CN115694639A - Time-frequency signal phase-locked transmission system - Google Patents
Time-frequency signal phase-locked transmission system Download PDFInfo
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Abstract
The invention relates to the technical field of distributed radars, in particular to a time-frequency signal phase-locked transmission system, which comprises a phase-locked transmission front-end unit, a transmission long optical fiber and a phase-locked transmission rear-end unit; the transmission long optical fiber is connected with the phase-locked transmission front-end unit, and the phase-locked transmission rear-end unit is connected with the transmission long optical fiber; the time-frequency signal enters the phase-locked transmission front-end unit, and the two functions of time-frequency transmission and link phase-locked control are completed through the transmission long optical fiber and the phase-locked transmission rear-end unit.
Description
Technical Field
The invention relates to the technical field of distributed radars, in particular to a time-frequency signal phase-locked transmission system.
Background
The distributed radar array needs to perform phase synchronization on time-frequency references in each sub-array, so that homologous time-frequency signals need to be transmitted to each sub-array in a control center, optical fibers are generally used as transmission media in long-distance time-frequency transmission, the transmission delay temperature drift of single-mode optical fibers is about 40ps and km, if the transmission delay of an optical link is unstable under the conditions that the transmission distance is long and the temperature of the environment where the optical fibers are located changes violently, the phase fluctuation of the transmitted time-frequency signals can be caused by the instability of the delay, the time sequence of each sub-array is disordered, and the detection capability of a distributed radar system is reduced.
Therefore, the introduction of a long-distance time-frequency signal light transmission phase stabilization mechanism is necessary, the most conventional phase stabilization scheme applied in the current engineering adopts two optical wavelengths of digital pulse coarse time delay measurement light and microwave frequency-scaling fine phase measurement light which are multiplexed in a transmission optical chain to measure the time delay change of the link, and then the phase drift of a transmission signal caused by the temperature drift of a transmission optical fiber is counteracted by adjusting a variable delay line.
Disclosure of Invention
The invention aims to provide a time-frequency signal phase-locked transmission system which does not need to multiplex time delay measuring light wavelength and phase measuring light in a transmission optical fiber channel and solves the problem of stable phase transmission of time-frequency signals of a distributed radar array.
In order to achieve the above object, the present invention provides a time-frequency signal phase-locked transmission system, which includes a phase-locked transmission front-end unit, a transmission long optical fiber and a phase-locked transmission back-end unit;
the transmission long optical fiber is connected with the phase-locked transmission front-end unit, and the phase-locked transmission rear-end unit is connected with the transmission long optical fiber.
The phase-locked transmission front-end unit comprises a first time-frequency band-pass filter, a combiner, an electro-optical conversion module, a first optical circulator, an adjustable light delay line, a measurement and control processing module, a variable standard frequency source, a power divider, a first photoelectric conversion module, a time-frequency band-stop filter and a phase discrimination module;
the combiner is connected with the first time-frequency band-pass filter, the electro-optical conversion module is connected with the combiner, the first optical circulator is connected with the electro-optical conversion module, the adjustable optical delay line is connected with the first optical circulator and the transmission long optical fiber, the measurement and control processing module is connected with the adjustable optical delay line, the variable standard frequency source is connected with the measurement and control processing module, the power divider is connected with the variable standard frequency source and the combiner, the first photoelectric conversion module is connected with the first optical circulator, the time-frequency band-stop filter is connected with the first photoelectric conversion module, and the phase discrimination module is connected with the power divider, the time-frequency band-stop filter and the measurement and control processing module.
The phase-locked transmission back-end unit comprises a second optical circulator, an optical splitter, a second photoelectric conversion module and a second time-frequency band-pass filter;
the second optical circulator is connected with the transmission long optical fiber, the optical splitter is connected with the second optical circulator, the second photoelectric conversion module is connected with the optical splitter, and the second time-frequency band-pass filter is connected with the second photoelectric conversion module.
