A device and method for jointly extracting L1P and L1M authorization codes from GPS BLOCK II satellites.

Abstract

The application discloses a GPS BLOCK II type satellite L1P and L1M authorized code joint extraction device and method, relates to the technical field of satellite navigation signal processing, and the output end of a signal tracking module is connected with the input end of a code stream extraction module; the signal tracking module tracks L1CA signals of GPS satellites and outputs baseband complex signals; based on the baseband complex signals, the code stream extraction module extracts L1P code streams and L1M code streams in II type satellite signals through a time domain orthogonal separation strategy; the signal tracking module comprises a carrier unit, a frequency mixing unit, an accumulation unit and a loop control unit. The code stream extraction module comprises L1CA20 code units, L1P sub-carrier units, L1P accumulation units, L1M sub-carrier units and L1M accumulation units, and each unit extracts L1P code streams and L1M code streams. The application solves the problems of poor separation effect, easy interference and low extraction precision in the prior art.

Description

Technical Field

[0001] This invention relates to the field of satellite navigation signal processing technology, specifically to a device and method for jointly extracting L1P and L1M license codes of GPS BLOCK II satellites. Background Technology

[0002] The Global Positioning System (GPS), as one of the most widely used satellite navigation systems, utilizes the L1 frequency signal carried by its Block II satellites. Due to its wide coverage and strong compatibility, it is widely used in core fields such as aerospace telemetry and control, high-precision navigation and positioning, military weapon guidance, and special communications. In practical applications, the L1 frequency signal contains multiple code streams, including the L1CA civilian code, the L1P license code, and the L1M license code. Among these, the L1P and L1M license codes, carrying critical information such as high-precision satellite navigation data and encrypted communication commands, have become the core acquisition targets for various navigation terminals and telemetry and control systems. Currently, mainstream technologies for extracting GPS L1 license codes mainly focus on independent extraction of single code streams or use simple filtering and separation methods to process the superimposed L1P and L1M signals. While these methods can meet basic navigation reception requirements, they are no longer suitable for high-precision, anti-interference, and multi-code stream synchronous extraction scenarios, and are insufficient for the application requirements of high-end terminals and complex operating conditions.

[0003] Currently, existing technologies for extracting L1P and L1M license codes from GPS BLOCK II satellites have significant technical shortcomings. On the one hand, mainstream frequency domain filtering separation methods suffer from signal distortion and energy loss due to the spectral overlap between L1P and L1M signals. Furthermore, they cannot effectively suppress intermodulation components and noise interference, directly compromising the accuracy and completeness of license code extraction. On the other hand, traditional solutions often employ a serial, independent extraction process, requiring repeated execution of core operations such as carrier tracking and pseudocode locking. This increases the consumption of terminal hardware resources and computational complexity, and fails to achieve synchronous extraction of dual license code streams. Additionally, the lack of targeted design for the BOC modulation characteristics of the L1 signal results in the inability to eliminate orthogonal component interference, further limiting the accuracy, reliability, and real-time performance of license code extraction. Consequently, these technologies struggle to meet the core requirements of complex applications such as modern high-precision navigation and real-time telemetry and control.

[0004] Therefore, there is an urgent need for a device for jointly extracting the L1P and L1M license codes of GPS BLOCK II satellites to solve the problems of poor separation effect, susceptibility to interference, and low extraction accuracy of existing technologies. Summary of the Invention

[0005] To address these issues, this invention provides a device and method for jointly extracting L1P and L1M authorization codes from GPS BLOCK II satellites, solving problems such as poor separation performance, susceptibility to interference, low extraction accuracy, and inability to extract L1P and L1M authorization codes simultaneously and efficiently in existing GPS BLOCK II satellite extraction methods.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a device for jointly extracting L1P and L1M license codes from GPS BLOCK II satellites, comprising a signal tracking module and a code stream extraction module; the output terminal of the signal tracking module is connected to the input terminal of the code stream extraction module; the signal tracking module is used to track the L1CA signal of GPS satellites and outputs a baseband complex signal after carrier stripping; based on the baseband complex signal, the code stream extraction module extracts the L1P and L1M code streams from the GPS BLOCK II satellite signals using a time-domain orthogonal separation strategy; The signal tracking module includes a carrier unit, a mixer unit, an accumulator unit, and a loop control unit; the output of the carrier unit is connected to the input of the mixer unit; the output of the mixer unit is connected to the input of the accumulator unit; the output of the accumulator unit is connected to the input of the loop control unit; and the output of the loop control unit is connected to the input of the carrier unit. The code stream extraction module includes an L1CA20 code unit, an L1P subcarrier unit, an L1P accumulation unit, an L1M subcarrier unit, and an L1M accumulation unit. The first output terminal of the L1CA20 code unit is connected to the signal tracking module and is used to transmit the local L1CA early / late code. The second to fifth output terminals of the L1CA20 code unit are respectively connected to the control terminals of the L1P subcarrier unit, the L1P accumulation unit, the L1M subcarrier unit, and the L1M accumulation unit, and are used to transmit the L1P subcarrier address, L1P chip overflow pulse, L1M subcarrier address, and L1M chip overflow pulse, respectively. The output terminal of the L1P subcarrier unit is connected to the first input terminal of the L1P accumulation unit. The output terminal of the L1M subcarrier unit is connected to the first input terminal of the L1M accumulation unit. The output terminal of the signal tracking module is connected to the second input terminals of the L1P accumulation unit and the L1M accumulation unit, respectively, and is used to transmit the baseband complex signal.

[0007] As a preferred embodiment of a joint extraction device for L1P and L1M license codes of GPS BLOCK II satellites, the carrier unit is used to generate an intermediate frequency carrier signal that matches the intermediate frequency signal of the L1 frequency point of the GPS BLOCK II satellite; the mixing unit is used to mix the input intermediate frequency signal with the intermediate frequency carrier signal, remove the carrier component, and generate a mixed signal; the accumulation unit is used to accumulate the mixed signal to generate an accumulation result; and the loop control unit is used to adjust the carrier signal parameters of the carrier unit according to the accumulation result to achieve tracking of the L1CA signal.

[0008] As a preferred embodiment of a GPS BLOCK II satellite L1P and L1M license code joint extraction device, the L1CA20 code unit is used to generate a BPSK(20) modulated L1CA20 code stream with a reference rate of 20.46MHz; the L1CA20 code unit generates and outputs the L1P subcarrier address, the L1P chip overflow pulse, the L1M subcarrier address, and the L1M chip overflow pulse by counting chips in the L1CA20 code stream and performing modulo 2 and modulo 4 operations respectively.

[0009] As a preferred embodiment of a GPS BLOCK II satellite L1P and L1M license code joint extraction device, the L1P subcarrier unit is a single-input lookup table structure, and the element sequence stored internally is [1 1]. Based on the L1P subcarrier address, the L1P subcarrier sequence is extracted through the L1P subcarrier unit to generate the L1P code stream. The L1M subcarrier unit is a two-input lookup table structure, and the element sequence stored internally is [-1 1-1 1]. Based on the L1M subcarrier address, the L1M subcarrier sequence is extracted through the L1M subcarrier unit to generate the L1M code stream.

[0010] As a preferred embodiment of a GPS BLOCK II satellite L1P and L1M license code joint extraction device, the L1P accumulation unit is used to coherently accumulate the Q-branch data of the baseband complex signal with the L1P subcarrier sequence, with an accumulation length of one L1P chip length; when the L1P chip overflow pulse is valid, the L1P accumulation unit resets the coherent accumulation value and outputs the L1P code stream, and the L1M component accumulation value is 0 when the L1P chip overflow pulse is aligned with the satellite signal L1P chip; the L1M accumulation unit is used to coherently accumulate the Q-branch data of the baseband complex signal with the L1M subcarrier sequence, with an accumulation length of one L1M chip length; when the L1M chip overflow pulse is valid, the L1M accumulation unit resets the coherent accumulation value and outputs the L1M code stream, and the L1P component accumulation value is 0 when the L1M chip overflow pulse is aligned with the satellite signal L1M chip.

