CN106403930B - A kind of observations of pulsar devices, systems, and methods - Google Patents
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Abstract
The present invention provides a kind of observations of pulsar devices, systems, and methods, accurately time interval information can be obtained by counting to sampling clock, the temporal information of sampling instant is squeezed into data frame together with sampled data can guarantee that the time is consistent with the height of signal, the integer second obtained using hydrogen atomic clock and GPS receiver time synchronization and the small several seconds counted to get to sampling clock obtain accurate time information, it is hereby achieved that the other high-precision pulse star time of arrival (toa) of nanosecond, greatly improves the precision and accuracy of observations of pulsar；For avoid as data transmit lose and caused by time error, network verification head is increased in a data frame, it such as finds that admission control is able to carry out compensation, ensure that data integrity and time continuity under observing for a long time, be of great significance to observations of pulsar data processing.
Description
Technical Field
The invention relates to a pulsar observation device, a pulsar observation system and a pulsar observation method, which are suitable for pulsar observation and related scientific researches, such as pulsar arrival time, strong pulse radiation, walling, subpulse drift, magnetor, gamma ray pulsar, fermi source and the like, and are also suitable for pulsar timing, pulsar navigation and other applications.
Background
Pulsar is a kind of high-speed rotating neutron star, and is formed by that the star with larger mass is collapsed under the action of self gravity at the end stage of evolution, and the synchrotron radiation emitted by charged particles moving in the star rotates with the neutron star to form radio wave beam, and every time the radio wave beam is swept over the earth, a pulse is received, so that it is named pulsar.
The rotation period range of the pulsar is from several milliseconds to more than ten seconds, the period stability is excellent, the time characteristic of ultrahigh stability is realized, the most stable astronomical clock in nature is known, and the long-term stability of atomic time can be improved by utilizing pulsar timing. The two magnetic poles of the pulsar are respectively provided with a radiation beam, and according to the self-rotation condition of the star body, the pulsar periodically transmits pulse signals to the detection equipment on the spacecraft so as to guide the direction of the spacecraft which travels between the stars. The pulsar is like a lighthouse which is never extinguished by the sea in space, and is a navigation mark arranged in the space.
However, since the pulsar is located at an extremely long distance of hundreds of millions to billions of optical years from the earth, although the power radiated by the pulsar is extremely strong, the signal reaching the earth is extremely weak, and in order to observe the pulsar signal, besides the need to construct a radio telescope with a large caliber and a receiver with excellent performance, a set of special high-precision, high-stability and high-reliability terminal needs to be developed according to the characteristics of the pulsar signal for detection.
In the process that electromagnetic waves radiated by pulsar reach the earth through free space transmission, the universe is not absolute vacuum, and the influence of interplanetary media can cause the dispersion effect of signals, namely, high-frequency signals arrive first and low-frequency signals arrive later. To compensate for this effect, the common practice is to transform the received time domain signal into the frequency domain, divide the frequency spectrum into a plurality of channels, each channel contains a specific frequency range component signal, and delay (or advance) the signal corresponding to each channel according to the time of reaching the telescope at different frequencies, thereby achieving the effect of dispersion cancellation.
The observation of the pulsar has extremely high requirement on time precision, for example, in order to research the arrival time of the pulsar, the accurate time information of the pulsar arriving at the earth needs to be recorded, the pulsar usually needs to be monitored for decades or even longer, the arrival time residual of a single radio telescope generally can reach hundreds of nanoseconds to tens of microseconds, which is closely related to the performance and the time reference of the radio telescope, and for the same radio telescope, if the time is inaccurate, the observation of the lunar year is not carried out, or the recorded data is meaningless. Accurate radio pulsar timing indicates that their autorotation is slowing very slowly, typically at a rate of one million seconds per year, to resolve periodic variations of a few nanoseconds, in terms of daily counts.
