CN105450311A - Signal receiving device - Google Patents
Signal receiving device Download PDFInfo
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- CN105450311A CN105450311A CN201510753447.0A CN201510753447A CN105450311A CN 105450311 A CN105450311 A CN 105450311A CN 201510753447 A CN201510753447 A CN 201510753447A CN 105450311 A CN105450311 A CN 105450311A
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- signal
- local oscillation
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- light signal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
- H04B10/6163—Compensation of non-linear effects in the fiber optic link, e.g. self-phase modulation [SPM], cross-phase modulation [XPM], four wave mixing [FWM]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/61—Coherent receivers
- H04B10/616—Details of the electronic signal processing in coherent optical receivers
- H04B10/6165—Estimation of the phase of the received optical signal, phase error estimation or phase error correction
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- Engineering & Computer Science (AREA)
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Abstract
The invention provides a signal receiving device comprising a data signal processing terminal, an optical fiber and an antenna terminal. The data signal processing terminal is connected with the antenna terminal via the optical fiber. The data signal processing terminal comprises a local oscillator source used for providing a first local oscillation signal; a signal receiving module connected with the optical fiber and used for receiving a second optical signal from the antenna terminal through the optical fiber, and then generating a second local oscillation signal and a data signal containing the required data information according to the second optical signal; and a first modulation module connected with the signal receiving module and the local oscillator source and used for sending a first optical signal and sending the first optical signal to the antenna terminal through the optical fiber. The first modulation module is configured to adjust the first optical signal according to the first local oscillation signal and the second local oscillation signal so as to adjust the antenna terminal to generate the corresponding second optical signal. Therefore, data signals are kept stable.
Description
Technical field
The present invention relates to data communication technology field, specifically, relate to a kind of signal receiving device.
Background technology
Along with the observing and controlling frequency in the fields such as astronomical observation and Aero-Space detection is expanded towards high band, the mode of observing and controlling is simultaneously developed towards multiple antennas group battle array by large aperture antenna, it is also proposed new challenge to the method for antenna receiving signal.
Because the observing and controlling frequency range of signal is higher, be faced with the excessive problem of loss by the direct signal transmission of microwave cable or local oscillator.Existing method generally uses Optical Fiber Transmission frequency reference signal or high-frequency local oscillation signal to antenna place, then carries out down-conversion to received signal at antenna place, finally by other circuit passback intermediate-freuqncy signal.Relevant treatment is carried out to the received signal to obtain result because the astronomical observation of distributed multi-antenna and Aero-Space detection all depend on, this just requires that receiving course must avoid introducing the shake of extra frequency or phase place as far as possible, otherwise can have a huge impact the precision measured.
Based on above-mentioned situation, need a kind of signal receiving device effectively can avoiding introducing extra frequency or phase jitter badly.
Summary of the invention
For solving the problem, the invention provides a kind of signal receiving device, described device comprises: data-signal end for process, optical fiber and antenna end, and described data-signal end for process is connected with antenna end by optical fiber, and wherein, described data-signal end for process comprises:
Local vibration source, it is for providing the first local oscillation signal;
Signal receiving module, itself and described Fiber connection, for being received the second light signal from antenna end by optical fiber, and generated the second local oscillation signal according to described second light signal and include the data-signal of required data message;
First modulation module, it is connected with described signal receiving module and local vibration source, for generating the first light signal and described first light signal being sent to described antenna end by described optical fiber, described first modulation module is configured to according to described first local oscillation signal and described first light signal of the second local oscillation signal adjustment, to regulate described antenna end to generate the second corresponding light signal, thus described data-signal is made to keep stable.
According to one embodiment of present invention, described local vibration source comprises:
Reference frequency unit, it is for providing reference frequency signal;
Frequency synthesis unit, it is connected with described reference frequency unit, synthesizes described first local oscillation signal for utilizing described reference frequency signal.
According to one embodiment of present invention, described local vibration source comprises:
Reference frequency unit, it is for providing reference frequency signal;
Local oscillator module, it is for providing basic local oscillation signal;
Synchronization module, itself and reference frequency unit and local oscillator model calling, for carrying out synchronously, obtaining described first local oscillation signal to described basic local oscillation signal according to described reference frequency signal.
According to one embodiment of present invention, described first modulation module comprises:
Phase discriminator, it is connected with described local vibration source and the first modulation module, for according to described first local oscillation signal and the second local oscillation signal, produces corresponding phase signal;
Laser, it is connected with described phase discriminator, for according to described phase signal, produces corresponding light carrier, is stabilized in preset range to make described data-signal;
Electrooptic modulator, it is connected with described laser and local vibration source, for by described first local oscillator signal madulation to described light carrier, obtain described first light signal;
Light signal transmitting element, itself and described electrooptic modulator and Fiber connection, for sending to described optical fiber by described first light signal.
According to one embodiment of present invention, described first modulation module also comprises:
Polarization scrambler, it is connected between described electrooptic modulator and light signal transmitting element, for disturbing inclined process to described first light signal.
According to one embodiment of present invention, described light signal transmitting element comprises optical circulator.
According to one embodiment of present invention, described signal receiving module comprises:
Light signal receiving element, itself and described Fiber connection, for receiving the second light signal that described Optical Fiber Transmission is come;
Photodetector, it is connected with described light signal receiving element, for carrying out opto-electronic conversion to described second light signal, generates corresponding first signal of telecommunication;
Second local oscillation signal generation unit, it is connected with described photodetector, for generating described second local oscillation signal according to described first signal of telecommunication;
Data-signal generation unit, it is connected with described photodetector, for generating described data-signal according to described first signal of telecommunication.
