A Spread Spectrum Signal Tracking System Supporting Mixed Symbol Rates

Abstract

The embodiment of the present invention provides a spread spectrum signal tracking system supporting mixed symbol rates, and relates to the field of spread spectrum communications. It includes: a first-stage coherent integrator, a second-stage coherent integrator, an Nth-stage coherent integrator, an incoherent integrator, a random access memory, a frame synchronization unit, and a tracking loop. It adopts a hierarchical integrator and a multi-stage symbol demodulation cascade to achieve the configuration capability of short, medium, long and other integration durations, and each stage supports independent symbol demodulation. It supports the demodulation of spread spectrum signals modulated with different symbol rates at the same time, and has higher robustness when the symbol rate is dynamically switched. It achieves the technical effect of being able to flexibly demodulate spread spectrum signals with multiple symbol rates.

Description

Technical Field

[0001] The present application relates to the field of spread spectrum communication, and in particular to a spread spectrum signal tracking system supporting mixed symbol rates. Background Art

[0002] Spread spectrum signal systems are widely used in Beidou navigation GNSS systems, RDSS short message systems, and satellite communication systems. Spread spectrum signals reduce the requirements for symbol Eb / No during channel transmission by increasing signal bandwidth, so that the signal can be buried under noise, thereby improving the concealment and anti-interference performance of communications.

[0003] When extracting information symbols from spread spectrum signals at the receiving end, the prior art requires despreading first by means of coherent integration. Coherent integration can greatly reduce the noise bandwidth, thereby recovering the signal from the noise. Therefore, the longer the coherent integration time, the higher the signal-to-noise ratio of the recovered signal. However, the coherent integration time is at least affected by the symbol rate and the signal Doppler frequency deviation. If the symbol is not stripped, cross-symbol integration is not possible. Considering that in modern Beidou RDSS and satellite communications systems that use the CDMA spread spectrum system, the symbol rate transmitted by a channel is not just one. For example, in the Beidou RDSS system, the symbol rates of the public segment and the dedicated segment are 16Kbps and 32Kbps respectively, and the pilot is 1kbps. In most satellite communication systems, the symbol rate can be configured within a wide range to adapt to different good or bad channel environments.

[0004] Therefore, how to flexibly demodulate spread spectrum signals with multiple symbol rates has become a technical problem that needs to be solved urgently. Summary of the invention

[0005] In order to achieve the ability to flexibly demodulate spread spectrum signals with multiple symbol rates, the present application provides a spread spectrum signal tracking system that supports mixed symbol rates.

[0006] In the first aspect, a spread spectrum signal tracking method provided by the present application adopts the following technical solution:

[0007] A spread spectrum signal tracking system supporting mixed symbol rates, comprising: a first-stage coherent integrator, a second-stage coherent integrator, an Nth-stage coherent integrator, a non-coherent integrator, a random access memory, a frame synchronization unit and a tracking loop;

[0008] The first-stage coherent integrator is used to perform coherent integration after receiving the spread spectrum signal to generate a first-stage integration result and a first-stage symbol soft demodulation result corresponding to the first-stage integration result, and store the first-stage integration result in the random access memory;

[0009] The second-stage coherent integrator is used to perform coherent integration on the first-stage integration result to generate a second-stage integration result and a second-stage symbol soft demodulation result corresponding to the second-stage integration result, and store the second-stage integration result in the random access memory;

[0010] The N-th level coherent integrator is used to perform coherent integration on the N-1-th level integration result generated by the N-1-th level coherent integrator to generate an N-th level integration result and an N-th level symbol soft demodulation result corresponding to the N-th level integration result, and store the N-th level integration result in the random access memory;

[0011] The non-coherent integrator is used to obtain corresponding integration results from all coherent integrators and perform non-coherent integration;

[0012] The frame synchronization unit is used to obtain all symbol soft demodulation results from all coherent integrators to determine symbol soft information, and perform a search based on the symbol soft information to obtain a search result;

[0013] The tracking loop is used to obtain integration results from all the coherent integrators and the incoherent integrators, and perform filtering processing according to the integration results.

[0014] Optionally, symbol rate information in a current use environment is acquired, and specific information of the Nth stage coherent integrator is determined according to the symbol rate information, where N is a positive integer.

[0015] Optionally, the first-stage coherent integrator is also used to perform symbol soft demodulation on the first-stage integration result based on symbol soft demodulation 1 and store the generated first-stage symbol soft information in the random access memory.

