CN105717501A - Range finding system and method based on direct RF sampling and long distance fiber transmission - Google Patents
Range finding system and method based on direct RF sampling and long distance fiber transmission Download PDFInfo
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- CN105717501A CN105717501A CN201610054865.5A CN201610054865A CN105717501A CN 105717501 A CN105717501 A CN 105717501A CN 201610054865 A CN201610054865 A CN 201610054865A CN 105717501 A CN105717501 A CN 105717501A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S11/00—Systems for determining distance or velocity not using reflection or reradiation
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Abstract
The invention relates to a range finding system and method based on direct RF sampling and long distance fiber transmission. The system comprises an antenna part, an emission machine room and a central machine room, RF signals are received by an antenna and amplified by a low noise amplifier (LNA), an A/D sampling module of a collection preprocessing unit samples carries out direct RF sampling on the amplified RF signals, a digital down conversion module converts the RF signals into digital baseband signals, a data framing module frames the digital baseband signals in a set data format, an optical module converts the digital baseband signals into optical signals, the optical signals are transmitted to a signal processing terminal of the central machine room in long distance via fibers, and the signal processing signals recovers the optical signals to digital baseband signals, and then captures, tracks, demodulates and despreads the signals to obtain a pseudo-range time delay value of a user. According to the invention, direct RF sampling and remote fibers are used to reduce down conversion time delay and cable time delay and increase the range finding precision.
Description
Technical field
The present invention relates to technical field of satellite navigation, particularly the range-measurement system of a kind of optical fiber long range propagation of directly sampling based on radio frequency of satellite navigation system ground section and method thereof.
Background technology
Satellite navigation system is mainly made up of three independent sectors: space segment, ground segment and user segment, ground segment receives the check-in signal forwarded from space segment, by the process of check-in signal is obtained pseudo-range time delay value, real propagation delay should using Antenna aperture as stoichiometric point, and the propagation delay of reality also comprises reception channel time delay and transmission channel time delay except real propagation delay, receive channel time delay refer to receiver change from antenna phase center to A/D before analog channel time delay, namely receive null value；Transmission channel time delay refer to transmitter from D/A change after to the analog channel time delay transmitting antenna phase center, namely launch null value, so the impact that range finding is produced by the unstability that should reduce null value in data handling procedure as far as possible.
By long cable transmission analog if signal between emitting and receiving equipment and each receiving-transmitting chain of signal processing in tradition ground central station, the mode then passing through if sampling completes the reception of signal and the process of generation, it is owing to emitting and receiving equipment is significantly high to environmental requirement that emitting and receiving equipment and signal processing are easily separated, must being unobstructed and that electromagnetic conditions is good place, all devices be put together and is added equipment scale and improve the whole system requirement to environment.Signal based on analog if signal transmission receives schematic diagram as shown in Figure 1, check-in signal receives through antenna and passes through LNA processing and amplifying, then radiofrequency signal is converted to intermediate-freuqncy signal by downconverted device, by long cable transmission to signal processing terminal, a road A/D sampling module is selected to complete the analog if signal conversion to digital medium-frequency signal by signal processing terminal according to the principle of free cells rotation, and by the Digital Down Converter Module of signal processing terminal, digital medium-frequency signal is converted to digital baseband signal, finally completed catching check-in signal by corresponding signal processing module, the demodulation of tracking and information, decoding etc. process, obtain pseudo-range time delay value, from the definition receiving channel time delay, tradition ground central station receives channel time delay and includes antenna delay t1, LNA time delay t2, low-converter time delay t3And cable time delay t4, each equipment delay be there will be time delay instability by factors such as ambient temperature, working signal characteristics, the especially unstability of cable time delay, final influential system range finding delay stability of time.Traditional mode Problems existing: cable is embedded in trench, in trench, ambient temperature is uncontrollable and cable itself aging all to will result in whole system time delay unstable；Owing to the loss of cable is relatively big, it is unfavorable for long-distance transmissions, is generally separated distance only 100 meters～200 meters；Extensibility is not strong, if equipment need to be increased, it is necessary to rewiring, adds capital construction difficulty and brings difficulty to follow-up maintenance.
Summary of the invention
It is an object of the invention to provide the distance-finding method of a kind of optical fiber long range propagation of directly sampling based on radio frequency, reduce the impact on range finding of the time delay unstable factor, realize the remote separation of emitting and receiving equipment and signal processing various kinds of equipment simultaneously, solve tradition ground central station Problems existing.
