CN108551378A - A kind of radiofrequency signal remote transmission method - Google Patents
A kind of radiofrequency signal remote transmission method Download PDFInfo
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- CN108551378A CN108551378A CN201810128312.9A CN201810128312A CN108551378A CN 108551378 A CN108551378 A CN 108551378A CN 201810128312 A CN201810128312 A CN 201810128312A CN 108551378 A CN108551378 A CN 108551378A
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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 terminal；Receiving terminal stores same channel data packet into reception buffering area, later, with according to packet serial number, out of order rearrangement processing is first carried out to the channel data packet in reception buffering area and carries out packet loss filling again, obtain the out of order continuous data packet of no packet loss, 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, to it successively into row interpolation, low-pass filtering, D/A switch, upconversion process, the radiofrequency signal of transmission is finally recovered.
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 experiment and other space mission Major Ground Tests, belong to technical field of electronic communication.
Background technology
With the construction of Chinese Beidou satellite navigation system, gradually from No. two area navigation systems of the Big Dipper of the service Asian-Pacific area
System develops into No. three Global Navigation Systems of the Big Dipper of Service Global, and maximum variation is exactly to introduce inter-satellite link technology, will
Multi-satellite interconnects information transmission and the exchange realized together between satellite, 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.It improves and measures track and time service precision, and reduce the dependence to ground cloth station, effectively reduce the operation pipe of system
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 experiment can not complete inter-satellite link network layer and protocol layer authentication, it is necessary to open
The more star multilink synthesis docking experiments of exhibition.However the space flight Fifth Academy of Aerospace Industry of Liang Jia satellites 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 experiment of development and unrealistic, need to solve remote (the thousands of public affairs of radiofrequency signal
In) transmission could realize more star multilinks strange land synthesis dock test.
The special large-scale ground of dipper system tests system Construction in nine institute's computer room of space flight, apart from space flight Fifth Academy of Aerospace Industry satellite workshop
Several kilometers, apart from more than 1,000 kilometer of Shanghai satellite workshop, a kind of radiofrequency signal remote transmission method is needed, could realize space flight
Nine institute's Big Dipper ground testing systems and space flight Fifth Academy of Aerospace Industry satellite workshop, more star multilinks synthesis pair of Shanghai satellite workshop satellite to be measured
Experiment 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 adapting to simulated light debugging signal by increase is put
Big device realizes that relay transmission, maximum transmission distance can reach 200~300km, but individually lays single mode optical fiber and build suitable
The of 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.
Invention content
The technology of the present invention solves the problems, such as：For above-mentioned dipper system mission requirements, a kind of radiofrequency signal long distance is proposed
From transmission method, solve the problems, such as that dipper system carries out the more star multilink synthesis docking in strange land.
Technical solution of the invention is：A kind of radiofrequency signal remote transmission method, this method include transmitting terminal
The step of step and receiving terminal, 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；
(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
It includes packet serial number, channel number, timestamp, quantization digit to answer channel digital signal, middle wrapping head, 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 transmitting terminal by time-division multiplexing method, and is sent it to and connect
Receiving end；
Receiving terminal 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 buffering area, and later, receiving terminal 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 receiving the channel data packet in buffering area according to packet serial number
It carries out out of order rearrangement processing and carries out packet loss filling again, obtain the out of order continuous data packet of no packet loss, 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, to it successively into row interpolation, low-pass filtering, D/A switch and upconversion process, recover the radiofrequency signal of transmission.
The transmitting terminal has synchronous reference time frequency signal with receiving terminal, and the reference time frequency signal includes clock signal
And pps pulse per second signal, clock signal are used for ensureing that transmitting terminal is synchronous with the sampling clock of receiving terminal, pulse per second (PPS) is sent for ensureing
The time synchronization at end and receiving terminal.
The set time T is more than maximum transmission time of the serial data from transmitting terminal to receiving terminal.
The transmitting terminal and receiving terminal are communicated by optical fiber or commercial data line.