According to the time-frequency signal phase-locked transmission system, a time-frequency signal enters the phase-locked transmission front-end unit, and two functions of time-frequency transmission and link phase-locked control are completed through the long transmission optical fiber and the phase-locked transmission rear-end unit.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a time-frequency signal phase-locked transmission system according to the present invention.
Fig. 2 is a schematic diagram of a phase calibration process.
Fig. 3 is a schematic diagram of a link phase lock control flow.
Fig. 4 is a detailed flow chart of phase detection.
Fig. 5 is a schematic diagram of a phase detection and linear phase interval.
The phase-locked loop comprises a phase-locked transmission front-end unit 1, a transmission long optical fiber 2, a phase-locked transmission rear-end unit 3, a time-locked band-pass filter 4, a first time-frequency band-pass filter 5, a combiner 6, an electro-optical conversion module 7, a first optical circulator 7, a tunable optical delay line 8, a measurement and control processing module 9, a variable standard frequency source 10, a power divider 11, a first electro-optical conversion module 12, a time-frequency band rejection filter 13, a phase discrimination module 14, a second optical circulator 15, a light splitter 16, a second electro-optical conversion module 17 and a second time-frequency band-pass filter 18.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative and intended to explain the present invention and should not be construed as limiting the present invention.
Referring to fig. 1 to 5, the present invention provides a time-frequency signal phase-locked transmission system: the phase-locked transmission system comprises a phase-locked transmission front-end unit 1, a transmission long optical fiber 2 and a phase-locked transmission rear-end unit 3;
the transmission long optical fiber 2 is connected with the phase-locked transmission front-end unit 1, and the phase-locked transmission back-end unit 3 is connected with the transmission long optical fiber 2.
In the embodiment, a time-frequency signal enters the phase-locked transmission front-end unit 1, and two functions of time-frequency transmission and link phase-locked control are completed through the transmission long optical fiber 2 and the phase-locked transmission rear-end unit 3.
Further, the phase-locked transmission front-end unit 1 includes a first time-frequency band-pass filter 4, a combiner 5, an electro-optical conversion module 6, a first optical circulator 7, a tunable optical delay line 8, a measurement and control processing module 9, a variable standard frequency source 10, a power divider 11, a first electro-optical conversion module 12, a time-frequency band-stop filter 13, and a phase discrimination module 14;
the combiner 5 is connected with the first time-frequency band pass filter 4, the electro-optical conversion module 6 is connected with the combiner 5, the first optical circulator 7 is connected with the electro-optical conversion module 6, the adjustable optical delay line 8 is connected with the first optical circulator 7 and the transmission long optical fiber 2, the measurement and control processing module 9 is connected with the adjustable optical delay line 8, the variable standard frequency source 10 is connected with the measurement and control processing module 9, the power divider 11 is connected with the variable standard frequency source 10 and the combiner 5, the first electro-optical conversion module 12 is connected with the first optical circulator 7, the time-frequency band stop filter 13 is connected with the first electro-optical conversion module 12, and the phase discrimination module 14 is connected with the power divider 11, the time-frequency band stop filter 13 and the measurement and control processing module 9.
In this embodiment, the first time-frequency band pass filter 4 mainly filters out-of-band interference signals and harmonic component signals of the input time-frequency signal;
the combiner 5 combines an input time frequency signal and a standard frequency signal which can be output by the measurement and control processing module 9 into one path and outputs the path to the electro-optical conversion module 6;
the electro-optical conversion module 6 performs electro-optical conversion on the radio frequency signal mixed by time frequency and standard frequency, and outputs optical power.
