Synchronization module of communication and navigation integrated receiver, receiver and signal processing method

Abstract

The invention belongs to the field of communication and navigation, and relates to a synchronization module of a communication and navigation integrated receiver, the receiver and a signal processing method. The synchronization module has two signal paths: one is used for synchronizing a received signal for a communication service; the other loop is a navigation tracking loop which comprises a delay locking loop and a frequency locking loop and is used for estimating time delay for navigation service; the delay locked loop comprises a real-time branch, a lead branch and a delay branch. Mixing the received signal with a local carrier, and filtering to obtain an intermediate frequency signal; multiplying the intermediate frequency signal by a reference signal, and performing coherent integration to obtain an integration result; calculating autocorrelation function values of the three branches through an integral result; calculating time delay; calculating the time delay to obtain a time delay estimation value, and transmitting the time delay estimation value to a time synchronization module and a reference signal generation module; and obtaining a frequency offset estimation value according to an integration result, and transmitting the frequency offset estimation value to a frequency synchronization module and a carrier generation module. The problem that an existing synchronization module cannot be compatible with communication and navigation synchronization is solved.

Description

Technical Field

[0001] The invention belongs to the field of communication and navigation, and in particular relates to a synchronization module of a communication and navigation integrated receiver, a receiver and a signal processing method. Background Art

[0002] In today's era of rapid development of information technology, communication and navigation technology plays a vital role in many fields. Whether it is aerospace, transportation, military applications or daily communications, the demand for high-precision and high-reliability communication and navigation equipment is growing.

[0003] Traditional communication and navigation systems are usually designed and operated independently of each other, which not only leads to large equipment size and high cost, but also limits the overall performance and resource utilization of the system to a certain extent. For example, in some complex application scenarios, equipment with both accurate navigation and efficient communication capabilities is required, and independent systems are difficult to meet this comprehensive demand. With the continuous advancement of technology, the concept of Integrated Communication and Navigation (ICAN) came into being. It aims to organically integrate communication and navigation functions into one system, realize resource sharing and collaborative work, and thus improve the overall performance and efficiency of the system.

[0004] As a key component of the integrated communication and navigation system, the design of the synchronization module of the receiver is particularly important. The synchronization module is the core link to ensure that the receiver can accurately receive and process signals. It needs to quickly and accurately capture, track and synchronize signals in a complex electromagnetic environment to ensure the stability of communication and the accuracy of navigation. However, due to the differences in characteristics and modulation methods between communication and navigation signals, designing a synchronization module that can be compatible with both needs faces many challenges, such as signal interference suppression, synchronization accuracy improvement, and the balance between algorithm complexity and real-time performance. Summary of the invention

[0005] The object of the present invention is to provide a synchronization module of a communication and navigation integrated receiver, a receiver and a signal processing method, which solves the problem that the synchronization module in the existing receiver is not compatible with communication and navigation synchronization.

[0006] The present invention is achieved through the following technical solutions: The present invention discloses a synchronization module of a communication and navigation integrated receiver, wherein the synchronization module has two signal paths: one is used for synchronously receiving signals for communication services; the other is a navigation tracking loop, which is used to estimate the time offset and frequency offset of the received signal and estimate the time delay for the navigation service; The navigation tracking loop includes a delay locked loop as a code tracking loop and a frequency locked loop; The delay-locked loop consists of three branches: the immediate branch, the advance branch, and the delay branch; The signal path of the synchronous reception signal includes a time synchronization module and a frequency synchronization module; The three branches are all connected with a reference signal generating module and a carrier generating module.

[0007] Further, the output ends of the three branches are connected to a time delay discriminator, and the output end of the time delay discriminator is connected to a DLL filter; the output end of the instantaneous branch is connected to a FLL filter; The DLL filter connects the time synchronization module and the reference signal generation module; The FLL filter connects the frequency synchronization module and the carrier generation module.