When transmitting terminal and receiving terminal 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 terminal 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 processing procedure in step (4) is：
(4.1), according to the principle of first in, first out, the channel data packet received in buffering area is extracted, deposit can be held
Receive in the first extra buffer of M channel data packet, the M be more 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 corresponds to
Channel data packet in the first extra buffer, then the channel data packet is read from the first extra buffer to deposit second
In extra buffer, then reads next channel data packet from reception buffering area and insert 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, step (4.2)~step (4.3) is repeated, until receiving complete in buffering area
Portion's channel data packet is all disposed.
Packet loss described in step (4) fills processing procedure：
(4.4), it is successively read channel data packet from the second extra buffer, judges current channel data packet serial number and expects
Whether packet serial number is identical, identical, then current channel data packet is stored in output buffer, entered step (4.5)；Otherwise, will recognize
To there is packet drop appearance, insert at this time a bag data be full 0 data packet to output buffer, enter step (4.5)；
(4.5), expected packet serial number is updated, step (4.4)~step (4.5) is repeated, 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 is：First, in synchronization, control instruction data packet is sent to transmitting terminal and receiving terminal respectively and receive director data
Packet, transmitting terminal start when receiving a pps pulse per second signal after receiving transmission control instruction data packet after acquiring AD conversions
Data and organize packet send；Receiving terminal then receive receive control instruction after receive a pps pulse per second signal after, be with pulse per second (PPS)
Benchmark waits for fixed delay T to start the channel digital signal in output buffer being sent to D/A converter progress DA conversions again,
In this period of waiting, if receiving terminal 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 conversions are carried out toward D/A converter.
Compared with the prior art, the invention has the advantages that：
(1), the present invention is using the method for adding data receiver buffering area in receiving terminal, when solving the transmission in fiber optic communication
Prolong instability problem.
(2), the present invention solves the problems, such as transmission packet packet loss using packet loss fill method.
(3), the present invention solves the problems, such as that transmission packet is out of order using in out of order rearrangement method.
Description of the drawings
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 the out of order rearrangement flow of transmission packet of the embodiment of the present invention；
Fig. 4 is that transmission packet packet loss of the embodiment of the present invention fills flow；
Fig. 5 is propagation delay time control principle of the embodiment of the present invention；
Fig. 6 is satellite common vision Data processing of receiver flow of the embodiment of the present invention；
Fig. 7 is radiofrequency signal distance transmission system composition of the embodiment of the present invention based on optical fiber；
Fig. 8 is radiofrequency signal distance transmission system composition of the embodiment of the present invention based on commercial data special line.
Specific implementation mode
Below in conjunction with specific embodiment and Figure of description, the present invention is described in detail.
When it is within 100km that radiofrequency signal, which needs transmission range, (such as in same city), laying or rental single mode are naked
Optical fiber cost is relatively low, and can recover Time-Frequency Information from the data that optical fiber transmits；Transmitting terminal utilizes acquisition restorer
Modulus (A/D) converter converts analog radio-frequency signal to be transmitted to digital signal, is transmitted in single mode bare fibre, receiving terminal
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 terminal 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 radio frequency link synthesis docking experiment.
When it is hundreds of kms or more that radiofrequency signal, which needs transmission range, (such as in different cities), 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 satellite common vision side may be used
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
Converter converts analog radio-frequency signal to be transmitted to digital signal, is transmitted in commercial data special line, and receiving terminal is utilized and adopted
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 terminal and recovered clock, utilizes satellite common vision technology
It realizes strange land Time and Frequency Synchronization, identical clock is used 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 experiment.But commercial data special line transmission data time delay is unstable, in fact it could happen that transmission packet packet loss and out of order.