According to one embodiment of present invention, described signal receiving module also comprises:
First image intensifer, it is connected between described light signal receiving element and photodetector.
According to one embodiment of present invention, described light signal receiving element comprises optical circulator.
According to one embodiment of present invention, described second local oscillation signal generation unit comprises:
Power splitter, it is connected with described photodetector, for generating second signal of telecommunication according to described first signal of telecommunication;
Local oscillator filter, it is connected with described power splitter, for carrying out filtering to described second signal of telecommunication, obtains described second local oscillation signal.
According to one embodiment of present invention, described data-signal comprises intermediate-freuqncy signal, and described data-signal generation unit comprises:
Power splitter, it is connected with described photodetector, for generating the 3rd signal of telecommunication according to described first signal of telecommunication;
Intermediate-frequency filter, it is connected with described power splitter, for carrying out filtering to described 3rd signal of telecommunication, obtains described intermediate-freuqncy signal.
According to one embodiment of present invention, described antenna end comprises some Anneta modules.
According to one embodiment of present invention, described Anneta module comprises:
Radio-frequency antenna, it is for received RF signal;
Electrooptic switching element, itself and described radio-frequency antenna and Fiber connection, for modulating described first light signal according to described radiofrequency signal, generate described second light signal.
According to one embodiment of present invention, described electrooptic switching element comprises:
Optical signal transceiver unit, itself and described Fiber connection, for receiving the first light signal from described optical fiber, also for sending the second light signal to described optical fiber;
Second electrooptic modulator, it is connected with described radio-frequency antenna and optical signal transceiver unit, for modulating described first light signal according to described radiofrequency signal, generate described second light signal, and described second light signal is sent to described optical signal transceiver unit.
According to one embodiment of present invention, described electrooptic switching element also comprises:
Second image intensifer, it is connected between described optical signal transceiver unit and the second electrooptic modulator.
Signal receiving device provided by the present invention is by carrying out Active Compensation to the deviation that signal produces in transmission link, make the signal time delay of whole transmission link keep stable, so also just make the phase place of wideband frequency and the IF-FRE finally obtained keep stable.
Other features and advantages of the present invention will be set forth in the following description, and, partly become apparent from specification, or understand by implementing the present invention.Object of the present invention and other advantages realize by structure specifically noted in specification, claims and accompanying drawing and obtain.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, do simple introduction by accompanying drawing required in embodiment or description of the prior art below:
Fig. 1 is the structural representation typically utilizing reference frequency to carry out the signal receiving device of synchronous antenna end local vibration source;
Fig. 2 is the structural representation of typical directly distribution local oscillation signal to the signal receiving device of antenna;
Fig. 3 is the structural representation of signal receiving device according to an embodiment of the invention;
Fig. 4 is the structural representation of local vibration source according to an embodiment of the invention;
Fig. 5 is the structural representation of local vibration source in accordance with another embodiment of the present invention;
Fig. 6 is the structural representation of the first modulation module according to an embodiment of the invention;
Fig. 7 is the structural representation of signal receiving module according to an embodiment of the invention;
Fig. 8 is the structural representation of data-signal end for process according to an embodiment of the invention;
Fig. 9 is the structural representation of antenna according to an embodiment of the invention;
Figure 10 is the stability schematic diagram of return path signal according to an embodiment of the invention;
Figure 11 is return path signal Delay Variation schematic diagram according to an embodiment of the invention.
Embodiment
Describe embodiments of the present invention in detail below with reference to drawings and Examples, to the present invention, how application technology means solve technical problem whereby, and the implementation procedure reaching technique effect can fully understand and implement according to this.It should be noted that, only otherwise form conflict, each embodiment in the present invention and each feature in each embodiment can be combined with each other, and the technical scheme formed is all within protection scope of the present invention.
Meanwhile, in the following description, many details have been set forth for illustrative purposes, to provide thorough understanding of embodiments of the invention.But, it will be apparent to those skilled in the art that the present invention can detail here or described ad hoc fashion implement.
In the process of Received signal strength, the frequency of signal and the shake of phase place are mainly from two parts.Wherein a part is introduced in transmitting procedure, utilize optical fiber to come transmission frequency reference signal or high-frequency local oscillation signal and there is the advantages such as the low and electromagnetic interference of loss is little, but optical fiber is subject to the impact of the environmental factor such as temperature and vibration, when this is also with regard to causing signal to transmit in a fiber experience time to postpone a meeting or conference generation randomized jitter, and then affect the frequency of antenna place local oscillation signal and the stability of phase place, and the phase place change of local oscillation signal can be mixed into intermediate-freuqncy signal when down-conversion.Another part then carries out in frequency conversion and processing procedure to received signal because electronic device is introduced temperature and other environmental factor sensitive.Compensate so receiving system key Design is the time delay that causes this link and receiving device and phase place change.
Fig. 1 is the structural representation typically utilizing reference frequency to carry out the signal receiving device of synchronous antenna end local vibration source.