The technical scheme is that
A kind of range-measurement system of optical fiber long range propagation of directly sampling based on radio frequency, including antenna part, transmitter room and central machine room, described antenna part includes antenna and low-noise amplifier LNA, transmitter room includes gathering pretreatment unit, described collection pretreatment unit includes A/D radio frequency sampling module, Digital Down Converter Module, blockette frame module and optical module, described central machine room includes signal processing terminal, the radiofrequency signal received is amplified after receiving radiofrequency signal by described antenna through low-noise amplifier LNA, radiofrequency signal after amplification is completed the direct RF sampling to radiofrequency signal by the A/D sampling module gathering pretreatment unit, by Digital Down Converter Module, radiofrequency signal is converted to digital baseband signal, with the data form set, digital baseband signal is carried out framing by data set frame module, then by optical module, digital baseband signal is converted to optical signal, utilize optical fiber long-distance transmissions (transmission range is up to tens kilometers) to the signal processing terminal of central machine room, first optical signal is reverted to digital baseband signal by signal processing terminal, then the catching of complete pair signals, follow the tracks of, the process of demodulation obtains the pseudo-range time delay value of user.
The distance-finding method of a kind of optical fiber long range propagation of directly sampling based on radio frequency, comprises the following steps:
(1) radiofrequency signal received is amplified after receiving radiofrequency signal by antenna through low-noise amplifier LNA, radiofrequency signal after amplification is completed the direct RF sampling to radiofrequency signal by the A/D sampling module gathering pretreatment unit, by Digital Down Converter Module, radiofrequency signal is converted to digital baseband signal, then digital baseband signal is carried out packing process with 10,000,000,000 net IP data packet formats by data set frame module, and utilize the time frequency signal of transmitter room to packet mark local zone time, bidding is fixed time and is spaced apart X, then by optical module, digital baseband signal is converted to optical signal, fiber-optic transfer is utilized to arrive central machine room, the distance of transmitter room and central machine room is Y, the propagation delay time being transferred to central machine room by transmitter room isWherein c is the light velocity.
(2) the time difference synchronous error δ≤α between central machine room and transmitter room two places is setmax, wherein αmaxFor setting threshold value, characterizing synchronization accuracy, the method for synchronizing time concrete adopted by Project Realization determines.The time frequency signal that central machine room provides using the atomic clock of self machine room is as time reference, and X receives packet at set time intervals, so that crosstalk does not occur two packets, need to meet X >=αmax。
(3) after optical signals optical fiber arriving signal processing terminal, first optical signal is reverted to digital baseband signal, then complete catching and following the tracks of of signal synchronous head, obtain the signal T time of receptionr, obtain subscriber signal T launch time according to departures framing numbert, so propagation delay value is △ t=Tr-Tt, thus obtaining pseudorange ρ=c (△ t-t 'r)。
The Advantageous Effects of the present invention:
Ground central station of the present invention utilizes optical fiber to realize the separation of the transmitter room including emitting and receiving equipment and the central machine room including signal processing.It is received as such as shown in Fig. 2 with signal, antenna part is containing antenna, the equipment such as low-noise amplifier LNA, the complete twin aerial of LNA receives the amplification of radiofrequency signal, so that rear class receives the process of equipment, transmitter room is containing gathering pretreatment unit, the direct RF sampling to radiofrequency signal is completed by the A/D sampling module gathering pretreatment unit, by Digital Down Converter Module, radiofrequency signal is converted to digital baseband signal, then with the data form of regulation, digital baseband signal is carried out framing by data set frame module, finally by optical module, digital baseband signal being converted to optical signal facilitates the follow-up transmission to signal and process, schematic diagram contrast is received based on the signal that analog if signal transmits with Fig. 1, A/D sampling module is mentioned transmitter room by central machine room, decrease the time delay link of low-converter and cable, the propagation delay time making the present invention only includes antenna delay, LNA time delay, adopt first unified A/D sampling to be then passed to the mode of each signal processing terminal simultaneously, avoid the defect selecting unlike signal processing module to cause time delay there are differences, decrease the time delay factors of instability；Having signal processing terminal in central machine room, first optical signal is reverted to digital baseband signal by it, has then passed through the catching of pair signals, follows the tracks of, the process of demodulation obtains the information such as the pseudo-range time delay value of user, Doppler frequency shift.
