WO2014176719A1 - Carrier synchronization method and device - Google Patents

Abstract

Provided are a carrier synchronization method and device. By means of steps such as zero crossing comparison, edge capture, determining the mark-space ratio, frequency control, carrier synthesis, phase difference elimination and the like, the carrier synchronization method reduces the requirements for hardware while reducing carrier synchronization delay, and is capable of being used for suppressing the phase jitter of a signal.

Description

 Method and device for carrier synchronization

 The present invention relates to the field of communications technologies, and in particular, to a method and device for carrier synchronization. Background technique

 In the field of communication technology, time division duplexing (TDD) is a commonly used transmission mode. In the TDD system using the TDD mode, the uplink and downlink communication transmissions use the same frequency band, and the number of time slots is allocated according to the service requirement of the uplink communication or the downlink communication. If the downlink communication traffic is large, more time slots are allocated for the downlink communication. If the amount of uplink communication traffic is large, a larger number of slots are allocated for uplink communication.

 As shown in Figure 1, one time slot of the TDD system corresponds to one TDD frame, and one TDD frame consists of the following three parts: TDD time slot guard interval, TDD synchronization code, TDD effective payload. The same TDD time slot length, the shorter the TDD time slot protection interval, the higher the TDD effective payload ratio, and the higher the TDD effective payload ratio, the larger the capacity of each TDD bearer service. Or, shortening the TDD time slot protection interval and correspondingly reducing the TDD effective payload, the time length occupied by each TDD frame can be reduced while ensuring the TDD payload ratio is unchanged, thereby enhancing the flexibility of the TDD system. Sex. Therefore, shortening the TDD time slot protection interval can effectively improve the performance of the TDD system.

 As shown in Figure 2, the TDD time slot protection interval is mainly composed of four parts, including RF switch, RF circuit delay, automatic gain control stabilization delay, carrier synchronization delay, and algorithm convergence delay. Among them, the carrier synchronization delay accounts for a considerable part, which has an important impact on the performance of the TDD system.

 The existing carrier synchronization method, whether it is the square ring method or the Costas loop method, uses a phase-locked loop, and there is a feedback loop, and the loop stabilization takes a long time, and the carrier synchronization delay is large.