The data is achromatic, accurate time interval information is also needed, time delay or advance is needed to be carried out on each sub-frequency channel according to the dispersion amount of the pulsar, and the time accuracy is needed to reach the microsecond level.
In addition, because the signals of the pulsar reaching the earth are extremely weak, the signals need to be observed for a long time and then are folded according to the period of the pulsar, so that the signal-to-noise ratio of the pulsar signals is improved, and effective data is obtained. Besides the extremely high requirement on the accuracy of the time interval, the folding also puts high requirements on the stability of the equipment, and the data recorded by long-time observation must ensure higher integrity. If data observed for a long time is lost, time dislocation can be caused, and accurate superposition cannot be realized.
Data processing and observation research of the pulsar puts very strict requirements on time precision and stability of observation equipment, so that how to guarantee the extremely high time precision and data integrity is the key of research and development of the pulsar observation equipment.
Disclosure of Invention
Technical problem to be solved
In order to solve the problems of the prior art, the invention provides a pulsar observation device, a pulsar observation system and a pulsar observation method.
(II) technical scheme
The invention provides a pulsar observation device, comprising: a time-frequency signal generating module 10, a signal processing board 20 and a control device 30; wherein, the time frequency signal generating module 10 generates a pulse per second signal 43, a sampling clock 42 and a standard time 49; the pulsar observation signal enters the signal processing board 20, and the signal processing board 20 generates pulsar observation data and decimal second time by using the sampling clock 42 and the second pulse signal 43; the control device 30 receives the standard time 49, the pulsar observation data and the decimal second time, and obtains the pulsar signal arrival time with nanosecond time resolution based on the standard time 49 and the decimal second time, and the control device 30 processes the pulsar observation data by using the pulsar signal arrival time.
(III) advantageous effects
According to the technical scheme, the pulsar observation device, the pulsar observation system and the pulsar observation method have the following beneficial effects:
(1) according to the invention, the sampling clock is counted to obtain accurate time interval information, the time information of the sampling moment and the sampling data are input into a data frame together to ensure that the time is consistent with the height of the signal, and accurate time information is obtained by utilizing integer seconds obtained by time synchronization of the hydrogen atomic clock and the GPS receiver and decimal seconds obtained by counting the sampling clock, so that the arrival time of nanosecond-level high-precision pulsar signals can be obtained, and the precision and the accuracy of pulsar observation are greatly improved;
(2) in order to avoid time errors caused by data transmission loss, a network check head is added in a data frame, if the data frame loss is found, compensation can be carried out, the data integrity and time continuity under long-time observation are guaranteed, and the method has important significance for pulsar observation data processing.
Drawings
FIG. 1 is a schematic diagram of a pulsar processing flow;
FIG. 2 is a system block diagram of a pulsar observation device according to an embodiment of the present invention;
fig. 3 is a diagram illustrating a data frame format according to an embodiment of the invention.
Description of the symbols
10-a time-frequency signal generating module;
11-hydrogen atomic clock; 12-a GPS receiver; 121-time signal module; a 13-second pulse synchronizer; 14-a frequency synthesizer;
20-a signal processing board;
21-an analog-to-digital converter; 22-a frequency divider; 23-a digital signal processing module; 24-a pulse counter; 25-a data transmission module; 251-a formatter; 252-a first gigabit network card;
30-a control device;
31-a data receiving module; 311-second gigabit network card; 312-network packet acquisition module; 313-data extraction and frame check module; 32-a pulsar signal arrival time calculation module; 33-a data post-processing module; 34-time acquisition card; 35-a data storage module;
a-a first radio frequency signal; b-a second radio frequency signal; 41-reference clock signal; 42-a sampling clock; a 43-second pulse signal; 44-a four-divided sampling clock; 45-pulsar observation data; 46-fraction second time; 47-pulsar signal arrival time; 48-processed data; 49-standard time; 50-a sampled signal; 51-the down-converted sampled signal.
