CN105680970B - Radio astronomy array remote fiber synchronization system and its method - Google Patents

Radio astronomy array remote fiber synchronization system and its method Download PDF

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Publication number
CN105680970B
CN105680970B CN201610025611.0A CN201610025611A CN105680970B CN 105680970 B CN105680970 B CN 105680970B CN 201610025611 A CN201610025611 A CN 201610025611A CN 105680970 B CN105680970 B CN 105680970B
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China
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local
clock
fiber
phase
module
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CN201610025611.0A
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Chinese (zh)
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CN105680970A (en
Inventor
宫新保
秦冕
臧小刚
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上海交通大学
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04JMULTIPLEX COMMUNICATION
    • H04J3/00Time-division multiplex systems
    • H04J3/02Details
    • H04J3/06Synchronising arrangements
    • H04J3/0635Clock or time synchronisation in a network
    • H04J3/0638Clock or time synchronisation among nodes; Internode synchronisation
    • HELECTRICITY
    • H03BASIC ELECTRONIC CIRCUITRY
    • H03LAUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00Automatic control of frequency or phase; Synchronisation
    • H03L7/06Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
    • H03L7/08Details of the phase-locked loop
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04JMULTIPLEX COMMUNICATION
    • H04J3/00Time-division multiplex systems
    • H04J3/02Details
    • H04J3/06Synchronising arrangements
    • H04J3/0635Clock or time synchronisation in a network
    • H04J3/0682Clock or time synchronisation in a network by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging

Abstract

A kind of radio astronomy array remote fiber synchronization system and its method, including:It is arranged at the phase-locked local control module of local node and is arranged at the clock cleaning module of remote node, wherein:Remote node is connected with local node by optical fiber, local reference clock and the local fiber received from clock cleaning module are received clock input phase-locked local control module by local node, horizontal phasing control is entered by PID control local reference clock and obtains local fiber tranmitting data register, so as to realize optical fiber temperature drift compensation, the present invention carries out optical fiber temperature drift compensation by digital form, with clock synchronization accuracy height, reach picosecond magnitude, strong environmental adaptability, cost is cheap, clock information is transmitted using digital form, strong antijamming capability, transmission range is grown, only optical fibre channel can it need to realize sampling clock all the way, sampled data, the transmission of system control instruction, it is achieved thereby that the system integration of height, reduce the complexity of optical fiber wiring.

Description

Radio astronomy array remote fiber synchronization system and its method

Technical field

The present invention relates to a kind of technology in low frequency radio astronomical telescope distributed antenna array field, is specifically one kind Radio astronomy array remote fiber synchronization system and its method.

Background technology

The object of observation of radio astronomy is the weak electromagnetic signal of astronomical radiation in wide universe.In order to lift astronomical sight Resolution ratio and the sensitivity of survey are, it is necessary to be continuously increased the antenna aperture of radio astronomy array.Modern radio astronomy array to It is extensive, over long distances, distributed direction develop, this is also proposed more to the remote clock net synchronization capability of radio astronomy array High requirement.The clock of modern radio astronomy array be synchronously mainly used in radio astronomy array sampling clock it is synchronous, it is necessary to Over long distances, high clock synchronization accuracy is realized between the array element node of its generally more than 1 kilometer of distance, generally in psec amount Level, to meet the sampling coherence requirement between array element node;Moreover, the array scale of modern radio astronomy array is huge, battle array First number of nodes is numerous, it is therefore desirable to the cost of implementation of relative moderate.

Remote clock simultaneous techniques is widely used in the fields such as network transmission, communication, radio astronomy.Different field for The synchronous required precision of clock is different, therefore the technology realization rate used is also variant.It is synchronous in field of network transmission, clock Precision usually require that it is not high, typically in millisecond magnitude, therefore mainly using based on NTP (Network Time Protocol, NTP) clock synchronizing method.In the communications field, the synchronous required precision of clock is typically in tens nanoseconds Magnitude, therefore clock synchronization mode of the generally use based on the wireless method of synchronization in spatial domain or based on GPS.And led in radio astronomy Domain, in order to realize the remote clock synchronization accuracy of picosecond magnitude, mode proper at present is fiber bit clock simultaneous techniques.

