Crystal oscillator frequency offset correction method for scatter communication in motion, communication device and system

Abstract

The invention provides a crystal oscillator frequency offset correction method for scatter communication in motion, a communication device and a system, and relates to the technical field of scatter communication. The crystal oscillator frequency offset correction method is applied to a slave station and comprises the following steps: calculating local frequency offset according to a received signal; the local frequency offset is sent to an opposite terminal station; receiving a frequency offset value sent by the master station, and calculating local crystal oscillator frequency offset according to the local frequency offset and the frequency offset value sent by the master station; and adjusting the local crystal oscillator according to the frequency offset of the local crystal oscillator to complete the correction of the frequency offset of the crystal oscillator. According to the invention, separation of crystal oscillator deviation and Doppler frequency shift can be effectively realized under the condition of communication in motion, and calculation, tracking and correction of crystal oscillator frequency offset of each slave station in the system can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of scatter communication, in particular to a crystal oscillator frequency offset correction method, a communication device and a system for scatter moving target indication. BACKGROUND

[0002] In a scatter communication system, the clock of each scatter device needs to maintain relatively stable frequency consistency to eliminate the carrier frequency offset and timing deviation caused by clock frequency deviation, and ensure that the transmission performance of the system is not affected. The early scatter communication system used a rubidium atomic clock with high stability and accuracy as the clock source of the scatter device, so that the entire system had a negligible clock frequency deviation. However, the rubidium atomic clock has the disadvantages of high price, large size, and long preheating time.

[0003] With the development of the scatter communication system, the rubidium atomic clock in the scatter communication system is gradually replaced by a temperature-controlled crystal oscillator. The frequency stability and accuracy of the temperature-controlled crystal oscillator are both worse than those of the rubidium atomic clock, so a precise clock frequency offset estimation method must be used to correct the temperature-controlled crystal oscillator. In a moving target indication scatter system, the scatter device is stationary, and there is no Doppler frequency offset in the signal frequency offset, so the signal frequency offset is mainly caused by clock deviation. The clock deviation can be obtained by directly detecting the frequency offset of the signal. However, as the scatter system is expanded to moving target indication applications, the signal frequency offset is superimposed with the Doppler shift caused by the movement of the scatter device, which is constantly changing. The existing method of directly detecting the signal frequency offset cannot directly obtain the clock deviation, and cannot be applied to the crystal oscillator frequency offset correction of the scatter moving target indication system. SUMMARY

[0004] Therefore, the present application provides a crystal oscillator frequency offset correction method, a communication device and a system for scatter moving target indication, which can solve the problem that the existing crystal oscillator frequency offset estimation method cannot be applied to the scatter moving target indication system.

[0005] The technical scheme adopted by the present application is as follows:

[0006] A crystal oscillator frequency offset correction method for scatter moving target indication is applied to a slave station of a communication system, and includes the following steps:

[0007] Step 1: calculating a local frequency offset according to a received signal;

[0008] Step 2: sending the local frequency offset to a peer station;

[0009] Step 3: receiving a frequency offset value sent by a master station, and calculating a local crystal oscillator frequency offset according to the local frequency offset and the frequency offset value sent by the master station;

[0010] Step 4: adjusting the local crystal oscillator according to the local crystal oscillator frequency offset, and completing the correction of the crystal oscillator frequency offset;

[0011] Step 5, repeating steps 1 to 4, realizes the tracking and correction of the crystal frequency deviation.

[0012] Further, in step 3, the local crystal frequency deviation is calculated in the following way:

[0013] (1) Calculate the carrier frequency deviation Δf carrier1 :

[0014] According to the above relationship, the local frequency deviation value and the master station frequency deviation value can be calculated, and the calculation formula is as follows:

[0015] Δf carrier1 =( f1- f2) / 2

[0016] Wherein, f1 is the local frequency deviation, f2 is the frequency deviation value sent by the master station;

[0017] (2) Calculate the local crystal frequency deviation Δf:

[0018] Δf=(Δf carrier1 / f carrier )* f

[0019] Wherein, f carrier is the carrier frequency used for communication, and f is the frequency of the local crystal.