Summary of the invention

In view of this, the embodiments of the present invention provide a method and a device for carrier synchronization, which can reduce the carrier synchronization delay. In a first aspect, an embodiment of the present invention provides a method for carrier synchronization, including: performing a zero-cross comparison on a modulated signal, and outputting a first level when the amplitude of the modulated signal is greater than zero, in a modulated signal When the amplitude is less than zero, the second level is output, wherein the first level is higher than the second level; the level change point of the output after the zero-cross comparison is determined, and the output after the zero-cross comparison is determined by the first power When the level is changed to the second level, the first pulse signal is output, and when the output after the zero-cross comparison is changed from the second level to the first level, the second pulse signal is output; according to the first pulse signal and the second pulse a signal, an output frequency control word; synthesizing a carrier according to the frequency control word; and canceling the phase difference by phase-shifting the synthesized carrier according to a phase difference between the synthesized carrier and the modulated signal. With reference to the first aspect, in a first possible implementation, the phase-shifted carrier is divided into a first carrier and a second carrier; the first carrier and the modulated signal are mixed; The carrier carries out 90. Phase shifting, and mixing the phased second carrier with the modulated signal. In combination with the first aspect and the first possible implementation manner of the first aspect, in a second possible implementation, the outputting the frequency control word according to the first pulse signal and the second pulse signal, specifically: Determining, by the first pulse signal and the second pulse signal, a first duration and a second duration corresponding to each of the adjacent first level and the second level, according to the first duration and the second duration, Output frequency control word. In combination with the first aspect and the first and second possible implementation manners of the first aspect, in a third possible implementation, the frequency control word is output according to the first pulse signal and the second pulse signal, Specifically, the method includes: determining, according to the first pulse signal and the second pulse signal, a duty ratio of the first level or the second level; and outputting the frequency control word according to the duty ratio of the first level or the second level . Specifically, determining the duty ratio of the first level or the second level according to the first pulse signal and the second pulse signal, specifically: determining, by using the first pulse signal and the second pulse signal, determining the adjacent Determining a first level or a second level of the first level and the second level, respectively, determining a duty ratio of the first level or the second level according to the first duration and the second duration; Outputting the frequency control word according to the duty ratio of the first level or the second level, specifically comprising: if the duty ratio of the first level or the second level is equal to the preset value, according to the first duration or the second Determining and outputting a frequency control word, wherein the preset value is a duty ratio of a carrier for carrying a signal in the communication system; if a duty ratio of the first level or the second level is not equal to The preset value outputs the same frequency control word as the previous frequency control word. Further, determining the first voltage signal according to the first duration, or determining the second voltage signal according to the second duration; according to the first voltage signal or the second voltage signal, at the voltage signal and the frequency Query in the correspondence table of the control word, determine The frequency control word is output. In a second aspect, a device for carrier synchronization is provided, which can be used for carrier synchronization. The device includes: a zero-crossing comparison module, configured to perform zero-cross comparison on a modulated signal, and output a first power when the amplitude of the modulated signal is greater than zero. Level, when the