[0011] This invention also provides a method for jointly extracting the L1P and L1M authorization codes of GPS BLOCK II satellites, comprising: The signal tracking module receives the intermediate frequency (IF) signal at the L1 frequency point of a GPS BLOCK II satellite. The carrier unit in the signal tracking module generates an IF carrier signal that matches the IF signal. The mixing unit mixes the IF signal and the IF carrier signal, initially removing the carrier component to obtain the mixed signal. The accumulation unit accumulates the mixed signal to generate a tracking feedback reference signal. The loop control unit outputs an adjustment command based on the tracking feedback reference signal. The carrier unit adjusts the parameters of the IF carrier signal according to the adjustment command to track the L1CA signal in the IF signal and complete the carrier component removal, generating a baseband complex signal. The signal tracking module outputs the baseband complex signal to the code stream extraction module. The code stream extraction module separates the baseband complex signal to obtain a Q-branch signal containing L1P and L1M components; the L1CA20 code unit in the code stream extraction module converts the GPS satellite L1CA signal into a BPSK(20) modulated signal based on the BPSK(20) modulation rule to generate an L1CA20 code stream; a local L1CA early / late code is generated based on the L1CA20 code stream and transmitted to the signal tracking module; based on the L1CA20 code stream, the L1CA20 code unit transmits the L1P subcarrier address, L1P chip overflow pulse, L1M subcarrier address, and L1M chip overflow pulse to the L1P subcarrier unit, L1P accumulation unit, L1M subcarrier unit, and L1M accumulation unit, respectively; The L1P subcarrier unit generates an L1P subcarrier sequence based on the L1P subcarrier address; the L1M subcarrier unit generates an L1M subcarrier sequence based on the L1M subcarrier address. Based on the L1P chip overflow pulse and time-domain orthogonal separation strategy, the L1P accumulation unit performs coherent accumulation processing on the Q-branch signal and the L1P subcarrier sequence to output the L1P code stream. Based on the L1M chip overflow pulse and the time-domain orthogonal separation strategy, the L1M accumulation unit performs coherent accumulation processing on the Q-branch signal and the L1M subcarrier sequence, and outputs the L1M code stream.

[0012] As a preferred embodiment of a method for jointly extracting L1P and L1M license codes from GPS BLOCK II satellites, the expression for the intermediate frequency signal received by the signal tracking module is: ;

[0013] In the formula, It is an intermediate frequency signal; t For time; For L1P signal power, For L1P components; This refers to the L1M signal power. For L1M components; For subcarrier; The power of the L1CA component; For L1CA components; The intermediate frequency carrier frequency; The initial phase of the intermediate frequency carrier is unknown; For noise; For intermodulation components; The expression for the baseband complex signal is: ;

[0014] In the formula, It is a baseband complex signal; j The imaginary unit; It is complex noise.

[0015] As a preferred embodiment of a method for jointly extracting L1P and L1M license codes from GPS BLOCK II satellites, the L1CA20 code unit generates an L1CA20 code stream with a reference rate of 20.46MHz by repeating each chip of the L1CA signal 20 times; the local L1CA early / late code spacing is configured as 1 / 8 chip; the L1CA20 code unit generates the L1P subcarrier address, the L1P chip overflow pulse, the L1M subcarrier address, and the L1M chip overflow pulse by counting chips in the L1CA20 code stream and performing modulo-2 and modulo-4 operations respectively; one L1CA chip length corresponds to 20 subcarrier half-cycle lengths, 10 L1P chip lengths, and 5 L1M chip lengths; the L1P component code rate is 10.23MHz, the L1M component code rate is 5.115MHz, the L1CA component code rate is 1.023MHz, and the subcarrier frequency is 10.23MHz.

[0016] As a preferred embodiment of a method for jointly extracting L1P and L1M authorization codes from GPS BLOCK II satellites, the L1P subcarrier unit is a single-input lookup table structure, and the element sequence in the lookup table is [1 1]; the expression for the coherent accumulation value of the Q-branch signal and the L1P subcarrier sequence in the L1P accumulation unit is: ;

[0017] In the formula, The coherent cumulative integration interval extracted from the L1P bitstream; This refers to the Q-branch component of the baseband complex signal; The local subcarrier sequence is used for L1P code stream extraction.

[0018] As a preferred embodiment of the method for jointly extracting L1P and L1M authorization codes from GPS BLOCK II satellites, the L1M subcarrier unit has a two-input lookup table structure, with the element sequence in the lookup table being [-1 1-1 1]; the expression for the coherent accumulation value of the Q-branch signal and the L1M subcarrier sequence in the L1M accumulation unit is: ;

[0019] In the formula, Local subcarrier sequence for L1M bitstream extraction; Matched subcarrier sequence for L1M code stream extraction.

[0020] The present invention has the following advantages: First, by adopting a time-domain orthogonal separation strategy, the L1P and L1M licensed bitstreams can be effectively separated, reducing signal interference caused by spectrum overlap, reducing signal distortion and energy loss, and ensuring the integrity of the extracted bitstream.

[0021] Secondly, it enables synchronous extraction of L1P and L1M licensed bitstreams, eliminating the need to repeatedly perform processes such as carrier tracking and pseudocode locking, thereby reducing hardware resource consumption and computational complexity and improving extraction efficiency.

[0022] Third, the design incorporates the BOC modulation characteristics of the GPS BLOCK II satellite L1 signal, which can effectively eliminate orthogonal component interference, improve the reliability of authorization code extraction, and adapt to complex application scenarios.

[0023] Fourth, the overall structure and process design is simple and reasonable, with good compatibility with existing signal tracking and code stream extraction architectures, making it easy to integrate into various navigation terminals and measurement and control equipment. Attached Figure Description

[0024] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0025] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0026] Figure 1 This is a schematic diagram of the timing relationship between the L1CA20, L1P, and L1M signal components mentioned in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the architecture of a GPS BLOCK II satellite L1P and L1M authorization code joint extraction device provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the principle framework of the L1CA20 code unit in a GPS BLOCK II satellite L1P and L1M authorization code joint extraction device provided in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the principle framework of the L1P accumulation unit in a GPS BLOCK II satellite L1P and L1M authorization code joint extraction device provided in Embodiment 1 of the present invention. Figure 5This is a schematic diagram of the principle framework of the L1M accumulation unit in a GPS BLOCK II satellite L1P and L1M authorization code joint extraction device provided in Embodiment 1 of the present invention; Figure 6 This is a flowchart illustrating a method for jointly extracting L1P and L1M authorization codes from GPS BLOCK II satellites, as provided in Embodiment 2 of the present invention. Figure 7 This is a schematic diagram of the L1P code stream extraction timing in a GPS BLOCK II satellite L1P and L1M license code joint extraction method provided in Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of the L1M code stream extraction timing in a GPS BLOCK II satellite L1P and L1M authorization code joint extraction method provided in Embodiment 2 of the present invention; Figure 9 This is a constellation diagram illustrating the L1P code stream extraction in a GPS BLOCK II satellite L1P and L1M license code joint extraction method provided in Embodiment 2 of the present invention. Figure 10 This is a constellation diagram illustrating the L1M code stream extraction in a GPS BLOCK II satellite L1P and L1M license code joint extraction method provided in Embodiment 2 of the present invention. Detailed Implementation

[0027] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0028] As is well known, L1CA uses BPSK(1) modulation, and L1CA can be equivalent to the BPSK(20) modulated signal L1CA20. L1CA20 can be obtained by repeating each chip of L1CA 20 times. During satellite signal tracking, using high-sampling-rate intermediate frequency data and narrow-range correlation technology can achieve high-precision L1CA20 tracking accuracy, thereby obtaining accurate bit synchronization pulses for L1P and L1M. The timing relationship between the L1CA20, L1P, and L1M signal components is as follows: Figure 1 As shown, Tc represents the length of an L1M chip. From Figure 1It can be seen that when the Q branch of the baseband complex signal after carrier stripping is coherently accumulated within one L1P chip period, the accumulated value of the L1M component is 0; when the Q branch of the baseband complex signal after carrier stripping is coherently accumulated with the XBOC(10,5) subcarrier within one L1M chip period, the accumulated value of the L1P component is 0. Therefore, by performing coherent accumulation of the Q branch signal with different subcarrier signals for different durations, the time-domain orthogonal separation of the L1P and L1M signal components is achieved.