In sum, the present invention utilizes radio frequency directly to sample and fiber optic stretch reduces analog down time delay, cable time delay, reduces the intermediate link causing time delay unstable, improves system range finding delay stability of time；Optical fiber is utilized to realize zooming out at a distance, realizing transmitter room to separate with the distance of central machine room, separating distance, up to tens kilometers, improves the disguise of central machine room, make transmitter room be located at electromagnetic conditions remote districts good, unscreened, it is simple to the Appropriate application of geographical resource simultaneously；The extensibility of whole system strengthens.
Accompanying drawing explanation
Fig. 1 is based on the signal of analog if signal transmission and receives schematic diagram
The signal that Fig. 2 is the present invention receives schematic diagram
Fig. 3 is the range finding flow chart of the present invention
Detailed description of the invention
Below in conjunction with accompanying drawing, the present invention is further illustrated:
Satellite navigation system ground section demodulates propagation delay time value △ t by process to received signal, and this propagation delay time value is real propagation delay time ρ and reception channel time delay t 'rSummation, i.e. ρ=c (△ t-t 'r), as long as reducing t 'rThe impact that the time delay of whole range finding is unstable, can finally improve range finding delay stability of time.
Tradition is positioned at the A/D sampling module of central machine room and advances to the collection pretreatment unit of transmitter room and reduce analogsimulation down coversion link by the present invention, changing traditional if sampling is direct RF sampling, it is the time delay value before sampling from Antenna aperture to A/D owing to receiving channel time delay, so the present invention shifts to an earlier date calculating the position receiving time delay and unifies in transmitter room, signal based on radio frequency sampling digital signal optical fiber long range propagation receives schematic diagram as in figure 2 it is shown, receive channel time delay (namely receiving null value) to comprise antenna delay t1, LNA time delay t2, so total reception channel time delay is t 'r=t1+t2, reception channel time delay t compared to Fig. 1r=t1+t2+t3+t4By A/D sampling is placed in advance, reduce analog down and cable time delay link, solve the impact that delay stability of time is worsened by cable local environment, avoid the defect selecting unlike signal processing module to cause time delay there are differences simultaneously, reduce the impact that system is found range by time delay unstability.
As shown in Figure 2, the range-measurement system of a kind of optical fiber long range propagation of directly sampling based on radio frequency that the present embodiment provides, including antenna part, transmitter room and central machine room, described antenna part includes antenna and low-noise amplifier LNA, transmitter room includes gathering pretreatment unit, described collection pretreatment unit includes A/D radio frequency sampling module, Digital Down Converter Module, blockette frame module and optical module, described central machine room includes signal processing module, the radiofrequency signal received is amplified after receiving radiofrequency signal by described antenna through low-noise amplifier LNA, radiofrequency signal after amplification is completed the direct RF sampling to radiofrequency signal by the A/D sampling module gathering pretreatment unit, by Digital Down Converter Module, radiofrequency signal is converted to digital baseband signal, with the data form set, digital baseband signal is carried out framing by data set frame module, then by optical module, digital baseband signal is converted to optical signal, optical fiber is utilized to pass the long-distance transmissions signal processing terminal to central machine room, first optical signal is reverted to digital baseband signal by signal processing terminal, then the catching of complete pair signals, follow the tracks of, the process of demodulation obtains the pseudo-range time delay value of user.
Utilize optical fiber communicating optical signals to signal processing terminal, change the mode of original long cable transmission analog if signal, increase the exploitativeness of long range propagation, such that it is able to realize the remote separation of transmitter room and central machine room, facilitate the regular maintenance of central machine room and be conducive to the disguise of central machine room, because for satellite navigation system, signal processing is to complete at central machine room, so especially in Military Application, once central machine room is ruined, the operation of whole system can be produced impact, it is achieved that the disguise of central machine room has realistic meaning.
With reference to Fig. 3, the present invention provides the distance-finding method of a kind of optical fiber long range propagation of directly sampling based on radio frequency, comprises the following steps:
(1) radiofrequency signal received is amplified after receiving radiofrequency signal by antenna through low-noise amplifier LNA, radiofrequency signal after amplification is completed the direct RF sampling to radiofrequency signal by the A/D sampling module gathering pretreatment unit, by Digital Down Converter Module, radiofrequency signal is converted to digital baseband signal, then digital baseband signal is carried out packing process with 10,000,000,000 net IP data packet formats by data set frame module, and utilize the time frequency signal (1PPS or 1PPM) of transmitter room to packet mark local zone time, bidding is fixed time and is spaced apart X, then by optical module, digital baseband signal is converted to optical signal, utilize optical fiber long-distance transmissions to central machine room, the distance of transmitter room and central machine room is Y, the propagation delay time being transferred to central machine room by transmitter room isWherein c is the light velocity.
