CN111954298A - Clock synchronization device and system suitable for millimeter wave radio frequency remote module - Google Patents
Clock synchronization device and system suitable for millimeter wave radio frequency remote module Download PDFInfo
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- CN111954298A CN111954298A CN202010862377.3A CN202010862377A CN111954298A CN 111954298 A CN111954298 A CN 111954298A CN 202010862377 A CN202010862377 A CN 202010862377A CN 111954298 A CN111954298 A CN 111954298A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
- H04W56/001—Synchronization between nodes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
- H04W88/08—Access point devices
- H04W88/085—Access point devices with remote components
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The invention discloses a clock synchronization device and a system suitable for a millimeter wave radio frequency remote module, wherein the device comprises a time frequency subsystem and at least one time frequency terminal subsystem; the time frequency subsystem comprises a GPS/Beidou time service receiving unit, a time code unit, a frequency scale unit, an optical transmitter and an external time frequency system interface, and the external time frequency system interface is used for accessing synchronous information and a reference clock of an external time frequency system; the time-frequency terminal subsystem comprises N optical receivers and N frequency scale shunt modules which are in one-to-one correspondence with the optical receivers, wherein the input ends of the optical receivers are connected with the optical transmitters in the time code units; each optical receiver corresponds to one synchronous information output and one reference clock output of the optical transmitter. The invention can meet the requirement of the millimeter wave RRU front end on a high-performance clock.
Description
Technical Field
The present invention relates to a radio remote technology, and in particular, to a clock synchronization device and system suitable for a millimeter wave radio remote module.
Background
At present, a structure with separate baseband and radio frequency is widely used in a mobile communication system, wherein a baseband processing part constitutes a baseband module, generally called bbu (base Band unit), and a radio frequency processing part constitutes a radio Remote unit, generally called rru (radio Remote unit). By adopting the radio remote module, the problems of difficult site selection of a machine room, reduced feeder loss and the like can be solved, and the system efficiency is improved. The clock synchronization technology is a key technology of the radio remote unit.
In recent years, with the increasing crowding of low-frequency band spectrum and the increasing requirements of users on broadband communication technology, the millimeter wave is applied to mobile communication more and more. The millimeter wave is adopted in mobile communication, so that a wider working frequency band can be obtained, the communication capacity is increased, and a narrower beam can be realized, so that a higher EIRP value is obtained, the size of a terminal antenna is reduced, the application prospect is very wide, and the method belongs to the main development direction of the future mobile communication technology.
The BBU and the RRU typically communicate using an optical interface, which includes a transceiver module and SERDES (serial data transceiver), and the data transmission rate is up to several Gbps. In the current RRU system, a commonly used method is to extract a BBU clock signal from a high-speed transmitted data stream by using a phase-locked loop to generate a RRU clock signal. The clock signal of the RRU needs to meet the following clock requirements: 1. the requirement of clock precision; 2. phase noise and jitter requirements of the clock; 3. clock synchronization requirements. Because the millimeter wave RRU works in a millimeter wave frequency band, higher working frequency of the millimeter wave RRU puts higher requirements on the performance of the clock, and particularly under the condition of cascade connection of multiple stages of RRUs, the clock precision can show a nonlinear deterioration increasing trend along with the increase of the number of stages, so that the cascade requirements of more stages cannot be met. It can be seen that the existing clock scheme for recovering the RRU from the BBU cannot meet the requirement of the front end of the millimeter-wave RRU on a high-performance clock, and therefore a new clock synchronization method is needed to solve the problem.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a clock synchronization device and a clock synchronization system suitable for a millimeter wave remote radio module.
