CN105262541A - Optical fiber remote transmission timing system of air space-based radio frequency signals - Google Patents
Optical fiber remote transmission timing system of air space-based radio frequency signals Download PDFInfo
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- CN105262541A CN105262541A CN201510565962.6A CN201510565962A CN105262541A CN 105262541 A CN105262541 A CN 105262541A CN 201510565962 A CN201510565962 A CN 201510565962A CN 105262541 A CN105262541 A CN 105262541A
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Abstract
The invention discloses an optical fiber remote transmission timing system of air space-based radio frequency signals. The optical fiber remote transmission timing system comprises the following structures: an antenna used for receiving an air space-based radio frequency signal; a radio frequency-optical conversion module used for receiving the air space-based radio frequency signal output by the antenna, carrying out low noise amplification processing on the air space-based radio frequency signal, converting the air space-based radio frequency signal into an optical signal by a laser and outputting the optical signal; an optical-radio frequency conversion module used for receiving the optical signal output by the radio frequency-optical conversion module, converting the change of the optical power of the optical signal into a corresponding current signal, carrying out low noise amplification processing on the current signal and reducing the current signal into the air space-based radio frequency signal through numerical control attenuation processing; an optical fiber used for transmitting the optical signal output by the radio frequency-optical conversion module to the optical-radio frequency conversion module; and a PRC or LPR device used for receiving the air space-based radio frequency signal output by the optical-radio frequency conversion module.
Description
Technical field
The present invention relates to the Long-distance Transmission Technologies of aerial space-based radiofrequency signal, specifically aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system.
Background technology
As the synchronizer of supporting network in networking application, first nodes equipment (PRC/LPR) needs high-precision reference source, generally adopt at present and from aerial space-based radiofrequency signal (the GPS/ Big Dipper), obtain reference signal, for transmission network equipment provides high-precision time and frequency synchronization signal.But the acquisition of aerial space-based radiofrequency signal needs certain condition, and namely antenna must be fixed on the open place of sky, and meanwhile, feed line length is also confined to ensure the normal receiving satellite signal of synchronizer in 200 meters.So in the face of some special application, as special applications scenes such as underground, tunnel, buildings, when distance between antenna and synchronizer is more than 20km, adopt traditional feeder line mode that synchronizer cannot be made to obtain aerial space-based radiofrequency signal, thus high accuracy frequency and the time service of time of PRC/LPR first nodes cannot be realized.
At present, this type of application scenarios faced by user has following solution.
First scheme is caesium clock scheme, namely adds caesium clock at this node, is used as the reference source of synchronizer with caesium clock.This programme can solve the problem of Frequency Synchronization, but needs by moving clock method time synchronized, after namely first when strange land is carried out pair, moves this locality to and carries out time service.Caesium clock is expensive simultaneously, also will in the face of external embargo, buying difficulty.
Alternative plan is baseband transmission scheme, namely after antenna proximal end parses baseband signal (time signal) by receiver, the synchronizer that baseband signal is delivered to far-end by transmission link is made reference source input.This programme can solve the application of frequency and time synchronized, but also there is two problems: one is, from networking mode, the synchronizer being originally used as first nodes is reduced to two-level node synchronizer; Two is to transform (current PRC/LPR equipment all adopts radio frequency interface mode) the GPS/BD input unit of existing synchronizer, to adapt to the access of baseband signal.
Third program is terrestrial links schemes, and the line clock namely extracting higher level's synchronizer from the circuit of the STM-N of ground east orientation mouth is used as the reference source of local synchronization equipment.Without the need to transforming synchronizer, but also there is the problem of being demoted by local synchronization equipment in this programme, simultaneously also existing defects in time synchronized.
In sum, all there is respective problem in current all schemes, cannot the perfect access solving aerial space-based radiofrequency signal reference source signal.
Summary of the invention
The object of the present invention is to provide aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system, the aerial space-based radiofrequency signal inputted by GPS/ big-dipper satellite at reception antenna end converts light signal to, transmitted at a distance in building or tunnel by optical fiber, subsequently, in the aerial space-based radiofrequency signal restoring GPS/ big-dipper satellite that PRC/LPR equipment side can't harm, be supplied to PRC/LPR equipment use.Transformation like this without the need to carrying out interface to PRC/LPR equipment can meet the access of aerial space-based radiofrequency signal, to meet the first nodes facility level of synchronizer.