As shown in Figure 1, this signal receiving device comprises processing center 101 and antenna end 102.In processes in the heart 101, there is a high-precision reference frequency source 103.This reference frequency source 103 is generally atomic clock, and it can produce has very high-precision reference frequency.But the price of this atomic clock is higher, simultaneously also very harsh to the requirement of the environment of operation and maintenance, so can not antenna end be arranged on.Therefore, reference frequency source 103 needs, by data transmission unit 104, high accuracy reference frequency is transferred to optical fiber 105, be transferred in each antenna (i.e. antenna 1 to antenna N) in antenna end 102 again by optical fiber 105, with the local vibration source 107 in each antenna synchronous.In this signal receiving device, phase stabilization unit 113 is connected with data transmission unit 104, and it can ensure that optical fiber link can not introduce phase jitter in reference frequency signal.
Local vibration source 107 is generally crystal oscillator or oscillator, and its service condition is also harsh unlike reference frequency source 103, therefore can be arranged on antenna end.But the less stable of local vibration source self, therefore in order to ensure the quality of produced local oscillation signal, just needs to adopt lock unit 106 to stablize it.Lock unit 106 according to the reference frequency received from optical fiber 105 and the local frequency received from local vibration source 107, can control local vibration source 107, to produce stable local oscillation frequency signal.
Down-converter unit 108 is connected with radio-frequency antenna 109 and local vibration source 107, and it can utilize the local oscillation signal from local vibration source 107 to carry out down-conversion to the radiofrequency signal from radio-frequency antenna 109, thus obtains corresponding intermediate-freuqncy signal.Subsequently, down-converter unit 108 by the intermediate-freuqncy signal of generation by being transferred to the IF processing unit 112 of processing center 101 after filter unit 110 again by optical fiber 111, to carry out further analyzing and processing by IF processing unit 112.
The phase stabilization that such a construction ensures the local oscillation signal of link transmission of existing signal receiving device, it is advantageous that processing center is the same with transmitting reference frequency with the transceiver of intermediate-freuqncy signal between antenna arbitrarily, so also just can reduce costs.But the program needs the microwave device that arranges more in antenna end, the synchronous and signal down-conversion equipment of such as local oscillator, these equipment are all vulnerable to environmental change and introduce phase jitter.
In this signal receiving device, the generation of local oscillation signal and down-conversion etc. all complete in antenna end.Antenna end is generally distributed in different location, and their operational environment changes greatly, such as variations in temperature etc., and antenna end often can not control these environmental changes.And be used in antenna end the impact that local oscillator synthesis and the electronic device of down-conversion be easy to by environmental change (particularly variations in temperature), thus introduce very large phase place and change, and then affect final certainty of measurement.
Secondly, each antenna has needed the reception of reference frequency signal and the transmission of intermediate-freuqncy signal, therefore each antenna needs many cover transceivers and circuit to transmit different signals (such as reference frequency and intermediate-freuqncy signal etc.), this structure also just causing this signal receiving device is comparatively complicated, thus makes the cost increase of device.
Finally, this receiving system is, by optical fiber, the intermediate-freuqncy signal that down-converter unit produces directly is passed back to processing center.And this mode can make the impact that can be subject to extra phase jitter in intermediate-freuqncy signal in return link equally.In addition, if returned after intermediate-freuqncy signal is carried out digitlization, so configured digitizer is also easily subject to environmental impact in antenna end again.
Therefore can find out, the structure of this signal receiving device is as shown in Figure 1 comparatively complicated, easily introduces larger phase jitter in antenna end.
Fig. 2 is the structural representation of typical directly distribution local oscillation signal to the signal receiving device of antenna.With the signal receiving device shown in Fig. 1 unlike, local oscillation signal in signal receiving device antenna end 202 shown in Fig. 2 required for each antenna is that the heart 201 produces in processes, and the local oscillation signal of generation is directly transferred to each antenna by optical fiber by processing center 201.As shown in Figure 2, in this signal receiving device, processing center 201 provides high-precision reference frequency signal by reference to frequency cells 203, and produces local oscillation signal by frequency synthesis unit 204 according to reference frequency signal.
In this signal receiving device, need to configure special device to ensure the phase stabilization of local oscillation signal in transmitting procedure.Particularly, this signal receiving device is configured with the phase stabilization unit 211 be connected with frequency synthesis unit 204.Phase stabilization unit 211 can ensure that fiber links can not introduce phase jitter in local oscillation signal, thus ensures the phase stabilization of local oscillation signal in transmitting procedure.
The local oscillation signal produced can be transferred to the down-converter unit 206 of antenna by frequency synthesis unit 204 by optical fiber 205.Down-converter unit 206 is also connected with radio-frequency antenna 207, transmits with received RF antenna 207 the radiofrequency signal of coming.The radiofrequency signal that down-converter unit 206 utilizes the local oscillation signal received to carry out down-conversion to receive, thus obtaining intermediate-freuqncy signal, the IF processing unit 210 passing back to processing center 201 by optical fiber 209 after subsequently intermediate-freuqncy signal being carried out filtering by filter unit 208 is further analyzed process.
The advantage of this signal receiving device shown in Fig. 2 is, local oscillation signal is that the heart produces in processes, and processing center is well more a lot of than antenna end to the control of operational environment, so also just can avoid introducing extra phase jitter in local oscillation signal production process.Equally, this signal receiving device can also ensure phase stabilization in local oscillation signal transmitting procedure.