The first optical circulator 7 sends the forward light output by the electro-optical conversion module 6 to the adjustable light delay line 8, and sends the return light on the link to the measurement and control processing module 9;
the adjustable light delay line 8 adjusts the delay amount according to the control information of the measurement and control processing module 9, when the system is initialized, the adjustable light delay line 8 returns to the middle point of the adjustable range of the delay, the adjusting precision is designed to be superior to the phase stabilizing precision of the system, the adjustable light delay line 8 can be formed by combining a temperature control optical fiber and a space light delay line driven by a motor, and the adjustable range is designed to be 2 times of the delay variation range of the located optical fiber link caused by the change of the environmental temperature.
The measurement and control processing module 9 is used for storing and reading locked link delay phase information, controlling and outputting the frequency of the variable standard frequency source 10, analyzing the phase discrimination information of the phase discrimination module 14, and controlling the delay amount of the adjustable light delay line 8 according to the phase discrimination information, and is an intelligent control center of the whole system.
The variable frequency scaling source 10 is configured to receive control of the measurement and control processing module 9, and send frequency scaling signals of different frequencies as needed to obtain delay phase information of different accuracies, where the frequency scaling signals are selected to avoid as much as possible that intermodulation signals in at least three orders of the frequency scaling signals and the transmission time-frequency signals do not fall within a transmission signal bandwidth. The output frequency range of the variable standard frequency is 10MHz to f max (highest frequency supported by the phase detection module 14), over the entire linkIn the phase delay measurement locking process, the variable frequency scaling source 10 outputs three frequency scaling signals, namely, low-precision frequency scaling f L Middle precision standard frequency f M High-precision standard frequency f H The system scales the frequency f with high precision corresponding to the phase/time delay difference measurement with high, medium and low precision respectively H Calibrating vector phase difference change with highest precision and calibrating frequency f with medium and low precision M 、f L And the time delay difference is calibrated, and the period crossing of high-precision phase measurement is avoided. Wherein f is H Is equal to f max (highest frequency supported by the phase detection module 14), intermediate frequency scaling f M Recommended value range of f H /5～f H /10, low frequency standard frequency f L Recommended value range of f H /5～f H /10。；
The power divider 11 divides the input variable-scale frequency signal into two parts, one of which is output to the combiner 5 of the phase-locked transmission front-end unit 1, and the other of which is output to the phase discrimination module 14;
the first photoelectric conversion module 12 performs photoelectric conversion on the input loop back light, performs appropriate amplification processing on the converted radio frequency signal, and outputs the radio frequency signal to the time-frequency band-stop filter 13;
the function of the time-frequency band elimination filter 13 is to filter the time-frequency signal transmitted in the input radio frequency signal, and only the frequency component of the loop-back standard frequency signal is left;
the phase discrimination module 14 performs phase discrimination on the original standard frequency signal input by the power divider 11 and the looped standard frequency signal component to obtain phase discrimination information of a vector phase difference between the two components, and sends the vector phase difference information to the measurement and control processing module 9.
Further, the phase-locked transmission back-end unit 3 includes a second optical circulator 15, an optical splitter 16, a second photoelectric conversion module 17, and a second time-frequency band-pass filter 18;
the second optical circulator 15 is connected with the transmission long optical fiber 2, the optical splitter 16 is connected with the second optical circulator 15, the second photoelectric conversion module 17 is connected with the optical splitter 16, and the second time-frequency band-pass filter 18 is connected with the second photoelectric conversion module 17.
In this embodiment, the second optical circulator 15 transmits the optical signal transmitted to the phase-locked transmission back-end unit 3 through the transmission long optical fiber 2 to the optical splitter 16, and transmits the coupled light of the optical splitter 16 back to the phase-locked transmission front-end unit 1 through the original optical path; the optical splitter 16 couples 10% of the optical signal output by the second optical circulator 15 to send to the second optical circulator 15, and 90% of the optical power is sent to the second photoelectric conversion module 17; the second photoelectric conversion module 17 performs photoelectric conversion on the input optical signal, performs amplification processing on the converted optical signal, and sends the amplified optical signal to the second time-frequency band-pass filter 18; the second time-frequency band-pass filter 18 filters out signals outside the time-frequency signal band, and outputs clean time-frequency signals.