Fiber bit clock simultaneous techniques, i.e., clock recovery is carried out by the signal that is transmitted to optical fiber, in long-range receiving terminal by light The clock information transmitted on fibre extracts, and obtains the clock signal with local synchronization, realizes that remote clock is same with local clock Step.Because optical fiber has good transmission characteristic and cheap price, be especially suitable for radio astronomical telescope array it is remote, High precision clock is synchronous.But changed because by temperature change length can be occurred for fiber medium, in the case where optical fiber is longer, The clock of remote recovery can be caused to produce larger shake.

Found by the retrieval to prior art, L.J.Wang et al. is published in Nature periodicals Scientific in 2012 Paper " the Precise and Continuous Time and Frequency Synchronisation of the Report second phases at the 5×10-19Accuracy Level " are proposed in local node using atomic clock as clock source, by clock information Transmitted in the form of analog signal by optical fiber.The clock synchronization information received is fed back to local node by remote node, this Ground node is corrected according to the clock information of feedback to tranmitting data register, and remote synchronization clock zone is given with compensated optical fiber length change The shake come.But program equipment cost height, system complex, and the clock signal transmitted are analog signal, it is necessary to single light Fine tunnel.

Chinese patent literature CN104917582A, publication date is on 09 16th, 2015, when disclosing a kind of high-precision Clock distribute and phase automatic compensating system and its phase regulation method, the system include clock distribution module Master and it is multiple before Clock is distributed to multiple Slave by electronics node Slave, Master using optical fiber at end, wherein:Master by optical fiber by when Clock is sent to Slave, and Slave is received and clock is transferred back into Master again by optical fiber after clock, and Master is to clock Two-way time sum enters Mobile state measurement and obtains the delay up and down of clock, and sends the measurements to Slave, Slave according to Measurement result carries out dynamic phasing regulation to the clock received, Slave and Master is kept Phase synchronization.But the technology institute The synchronization accuracy that can reach can not meet the synchronous required precision of the sampling clock of radio astronomy array in tens picosecond magnitudes.

The content of the invention

The present invention is directed to deficiencies of the prior art, proposes a kind of radio astronomy array remote fiber synchronization system And its method.

The present invention is achieved by the following technical solutions:

The present invention relates to a kind of radio astronomy array remote fiber synchronization system, including:It is arranged at the local of local node Lock phase control module and the clock cleaning module for being arranged at remote node, wherein:Remote node and local node pass through optical fiber phase Even, local reference clock and the local fiber received from clock cleaning module are received clock input phase-locked local by local node Control module, horizontal phasing control is entered by PID control local reference clock and obtains local fiber tranmitting data register.

Described phase-locked local control module includes:First wave filter, the second wave filter, phase discriminator, analog-digital converter (ADC), digital signal processing unit and Direct Digital Frequency Synthesizers (DDS), wherein:Second wave filter, phase discriminator, ADC, DDS and digital signal processing unit are sequentially connected in series into loop, the first wave filter both ends and phase discriminator and local fiber receiving module It is connected, DDS is connected with local fiber sending module.

Described PID control refers to:Wherein u (n) is PID output controls Amount processed, e (n) are PID input quantities, KpFor proportionality coefficient, KiFor integral coefficient, KdFor differential coefficient.

Described remote node is provided with remote fiber sending module and remote fiber receiving module, and the remote fiber sends mould Block is connected with clock cleaning module and local fiber receiving module, the remote fiber receiving module and clock cleaning module and local Optical fiber sending module is connected.

Described digital signal processing unit and ADC is realized that local fiber receives by field programmable gate array (FPGA) Module and local fiber sending module are realized by FPGA high speed serialization transceiver (GTX).

The clock information received disappear by described clock cleaning module to be trembled processing and obtains remote synchronization clock, and instead It is fed back to local node.

The present invention relates to it is a kind of using above-mentioned radio astronomy array remote fiber synchronization system carry out temperature drift compensation method, Comprise the following steps:

Step 1, local reference clock and local fiber receive clock difference device after filtering, are then carried out by phase discriminator Phase demodulation;

Step 2, identified result is digitized by the analog-digital converter of low speed, is input to Digital Signal Processing list Member, handled by pid control algorithm, obtain phase-compensatory contro amount;

Step 3, phase-compensatory contro amount inputted into DDS, enter horizontal phasing control to local reference clock, obtain local fiber Tranmitting data register, realize optical fiber temperature drift compensation.