But still there is many deficiencies in this signal receiving device shown in Fig. 2.First, the down-converted of radio frequency signal still completes in antenna end, will introduce extra phase jitter like this.Particularly some signal receiving device adopts the mode of multistage frequency conversion, and its structure is complicated especially, and that introduces phase jitter may be larger.
Secondly, the device shown in this signal receiving device with Fig. 1 is the same, needs many cover transceivers and circuit to transmit different signals.Moreover, now the system of transmission local oscillation signal may often overlap all different (because the frequency being transferred to the local oscillation signal of different antennae may be different, if use the transmission system of arrowband, may every cover system all different; If use the transmission system in broadband, may difference do not had), in this case, the cost of whole system can increase further.
Finally, the same with the signal receiving device shown in Fig. 1, this signal receiving device also by optical fiber, the intermediate-freuqncy signal that down-converter unit produces directly is passed back to processing center.And this mode can make the impact that can be subject to extra phase jitter in intermediate-freuqncy signal in return link equally.In addition, if returned after intermediate-freuqncy signal is carried out digitlization, so configured digitizer is also easily subject to environmental impact in antenna end again.
Before the present invention considers, the some shortcomings of scheme and advantage, propose the signal receiving device that a kind of broadband signal surely returns mutually, transmit back processing center the broadband rf signal phase stabilization that remote antenna can receive by this device and process.
Fig. 3 shows the structural representation of the signal receiving device that the present embodiment provides.
As shown in Figure 3, the signal receiving device that the present embodiment provides comprises: data-signal end for process 301, optical fiber 302 and antenna end 303.Wherein, data-signal end for process 301 is connected with antenna end 303 by optical fiber 302, and it comprises: local vibration source 304, signal receiving module 305 and the first modulation module 306.Local vibration source 304 is for providing the first local oscillation signal.Signal receiving module 305 is connected with optical fiber 302, it can receive the second light signal from antenna end 303 according to optical fiber 302, generate corresponding second local oscillation signal according to the second light signal subsequently and comprise the data-signal of required data message, and the second local oscillation signal is sent to the first modulation module 306, to be regulated the first exported light signal according to the first local oscillation signal and the second local oscillation signal by the first modulation module 306.
In the present embodiment, intermediate-freuqncy signal is preferably included in the data-signal that signal receiving module 305 obtains, therefore intermediate-freuqncy signal can also be sent to intermediate frequency processor 307 by signal receiving module 305, carries out analyzing and processing further for intermediate frequency processor 307 pairs of intermediate-freuqncy signals.
It is pointed out that in other embodiments of the invention, the data-signal that signal receiving module 305 obtains can also comprise the first signal characterizing radiofrequency signal, or is only comprise the one in the first signal and intermediate-freuqncy signal, the present invention is not limited thereto.
Fig. 4 shows the structural representation of local vibration source in the present embodiment.
As shown in Figure 4, the local vibration source 304 that the present embodiment provides have employed the mode of frequency synthesis to produce local oscillation frequency signal, and it comprises reference frequency unit 401 and frequency synthesis unit 402.Reference frequency unit 401 can provide high-precision reference frequency signal.In order to obtain high-precision reference frequency signal, in the present embodiment, adopt atomic clock as reference frequency cells 401.Certainly, in other embodiments of the invention, other rational methods can also be adopted to provide high-precision reference frequency signal, the present invention is not limited thereto.
Frequency synthesis unit 402 is connected with reference frequency unit 401, and the reference frequency signal synthesis that it can provide according to reference frequency unit 401 obtains the first local oscillation signal, and by this first local oscillator Signal transmissions to the first modulation module 306.
It should be noted that, in other embodiments of invention, local vibration source can also adopt other reasonable manners to realize, and the present invention is not limited thereto.Such as in one embodiment of the invention, as shown in Figure 5, local vibration source can also adopt synchronous mode to realize.Particularly, in this embodiment, the reference frequency unit 501 in local vibration source 304 can provide high-precision reference frequency signal.Because local oscillator module 503 adopts crystal oscillator or oscillator, the therefore poor stability of this local oscillation signal causing local oscillator module 503 to produce usually.In order to obtain the first high local oscillation signal of stability, just need to utilize lock unit 502 to carry out synchronously local oscillator module 503.As shown in Figure 5, lock unit 502 is connected with reference frequency unit 501 and local oscillator module 503, and it can utilize reference frequency signal to carry out synchronously the local oscillation signal that local oscillator module 503 exports, thus obtains the first local oscillation signal.
Again as shown in Figure 3, first modulation module 306 is connected with local vibration source 304 and signal receiving module 305, it can generate the first light signal according to the first local oscillation signal from local vibration source 304 received and the second local oscillation signal from signal receiving module 305, and the first light signal is sent to antenna end 303 by optical fiber 302, the second light signal produced to regulate antenna end 303.
In the present embodiment, antenna end 303 comprises several antennas (i.e. antenna 1 to antenna N), and each antenna includes electrooptic switching element 308 and radio-frequency antenna 309.Wherein, electrooptic switching element 308 is connected between radio-frequency antenna 309 and optical fiber 302, and electrooptic switching element 308 1 aspect receives the first light signal from the first modulation module 306 by optical fiber 302, receives the radiofrequency signal from radio-frequency antenna 309 on the other hand.Electrooptic switching element 308 can utilize the radiofrequency signal received to modulate the first light signal, thus produces the second light signal.