The time-frequency signal phase-locked transmission system comprises two functions of time-frequency transmission and link phase-locked control, wherein when the system operates, the two functions operate simultaneously, the time-frequency transmission function ensures the purity of a time-frequency signal, and the link phase-locked control ensures the calibration, backtracking and stability of a link phase.
The following description is made in terms of the implementation of the time-frequency transmission function, for example, the frequency of the transmitted time-frequency signal is f 0 Time-frequency signal f 0 The phase-locked transmission front-end unit 1 is input, firstly, the phase-locked transmission front-end unit passes through the first time-frequency band pass filter 4, the 3dB bandwidth of the filter can be designed as the transmission time-frequency signal pass band, and the first time-frequency band pass filter 4 can effectively filter the input time-frequency signal f 0 The harmonic waves and the out-of-band spurious signals effectively inhibit time frequency signals and the harmonic waves and the standard frequencies (f) thereof i ) The frequency mixing intermodulation product ensures that the frequency spectrum of the transmission time-frequency signal is pure to a certain degree; the filtered time frequency signal and the standard frequency signal are synthesized into a mixed radio frequency signal in the combiner 5 and output to the electro-optical conversion module 6, the working bandwidth of the electro-optical conversion module 6 needs to completely cover the frequency ranges of the time frequency signal and the standard frequency signal, the electro-optical conversion module 6 performs electro-optical conversion on the mixed radio frequency signal and outputs the optical power to the No. 1 input port of the first optical circulator 7, then the optical power is output to the adjustable optical delay line 8 through the No. 3 port, and the adjustable optical delay line 8 performs phase adjustment and is connected with an external transmission long optical fiber2. An optical signal is transmitted to the phase-locked transmission back-end unit 3 through the long transmission fiber 2, in the phase-locked transmission back-end unit 3, an input optical signal firstly passes through the 3 ports of the second optical circulator 15, is output to the optical splitter 16 through the 2 ports of the second optical circulator 15, passes through the main path signal of the optical splitter 16, is output to the second photoelectric conversion module 17, the optical signal in the second photoelectric conversion module 17 is changed into a radio frequency signal, and is then amplified and output to the second time-frequency band-pass filter 18, the radio frequency signal input to the second time-frequency band-pass filter 18 includes a time-frequency signal, a standard-frequency signal and a mixed frequency signal of the time-frequency signal and the standard-frequency signal derived due to nonlinearity of the electro-optical/photoelectric conversion module, and the second time-frequency band-pass filter 18 filters other out-band signals and then keeps pure time-frequency signal output.
The link phase locking control function is realized in two working scenes, namely the system initialization realization and the system restart realization. The realization of the link phase locking control function during system initialization comprises the calibration of link phase information, the backtracking and real-time locking of link phases; and backtracking and locking the link phase in real time when the system is restarted. The system initialization has two triggering conditions, namely, the system initialization is triggered through the measurement and control processing module 9, and when the adjustable light delay line 8 reaches the adjustment limit range.