Technique effect

Compared with prior art, the present invention carries out optical fiber temperature drift compensation by digital form, has clock synchronization accuracy Height, reach picosecond magnitude, strong environmental adaptability, cost is cheap, and clock information, antijamming capability are transmitted using digital form By force, transmission range is grown, only need all the way optical fibre channel can realize the transmission of sampling clock, sampled data, system control instruction, It is achieved thereby that the system integration of height, reduces the complexity that optical fiber connects up.

Brief description of the drawings

Fig. 1 is principle of the invention structural representation;

Fig. 2 is that the present invention realizes structural representation;

The phase difference of local sampled signal and long-range sampled signal changes curve synoptic diagram when Fig. 3 is without temperature drift compensation;

Fig. 4 is that the phase difference of local sampled signal and long-range sampled signal changes curve synoptic diagram after temperature drift compensation.

Embodiment

Embodiments of the invention are elaborated below, the present embodiment is carried out lower premised on technical solution of the present invention Implement, give detailed embodiment and specific operating process, but protection scope of the present invention is not limited to following implementation Example.

Embodiment 1

As shown in figure 1, the present embodiment includes:It is arranged at the phase-locked local control module of local node and is arranged at long-range section The clock cleaning module of point, wherein:Remote node is connected with local node by optical fiber, local node by local reference clock and The local fiber received from clock cleaning module receives clock input phase-locked local control module, is locally joined by PID control Examine clock and enter horizontal phasing control and obtain local fiber tranmitting data register, so as to realize optical fiber temperature drift compensation.

Described phase-locked local control module includes:First wave filter, the second wave filter, phase discriminator, analog-digital converter (ADC), digital signal processing unit and Direct Digital Frequency Synthesizers (DDS), wherein:Second wave filter, phase discriminator, ADC, DDS and digital signal processing unit are sequentially connected in series into loop, the first wave filter both ends and phase discriminator and local fiber receiving module It is connected, DDS is connected with local fiber sending module.

Described remote node is provided with remote fiber sending module and remote fiber receiving module, and the remote fiber sends mould Block is connected with clock cleaning module and local fiber receiving module, the remote fiber receiving module and clock cleaning module and local Optical fiber sending module is connected.

Frequency-change sampling clock of the described local node using local reference clock as frequency-change sampling unit, can using scene Programming gate array (FPGA) is used as core devices, and remote synchronization clock is adopted as the frequency conversion of the frequency-change sampling unit of remote node Sample clock, realize the relevant collection of local node and remote node.

Described local node receives the clock information that remote node feeds back, so as to obtain by local fiber receiving module Obtain local fiber and receive clock.Local reference clock and local fiber are received into clock and are input to phase-locked local control module, is located Local fiber tranmitting data register is obtained after reason, local fiber tranmitting data register is output in local fiber sending module, passes through optical fiber It is sent to remote node.

Described remote node obtains the clock information that local node is sent, when passing through by remote fiber receiving module Clock cleaning module, which disappear, trembles processing, obtains remote synchronization clock, remote synchronization clock is sent into remote fiber sending module In, local node is fed back to by optical fiber.

As shown in Fig. 2 described local fiber receiving module and local fiber sending module use FPGA high speed serialization Transceiver (GTX).Remote node passes through GTX's also using GTX as remote fiber receiving module and remote fiber sending module Clock data recovery unit (CDR) extracts clock information.

The phase of described local reference clock isThe fixed phase of remote synchronization clock isLocal fiber is sent The fixed phase of clock isLocal fiber receives clockClock on local node to the fiber path of remote node Phase difference isShouldIt can be changed as fiber lengths change, so as to cause the clock jitter of receiving terminal.Assuming that hair Send the fiber lengths of link and receives link equal, then have:

Described remote synchronization clock produces shake because temperature drift causes fiber lengths to change, to ensureWith's Coherent pulse signalf not byThe influence of change, orderThen have:WhereinFor local light Fibre receives the phase difference of clock and local reference clock,For local fiber tranmitting data register and local reference clock phase Difference.As long as its equal can compensation is made because the fiber lengths that temperature drift introduces change the shake come to remote synchronization clock zone. Temperature drift compensation method comprises the following steps:

Step 1, local fiber receive clock and local reference clock passes through the first wave filter and the second wave filter respectively, so Phase demodulation is carried out by phase discriminator afterwards;

Step 2, identified result is digitized by the ADC of low speed, is input to digital signal processing unit and passes through PID Algorithm is handled signal, obtains phase-compensatory contro amount;

Step 3, phase-compensatory contro amount inputted into DDS, enter horizontal phasing control to local reference clock, obtain local fiber Tranmitting data register, realize optical fiber temperature drift compensation.

The first described wave filter and the second wave filter are narrow band filter, to filter the frequency outside phase demodulation frequency Component, reduce phase demodulation error.

Low speed ADC in the present embodiment is using the general ADC inside FPGA, i.e. XADC is realized, at pid control algorithm Reason, obtains phase-compensatory contro amount.According to obtained phase-compensatory contro amount, DDS is controlled by FPGA, adjusted locally The phase of optical fiber tranmitting data register, so as to realize temperature drift compensation.

Described PID control refers to:Wherein:U (n) is PID output controls Amount processed, e (n) are PID input quantities (i.e. digitized identified result), KpFor proportionality coefficient, KiFor integral coefficient, KdFor differential system Number.

The present embodiment is before PID control, and preferred pair e (n) carries out digital low-pass filtering, so as to filter the height of identified result Frequency noise, ensure e (n) stability;For Proportional coefficient Kp, integral coefficient KiWith differential coefficient KdSetting, can be divided Section processing, i.e., set different proportionality coefficient, integral coefficient and differential coefficient in different input quantity e (n) span Value, so as to improve the performance of the phase controlling of PID outputs.

Described local node and the sampling module of remote node use the structure of zero intermediate frequency, and the optical fiber for choosing 200m length enters Row test, wherein frequency conversion local oscillator are 2400MHz, and sampling clock is 50MHz quadrature samplings, and sampled input signal is 2401MHz's Sinusoidal signal.The simulated environment temperature change by way of carrying out uniformly heating and then natural cooling to optical fiber.Test analysis side Method synchronously samples for control local node and remote node to input signal, is sampled once every 15s, and will sampling Result cache, fft analysis is then carried out respectively to local sampled signal and long-range sampled signal, calculated using FFT result local The phase difference of sampled signal and long-range sampled signal, according to this result calculate local reference clock and remote synchronization clock it Between shake.

As shown in figure 3, when without temperature drift compensation, because optical fiber length changes, remote node sampled signal is relative originally The sampled signal phase difference of ground node is as shown in the figure.After converting chronomere, when remote synchronization clock is relative to local refer to The shake peak-to-peak value of clock is 289.84ps, and the shake root-mean-square value of remote synchronization clock relative local reference clock is 60.34ps.

As shown in figure 4, under same test condition, during using temperature drift compensation, remote node is using signal relative to local Node sample signal phase difference is as shown in the figure.After converting chronomere, remote synchronization clock is relative to local reference clock Shake peak value is 22.70ps, and remote synchronization clock is 3.94ps relative to the shake root-mean-square value of local reference clock.From result It can draw, the bright temperature drift compensation system of this law and temperature drift compensation method can substantially reduce the shake of remote synchronization clock, carry The synchronization accuracy of high-altitude synchronised clock.

Compared with prior art, technique effect of the invention includes:

1) synchronization accuracy is high, relative inexpensiveness, the present invention use based on wave filter, phase discriminator, DDS digitlization light Fine temperature drift compensation scheme, there is higher clock synchronization accuracy;By test, clock synchronization accuracy is less than 5ps, can meet to penetrate The sampling clock of the astronomical array of electricity synchronously requires.In addition, comparing high-precision simulated optical control method, cost substantially reduces, Compare the extensive requirement of structuring the formation of suitable radio astronomy array;

2) integrated level is high, and the present invention can be referred to by the completion of optical fibre channel all the way sampling clock, sampled data, system control The transmission of order, it is achieved thereby that data acquisition, Transmission system it is highly integrated, reduce further cost, be very suitable for big The distributed parallel computing environment of scale radio astronomy array;

3) strong environmental adaptability, the present invention have good temperature drift compensation ability, are adapted to various extreme open airs Environment, it is adapted to radio astronomy array to structure the formation the application characteristic that scope is wide, background environment is complicated.