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, it is proposed that a kind of radiofrequency signal remote transmission method, this method add data receiver buffering area using receiving terminal
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 more than 100km) transmission of commercial data special line is realized using satellite common vision method.Using
The method achieve nine institute's Big Dipper 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
More star multilinks synthesis docking experiment of satellite, effectively demonstrates No. three inter-satellite link network layers of the Big Dipper and protocol layer, to the Big Dipper
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 terminal
Suddenly, the transmitting terminal has synchronous reference time frequency signal with receiving terminal, and the reference time frequency signal includes clock signal and second
Pulse signal, clock signal for ensureing that transmitting terminal is synchronous with the sampling clock of receiving terminal, use by pps pulse per second signal (1PPS signals)
In the time synchronization for ensureing transmitting terminal and receiving terminal.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 for anti-signal aliasing, extracts and is used for realizing the down-sampled of signal, and digital AGC is used for realizing 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 digits are 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 digits are transmitted.
Quantify the strategy used to be transmitted for the interception A/D high positions sent, the mode that low level is directly cast out, such as using
4bit quantifies, then only intercepts high 4bit, low 8bit directly casts out.When receiving terminal reverts to the 12bit data for giving D/A, then
It need to be in low 8bit zero paddings.
As a result of quantization strategy, it is therefore desirable to carry out digital AGC, signal is amplified to full scale as possible, to ensure
The case where signal amplitude is less than quantizing range will not be gone out when bit quantifies.AGC modules carry out work(to the signal that sampling is come in first
Rate is estimated, the amplitude size of itself and full scale signal is compared；If signal power is much smaller than full scale signal amplitude, amplify letter
Number, ensure 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
It includes packet serial number, channel number, timestamp, quantization digit to answer channel digital signal, middle wrapping head, and the timestamp is channel data
Packet is packaged the moment；
After starting transmission, transmitting terminal often sends a data packet, and 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 interval is few, in each data packet
Including data time is long；Quantization digit is high, and the data packet in the unit interval is more, short comprising data time in each data packet.
(3), N number of channel data packet is formed serial data by transmitting terminal by time-division multiplexing method, and is sent it to and connect
Receiving end.Specially：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 interval, 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 interval, and poll often has data packet transmission.
As depicted in figs. 1 and 2, the transmitting terminal and receiving terminal can be communicated by optical fiber or commercial data line.Work as biography
When defeated circuit is single mode optical fiber, serial data is converted to optical signal by standard commercial optical module (such as 10Gbps optical modules),
It is sent to receiving terminal 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 terminal is sent to by commercial data special line.
Receiving terminal 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 buffering area (FIFO)；
When transmission line is single mode optical fiber, receiving terminal 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 terminal 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 receiving the channel data packet in buffering area according to packet serial number
It carries out out of order rearrangement processing and carries out packet loss filling again, obtain the out of order continuous data packet of no packet loss, and stored slow to output
Rush area.
Due to that can cause out of order and packet loss generation, receiving terminal that must again be arranged data packet in transmission process
Sequence and packet loss supplement, to ensure that propagation delay time is stablized.
Receiving terminal safeguards an expectation packet serial number register, and after often receiving a data packet, which increases 1 certainly.Data
It is as shown in Figure 3 to wrap out of order rearrangement processing procedure：
(4.1), according to the principle of first in, first out, the channel data packet received in buffering area is extracted, deposit can be held
It receives in the first extra buffer (such as RAM) of M channel data packet, the M is more than the channel data packet of two neighboring packet serial number
Maximum spacing after out of order, 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 corresponds to
Channel data packet in the first extra buffer, then the channel data packet is read from the first extra buffer to deposit second
In extra buffer, then reads next channel data packet from reception buffering area and insert 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, step (4.2)~step (4.3) is repeated, until receiving complete in buffering area
Portion's channel data packet is all disposed..