Object of the present invention is achieved through the following technical solutions:
Aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system, comprises following structure:
Antenna: for receiving aerial space-based radiofrequency signal,
Radio frequency light modular converter: for reception antenna export aerial space-based radiofrequency signal, and aerial space-based radiofrequency signal is carried out LNA process, again by laser be converted to light signal export;
Light radio frequency modular converter: the light signal exported for received RF light modular converter, and the change of the luminous power of light signal is converted into corresponding current signal, and current signal is carried out LNA process, be reduced into aerial space-based radiofrequency signal by numerical control attenuation process again;
Optical fiber: for transmitting the light signal of radio frequency light modular converter output to light radio frequency modular converter;
PRC or LPR equipment: for receiving the aerial space-based radiofrequency signal that light radio frequency modular converter exports.
Design principle of the present invention is: utilize the antenna being arranged on ground to receive aerial space-based radiofrequency signal, the space-based radiofrequency signal of such as gps satellite or the space-based radiofrequency signal of big-dipper satellite, then aerial space-based radiofrequency signal is directly delivered to radio frequency light modular converter, by the original direct LNA process of aerial space-based radiofrequency signal, be converted to light signal finally by laser to export, optical fiber is adopted to realize transmission at a distance again, optical signal transmission is to being positioned at underground, tunnel, after light radio frequency modular converter in building, reduction treatment is carried out by light radio frequency modular converter, by light signal through being processed into current signal, again current signal is carried out LNA process, aerial space-based radiofrequency signal is reduced into again by numerical control attenuation process, finally aerial space-based radiofrequency signal is sent to PRC or LPR equipment use.
Above-mentioned design is that the thought utilizing optical fiber to carry out remote transmission carries out remote transmission to space-based radiofrequency signal.
Because fiber bandwidth is large, the transmission requirement of the aerial space-based radiofrequency signal of GPS and big-dipper satellite can be met.Conveniently set forth, the aerial space-based radiofrequency signal of following GPS and big-dipper satellite is referred to as gps signal and Big Dipper signal.
According to Nyquist's theorem: for specific channel, its channel width need be greater than the twice of chip rate, and the digital signal like this after sampling intactly remains the information in primary signal.Otherwise will the mutual interference between code element be occurred, so that receiving terminal correctly cannot judge.Gps signal L1 frequency range is 1575.42MHz ± 10MHz; Big Dipper generation signal frequency range is 2491.75MHz ± 4.08MHz; Beidou II B1 frequency range is 1561.098MHz ± 2.046MHz.If will transmit GPS/Big Dipper signal in a fiber, namely require that bandwidth of an optical fiber is minimum and meet 5GHz.
Optical Fiber Transmission is disposed in a large number already in transmission network, has reached the bandwidth of n × 40GHz in current backbone network.
So the transmission bandwidth of optical fiber can meet the bandwidth demand of GPS/BD Signal transmissions 5GHz.
Optical Fiber Transmission attenuation is little, and what can ensure long distance zooms out application; The attenuation constant of monomode fiber in 1310nm and 1550nm wavelength zone is generally respectively 0.3 ~ 0.4dB/km (1310nm) and 0.17 ~ 0.25dB/km (1550nm).ITU-TG.652 advises that regulation optical fiber should be less than 0.5dB/km and 0.4dB/km respectively in the attenuation constant of 1310nm and 1550nm.We are in regular maintenance, and under 1550nm wavelength mode, every kilometer calculates by 0.25dB, each dead splicing loss 0.5dB; Articulation is also calculated by 0.5dB.This loss simultaneously becomes with temperature hardly, does not worry the fluctuation causing mains voltage because of variation of ambient temperature.
The power output of general optical transmission module is generally at about 2dBm, and the sensitivity minimum power of general Optical Receivers is generally about-15dBm.As carried out point-to-point transmission by the optical fiber of 1550nm wavelength, in conjunction with the attenuation of 0.25dB/km, estimate with two joints, the long range propagation that module can support 64km is received/sent out to general light.