[0029] Based on this view Figure 2 Embodiment 1 of the present invention provides a device for jointly extracting L1P and L1M license codes of GPS BLOCK II satellites, including a signal tracking module and a code stream extraction module; the output terminal of the signal tracking module is connected to the input terminal of the code stream extraction module; the signal tracking module is used to track the L1CA signal of GPS satellites and outputs the baseband complex signal after carrier stripping; based on the baseband complex signal, the code stream extraction module extracts the L1P code stream and L1M code stream in the GPS BLOCK II satellite signal through a time-domain orthogonal separation strategy.

[0030] Specifically, the signal tracking module and the code stream extraction module are the two core components of the device. They are connected through a unidirectional data transmission link, forming a complete working link of "signal preprocessing - code stream extraction". As the front-end preprocessing unit, the core function of the signal tracking module is to receive the intermediate frequency signal of the L1 frequency point of the GPS BLOCK II satellite, lock the L1CA signal through the collaborative work of its internal units, and after carrier stripping, continuously transmit the clean baseband complex signal to the code stream extraction module, providing the basic signal for subsequent license code extraction. As the back-end core processing unit, the code stream extraction module receives the baseband complex signal and, relying on the time-domain orthogonal separation strategy, separates and extracts the L1P and L1M license code streams from the Q branch of the baseband complex signal through the collaborative cooperation of its internal units. The connection between the two ensures the continuity and stability of signal transmission, realizing an integrated process from satellite signal reception and preprocessing to license code extraction.

[0031] In this embodiment, the signal tracking module includes a carrier unit, a mixer unit, an accumulator unit, and a loop control unit; the output terminal of the carrier unit is connected to the input terminal of the mixer unit; the output terminal of the mixer unit is connected to the input terminal of the accumulator unit; the output terminal of the accumulator unit is connected to the input terminal of the loop control unit; and the output terminal of the loop control unit is connected to the input terminal of the carrier unit.

[0032] Specifically, the signal tracking module has four units forming a closed-loop control link. The units are connected through a dedicated signal interface, and the data transmission follows the logic of "carrier generation - mixing and stripping - accumulation feedback - adjustment and calibration". The carrier unit, as the core of carrier signal generation, generates an intermediate frequency (IF) carrier signal that matches the frequency and phase of the input IF signal according to the adjustment commands of the loop control unit. This carrier signal is then transmitted in real-time to the mixing unit via its output. The mixing unit receives the satellite IF signal and the IF carrier signal output by the carrier unit, and performs mixing operations to initially remove the carrier component from the IF signal. The mixed baseband signal is then transmitted to the accumulation unit. The accumulation unit accumulates the mixed baseband signal to generate a tracking feedback reference signal, which reflects the current tracking accuracy of the L1CA signal. This signal is then transmitted to the loop control unit. The loop control unit analyzes the feedback reference signal, determines the current carrier tracking deviation, and outputs frequency and phase adjustment commands, which are fed back to the carrier unit via its output. The carrier unit adjusts the parameters of its generated carrier signal according to the adjustment commands. This closed-loop process ensures stable tracking of the L1CA signal and complete removal of the carrier component, guaranteeing that the output baseband complex signal meets the requirements for subsequent code stream extraction.

[0033] In this embodiment, the code stream extraction module includes an L1CA20 code unit, an L1P subcarrier unit, an L1P accumulation unit, an L1M subcarrier unit, and an L1M accumulation unit. The first output terminal of the L1CA20 code unit is connected to the signal tracking module and is used to transmit the local L1CA early / late code. The second to fifth output terminals of the L1CA20 code unit are respectively connected to the control terminals of the L1P subcarrier unit, the L1P accumulation unit, the L1M subcarrier unit, and the L1M accumulation unit, and are respectively used to transmit the L1P subcarrier address, the L1P chip overflow pulse, the L1M subcarrier address, and the L1M chip overflow pulse. The output terminal of the L1P subcarrier unit is connected to the first input terminal of the L1P accumulation unit. The output terminal of the L1M subcarrier unit is connected to the first input terminal of the L1M accumulation unit. The output terminal of the signal tracking module is connected to the second input terminals of the L1P accumulation unit and the L1M accumulation unit, respectively, and is used to transmit the baseband complex signal.

[0034] Specifically, the five units within the code stream extraction module have clearly defined roles and work collaboratively, forming an architecture with the L1CA20 code unit as the control core and two accumulation units as the extraction core. The logic of the connections between the units and the details of data transmission are as follows: The L1CA20 code unit serves as the control core. Its first output is connected to the loop control unit or mixer unit of the signal tracking module, transmitting the local L1CA early / late code to assist the signal tracking module in locking the pseudo-code of the L1CA signal and improving tracking stability. Its second to fifth outputs establish control signal links with the control terminals of four units, respectively. Specifically, it transmits the L1P subcarrier address to the L1P subcarrier unit to control the L1P subcarrier unit to generate a matching L1P subcarrier sequence; it transmits L1P chip overflow pulses to the L1P accumulator unit to trigger the coherent accumulation operation and reset the accumulated value of the L1P accumulator unit; it transmits the L1M subcarrier address to the L1M subcarrier unit to control it to generate a matching L1M subcarrier sequence; and it transmits L1M chip overflow pulses to the L1M accumulator unit to trigger the coherent accumulation operation and reset the accumulated value of the L1M accumulator unit.

[0035] After receiving the address control signal from the L1CA20 code unit, the L1P subcarrier unit generates the corresponding L1P subcarrier sequence and transmits it to the first input of the L1P accumulator unit through its output. Similarly, the L1M subcarrier unit generates the L1M subcarrier sequence and transmits it to the first input of the L1M accumulator unit. The output of the signal tracking module transmits the baseband complex signal to the second inputs of the L1P and L1M accumulator units respectively through two parallel data links, providing input signals for coherent accumulation. Finally, based on the received subcarrier sequence, baseband complex signal, and chip overflow pulse, the L1P and L1M accumulator units extract the L1P and L1M licensed code streams respectively using a time-domain orthogonal separation strategy, achieving synchronous extraction of the dual licensed code streams.

[0036] In this embodiment, the L1CA20 code unit is used to generate a BPSK(20) modulated L1CA20 code stream with a reference rate of 20.46MHz; the L1CA20 code unit generates and outputs the L1P subcarrier address, the L1P chip overflow pulse, the L1M subcarrier address, and the L1M chip overflow pulse by performing chip counting on the L1CA20 code stream and performing modulo 2 and modulo 4 operations respectively.

[0037] Specifically, such as Figure 3As shown, the L1CA20 code unit is the core control unit of the code stream extraction module. Its core functions revolve around the generation of the L1CA20 code stream and the derivation of subsequent control signals, providing a synchronization reference and control signal support for the extraction of L1P and L1M licensed code streams. In the L1CA20 code stream generation stage, this unit, based on the BPSK(20) modulation rule, converts the L1CA signal of the GPS satellite L1 frequency point into an equivalent BPSK(20) modulated signal. By repeating each chip of the original L1CA code stream 20 times, an L1CA20 code stream with a reference rate of 20.46MHz is generated. This rate matches the subcarrier frequency and code rate of the L1P and L1M signals, providing a stable reference timing for the generation of subsequent control signals. In the control signal generation stage, the L1CA20 code unit has a built-in chip counter that counts the generated L1CA20 code stream chips in real time. It generates corresponding control signals through two different modulo operations: First, it processes the chip counting result through modulo 2 operation to generate the L1P subcarrier address and L1P chip overflow pulse. The L1P subcarrier address controls the L1P subcarrier unit to generate a subcarrier sequence matching the L1P signal, and the L1P chip overflow pulse triggers the L1P accumulation unit to start coherent accumulation operation, ensuring that the accumulation period is synchronized with the L1P chip period. Second, it processes the chip counting result through modulo 4 operation to generate the L1M subcarrier address and L1M chip overflow pulse. The L1M subcarrier address controls the L1M subcarrier unit to generate a subcarrier sequence adapted to the BOC(10,5) modulation characteristics of the L1M signal, and the L1M chip overflow pulse triggers the L1M accumulation unit to start coherent accumulation operation, achieving synchronization with the L1M chip period. The design of the above-mentioned modulo 2 and modulo 4 operations is compatible with the code rate ratio of L1P and L1M signals (L1P code rate 10.23MHz, L1M code rate 5.115MHz), ensuring that the generated control signal can match the working timing of the L1P and L1M accumulation units, providing a reliable synchronization guarantee for the implementation of the time-domain orthogonal separation strategy, and realizing the integrated generation of control signals, simplifying the overall structure of the code stream extraction module.