amplitude of the modulation signal is less than zero, outputting a second level, wherein the first level is higher than the second level; the edge capture module is configured to determine a level change point of the output after the zero-cross comparison, and When the output after the zero-cross comparison is changed from the first level to the second level, the first pulse signal is output, and when the output after the zero-cross comparison is changed from the second level to the first level, the second pulse signal is output; a frequency control module, configured to output a frequency control word according to the first pulse signal and the second pulse signal; a carrier synthesis module, configured to synthesize a carrier according to the frequency control word; and a phase difference cancellation module, configured to use the synthesized carrier And a phase difference of the modulated signal, the phase difference is eliminated by phase shifting the synthesized carrier. With reference to the second aspect, in a first possible implementation, the device further includes: a carrier separation module, configured to divide the phase-shifted carrier into a first path carrier and a second path carrier; a module, configured to perform mixing processing on the first carrier and the modulated signal; and a second mixing processing module, configured to perform 90 on the second carrier. Phase shifting, and mixing the phased second carrier with the modulated signal. With reference to the second aspect, and the first possible implementation manner of the second aspect, in a second possible implementation, the frequency control module is specifically configured to: determine a phase according to the first pulse signal and the second pulse signal The first duration and the second duration of the adjacent first level and the second level respectively output a frequency control word according to the first duration and the second duration. With reference to the second aspect, and the first and second possible implementation manners of the second aspect, in a third possible implementation, the frequency control module is specifically configured to: according to the first pulse signal and the second pulse a signal determining a duty ratio of the first level or the second level; and outputting the frequency control word according to the duty ratio of the first level or the second level. The frequency control module is specifically configured to: determine a duty ratio of the first level or the second level according to the first pulse signal and the second pulse signal; and occupy a space according to the first level or the second level Ratio, output frequency control word. More specifically, the frequency control module is specifically configured to: determine, according to the first pulse signal and the second pulse signal, a first duration and a second duration corresponding to each of the adjacent first level and the second level According to the first duration and a second duration, determining a duty ratio of the first level or the second level; if the duty ratio of the first level or the second level is equal to the preset value, determining according to the first duration or the second duration And outputting a frequency control word, where the preset value is a duty ratio of a carrier used to carry a signal in the communication system; if a duty ratio of the first level or the second level is not equal to the preset value, The same frequency control word as the previous frequency control word is output. The method and device for carrier synchronization provided by the embodiments of the present invention use an open-loop carrier synchronization structure to perform zero-cross comparison of the received modulated signals, edge capture, duty ratio determination, frequency control, carrier synthesis, and shift. The phase processing and the like directly extract the carrier of the signal from the received modulated signal. The open-loop carrier synchronization structure shortens the carrier synchronization delay and improves the performance of the TDD system. DRAWINGS

The drawings used in the embodiments or the description of the prior art are briefly described. It is obvious that the drawings in the following description are some embodiments of the present invention, and are not creative to those skilled in the art. Other drawings can also be obtained from these drawings on the premise of labor.