So adopt optical fiber to carry out growing distance zoom out utilization, the transmission range requirement of 30km can be met.
Optical Fiber Transmission antijamming capability is strong, and good stability, is particularly suitable for the application of the particular surroundingss such as tunnel
Optical fiber communication has strong antijamming capability, mainly contain two reasons, first is the basis of optical fiber is quartz, only pass light, non-conductive, be not afraid of high pressure, not by the effect of electromagnetic field, the light signal transmitted wherein is not by the impact of electromagnetic field, therefore Optical Fiber Transmission has very strong defensive ability/resistance ability to electromagnetic interference, industrial interference.Also Just because of this, the signal transmitted in a fiber is not easily ravesdropping, and is thus beneficial to secret; Second is that what to transmit in optical fiber is the light wave that frequency is very high, and the frequency of various interference is general all lower, so it can not the interfering frequency light wave more much higher than it.
The life-span of fiber plant is all very long, and time between failures reaches 500,000 ~ 750,000 hours, and the laser that what wherein the life-span was the shortest is in optical sender, least life is also more than 100,000 hours.
So the transmission adopting optical fiber to carry out GPS/ Big Dipper signal can meet the environmental requirement of the special applications such as tunnel.
Because GPS/ Big Dipper signal is all low-power signal, realize the key of the optical fiber teletransmission of GPS/ Big Dipper signal and difficult point mainly at GPS/ Big Dipper signal in the conversion of light signal.Although theoretical ripe, and there are some practical basis, in existing actual use procedure, mainly face following problem: GPS/ Big Dipper signal power is very low, be difficult to by the identification of general radio frequency light modular converter.
The aerial signal representative value of GPS is about-130dBm, the aerial signal representative value of a Big Dipper generation about-120dBm, the aerial signal representative value of Beidou II about-130dBm, the noise floor of this value closely signal.Meanwhile, the radio-frequency (RF) input power that conventional radio frequency light modular converter is general requires about-20dBm.
The main points of head it off make GPS/ Big Dipper signal energy distortionless by the conversion of radiofrequency signal to light signal.The means adopted the radiofrequency signal of this two frequency bins of the GPS/ Big Dipper are carried out respectively to the process of strict low noise amplification.Insertion Loss in transfer process is compensated simultaneously, control noise floor.
The aerial signal representative value of GPS is about-130dBm, the aerial signal representative value of the Big Dipper about-120dBm, the noise floor of this value closely signal.And the general RF input power of radio frequency/light modular converter requires about-20dBm, so will allow GPS/BD signal can be distortionless by radio frequency/light conversion, the process of strict low noise amplification must be carried out respectively to the RF signal of this two frequency bins of the GPS/ Big Dipper.
In traditional optic-fiber repeater system, also the transformational structure adopting radiofrequency signal to light signal is had, such as patent publication No. is that one point of Multi-path electricity of CN102752056B divides radio-frequency light transmission module, in this patent, also the transformational structure of radiofrequency signal to light signal is disclosed, radio frequency/optical signal conversion unit in this system is different from radio frequency light modular converter of the present invention, light/radiofrequency signal converting unit is also different from smooth radio frequency modular converter of the present invention, radiofrequency signal in this technology is high-power radiofrequency signal, different from radiofrequency signal of the present invention, the aerial space-based radiofrequency signal that the present invention be directed to, and this signal is lower powered radiofrequency signal, therefore, if directly adopt the radio frequency/optical signal conversion unit in existing optic-fiber repeater system and light/radiofrequency signal converting unit, because the radio-frequency input signals processing mode in this data is: first through Input matching, again through attenuator attenuates, again through amplifying process, decay after shunt again, finally be transferred in laser and produce light signal, obvious, input signal of the present invention is a kind of low-power signal, the noise floor of its input signal closely signal, therefore, cannot again through attenuation processing, this existing radio frequency/optical signal conversion unit obviously cannot be applied in the present invention, simultaneously, in this technology, 4 detectors of light/radiofrequency signal converting unit export and connect adjustable damping respectively, after adjustable damping exports, successively through signal combiner unit, high pass filter, first order amplifying circuit, numerical-control attenuator, output matching circuit.It is also different that this light/radiofrequency signal converting unit is also changed from smooth radiofrequency signal of the present invention, also cannot be applied in the present invention.Therefore, the present invention specifically designs, a kind of radio frequency light modular converter and light radio frequency modular converter that can adapt to this low-power radio frequency signal of GPS/ Big Dipper signal.