[0016] Optionally, the second-stage coherent integrator is further used to perform symbol soft demodulation on the second-stage integration result based on symbol soft demodulation 2 and store the generated second-stage symbol soft information in the random access memory.

[0017] Optionally, the Nth stage coherent integrator is also used to perform symbol soft demodulation on the Nth stage integration result based on symbol soft demodulation N and store the generated Nth stage symbol soft information in the random access memory.

[0018] Optionally, the symbol soft demodulation result is generated according to the first-level symbol soft information, the second-level symbol soft information and the N-th-level symbol soft information.

[0019] In summary, the present application includes the following beneficial technical effects:

[0020] The present application includes a first-stage coherent integrator, a second-stage coherent integrator, an Nth-stage coherent integrator, an incoherent integrator, a random access memory, a frame synchronization unit, and a tracking loop. It adopts a hierarchical integrator and a multi-stage symbol demodulation cascade to realize the configuration capability of short, medium, long, and other integration durations, and each stage supports independent symbol demodulation. It supports the demodulation of spread spectrum signals modulated with different symbol rates at the same time, and has higher robustness when the symbol rate is dynamically switched. It realizes the technical effect of being able to flexibly demodulate spread spectrum signals with multiple symbol rates. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural block diagram of the first embodiment of the spread spectrum signal tracking system supporting mixed symbol rates of the present application;

[0022] Figure 2 It is a schematic diagram of specific implementation steps in a certain type of Beidou RDSS receiver of the first embodiment of the spread spectrum signal tracking system supporting mixed symbol rates of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below through the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0024] Reference Figure 1 , Figure 1 This is a structural block diagram of the first embodiment of the spread spectrum signal tracking system supporting mixed symbol rates of the present application.

[0025] like Figure 1 As shown, the spread spectrum signal tracking system supporting mixed symbol rate proposed in the embodiment of the present application includes: a first-stage coherent integrator 10, a second-stage coherent integrator 20, an N-th-stage coherent integrator 30, a non-coherent integrator 40, a random access memory 50, a frame synchronization unit 60 and a tracking loop 70:

[0026] The first-stage coherent integrator 10 is used to perform coherent integration after receiving the spread spectrum signal to generate a first-stage integration result and a first-stage symbol soft demodulation result corresponding to the first-stage integration result, and store the first-stage integration result in a random access memory 50;

[0027] The second-stage coherent integrator 20 is used to perform coherent integration on the first-stage integration result to generate a second-stage integration result and a second-stage symbol soft demodulation result corresponding to the second-stage integration result, and store the second-stage integration result in the random access memory 50;

[0028] The N-th level coherent integrator 30 is used to perform coherent integration on the N-1-th level integration result generated by the N-1-th level coherent integrator to generate the N-th level integration result and the N-th level symbol soft demodulation result corresponding to the N-th level integration result, and store the N-th level integration result in the random access memory 50;

[0029] A non-coherent integrator 40, used to obtain corresponding integration results from all coherent integrators and perform non-coherent integration;

[0030] Frame synchronization unit: 60, used to obtain all symbol soft demodulation results from all coherent integrators to determine symbol soft information, and search according to the symbol soft information to obtain search results;

[0031] The tracking loop 70 is used to obtain integration results from all coherent integrators and non-coherent integrators, and perform filtering processing according to the integration results.

[0032] It should be noted that the present embodiment provides a spread spectrum signal tracking system supporting mixed symbol rates, including a spread spectrum signal tracking architecture and a receiver supporting mixed symbol rates. In view of the problem that a tracking engine in the existing traditional baseband design can only configure and support one symbol rate, and multiple symbol rates require deep software involvement and high complexity, the present embodiment adopts a hierarchical integrator and a multi-level symbol demodulation cascade, and the integration time lengths such as short time, medium time, and long time are configurable, and each level supports independent symbol demodulation and even independent carrier loops to support the demodulation of spread spectrum signals modulated with different symbol rates at the same time, and has higher robustness when the symbol rate is dynamically switched.

[0033] In the specific implementation, Figure 1 The schematic diagram of the working principle of the spread spectrum signal tracking system supporting mixed symbol rates is shown, 10 is the first-stage coherent integrator, 20 is the second-stage coherent integrator, 30 is the Nth-stage coherent integrator, 40 is the incoherent integrator, 60 is the frame synchronization unit, and 70 is the tracking loop.