Detailed Description
The invention provides a pulsar observation device, a pulsar observation system and a pulsar observation method, which can provide time precision of up to 4 nanoseconds and can realize accurate timing and observation of pulsars. The time precision comprises two meanings of precise time information and precise time interval, the invention counts the clock pulse to obtain the precise time interval information, and the precise GPS integer second and the decimal second for counting the clock pulse to obtain the precise time information, thereby obtaining the high-precision time; meanwhile, in order to avoid time errors caused by data transmission loss, a frame check head is added in a data frame, and compensation is carried out if frame loss is found, so that data integrity and time continuity under long-time observation are guaranteed.
Firstly, the working principle of the pulsar observation device is introduced through the pulsar signal processing flow. Fig. 1 shows a processing flow of a pulsar signal, electromagnetic waves radiated by a pulsar reach a radio telescope from a far outer space, and the electromagnetic waves are influenced by an interplanetary medium to cause a signal dispersion effect, and as shown in a pulse profile diagram which is widened in fig. 1, a pulse profile seen in a time domain is widened. In order to eliminate the dispersion effect, after the signal received by the radio telescope is sampled, fourier transform is performed to convert the signal into frequency, and the signal with the total bandwidth v is divided into n subchannels with the bandwidth Δ v, as shown in a frequency channel diagram with time delay in fig. 1, it can be obviously seen that the time of occurrence of pulses in each channel is different. The signal is then interference and dispersion cancelled. Since communication base stations, radars, satellites, electronic devices, etc. cause interference to the radio frequency band, which affects the signal processing effect if not eliminated, the radio interference should be eliminated in the frequency domain first. Then, the achromatic process needs to be completed. For a signal with a center frequency v and a bandwidth Δ v, the signal arrival time delay of a single channel after propagation through the interplanetary medium can be calculated using the following equation:
tDM＝8.3×106ms·DM·Δv/v2 (1)
wherein: DM is the dispersion of the interplanetary medium in cm-3pc, v and Δ v are in MHz units, and t has been givenDMThe unit of (c) is equivalent to ms. The contamination of the pulsar signals by this dispersion effect severely affects the detection of the pulsar signals (especially short-period pulsar signals), resulting in a decrease in sensitivity.
The effect of performing time delay compensation on the signal sub-channels by using the above formula is shown in a frequency channel diagram after time delay compensation, and then the sub-channels are overlapped and transformed to a time domain to obtain the pulsar outline. However, since the distance between the pulsar and the earth is too far, the signal reaching the radio telescope on the earth is extremely weak, and in order to observe the signal, the signal needs to be observed for a long time, and then is folded according to the period of the pulsar, so as to improve the signal-to-noise ratio and obtain a more accurate profile, such as a pulse profile graph obtained by adding and folding frequency channels in the graph.
To better understand the importance of time accuracy to pulsar signal processing, the following example is provided. Two different frequencies v1And v2Of the channel(s), the arrival time t of the signal resulting from the dispersion effect2And t1The time difference of (a) can be calculated by equation (2):
t2and t1The time units of (1) are ms, DM is the dispersion of the interplanetary medium, and the units are equivalent to dimensionless values, v1And v2All units of (A) are GHz. For example, when the DM value is 20, two adjacent channels v1And v2T is 1.699GHz and 1.7GHz respectively2-t1The time difference of (2) is 0.035 ms. That is, the time resolution of two adjacent channels when the sub-channel bandwidth is 1MHz should be over 35 microseconds to better eliminate the dispersion effect, and if the sub-channel bandwidth is increased by 10 times to 0.1MHz, the time resolution is also correspondingly increased by 10 times to 3.5 microseconds.
At present, the period of the pulsar with the fastest rotation is 1.55 milliseconds, the period is calculated according to 128 sampling points in each period, the time interval between every two points is 12 microseconds, and the time precision is higher than the sampling interval by one order of magnitude and is calculated to reach 1.2 microseconds.