Described radio frequency light modular converter comprises following structure:
Rf signal reception port: the aerial space-based radiofrequency signal exported for reception antenna;
First low noise amplifier: under the prerequisite producing low noise, the aerial space-based radiofrequency signal that receives of radio frequency receiver port carries out amplifications and processes;
Laser: be converted to light signal output for the aerial space-based radiofrequency signal after the first low noise amplifier is amplified process.
Described radio frequency light modular converter also comprises light power controller A and control unit A, and the instruction of light power controller A reception control unit A also controls the power output of laser.
Described radio frequency light modular converter also comprises feed processing unit, the aerial space-based radiofrequency signal of feed processing unit received RF signal receiving port input, and whether the access automatically detecting aerial space-based radiofrequency signal opens a way or short circuit.
The input impedance of described first low noise amplifier reaches 50 Ω.
Described smooth radio frequency modular converter comprises following structure:
Light signal receiving port: for receiving the light signal that Optical Fiber Transmission is come;
Photo-detector: for the luminous power of the light signal that sensed light signal receiving port receives, and the change of this luminous power is converted into corresponding current signal;
Second low noise amplifier: for carrying out amplification process under the prerequisite producing low noise, to current signal;
Numerical-control attenuator: the level adjusting the second low noise amplifier output current signal.
Described smooth radio frequency modular converter also comprises luminous power collector, control unit B, controller B, luminous power collector gathers the luminous power that photo-detector detects, control unit B exports control command to controller B after receiving the luminous power of luminous power collector, controller B controls numerical-control attenuator according to control command.
The input impedance of the second low noise amplifier reaches 50 Ω.
Described aerial space-based radiofrequency signal is GPS or Big Dipper radiofrequency signal.
Described aerial space-based radiofrequency signal is low-power radio frequency signal.
Second low noise amplifier of the present invention and the one the second low noise amplifiers are a kind of low noise amplifier (LNA): because aerial space-based radiofrequency signal is very weak, close to noise floor, so the noise requirements of circuit is the strictest, be also that the noiseproof feature impact of whole system is of paramount importance.The main task of LNA is that radio frequency signal carries out amplifying reducing noise that post-module produces to the impact of signal under the prerequisite producing low noise as far as possible.In order to reach such effect, LNA serves vital effect with extraneous mating to himself and whole receiver, and normally requires that the input impedance of LNA reaches 50 Ω.Generally speaking, wish that LNA has high-gain, low-noise factor, the performance such as high linearity and low-power consumption.
Laser: realize the conversion of radiofrequency signal to light signal.
Light power controller A: mainly realize automatic gain compensation function.Automatic gain compensation adopts a close loop negative feedback control mode, according to signal amplitude adjustment gain, solve because satellite-signal is by differences such as the change of environment, decline and Received signal strength conditions, its input end signal power in very large range changes, and makes to output signal the problem that there will be strong and weak very greatly different signal power.
Feed processing unit: realize open circuit/short circuit alarm detection function.Whether detection antenna-feedback system access automatically of making a start opens a way or short circuit, points out user, be convenient to remote maintenance by the mode of stand by lamp.
Photo-detector: photo-detector is the pith that Fibre Optical Sensor is formed, and it detects the luminous power incided on its face, and the change of this luminous power is converted into corresponding current signal.Due to light signal in a fiber lossy and distortion so very high to the performance requirement of photo-detector.Wherein most important requirement is in the wave-length coverage of light source used, have higher sensitivity, less noise, and fast response time is to adapt to speed rates.
Numerical-control attenuator: the optical signal level for measuring element input characteristics can be adjusted.