It is as shown in Figure 4 that data packet packet loss fills processing procedure：
(4.4), it is successively read channel data packet from the second extra buffer, judges current channel data packet serial number and expects
Whether packet serial number is identical, identical, then current channel data packet is stored in output buffer, entered step (4.5)；Otherwise, will recognize
To there is packet drop appearance, insert at this time a bag data be full 0 data packet to output buffer, enter step (4.5)；
(4.5), expected packet serial number is updated, step (4.4)~step (4.5) is repeated, 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 digits, 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 digits
Digital signal obtains intermediate-freuqncy signal into row interpolation, low-pass filtering, D/A switch successively to it, then by intermediate-freuqncy signal up-conversion,
The final radiofrequency signal for recovering transmission, the set time T are more than maximum transmitted of the serial data from transmitting terminal to receiving terminal
Time.
Due to affected by various factors in the transmission process of data packet, the end-to-end time delay of data packet wave can be caused
It is dynamic.In order to realize that propagation delay time accurately controls, therefore need to be ensured by a kind of mechanism from number transmitting terminal A/D to receiving terminal 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, the specific method of delay set time T is：It is first
First, in synchronization, control instruction data packet is sent to transmitting terminal and receiving terminal respectively and receive director data packet, sent
End starts to acquire the data after AD is converted simultaneously when receiving a pps pulse per second signal after receiving transmission control instruction data packet
Group packet is sent；Receiving terminal then receive receive control instruction after receive a pps pulse per second signal after, on the basis of pulse per second (PPS), wait for
Fixed delay T starts the channel digital signal in output buffer being sent to D/A converter progress DA conversions again, in this of waiting
In the section time, if receiving terminal has received the data that transmitting terminal is sent, then it is temporarily stored in output buffer without being sent to DA conversions
Device carries out DA conversions.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 terminal is enabled draws high, the data for starting to receive are sent to D/A.
According to this operation, start after D/A transmission datas in receiving terminal, as long as the data in buffering area FIFO are not empty not
Full, then the propagation delay time from A/D to D/A remains fixed delay T, to realize the stringent control of propagation delay time.Due to
The clock frequency of A/D and D/A samplings is strictly with frequency, therefore the data in normal transmission, buffering area FIFO 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 more than the propagation delay time of transmitting-receiving two-end data packet, so as to
When receiving terminal, which is opened, receives enabled, there are data in buffering area FIFO；(2) time delay cannot be too big, to prevent from opening in receiving terminal
When receiving enabled, buffering 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 if the clock reference frequency different frequencies that transmitting terminal and receiving terminal use, the reception of receiving terminal buffers
Area FIFO reads empty or overflows, and can cause to restore spectrum of radio frequency signals distortion.Pulse per second (PPS) be used to ensure transmitting terminal and receiving terminal when
Between it is synchronous, so that transmitting terminal and receiving terminal is sampled restorer and start to execute action in synchronization, if transmitting terminal and receiving terminal
The time irreversibility used, can lead to the non-setting value of radio signal transmission time delay, the reception buffering area FIFO of receiving terminal read it is empty or
It overflows.
When transmitting terminal and receiving terminal 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 circuitries of FPGA high speed serial transceivers into
Row.
The 10Gbps serial digital signals that optical fiber is sent are 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 clock jitter of the 10GHz clocks and source that are recovered under 10Gbps rates is less than 100ps, however when 10GHz
Clock need to can just obtain the 10MHz clocks needed for sampling restorer after dividing twice, and divide operation can cause to connect twice for this
There is deviation in the 10MHz clocks of receiving end and the 10MHz clock phases of transmitting terminal.
The work clock of the high speed serialization transceiver of FPGA is 250MHz, and the 250MHz clocks of transmitting terminal are directly by 10MHz
Frequency multiplication obtains, therefore there is no the uncertainties of phase；The 250MHz clocks that receiving terminal restores are due to being divided from 10GHz
, therefore with the 250MHz clocks of transmitting terminal there are phase indeterminacy, it is Δ T1 to count the time.After obtaining 250MHz clocks,
It need to divide again to 10MHz so that sampling restorer uses, introduce phase indeterminacy again at this time, it is Δ T2 to count the time.