For a millisecond pulsar with a weak signal, the period is only a few milliseconds, the flow rate of 1.4GHz is less than 1mJy (1 milli-center, Jy is a unit of celestial body radio current density), long-time integration of hours is generally carried out, then data is folded to improve the signal-to-noise ratio of the signal, because the time resolution of the data is high, the data rate reaches about a plurality of Gbps, if the transmitted data is lost, the data cannot be aligned during folding, effective data processing cannot be carried out, and the high data rate is difficult to maintain zero loss in long-time transmission.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.
As shown in fig. 2, the present invention provides a pulsar observation device, comprising: a time frequency signal generating module 10, a signal processing board 20 and a control device 30. Wherein,
the time-frequency signal generation module 10 generates a second pulse signal 43, a sampling clock 42 and standard time 49, the pulsar observation signal enters the signal processing board 20, the signal processing board 20 generates pulsar observation data and decimal second time by using the sampling clock 42 and the second pulse signal 43, the control device 30 receives the standard time 49, the pulsar observation data and the decimal second time, obtains pulsar signal arrival time with nanosecond time resolution based on the standard time 49 and the decimal second time 46, and the control device 30 processes the pulsar observation data 45 by using pulsar signal arrival time 47.
The time-frequency signal generation module 10 includes a hydrogen atomic clock 11, a GPS receiver 12, a second pulse synchronizer 13, and a frequency synthesizer 14.
The hydrogen atomic clock 11 and the GPS receiver 12 transmit a pulse-per-second signal (1PPS) to the pulse-per-second synchronizer 13, and the pulse-per-second synchronizer 13 performs the second synchronization of the hydrogen atomic clock 11 and the GPS receiver 12 using the pulse-per-second signals transmitted from the hydrogen atomic clock 11 and the GPS receiver 12, and transmits the pulse-per-second signal 43 to the signal processing board 20.
The hydrogen atomic clock 11 generates a reference clock signal 41, and the frequency synthesizer 14 generates a sampling clock 42 to the signal processing board 20 using the reference clock signal 41. The frequency of the reference clock signal 41 may be 10MHz, and the frequency of the sampling clock 42 may be 1 GHz.
The signal processing board 20 includes: an analog-to-digital converter 21, a digital down-conversion module 22, a digital signal processing module 23, a pulse counter 24 and a data transmission module 25.
Pulsar observation signals output by a radio telescope receiver system, namely a first radio frequency signal A and a second radio frequency signal B, enter an analog-to-digital converter 21, the analog-to-digital converter 21 samples the pulsar observation signals by using a sampling clock 42 provided by a frequency synthesizer 14, a sampling signal 50 then enters a digital frequency reduction module, and a sampling signal 51 after frequency reduction enters a digital signal processing module 23 to be subjected to digital signal processing to obtain pulsar observation data, specifically, the digital signal processing comprises the steps of performing Fourier transform and Stokes parameter calculation on the sampling signals, the number of Fourier transform points is 1024, and the number of frequency channels is 512.
The bandwidth of the first radio frequency signal a and the bandwidth of the second radio frequency signal B are 500MHz, the analog-to-digital converter 21 adopts a dual-channel, 1GHz sampling frequency, 8bit quantized high-speed sampling card, and the 1GHz sampling clock 42 provided by the hydrogen atomic clock 11 and the frequency synthesizer 14 ensures extremely high frequency accuracy and stability.
The analog-to-digital converter 21 transmits the second pulse signal 43 and the sampling clock 42 from the second pulse synchronizer 13 to the pulse counter 24 and the digital down-conversion module 22 respectively, the digital down-conversion module 22 divides the sampling clock 42 by four, the four-divided sampling clock 44 also enters the pulse counter 24, the pulse counter 24 counts the four-divided sampling clock 44 by using the second pulse signal 43, that is, the second pulse signal 43 resets the pulse counter 24 once per second to obtain a four-divided sampling clock 44 count value corresponding to the second pulse signal 43, and the count value obtains the time of a few seconds.