Luminous power collector: the luminous power gathering Received signal strength, for controlling radio frequency output signal.
The invention has the advantages that: convert the radiofrequency signal that the GPS/ Big Dipper inputs to light signal at reception antenna end, transmitted at a distance by optical cable in building or tunnel, transmission range can reach 30km.Subsequently, at the RF signal restoring GPS/BD that PRC/LPR equipment side can't harm, PRC/LPR equipment use is supplied to.Transformation like this without the need to carrying out interface to PRC/LPR equipment can meet the access of space-based signal, to meet the first nodes facility level of synchronizer.
Accompanying drawing explanation
Fig. 1 is system diagram of the present invention.
Fig. 2 is the system block diagram of radio frequency light modular converter.
Fig. 3 is the system block diagram of light radio frequency modular converter.
Embodiment
Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited thereto.
embodiment 1:
As shown in Figure 1 and Figure 2 and Figure 3.BD in Fig. 1 is the Chinese big-dipper satellite referred to.
Aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system, comprises following structure:
Antenna: for receiving aerial space-based radiofrequency signal,
Radio frequency light modular converter: for reception antenna export aerial space-based radiofrequency signal, and aerial space-based radiofrequency signal is carried out LNA process, again by laser be converted to light signal export;
Light radio frequency modular converter: the light signal exported for received RF light modular converter, and the change of the luminous power of light signal is converted into corresponding current signal, and current signal is carried out LNA process, be reduced into aerial space-based radiofrequency signal by numerical control attenuation process again;
Optical fiber: for transmitting the light signal of radio frequency light modular converter output to light radio frequency modular converter;
PRC or LPR equipment: for receiving the aerial space-based radiofrequency signal that light radio frequency modular converter exports.
Design principle of the present invention is: utilize the antenna being arranged on ground to receive aerial space-based radiofrequency signal, the space-based radiofrequency signal of such as gps satellite or the space-based radiofrequency signal of big-dipper satellite, then aerial space-based radiofrequency signal is directly delivered to radio frequency light modular converter, by the original direct LNA process of aerial space-based radiofrequency signal, be converted to light signal finally by laser to export, optical fiber is adopted to realize transmission at a distance again, optical signal transmission is to being positioned at underground, tunnel, after light radio frequency modular converter in building, reduction treatment is carried out by light radio frequency modular converter, by light signal through being processed into current signal, again current signal is carried out LNA process, aerial space-based radiofrequency signal is reduced into again by numerical control attenuation process, finally aerial space-based radiofrequency signal is sent to PRC or LPR equipment use.
Above-mentioned design is that the thought utilizing optical fiber to carry out remote transmission carries out remote transmission to space-based radiofrequency signal.
Because fiber bandwidth is large, the transmission requirement of the aerial space-based radiofrequency signal of GPS and big-dipper satellite can be met.Conveniently set forth, the aerial space-based radiofrequency signal of following GPS and big-dipper satellite is referred to as gps signal and Big Dipper signal.
According to Nyquist's theorem: for specific channel, its channel width need be greater than the twice of chip rate, and the digital signal like this after sampling intactly remains the information in primary signal.Otherwise will the mutual interference between code element be occurred, so that receiving terminal correctly cannot judge.Gps signal L1 frequency range is 1575.42MHz ± 10MHz; Big Dipper generation signal frequency range is 2491.75MHz ± 4.08MHz; Beidou II B1 frequency range is 1561.098MHz ± 2.046MHz.If will transmit GPS/Big Dipper signal in a fiber, namely require that bandwidth of an optical fiber is minimum and meet 5GHz.
Optical Fiber Transmission is disposed in a large number already in transmission network, has reached the bandwidth of n × 40GHz in current backbone network.
So the transmission bandwidth of optical fiber can meet the bandwidth demand of GPS/BD Signal transmissions 5GHz.