The core that recovered clock keeps phase to determine is to eliminate Δ T1 and Δ T2, makes the phase error that it is contributed 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 terminal when receiving data, can confirm the boundary of serial data, to carry out serial number by comma alignment first
According to the conversion to parallel data.
The high speed serialization transceiver of FPGA when carrying out comma alignment, can record comma alignment at the time of relative to
The delay of 250MHz rising edges, 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 terminal 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
Go out the value.Then by the phase shift function of FPGAMMCX, according to the digital baseband input signal of reading, by the 250MHz clock phases of receiving terminal
It is moved to identical with transmitting terminal.After the processing, the 250MHz of transmitting-receiving two-end can reach with phase precision within 100ps.
In clock phase alignment, 1PPS is mainly used for being aligned the 10MHz phases of transmitting terminal and receiving terminal.It has eliminated before
Phase does not know Δ T1, and eliminates Δ T2 and then need transmitting terminal and receiving terminal there are one time reference, which is
Synchronous 1PPS.
Transmitting terminal generates the 1PPS pulses under a 250MHz clock domain, is sent to receiving terminal in the rising edge of 10MHz.
The pulse is after optical fiber transmits, when recovering the 250MHz of 1PPS pulses and transmitting terminal by same data clock restoration methods
Clock, so as to generate the high speed serialization Transceiver Clock for the receiving terminal 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 pulses, after plaing a bat by local 250MHz clocks,
It has obtained differing the 1PPS for being fixed as 4ns with transmitting terminal, the as 1PPS of receiving terminal.
1PPS after the finally obtained adjustment of receiving terminal differs fixed 4ns with the rising edge of transmitting terminal 10MHz.Therefore should
1PPS can be used for being aligned for subsequent receiving terminal 10MHz and transmitting terminal 10MHz.
Front has been obtained for the 250MHz clocks and 1PPS with phase with transmitting terminal, need in next step through the clock and
1PPS obtains the 10MHz clocks with phase with transmitting terminal.
Receiving terminal divides the 250MHz clocks after adjustment to 10MHz by MMCX, which can introduce phase error Δ
T2.By the 250MHz clock domain down-samplings of the 10MHz clocks after frequency dividing after the adjustment, this makes it possible to obtain the risings of 10MHz clocks
Edge.Then under 250MHz clock domains after the adjustment, the rising edge of 10MHz and the 1PPS after adjustment are subjected to phase bit comparison, it can
Obtain the phase difference between the 1PPS after receiving terminal 10MHz clocks and adjustment.And due to the 1PPS and transmitting terminal 10MHz after adjustment
Phase fix, therefore this phase difference can reflect the phase difference of the 10MHz and transmitting terminal 10MHz of receiving terminal.
Then, according to obtained phase difference, by 10MHz clocks by the MMCX phase shifts of FPGA to and transmitting terminal 10MHz phases
Position is identical, then receiving terminal has just obtained the reference clock with phase with transmitting terminal 10MHz.The in-phase clock sampling is supplied again to restore
Equipment uses, you can ensures that the sampling clock phase relationship of transmitting terminal and receiving terminal determines.
When transmitting terminal and receiving terminal 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, and same or same group of satellite are observed in synchronization.
It is meant that in the visual angle of one or one group satellite, the clock in any two place can be utilized while be received same on the earth
Or the time signal of same group of satellite carry out Time transfer receiver.