[0008] The present invention also discloses a signal processing method of a synchronization module of a communication-conductance integrated receiver, comprising the following process: The received signal is mixed with a local carrier and then filtered to obtain an intermediate frequency signal; The intermediate frequency signal is multiplied by the locally copied reference signal, and then coherent integration is performed to obtain the integration results on the in-phase component and the orthogonal component; The autocorrelation function values ​​of the three branches are calculated through the integration results; The time delay is calculated based on the autocorrelation function value; The time delay is filtered and calculated to obtain a time delay estimation value; the time delay estimation value is transmitted to the time synchronization module and the reference signal generation module; At the same time, a frequency offset value is calculated based on the integration result, and a frequency offset estimation value is obtained after filtering the frequency offset value. The frequency offset estimation value is passed to the frequency synchronization module and the carrier generation module.

[0009] Furthermore, the received signal is mixed with a local carrier and then filtered to obtain an intermediate frequency signal, which is expressed as:

[0010] in, t Indicates time, represents the real part of the complex number, j represents the imaginary unit, is the frequency of the local carrier, and They represent the in-phase component and quadrature component of the intermediate frequency signal respectively.

[0011] Furthermore, the integration results on the in-phase component and the orthogonal component are specifically expressed as follows:

[0012] in, represents the time delay between the received signal and the local copy, represents the autocorrelation function of the reference signal on the in-phase component and the orthogonal component, Indicates the frequency offset between the received signal and the local carrier. Indicates the phase offset between the received signal and the local carrier. is the integration period, represents the sinc function, represents the integration result on the in-phase component; Represents the result of integration over the orthogonal components.

[0013] Furthermore, the reference signal time offset corresponding to the instantaneous branch is , the reference signal time offset ratio corresponding to the leading branch The time offset of the reference signal corresponding to the delay branch is smaller than that of the correlator spacing. 1 correlator spacing larger; The autocorrelation function values ​​of the three branches are calculated by integrating the results, that is, the autocorrelation function values ​​of the instant branches The expression is:

[0014] Similarly, the autocorrelation function value of the leading branch is obtained The autocorrelation function value of the delay branch ; The time delay is calculated based on the autocorrelation function value, and the expression is: .

[0015] Further, the time delay is filtered and calculated to obtain the time delay estimation value, and the specific process is: First get the time delay after filtering , calculated using the following formula:

[0016] in, and are the time delay of filtering and the time delay of measurement in the previous integration period, respectively; Indicates the natural frequency that determines the output accuracy and dynamic response performance; Finally, after filtering, the delay and the delay estimate in the previous integration cycle Calculate the time delay estimate : ; in, is the integration period.

[0017] further, According to the noise bandwidth of the DLL The calculation results in: .

[0018] Further, the frequency offset value is obtained by measuring according to the integration result, and the specific process is as follows: First calculate the integral value from the integral results on the in-phase component and the orthogonal component :

[0019] By multiplying the integral value in the previous integration period and the integral value corresponding to the current integration period, the phase change in the adjacent integration period is obtained, and the expression is:

[0020] in, express The complex conjugate of represents the modulus of a complex number, Indicates the integration period Phase changes in The frequency offset value is calculated based on this phase change :

[0021] Among them, the range of frequency measurement is , is the integration period; The frequency offset value is filtered to obtain the frequency offset estimate .

[0022] The invention also discloses a communication and navigation integrated receiver containing the synchronization module.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention proposes a synchronization module for a communication and navigation integrated receiver, which integrates a navigation tracking loop and a communication synchronization function, has a time synchronization module, and is combined with a delay locked loop (DLL). By utilizing its three branches of immediate, advance, and delay, it is able to precisely identify the signal time delay, and accurately correct the time error through the DLL filter, so that the receiver can accurately locate the time point of receiving the signal, which is extremely critical for the subsequent accurate demodulation of data and positioning calculation.

[0024] The frequency locked loop (FLL) works with the frequency synchronization module to accurately estimate and compensate for the frequency offset of the received signal. Accurate frequency synchronization can avoid distortion and bit errors caused by frequency deviation during signal demodulation, ensuring the reliability of the communication link and the accuracy of data transmission.