The phase calibration process is that the measurement and control processing module 9 controls and adjusts the standard frequency (f) on the basis of clearing the original clear stored standard frequency/phase information and the regression midpoint of the optical delay line i ) The vector phase difference measurement (phase discrimination) of the reference standard frequency and the loopback standard frequency is carried out under high, medium and low precision, and the vector phase difference value is ensured to be in the linear phase area of the phase discrimination module 14, and the standard frequency (f) is carried out i ) Avoiding it and transmitting time frequency signal (f) as much as possible during selection 0 ) The intermodulation signal frequency point within the third order of the time frequency falls within the 10dB bandwidth of the time frequency first time frequency band pass filter 4; the phase calibration process is as shown in fig. 2, and the vector phase difference value is measured, determined, stored and cleared in the calibration process; adjusting, judging, storing and clearing the standard frequency; the adjustable light delay line 8 is adjusted by a measurement and control processing module9, performing control operation. After the phase calibration process is started, the original stored standard frequency/phase information is cleared, then the optical delay line returns to the midpoint, and the highest standard frequency (f) is carried out max ) If the measurement and control processing module 9 judges that the currently measured high-precision measurement vector phase difference value is in a nonlinear phase region, the adjustable optical delay line 8 is adjusted until the currently measured high-precision measurement vector phase difference value is in the linear phase region; if the current high-precision measurement vector phase difference value is in the linear phase region, the time delay of the adjustable light delay line 8 is slightly increased and decreased at the point, the position of the linear phase region after the rising region or the falling region and before the time delay fine adjustment is determined, and high-precision vector phase difference information lambda is stored H Late entry medium precision vector phase difference measurement lambda M (ii) a Selecting from f for medium precision vector phase difference measurement (medium precision phase discrimination) time frequency max The method comprises the steps that/10, the middle precision vector phase difference value starts to be measured, if the current middle precision vector phase difference value is in the nonlinear phase area of the phase discrimination module 14, the standard frequency is gradually increased until the middle precision vector phase difference value is in the linear phase area of the phase discrimination module 14, and the middle precision standard frequency is stored to be f m If the current medium precision vector phase difference value is in the linear phase area of the phase discrimination module 14, the time delay of the adjustable light delay line 8 is slightly increased and decreased, the position of the linear phase area after the rising area or the falling area and before the time delay fine adjustment is determined, and the medium precision vector phase difference information lambda is stored M Late entry low precision vector phase difference measurement lambda L (ii) a Selecting from f for low-precision vector phase difference measurement time frequency m The method comprises the following steps of/10 starting to measure the low-precision vector phase difference value, gradually increasing the standard frequency until the middle-precision vector phase difference value is in the linear phase area of the phase discrimination module 14 if the current low-precision vector phase difference value is in the nonlinear phase area of the phase discrimination module 14, and storing the low-precision standard frequency as f L If the current low-precision vector phase difference value is in the linear phase area of the phase discrimination module 14, the time delay of the adjustable light delay line 8 is increased and decreased, the position of the linear phase area after the rising area or the falling area and before the time delay fine adjustment is determined, and precision vector phase difference information lambda is stored L . Is stored in a measurement and control processing moduleHigh, medium, low precision vector phase difference information λ in 9 H 、λ M 、λ L As the initial phase of the link.
The backtracking and real-time locking process of the link phase refers to reading the high, medium and low precision standard frequency information f stored in the measurement and control processing module 9 max 、f m 、f L And high, medium and low precision vector phase difference value information lambda H 、λ M 、λ L Then, the initial phase state of the original phase calibration timing of the link is reached through low, medium and high precision standard frequency and loop standard frequency phase demodulation and the adjustment of the adjustable optical delay line 8 according to the phase difference of the phase demodulation, then the real-time locking purpose of the link phase locking is reached through high precision phase difference measurement and the real-time adjustment of the adjustable optical delay line 8, and when the delay line reaches the limit range, an initialization program is started; because the adjustable range of the adjustable optical delay line 8 is designed to be 2 times of the delay variation range of the optical fiber link where the adjustable optical delay line is located due to the change of the environmental temperature, the situation that the delay line reaches the limit range cannot occur in the normal situation. The flow chart of the backtracking and real-time locking of the link phase is shown in fig. 3.