In the present invention, for a 1GHz sampling clock 42, the pulse time resolution of each quarter-divided sampling clock 44 is 1/(1000/4 × 10) due to the quarter-division by the digital down-conversion module 226) 4 ns, so a fraction of a second of four ns time resolution can be obtained.
The data transmission module 25 transmits pulsar observation data and the fraction second time to the control device 30.
In the present invention, the signal processing board 20 is a high-speed signal processing board, and includes a Xilinx Virtex 6FPGA, and the analog-to-digital converter 21, the digital down-conversion module 22, the digital signal processing module 23, the pulse counter 24, and the data transmission module 25 may be implemented by the FPGA.
The control device 30 includes: the device comprises a data receiving module 31, a time acquisition card 34, a pulsar signal arrival time calculation module 32, a data post-processing module 33 and a data storage module 35.
The data receiving module 31 receives the pulsar observation data and the fraction second time sent by the data sending module 25, sends the pulsar observation data 45 to the data post-processing module 33, and sends the fraction second time 46 to the pulsar signal arrival time calculating module 32.
The time acquisition card 34 receives the standard time 49 sent by the time signal module 121 of the GPS receiver 12, and sends the standard time 49 to the pulsar signal arrival time calculation module 32, and the pulsar signal arrival time calculation module 32 discards the fraction seconds of the standard time 49, converts the fraction second time 46 into the fraction seconds, and adds the fraction seconds to the standard time 49 after the fraction seconds are discarded, so as to obtain the pulsar signal arrival time 47.
For example, a fraction-second time of 128128000, the fraction-second time 46 translates to a fraction-second of 128128000 x 4/109When the standard information acquired from the time acquisition card 34 is UTC time 2016, 7, 27, 22, 59, 23.512512 seconds, the pulsar signal arrival time calculation module 32 discards the fraction seconds 0.453672 and adds the fraction seconds of the fraction second time conversion, the second part becomes 23.512512, and the pulsar signal arrival time is 2016, 7, 27, 22, 59, 23.512512 seconds. Since the standard time 49 is provided by the GPS receiver 12, and the GPS receiver 12 and the hydrogen atomic clock 11 are synchronized by the pulse-per-second synchronizer 13, that is, the pulse counter 24 in the signal processing board 20 is highly consistent with the start time of the time acquisition card 34 per second, in this way, accurate time information of the pulsar signal entering the pulsar observation device can be obtained.
The data post-processing module 33 processes the pulsar observation data 45 by using the pulsar signal arrival time 47 obtained by the pulsar signal arrival time calculation module 32, including converting the pulsar observation data 45 into a FilterBank format commonly used for pulsar software processing, performing post-processing such as interference elimination, dispersion elimination, folding and the like by using special software, and storing the processed data 48 in the data storage module 35.
The control device 30 is a high-performance computer with Intel Xeon E5-2630V 3 CPU processing core, 64G memory, and 48TB memory space, and may also be other computing devices or data processing platforms.
Therefore, the method and the device have the advantages that the integer seconds obtained by the time synchronization of the hydrogen atomic clock and the GPS receiver and the decimal seconds for counting the sampling clock are added to obtain the high-precision pulsar signal arrival time in a nanosecond level, the precision and the accuracy of pulsar observation are greatly improved, and the method and the device have important significance for pulsar observation data processing.
In the pulsar observation device of the present invention, the data transmission module 25 of the signal processing board includes: formatter 251 and first gigabit network card 252; the data receiving module 31 of the control device includes: a second gigabit network card 311, a network packet acquisition module 312, and a data extraction and frame check module 313.