[0020] A communication device, which executes the method as described above, comprising:

[0021] The local frequency deviation calculation module is used for calculating the local frequency deviation according to the received signal;

[0022] The frequency deviation sending module is used for sending the local frequency deviation to the opposite station;

[0023] The crystal frequency deviation calculation module is used for receiving the frequency deviation value sent by the master station, and calculating the local crystal frequency deviation according to the local frequency deviation and the frequency deviation value sent by the master station;

[0024] The crystal frequency adjustment module is used for adjusting the local crystal according to the local crystal frequency deviation, and completing the correction of the crystal frequency deviation.

[0025] A communication system, comprising a plurality of slave stations and a master station, wherein the slave stations are the communication devices as described above, and the master station comprises:

[0026] The local frequency deviation calculation module is used for calculating the local frequency deviation according to the received signal;

[0027] The frequency deviation sending module is used for sending the local frequency deviation to the opposite station.

[0028] The beneficial effects of the present application compared with the prior art are:

[0029] 1、The present application is simple and easy to implement, and is convenient to realize.

[0030] 2、The application can effectively realize the separation of the crystal oscillator deviation and the Doppler shift in the case of mobile communication, and realize the calculation, tracking and correction of the crystal oscillator frequency deviation of each slave station in the system. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0032] Figure 1 is an application scenario of a crystal oscillator frequency deviation correction method for scattering mobile communication provided by the embodiment of the present application.

[0033] Figure 2 is a flowchart of a slave station in the embodiment of the present application.

[0034] Figure 3 is a flowchart of a master station in the embodiment of the present application.

[0035] Figure 4 is a structural schematic diagram of a slave station in the embodiment of the present application.

[0036] Figure 5 is a structural schematic diagram of a master station in the embodiment of the present application.

[0037] Figure 6 is a schematic diagram of a device terminal provided by the embodiment of the present application. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present application more clear, the following will be described by specific embodiments in combination with the drawings.

[0039] A crystal oscillator frequency deviation correction method for scattering mobile communication is applied to a slave station of a communication system, and includes the following steps:

[0040] Step 1: calculating the local frequency deviation according to the received signal;

[0041] Step 2: sending the local calculated frequency deviation value to the opposite station;

[0042] Step 3: receiving the frequency deviation value sent by the master station, and calculating the local crystal oscillator frequency deviation according to the local calculated frequency deviation value and the frequency deviation value calculated by the master station;

[0043] In the case of mobile communication, the local frequency deviation f1 includes the Doppler shift f Doppler1 and the carrier frequency deviation Δf carrier1 , that is:

[0044] f1= f Doppler1 +Δf carrier1

[0045] Among them, f Doppler1 The Doppler frequency shift, Δf, is caused by the relative movement of the two ends during mobile communication. carrier1 The carrier frequency offset is caused by the inconsistency in the crystal oscillator frequencies of the two communication terminals.

[0046] The frequency offset value f2 transmitted by the master station includes the Doppler frequency shift f. Doppler2 and carrier frequency offset Δf carrier2 ,Right now:

[0047] f2= f Doppler2 +Δf carrier2

[0048] The Doppler shift is caused by relative movement, and the effect is the same for both the slave and master stations, therefore:

[0049] f Doppler2 = f Doppler1

[0050] The carrier frequency offset is caused by the inconsistent frequency offsets of the crystal oscillators at both ends. The effects on the slave station and the master station are opposite, therefore:

[0051] Δf carrier2 = -Δf carrier1

[0052] Based on the above relationship, the carrier frequency offset can be calculated using the locally calculated frequency offset value and the master station's calculated frequency offset value, as shown in the following formula:

[0053] Δf carrier1 =(f1-f2) / 2

[0054] The carrier used for communication is f carrier The frequency of the local crystal oscillator is f, and the frequency deviation Δf of the local crystal oscillator is calculated by the following formula:

[0055] Δf=(Δf carrier1 / f carrier )* f

[0056] Step 4: The local crystal oscillator is a frequency-adjustable crystal oscillator. The calculated crystal oscillator frequency offset value is used to adjust the local crystal oscillator to complete the correction of the crystal oscillator frequency offset.

[0057] Step 5: Repeat steps 1-4 to achieve crystal oscillator frequency offset tracking and correction.

[0058] Accordingly, the master station of the communication system performs the following steps:

[0059] Step 1: Calculate the local frequency offset based on the received signal;

[0060] Step 2: Send the locally calculated frequency offset value to the peer station;

[0061] Step 3, repeat steps 1-2.

[0062] The master station only sends the calculated frequency offset and does not adjust the crystal oscillator on the master station itself.