 1 is a schematic diagram of a slot structure in a TDD frame;

 2 is a schematic diagram of a slot guard interval structure in a TDD frame;

 Figure 3 is a structural diagram of a receiver;

 4 is a schematic structural diagram of a device for carrier synchronization in Embodiment 1 of the present invention;

 FIG. 5 is a flowchart of a method for carrier synchronization in Embodiment 2 of the present invention. The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. The embodiments are a part of the embodiments of the invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

Embodiment 1 The embodiment of the present invention provides a device for carrier synchronization, which can be applied to the figure. In the receiver shown in Fig. 3, it serves as a carrier synchronization module of the receiver. The receiver receives the communication signal and needs to process the received signal to recover the transmitted signal. As shown in FIG. 3, the receiver processing process generally includes the following steps: signal reception, signal filtering, signal amplification, mixing, carrier synchronization, analog to digital conversion, and demodulation. Of course, the device provided by the embodiment of the present invention can also be applied to other communication devices, as an integral part of the carrier synchronization function, or can be used as a device to implement carrier synchronization, which is not limited in this embodiment of the present invention. Carrier synchronization, also known as carrier recovery, is to generate a local carrier in the receiving device that is in phase with the carrier of the received modulated signal, and supplies it to the demodulator for coherent demodulation. The device for carrier synchronization provided in this embodiment includes a zero-crossing comparison module, an edge capture module, a frequency control module, a carrier synthesis module, and a phase difference cancellation module. Optionally, the method further includes a carrier separation module, a first mixing processing module, and a second mixing processing module. As shown in FIG. 4, the zero-crossing comparison module is configured to perform a zero-cross comparison of the modulated signal, and output a first level when the amplitude of the modulated signal is greater than zero, and output a second level when the amplitude of the modulated signal is less than zero. Wherein the first level is higher than the second level; the edge capture module is configured to determine a level change point of the output after the zero-cross comparison, and the output after the zero-cross comparison is changed from the first level to the second level At the level, the first pulse signal is output, and when the output after the zero-cross comparison is changed from the second level to the first level, the second pulse signal is output; the frequency control module is configured to: according to the first pulse signal and the second a pulse signal, an output frequency control word; a carrier synthesis module, configured to synthesize a carrier according to the frequency control word; and a phase difference cancellation module, configured to: move the synthesized carrier according to a phase difference between the synthesized carrier and the modulated signal The phase cancels the phase difference. Specifically, the frequency control module is specifically configured to: determine, according to the first pulse signal and the second pulse signal, a first duration and a second duration corresponding to each of the adjacent first level and the second level, A frequency control word is output based on the first duration and the second duration. Or the frequency control module is specifically configured to: determine, according to the first pulse signal and the second pulse signal, a duty ratio of the first level or the second level; according to the first level or the second level Duty cycle, output frequency control word. More specifically, the frequency control module is specifically configured to: determine, according to the first pulse signal and the second pulse signal, a first duration and a second corresponding to each of the adjacent first level and the second level a duration, determining a duty ratio of the first level or the second level according to the first duration and the second duration; if the duty ratio of the first level or the second level is equal to a preset value, Determining and outputting a frequency control word according to the first duration or the second duration, the preset value being a duty ratio of a carrier for carrying a signal in the communication system; if the first level or the second level The duty ratio is not equal to the preset value, and the same frequency control word as the previous frequency control word is output. Determining and outputting the frequency control word according to the first duration or the second duration, specifically: determining the first voltage signal according to the first duration, or determining the second according to the second duration The voltage signal is queried according to the first voltage signal or the second voltage signal in a correspondence table between the voltage signal and the frequency control word, and the frequency control word is determined and output. Further, the device for carrier synchronization further includes: a carrier separation module, configured to divide the phase-shifted carrier into a first carrier and a second carrier; and a first mixing processing module, configured to: The modulated signal is subjected to mixing processing; the second mixing processing module is configured to perform phase shifting of the second carrier by 90°, and mixing the phase-shifted second carrier with the modulated signal. The specific explanation of each module will be given below. The zero-crossing comparison module can be a comparator, or even further a zero-crossing comparator. The zero-crossing comparison module has a threshold voltage of 0V. When the amplitude value of the received signal is greater than 0, a constant amplitude value is output, that is, the first level. When the amplitude value of the received signal is less than 0, the output is output. The other amplitude value is also the second level. The amplitude value referred to herein refers to a voltage amplitude value. Alternatively, the first level may be a positive amplitude value +P, and the second level may be a negative amplitude value -P. The first level and the second level may also be other values. As long as the two are different, they can be distinguished from each other. The specific values of the embodiments of the present invention are not limited. The edge capture module can also be implemented with a comparator. The edge capture module triggers the output of the zero-crossing comparison module, captures the edge of the amplitude value change trigger, and outputs the edge indication signal. That is, when the output of the zero-crossing comparison module changes from the first level to the second level, or when the second level changes to the first level, the edge capture module outputs an edge indication