[0038] In this embodiment, the L1P subcarrier unit is a single-input lookup table structure, and the element sequence stored inside is

[11] . Based on the L1P subcarrier address, the L1P subcarrier sequence is extracted through the L1P subcarrier unit to generate the L1P code stream. The L1M subcarrier unit is a two-input lookup table structure, and the element sequence stored inside is [-1 1-1 1]. Based on the L1M subcarrier address, the L1M subcarrier sequence is extracted through the L1M subcarrier unit to generate the L1M code stream.

[0039] Specifically, the L1P subcarrier unit and the L1M subcarrier unit are the core hardware carriers of the time-domain orthogonal separation strategy, providing accurate matching local subcarrier reference signals for the coherent accumulation and extraction of the two licensed code streams. Both adopt a lookup table structure design, which not only adapts to the inherent modulation characteristics of the L1P and L1M signals at the L1 frequency of the GPS BLOCK II satellite, but also simplifies the hardware implementation logic and ensures strict synchronization between the output sequence and the front-end timing. Among them, the L1P subcarrier unit adopts a single-input lookup table structure to adapt to the 1-bit L1P subcarrier address generated by the L1CA 20 code unit through modulo 2 operation. The single-input addressing logic is completely matched with the 1-bit address width, eliminating the need for additional address decoding circuits. It can directly respond to the address signal to complete the sequence output, greatly reducing hardware resource consumption. The [1 1] element sequence stored internally is completely matched with the code rate characteristics and chip period of the L1P signal of 10.23MHz. It will not introduce additional phase deviation in the coherent accumulation interval, and can form a stable orthogonal relationship with the subcarrier of the L1M signal. During operation, the input of the L1P subcarrier unit is directly connected to the L1CA 20 code unit, receiving the L1P subcarrier address in real time. Within each address clock cycle, the unit reads the corresponding element in the lookup table according to the input 1-bit address index and continuously outputs the L1P subcarrier sequence that is perfectly aligned with the L1P chip timing. This sequence is directly transmitted to the L1P accumulation unit as a local reference signal for coherent accumulation operation, providing a core orthogonal matching reference for L1P code stream extraction.

[0040] The L1M subcarrier unit adopts a two-input lookup table structure to adapt to the 2-bit L1M subcarrier address generated by the L1CA 20 code unit through modulo-4 operation. The two-input addressing logic can directly cover the four addressing states corresponding to the 2-bit address without the need for additional address splicing circuits. It can accurately respond to the address signal generated by modulo-4 counting and adapt to the modulation characteristics of the L1M signal BOC (10,5). The [-1 1-1 1] element sequence stored internally is the standard discrete sequence of the BOC (10,5) modulated subcarrier, which matches the subcarrier waveform, 10.23MHz subcarrier frequency, and 5.115MHz code rate of the L1M signal. It can form coherent superposition with the L1M signal component during coherent accumulation and orthogonally cancel with the L1P signal component. It is the core foundation for realizing the time-domain orthogonal separation of the two code streams. During operation, the input of the L1M subcarrier unit is directly connected to the L1CA 20 code unit, receiving the L1M subcarrier address in real time. Within each address clock cycle, the unit reads the corresponding element in the lookup table according to the input 2-bit address index and continuously outputs the L1M subcarrier sequence that is perfectly aligned with the L1M chip timing and BOC modulation characteristics. This sequence is directly transmitted to the L1M accumulation unit as a local reference signal for coherent accumulation operations, ensuring that interference from the L1P component can be effectively canceled during the L1M code stream extraction process, ultimately achieving crosstalk-free synchronous extraction of the two licensed code streams.

[0041] In this embodiment, the L1P accumulation unit is used to coherently accumulate the Q-branch data of the baseband complex signal with the L1P subcarrier sequence, and the accumulation length is one L1P chip length. When the L1P chip overflow pulse is valid, the L1P accumulation unit resets the coherent accumulation value and outputs the L1P code stream, and the L1M component accumulation value is 0 when the L1P chip overflow pulse is aligned with the L1P chip of the satellite signal. The L1M accumulation unit is used to coherently accumulate the Q-branch data of the baseband complex signal with the L1M subcarrier sequence, and the accumulation length is one L1M chip length. When the L1M chip overflow pulse is valid, the L1M accumulation unit resets the coherent accumulation value and outputs the L1M code stream, and the L1P component accumulation value is 0 when the L1M chip overflow pulse is aligned with the L1M chip of the satellite signal.

[0042] Specifically, such as Figure 4 As shown, the core functionality of the L1P accumulator unit is implemented in three parts: First, coherent accumulation operation: The two signal input terminals of the L1P accumulation unit are directly connected to the signal tracking module and the L1P subcarrier unit, respectively, to receive the baseband complex signal Q branch data (containing only L1P and L1M components, without L1CA civilian code and intermodulation component interference) and L1P subcarrier sequence after the carrier is stripped in real time. In each signal sampling period, the synchronously collected Q branch sampling data and the corresponding L1P subcarrier sequence are multiplied first, and then the result is continuously accumulated within one L1P chip length. Here, one L1P chip length is set as the accumulation period, which is not only completely matched with the L1P signal code rate of 10.23MHz, but also aligned with the timing period of the L1CA (20) code unit modulo 2 counting, ensuring that the accumulation process is completely synchronized with the timing of the L1P chip, and maximizing the coherent accumulation gain of the target component.

[0043] Second, the code stream output and accumulation reset: The control terminal of the L1P accumulation unit is directly connected to the L1CA20 code unit and receives the L1P chip overflow pulse in real time. When the pulse is valid, it indicates that the accumulation operation of the current L1P chip cycle is completed. The unit first outputs the final coherent accumulation value of the current cycle, and determines the polarity of the corresponding L1P chip by the positive or negative sign of the accumulation value, thus completing the output of the L1P code stream. Then, it automatically resets the value of the accumulator to the initial state, preparing for the accumulation operation of the next L1P chip cycle, and realizing the seamless connection between code stream output and accumulation operation.

[0044] Third, orthogonal interference cancellation: When the L1P chip overflow pulse is completely aligned with the L1P chip of the satellite signal, it means that the locally generated timing and subcarrier sequence are synchronized with the L1P signal transmitted by the satellite. At this time, within the accumulation period of one L1P chip, the BOC(10,5) modulated subcarrier of the L1M component and the local L1P subcarrier sequence satisfy the time-domain orthogonality characteristic. The positive and negative values ​​of the multiplication result of the L1M component cancel each other out within the accumulation period, and the final accumulation value is 0, ensuring that the output L1P code stream is free from L1M component crosstalk and achieving pure extraction of the target code stream.

[0045] like Figure 5 As shown, the working logic of the L1M accumulator unit is symmetrically adapted to the L1P accumulator unit. Furthermore, it is specifically designed for the BOC(10,5) modulation characteristics of the L1M signal. The core functionality is also divided into three parts: First, coherent accumulation operation: The two signal input terminals of the L1M accumulation unit are directly connected to the signal tracking module and the L1M subcarrier unit, respectively, to synchronously receive the Q-branch data of the baseband complex signal and the L1M subcarrier sequence. After completing the multiplication operation of the Q-branch data and the L1M subcarrier sequence in each sampling period, the operation result is continuously accumulated within one L1M chip length. Here, one L1M chip length is set as the accumulation period, which is perfectly matched with the code rate of the L1M signal of 5.115MHz. One L1M chip length corresponds exactly to two L1P chip lengths, which is perfectly aligned with the timing period of the modulo-4 counting of the L1CA20 code unit. This adapts to the subcarrier period characteristics of the BOC(10,5) modulation of the L1M signal, ensuring the coherent superposition effect of the target components.

[0046] Second, the code stream output and accumulation reset: The control terminal of the L1M accumulation unit is directly connected to the L1CA20 code unit and receives the L1M chip overflow pulse in real time. When the pulse is valid, it indicates that the accumulation operation of the current L1M chip cycle is completed. The unit first outputs the final coherent accumulation value of the current cycle, and determines the polarity of the generated L1M chip by the positive or negative sign of the accumulation value, thus completing the output of the L1M code stream. Then, the accumulator value is reset to realize continuous code stream extraction operation.