The formatter 251 packs the pulsar observation data and the fraction second time into a data frame, where the packed data frame includes a network check header, pulsar observation data and a fraction second time, as shown in fig. 3, the data frame may be composed of a network check header (frame _ n) of 4 bytes, a fraction second time (timestamp) of 4 bytes, and pulsar observation data of 2048 bytes, the pulsar observation data of 2048 bytes corresponds to Stokes parameters generated by 512 frequency channels, so that each data frame has a size of 2056 bytes, a time interval between data frames is τ μ s, and the Stokes parameters (I, Q, U, V) are as follows (1):
I：A_amp+B_amp，Q：A_amp-B_amp，U：2[AB_re]，V：2[AB_im] (3)
the first radio frequency signal a and the second radio frequency signal B are respectively an intermediate frequency autocorrelation amplitude, an intermediate frequency cross correlation real part, an intermediate frequency cross correlation imaginary part, and an intermediate frequency cross correlation real part.
The data frame is sent to the second gigabit network card 311 of the control device 30 through the first gigabit network card 252, the first gigabit network card 252 and the second gigabit network card 311 are connected through a 10GbE network, in order to improve the transmission rate, a transport layer protocol UDP is used to transmit the data frame, the maximum frame in the mega frame mode of the UDP protocol is 8k +512 bytes, which can satisfy the transmission of data of 2048 frequency channels, if a frequency channel needs to be added, multiple 10GbE ports can be used for transmission, and 8 10GbE ports are supported to the maximum.
Since the UDP protocol does not check the transmission data, it is impossible to know whether the data frame arrives safely and completely. The pulsar observation has extremely high requirement on data integrity, the processing result of the pulsar data is inaccurate due to the loss of any time sequence, and through a large amount of experiments, when the frame sequence number is detected to be discontinuous or the interruption phenomenon is marked as packet loss. If a large amount of packet loss is detected, for example, a certain threshold value is exceeded (according to requirements, for example, 10E-4), data invalidation requires checking whether the system has a fault.
Therefore, the invention adds a 4-byte network check head in the header of the data frame, when the second tera network card 311 of the control device 30 receives the data frame, the network packet acquisition module 312 captures the data network packet, and then the data extraction and frame check module 313 separates the pulsar observation data 45 and the decimal second time 46 in the network packet from the network check head, judges whether the network check head is a continuous digital sequence, and judges whether the packet is lost by checking the continuity of the network check head.
If the data extraction and frame check module 313 determines that there is an occasional packet loss, the lost data frame is compensated, for example, by padding the RMS value of the data frame. The data extraction and frame check module 313 sends the compensated pulsar observation data 45 and the decimal second time to the data post-processing module 33 and the pulsar signal arrival time calculation module 32, respectively.
The pulsar observation device has the data rate of 1 x 10 when the data frame time interval is 64 mu s6And the packet loss rate of the network is 0 when the network is continuously tested for 24 hours at the rate of/64 × 2056 × 8 ≈ 245.1 Mbps.
Therefore, in order to avoid time errors caused by data transmission loss, the pulsar observation device provided by the invention adds the network check head in the data frame, can compensate if the data frame loss is found, ensures the data integrity and time continuity under long-time observation, and has important significance for pulsar observation data processing.
The invention also provides a pulsar observation system which comprises the pulsar observation device and a radio telescope connected with the pulsar observation device.
The invention also provides a pulsar observation method, which utilizes the pulsar observation device to obtain the pulsar signal arrival time with nanosecond time resolution.
So far, the embodiments of the present invention have been described in detail with reference to the accompanying drawings. From the above description, those skilled in the art should have a clear understanding of the pulsar observation device, system and method of the present invention.
According to the pulsar observation device, the pulsar observation system and the pulsar observation method, integer seconds obtained by synchronizing the time of the hydrogen atomic clock and the GPS receiver and decimal seconds for counting the sampling clock are added to obtain the nanosecond-level high-precision pulsar signal arrival time, so that the pulsar observation precision and accuracy are greatly improved; in order to avoid time errors caused by data transmission loss, a network check head is added in a data frame, if the data frame loss is found, compensation can be carried out, the data integrity and time continuity under long-time observation are guaranteed, and the method has important significance for pulsar observation data processing.