[0034] It should be noted that 10 performs the first level coherent integration on the spread spectrum signal. Symbol soft demodulation 1 performs symbol soft demodulation based on the first level integration result, and continuously stores symbol soft information in RAM;

[0035] 20 Based on the first-stage integration, the spread spectrum signal is subjected to a second-stage coherent integration. Symbol soft demodulation 2, based on the second-stage integration result, symbol soft demodulation is performed, and symbol soft information is continuously stored in RAM;

[0036] 30 Performing N-th level coherent integration on the spread spectrum signal. Symbol soft demodulation N, performing symbol soft demodulation based on the N-th level integration result, and continuously storing symbol soft information in RAM; where N is a positive integer, and N is determined by the type of symbol rate in the current target spread spectrum system;

[0037] 40 is defined as configurable, supporting obtaining integration results from the first, second, and Nth level coherent integrators and performing incoherent integration;

[0038] 60 definitions are configurable, supporting the extraction of symbol soft information from symbol soft demodulation 1, symbol soft demodulation 2, to symbol soft demodulation N, and frame synchronization search; the frame synchronization result can be synchronously fed back to the symbol soft demodulation units at all levels;

[0039] 70 is defined as configurable, and supports obtaining integration results from the first, second, to Nth level coherent integrators, and non-coherent integrators, and performing tracking loop filtering processing on the spread spectrum signal.

[0040] In a specific implementation, the specific implementation steps of applying this embodiment to a certain type of Beidou RDSS receiver are as follows: Figure 2 As shown:

[0041] Step 1: The first-stage coherent integrator performs 1 / 32 ms coherent integration on the spread spectrum signal. Symbol soft demodulation 1: soft demodulation is performed at a symbol rate of 32 kbps, and symbol soft information is continuously stored in RAM;

[0042] Step 2: The second-stage coherent integrator accumulates the 1 / 32ms result obtained by the first-stage integration twice to obtain a 1 / 16ms integration result. Symbol soft demodulation 2: soft demodulation is performed at a symbol rate of 16kbps, and symbol soft information is continuously stored in RAM;

[0043] Step 3, the third-stage coherent integrator accumulates the 1 / 16ms result obtained by the second-stage integration 16 times to obtain a 1ms integration result. Symbol soft demodulation 3, soft demodulation is performed at a symbol rate of 1 kbps, and symbol soft information is continuously stored in RAM;

[0044] Step 4, the non-coherent integrator is configured to obtain the integration result from the third-stage coherent integrator, perform non-coherent integration, and perform non-coherent integration four times to obtain a non-coherent integration result once every 4 ms;

[0045] Step 5, the frame synchronization unit is configured to extract 1kbps symbol soft information from symbol soft demodulation 3 and perform frame synchronization search; according to the frame synchronization result, the starting position of the symbol is obtained, and then according to the protocol format of the information frame, the relative position of the 32k symbol and the 16k symbol is obtained, and fed back to symbol soft demodulation 1 and symbol soft demodulation 2;

[0046] Step 6, the tracking loop configuration obtains the integration results from the second and third stage coherent integrators, as well as the incoherent integrators, and performs tracking loop filtering processing on the spread spectrum signal; this example uses a carrier loop that combines 1ms and 1 / 32ms, as well as a typical carrier-assisted code loop.

[0047] It should be noted that in step 1, the integration time of the first-stage coherent integrator is designed to be 1 / 32 ms, considering that the maximum symbol rate of the target coherent spread spectrum signal of the receiver instance is 32kbps. The integration time of the first-stage integrator can also be designed to be 1 / 2 of the period corresponding to the maximum symbol rate of the target spread spectrum signal, so as to support the scenario where the spread spectrum code and the information symbol are incoherent. At present, for the scenario where the maximum symbol rate period of the target spread spectrum signal is relatively large, the integration time of the first-stage coherent integrator can be designed to be smaller, such as 0.125ms or 0.5ms, etc., to support the receiver to keep tracking a larger Doppler change rate. And in step 1, symbol soft demodulation 1, the 32khz integration result output by the first-stage integrator is soft-demodulated, and the symbol soft information is continuously stored in RAM. The starting position and length of the storage can be cleared and adjusted according to the frame format after the frame synchronization is completed, so as to realize the demodulation and storage of the soft information of the 32khz symbol in a specific period of time in the frame;

[0048] In step 2, the second-stage coherent integrator performs two coherent accumulations on the 1 / 32 ms result of the input first-stage coherent integrator to obtain a 1 / 16 ms coherent integration result. In the specific implementation process, the number of accumulations of the first-stage integration result by the second-stage coherent integrator is configurable. In this example receiver, it is designed to be adjustable from 1 to 32 times, that is, the second-stage coherent integrator supports coherent integration from 1 / 32 ms to 1 ms;

[0049] In step 3, the third-stage coherent integrator performs 16 coherent accumulations on the 1 / 16 ms result of the input second-stage coherent integrator to obtain a 1 ms coherent integration result. In the specific implementation process, the number of accumulations of the second-stage integration result by the third-stage coherent integrator is configurable. In this example receiver, it is designed to be adjustable from 1 to 128 times, that is, the second-stage coherent integrator supports coherent integration from 1 / 32 ms to 128 ms.