First modulation module 304 can determine according to the first local oscillation signal and the second local oscillation signal the deviation that local oscillation signal produces in transmitting procedure.In the present embodiment, this deviation due in the process of local oscillation signal transmission in the optical fiber link (comprising optical fiber 302 and antenna end 303) because the factors such as the variations in temperature of optical fiber link and vibration are introduced, therefore this deviation is also unstable.It should be noted that, in other embodiments of the present invention, the deviation that local oscillation signal produces in transmitting procedure also may be caused by other rational factors, the present invention is not limited thereto.
The deviation that first modulation module 306 can produce in transmitting procedure according to local oscillation signal, adjust the first light signal outputting to antenna end 303, make the signal relevant with data-signal contained in the second light signal keep stable with this, thus the data-signal that signal receiving module 305 is finally obtained can keep stable.
As can be seen from foregoing description, the signal transmitting apparatus that the present embodiment provides is by carrying out Active Compensation to the deviation that signal produces in transmission link, make the signal time delay of whole transmission link keep stable, so also just make the phase place of wideband frequency and the IF-FRE finally obtained keep stable.
Meanwhile, in this signal receiving device, contain radio spectrum, local oscillator frequency spectrum and intermediate frequency spectrum in the second light signal, and these frequency spectrums are the same being transferred to the time delay produced in the process of data-signal end for process by antenna end.Therefore, the signal receiving device that the present embodiment provides comes the time delay of stable local oscillation signal in transmitting procedure and phase place by the mode of Active Compensation, so also just stabilizes time delay and phase place that radio spectrum and intermediate frequency spectrum experience in transmitting procedure.
Fig. 6 shows the structural representation of data-signal end for process in the signal receiving device that the present embodiment provides, and schematically shows the structure of the first modulation module in the present embodiment in this figure.
As shown in Figure 6, in the present embodiment, in data-signal end for process 301, the first modulation module 306 comprises: laser 601, electrooptic modulator 602, optical circulator 604 and phase discriminator 609.Wherein, laser 601 can provide preset wavelength to be first light carrier of λ.Local vibration source 304 is by the mode of frequency synthesis, and produce a stable single-frequency point frequency local oscillation signal (i.e. the first local oscillation signal), the centre frequency of this local oscillation signal is ω
lO, initial phase is
electrooptic modulator 602 is connected with local vibration source 304 and laser 601, and it by the first local oscillator signal madulation on light carrier, thus can obtain the first light signal.
In the present embodiment, optical circulator 604, as light signal transmitting element, is connected with electrooptic modulator 602.Optical circulator 604 is connected with optical fiber 302, and the first light signal that electrooptic modulator 602 produces can be transferred to antenna end 303 by optical fiber 302 by it.
In the present embodiment, between electrooptic modulator 602 and optical circulator 604, be also provided with polarization scrambler 603.Polarization scrambler 603 can the polarization state of disturbance light signal, occurs the damage relevant with polarization state to avoid signal.
Light signal can be transferred to the modulator of antenna end through optical fiber link.The shape of actual fiber itself may not be a positive round, and its inside has remaining anisotropic stress simultaneously.In addition, optical fiber also can by the impact of external factor, such as torsion, bending, extruding etc.These all can cause the polarization state of the light signal transmitted in a fiber unstable, and the propagation velocity being embodied in the pattern of two cross-polarizations is different, namely so-called fiber birefringence.
Due to the impact of random birefringence, after optical signal transmission to antenna end, its polarization state there will be random change.Current most of commercial modulator is all LiNbO
3modulator, and LiNbO
3modulation efficiency difference on crystal different main direction is very large, and this also just causes LiNbO
3modulator is responsive to the polarization direction of incident light.Therefore, if do not controlled the polarization state of the light signal entering far-end modulator, so can there is change at random in the modulation efficiency of return path signal, and worsening also may appear in the signal to noise ratio of the calibrating signal simultaneously returned, and finally affects the stability of return path signal and the performance of other side.
Certainly, in other embodiments of the invention, polarization scrambler 603 can utilize other modules that can control the polarization of the light signal entering far-end modulator or device (such as polarization tracking device, polarization diversity device or nonlinear polarization traction device etc.) to replace, and the present invention is not limited thereto.
Phase discriminator 609 is connected with laser 601, local vibration source 304 and signal receiving module 305.Signal receiving module 305 is connected with optical fiber 302, and it receives the second light signal from antenna end 303 by optical fiber 302, and generates the second local oscillation signal and intermediate-freuqncy signal according to the second light signal.Suppose that the time delay disturbance that optical fiber link is introduced due to variations in temperature and vibration is Δ τ
path, so phase place of the second local oscillation signal
can be expressed as:
Compare phase difference with source local oscillation signal (i.e. the first local oscillation signal) by phase discriminator 609 by the local oscillation signal (i.e. the second local oscillation signal) recovered afterwards that transmits round between data-signal end for process 301 with antenna end 303, can error phase be obtained
, namely exist:
The error phase that phase discriminator 609 will obtain
be transferred to laser 601, laser 601 can regulate optical carrier wavelength according to this error phase, and optical carrier wavelength is adjusted to λ+Δ λ.Now laser 601 exports new light carrier (i.e. the second light carrier) to electrooptic modulator 602, and electrooptic modulator 602 by the first local oscillator signal madulation on the second light carrier, can obtain the first new light signal.