[0047] Third, orthogonal interference cancellation: When the L1M chip overflow pulse is fully aligned with the L1M chip of the satellite signal, the local timing, subcarrier sequence and satellite L1M signal are synchronized. At this time, within the accumulation period of one L1M chip, the subcarrier of the L1P component and the local subcarrier sequence of L1M satisfy the time-domain orthogonality characteristic. The multiplication result of the L1P component cancels out the positive and negative values ​​within the accumulation period, and the final accumulation value is 0, ensuring that the output L1M code stream is free from L1P component crosstalk.

[0048] In summary, the operating principle of this invention is as follows: The signal tracking module receives the intermediate frequency input signal at the L1 frequency point of the GPS BLOCK II satellite. This signal is a mixed signal containing L1CA civilian code, L1P license code, L1M license code, carrier component, noise and intermodulation components. Simultaneously, the L1CA 20 code unit in the code stream extraction module repeats each chip of the original L1CA code 20 times based on the BPSK(20) modulation rule to generate an L1CA20 code stream with a reference rate of 20.46MHz. Based on this code stream, a local L1CA early and late code is generated and transmitted to the signal tracking module to provide a local reference for pseudocode locking of the L1CA signal.

[0049] Based on this, a carrier tracking closed loop is formed within the signal tracking module: the carrier unit generates an intermediate frequency carrier signal that matches the input intermediate frequency signal and transmits it to the mixing unit; the mixing unit performs mixing operations on the intermediate frequency input signal and the intermediate frequency carrier signal, initially stripping the carrier component from the signal, and outputs the mixed baseband signal to the accumulation unit; the accumulation unit performs coherent accumulation processing on the mixed signal in conjunction with the local L1CA early and late code, generating a tracking feedback reference signal that reflects the current carrier tracking deviation and pseudo-code tracking status, and transmits it to the loop control unit; the loop control unit performs deviation calculation on the reference signal and outputs the corresponding frequency and phase adjustment commands to the carrier unit; the carrier unit adjusts the parameters of the intermediate frequency carrier signal in real time according to the adjustment commands, thereby forming a closed-loop control to continuously achieve stable carrier tracking and pseudo-code locking of the L1CA signal. After closed-loop adjustment, the mixing signal completes the stripping of the carrier component, and the signal tracking module finally outputs a baseband complex signal. In this signal, the L1CA code stream and intermodulation components are concentrated in the I branch, and the L1P and L1M license code components are concentrated in the Q branch, providing an input signal without civilian code interference for subsequent code stream extraction.

[0050] The L1CA20 code unit has a built-in chip counter that performs real-time chip counting on the generated L1CA20 code stream. It generates four synchronization control signals through two modulo operations: First, it performs a modulo-2 operation on the chip count value to generate a 1-bit wide L1P subcarrier address and an L1P chip overflow pulse. The L1P subcarrier address is transmitted to the L1P subcarrier unit, and the L1P chip overflow pulse is transmitted to the L1P accumulation unit. The timing is perfectly matched with the 10.23MHz code rate of the L1P signal. Second, it performs a modulo-4 operation on the chip count value to generate a 2-bit wide L1M subcarrier address and an L1M chip overflow pulse. The L1M subcarrier address is transmitted to the L1M subcarrier unit, and the L1M chip overflow pulse is transmitted to the L1M accumulation unit. The timing is perfectly matched with the 5.115MHz code rate and BOC(10,5) modulation characteristics of the L1M signal.

[0051] The L1P subcarrier unit and the L1M subcarrier unit synchronize the generation of the matching subcarrier sequence based on the received address signal: The L1P subcarrier unit adopts a single-input lookup table structure, internally stores the [1 1] element sequence, and performs real-time lookup addressing according to the input 1-bit L1P subcarrier address, continuously outputting the L1P subcarrier sequence that is completely aligned with the L1P chip timing to the L1P accumulation unit; The L1M subcarrier unit adopts a two-input lookup table structure, internally stores the [-1 1-1 1] element sequence that matches the BOC (10,5) modulated subcarrier, and performs real-time lookup addressing according to the input 2-bit L1M subcarrier address, continuously outputting the L1M subcarrier sequence that is completely aligned with the L1M chip timing and modulation characteristics to the L1M accumulation unit.

[0052] The L1P accumulation unit and the L1M accumulation unit operate in parallel, sharing the same baseband complex signal Q-branch data. The two extraction processes are independent and synchronized in timing: For L1P code stream extraction, the L1P accumulation unit synchronously receives baseband Q-branch data, the L1P subcarrier sequence, and L1P chip overflow pulses. Within each sampling period, it first performs a multiplication operation between the synchronously acquired Q-branch data and the corresponding L1P subcarrier sequence, then continuously coherently accumulates the result over one L1P chip length. When the L1P chip overflow pulse is valid, it indicates the current L1P code... Once the accumulation operation of the chip period is completed, if the L1P chip overflow pulse aligns with the L1P chip of the satellite signal, the L1M component satisfies the time-domain orthogonality characteristic with the L1P subcarrier sequence within this accumulation period. The positive and negative values ​​of their multiplication operation results completely cancel each other out within the accumulation period, and the final accumulation value is 0, retaining only the coherent accumulation result of the L1P component. The L1P accumulation unit then determines the polarity of the corresponding L1P chip based on the positive or negative sign of the accumulation result, completes the output of the L1P code stream, and automatically resets the accumulator value to enter the accumulation operation of the next L1P chip period.

[0053] For L1M code stream extraction, the L1M accumulation unit synchronously receives baseband Q-branch data, L1M subcarrier sequence, and L1M chip overflow pulse. After performing the multiplication operation between the Q-branch data and the L1M subcarrier sequence within each sampling period, the result is continuously coherently accumulated over one L1M chip length. When the L1M chip overflow pulse is valid, it indicates that the accumulation operation for the current L1M chip period is complete. If the L1M chip overflow pulse aligns with the L1M chip of the satellite signal, the L1P component and the L1M subcarrier sequence satisfy the time-domain orthogonality characteristic within this accumulation period. The positive and negative values ​​of their multiplication results completely cancel each other out within the accumulation period, resulting in a final accumulation value of 0. Only the coherent accumulation result of the L1M component is retained. The L1M accumulation unit then determines the polarity of the corresponding L1M chip based on the sign of the accumulation result, completing the output of the L1M code stream. Simultaneously, it automatically resets the accumulator value and enters the accumulation operation for the next L1M chip period. Example 2

[0054] See Figure 6 Embodiment 2 of the present invention also provides a method for jointly extracting the L1P and L1M authorization codes of GPS BLOCK II satellites, including: S1. The signal tracking module receives the intermediate frequency (IF) signal at frequency L1 of a GPS BLOCK II satellite. The carrier unit in the signal tracking module generates an IF carrier signal that matches the IF signal. The mixing unit mixes the IF signal and the IF carrier signal, initially removing the carrier component to obtain the mixed signal. The accumulation unit accumulates the mixed signal to generate a tracking feedback reference signal. The loop control unit outputs an adjustment command based on the tracking feedback reference signal. The carrier unit adjusts the parameters of the IF carrier signal according to the adjustment command to track the L1CA signal in the IF signal and complete the carrier component removal, generating a baseband complex signal. The signal tracking module outputs the baseband complex signal to the code stream extraction module. S2. The code stream extraction module separates the baseband complex signal to obtain a Q-branch signal containing L1P and L1M components. The L1CA20 code unit in the code stream extraction module converts the GPS satellite L1CA signal into a BPSK(20) modulated signal based on the BPSK(20) modulation rule, generating an L1CA20 code stream. Based on the L1CA20 code stream, a local L1CA early / late code is generated and transmitted to the signal tracking module. Based on the L1CA20 code stream, the L1CA20 code unit transmits the L1P subcarrier address, L1P chip overflow pulse, L1M subcarrier address, and L1M chip overflow pulse to the L1P subcarrier unit, L1P accumulation unit, L1M subcarrier unit, and L1M accumulation unit, respectively. S3. The L1P subcarrier unit generates an L1P subcarrier sequence based on the L1P subcarrier address; the L1M subcarrier unit generates an L1M subcarrier sequence based on the L1M subcarrier address. S4. Based on the L1P chip overflow pulse and time-domain orthogonal separation strategy, the L1P accumulation unit performs coherent accumulation processing on the Q branch signal and the L1P subcarrier sequence, and outputs the L1P code stream. S5. Based on the L1M chip overflow pulse and the time-domain orthogonal separation strategy, the L1M accumulation unit performs coherent accumulation processing on the Q branch signal and the L1M subcarrier sequence, and outputs the L1M code stream.

