A method and apparatus for secure isolation of satellite navigation signals

Abstract

The application discloses a kind of satellite navigation signal security isolation method and device.The isolation method includes satellite navigation receiving antenna simultaneously receiving multiple satellite navigation signals from different navigation satellites, by isolating device, these satellite navigation signals are respectively demodulated received, and using receiving information real-time recovery regenerates corresponding regenerative navigation signal, while detecting these satellite navigation signals, find any satellite navigation signal as spoofing signal, then block corresponding regenerative navigation signal output, while satellite navigation signal detected as real signal, corresponding regenerative navigation signal is combined and output to the satellite navigation receiving equipment protected.The method and device are not only beneficial to accurate isolation spoofing satellite navigation signal, but also beneficial to maintain the continuity and accuracy of real satellite navigation signal reception, realize the effective unity of satellite navigation signal detection, spoofing signal blocking isolation and uninterrupted reception of real signal.

Description

Technical Field

[0001] This invention relates to the field of satellite navigation technology, and in particular to a method and apparatus for secure isolation of satellite navigation signals. Background Technology

[0002] In existing technologies, such as Figure 1 The satellite navigation receiving antenna 2 shown can typically receive satellite navigation signals from multiple satellites 1 simultaneously. After these different satellite navigation signals are received by the antenna 2, they are transmitted to the satellite navigation receiving device 3 at the back end for demodulation and calculation, and the corresponding accurate positioning, speed or timing information is obtained.

[0003] In practical applications, malicious attempts may arise to generate false satellite navigation signals, impersonating genuine signals from actual satellites to deceive the system and cause errors in positioning, speed, or timing results. Currently, existing navigation terminals and timing devices typically lack anti-spoofing capabilities. Even for devices equipped with spoofing detection functions, detecting a spoofing signal usually results in stopping reception or cutting off signal transmission to the downstream satellite navigation receiver, leading to reception interruption. Therefore, effectively isolating and blocking spoofing signals without affecting the downstream satellite navigation receiver's ability to continue receiving genuine satellite navigation signals from other satellites has become a significant technical challenge in engineering practice. Summary of the Invention

[0004] The main technical problem solved by this invention is to provide a secure isolation method and device for satellite navigation signals, which solves the problem in the prior art that spoofing signals cannot be blocked and isolated separately, and does not affect the normal reception of other real satellite navigation signals by the back-end receiving equipment after passing through the isolation device.

[0005] To address the aforementioned technical problems, one technical solution adopted by this invention is to provide a satellite navigation signal security isolation method. This method involves setting up an isolation device between a satellite navigation receiving antenna and a satellite navigation receiving device, and further includes: Step 1, where the satellite navigation receiving antenna simultaneously receives satellite navigation signals from different navigation satellites, from the 1st to the Nth satellite navigation signals, where N is the maximum value of the simultaneously received satellite navigation signals; Step 2, where the isolation device demodulates and receives the 1st to the Nth satellite navigation signals respectively, and uses the received information to recover and regenerate the corresponding 1st to the Nth regenerated navigation signals in real time; Step 3, where the 1st to the Nth satellite navigation signals are simultaneously detected. If any satellite navigation signal is found to be a spoofing signal, the corresponding regenerated navigation signal output is blocked. Simultaneously, for satellite navigation signals detected as genuine signals, the corresponding regenerated navigation signals are combined and output to the satellite navigation receiving device.

[0006] Preferably, the first to Nth satellite navigation signals belong to the same satellite navigation system and coexist in code division multiple access mode, and have the same nominal carrier frequency.

[0007] Preferably, a portion of the first to Nth satellite navigation signals belong to signals coexisting in the first satellite navigation system using code division multiple access and have the same first nominal carrier frequency. Another portion of the first to Nth satellite navigation signals belong to signals coexisting in the second satellite navigation system using code division multiple access and have the same second nominal carrier frequency. The first and second nominal carrier frequencies are close but not the same.