Compared with the first initial light signal, after Optical Fiber Transmission, the dispersion time delay Δ τ caused by dispersion can be there is in this first stylish signal
disp.Dispersion time delay Δ τ
dispcan calculate according to following expression:
Δτ
disp＝D·L·Δλ(3)
Wherein, D represents the abbe number of optical fiber, and L represents the length of optical fiber.
The intermediate-freuqncy signal that the radiofrequency signal received due to antenna end and mixing produce have passed through round-trip transmission in data-signal end for process and antenna end unlike local oscillation signal, radiofrequency signal and intermediate-freuqncy signal have only passed back to data-signal end for process from antenna end, so the time delay that this two classes signal produces in the process of transmission is Δ τ
path+ Δ τ
disp.
Laser 601 is according to error phase
adjust the wavelength of light carrier, after compensation loop locking, 2 ω can be made
lOΔ τ
path+ 2 ω
lOΔ τ
disp=C, C one stablize constant.Now then have:
Δτ
path+Δτ
disp＝C/(2ω
LO)(4)
Find out thus, laser 601 is by the adjustment to light carrier, make the time delay of whole link transmission be stable, that is radiofrequency signal and intermediate-freuqncy signal are transferred to by antenna end the time delay that data-signal end for process produces also is stable, and therefore their frequency and phase place are also stable.
Fig. 7 shows the structural representation of signal receiving module in the present embodiment.
As shown in Figure 7, in the signal receiving device that the present embodiment provides, signal receiving module 305 comprises: light signal receiving element 701, first image intensifer 702, photodetector 703, second local oscillation signal generation unit 704 and intermediate-freuqncy signal generation unit 705.Wherein, light signal receiving element 701 is connected with optical fiber 302, and it transmits for receiving optical fiber 302 second light signal of coming.First image intensifer 702 is connected between light signal receiving element 701 and photodetector 703, the second light signal that light signal receiving element 701 receives can amplify by it, generates corresponding first signal of telecommunication for photodetector 703 according to the second light signal.
In the present embodiment, signal receiving module 305 can generate the second local oscillation signal and intermediate-freuqncy signal respectively according to the second light signal, and this function is realized by the second local oscillation signal generation unit 704 and intermediate-freuqncy signal generation unit 705.Wherein, the second local oscillation signal generation unit 704 is all connected with photodetector 703 with intermediate-freuqncy signal generation unit 705.
Second local oscillation signal generation unit 704 can generate corresponding second local oscillation signal according to first signal of telecommunication, and this second local oscillation signal is sent to the first modulation module 306, to adjust the first light signal by the first modulation module 306 according to the first local oscillation signal and the second local oscillation signal.Intermediate-freuqncy signal generation unit 705 can generate intermediate-freuqncy signal according to first signal of telecommunication, and this intermediate-freuqncy signal is sent to intermediate frequency processor 307, to carry out analyzing and processing further by intermediate frequency processor 307 pairs of intermediate-freuqncy signals.It should be noted that, in other embodiments of the invention, if the second light signal that light signal receiving element 701 receives can meet follow-up processing requirements, so then can configure the first image intensifer 702 in signal receiving module 305, to simplify the structure of whole device, and reduce volume and the cost of whole device, the present invention is not limited thereto.
Fig. 8 shows the concrete structure schematic diagram of data-signal end for process in the present embodiment.
As shown in Figure 8, in the present embodiment, signal receiving module adopts optical circulator as light signal receiving element, and the optical circulator 604 as light signal transmitting element in this optical circulator and the first modulation module is same circulator.The number of devices of data-signal end for process can be reduced like this, contribute to the structure of reduced data signal transacting end, and reduce the volume of data-signal end for process.
In the present embodiment, the second local oscillation signal generation unit 704 comprises power splitter 802 and local oscillator filter 803.Power splitter 802 is connected with photodetector 703, and its first signal of telecommunication that can generate according to photodetector 703 generates second signal of telecommunication, and by the second electric signal transmission to local oscillator filter 803.Local oscillator filter 803 is connected with power splitter 802, and the local oscillation signal comprised in second signal of telecommunication can leach by it, thus obtains the second local oscillation signal.
Intermediate-freuqncy signal generation unit 705 comprises power splitter 802 and intermediate-frequency filter 804.Power splitter 802 is connected with photodetector 703, and its first signal of telecommunication that can generate according to photodetector 703 generates the 3rd signal of telecommunication, and by the 3rd electric signal transmission to intermediate-frequency filter 804.Intermediate-frequency filter 804 is connected with power splitter 802, and intermediate-freuqncy signal can leach by it from the 3rd signal of telecommunication, thus obtains described intermediate-freuqncy signal.
Other structures of data-signal end for process can composition graphs 6 and Fig. 7 be found out, do not repeat them here.
It should be noted that, in other embodiments of the invention, other rational methods can also be adopted to obtain the second local oscillation signal and intermediate-freuqncy signal according to first signal of telecommunication, the present invention is not limited thereto.
In the present embodiment, the antenna end of signal receiving device comprises the identical Anneta module of multiple structure.Be described for the structure of Anneta module 1 to Anneta module below.
Fig. 9 shows the concrete structure schematic diagram of Anneta module 1 in the present embodiment.