[0025] Two different signal paths are set up, one for basic synchronization reception and the other for navigation tracking, with clear division of labor. This architecture enables targeted optimization and debugging of the synchronization process and navigation tracking parameter estimation in complex and changing signal environments, enhancing the system's ability to adapt to different working conditions.

[0026] The delay-locked loop and frequency-locked loop work together to continuously track and adjust the signal when it changes dynamically, whether it is the Doppler frequency shift of the signal or the fluctuation of the transmission delay, to maintain stable and reliable lock on the signal, reduce the probability of signal loss of lock, and ensure the continuity of communication and navigation functions.

[0027] The connections between each module are clear. If a module fails, it can be quickly located and repaired by replacing the corresponding module, reducing maintenance costs and difficulty, and is also conducive to subsequent system upgrades and function expansions.

[0028] The present invention proposes an ICAN receiver that integrates a navigation tracking loop and a communication synchronization module, wherein the synchronization module can be used for both synchronization of communication signals and estimation of time delay of navigation services. Compared with communication and navigation receivers that work separately, the ICAN receiver can improve the efficiency of signal processing and reduce costs and power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the schematic diagram of the synchronization module of the ICAN receiver; Figure 2 For the application of synchronization module in OFDM system; Figure 3 This is the curve of BER changing with satellite transmission power; Figure 4 is the curve of the estimated error of time delay changing with time; Figure 5 This is the variation law of ranging accuracy with the transmission power of LEO satellite. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0031] The detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the invention claimed for protection, but merely represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0032] The features and performances of the present invention are further described in detail below in conjunction with the embodiments.

[0033] The present invention proposes an ICAN receiver that integrates a navigation tracking loop and a communication synchronization module, wherein the synchronization module can be used for both synchronization of communication signals and estimation of time delay of navigation services. Compared with communication and navigation receivers that work separately, the ICAN receiver can improve the efficiency of signal processing and reduce costs and power consumption.

[0034] First, the working principle of the ICAN receiver synchronization module proposed in the present invention is introduced in detail. Then, the transmitter and receiver processing flow of the integrated communication and guidance signal are explained by taking the Orthogonal Frequency Division Multiplexing (OFDM) system as an example, in which the signal synchronization module utilizes the method proposed in the present invention. Finally, the performance of the ICAN receiver synchronization module proposed in the present invention is compared with that of the traditional receiver synchronization module to illustrate the advantages of the method.

[0035] The synchronization module of the integrated communication and navigation receiver designed by the present invention has two functions: (1) synchronous reception of signals for communication services; (2) estimation of time delay for navigation services. Generally, integrated communication and navigation signals contain reference signals, which can be reproduced in the receiver and used to achieve synchronization of integrated communication and navigation signals.

[0036] Figure 1 The schematic diagram of the synchronization module of the ICAN receiver is shown. The module has two signal paths: one for synchronizing the received signal ; The other is a navigation tracking loop, which is used to estimate The navigation tracking loop includes a delay lock loop (DLL) as a code tracking loop and a frequency lock loop (FLL). The DLL contains three branches: the immediate branch, the advance branch, and the delay branch.

[0037] The signal output by the instantaneous branch is the square of the autocorrelation function value. , the signal output by the leading branch is the square of the autocorrelation function value The signal output by the delay branch is the square of the autocorrelation function value .

[0038] The three branches are connected with a reference signal generating module and a carrier generating module, the output ends of the three branches are connected with a time delay discriminator, the output end of the time delay discriminator is connected with a DLL filter; the output end of the instantaneous branch is connected with an FLL filter; The signal path of the synchronous reception signal includes a time synchronization module and a frequency synchronization module.

[0039] The DLL filter connects the time synchronization module and the reference signal generation module.

[0040] The FLL filter connects the frequency synchronization module and the carrier generation module.

[0041] The following is a detailed introduction to the processing of the delay locked loop DLL.