The purpose of the invention is realized by the following technical scheme: a clock synchronization device suitable for a millimeter wave radio frequency remote module comprises a time frequency subsystem and at least one time frequency terminal subsystem;
the time frequency subsystem comprises a GPS/Beidou time service receiving unit, a time code unit, a frequency scale unit, an optical transmitter and an external time frequency system interface, and the external time frequency system interface is used for accessing synchronous information and a reference clock of an external time frequency system;
the input end of the time code unit is respectively connected with the GPS/Beidou time service receiving unit and an external time frequency system interface, and is used for generating N +1 paths of synchronous information according to time information from the GPS/Beidou time service receiving unit or synchronous information of the external time frequency system, wherein N paths of synchronous information are output outwards, and the other path of synchronous information is divided into N paths by an optical transmitter and then is transmitted to the time frequency terminal subsystem; the input end of the frequency scaling unit is connected with an external time frequency system interface, and the frequency scaling unit is used for providing a reference clock for the time code unit according to reference clock information from an external time frequency system or a local rubidium clock and generating N +1 paths of reference clocks, wherein the N paths of reference clocks are output outwards, and the other path of reference clock is divided into N paths by an optical transmitter and then is transmitted to each time frequency terminal subsystem;
each time-frequency terminal subsystem comprises N optical receivers and N frequency scale shunt modules which are in one-to-one correspondence with the optical receivers, and in each time-frequency terminal subsystem, the input ends of the optical receivers are connected with the optical transmitters in the time code units; each optical receiver corresponds to one path of synchronous information output and one path of reference clock output of the optical transmitter; the optical receiver outputs the received synchronous information to the outside, transmits the received synchronous information to the corresponding frequency scale shunt module after receiving the reference clock, and sends k paths of signals to k clock output modules after the frequency scale shunt module performs shaping, filtering and amplifying to obtain k paths of reference clock output to the outside.
Preferably, the GPS \ beidou receiving unit comprises a GPS receiver and a beidou receiver which are mutually backup, wherein the GPS receiver is used for receiving a GPS satellite navigation signal and generating UTC time information and a 1PPS reference signal; the Beidou receiver is used for receiving a second-generation Beidou satellite navigation signal and generating UTC time information and a 1PPS reference signal.
Furthermore, the time code unit comprises a receiving module, a time code generating module, a time code shunting module and a time code monitoring module;
the receiving module is used for receiving UTC time information and 1PPS reference signals output by the GPS receiver or the Beidou receiver and transmitting the UTC time information and the 1PPS reference signals to the time code generating module;
the time code generating module is used for coding the time information from the receiving module to obtain synchronous information, dividing the frequency of the reference clock from the frequency standard unit to obtain a 1Hz signal, realizing the synchronization with the 1PPS second signal, alarming when the synchronization error between the 1Hz signal and the 1PPS second signal is greater than the index requirement, and automatically starting resynchronization;
the time code shunting module is used for shunting the synchronous information obtained by coding or the synchronous information from an external time frequency system interface to generate N +1 paths of synchronous information;
and the time code monitoring module is used for monitoring and controlling the state of each module of the time code unit and outputting monitoring information to the outside through a self-contained serial port.
Further, the frequency scale unit comprises a rubidium clock, a first signal change-over switch, a phase-locked loop A, a phase-locked loop B, a second signal change-over switch, a signal shunt module, a display control panel, a frequency scale monitoring unit and an N +1 clock output module;
one input end of the first signal change-over switch is connected with the external time-frequency system interface and is connected with an external video system reference clock, the other input end of the first signal change-over switch is connected with the rubidium clock, the output end of the first signal change-over switch is respectively connected with a phase-locked loop A and a phase-locked loop B, the output ends of the phase-locked loop A and the phase-locked loop B are both connected with the input end of a second signal change-over switch, the output end of the second signal change-over switch is connected with a signal shunt module, the received reference clock is divided into N +1 paths by the signal shunt module to generate N +1 paths of reference signals, and each path of reference signal is transmitted to a clock output module to be output;
the first signal switch selects a reference clock sent by an external time frequency system by default; the phase-locked loop A and the phase-locked loop B are mutually hot backup and are low-noise narrow-band phase-locked loops;
the frequency scale monitoring unit is used for controlling the first signal change-over switch to automatically switch to the internal rubidium clock when the reference clock sent by the external time-frequency system fails; when one phase-locked loop fails, the second signal change-over switch is controlled to automatically switch to the other phase-locked loop; and at the same time of switching, a display control panel connected with the frequency scale monitoring unit carries out alarm indication and reports equipment faults through a monitoring serial port.
Further, the optical transmitter comprises a modulation module, a multiplexer, an optical amplifier, an optical splitter, a light source with the wavelength of lambda 1 and a light source with the wavelength of lambda 2;
the modulation module is used for modulating two signals of the synchronous information and the reference clock onto an optical signal through two light sources with different wavelengths respectively;
the multiplexer is used for combining two optical signals with different wavelengths onto one optical fiber in a wavelength division multiplexing mode, amplifying the optical signals by an optical amplifier and transmitting the amplified optical signals to the optical splitter;
the optical splitter is used for splitting the received optical signals into N paths, and each path of signals is transmitted to an optical receiver in the time-frequency terminal subsystem through an optical fiber.