The phase discrimination refers to the vector phase difference measurement of the reference standard frequency and the loopback standard frequency. The detailed process includes that a measurement and control processing module 9 controls a scalable frequency source to output a scaling frequency signal, the scaling frequency signal is divided into two parts by a power divider 11, one part is input into a combiner 5 at a reference end of a phase discrimination module 14, the light signal is converted into a light signal by an electro-optical conversion module 6 and then input through a port of a first optical circulator 7, the light signal is output to an adjustable optical delay line 8 through three ports of a second optical circulator 15 after passing through the adjustable optical delay line 8 and a transmission long fiber 2 respectively, the light signal is looped back to a splitter 16 at two ports of the second optical circulator 15, 10% of light is split by the splitter 16 and input through a port of the second optical circulator 15, the light is input through three ports, the original paths of the transmission long fiber 2 and the adjustable optical delay line 8 are returned to three ports of the first optical circulator 7, the light is input through two ports of the first optical circulator 7 to a first photoelectric conversion module 12 for photoelectric conversion and amplification of a radio frequency signal and then output to a radio frequency filter 13, the remaining band stop signal is filtered, the same frequency signal is input to the measurement and fed back to the two paths of the measurement and control processing module 14, and the phase discrimination frequency signal is fed back to the two paths of the phase discrimination module 14. The detailed phase detection process is shown in fig. 4 and is performed by steps 1 to 17.
The phase discrimination linear phase interval refers to that the phase discrimination result of two paths of same-frequency signals input to the phase discrimination module 14 is relatively accurate within a certain phase difference range, as shown in fig. 5, for example, the phase discrimination module 14 taking AD8302 as a core is taken as an example, the AD8302 phase discriminator has a phase discrimination linear phase rising area (-150 ° -30 °) and a phase discrimination linear phase falling area (+ 150 ° -30 °), the phase discrimination error in the two phase difference intervals is less than 1 °, and the phase discrimination error in other phase difference intervals is relatively large.
The invention does not need to multiplex time delay measuring light wavelength and phase measuring light in a transmission optical fiber channel, efficiently solves the problem of stable phase transmission of time-frequency signals of the distributed radar array, and can lock the time delay and the phase of a link in a stable state before the system is restarted.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
Claims (10)
1. A time-frequency signal phase-locked transmission system is characterized in that,
the phase-locked transmission system comprises a phase-locked transmission front-end unit, a transmission long optical fiber and a phase-locked transmission rear-end unit;
the transmission long optical fiber is connected with the phase-locked transmission front-end unit, and the phase-locked transmission rear-end unit is connected with the transmission long optical fiber.
2. The time-frequency signal phase-locked transmission system of claim 1,
the phase-locked transmission front-end unit comprises a first time-frequency band pass filter, a combiner, an electro-optical conversion module, a first optical circulator, an adjustable light delay line, a measurement and control processing module, a variable standard frequency source, a power divider, a first photoelectric conversion module, a time-frequency band elimination filter and a phase discrimination module;
the combiner is connected with the first time-frequency band-pass filter, the electro-optical conversion module is connected with the combiner, the first optical circulator is connected with the electro-optical conversion module, the adjustable light delay line is connected with the first optical circulator and the transmission long optical fiber, the measurement and control processing module is connected with the adjustable light delay line, the variable standard frequency source is connected with the measurement and control processing module, the power divider is connected with the variable standard frequency source and the combiner, the first photoelectric conversion module is connected with the first optical circulator, the time-frequency band-stop filter is connected with the first photoelectric conversion module, and the phase discrimination module is connected with the power divider, the time-frequency band-stop filter and the measurement and control processing module.
3. The time-frequency signal phase-locked transmission system as claimed in claim 2,
the phase-locked transmission rear-end unit comprises a second optical circulator, a light splitter, a second photoelectric conversion module and a second time-frequency band-pass filter;
the second optical circulator is connected with the transmission long optical fiber, the optical splitter is connected with the second optical circulator, the second photoelectric conversion module is connected with the optical splitter, and the second time-frequency band-pass filter is connected with the second photoelectric conversion module.