As shown in Figure 9, Anneta module 1 comprises electrooptic switching element 308 and radio-frequency antenna 309.Wherein, electrooptic switching element 308 is connected between radio-frequency antenna 309 and optical fiber 302, and electrooptic switching element 308 1 aspect receives the first light signal from the first modulation module 306 by optical fiber 302, receives the radiofrequency signal from radio-frequency antenna 309 on the other hand.Electrooptic switching element 308 can utilize the radiofrequency signal received to modulate the first light signal, thus produces the second light signal.
As shown in Figure 9, in the present embodiment, electrooptic switching element 308 comprises optical signal transceiver unit 901, second image intensifer 902 and the second electrooptic modulator 903.Optical signal transceiver unit 901 can receive by optical fiber 302 the first light signal sent by data-signal end for process 301, and gives the second image intensifer 902 by the first optical signal transmission.In the present embodiment, the second image intensifer 902 is erbium-doped fiber amplifier, and it can amplify the first light, and gives the second electrooptic modulator 903 by the optical signal transmission after amplification.Second electrooptic modulator 903 is connected with radio-frequency antenna 309 and the second image intensifer 902, its radiofrequency signal that radio-frequency antenna 309 can be utilized to receive is modulated the first light signal, generate described second light signal, and the second light signal generated is sent to optical signal transceiver unit 901, to send data-signal end for process 301 by optical fiber 302 by counter for the second light signal by optical signal transceiver unit 901.
As can be seen from foregoing description, in the antenna end that the present embodiment provides, the structure of each Anneta module is simple, and each Anneta module utilizes electrooptic modulator to achieve full light down-conversion, achieves the conversion of rf frequency to IF-FRE in area of light.Frequency-variable electronic device can not only be saved like this, the interference that downconversion process is introduced can also be reduced.
In addition, the antenna end structure that the present embodiment provides is simple, the Main functional units of each Anneta module is electrooptic modulator, effectively can reduce the possibility that antenna end introduces extra phase shake like this, thus provide guarantee for finally obtaining stable IF-FRE.
In the present embodiment, the reference frequency of 10MHz is utilized to synthesize first local oscillation signal of 2.46GHz in data-signal end for process.First local oscillation signal is modulated on the first light carrier by the first electrooptic modulator, and by a polarization scrambler.Disturb light signal to the rear through an optical circulator, then enter the Optical Fiber Transmission of 45 kilometers to antenna end.
In antenna end, first the light signal received passes through another optical circulator, by this optical circulator light signal out through an erbium-doped fiber amplifier (if transmission range is little, also can not configure erbium-doped fiber amplifier), then through second electrooptic modulator.The broadband rf signal that radio-frequency antenna receives can be modulated on light carrier by the second electrooptic modulator, obtains the second light signal.The second light signal obtained after modulation also there will be radiofrequency signal by the IF-FRE after local oscillation signal down-conversion.Here, IF-FRE after the radiofrequency signal that receives of local oscillation signal, antenna and down-conversion is all on light carrier.Second light signal, then by the optical circulator of antenna end, reenters optical fiber to the transmission of data-signal end for process.
The heart in processes, the second light signal that passback comes branches away by optical circulator, amplifies, then revert to the signal of telecommunication through photodetector through image intensifer (depending on luminous power size the need of use).The signal of telecommunication is divided into two parts through a power splitter, and filtering respectively.Intermediate-freuqncy signal leaches by intermediate-frequency filter, gives data processing equipment below.Local oscillation signal leaches by local oscillator filter, and local oscillation signal and source local oscillation signal carry out phase demodulation, is used for the delay jitter of perception optical fiber link, and controls tunable laser and change optical carrier wavelength and stablize link delay.
In order to verify whether receiving system can ensure in receiving course that the phase place of signal and time delay are stablized, the stability of experimental record return path signal and time delay change in the present embodiment.Figure 10 and Figure 11 respectively illustrates stability and the Delay Variation schematic diagram of return path signal.As shown in Figure 10, after consistent link time delay, signal stabilization degree reaches 3.3x10
-13(1s average time) and 7.5x10
-17(10
4s average time).Also record time delay change in both cases respectively in addition: the wavelength 1) not changing tunable laser, is kept 1550 nanometers, and as the black dotted lines in Figure 11, delay variation reaches 2274 psecs; 2) change the wavelength of tunable laser, namely when compensating, as the solid black lines in Figure 11, delay variation is suppressed in 3.3 picosecond range.The writing time of time delay change is 20,000 seconds.
This shows, the signal transmitting apparatus that the present embodiment provides is by carrying out Active Compensation to the deviation that signal produces in transmission link, make the signal time delay of whole transmission link keep stable, so also just make the phase place of wideband frequency and the IF-FRE finally obtained keep stable.
It should be understood that disclosed embodiment of this invention is not limited to ad hoc structure disclosed herein, and the equivalent of these features that those of ordinary skill in the related art understand should be extended to substitute.It is to be further understood that term is only for describing the object of specific embodiment as used herein, and and do not mean that restriction.
Special characteristic, structure or characteristic that " embodiment " mentioned in specification or " embodiment " mean to describe in conjunction with the embodiments comprise at least one embodiment of the present invention.Therefore, specification various places throughout occur phrase " embodiment " or " embodiment " might not all refer to same embodiment.
Although above-mentioned example is for illustration of the principle of the present invention in one or more application, but for a person skilled in the art, when not deviating from principle of the present invention and thought, obviously can in form, the details of usage and enforcement does various amendment and need not creative work be paid.Therefore, the present invention is limited by appending claims.