It is to be noted that, in the attached drawings or in the description, the implementation modes not shown or described are all the modes known by the ordinary skilled person in the field of technology, and are not described in detail. In addition, the above definitions of the respective elements are not limited to the various manners mentioned in the embodiments, and those skilled in the art may easily modify or replace them, for example:
(1) directional phrases used in the embodiments, such as "upper", "lower", "front", "rear", "left", "right", etc., refer only to the orientation of the attached drawings and are not intended to limit the scope of the present invention;
(2) the embodiments described above may be mixed and matched with each other or with other embodiments based on design and reliability considerations, i.e. technical features in different embodiments may be freely combined to form further embodiments.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A pulsar observation device, comprising: the device comprises a time-frequency signal generating module (10), a signal processing board (20) and a control device (30); wherein,
the time-frequency signal generation module (10) generates a pulse per second signal (43), a sampling clock (42) and standard time (49); the time-frequency signal generation module (10) comprises: a hydrogen atomic clock (11), a GPS receiver (12) and a second pulse synchronizer (13); the hydrogen atomic clock (11) and the GPS receiver (12) send pulse-per-second signals to the pulse-per-second synchronizer (13), and the pulse-per-second synchronizer (13) performs pulse-per-second synchronization on the hydrogen atomic clock (11) and the GPS receiver (12) by using the pulse-per-second signals sent by the hydrogen atomic clock (11) and the GPS receiver (12) and sends the pulse-per-second signals to the signal processing board (20);
the pulsar observation signals enter the signal processing board (20), and the signal processing board (20) generates pulsar observation data and decimal second time by using the sampling clock (42) and the second pulse signal (43); the signal processing board (20) includes: the device comprises an analog-to-digital converter (21), a digital frequency-reducing module (22), a pulse counter (24) and a data sending module (25); the analog-to-digital converter (21) transmits the pulse per second signal (43) and the sampling clock (42) to the pulse counter (24) and the digital down-conversion module (22) respectively, the digital down-conversion module (22) divides the sampling clock (42) by four, a four-divided sampling clock (44) enters the pulse counter (24), and the pulse counter (24) counts the four-divided sampling clock (44) by using the pulse per second signal (43) to obtain the time of decimal seconds;
the data sending module (25) sends pulsar observation data and decimal second time to the control device (30); the data transmission module (25) comprises: a formatter (251); the formatter (251) packages the pulsar observation data and the fraction second time into a data frame, wherein the packaged data frame comprises a network check header, pulsar observation data and the fraction second time;
the control device (30) receives the standard time (49), pulsar observation data and the decimal second time, and obtains pulsar signal arrival time with nanosecond time resolution based on the standard time (49) and the decimal second time, and the control device (30) processes the pulsar observation data by using the pulsar signal arrival time; the control device (30) comprises: a pulsar signal arrival time calculation module (32), wherein the pulsar signal arrival time calculation module (32) discards decimal seconds of the standard time, converts the decimal seconds time into decimal seconds and adds the decimal seconds to the standard time (49) after the decimal seconds are discarded to obtain the pulsar signal arrival time (47).
2. Pulsar observation device according to claim 1,
the time-frequency signal generation module (10) further comprises: a frequency synthesizer (14); wherein,
the hydrogen atomic clock (11) generates a reference clock signal (41), and the frequency synthesizer (14) generates the sampling clock (42) by using the reference clock signal (41) and sends the sampling clock (42) to the signal processing board (20).
3. Pulsar observation device according to claim 1,
the signal processing board (20) further includes: a digital signal processing module (23); wherein,
pulsar observation signals enter the analog-to-digital converter (21), the analog-to-digital converter (21) utilizes the sampling clock (42) to sample the pulsar observation signals, the sampling signals (50) enter the digital frequency reduction module (22), and the sampling signals (51) after frequency reduction enter the digital signal processing module (23) to be subjected to digital signal processing to obtain pulsar observation data.