4. The time-frequency signal phase-locked transmission system according to claim 3,
the first time-frequency band-pass filter filters out-of-band interference signals and harmonic component signals of input time-frequency signals; the adjustable light delay line adjusts the delay amount according to the control information of the measurement and control processing module, returns to the middle point of the adjustable range of the time delay when the system is initialized, and is formed by combining a temperature control optical fiber and a motor-driven space light delay line; the measurement and control processing module is used for storing and reading the locked chainThe variable standard frequency source is used for receiving the control of the measurement and control processing module, sending standard frequency signals with different frequencies as required to obtain delay phase information with different precisions, and outputting three standard frequency signals, namely a low-precision standard frequency f L Middle precision standard frequency f M High-precision standard frequency f H The system scales the frequency f with high precision corresponding to the phase/time delay difference measurement with high, medium and low precision respectively H Calibrating vector phase difference change with highest precision and calibrating frequency f with medium and low precision M 、f L A nominal time delay difference of wherein H Is equal to f max ，f max The highest frequency supported by the phase demodulation module, the intermediate frequency standard frequency f M Recommended value range of f H /5～f H 10, low frequency scale frequency f L Recommended value range of f H /5～f H /10。
5. The time-frequency signal phase-locked transmission system according to claim 4,
the time frequency signal enters the phase-locked transmission front-end unit, the transmission long optical fiber and the phase-locked transmission rear-end unit complete two functions of time frequency transmission and link phase-locked control, the time frequency transmission function ensures the purity of the transmission time frequency signal, and the link phase-locked control ensures the backtracking and the stability of the time frequency transmission phase.
6. The time-frequency signal phase-locked transmission system according to claim 5,
a time-frequency signal is input into the phase-locked transmission front-end unit, firstly, the filtered time-frequency signal and a standard frequency signal are synthesized into a mixed radio-frequency signal in the combiner through the first time-frequency band pass filter and then output to the electro-optical conversion module, the electro-optical conversion module performs electro-optical conversion on the mixed radio-frequency signal and outputs optical power to the No. 1 input port of the first optical circulator, then the mixed radio-frequency signal is output to the adjustable optical delay line through the No. 3 port, and the phase of the mixed radio-frequency signal is adjusted through the adjustable optical delay line and then is connected with the transmission long optical fiber; the optical signal is transmitted to the phase-locked transmission rear-end unit through the transmission long optical fiber, in the phase-locked transmission rear-end unit, the input light firstly passes through a 3-port of the second optical circulator, is output to the optical splitter through a 2-port of the second optical circulator, passes through a main path signal of the optical splitter and is output to the second photoelectric conversion module, the optical signal in the second photoelectric conversion module is changed into a radio-frequency signal, and then is amplified and output to the second time-frequency band-pass filter, the radio-frequency signal input to the second time-frequency band-pass filter comprises a time-frequency signal, a standard-frequency signal and a mixing signal of the time-frequency signal and the standard-frequency signal derived due to nonlinearity of the electro-optic/photoelectric conversion module, and the second time-frequency band-pass filter filters other out-band signals and then keeps the time-frequency signal output.
7. The time-frequency signal phase-locked transmission system according to claim 6,
the link phase locking control function comprises the realization of two working scenes, namely the realization during system initialization and the realization during system restart; the realization of the link phase locking control function during system initialization comprises the calibration of link phase information, the backtracking and real-time locking of link phases; backtracking and locking the link phase in real time when the system is restarted; the system initialization has two triggering conditions, namely the system initialization is triggered through the measurement and control processing module, and the adjustable light delay line reaches the adjustment limit range.