(2) time frequency signal in central machine room is provided by atomic clock, as time reference, it is possible to realized the time synchronized of transmitter room and central machine room by methods such as optical fiber bidirectional Time transfer receiver；If the time difference synchronous error δ≤α between central machine room and transmitter room two placesmax, the time frequency signal that central machine room provides using the atomic clock of self machine room is as time reference, and X receives packet at set time intervals, when assuming certain T0The moment of the packet arrival central machine room that the moment is demarcated by transmitter room is T0+△τ+αmax, next demarcation moment T0The moment of the packet arrival central machine room in+X moment is T0+ △ τ+X, so that crosstalk does not occur two packets, need to meet X >=αmax。
(3) after optical signals optical fiber arriving signal processing terminal, first optical signal is reverted to digital baseband signal, then complete catching and following the tracks of of signal synchronous head, thus obtain the signal T time of receptionr, obtain signal transmission time T according to departures framing numbert, so propagation delay value is △ t=Tr-Tt, thus obtaining pseudorange ρ=c (△ t-t 'r).The pseudo-range time delay value of the present invention is owing to decreasing time delay factors of instability t 'r, improve range finding delay stability of time.
Claims (2)
1. the range-measurement system of an optical fiber long range propagation of directly sampling based on radio frequency, including antenna part, transmitter room and central machine room, it is characterized in that: described antenna part includes antenna and low-noise amplifier LNA, transmitter room includes gathering pretreatment unit, described collection pretreatment unit includes A/D radio frequency sampling module, Digital Down Converter Module, blockette frame module and optical module, described central machine room includes signal processing terminal, the radiofrequency signal received is amplified after receiving radiofrequency signal by described antenna through low-noise amplifier LNA, radiofrequency signal after amplification is completed the direct RF sampling to radiofrequency signal by the A/D sampling module gathering pretreatment unit, by Digital Down Converter Module, radiofrequency signal is converted to digital baseband signal, with the data form set, digital baseband signal is carried out framing by data set frame module, then by optical module, digital baseband signal is converted to optical signal, utilize optical fiber long-distance transmissions to the signal processing terminal of central machine room, first optical signal is reverted to digital baseband signal by signal processing terminal, then the catching of complete pair signals, follow the tracks of, the process of demodulation obtains the pseudo-range time delay value of user.
2. the distance-finding method of an optical fiber long range propagation of directly sampling based on radio frequency, it is characterised in that: comprise the following steps:
(1) radiofrequency signal received is amplified after receiving radiofrequency signal by antenna through low-noise amplifier LNA, radiofrequency signal after amplification is completed the direct RF sampling to radiofrequency signal by the A/D sampling module gathering pretreatment unit, radiofrequency signal is converted to digital baseband signal, then digital baseband signal is carried out packing process with 10,000,000,000 net IP data packet formats by data set frame module, and utilize the time frequency signal of transmitter room to packet mark local zone time, bidding is fixed time and is spaced apart X, finally by optical module, digital baseband signal is converted to optical signal, utilize optical fiber long-distance transmissions to central machine room, the distance of transmitter room and central machine room is Y, the propagation delay time being transferred to central machine room by transmitter room isWherein c is the light velocity.
(2) the time difference synchronous error δ≤α between central machine room and transmitter room two places is setmax, αmaxFor setting threshold value, the time frequency signal that central machine room provides using the atomic clock of self machine room is as time reference, with prefixed time interval X reception packet, wherein X >=αmax；
(3) optical signals fiber-optic transfer is to the signal processing terminal of central machine room, first optical signal is reverted to digital baseband signal, then completes catching and following the tracks of of signal synchronous head, obtains the signal T time of receptionr, obtain subscriber signal T launch time according to departures framing numbert, so propagation delay value is Δ t=Tr-Tt, thus obtaining pseudorange ρ=c (Δ t-t'r)。
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| CN111638502A (en) * | 2020-04-29 | 2020-09-08 | 西南电子技术研究所（中国电子科技集团公司第十研究所） | Time-base-based transmitting one-way zero-value ranging system for measurement and control communication ground station |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111638502A (en) * | 2020-04-29 | 2020-09-08 | 西南电子技术研究所（中国电子科技集团公司第十研究所） | Time-base-based transmitting one-way zero-value ranging system for measurement and control communication ground station |
| CN111638502B (en) * | 2020-04-29 | 2023-09-05 | 西南电子技术研究所（中国电子科技集团公司第十研究所） | Emission unidirectional zero value ranging system based on time base for measurement and control communication ground station |
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