[0063] A slave communication device, comprising:

[0064] The local frequency offset calculation module is used to calculate the local frequency offset based on the received signal.

[0065] The frequency offset transmission module is used to send the locally calculated frequency offset value to the peer station;

[0066] The crystal oscillator frequency offset calculation module is used to receive the frequency offset value sent by the master station and complete the calculation of the local crystal oscillator frequency offset based on the frequency offset value calculated locally and the frequency offset value calculated by the master station.

[0067] The crystal oscillator frequency adjustment module is used to adjust the local crystal oscillator according to the crystal oscillator frequency deviation value to complete the correction of the crystal oscillator frequency deviation.

[0068] A master station communication device, comprising:

[0069] The local frequency offset calculation module is used to calculate the local frequency offset based on the received signal.

[0070] The frequency offset transmission module is used to send the locally calculated frequency offset value to the peer station.

[0071] A communication system includes multiple slave communication devices and a master communication device.

[0072] Here are more specific examples:

[0073] A method for correcting the frequency offset of a crystal oscillator used for scattering dynamic channels, such as Figure 1 As shown, this method is applied to the slave station of the scattering mobile communication system, where the master and slave stations can communicate with each other in different locations, and each communication device can communicate normally.

[0074] It should be noted that the present invention does not limit the number of devices, device structure, application scenario, or device movement or stationary state in the communication system. The method is applicable to communication systems with one master station and multiple slave stations, one master station and one slave station, network communication, relay communication, mobile communication, and stationary communication.

[0075] See Figure 2 The steps of this method are as follows:

[0076] Step S201: Calculate the local frequency offset based on the received signal.

[0077] In one possible implementation, the received signal includes a frame header and a data portion. The frame header uses a fixed PN code, for example, the PN code length is 128 symbols. After receiving the frame header signal, the frame header signal is demodulated and then FFT processing is performed to obtain the frequency offset of the received signal. There are multiple frame headers within 1 second of the signal. The frequency offset values ​​calculated from multiple frame headers are averaged, and the local frequency offset value is taken as the average frequency offset over 1 second.

[0078] In one possible implementation, one or both of the communication endpoints are mobile, and the local frequency offset f1 includes the Doppler frequency shift f. Doppler1 and carrier frequency offset Δf carrier1 That is, f1 = f Doppler1 +Δf carrier1 Among them, f Doppler1 The Doppler frequency shift, Δf, is caused by the relative movement of the two ends during mobile communication. carrier1 The carrier frequency offset is caused by the inconsistency in the crystal oscillator frequencies of the two communication terminals.

[0079] Step S202: Send the locally calculated frequency offset value to the peer station.

[0080] In one possible implementation, the locally calculated frequency offset value is sent to the peer station via a signaling channel. For example, the locally calculated frequency offset value f1 is used as signaling information, encoded using 1 / 4 LDPC code, and the encoded data is then modulated using BPSK. The modulated signal is then sent to the peer station once every 1 second.

[0081] Step S203: Receive the frequency offset value sent by the master station, and complete the calculation of the local crystal oscillator frequency offset based on the locally calculated frequency offset value and the frequency offset value calculated by the master station.

[0082] In one possible implementation, signaling information including the master station's frequency offset value is received from the master station, and the information is demodulated to obtain the frequency offset value f2 sent by the master station. The frequency offset value f2 sent by the master station includes the master station's Doppler frequency shift f. Doppler2 and carrier frequency offset Δf carrier2 That is, f2 = f Doppler2 +Δf carrier2 The Doppler shift is caused by relative movement, and the effect is the same for both the slave and master stations, so f Doppler2 = f Doppler1 The carrier frequency offset is caused by the inconsistent frequency offsets of the crystal oscillators at both ends. The effects on the slave station and the master station are opposite, so Δf carrier2 = -Δf carrier1Based on the above relationship, the carrier frequency offset can be calculated using the locally calculated frequency offset value and the master station's calculated frequency offset value. The calculation formula is as follows:

[0083] Δf carrier1 =(f1-f2) / 2

[0084] The carrier used for communication is f carrier The frequency of the local crystal oscillator is f, and the frequency deviation Δf of the local crystal oscillator is calculated by the following formula:

[0085] Δf=(Δf carrier1 / f carrier )* f

[0086] Step S204: Adjust the local crystal oscillator according to the crystal oscillator frequency offset value to complete the correction of the crystal oscillator frequency offset.