[0050] In step 4, the non-coherent integrator supports obtaining the coherent integration result from any one of the first, second or third stages, and the number of non-coherent integrations is configurable. The receiver in this example is configured to obtain the integration result from the third-stage coherent integrator, and the number of non-coherent integrations of the non-coherent integrator is configured to 4 times, so as to obtain the non-coherent integration result once every 4ms; in the specific implementation process, it is preferred to design one or more non-coherent integrators according to the requirements of the code loop or carrier loop for the non-coherent integration result, and support obtaining the integration result from multiple coherent integrators to achieve flexible loop design;

[0051] In step 5, the frame synchronization unit is configured to extract 1kbps symbol soft information from the symbol soft demodulation 3 to perform frame synchronization search. In the specific implementation process, the symbol soft information for the receiver frame synchronization can be preferentially implemented according to the format of the frame header, the length of the frame header, the relevant characteristics of the frame header, etc. under different symbol rates (for example, in the application scenario, which symbol rate has the highest autocorrelation gain of the frame header, which is most conducive to the frame header synchronization search). In the receiver of this example, a 1kbps symbol stream with a low symbol rate and a high coherence gain is used for frame synchronization. And according to the frame synchronization result, the starting position of the symbol is obtained, and then according to the protocol format of the information frame, the relative position of the 32k symbol and the 16k symbol is obtained, and fed back to the symbol soft demodulation 1 and the symbol soft demodulation 2.

[0052] For scenarios where the spread spectrum code and information symbols are coherent, after the receiver captures the code phase of the spread spectrum code, it already knows the integration start edge of the symbol, and only needs to perform frame synchronization to obtain the starting edge of the frame, so as to perform symbol reception and demodulation and decoding of each symbol segment according to the frame format of the communication protocol. For non-coherent spread spectrum signals, or scenarios where there are subcodes, secondary codes, etc. in the symbol that require bit synchronization, it is only necessary to add a first-level coherent integrator, whose integration time is half of the secondary code period, and then perform a bit synchronization search on the integration result of this level to find the starting position of the symbol required for frame synchronization; then perform a frame synchronization search in the symbol soft demodulation information output by the next level of coherent integrator; it can be seen that the spread spectrum signal tracking architecture of the present invention is flexible under different signal tracking, as well as synchronization requirements of symbols, secondary codes, etc.

[0053] In step 6, the tracking loop supports obtaining the integration results from the first, second, third and other coherent and incoherent integrators to perform loop filtering calculations. The receiver of this example is configured to obtain the integration results from the second and third coherent integrators, as well as the incoherent integrators, to perform tracking loop filtering processing of the spread spectrum signal; in this example, a carrier loop with 1 ms and 1 / 32 ms is used, as well as a typical carrier-assisted code loop. In the specific implementation process, since the tracking architecture of the present invention can simultaneously output a variety of long and short-time coherent and incoherent integration results, it can more easily and flexibly support complex tracking loops, such as short-time PLL phase-locked loop + short-time DLL, long-time phase detection + Kalman filter + long-time DLL, or according to the real-time characteristics of the output results of the long and short-time phase detectors, combined with the current application environment of the receiver, the real-time long and short-time integration results are dynamically and time-varyingly selected to better adapt to the changes in the dynamics and sensitivity of the spread spectrum signal.

[0054] This embodiment includes a first-stage coherent integrator, a second-stage coherent integrator, an Nth-stage coherent integrator, an incoherent integrator, a random access memory, a frame synchronization unit, and a tracking loop. It adopts a hierarchical integrator and a multi-stage symbol demodulation cascade to achieve the configuration capability of short, medium, long, and other integration durations, and each stage supports independent symbol demodulation. It supports the demodulation of spread spectrum signals modulated with different symbol rates at the same time, and has higher robustness when the symbol rate is dynamically switched. It achieves the technical effect of being able to flexibly demodulate spread spectrum signals with multiple symbol rates.