Claims (4)

1. a kind of implementation method of radio astronomy array remote fiber synchronization system, it is characterised in that the system includes:Set In local node phase-locked local control module and be arranged at the clock cleaning module of remote node, wherein:Remote node and sheet Ground node is connected by optical fiber, and local node receives local reference clock and the local fiber received from clock cleaning module Clock inputs phase-locked local control module, and entering horizontal phasing control by PID control local reference clock obtains local fiber transmission Clock, i.e.,Wherein u (n) is PID output control amounts, and e (n) inputs for PID Amount, KpFor proportionality coefficient, KiFor integral coefficient, KdFor differential coefficient;
Described phase-locked local control module includes:First wave filter, the second wave filter, phase discriminator, ADC, Digital Signal Processing Unit and DDS, wherein:Second wave filter, phase discriminator, ADC, DDS and digital signal processing unit are sequentially connected in series into loop, and first Wave filter both ends are connected with phase discriminator and local fiber receiving module, and DDS is connected with local fiber sending module;
It the described method comprises the following steps:
Step 1, local reference clock and local fiber receive clock difference device after filtering, are then reflected by phase discriminator Phase;
Step 2, identified result is digitized by the analog-digital converter of low speed, is input to digital signal processing unit, led to Pid control algorithm processing is crossed, obtains phase-compensatory contro amount;
Step 3, phase-compensatory contro amount inputted into DDS, enter horizontal phasing control to local reference clock, obtain local fiber and send Clock, realize optical fiber temperature drift compensation;
Before PID control, digital low-pass filtering is carried out to e (n), so as to filter the high-frequency noise of identified result, ensures e (n) Stability;Segment processing Proportional coefficient Kp, integral coefficient KiWith differential coefficient Kd, i.e., the value in different input quantity e (n) In the range of different proportionality coefficients, integral coefficient and differential coefficient value are set, so as to improve PID output phase controlling property Energy.
2. according to the method for claim 1, it is characterized in that, described remote node is provided with remote fiber sending module and far Journey optic fiber transceiver module, the remote fiber sending module are connected with clock cleaning module and local fiber receiving module, and this is long-range Optic fiber transceiver module is connected with clock cleaning module and local fiber sending module.
3. according to the method for claim 1, it is characterized in that, described digital signal processing unit and ADC are realized by FPGA, Local fiber receiving module and local fiber sending module are realized by FPGA GTX.
4. according to the method for claim 1, it is characterized in that, described clock cleaning module enters the clock information received Row, which disappears, to be trembled processing and obtains remote synchronization clock, and feeds back to local node.
CN201610025611.0A 2016-01-15 2016-01-15 Radio astronomy array remote fiber synchronization system and its method CN105680970B (en)

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CN110247723A (en) * 2019-06-18 2019-09-17 广东大普通信技术有限公司 The device and method of Noise Identification and parameter adjustment in a kind of clock synchronization compliant with precision time protocol network

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CN102201906A (en) * 2010-03-26 2011-09-28 大唐移动通信设备有限公司 Clock signal processing method and equipment
CN204928848U (en) * 2015-07-21 2015-12-30 成都泰富通信有限公司 Temporal frequency transmission equipment

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JPH0575635A (en) * 1991-09-12 1993-03-26 Hitachi Comput Eng Corp Ltd Network synchronization management system and management system
CN103595522B (en) * 2012-08-17 2017-03-15 北京航天自动控制研究所 A kind of Dual-channel digital analog converter synchronization method
CN104917582B (en) * 2015-06-30 2018-05-01 中国科学技术大学 High precision clock distributes and phase automatic compensating system and its phase regulation method

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Publication number Priority date Publication date Assignee Title
CN102201906A (en) * 2010-03-26 2011-09-28 大唐移动通信设备有限公司 Clock signal processing method and equipment
CN204928848U (en) * 2015-07-21 2015-12-30 成都泰富通信有限公司 Temporal frequency transmission equipment

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