signal. Specifically, the edge capture process is a level comparison, and when the level changes, the edge of the amplitude value is captured. Taking the first level and the second level as +P and -P respectively, when the output of the zero-crossing comparison module is changed from +P to -P, the edge capture module outputs the first pulse signal, and the zero-crossing comparison module Output by -P When it becomes +P, the edge capture module outputs a second pulse signal. The first pulse signal may be a positive pulse, and the second pulse signal may be a negative pulse; or the second pulse signal may be a positive pulse, and the first pulse signal may be a negative pulse. Optionally, the frequency control module may include two clock chips. The first pulse signal triggers the first clock chip to start timing, the second pulse signal triggers the end timing, and the timing duration is the first duration; the second pulse signal triggers the second clock chip to start timing, and the first pulse signal ends timing, timing The duration is the second duration. The corresponding duration can be converted into a voltage signal within the clock chip. Then, according to the corresponding first duration and the second duration, the frequency of generating the carrier can be determined, thereby outputting the corresponding frequency control word. Certainly, the corresponding first duration and the second duration need to be first converted into corresponding first voltage signals and second voltage signals, and the frequency control module according to the corresponding first voltage signals and second voltage signals, Determine and output the corresponding frequency control word. Optionally, a clock chip can also be implemented, such as the first pulse signal triggering timing, the second pulse signal ending timing, thereby obtaining a second duration of the second level, the frequency control module according to the length of the second duration and the advance The stored duty cycle determines the corresponding frequency control word that should be output. For example, the pre-stored duty cycle is 50%. In the case where the carrier does not shake, in fact, the frequency control module is equivalent to obtaining the first duration of the first level. In another optional solution, the frequency control module may first determine a duty ratio of the first level or the second level according to the first pulse signal and the second pulse signal; The duty cycle of the second level, the output frequency control word. The duty cycle in the embodiment of the present invention is used to describe the ratio of the duration of the first level or the second level in a period to the total time. The first level and the second level are always alternately present, and the total time during which the adjacent first level and the second level continue may be referred to as one period. Specifically, the frequency control module can include two clock chips and one comparator. First, the duty ratio is determined, or the duty ratio is measured. The duty cycle measurement can be timed using two clock chips: the first pulse signal triggers the first clock chip to start timing, the second pulse signal triggers the end timing, and the timing duration For the first duration; the second pulse signal triggers the second clock chip to start timing, the first pulse signal ends the timing, and the timing duration is the second duration. The corresponding duration can be converted into a voltage signal within the clock chip. The comparator outputs the voltage signals output by the two clock chips. If the voltage values are the same, the duty ratio is 50%, otherwise they are not equal. In summary, the first duration can be used to characterize the duration of the second level in one cycle, and the second duration is used to characterize a week The duration of the first level during the period. Of course, other methods, such as determining the duty cycle based on the ratio of the first level or the second level duration in two or more cycles to the total time. Alternatively, the duty cycle measurement module may also have only one clock chip. Once the first pulse signal and the second pulse signal are received, the next timing is started before the end of the line, and the method is used for the original carrier used to carry the signal. The case where the space ratio is 50% is particularly suitable because in this case, the durations of the first level and the second level tend to be the same. After the duration is measured, the duty cycle is determined by the first voltage value converted by the first duration and the second voltage value converted by the second duration, wherein the corresponding voltage value is proportional to the duration. If the duty ratio is equal to the preset value, the preset value is the duty ratio of the carrier used to carry the signal in the communication system used by the device for the carrier synchronization, and can be set as needed. Then, according to the corresponding first voltage converted first voltage signal or the second duration converted second voltage signal, the corresponding voltage signal and the frequency control word correspondence table are queried. Wherein the duty ratio of the first level is equal to the first level duration divided by the sum of the first level duration and the second level duration, and is also equal to the first voltage signal divided by the first voltage signal and the second voltage The sum of the signals. Therefore, when the duty ratio is equal to the preset value, only one of the first voltage signal and the second voltage signal is needed to know the other value, so only one of the voltage signals can be in the corresponding correspondence. The corresponding frequency control word is queried in the table, and of course two voltage signals can be used. The voltage signal in the correspondence table between the voltage signal and the frequency control word may be the first voltage signal, the second voltage signal, or a sum of the two. Preferably, the preset value of the duty ratio is 50%. Correspondingly, when the determined duty ratio is 50%, the corresponding relationship table is queried according to the corresponding voltage signal to obtain a corresponding frequency control word; when the determined duty ratio is not 50%, the output and the previous frequency control are performed. The same frequency control word. It should be noted that, in general, the probability that the duty ratio is exactly equal to the preset value is relatively small, such as a preset value of 50%, and the duty ratio is 50.5%, which should be understood by those skilled in the art. Equal to "allows an error within a certain range. A carrier synthesis module that synthesizes and outputs a corresponding carrier according to a frequency control word output by the frequency control module. The frequency control word is the word that controls the frequency, changes the content of the frequency control word, and controls the occurrence and change of the frequency. Using the frequency control word, the composite carrier is prior art, Not bad.