Further, the optical receiver comprises a demultiplexer and a demodulation module;
a demultiplexer in the optical receiver separates optical signals with wavelengths of lambda 1 and lambda 2 through wavelength division demultiplexing, two different optical signals are restored into synchronous information and a reference clock through a demodulation module, the synchronous information is output outwards, and the reference clock is transmitted to a corresponding frequency scale branching module.
Furthermore, the frequency scale splitting module comprises a buffer module and K clock output modules, wherein the input end of the buffer module receives a reference clock from the optical receiver, and the buffer module is used for shaping, filtering and amplifying the received reference clock, dividing the reference clock into K paths, transmitting the K paths of reference clock to the K clock output modules, and outputting the K paths of reference clock by the K clock output modules.
A clock synchronization system suitable for a millimeter wave remote radio module comprises a clock synchronization device and a plurality of remote radio assemblies;
each group of radio remote units comprises a base band processing module BBU, each base band processing module BBU is connected with at least one radio remote module RRU through an optical fiber, and each radio remote module RRU is connected with at least one radio front end;
the BBU in each radio remote unit and the time-frequency subsystem of the clock synchronization device are located in the same BBU distribution area, and the synchronization information and the reference clock output by the time-frequency subsystem are respectively transmitted to the BBU of each radio remote unit, so as to provide time-frequency reference for each BBU;
the RRUs in each remote radio unit are distributed in one or more RRU distribution areas, each RRU distribution area is provided with one time-frequency terminal subsystem, and the RRUs and the radio frequency terminals connected with the RRUs are located in the same RRU distribution area;
and the synchronous information output by each time-frequency terminal subsystem is respectively transmitted to each RRU in the RRU distribution area where the time-frequency terminal subsystem is located, and the reference clock output by each time-frequency terminal subsystem is respectively transmitted to each RRU and the radio frequency front end in the RRU distribution area where the time-frequency terminal subsystem is located.
The invention has the beneficial effects that: the invention provides time-frequency signals for the BBU, the RRU and the radio frequency front end by adding the independent high-performance time-frequency subsystem and the time-frequency terminal subsystem, and can meet the requirement of the millimeter wave RRU front end on a high-performance clock.
Drawings
Fig. 1 is a schematic block diagram of a time-frequency synchronization system.
Fig. 2 is a schematic block diagram of a time-frequency subsystem.
Fig. 3 is a schematic block diagram of a time code unit.
Fig. 4 is a schematic block diagram of a frequency scale unit.
Fig. 5 is a schematic block diagram of light emission.
Fig. 6 is a working block diagram of single-channel wavelength division multiplexing demultiplexing.
Fig. 7 is a block diagram of a time-frequency terminal subsystem.
Fig. 8 is a schematic block diagram of a frequency scale branching unit.
Fig. 9 is a functional block diagram of a clock synchronization system.
Detailed Description
The technical solutions of the present invention are further described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the following.
As shown in fig. 1, a clock synchronization apparatus suitable for a millimeter wave remote radio module includes a time-frequency subsystem and at least one time-frequency terminal subsystem;
as shown in fig. 2, the time-frequency subsystem includes a GPS/beidou time service receiving unit, a time code unit, a frequency scale unit, an optical transmitter, and an external time-frequency system interface, where the external time-frequency system interface is used to access synchronization information and a reference clock of an external time-frequency system;
the input end of the time code unit is respectively connected with the GPS/Beidou time service receiving unit and an external time frequency system interface, and is used for generating N +1 paths of synchronous information according to time information from the GPS/Beidou time service receiving unit or synchronous information of the external time frequency system, wherein N paths of synchronous information are output outwards, and the other path of synchronous information is divided into N paths by an optical transmitter and then is transmitted to the time frequency terminal subsystem; the input end of the frequency scaling unit is connected with an external time frequency system interface, and the frequency scaling unit is used for providing a reference clock for the time code unit according to reference clock information from an external time frequency system or a local rubidium clock and generating N +1 paths of reference clocks, wherein the N paths of reference clocks are output outwards, and the other path of reference clock is divided into N paths by an optical transmitter and then is transmitted to each time frequency terminal subsystem;
in the embodiment of the application, the GPS/Beidou receiving unit comprises a GPS receiver and a Beidou receiver which are mutually backed up, wherein the GPS receiver is used for receiving a GPS satellite navigation signal and generating UTC time information and a 1PPS reference signal; the Beidou receiver is used for receiving a second-generation Beidou satellite navigation signal and generating UTC time information and a 1PPS reference signal.