8. The time-frequency signal phase-locked transmission system according to claim 7,
when the phase calibration process is started, the original stored calibration frequency/phase information is cleared, and the measurement and control processing module controls and adjusts the calibration frequency (f) on the basis of the regression midpoint of the optical delay line i ) The vector phase difference measurement of the reference standard frequency and the loopback standard frequency is carried out under high, medium and low precision, and the vector phase difference value is ensured to be in the linear phase of the phase discrimination moduleA zone; the adjustment of the adjustable light delay line is controlled and operated by the measurement and control processing module, after a phase calibration process is started, the original stored standard frequency/phase information is cleared firstly, then the light delay line returns to the middle point, and the highest standard frequency (f) is carried out max ) If the measurement and control processing module judges that the currently measured high-precision measurement vector phase difference value is in a nonlinear phase region, the adjustable optical delay line is adjusted until the adjustable optical delay line is in the linear phase region; if the current high-precision measurement vector phase difference value is in a linear phase region, slightly increasing and decreasing the time delay of the adjustable light delay line at the point, determining whether the linear phase region is in a rising region or a falling region and then regressing the position before fine adjustment of the time delay, and storing high-precision vector phase difference information lambda H Late entry medium precision vector phase difference measurement lambda M (ii) a Selecting from f when measuring medium precision vector phase difference max And/10 starting to measure the intermediate precision vector phase difference value, gradually increasing the standard frequency until the intermediate precision vector phase difference value is in the linear phase region of the phase discrimination module if the intermediate precision vector phase difference value is in the nonlinear phase region of the phase discrimination module, and storing the intermediate precision standard frequency with the frequency f m If the current medium precision vector phase difference value is in the linear phase area of the phase discrimination module, the time delay of the adjustable light delay line is increased and decreased, the position of the linear phase area before the time delay fine adjustment is determined to be returned after the rising area or the falling area, and precision vector phase difference information lambda is stored M Late entry low precision vector phase difference measurement lambda L (ii) a Selecting from f for low-precision vector phase difference measurement time frequency m The method comprises the following steps of/10 starting to measure the low-precision vector phase difference value, gradually increasing the standard frequency until the middle-precision vector phase difference value is in the linear phase area of the phase discrimination module if the current low-precision vector phase difference value is in the nonlinear phase area of the phase discrimination module, and storing the low-precision standard frequency with the frequency f L If the current low-precision vector phase difference value is in the linear phase area of the phase discrimination module, the time delay of the adjustable light delay line is increased and decreased, the position of the linear phase area before time delay fine adjustment is determined to be returned after the rising area or the falling area, and precision vector phase difference information lambda is stored L (ii) a Stored in the measurement and control processHigh, medium and low precision vector phase difference information lambda in module H 、λ M 、λ L As the initial phase of the link.
9. The time-frequency signal phase-locked transmission system of claim 8,
the backtracking and real-time locking of the link phase can firstly read the high, medium and low precision standard frequency information f stored in the measurement and control processing module max 、f m 、f L And high, medium and low precision vector phase difference information lambda H 、λ M 、λ L And then the adjustable light delay line is adjusted through low, medium and high-precision standard frequency and loop standard frequency phase demodulation and according to the phase difference of the phase demodulation, and the initial phase state of the original phase calibration timing of the link is reached.
10. The time-frequency signal phase-locked transmission system of claim 9,
the phase demodulation is a vector phase difference measurement of a reference standard frequency and a loopback standard frequency, the detailed process is that the measurement and control processing module controls a scalable frequency source to output a standard frequency signal, the standard frequency signal is divided into two parts by the power divider, one part of the standard frequency signal is input into the combiner at the reference end of the phase demodulation module, the standard frequency signal is converted into an optical signal by the electro-optical conversion module, the optical signal is input through one port and output to the adjustable optical delay line through three ports of the first optical circulator, then the optical signal is respectively connected into the three ports of the second optical circulator through the adjustable optical delay line and the transmission long fiber, after the two ports of the second optical circulator output light to the light divider, the light splitter divides 10% of light to be input through one port of the second optical circulator, and the light is input through the three ports, returned to the three ports of the first optical circulator through the transmission long fiber and the original path of the adjustable optical delay line, the two ports of the first optical circulator input to the first photoelectric conversion module for photoelectric conversion and amplification of a radio frequency signal, then the phase demodulation module outputs the amplified signal to the three ports of the first optical circulator, and the two ports of the phase demodulation module retain the input time frequency signal, and the two channels of the measurement and control processing module, and the phase demodulation module retain the input time frequency signal.
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