[0055] The first stage coherent integrator 10 , the second stage coherent integrator 20 , the Nth stage coherent integrator 30 , the non-coherent integrator 40 , the random access memory 50 , the frame synchronization unit 60 and the tracking loop 70 .

[0056] In one embodiment, the Nth stage coherent integrator 30 is further used to obtain symbol rate information in the current use environment, and determine specific information of the Nth stage coherent integrator according to the symbol rate information, wherein N is a positive integer.

[0057] In one embodiment, the first-stage coherent integrator 10 is further used to perform symbol soft demodulation on the first-stage integration result based on symbol soft demodulation 1 and store the generated first-stage symbol soft information into the random access memory.

[0058] In one embodiment, the second-stage coherent integrator 20 is further used to perform symbol soft demodulation on the second-stage integration result based on symbol soft demodulation 2 and store the generated second-stage symbol soft information into the random access memory.

[0059] In one embodiment, the Nth stage coherent integrator 30 is further used to perform symbol soft demodulation on the Nth stage integration result based on symbol soft demodulation N and store the generated Nth stage symbol soft information into the random access memory.

[0060] In one embodiment, the frame synchronization unit 60 is further configured to generate the symbol soft demodulation result according to the first-level symbol soft information, the second-level symbol soft information and the Nth-level symbol soft information.

[0061] It should be noted that the workflow described above is merely illustrative and does not limit the scope of protection of the present application. In practical applications, technicians in this field can select part or all of it according to actual needs to achieve the purpose of the present embodiment, and no limitation is made here.

[0062] In addition, for technical details not described in detail in this embodiment, reference can be made to the method for spread spectrum signal tracking provided in any embodiment of the present application, and will not be repeated here.

[0063] In addition, it should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0064] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0065] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as a read-only memory (ROM) / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a terminal device (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods of each embodiment of the present application.

[0066] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A spread spectrum signal tracking system supporting mixed symbol rates, characterized in that: include: A first-stage coherent integrator, a second-stage coherent integrator, an Nth-stage coherent integrator, a non-coherent integrator, a random access memory, a frame synchronization unit, and a tracking loop; The first-stage coherent integrator is used to perform coherent integration after receiving the spread spectrum signal to generate a first-stage integration result and a first-stage symbol soft demodulation result corresponding to the first-stage integration result, and store the first-stage integration result in the random access memory; The second-stage coherent integrator is used to perform coherent integration on the first-stage integration result to generate a second-stage integration result and a second-stage symbol soft demodulation result corresponding to the second-stage integration result, and store the second-stage integration result in the random access memory; The N-th level coherent integrator is used to perform coherent integration on the N-1-th level integration result generated by the N-1-th level coherent integrator to generate an N-th level integration result and an N-th level symbol soft demodulation result corresponding to the N-th level integration result, and store the N-th level integration result in the random access memory; The non-coherent integrator is used to obtain corresponding integration results from all coherent integrators and perform non-coherent integration; The frame synchronization unit is used to obtain all symbol soft demodulation results from all coherent integrators to determine symbol soft information, and perform a search based on the symbol soft information to obtain a search result; The tracking loop is used to obtain integration results from all the coherent integrators and the incoherent integrators, and perform filtering processing according to the integration results.

2. A spread spectrum signal tracking system supporting mixed symbol rates according to claim 1, characterized in that: The symbol rate information in the current use environment is obtained, and the specific information of the Nth stage coherent integrator is determined according to the symbol rate information, wherein N is a positive integer.

3. A spread spectrum signal tracking system supporting mixed symbol rate according to claim 1, characterized in that: The first-stage coherent integrator is also used to perform symbol soft demodulation on the first-stage integration result based on symbol soft demodulation 1 and store the generated first-stage symbol soft information in the random access memory.

4. A spread spectrum signal tracking system supporting mixed symbol rate according to claim 3, characterized in that: The second-stage coherent integrator is also used to perform symbol soft demodulation on the second-stage integration result based on symbol soft demodulation 2 and store the generated second-stage symbol soft information in the random access memory.

5. A spread spectrum signal tracking system supporting mixed symbol rate according to claim 4, characterized in that: The Nth level coherent integrator is also used to perform symbol soft demodulation on the Nth level integration result based on symbol soft demodulation N and store the generated Nth level symbol soft information into the random access memory.

6. A spread spectrum signal tracking system supporting mixed symbol rate according to claim 5, characterized in that: A symbol soft demodulation result is generated according to the first-level symbol soft information, the second-level symbol soft information and the Nth-level symbol soft information.

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