[0087] In one possible implementation, the local crystal oscillator is a frequency-adjustable crystal oscillator. The local crystal oscillator receives frequency adjustment commands via serial port. After the crystal oscillator frequency offset value is calculated in the processor, the processor sends the frequency adjustment command to the crystal oscillator via serial port according to the protocol format of the crystal oscillator adjustment control command. The frequency offset adjustment amount can be adjusted once or multiple times according to the calculated crystal oscillator frequency offset value, and can be adjusted once every 1 second.

[0088] In one possible implementation, steps S201-S204 are repeated continuously. When the frequency of the crystal oscillator changes during long-term use of the device, the frequency deviation can be detected and adjusted in a timely manner, thus realizing the tracking and correction of the crystal oscillator frequency deviation during communication.

[0089] See Figure 3 The execution entity of this method is the master station in the communication system, and the specific steps are as follows:

[0090] Step S301: Calculate the local frequency offset based on the received signal.

[0091] In one possible implementation, the received signal includes a frame header and a data portion. The frame header uses a fixed PN code, for example, the PN code length is 128 symbols. After receiving the frame header signal, the frame header signal is demodulated and then FFT processing is performed to obtain the frequency offset of the received signal. There are multiple frame headers within 1 second of the signal. The frequency offset values ​​calculated from multiple frame headers are averaged, and the local frequency offset value is taken as the average frequency offset over 1 second.

[0092] In one possible implementation, one or both of the communication endpoints are mobile, and the local frequency offset f1 includes the Doppler frequency shift f. Doppler1 and carrier frequency offset Δf carrier1 That is, f1 = f Doppler1 +Δf carrier1 Among them, f Doppler1The Doppler frequency shift, Δf, is caused by the relative movement of the two ends during mobile communication. carrier1 The carrier frequency offset is caused by the inconsistency in the crystal oscillator frequencies of the two communication terminals.

[0093] Step S302: Send the locally calculated frequency offset value to the peer station.

[0094] In one possible implementation, the locally calculated frequency offset value is sent to the peer station via a signaling channel. For example, the locally calculated frequency offset f1 is used as signaling information and encoded using a 1 / 4 LDPC code. The encoded data is then modulated using BPSK, and the modulated signal is sent to the peer station once every 1 second. The frequency offset value sent by the master station is obtained by the slave station and used for calculating the frequency offset of the slave station's crystal oscillator.

[0095] In one possible implementation, the master station repeats steps S301-S302, enabling the slave station to repeatedly obtain the master station's frequency offset value, which is used by the slave station to detect changes in the crystal oscillator frequency offset during communication and adjust it in a timely manner.

[0096] like Figure 4 As shown, the communication device 4 is used as a slave station and includes: a local frequency offset calculation module 41, a frequency offset transmission module 42, a crystal oscillator frequency offset calculation module 43, and a crystal oscillator frequency adjustment module 44. Wherein:

[0097] The local frequency offset calculation module 41 is used to calculate the local frequency offset based on the received signal;

[0098] Frequency offset transmission module 42 is used to send the locally calculated frequency offset value to the peer station;

[0099] The crystal oscillator frequency offset calculation module 43 is used to receive the frequency offset value sent by the master station and complete the calculation of the local crystal oscillator frequency offset based on the frequency offset value calculated locally and the frequency offset value calculated by the master station.

[0100] The crystal frequency adjustment module 44 is used to adjust the local crystal oscillator according to the crystal frequency deviation value to complete the correction of the crystal frequency deviation.

[0101] like Figure 5 As shown, communication device 5 is used as a master station and includes: a local frequency offset calculation module 51 and a frequency offset transmission module 52. Wherein:

[0102] The local frequency offset calculation module 51 is used to calculate the local frequency offset based on the received signal;

[0103] The frequency offset transmission module 52 is used to send the locally calculated frequency offset value to the peer station.

[0104] The embodiments of the present invention also provide, as follows: Figure 1The communication system shown includes multiple communication devices, including a master station communication device and multiple slave station communication devices. The slave station executes steps S201-S204, and the master station executes steps S301-S302 to correct and track the deviation between the crystal oscillator frequency of the slave station and the crystal oscillator frequency of the master station.