[0055] In this embodiment, in step S1, the signal tracking module receives the intermediate frequency (IF) signal at the L1 frequency point of a GPS BLOCK II satellite; the carrier unit in the signal tracking module generates an IF carrier signal that matches the IF signal; the mixing unit mixes the IF signal and the IF carrier signal, initially stripping the carrier component to obtain the mixed signal; the accumulation unit accumulates the mixed signal to generate a tracking feedback reference signal; the loop control unit outputs an adjustment command based on the tracking feedback reference signal; the carrier unit adjusts the parameters of the IF carrier signal according to the adjustment command to track the L1CA signal in the IF signal and complete the carrier component stripping to generate a baseband complex signal; the signal tracking module outputs the baseband complex signal to the code stream extraction module.

[0056] Specifically, the intermediate frequency (IF) signal received by the signal tracking module is a mixed signal of the GPSBLOCK II satellite L1 frequency point after being received by the antenna and down-converted by the RF front-end. This signal contains L1CA civilian code components, L1P license code components, L1M license code components, IF carrier components, channel noise, and signal intermodulation components, and is the signal source for all subsequent processing. The carrier unit generates an IF carrier signal based on the nominal IF frequency of the L1 frequency point in the initial state. The mixing unit performs mixing of the IF signal and the local IF carrier through multiplication operations, and uses the spectrum shifting principle to shift the signal from the carrier frequency band to the baseband frequency band, achieving initial carrier component stripping and outputting a zero-IF mixed signal. The accumulation unit, in conjunction with the local L1CA early and late codes transmitted by the code stream extraction module, performs coherent accumulation processing on the mixed signal. The generated tracking feedback reference signal reflects the frequency and phase deviations between the current local carrier and the satellite signal carrier, as well as the tracking error of the L1CA signal pseudocode. The loop control unit performs deviation calculation based on this reference signal and outputs corresponding frequency and phase adjustment commands to the carrier unit. The carrier unit corrects the frequency and phase parameters of the intermediate frequency carrier signal in real time according to the commands, thereby forming a complete closed-loop tracking loop. This continuously eliminates Doppler frequency shift, carrier initial phase deviation, and phase disturbance caused by the satellite motion, achieving stable carrier tracking and pseudocode locking of the L1CA signal.

[0057] After continuous closed-loop calibration, the carrier component in the mixed signal is completely stripped, ultimately generating a baseband complex signal. This signal is output in complex form, with the real component (I branch) carrying the L1CA civilian code component and signal intermodulation component, and the imaginary component (Q branch) carrying the L1P and L1M license code components. This completely avoids interference from the L1CA civilian code to the subsequent license code extraction. The signal tracking module stably transmits this baseband complex signal to the code stream extraction module, providing the core input for subsequent code stream separation and extraction.

[0058] The expression for the intermediate frequency signal received by the signal tracking module is as follows: ;

[0059] In the formula, It is an intermediate frequency signal; t For time; For L1P signal power, For L1P components; This refers to the L1M signal power. For L1M components; For subcarrier; The power of the L1CA component; For L1CA components; The intermediate frequency carrier frequency; The initial phase of the intermediate frequency carrier is unknown; For noise; For intermodulation components; The expression for the baseband complex signal is: ;

[0060] In the formula, It is a baseband complex signal; j The imaginary unit; It is complex noise.

[0061] In this embodiment, in step S2, the code stream extraction module separates the baseband complex signal to obtain a Q-branch signal containing L1P and L1M components; the L1CA20 code unit in the code stream extraction module converts the GPS satellite L1CA signal into a BPSK(20) modulated signal based on the BPSK(20) modulation rule, and generates an L1CA20 code stream; a local L1CA early / late code is generated based on the L1CA20 code stream and transmitted to the signal tracking module; based on the L1CA20 code stream, the L1CA20 code unit transmits the L1P subcarrier address, L1P chip overflow pulse, L1M subcarrier address and L1M chip overflow pulse to the L1P subcarrier unit, L1P accumulation unit, L1M subcarrier unit and L1M accumulation unit respectively.

[0062] Specifically, the code stream extraction module directly extracts the imaginary component of the baseband complex signal based on its inherent structure, obtaining a pure Q-branch signal. This signal contains only L1P and L1M licensed code components and is free from L1CA civilian code interference. The L1CA20 code unit repeats each chip of the original 1.023MHz L1CA code at equal intervals 20 times based on the BPSK(20) modulation rule, generating an L1CA20 code stream with a reference rate of 20.46MHz. This code rate is an integer multiple of the L1P signal's 10.23MHz code rate, the L1M signal's 5.115MHz code rate, and the 10.23MHz subcarrier frequency, providing a timing reference for the subsequent generation of synchronization control signals. Based on the L1CA20 code stream, the L1CA20 code unit generates local L1CA early-late codes, with the early-late code spacing configured as 1 / 8 chip, and transmits them to the accumulation unit of the signal tracking module. Simultaneously, the L1CA20 code unit has a built-in chip counter that performs real-time continuous chip counting on the 20.46MHz L1CA20 code stream, generating four synchronization control signals through two different modulo operations: such as... Figure 7 As shown, a modulo-2 operation is performed on the chip count value to generate a 1-bit wide L1P subcarrier address and an L1P chip overflow pulse. The timing period perfectly matches the 10.23MHz code rate of the L1P signal. Figure 8 As shown, a modulo-4 operation is performed on the chip count value to generate a 2-bit L1M subcarrier address and an L1M chip overflow pulse. The timing period perfectly matches the 5.115MHz code rate of the L1M signal. Four control signals are synchronously transmitted to their respective units, providing unified timing triggering and addressing control for subsequent subcarrier sequence generation and coherent accumulation operations, ensuring that all operations in the entire link are strictly synchronized with the satellite signal chip timing.

[0063] In this embodiment, in step S3, the L1P subcarrier unit generates an L1P subcarrier sequence based on the L1P subcarrier address; the L1M subcarrier unit generates an L1M subcarrier sequence based on the L1M subcarrier address.

[0064] Specifically, the L1P subcarrier unit adopts a single-input lookup table structure, and internally stores a sequence of elements [1 1] that matches the modulation characteristics of the L1P signal. Its single-input addressing logic is fully compatible with the 1-bit L1P subcarrier address generated by the modulo 2 operation of the L1CA20 code unit, without the need for an additional address decoding circuit. During operation, the L1P subcarrier unit receives the L1P subcarrier address in real time. In each address clock cycle, it reads the corresponding element in the lookup table according to the input 1-bit address index and continuously outputs the L1P subcarrier sequence that is fully aligned with the timing of the L1P chip. This sequence will not introduce additional phase deviation in the coherent accumulation period, and can form the maximum coherent gain with the L1P signal component. At the same time, it forms a stable time-domain orthogonal relationship with the BOC modulation subcarrier of the L1M signal.

[0065] The expression for the coherent accumulation value of the Q-branch signal and the L1P subcarrier sequence by the L1P accumulation unit is as follows: ;

[0066] In the formula, The coherent cumulative integration interval extracted from the L1P bitstream; This refers to the Q-branch component of the baseband complex signal; The local subcarrier sequence is used for L1P code stream extraction.

[0067] In this embodiment, the L1M subcarrier unit adopts a two-input lookup table structure. It internally stores a standard subcarrier discrete sequence [-1 1-1 1] that perfectly matches the modulation characteristics of the L1M signal BOC(10,5). Its two-input addressing logic is perfectly compatible with the 2-bit L1M subcarrier address generated by the modulo-4 operation of the L1CA20 code unit, and can directly cover the four addressing states corresponding to the 2-bit address. During operation, the L1M subcarrier unit receives the L1M subcarrier address in real time. In each address clock cycle, it reads the corresponding element in the lookup table according to the input 2-bit address index and continuously outputs the L1M subcarrier sequence that is perfectly aligned with the L1M chip timing and the BOC modulated subcarrier waveform. This sequence can form the maximum coherence gain with the L1M signal component and form a stable time-domain orthogonal relationship with the L1P signal component, providing the core conditions for the crosstalk-free separation of the two code streams.