As shown in fig. 3, the time code unit includes a receiving module, a time code generating module, a time code splitting module, and a time code monitoring module;
the receiving module is used for receiving UTC time information and 1PPS reference signals output by the GPS receiver or the Beidou receiver and transmitting the UTC time information and the 1PPS reference signals to the time code generating module;
the time code generating module is used for coding the time information from the receiving module to obtain synchronous information, dividing the frequency of the reference clock from the frequency standard unit to obtain a 1Hz signal, realizing the synchronization with the 1PPS second signal, alarming when the synchronization error between the 1Hz signal and the 1PPS second signal is greater than the index requirement, and automatically starting resynchronization;
the time code shunting module is used for shunting the synchronous information obtained by coding or the synchronous information from an external time frequency system interface to generate N +1 paths of synchronous information;
and the time code monitoring module is used for monitoring and controlling the state of each module of the time code unit and outputting monitoring information to the outside through a self-contained serial port.
As shown in fig. 4, the frequency scale unit includes a rubidium clock, a first signal switch, a phase-locked loop a, a phase-locked loop B, a second signal switch, a signal splitting module, a display control panel, a frequency scale monitoring unit, and an N +1 clock output module;
one input end of the first signal change-over switch is connected with the external time-frequency system interface and is connected with an external video system reference clock, the other input end of the first signal change-over switch is connected with the rubidium clock, the output end of the first signal change-over switch is respectively connected with a phase-locked loop A and a phase-locked loop B, the output ends of the phase-locked loop A and the phase-locked loop B are both connected with the input end of a second signal change-over switch, the output end of the second signal change-over switch is connected with a signal shunt module, the received reference clock is divided into N +1 paths by the signal shunt module to generate N +1 paths of reference signals, and each path of reference signal is transmitted to a clock output module to be output;
the first signal switch selects a reference clock sent by an external time frequency system by default; the phase-locked loop A and the phase-locked loop B are mutually hot backup and are low-noise narrow-band phase-locked loops;
the frequency scale monitoring unit is used for controlling the first signal change-over switch to automatically switch to the internal rubidium clock when the reference clock sent by the external time-frequency system fails; when one phase-locked loop fails, the second signal change-over switch is controlled to automatically switch to the other phase-locked loop; and at the same time of switching, a display control panel connected with the frequency scale monitoring unit carries out alarm indication and reports equipment faults through a monitoring serial port.
As shown in fig. 5, the optical transmitter includes a modulation module, a multiplexer, an optical amplifier, an optical splitter, a light source with a wavelength λ 1, and a light source with a wavelength λ 2;
the modulation module is used for modulating two signals of the synchronous information and the reference clock onto an optical signal through two light sources with different wavelengths respectively;
the multiplexer is used for combining two optical signals with different wavelengths onto one optical fiber in a wavelength division multiplexing mode, amplifying the optical signals by an optical amplifier and transmitting the amplified optical signals to the optical splitter;
the optical splitter is used for splitting the received optical signals into N paths, and each path of signals is transmitted to an optical receiver in the time-frequency terminal subsystem through an optical fiber.
Each time-frequency terminal subsystem comprises N optical receivers and N frequency scale shunt modules which are in one-to-one correspondence with the optical receivers, and in each time-frequency terminal subsystem, the input ends of the optical receivers are connected with the optical transmitters in the time code units; each optical receiver corresponds to one path of synchronous information output and one path of reference clock output of the optical transmitter; the optical receiver outputs the received synchronous information to the outside, transmits the received synchronous information to the corresponding frequency scale shunt module after receiving the reference clock, and sends k paths of signals to k clock output modules after the frequency scale shunt module performs shaping, filtering and amplifying to obtain k paths of reference clock output to the outside.
