmission；
Receiving end then receive receive control instruction after receive a second pulse signal after, on the basis of pulse per second (PPS), wait fixed delay T
Start for the channel digital signal in output buffer to be sent to D/A converter progress DA conversion again, within this period of waiting,
If receiving end has received the data that transmitting terminal is sent, then it is temporarily stored in output buffer and carries out DA turns without being sent to D/A converter
It changes.
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| CN114430302A (en) * | 2020-10-29 | 2022-05-03 | 南京中兴新软件有限责任公司 | Time synchronization method and device |
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