Claims (15)
1. a signal receiving device, is characterized in that, described device comprises: data-signal end for process, optical fiber and antenna end, and described data-signal end for process is connected with antenna end by optical fiber, and wherein, described data-signal end for process comprises:
Local vibration source, it is for providing the first local oscillation signal;
Signal receiving module, itself and described Fiber connection, for being received the second light signal from antenna end by optical fiber, and generated the second local oscillation signal according to described second light signal and include the data-signal of required data message;
First modulation module, it is connected with described signal receiving module and local vibration source, for generating the first light signal and described first light signal being sent to described antenna end by described optical fiber, described first modulation module is configured to according to described first local oscillation signal and described first light signal of the second local oscillation signal adjustment, to regulate described antenna end to generate the second corresponding light signal, thus described data-signal is made to keep stable.
2. signal receiving device as claimed in claim 1, it is characterized in that, described local vibration source comprises:
Reference frequency unit, it is for providing reference frequency signal;
Frequency synthesis unit, it is connected with described reference frequency unit, synthesizes described first local oscillation signal for utilizing described reference frequency signal.
3. signal receiving device as claimed in claim 1, it is characterized in that, described local vibration source comprises:
Reference frequency unit, it is for providing reference frequency signal;
Local oscillator module, it is for providing basic local oscillation signal;
Synchronization module, itself and reference frequency unit and local oscillator model calling, for carrying out synchronously, obtaining described first local oscillation signal to described basic local oscillation signal according to described reference frequency signal.
4. the signal receiving device according to any one of claims 1 to 3, is characterized in that, described first modulation module comprises:
Phase discriminator, it is connected with described local vibration source and the first modulation module, for according to described first local oscillation signal and the second local oscillation signal, produces corresponding phase signal;
Laser, it is connected with described phase discriminator, for according to described phase signal, produces corresponding light carrier, is stabilized in preset range to make described data-signal;
Electrooptic modulator, it is connected with described laser and local vibration source, for by described first local oscillator signal madulation to described light carrier, obtain described first light signal;
Light signal transmitting element, itself and described electrooptic modulator and Fiber connection, for sending to described optical fiber by described first light signal.
5. signal receiving device as claimed in claim 4, it is characterized in that, described first modulation module also comprises:
Polarization scrambler, it is connected between described electrooptic modulator and light signal transmitting element, for disturbing inclined process to described first light signal.
6. the signal receiving device as described in claim 4 or 5, is characterized in that, described light signal transmitting element comprises optical circulator.
7. the signal receiving device according to any one of claim 1 ~ 6, is characterized in that, described signal receiving module comprises:
Light signal receiving element, itself and described Fiber connection, for receiving the second light signal that described Optical Fiber Transmission is come;
Photodetector, it is connected with described light signal receiving element, for carrying out opto-electronic conversion to described second light signal, generates corresponding first signal of telecommunication;
Second local oscillation signal generation unit, it is connected with described photodetector, for generating described second local oscillation signal according to described first signal of telecommunication;
Data-signal generation unit, it is connected with described photodetector, for generating described data-signal according to described first signal of telecommunication.
8. signal receiving device as claimed in claim 7, it is characterized in that, described signal receiving module also comprises:
First image intensifer, it is connected between described light signal receiving element and photodetector.
9. signal receiving device as claimed in claim 7 or 8, it is characterized in that, described light signal receiving element comprises optical circulator.
10. the signal receiving device according to any one of claim 7 ~ 9, is characterized in that, described second local oscillation signal generation unit comprises:
Power splitter, it is connected with described photodetector, for generating second signal of telecommunication according to described first signal of telecommunication;
Local oscillator filter, it is connected with described power splitter, for carrying out filtering to described second signal of telecommunication, obtains described second local oscillation signal.
11. signal receiving devices according to any one of claim 7 ~ 10, it is characterized in that, described data-signal comprises intermediate-freuqncy signal, and described data-signal generation unit comprises:
Power splitter, it is connected with described photodetector, for generating the 3rd signal of telecommunication according to described first signal of telecommunication;
Intermediate-frequency filter, it is connected with described power splitter, for carrying out filtering to described 3rd signal of telecommunication, obtains described intermediate-freuqncy signal.
12. signal receiving devices according to any one of claim 1 ~ 11, it is characterized in that, described antenna end comprises some Anneta modules.
13. signal receiving devices as claimed in claim 12, it is characterized in that, described Anneta module comprises:
Radio-frequency antenna, it is for received RF signal;
Electrooptic switching element, itself and described radio-frequency antenna and Fiber connection, for modulating described first light signal according to described radiofrequency signal, generate described second light signal.
14. signal receiving devices as claimed in claim 13, it is characterized in that, described electrooptic switching element comprises:
Optical signal transceiver unit, itself and described Fiber connection, for receiving the first light signal from described optical fiber, also for sending the second light signal to described optical fiber;
Second electrooptic modulator, it is connected with described radio-frequency antenna and optical signal transceiver unit, for modulating described first light signal according to described radiofrequency signal, generate described second light signal, and described second light signal is sent to described optical signal transceiver unit.
15. signal receiving devices as claimed in claim 14, it is characterized in that, described electrooptic switching element also comprises:
Second image intensifer, it is connected between described optical signal transceiver unit and the second electrooptic modulator.
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