Ideally, it is assumed that satellite receiver is respectively placed in two known locations A and B, is observed in synchronization same
Satellite i.Then have：
The clock correction formula (1) of Δ tiA=(ti-tA)=clock A and satellite i
The clock correction formula (2) of Δ tiB=(ti-tB)=clock B and satellite i
Two formulas make the difference the clock correction that can obtain two station A, B：
Δ tiA- Δs tiB=(ti-tA)-(ti-tB)=tB-tA=tAB formulas (3)
If the clock time in the places A is tA, the clock time in the places B is tB, and satellite time is t satellites, and dA and dB arrive for satellite
A, the path delay of the two places B.The accurate principle for measuring A, 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 satellites, are expressed as formula (4) and formula (5)：
Δ tA satellites=tA- (t satellites+dA) formula (4)
Δ tB satellites=tB- (t satellites+dB) formula (5)
The data of the two places A, B are passed to by communication network in the computer of other side, 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 satellites-Δ tB satellites=(tA-t satellites-dA)-(tB-t satellites-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 signals, meanwhile, the satellite-signal that transmitting terminal is received
It is compared with the satellite-signal that receiving terminal receives, obtains the clock correction between transmitting terminal and receiving terminal, then transmitting terminal is according to altogether
Find out offset depending on algorithm and be issued to receiving terminal, receiving terminal constantly corrects its rubidium clock second according to the value, it is final generate with
Transmitting terminal synchronization accuracy<5ns's regards second signal altogether.
Satellite common vision flow chart of data processing is as shown in fig. 6, its main flow is as follows：
(1) transmitting terminal/receiving terminal clock correction calculates；
(2) receiving terminal uploads its clock correction data to transmitting terminal；
(3) transmitting terminal motor synchronizing and issue receiving terminal correct data；
(4) receiving terminal motor synchronizing；
(5) transmitting terminal and receiving terminal 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 terminal to transmitting terminal；
(7) transmitting terminal receive receive end data after to regard satellite altogether as the time complexity curve amount of criterion calculation receiving terminal and issue
To receiving terminal；
(8) receiving terminal carries out accurate phase shift synchronization after receiving amendment data to the local second, is finally completed regarding altogether for receiving terminal
Second output；
(9) transmitting terminal measures local second (atomic clock second) and refers to the time difference of second with receiver in real time, and is sent to time difference benefit
Repay unit, be finally completed the local second with reference to the second tight tracking and generate transmitting terminal altogether regard the second.
This method uses the high precision clock with frequency to realize by receiving-transmitting sides clock signal, 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 Big Dipper 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 main side computer room sampling 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 signals for clock recovery apparatus；It is extensive by clock
Multiple equipment makes main and slave terminal use synchronous pps pulse per second signal as time reference, main and slave terminal is made to sample restorer
Start to execute action 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.
The detailed process of radio signal transmission is as follows：
(1) radiofrequency signal to be transmitted enters transmitting terminal sampling restorer, which completes radiofrequency signal
Down coversion and ADC samplings, 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
According to including packet header and the channel digital signal, middle wrapping head includes packet serial number (for the filling of follow-up packet loss, out of order rearrangement), logical
Taoist monastic name (for the processing of receiving terminal demultiplexing subchannel), timestamp (for counting propagation delay time), bit quantization digits 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 terminal 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 modules)
Optical signal is sent to receiving terminal 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 modules)；
(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 buffering area FIFO in each channel, in the packet header of each packet
In solve packet serial number, according to packet serial number carry out it is out of order rearrangement and packet loss filling (since out of order and packet loss can be caused in transmission process
Generation, therefore receiving terminal data packet must be carried out rearrangement and packet loss supplement, with ensure propagation delay time stablize), obtain
Continuously without the out of order continuous data packet of packet loss；
(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 digits are solved in the packet header of each packet, are quantified according to bit
Digit unpacks；(high frequency occurred in frequency spectrum is eliminated into row interpolation (rising sampling), low-pass filtering to the digital signal after unpacking successively
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 Big Dipper ground test computer room (Beijing) of space flight and Shanghai satellite workshop (Shanghai)
Signal transmits at a distance.The system includes main side computer room sampling 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 Big Dipper 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 signals for satellite common vision receiver；It defends at both ends
Star common-view receiver receives the Big Dipper or GPS satellite navigation signal by antenna, utilizes sampling restorer and commercial data special line
Clock correction information is transmitted, realizes that both ends export 10MHz the and 1PPS signals 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 the reference clock of oneself, to keep master-salve clock
The consistency of frequency.