The phase difference cancellation module includes at least one phase shifter. Since the previous steps process brings a corresponding delay, the carrier frequency of the frequency synthesis output has a certain phase difference with the carrier frequency of the bearer signal. The phase difference can be measured using a manual measurement method, and then the phase shifter is used to compensate for the phase difference between the synthesized frequency and the modulated signal, so that the combined carrier frequency is perfectly aligned with the carrier frequency of the carrier signal. Specifically, after manually measuring the delay, the extracted carrier frequency is used as a reference to convert to a corresponding phase value, and is configured to the phase shifter. Since the delay is relatively fixed, the corresponding phase difference only needs to be measured once and can be used continuously. Optionally, the device for carrier synchronization may further include a carrier separation module, a first mixing processing module, and a second mixing processing module. The carrier separation module may be a power splitter. The device for carrier synchronization provided by the embodiment of the present invention uses the open-loop carrier extraction structure, and does not need the carrier stabilization time required by the feedback carrier extraction structure, does not need to wait for the carrier to be stable, extracts the direct output of the carrier, and greatly reduces the carrier synchronization delay. Time. In addition, the device avoids multiple frequency doubling of the signal, has a simple structure, low hardware requirements, and reduces cost. At the same time, the duty ratio determination method is also adopted. If the signal carrier has phase jitter, the previous frequency control word is output, thereby ensuring that the synthesized carrier does not change with the wrong carrier variation, and the phase jitter of the signal is suppressed. Embodiment 2 As shown in FIG. 6, an embodiment of the present invention provides a method for carrier synchronization. The method can use the device described in the first embodiment, and the device of the embodiment can use the method of the embodiment. The two embodiments can be mutually verified, and the details can refer to each other. The carrier synchronization method includes: performing a zero-cross comparison on the modulated signal, and outputting a first level when the amplitude of the modulated signal is greater than zero, and outputting a second level when the amplitude of the modulated signal is less than zero, wherein the first electrical Level higher than the second level; determining the level change point of the output after the zero-cross comparison, and outputting the first pulse signal at the zero-crossing when the output after the zero-cross comparison is changed from the first level to the second level The second pulse signal is output when the compared output changes from the second level to the first level; the frequency control word is output according to the first pulse signal and the second pulse signal; and the carrier is synthesized according to the frequency control word; Optionally, the method may further include: dividing the phase-shifted carrier into a first carrier and a first Two-way carrier; mixing the first carrier with the modulated signal; performing 90 for the second carrier. Phase shifting, and mixing the phased second carrier with the modulated signal. Specifically, outputting the frequency control word according to the first pulse signal and the second pulse signal, specifically: determining, according to the first pulse signal and the second pulse signal, adjacent first level and second level Corresponding first duration and second duration, the frequency control word is output according to the first duration and the second duration. Alternatively, optionally, outputting the frequency control word according to the first pulse signal and the second pulse signal, specifically: determining, according to the first pulse signal and the second pulse signal, the first level or the second level Duty cycle; The frequency control word is output according to the duty ratio of the first level or the second level. Specifically, determining the duty ratio of the first level or the second level according to the first pulse signal and the second pulse signal, specifically: determining, by using the first pulse signal and the second pulse signal, determining the adjacent Determining a first level or a second level of the first level and the second level, respectively, determining a duty ratio of the first level or the second level according to the first duration and the second duration; Outputting the frequency control word according to the duty ratio of the first level or the second level, specifically comprising: if the duty ratio of the first level or the second level is equal to the preset value, according to the first duration or the second Determining and outputting a frequency control word, wherein the preset value is a duty ratio of a carrier for carrying a signal in the communication system; if a duty ratio of the first level or the second level is not equal to The preset value outputs the same frequency control word as the previous frequency control word. Specifically, determining, according to the first duration or the second duration, the frequency control word, specifically: determining the first voltage signal according to the first duration, or determining the second according to the second duration The voltage signal is queried according to the first voltage signal or the second voltage signal in a correspondence table between the voltage signal and the frequency control word, and the frequency control word is determined and output. Further, the frequency control word is output according to the duty ratio, and specifically includes: if the duty ratio is the carrier synchronization method provided by the embodiment of the present invention, the open loop carrier extraction structure is used, and no feedback carrier extraction is needed. The carrier stabilization time required by the structure, the carrier synchronization method of the open-loop structure directly extracts the carrier from the signal carrier, does not need to wait for the carrier to be stable, extracts the direct output of the carrier, and greatly reduces the carrier synchronization delay. In addition, the method avoids multiple frequency doubling of the signal, has low hardware requirements, and reduces cost. At the same time, the duty ratio determination method is also used. If the signal carrier has phase jitter, the previous frequency control word is output, thereby ensuring that the synthesized carrier does not follow the error. The erroneous carrier changes and changes the phase jitter of the signal. A person skilled in the art can understand that all or part of the steps of implementing the above method embodiments may be completed by using hardware related to program instructions, and the foregoing program may be stored in a computer readable storage medium, and the program is executed when executed. The foregoing storage medium includes: ROM, RAM, magnetic disk or optical disk, etc., which can store various program codes. Finally, the above embodiments are only used to illustrate the technology of the present invention. The invention is not limited thereto; although the invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions described in the foregoing embodiments may still be modified, or Some or all of the technical features are equivalently substituted; and the modifications or substitutions do not depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