[0042] In order to better understand the principle of the delay locked loop, the instantaneous branch is used as an example. Figure 1 As shown, first, the receiving signal Mix with local carrier and then filter to get IF signal : (1) in, t Indicates time, represents the real part of the complex number, j represents the imaginary unit, is the frequency of the local carrier, and They represent the in-phase (I) component and quadrature (Q) component of the intermediate frequency signal respectively.

[0043] Then, the IF signal Multiplied with the locally copied reference signal, the product is sent to the integration and removal filter (I&D) for coherent integration. The integration results on the in-phase component and the orthogonal component are: (2) in, represents the time delay between the received signal and the local copy, represents the autocorrelation function of the reference signal on the in-phase component and the orthogonal component, Indicates the frequency offset between the received signal and the local carrier. Indicates the phase offset between the received signal and the local carrier. is the integration period, represents the sinc function, represents the integration result on the in-phase component; Represents the result of integration over the orthogonal components.

[0044] To avoid phase shift The autocorrelation function value is calculated by the coherent integration result. : (3) Similarly, the autocorrelation function value of the leading branch can be generated The autocorrelation function value of the delay branch The difference between the three branches lies in the time offset of the locally copied reference signal. The time offset of the reference signal corresponding to the branch is , and the reference signal time offset of the leading branch is The time offset of the reference signal corresponding to the delay branch is smaller than that of the correlator spacing. The correlator spacing is larger by 1, so the local reference signal generated is different, and the reference signal must be multiplied by the intermediate frequency signal and then coherently integrated, so the autocorrelation function value obtained is different.

[0045] The non-coherent Early-minus-Late Power (NELP) method is used as the time delay identification method. The calculation formula of the time delay discriminator is: (4) Then, the time delay is calculated It is sent to the DLL filter to reduce the influence of noise. Because the time delay of the received signal changes linearly with time, the present invention uses a second-order DLL loop to accurately track the time delay. The present invention uses a first-order DLL filter, and the time delay after the DLL filter is filtered It is calculated as follows: (5) in, and are the time delay of filtering and the time delay of measurement in the previous integration period, respectively. It is a parameter of the DLL filter, indicating the natural frequency that determines the output accuracy and dynamic response performance. It can be calculated based on the noise bandwidth of the DLL. The calculation results in: (6) Finally, after filtering, the delay and the delay estimate in the previous integration cycle Calculates an estimate of the time delay during the current integration period : (7) Then, the time delay estimate It is passed to the time synchronization module and the reference signal generation module to mitigate the time offset of the received signal.

[0046] also, It can also be used to calculate the pseudorange for navigation services. It is worth noting that the proposed synchronization method estimates the time delay of communication and navigation services simultaneously. Compared with separate processing of communication and navigation, this ICAN receiver eliminates the need for a carrier tracking loop in navigation and a traditional synchronization module in communication, reducing cost and power consumption.

[0047] The processing of the frequency locked loop FLL is introduced in detail below.

[0048] Due to the influence of Doppler frequency and low stability oscillator, there is a frequency offset between the received signal and the local replica signal in the receiver. The frequency locked loop FLL tracks the frequency of the intermediate frequency signal based on the adjacent integrated values ​​in the instantaneous branch. The integrated value is obtained by integrating the I and Q components: (8) Similarly, Represents the integral value in the previous integration period. By multiplying these two integral values, the phase change in the adjacent integration period can be obtained, and the expression is: (9) in, express The complex conjugate of represents the modulus of a complex number, Indicates the integration period Therefore, the frequency offset value can be calculated based on this phase change : (10) The frequency measurement range is .

[0049] Similar to the DLL process, the calculated frequency offset value After passing through the FLL filter, the frequency offset estimate is obtained ,Then is passed to the frequency synchronization and carrier generation module.

[0050] The following is a detailed introduction to the application of the synchronization module in the OFDM system.