[0068] The expression for the coherent accumulation value of the Q-branch signal and the L1M subcarrier sequence by the L1M accumulation unit is as follows: ;

[0069] In the formula, Local subcarrier sequence for L1M bitstream extraction; Matched subcarrier sequence for L1M code stream extraction.

[0070] In this embodiment, in step S4, based on the L1P chip overflow pulse and time-domain orthogonal separation strategy, the L1P accumulation unit performs coherent accumulation processing on the Q branch signal and the L1P subcarrier sequence, and outputs the L1P code stream.

[0071] Specifically, the L1P accumulator unit synchronously receives three core inputs: the Q-branch signal separated and output by the code stream extraction module, the L1P subcarrier sequence generated by the L1P subcarrier unit, and the L1P chip overflow pulse output by the L1CA20 code unit. Within each signal sampling period, the L1P accumulator unit first performs a multiplication operation between the synchronously acquired Q-branch signal sampling data and the corresponding L1P subcarrier sequence, and then continuously coherently accumulates the result within a preset L1P chip length. This accumulation length is perfectly matched with the L1P signal's 10.23MHz code rate and strictly aligned with the trigger period of the L1P chip overflow pulse, which can maximize the coherent accumulation gain of the L1P target component. When the L1P chip overflow pulse is valid, it signifies the completion of the coherent accumulation operation for the current L1P chip cycle. If the L1P chip overflow pulse aligns with the L1P chip of the satellite signal, it indicates that the local timing, subcarrier sequence, and L1P signal transmitted by the satellite are completely synchronized. Within this accumulation cycle, the BOC-modulated subcarrier of the L1M component and the L1P subcarrier sequence satisfy the time-domain orthogonality characteristic. The multiplication result of the L1M component completely cancels out the positive and negative values ​​within the accumulation cycle, resulting in a final accumulation value of 0. Only the coherent accumulation result of the L1P target component is retained. The L1P accumulation unit then determines the polarity of the corresponding L1P chip based on the sign of the accumulation result, completing the extraction and output of one L1P chip. Simultaneously, it automatically resets the accumulator value to its initial state, preparing for the coherent accumulation operation of the next L1P chip cycle. Through the above cyclic process, the L1P accumulation unit achieves continuous and stable output of the L1P code stream. Figure 9 The diagram shown is a constellation diagram of the L1P bitstream extraction. The Q branch of the constellation is the L1P component, and the I branch is the L1CA component.

[0072] In this embodiment, in step S5, based on the L1M chip overflow pulse and the time-domain orthogonal separation strategy, the L1M accumulation unit performs coherent accumulation processing on the Q-branch signal and the L1M subcarrier sequence, and outputs the L1M code stream.

[0073] Specifically, the L1M accumulator unit synchronously receives three core inputs: the Q-branch signal separated and output by the code stream extraction module, the L1M subcarrier sequence generated by the L1M subcarrier unit, and the L1M chip overflow pulse output by the L1CA20 code unit. Within each signal sampling period, the L1M accumulator unit first performs a multiplication operation between the synchronously acquired Q-branch signal sampling data and the corresponding L1M subcarrier sequence, and then continuously coherently accumulates the result within a preset L1M chip length. This accumulation length perfectly matches the 5.115MHz code rate of the L1M signal, corresponds exactly to two L1P chip lengths, and is strictly aligned with the trigger period of the L1M chip overflow pulse. This adapts to the subcarrier periodic characteristics of the L1M signal BOC(10,5) modulation, maximizing the coherent accumulation gain of the L1M target component. When the L1M chip overflow pulse is valid, it signifies the completion of the coherent accumulation operation for the current L1M chip cycle. If the L1M chip overflow pulse aligns with the L1M chip of the satellite signal, it indicates that the local timing, subcarrier sequence, and L1M signal transmitted by the satellite are completely synchronized. Within this accumulation cycle, the subcarrier of the L1P component and the L1M subcarrier sequence satisfy the time-domain orthogonality characteristic. The positive and negative values ​​of the L1P component multiplication result completely cancel each other out within the accumulation cycle, resulting in a final accumulation value of 0. Only the coherent accumulation result of the L1M target component is retained. The L1M accumulation unit then determines the polarity of the corresponding L1M chip based on the sign of the accumulation result, completing the extraction and output of one L1M chip. Simultaneously, it automatically resets the accumulator value to its initial state, preparing for the coherent accumulation operation of the next L1M chip cycle. Through the above cyclic process, the L1M accumulation unit achieves continuous and stable output of the L1M code stream, synchronously completing the crosstalk-free joint extraction of the two licensed code streams with step S4. Figure 10 The diagram shown is a constellation diagram for L1M bitstream extraction. The Q branch of the constellation represents the L1M component, and the I branch represents the L1CA and intermodulation synthesis components.

[0074] The application scenarios of this invention are as follows: In aerospace satellite telemetry and control scenarios, this invention can simultaneously extract the L1P and L1M licensed code streams of GPS BLOCK II satellites, providing a stable navigation signal data source for spacecraft orbit measurement and attitude stabilization control, and is adapted to the high reliability and long-term continuous operation requirements of aerospace telemetry and control equipment.

[0075] In the research and development and manufacturing of special navigation terminals, this invention uses the L1CA signal as a single tracking anchor point to complete the extraction of dual-licensed code streams. It eliminates the need to build multiple independent signal tracking loops, which simplifies the terminal hardware architecture, reduces the consumption of device computing resources, and adapts to the design requirements of miniaturized and low-power navigation terminals.

[0076] In satellite navigation signal monitoring and analysis scenarios, this invention can achieve crosstalk-free separation and extraction of L1P and L1M licensed code streams, providing a clean code stream data source for navigation signal quality assessment, satellite on-orbit operational status monitoring, and wireless channel characteristic analysis, thus supporting the stable operation of ground navigation signal monitoring systems.

[0077] In emergency rescue and special field operations scenarios, this invention can stably extract two authorized code streams under complex electromagnetic environments and weak signal reception conditions, providing reliable navigation signal support for field operation equipment and emergency rescue navigation terminals, and adapting to navigation and positioning needs in complex environments.

[0078] In shipborne and vehicle-mounted special navigation equipment applications, this invention achieves synchronous extraction of dual-authorized code streams through parallel coherent accumulation processing, eliminating the need to serially execute multiple code stream extraction processes, thereby improving the efficiency of navigation data updates and adapting to the real-time navigation operation requirements of high-speed mobile carriers.

[0079] In the research scenario of navigation signal anti-interference technology, this invention extracts the authorized code stream based on the time-domain orthogonal separation strategy, which can avoid the signal distortion problem caused by frequency domain filtering and provide stable code stream extraction technology support for navigation anti-interference algorithm verification and anti-interference terminal development.

[0080] It should be noted that the present invention has been described in a relatively specific and detailed manner above through general descriptions and specific embodiments. It should be understood that, based on the technical concept of the present invention, several conventional adjustments or further innovations can be made to these specific embodiments; however, as long as they do not depart from the technical concept of the present invention, the technical solutions obtained by these conventional adjustments or further innovations also fall within the protection scope of the claims of the present invention.