Optical Fiber Transmission attenuation is little, and what can ensure long distance zooms out application; The attenuation constant of monomode fiber in 1310nm and 1550nm wavelength zone is generally respectively 0.3 ~ 0.4dB/km (1310nm) and 0.17 ~ 0.25dB/km (1550nm).ITU-TG.652 advises that regulation optical fiber should be less than 0.5dB/km and 0.4dB/km respectively in the attenuation constant of 1310nm and 1550nm.We are in regular maintenance, and under 1550nm wavelength mode, every kilometer calculates by 0.25dB, each dead splicing loss 0.5dB; Articulation is also calculated by 0.5dB.This loss simultaneously becomes with temperature hardly, does not worry the fluctuation causing mains voltage because of variation of ambient temperature.
The power output of general optical transmission module is generally at about 2dBm, and the sensitivity minimum power of general Optical Receivers is generally about-15dBm.As carried out point-to-point transmission by the optical fiber of 1550nm wavelength, in conjunction with the attenuation of 0.25dB/km, estimate with two joints, the long range propagation that module can support 64km is received/sent out to general light.
So adopt optical fiber to carry out growing distance zoom out utilization, the transmission range requirement of 30km can be met.
Optical Fiber Transmission antijamming capability is strong, and good stability, is particularly suitable for the application of the particular surroundingss such as tunnel
Optical fiber communication has strong antijamming capability, mainly contain two reasons, first is the basis of optical fiber is quartz, only pass light, non-conductive, be not afraid of high pressure, not by the effect of electromagnetic field, the light signal transmitted wherein is not by the impact of electromagnetic field, therefore Optical Fiber Transmission has very strong defensive ability/resistance ability to electromagnetic interference, industrial interference.Also Just because of this, the signal transmitted in a fiber is not easily ravesdropping, and is thus beneficial to secret; Second is that what to transmit in optical fiber is the light wave that frequency is very high, and the frequency of various interference is general all lower, so it can not the interfering frequency light wave more much higher than it.
The life-span of fiber plant is all very long, and time between failures reaches 500,000 ~ 750,000 hours, and the laser that what wherein the life-span was the shortest is in optical sender, least life is also more than 100,000 hours.
So the transmission adopting optical fiber to carry out GPS/ Big Dipper signal can meet the environmental requirement of the special applications such as tunnel.
Because GPS/ Big Dipper signal is all low-power signal, realize the key of the optical fiber teletransmission of GPS/ Big Dipper signal and difficult point mainly at GPS/ Big Dipper signal in the conversion of light signal.Although theoretical ripe, and there are some practical basis, in existing actual use procedure, mainly face following problem: GPS/ Big Dipper signal power is very low, be difficult to by the identification of general radio frequency light modular converter.
The aerial signal representative value of GPS is about-130dBm, the aerial signal representative value of a Big Dipper generation about-120dBm, the aerial signal representative value of Beidou II about-130dBm, the noise floor of this value closely signal.Meanwhile, the radio-frequency (RF) input power that conventional radio frequency light modular converter is general requires about-20dBm.
The main points of head it off make GPS/ Big Dipper signal energy distortionless by the conversion of radiofrequency signal to light signal.The means adopted the radiofrequency signal of this two frequency bins of the GPS/ Big Dipper are carried out respectively to the process of strict low noise amplification.Insertion Loss in transfer process is compensated simultaneously, control noise floor.
The aerial signal representative value of GPS is about-130dBm, the aerial signal representative value of the Big Dipper about-120dBm, the noise floor of this value closely signal.And the general RF input power of radio frequency/light modular converter requires about-20dBm, so will allow GPS/BD signal can be distortionless by radio frequency/light conversion, the process of strict low noise amplification must be carried out respectively to the RF signal of this two frequency bins of the GPS/ Big Dipper.