[0051] OFDM technology has the advantages of high spectrum utilization and strong resistance to multipath fading, and is widely used in mobile communications, digital video broadcasting, and downlink signals of Starlink low-orbit constellations. Under the OFDM technology framework, a special reference signal structure is designed so that it can be used for channel estimation in communications and for capturing and tracking navigation signals.

[0052] Figure 2 The signal processing flow of the OFDM system is shown. The transmitter modulates the input bit stream and converts the serial data into parallel data. , and then use the inverse fast Fourier transform (IFFT) to transform these parallel data Modulation is performed and the resulting data is then converted back into a serial time domain signal At the same time, reference data Used to modulate the reference signal . Further with signal The composite signal is obtained by adding and a cyclic prefix (CP) is added in front of it. Finally, the signal is sent to the receiver through the wireless channel.

[0053] In the receiver, the synchronization module uses the reference signal Estimated propagation time delay Provided to navigation service, while adjusting sampling timing and carrier frequency deviation to obtain synchronization signal. After that, remove the cyclic prefix (CP) from the synchronization signal, and obtain parallel data after the serial-to-parallel conversion processing through fast Fourier transform (FFT) and channel estimation and equalization. Finally, the balanced data The received bit stream is obtained after parallel-to-serial conversion and demodulation to provide communication services.

[0054] Performance Analysis In order to illustrate the superiority of the communication and navigation integrated receiver synchronization module implementation method proposed in the present invention, the performance of the method is compared with that of the traditional method in terms of communication and navigation.

[0055] The simulation experiment is aimed at the OFDM type integrated communication and navigation signals broadcast by low-orbit satellites. The synchronization method of the integrated communication and navigation receiver synchronization module proposed by the present invention (called OFDM DLL) and the traditional method (called OFDM SYNC) are used to compare their communication performance and navigation performance. OFDM SYNC is established based on OFDM signals, and its synchronization is achieved through a two-dimensional search of time delay and frequency offset. In contrast, OFDM DLL uses a delay locked loop for synchronization.

[0056] The simulation parameters are shown in Table 1. The OFDM signal parameters directly adopt the typical 5G NR configuration.

[0057] Table 1 Key simulation parameters of OFDM system

[0058] (1) Communication performance The bit error rate (BER) is used to evaluate the communication performance of different schemes, and the results are plotted on Figure 3 In. From Figure 3 It can be concluded that the BER curve of OFDM DLL is below the BER curve of OFDM SYNC. In particular, when the transmit power is 60 dBm, the BER of OFDM DLL is reduced by 0.17% compared with OFDM SYNC.

[0059] 2. Navigation performance Estimation error of time delay Used to characterize navigation performance, it can be based on the estimated time delay and the actual time delay Derived from this: (11) Figure 4 By comparing the estimation errors of the two schemes over time, it can be found that the error of the time delay estimation value of the two-dimensional search presents a periodic sawtooth wave. Because the minimum resolution of the two-dimensional search is limited to one sampling interval, but the time delay changes linearly with time, the navigation accuracy is low. The estimation error of the proposed scheme (OFDM DLL) is significantly lower than that of OFDM SYNC because the delay locked loop provides a high-precision time delay estimate.

[0060] In addition, using the estimated error The standard deviation (STD) is used to characterize the navigation performance of the proposed OFDM DLL, as shown in Figure 5 As shown, the ranging accuracy increases with the increase of LEO satellite transmission power.

[0061] In summary, the comparison results show that the proposed ICAN receiver synchronization scheme improves the communication performance and navigation performance, and the delay locked loop DLL is essential to provide high-precision navigation tracking.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A synchronization module for a communication and guidance integrated receiver, characterized in that: The synchronization module has two signal paths: one for synchronizing received signals for communication services; the other is a navigation tracking loop for estimating the time offset and frequency offset of received signals and estimating the time delay for navigation services; The navigation tracking loop includes a delay locked loop as a code tracking loop and a frequency locked loop; The delay-locked loop consists of three branches: the immediate branch, the advance branch, and the delay branch; The signal path of the synchronous reception signal includes a time synchronization module and a frequency synchronization module; The three branches are all connected with a reference signal generating module and a carrier generating module.