As shown in fig. 6, a wavelength division multiplexing/demultiplexing operation block diagram is shown, where a Wavelength Division Multiplexing (WDM) technology is a technology for simultaneously transmitting optical signals with multiple wavelengths in one optical fiber, and a basic principle thereof is to modulate various information onto optical signals with different wavelengths at a transmitting end, and then multiplex the optical signals carrying the information into the same optical fiber through a Multiplexer (MUX) for unidirectional transmission; after the signals are transmitted to a receiving end, optical signals with various wavelengths are separated through a Demultiplexer (DMUX) and then demodulated, so that the transmission of a plurality of optical signals with different wavelengths is completed. Wavelength division multiplexing is essentially a Frequency Division Multiplexing (FDM) technique in the optical domain, where each channel of a WDM system achieves a division of the frequency domain by a division of the frequency domain.
As shown in fig. 7, the optical receiver includes a demultiplexer and a demodulation module;
a demultiplexer in the optical receiver separates optical signals with wavelengths of lambda 1 and lambda 2 through wavelength division demultiplexing, two different optical signals are restored into synchronous information and a reference clock through a demodulation module, the synchronous information is output outwards, and the reference clock is transmitted to a corresponding frequency scale branching module.
As shown in fig. 8, the frequency scale splitting module includes a buffering module and K clock output modules, and in the embodiment of the present application, the buffering module includes a shaping module, a filtering module, an amplifying module, and a power divider, which are connected in sequence; the input end of the buffer module receives a reference clock from an optical receiver, and the buffer module is used for shaping, filtering and amplifying the received reference clock, dividing the reference clock into K paths, transmitting the K paths of reference clock to K clock output modules, and outputting the K paths of reference clock by the K clock output modules.
As shown in fig. 9, a clock synchronization system suitable for a millimeter wave remote radio module includes the clock synchronization apparatus and multiple sets of remote radio modules;
each group of radio remote units comprises a base band processing module BBU, each base band processing module BBU is connected with at least one radio remote module RRU through an optical fiber, and each radio remote module RRU is connected with at least one radio front end;
the BBU in each radio remote unit and the time-frequency subsystem of the clock synchronization device are located in the same BBU distribution area, and the synchronization information and the reference clock output by the time-frequency subsystem are respectively transmitted to the BBU of each radio remote unit, so as to provide time-frequency reference for each BBU; in the embodiment of the application, when the number of the baseband processing modules BBUs is greater than the number of the paths of the synchronous clocks or the reference clocks externally output by the time-frequency subsystem, one path of the synchronous clocks or the reference clocks can be shunted by the power divider, so that all BBUs can obtain the synchronous information and the reference clocks. Of course, this is only an example of an embodiment, and in an actual design process, a specific number of step clocks and reference clock paths may be designed in advance, so that the number of step clocks or reference clock paths is consistent with the number of BBUs, or the number of output paths is greater than the number of BBUs.
The RRUs in each remote radio unit are distributed in one or more RRU distribution areas, each RRU distribution area is provided with one time-frequency terminal subsystem, and the RRUs and the radio frequency terminals connected with the RRUs are located in the same RRU distribution area;
and the synchronous information output by each time-frequency terminal subsystem is respectively transmitted to each RRU in the RRU distribution area where the time-frequency terminal subsystem is located, and the reference clock output by each time-frequency terminal subsystem is respectively transmitted to each RRU and the radio frequency front end in the RRU distribution area where the time-frequency terminal subsystem is located. In the embodiment of the application, when the number of the RRUs in a certain RRU distribution area is greater than the number of the paths of the synchronization information output by the time-frequency terminal subsystem, one path of the synchronization information can be branched by the power divider, so that all the RRUs in the area can obtain the synchronization information; when the number of the RRUs and the radio frequency front end in a certain RRU distribution area and the number of output paths greater than the reference clock are counted, one path of the reference clock can be branched through a power divider so as to report that all the RRUs and the radio frequency front end in the area can obtain the reference clock; certainly, this is only an example of an embodiment, and in an actual design process, a specific output path number may be designed in advance, and the number of synchronization information output paths of the time-frequency terminal subsystem is consistent with or greater than the number of RRUs in the area, so that the number of reference clock output paths of the time-frequency terminal subsystem is consistent with or greater than the total number of RRUs and radio frequency front ends in the area.