Claims

1. A device for jointly extracting L1P and L1M authorization codes of GPS BLOCK II satellites, characterized in that, It includes a signal tracking module and a code stream extraction module; the output of the signal tracking module is connected to the input of the code stream extraction module; the signal tracking module is used to track the L1CA signal of GPS satellites and outputs the baseband complex signal after carrier stripping; based on the baseband complex signal, the code stream extraction module extracts the L1P code stream and L1M code stream from the GPS BLOCK II satellite signal through a time-domain orthogonal separation strategy; The signal tracking module includes a carrier unit, a mixer unit, an accumulator unit, and a loop control unit; the output of the carrier unit is connected to the input of the mixer unit; the output of the mixer unit is connected to the input of the accumulator unit; the output of the accumulator unit is connected to the input of the loop control unit; and the output of the loop control unit is connected to the input of the carrier unit. The code stream extraction module includes an L1CA20 code unit, an L1P subcarrier unit, an L1P accumulation unit, an L1M subcarrier unit, and an L1M accumulation unit. The first output terminal of the L1CA20 code unit is connected to the signal tracking module and is used to transmit the local L1CA early / late code. The second to fifth output terminals of the L1CA20 code unit are respectively connected to the control terminals of the L1P subcarrier unit, the L1P accumulation unit, the L1M subcarrier unit, and the L1M accumulation unit, and are used to transmit the L1P subcarrier address, L1P chip overflow pulse, L1M subcarrier address, and L1M chip overflow pulse, respectively. The output terminal of the L1P subcarrier unit is connected to the first input terminal of the L1P accumulation unit. The output terminal of the L1M subcarrier unit is connected to the first input terminal of the L1M accumulator unit; The output terminal of the signal tracking module is connected to the second input terminal of the L1P accumulator unit and the L1M accumulator unit, respectively, for transmitting the baseband complex signal.

2. The GPS BLOCK II satellite L1P and L1M license code joint extraction device according to claim 1, characterized in that, The carrier unit is used to generate an intermediate frequency carrier signal that matches the intermediate frequency signal at the L1 frequency point of the GPS BLOCK II satellite; the mixing unit is used to mix the input intermediate frequency signal with the intermediate frequency carrier signal, remove the carrier component, and generate a mixed signal. The accumulation unit is used to accumulate the mixed signal and generate an accumulation result; The loop control unit is used to adjust the carrier signal parameters of the carrier unit based on the feedback of the accumulation processing result, so as to achieve tracking of the L1CA signal.

3. The GPS BLOCK II satellite L1P and L1M authorization code joint extraction device according to claim 2, characterized in that, The L1CA20 code unit is used to generate a BPSK(20) modulated L1CA20 code stream with a reference rate of 20.46MHz. The L1CA20 code unit generates and outputs the L1P subcarrier address, the L1P chip overflow pulse, the L1M subcarrier address, and the L1M chip overflow pulse by performing chip counting on the L1CA20 code stream and performing modulo 2 and modulo 4 operations, respectively.

4. The GPS BLOCK II satellite L1P and L1M license code joint extraction device according to claim 3, characterized in that, The L1P subcarrier unit is a single-input lookup table structure, and the internal element sequence is [1 1]; Based on the L1P subcarrier address, the L1P subcarrier sequence is extracted through the L1P subcarrier unit to generate the L1P code stream; the L1M subcarrier unit is a two-input lookup table structure, and the element sequence stored internally is [-1 1-1 1]. Based on the L1M subcarrier address, the L1M subcarrier sequence is extracted through the L1M subcarrier unit to generate the L1M code stream.

5. The GPS BLOCK II satellite L1P and L1M license code joint extraction device according to claim 4, characterized in that, The L1P accumulation unit is used to coherently accumulate the Q-branch data of the baseband complex signal with the L1P subcarrier sequence, and the accumulation length is one L1P chip length. When the L1P chip overflow pulse is valid, the L1P accumulation unit resets the coherent accumulation value and outputs the L1P code stream. When the L1P chip overflow pulse is aligned with the L1P chip of the satellite signal, the L1M component accumulation value is 0. The L1M accumulation unit is used to coherently accumulate the Q-branch data of the baseband complex signal with the L1M subcarrier sequence, and the accumulation length is one L1M chip length. When the L1M chip overflow pulse is valid, the L1M accumulation unit resets the coherent accumulation value and outputs the L1M code stream, and when the L1M chip overflow pulse is aligned with the satellite signal L1M chip, the L1P component accumulation value is 0.

6. A method for jointly extracting L1P and L1M authorization codes of GPS BLOCK II satellites, characterized in that, include: The signal tracking module receives the intermediate frequency signal at the L1 frequency point of the GPS BLOCK II satellite; The carrier unit in the signal tracking module generates an intermediate frequency carrier signal that matches the intermediate frequency signal; The mixing unit performs mixing processing on the intermediate frequency signal and the intermediate frequency carrier signal, initially stripping away the carrier component to obtain the mixed signal; The accumulator unit performs accumulator processing on the mixed signal to generate a tracking feedback reference signal; the loop control unit outputs an adjustment command based on the tracking feedback reference signal; the carrier unit adjusts the parameters of the intermediate frequency carrier signal according to the adjustment command to track the L1CA signal in the intermediate frequency signal and complete the carrier component stripping to generate a baseband complex signal. The signal tracking module outputs the baseband complex signal to the code stream extraction module; The code stream extraction module separates the baseband complex signal to obtain a Q-branch signal containing L1P and L1M components; the L1CA20 code unit in the code stream extraction module is based on the BPSK(20) modulation rule to convert the GPS satellite L1CA signal into a BPSK(20) modulated signal and generate an L1CA20 code stream. Based on the L1CA20 code stream, a local L1CA early / late code is generated and transmitted to the signal tracking module; Based on the L1CA20 code stream, the L1CA20 code unit transmits the L1P subcarrier address, L1P chip overflow pulse, L1M subcarrier address and L1M chip overflow pulse to the L1P subcarrier unit, L1P accumulation unit, L1M subcarrier unit and L1M accumulation unit respectively. The L1P subcarrier unit generates an L1P subcarrier sequence based on the L1P subcarrier address; The L1M subcarrier unit generates an L1M subcarrier sequence based on the L1M subcarrier address; Based on the L1P chip overflow pulse and time-domain orthogonal separation strategy, the L1P accumulation unit performs coherent accumulation processing on the Q-branch signal and the L1P subcarrier sequence to output the L1P code stream. Based on the L1M chip overflow pulse and the time-domain orthogonal separation strategy, the L1M accumulation unit performs coherent accumulation processing on the Q-branch signal and the L1M subcarrier sequence, and outputs the L1M code stream.

7. The method for jointly extracting GPS BLOCK II satellite L1P and L1M authorization codes according to claim 6, characterized in that, The expression for the intermediate frequency signal received by the signal tracking module is: In the formula, It is an intermediate frequency signal; t For time; For L1P signal power, For L1P components; This refers to the L1M signal power. For L1M components; For subcarrier; The power of the L1CA component; For L1CA components; The intermediate frequency carrier frequency; The initial phase of the intermediate frequency carrier is unknown; For noise; For intermodulation components; The expression for the baseband complex signal is: In the formula, It is a baseband complex signal; j The imaginary unit; It is complex noise.

8. The method for jointly extracting GPS BLOCK II satellite L1P and L1M authorization codes according to claim 7, characterized in that, The L1CA20 code unit repeats each chip of the L1CA signal 20 times to generate the L1CA20 code stream with a reference rate of 20.46MHz; the local L1CA early and late code spacing is configured to be 1 / 8 chip. The L1CA20 code unit generates the L1P subcarrier address, the L1P chip overflow pulse, the L1M subcarrier address, and the L1M chip overflow pulse by counting chips in the L1CA20 code stream and performing modulo-2 and modulo-4 operations, respectively. One L1CA chip length corresponds to 20 subcarrier half-cycle lengths, 10 L1P chip lengths, and 5 L1M chip lengths. The L1P component code rate is 10.23MHz, the L1M component code rate is 5.115MHz, the L1CA component code rate is 1.023MHz, and the subcarrier frequency is 10.23MHz.

9. The method for jointly extracting GPS BLOCK II satellite L1P and L1M authorization codes according to claim 8, characterized in that, The L1P subcarrier unit is a single-input lookup table structure, and the element sequence in the lookup table is [1 1]; the expression for the coherent accumulation value of the Q-branch signal and the L1P subcarrier sequence in the L1P accumulator unit is: In the formula, The coherent cumulative integration interval extracted from the L1P bitstream; This refers to the Q-branch component of the baseband complex signal; The local subcarrier sequence is used for L1P code stream extraction.

10. A method for jointly extracting L1P and L1M authorization codes of GPS BLOCK II satellites according to claim 9, characterized in that, The L1M subcarrier unit has a two-input lookup table structure, and the element sequence in the lookup table is [-1 1-1 1]; the expression for the coherent accumulation value of the Q-branch signal and the L1M subcarrier sequence in the L1M accumulator unit is: In the formula, Local subcarrier sequence for L1M bitstream extraction; Matched subcarrier sequence for L1M code stream extraction.

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