[0105] Figure 6 This is a schematic diagram of a device terminal provided in an embodiment of the present invention. Figure 6 As shown, the terminal 6 in this embodiment includes a processor 60, a memory 61, and a computer program 62 stored in the memory 11 and executable on the processor 60. When the processor 60 executes the computer program 62, it implements the steps described in the embodiment of a crystal oscillator frequency offset correction method suitable for scattering dynamic channels, for example... Figure 2 Steps S201 to S204 shown are Figure 3 Steps S301 to S302 are shown. Alternatively, when processor 60 executes computer program 62, it implements the functions of each module / unit in the above-described device embodiments, for example... Figure 4 The functions of modules 41 to 44 shown are as follows: Figure 5 The functions of modules 51 to 52 are shown.

[0106] For example, computer program 62 can be divided into one or more modules / units, one or more of which are stored in memory 61 and executed by processor 60 to complete the present invention. One or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of computer program 62 in terminal 6. For example, computer program 62 can be divided into... Figure 4 Modules / units 41 to 44 shown and Figure 5 Modules / units 51 to 52 are shown.

[0107] Terminal 6 can be a computing device such as a desktop computer, laptop, handheld computer, or cloud server. Terminal 6 may include, but is not limited to, a processor 60 and a memory 61. Those skilled in the art will understand that... Figure 6 This is merely an example of terminal 6 and does not constitute a limitation on terminal 6. It may include more or fewer components than shown, or combine certain components, or different components. For example, the terminal may also include input / output devices, network access devices, buses, etc.

[0108] The processor 60 may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor.

[0109] The memory 61 can be an internal storage unit of the terminal 6, such as the hard disk or memory of the terminal 6. The memory 61 can also be an external storage device of the terminal 6, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the terminal 6. Furthermore, the memory 61 can include both internal storage units and external storage devices of the terminal 6. The memory 61 is used to store computer programs and other programs and data required by the terminal. The memory 61 can also be used to temporarily store data that has been output or will be output.

[0110] In summary, this invention can effectively separate crystal oscillator deviation from Doppler frequency shift under dynamic communication conditions, and realize the calculation, tracking and correction of crystal oscillator frequency deviation of each slave station in the system.

[0111] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for correcting frequency deviation of a crystal oscillator of a spread spectrum frequency hopping (SSFH) system, applied to a slave station of the SSFH system, characterized in that, Comprising the following steps: Step 1, calculating the local frequency offset according to the received signal; Step 2, sending the local frequency offset to the opposite end station; Step 3, receiving the frequency offset value sent by the master station, and calculating the local crystal oscillator frequency offset according to the local frequency offset and the frequency offset value sent by the master station; Step 4, adjusting the local crystal oscillator according to the local crystal oscillator frequency offset, and completing the correction of the crystal oscillator frequency offset; Step 5, repeating steps 1 to 4 to realize the tracking and correction of the crystal oscillator frequency offset.

2. The method for frequency deviation correction of a crystal oscillator for a spread Loran according to claim 1, wherein, In step 3, the calculation method of the local crystal oscillator frequency offset is: (1) Calculate carrier frequency offset Δf carrier1 : According to the above relationship, the local frequency offset value and the master station frequency offset value can be calculated, and the calculation formula is as follows: Δf carrier1 = (f1 - f2) / 2 Wherein, f1 is the local frequency offset, f2 is the frequency offset value sent by the master station; (2) calculating the local crystal oscillator frequency offset Δf: Δf = (Δf carrier1 / f carrier )* f where f carrier is the carrier frequency used for communication, and f is the frequency of the local crystal oscillator.

3. A communication device, characterized by The method of claim 1 or 2 is executed, comprising: The local frequency offset calculation module is used for calculating the local frequency offset according to the received signal; The frequency offset sending module is used for sending the local frequency offset to the opposite end station; The crystal oscillator frequency offset calculation module is used for receiving the frequency offset value sent by the master station, and calculating the local crystal oscillator frequency offset according to the local frequency offset and the frequency offset value sent by the master station; The crystal oscillator frequency adjustment module is used for adjusting the local crystal oscillator according to the local crystal oscillator frequency offset, and completing the correction of the crystal oscillator frequency offset.

4. A communication system, characterized by Comprising a plurality of slave stations and a master station, the slave station is the communication device of claim 3, and the master station comprises: The local frequency offset calculation module is used for calculating the local frequency offset according to the received signal; The frequency offset sending module is used for sending the local frequency offset to the opposite end station.

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