In the embodiment of the application, the time-frequency subsystem is configured to directly provide synchronization information and a reference clock for 2 BBUs, and the time-frequency subsystem sends the time-frequency information to 2 RRUs and 2 optical receivers of the time-frequency terminal subsystem near the radio frequency front end through optical fibers. In the embodiment, a time frequency subsystem and the time frequency terminal subsystem are required to provide synchronization information and reference clocks for a BBU, an RRU and a radio frequency front end to ensure that each device synchronously works under uniform time and frequency, and specifically, the time frequency subsystem generates 3 paths of synchronization information through a satellite signal or an external time frequency system, and generates 3 paths of reference clocks through a local rubidium clock or an external reference clock. And 2 paths of time frequency signals generated by the time frequency subsystem provide time frequency reference for the BBU, and 1 path of generated time frequency signals are divided into 2 paths by the optical transmitter, then are pulled far by the optical fiber and are sent to 2 optical receivers in the time frequency terminal subsystem. In the time-frequency terminal subsystem, an optical receiver and a frequency scale branching module provide time-frequency reference for an RRU and a radio frequency front end.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the methods described in the foregoing embodiments, such as changes in names of the methods and antenna forms. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. The utility model provides a clock synchronization device suitable for millimeter wave radio frequency zooming out module which characterized in that: the system comprises a time-frequency subsystem and at least one time-frequency terminal subsystem;
the time frequency subsystem comprises a GPS/Beidou time service receiving unit, a time code unit, a frequency scale unit, an optical transmitter and an external time frequency system interface, and the external time frequency system interface is used for accessing synchronous information and a reference clock of an external time frequency system;
the input end of the time code unit is respectively connected with the GPS/Beidou time service receiving unit and an external time frequency system interface, and is used for generating N +1 paths of synchronous information according to time information from the GPS/Beidou time service receiving unit or synchronous information of the external time frequency system, wherein N paths of synchronous information are output outwards, and the other path of synchronous information is divided into N paths by an optical transmitter and then is transmitted to the time frequency terminal subsystem; the input end of the frequency scaling unit is connected with an external time frequency system interface, and the frequency scaling unit is used for providing a reference clock for the time code unit according to reference clock information from an external time frequency system or a local rubidium clock and generating N +1 paths of reference clocks, wherein the N paths of reference clocks are output outwards, and the other path of reference clock is divided into N paths by an optical transmitter and then is transmitted to each time frequency terminal subsystem;
each time-frequency terminal subsystem comprises N optical receivers and N frequency scale shunt modules which are in one-to-one correspondence with the optical receivers, and in each time-frequency terminal subsystem, the input ends of the optical receivers are connected with the optical transmitters in the time code units; each optical receiver corresponds to one path of synchronous information output and one path of reference clock output of the optical transmitter; the optical receiver outputs the received synchronous information to the outside, transmits the received synchronous information to the corresponding frequency scale shunt module after receiving the reference clock, and sends k paths of signals to k clock output modules after the frequency scale shunt module performs shaping, filtering and amplifying to obtain k paths of reference clock output to the outside.
2. The clock synchronization device of claim 1, wherein the clock synchronization device is adapted to a millimeter wave remote radio module, and comprises: the GPS/Beidou receiving unit comprises a GPS receiver and a Beidou receiver which are mutually backed up, and the GPS receiver is used for receiving GPS satellite navigation signals and generating UTC time information and 1PPS reference signals; the Beidou receiver is used for receiving a second-generation Beidou satellite navigation signal and generating UTC time information and a 1PPS reference signal.
3. The clock synchronization device of claim 2, wherein the clock synchronization device is adapted to a millimeter wave remote radio module, and comprises: the time code unit comprises a receiving module, a time code generating module, a time code shunting module and a time code monitoring module;
the receiving module is used for receiving UTC time information and 1PPS reference signals output by the GPS receiver or the Beidou receiver and transmitting the UTC time information and the 1PPS reference signals to the time code generating module;
the time code generating module is used for coding the time information from the receiving module to obtain synchronous information, dividing the frequency of the reference clock from the frequency standard unit to obtain a 1Hz signal, realizing the synchronization with the 1PPS second signal, alarming when the synchronization error between the 1Hz signal and the 1PPS second signal is greater than the index requirement, and automatically starting resynchronization;
the time code shunting module is used for shunting the synchronous information obtained by coding or the synchronous information from an external time frequency system interface to generate N +1 paths of synchronous information;
and the time code monitoring module is used for monitoring and controlling the state of each module of the time code unit and outputting monitoring information to the outside through a self-contained serial port.