In traditional optic-fiber repeater system, also the transformational structure adopting radiofrequency signal to light signal is had, such as patent publication No. is that one point of Multi-path electricity of CN102752056B divides radio-frequency light transmission module, in this patent, also the transformational structure of radiofrequency signal to light signal is disclosed, radio frequency/optical signal conversion unit in this system is different from radio frequency light modular converter of the present invention, light/radiofrequency signal converting unit is also different from smooth radio frequency modular converter of the present invention, radiofrequency signal in this technology is high-power radiofrequency signal, different from radiofrequency signal of the present invention, the aerial space-based radiofrequency signal that the present invention be directed to, and this signal is lower powered radiofrequency signal, therefore, if directly adopt the radio frequency/optical signal conversion unit in existing optic-fiber repeater system and light/radiofrequency signal converting unit, because the radio-frequency input signals processing mode in this data is: first through Input matching, again through attenuator attenuates, again through amplifying process, decay after shunt again, finally be transferred in laser and produce light signal, obvious, input signal of the present invention is a kind of low-power signal, the noise floor of its input signal closely signal, therefore, cannot again through attenuation processing, this existing radio frequency/optical signal conversion unit obviously cannot be applied in the present invention, simultaneously, in this technology, 4 detectors of light/radiofrequency signal converting unit export and connect adjustable damping respectively, after adjustable damping exports, successively through signal combiner unit, high pass filter, first order amplifying circuit, numerical-control attenuator, output matching circuit.It is also different that this light/radiofrequency signal converting unit is also changed from smooth radiofrequency signal of the present invention, also cannot be applied in the present invention.Therefore, the present invention specifically designs a kind of radio frequency light modular converter and the light radio frequency modular converter that can adapt to this low-power radio frequency signal of GPS/ Big Dipper signal.
As shown in Figure 2, described radio frequency light modular converter comprises following structure:
Rf signal reception port: the aerial space-based radiofrequency signal exported for reception antenna;
First low noise amplifier: under the prerequisite producing low noise, the aerial space-based radiofrequency signal that receives of radio frequency receiver port carries out amplifications and processes;
Laser: be converted to light signal output for the aerial space-based radiofrequency signal after the first low noise amplifier is amplified process.
Described radio frequency light modular converter also comprises light power controller A and control unit A, and the instruction of light power controller A reception control unit A also controls the power output of laser.
Described radio frequency light modular converter also comprises feed processing unit, the aerial space-based radiofrequency signal of feed processing unit received RF signal receiving port input, and whether the access automatically detecting aerial space-based radiofrequency signal opens a way or short circuit.
The input impedance of described first low noise amplifier reaches 50 Ω.
As shown in Figure 3, described smooth radio frequency modular converter comprises following structure:
Light signal receiving port: for receiving the light signal that Optical Fiber Transmission is come;
Photo-detector: for the luminous power of the light signal that sensed light signal receiving port receives, and the change of this luminous power is converted into corresponding current signal;
Second low noise amplifier: for carrying out amplification process under the prerequisite producing low noise, to current signal;
Numerical-control attenuator: the level adjusting the second low noise amplifier output current signal.
Described smooth radio frequency modular converter also comprises luminous power collector, control unit B, controller B, luminous power collector gathers the luminous power that photo-detector detects, control unit B exports control command to controller B after receiving the luminous power of luminous power collector, controller B controls numerical-control attenuator according to control command.
The input impedance of the second low noise amplifier reaches 50 Ω.
Described aerial space-based radiofrequency signal is GPS or Big Dipper radiofrequency signal.
Described aerial space-based radiofrequency signal is low-power radio frequency signal.
Second low noise amplifier of the present invention and the one the second low noise amplifiers are a kind of low noise amplifier (LNA): because aerial space-based radiofrequency signal is very weak, close to noise floor, so the noise requirements of circuit is the strictest, be also that the noiseproof feature impact of whole system is of paramount importance.The main task of LNA is that radio frequency signal carries out amplifying reducing noise that post-module produces to the impact of signal under the prerequisite producing low noise as far as possible.In order to reach such effect, LNA serves vital effect with extraneous mating to himself and whole receiver, and normally requires that the input impedance of LNA reaches 50 Ω.Generally speaking, wish that LNA has high-gain, low-noise factor, the performance such as high linearity and low-power consumption.
Laser: realize the conversion of radiofrequency signal to light signal.
Light power controller A: mainly realize automatic gain compensation function.Automatic gain compensation adopts a close loop negative feedback control mode, according to signal amplitude adjustment gain, solve because satellite-signal is by differences such as the change of environment, decline and Received signal strength conditions, its input end signal power in very large range changes, and makes to output signal the problem that there will be strong and weak very greatly different signal power.