claims 1. A carrier synchronization method, applied in communication systems, characterized in that the method includes: performing a zero-crossing comparison on the modulated signal, and when the amplitude of the modulated signal is greater than zero, outputting the first level, when the modulated signal When the amplitude is less than zero, the second level is output, where the first level is higher than the second level; the level change point of the output after the zero-crossing comparison is determined, and the output after the zero-crossing comparison is determined by the first level. When the level changes to the second level, the first pulse signal is output, and when the output after the zero-crossing comparison changes from the second level to the first level, the second pulse signal is output; According to the first pulse signal and the second pulse signal, output a frequency control word; synthesize a carrier wave according to the frequency control word; eliminate the phase difference by phase-shifting the synthesized carrier wave according to the phase difference between the synthesized carrier wave and the modulation signal. 2. The method according to claim 1, characterized in that, the method further includes: dividing the phase-shifted carrier into a first carrier and a second carrier; performing frequency mixing processing on the first carrier and the modulated signal ; Perform 90 on the second carrier. Phase shift, and mix the phase-shifted second carrier with the modulated signal. 3. The method according to claim 1 or 2, characterized in that, according to the first pulse signal and the second pulse signal, outputting a frequency control word specifically includes: according to the first pulse signal and the second pulse signal, The first duration and the second duration respectively corresponding to the adjacent first level and the second level are determined, and the frequency control word is output according to the first duration and the second duration. 4. The method according to claim 1 or 2, characterized in that, according to the first pulse signal and the second pulse signal, outputting a frequency control word specifically includes: According to the first pulse signal and the second pulse signal, the duty cycle of the first level or the second level is determined; according to the duty cycle of the first level or the second level, the frequency control word is output. 5. The method according to claim 4, wherein determining the duty cycle of the first level or the second level according to the first pulse signal and the second pulse signal specifically includes: according to the first pulse signal The pulse signal and the second pulse signal determine the first duration and the second duration corresponding to the adjacent first level and the second level respectively, and determine the first level based on the first duration and the second duration. The duty cycle of the first level or the second level; According to the duty cycle of the first level or the second level, the output frequency control word specifically includes: If the duty cycle of the first level or the second level is equal to the preset Set a value, determine and output the frequency control word according to the first duration or the second duration, wherein the preset value is the duty cycle of the carrier used to carry signals in the communication system; if the first level or The duty cycle of the second level is not equal to the preset value, and the same frequency control word as the previous frequency control word is output. 6. The method according to claim 5, characterized in that, determining and outputting a frequency control word according to the first duration or the second duration, specifically comprising: determining a first voltage signal according to the first duration, or, according to The second duration determines a second voltage signal; according to the first voltage signal or the second voltage signal, the correspondence table between the voltage signal and the frequency control word is queried to determine the frequency control word and output it. 7. A carrier synchronization device, the device includes: a zero-crossing comparison module, used to perform zero-crossing comparison on the modulation signal, and output the first level when the amplitude of the modulation signal is greater than zero, and when the amplitude of the modulation signal is less than When zero, the second level is output, where the first level is higher than the second level; the edge capture module is used to determine the level change point of the output after zero-crossing comparison, and the output after zero-crossing comparison is When the first level changes to the second level, the first pulse signal is output, and when the output after the zero-crossing comparison changes from the second level to the first level, the second pulse signal is output; The frequency control module is used to output the frequency control word according to the first pulse signal and the second pulse signal; the carrier synthesis module is used to synthesize the carrier according to the frequency control word; the phase difference elimination module is used to synthesize the carrier according to the synthesized carrier and the phase difference of the modulated signal, and the phase difference is eliminated by phase-shifting the synthesized carrier wave. 8. The device according to claim 7, characterized in that, the device further includes: a carrier separation module, used to divide the phase-shifted carrier into a first carrier and a second carrier; a first mixing processing module , used for mixing the first carrier and the modulated signal; the second mixing processing module is used for 90 the second carrier. The phase is shifted, and the phase-shifted second carrier wave and the modulated signal are mixed. 9. The device according to claim 7 or 8, characterized in that the frequency control module is specifically configured to: determine the adjacent first level and the second level according to the first pulse signal and the second pulse signal. The frequency control word is output according to the first duration and the second duration respectively corresponding to the first duration and the second duration. 10. The device according to claim 7 or 8, characterized in that the frequency control module is specifically configured to: determine the occupancy of the first level or the second level according to the first pulse signal and the second pulse signal. Duty cycle; According to the duty cycle of the first level or the second level, the frequency control word is output. 11. The device according to claim 10, characterized in that, the frequency control module is specifically configured to: determine, according to the first pulse signal and the second pulse signal, the adjacent first level and the second level corresponding to each other. The first duration and the second duration, determine the duty cycle of the first level or the second level according to the first duration and the second duration; If the duty cycle of the first level or the second level is equal to a preset value, the frequency control word is determined and output according to the first duration or the second duration. The preset value is used to carry the frequency in the communication system. The duty cycle of the carrier wave of the signal; if the duty cycle of the first level or the second level is not equal to the preset value, output the same frequency control word as the previous frequency control word. 12. The device according to claim 10, characterized in that, the frequency control module is specifically configured to: determine, according to the first pulse signal and the second pulse signal, the adjacent first level and the second level corresponding to each other. The first duration and the second duration, determine the duty cycle of the first level or the second level according to the first duration and the second duration; if the first level or the second level The duty cycle is equal to the preset value, the first voltage signal is determined according to the first duration, or the second voltage signal is determined according to the second duration, and the first voltage signal or the second voltage signal is determined according to the first voltage signal or the second voltage signal. Query the corresponding relationship between the voltage signal and the frequency control word in the table to determine the frequency control word and output it; if the duty cycle of the first level or the second level is not equal to the preset value, the output is the same as the previous frequency control word. words are the same as the frequency control words.