The detailed process of radio signal transmission 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 quantizations is sequentially completed according to radiofrequency signal bandwidth；
(2) identical per packet length by the digital signal handled according to the format group packet of agreement；Each data packet packet
Packet header and the channel digital signal are included, middle wrapping head includes packet serial number (for the filling of follow-up packet loss, out of order rearrangement), channel number
(for the processing of receiving terminal demultiplexing subchannel), timestamp (for counting propagation delay time), bit quantization digits (for unpacking),
The timestamp is the corresponding sampling instant of N number of channel digital signal；
(3) after receiving transmission control instruction (receiving terminal 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 according still further to standard UDP protocol be packaged again and be encapsulated, sent to exchange
Machine is sent to receiving terminal 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 buffering area FIFO in each channel, in the packet header of each packet
In solve packet serial number, according to packet serial number carry out it is out of order rearrangement and packet loss filling (since out of order and packet loss can be caused in transmission process
Generation, therefore receiving terminal data packet must be carried out rearrangement and packet loss supplement, with ensure propagation delay time stablize), obtain
Continuously without the out of order continuous data packet of packet loss；
(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 digits are solved in the packet header of each packet, are quantified according to bit
Digit unpacks；(high frequency occurred in frequency spectrum is eliminated into row interpolation (rising sampling), low-pass filtering to the digital signal after unpacking successively
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 signals.1PPS signals to be transmitted enter after sampling restorer, and set
The standby time synchronizing signal of itself is compared, and obtains the time difference between two signals.In the form of data by the time difference
It is transferred to the other end by optical fiber and samples restorer, other end sampling restorer adds on the time synchronizing signal of itself
The time difference, the 1PPS signals then restored in other end output.
The management and monitoring that sample restorer are realized by upper computer software by Ethernet interface, can be completed to radio frequency
Parameter configuration, bit quantizations, 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 terminal,
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 transmitting terminal by time-division multiplexing method, and sends it to receiving terminal；
Receiving terminal 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 buffering area, and later, receiving terminal 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, is first carried out to receiving the channel data packet in buffering area
Out of order rearrangement processing carries out packet loss filling again, obtains the out of order continuous data packet of no packet loss, 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,
To it successively into row interpolation, low-pass filtering, D/A switch and upconversion process, the radiofrequency signal of transmission is recovered.
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 pps pulse per second signal, clock signal
For ensureing that transmitting terminal is synchronous with the sampling clock of receiving terminal, pulse per second (PPS) is used to ensure the time synchronization of transmitting terminal and receiving terminal.
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 terminal.
4. a kind of radiofrequency signal remote transmission method according to claim 1, 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 out of order in step (4)
Resetting processing procedure is：
(4.1), according to the principle of first in, first out, the channel data packet received in buffering area is extracted, deposit can accommodate M
In first extra buffer of channel data packet, the maximum after the M is out of order more than the channel data packet 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 then to be read deposit second in the first extra buffer by track data packet from the first extra buffer for the channel data packet
It in buffering area, then reads next channel data packet from reception buffering area and inserts 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, step (4.2)~step (4.3) is repeated, until the whole received in buffering 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 fills processing procedure：
(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, entered step (4.5)；Otherwise, it will be considered that have
Packet drop occur, insert at this time a bag data be full 0 data packet to output buffer, enter step (4.5)；
(4.5), expected packet serial number is updated, step (4.4)~step (4.5) is repeated, 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, the specific method of delay set time T is：First, in same a period of time
It carves, send control instruction data packet to transmitting terminal and receiving terminal respectively and receives director data packet, transmitting terminal is receiving
When receiving a pps pulse per second signal after transmission control instruction data packet, starts to acquire the data after AD is converted and organize packet transmission；
Receiving terminal then receives receive control instruction after receive a pps pulse per second signal after, on the basis of pulse per second (PPS), wait for fixed delay T
Start the channel digital signal in output buffer being sent to D/A converter progress DA conversions again, within this period of waiting,
If receiving terminal 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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