2. The synchronization module of the integrated communication and guidance receiver according to claim 1, characterized in that: The output ends of the three branches are connected to a time delay discriminator, and the output end of the time delay discriminator is connected to a DLL filter; the output end of the instantaneous branch is connected to a FLL filter; The DLL filter connects the time synchronization module and the reference signal generation module; The FLL filter connects the frequency synchronization module and the carrier generation module.

3. A signal processing method for a synchronization module of a communication and guidance integrated receiver according to claim 1 or 2, characterized in that: The process includes: The received signal is mixed with a local carrier and then filtered to obtain an intermediate frequency signal; The intermediate frequency signal is multiplied by the locally copied reference signal, and then coherently integrated to obtain the integration results on the in-phase component and the orthogonal component; The autocorrelation function values ​​of the three branches are calculated through the integration results; The time delay is calculated based on the autocorrelation function value; The time delay is filtered and calculated to obtain a time delay estimation value; the time delay estimation value is transmitted to the time synchronization module and the reference signal generation module; At the same time, a frequency offset value is calculated based on the integration result, and a frequency offset estimation value is obtained after filtering the frequency offset value. The frequency offset estimation value is transmitted to the frequency synchronization module and the carrier generation module.

4. The signal processing method according to claim 3, characterized in that: The received signal is mixed with the local carrier and then filtered to obtain the intermediate frequency signal, which is expressed as: in, t Indicates time, represents the real part of the complex number, j represents the imaginary unit, is the frequency of the local carrier, and They represent the in-phase component and quadrature component of the intermediate frequency signal respectively.

5. The signal processing method according to claim 3, characterized in that: The integration result on the in-phase component and the orthogonal component is expressed as follows: in, represents the time delay between the received signal and the local copy, represents the autocorrelation function of the reference signal on the in-phase component and the orthogonal component, Indicates the frequency offset between the received signal and the local carrier. Indicates the phase offset between the received signal and the local carrier. is the integration period, represents the sinc function, represents the integration result on the in-phase component; Represents the result of integration over the orthogonal components.

6. The signal processing method according to claim 5, characterized in that: The reference signal time offset corresponding to the instantaneous branch is , the reference signal time offset ratio corresponding to the leading branch The time offset of the reference signal corresponding to the delay branch is smaller than that of the correlator spacing. 1 correlator spacing larger; The autocorrelation function values ​​of the three branches are calculated by integrating the results, that is, the autocorrelation function values ​​of the instant branches The expression is: Similarly, the autocorrelation function value of the leading branch is obtained The autocorrelation function value of the delay branch ; The time delay is calculated based on the autocorrelation function value, and the expression is: 。 7. The signal processing method according to claim 3, characterized in that: The time delay is filtered and calculated to obtain the time delay estimation value, and the specific process is: First get the time delay after filtering , calculated according to the following formula: in, and are the time delay of filtering and the time delay of measurement in the previous integration period, respectively; Indicates the natural frequency that determines the output accuracy and dynamic response performance; Finally, after filtering, the delay and the delay estimate in the previous integration cycle Calculate the time delay estimate : ； in, is the integration period.

8. The signal processing method according to claim 7, characterized in that: According to the noise bandwidth of the DLL The calculations show that: 。 9. The signal processing method according to claim 5, characterized in that: The frequency offset value is obtained by measuring the integration result, and the specific process is as follows: First calculate the integral value from the integral results on the in-phase component and the orthogonal component : By multiplying the integral value in the previous integration period and the integral value corresponding to the current integration period, the phase change in the adjacent integration period is obtained, and the expression is: in, express The complex conjugate of represents the modulus of a complex number, Indicates the integration period Phase changes in The frequency offset value is calculated based on this phase change : Among them, the range of frequency measurement is , is the integration period; The frequency offset value is filtered to obtain the frequency offset estimate .

10. A communication and navigation integrated receiver comprising the synchronization module according to claim 1 or 2.

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