4. The clock synchronization device of claim 3, wherein the clock synchronization device is adapted to a millimeter wave remote radio module, and comprises: the frequency scale unit comprises a rubidium clock, a first signal change-over switch, a phase-locked loop A, a phase-locked loop B, a second signal change-over switch, a signal shunt module, a display control panel, a frequency scale monitoring unit and an N +1 clock output module;
one input end of the first signal change-over switch is connected with the external time-frequency system interface and is connected with an external video system reference clock, the other input end of the first signal change-over switch is connected with the rubidium clock, the output end of the first signal change-over switch is respectively connected with a phase-locked loop A and a phase-locked loop B, the output ends of the phase-locked loop A and the phase-locked loop B are both connected with the input end of a second signal change-over switch, the output end of the second signal change-over switch is connected with a signal shunt module, the received reference clock is divided into N +1 paths by the signal shunt module to generate N +1 paths of reference signals, and each path of reference signal is transmitted to a clock output module to be output;
the first signal switch selects a reference clock sent by an external time frequency system by default; the phase-locked loop A and the phase-locked loop B are mutually hot backup and are low-noise narrow-band phase-locked loops;
the frequency scale monitoring unit is used for controlling the first signal change-over switch to automatically switch to the internal rubidium clock when the reference clock sent by the external time-frequency system fails; when one phase-locked loop fails, the second signal change-over switch is controlled to automatically switch to the other phase-locked loop; and at the same time of switching, a display control panel connected with the frequency scale monitoring unit carries out alarm indication and reports equipment faults through a monitoring serial port.
5. The clock synchronization device of claim 1, wherein the clock synchronization device is adapted to a millimeter wave remote radio module, and comprises: the optical transmitter comprises a modulation module, a multiplexer, an optical amplifier, an optical splitter, a light source with the wavelength of lambda 1 and a light source with the wavelength of lambda 2;
the modulation module is used for modulating two signals of the synchronous information and the reference clock onto an optical signal through two light sources with different wavelengths respectively;
the multiplexer is used for combining two optical signals with different wavelengths onto one optical fiber in a wavelength division multiplexing mode, amplifying the optical signals by an optical amplifier and transmitting the amplified optical signals to the optical splitter;
the optical splitter is used for splitting the received optical signals into N paths, and each path of signals is transmitted to an optical receiver in the time-frequency terminal subsystem through an optical fiber.
6. The clock synchronization device of claim 5, wherein the clock synchronization device is adapted to a millimeter wave remote radio module, and comprises: the optical receiver comprises a demultiplexer and a demodulation module;
a demultiplexer in the optical receiver separates optical signals with wavelengths of lambda 1 and lambda 2 through wavelength division demultiplexing, two different optical signals are restored into synchronous information and a reference clock through a demodulation module, the synchronous information is output outwards, and the reference clock is transmitted to a corresponding frequency scale branching module.
7. The clock synchronization device of claim 6, wherein the clock synchronization device is adapted to a millimeter wave remote radio module, and comprises: the frequency scale shunting module comprises a buffer module and K clock output modules, wherein the input end of the buffer module receives a reference clock from the optical receiver, and the buffer module is used for shaping, filtering and amplifying the received reference clock, dividing the reference clock into K paths and transmitting the K paths of reference clock to the K clock output modules, and the K clock output modules output the K paths of reference clock.
8. The clock synchronization system suitable for the millimeter wave remote radio module according to claim 1, wherein the clock synchronization device according to any one of claims 1 to 7 is adopted, and the clock synchronization system further comprises: the system comprises the clock synchronization device and a plurality of groups of radio remote units;
each group of radio remote units comprises a base band processing module BBU, each base band processing module BBU is connected with at least one radio remote module RRU through an optical fiber, and each radio remote module RRU is connected with at least one radio front end;
the BBU in each radio remote unit and the time-frequency subsystem of the clock synchronization device are located in the same BBU distribution area, and the synchronization information and the reference clock output by the time-frequency subsystem are respectively transmitted to the BBU of each radio remote unit, so as to provide time-frequency reference for each BBU;
the RRUs in each remote radio unit are distributed in one or more RRU distribution areas, each RRU distribution area is provided with one time-frequency terminal subsystem, and the RRUs and the radio frequency terminals connected with the RRUs are located in the same RRU distribution area;
and the synchronous information output by each time-frequency terminal subsystem is respectively transmitted to each RRU in the RRU distribution area where the time-frequency terminal subsystem is located, and the reference clock output by each time-frequency terminal subsystem is respectively transmitted to each RRU and the radio frequency front end in the RRU distribution area where the time-frequency terminal subsystem is located.
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