Feed processing unit: realize open circuit/short circuit alarm detection function.Whether detection antenna-feedback system access automatically of making a start opens a way or short circuit, points out user, be convenient to remote maintenance by the mode of stand by lamp.
Photo-detector: photo-detector is the pith that Fibre Optical Sensor is formed, and it detects the luminous power incided on its face, and the change of this luminous power is converted into corresponding current signal.Due to light signal in a fiber lossy and distortion so very high to the performance requirement of photo-detector.Wherein most important requirement is in the wave-length coverage of light source used, have higher sensitivity, less noise, and fast response time is to adapt to speed rates.
Numerical-control attenuator: the optical signal level for measuring element input characteristics can be adjusted.
Luminous power collector: the luminous power gathering Received signal strength, for controlling radio frequency output signal.
Said system uses SQMP instrument to carry out net synchronization capability test in 100,000 seconds, and test index meets G.811 requirement completely.
As mentioned above, then well the present invention can be realized.
Claims (10)
1. aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system, is characterized in that: comprise following structure:
Antenna: for receiving aerial space-based radiofrequency signal,
Radio frequency light modular converter: for reception antenna export aerial space-based radiofrequency signal, and aerial space-based radiofrequency signal is carried out LNA process, again by laser be converted to light signal export;
Light radio frequency modular converter: the light signal exported for received RF light modular converter, and the change of the luminous power of light signal is converted into corresponding current signal, and current signal is carried out LNA process, be reduced into aerial space-based radiofrequency signal by numerical control attenuation process again;
Optical fiber: for transmitting the light signal of radio frequency light modular converter output to light radio frequency modular converter;
PRC or LPR equipment: for receiving the aerial space-based radiofrequency signal that light radio frequency modular converter exports.
2. aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system according to claim 1, is characterized in that: described radio frequency light modular converter comprises following structure:
Rf signal reception port: the aerial space-based radiofrequency signal exported for reception antenna;
First low noise amplifier: under the prerequisite producing low noise, the aerial space-based radiofrequency signal that receives of radio frequency receiver port carries out amplifications and processes;
Laser: be converted to light signal output for the aerial space-based radiofrequency signal after the first low noise amplifier is amplified process.
3. aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system according to claim 2, it is characterized in that: described radio frequency light modular converter also comprises light power controller A and control unit A, the instruction of light power controller A reception control unit A also controls the power output of laser.
4. aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system according to claim 2, it is characterized in that: described radio frequency light modular converter also comprises feed processing unit, the aerial space-based radiofrequency signal of feed processing unit received RF signal receiving port input, and whether the access automatically detecting aerial space-based radiofrequency signal opens a way or short circuit.
5. aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system according to claim 2, is characterized in that: the input impedance of described first low noise amplifier reaches 50 Ω.
6. aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system according to claim 1, is characterized in that: described smooth radio frequency modular converter comprises following structure:
Light signal receiving port: for receiving the light signal that Optical Fiber Transmission is come;
Photo-detector: for the luminous power of the light signal that sensed light signal receiving port receives, and the change of this luminous power is converted into corresponding current signal;
Second low noise amplifier: for carrying out amplification process under the prerequisite producing low noise, to current signal;
Numerical-control attenuator: the level adjusting the second low noise amplifier output current signal.
7. aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system according to claim 6, it is characterized in that: described smooth radio frequency modular converter also comprises luminous power collector, control unit B, controller B, luminous power collector gathers the luminous power that photo-detector detects, control unit B exports control command to controller B after receiving the luminous power of luminous power collector, controller B controls numerical-control attenuator according to control command.
8. aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system according to claim 6, is characterized in that: the input impedance of the second low noise amplifier reaches 50 Ω.
9. aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system according to claim 6, is characterized in that: described aerial space-based radiofrequency signal is GPS or Big Dipper radiofrequency signal.
10. aerial space-based radiofrequency signal optical fiber teletransmission time dissemination system according to claim 6, is characterized in that: described aerial space-based radiofrequency signal is low-power radio frequency signal.
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