4. Pulsar observation device according to claim 3,
the control device (30) further comprises: the device comprises a data receiving module (31), a time acquisition card (34), a data post-processing module (33) and a data storage module (35); wherein,
the data receiving module (31) receives pulsar observation data and decimal second time, sends the pulsar observation data to the data post-processing module (33), and sends the decimal second time to the pulsar signal arrival time calculating module (32);
the time acquisition card (34) receives standard time (49) and sends the standard time (49) to the pulsar signal arrival time calculation module (32);
the data post-processing module (33) processes pulsar observation data (45) by using the pulsar signal arrival time (47), and stores the processed data (48) in the data storage module (35).
5. Pulsar observation device according to claim 4,
the data transmission module (25) further comprises: a first gigabit network card (252); the data frame is sent to the data receiving module (31) through the first gigabit network card (252).
6. Pulsar observation device according to claim 5,
the data receiving module (31) comprises: a second gigabit network card (311), a network packet acquisition module (312) and a data extraction and frame check module (313);
the second gigabit network card (311) receives data frames, the network packet acquisition module (312) captures data network packets, the data extraction and frame check module (313) separates pulsar observation data (45) and decimal second time in the network packets from a network check head, compensates the lost data frames, and then respectively sends the compensated pulsar observation data (45) and decimal second time to the data post-processing module (33) and the pulsar signal arrival time calculation module (32).
7. Pulsar observation device according to claim 3, wherein the frequency of the sampling clock is 1GHz and the pulse time resolution of the quarter-frequency sampling clock is 4 nanoseconds.
8. The pulsar observation device according to claim 6, wherein the first gigabit network card (252) and the second gigabit network card (311) are connected via a 10GbE network, and a transport layer protocol UDP is used to transmit data frames.
9. A pulsar observation system, comprising: pulsar observation device according to any one of claims 1 to 8, and a radio telescope connected to the pulsar observation device.
10. A pulsar observation method, characterized in that a pulsar signal arrival time with nanosecond time resolution is obtained by using the pulsar observation device of any one of claims 1 to 8, and pulsar observation data is processed by using the pulsar signal arrival time.
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| US11537086B2 (en) * | 2018-04-27 | 2022-12-27 | University Of Tennessee Research Foundation | Pulsar based timing synchronization method and system |
| CN109991479B (en) * | 2019-03-22 | 2020-12-11 | 中国科学院新疆天文台 | Fast radio storm real-time detection device, system and method of multi-beam receiver |
| CN110058286A (en) * | 2019-05-13 | 2019-07-26 | 天津讯联科技有限公司 | Space-time synchronous method, apparatus, equipment and medium under the conditions of a kind of defence |
| CN110455282A (en) * | 2019-08-15 | 2019-11-15 | 中国科学院新疆天文台 | A kind of digital termination system applied to observations of pulsar |
| CN111292222B (en) * | 2020-01-22 | 2023-05-12 | 中国科学院新疆天文台 | Pulsar dispersion eliminating device and method |
| CN111504362B (en) * | 2020-05-07 | 2022-03-22 | 中国科学院新疆天文台 | Multifunctional processing system and method for observation signals |
| CN113433817B (en) * | 2021-06-24 | 2022-10-11 | 贵州射电天文台 | Pulsar clock system and method based on FAST pulsar observation |
| CN113765614B (en) * | 2021-09-08 | 2023-06-23 | 中国科学院新疆天文台 | System and method for improving information receiving efficiency of PAF data processing terminal |
| CN114114883B (en) * | 2021-11-01 | 2022-12-23 | 中国科学院国家授时中心 | Method for detecting atomic clock jump by observing multiple pulsar |
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