[0008] Preferably, in step two, the isolation device demodulates, receives, and regenerates multiple satellite navigation signals included in the first satellite navigation system and multiple satellite navigation signals included in the second satellite navigation system, respectively; in step three, each satellite navigation signal is also detected, and the output of the regenerated navigation signal corresponding to the spoofing signal is blocked, and the regenerated navigation signal corresponding to the real signal is combined and output to the satellite navigation receiving device.

[0009] Preferably, in step two, the demodulation reception includes real-time carrier tracking, despreading, and demodulation processing of the satellite navigation signal, and the received information includes reproducing the coherent carrier, reproducing the PN code, and reproducing the navigation message.

[0010] Preferably, the recovery and regeneration includes spreading modulation of the regenerated navigation data based on the regenerated navigation message using the regenerated PN code, and further carrier modulation of the spread modulation result using the regenerated coherent carrier to obtain the corresponding regenerated navigation signal.

[0011] Preferably, before demodulating and receiving each of the satellite navigation signals, each of the satellite navigation signals is uniformly down-converted and AD sampled; and after the regenerated navigation signals that are detected as corresponding to the real signals are combined, they are subjected to DA conversion and up-conversion before being transmitted to the satellite navigation receiving device.

[0012] This invention also discloses a satellite navigation signal security isolation device, including an input interface and an output interface, comprising multiple parallelly arranged first to Lth receiving and regenerating units, where L is greater than or equal to the maximum value of the multiple satellite navigation signals received simultaneously; the input interface is connected to the input terminal of each receiving and regenerating unit, and the output interface is connected to the output terminal of each receiving and regenerating unit respectively via first to Lth detection and control switches; each receiving and regenerating unit includes a receiving subunit and a regenerating subunit, respectively used to receive and demodulate the input satellite navigation signal, and to recover and generate the corresponding regenerated navigation signal using the reconstructed coherent carrier, reconstructed PN code, and reconstructed navigation message generated during the receiving and demodulation; the output terminal of each receiving and regenerating unit is also controlled by a corresponding detection and control switch, wherein if the satellite navigation signal received by the receiving and regenerating unit is detected as a spoofing signal, the corresponding detection and control switch is turned off, and if the satellite navigation signal received by the receiving and regenerating unit is detected as a genuine signal, the corresponding detection and control switch is turned on.

[0013] Preferably, the receiving subunit includes a mixer, a local carrier generator, a despreader, a delay locker, and a demodulator. After the satellite navigation signal enters the mixer, it is mixed with the reproducible coherent carrier output by the local carrier generator to obtain a baseband signal. Then, the despreader despreads the baseband signal using the reproducible PN code output by the delay locker. The despreaded timely branch is input to the demodulator for demodulation to obtain the reproducible navigation message. The despreaded advance and lag branches are input to the delay locker for spreading code synchronization tracking. The reproducible PN code and reproducible data clock are sent to the receiver and demodulator. The regenerating subunit includes a carrier modulator, a spread spectrum modulator, and a regenerating navigation data buffer. The reproducible navigation message generated by the demodulator is input to the regenerating navigation data buffer for buffering and processing to obtain regenerating navigation data. Then, the reproducible PN code is used to spread spectrum modulate the regenerating navigation data through the spread spectrum modulator. Finally, the reproducible coherent carrier is used to carrier modulate the spread spectrum modulation result to obtain the corresponding regenerating navigation signal.

[0014] Preferably, a downconverter and an AD sampler are connected in series before the first receiving and regenerating unit to the Lth receiving and regenerating unit, and a shared DA converter, upconverter and power regulator are connected in series thereafter.

[0015] The beneficial effects of this invention are as follows: This invention discloses a method and apparatus for secure isolation of satellite navigation signals. The isolation method includes a satellite navigation receiving antenna simultaneously receiving multiple satellite navigation signals from different navigation satellites. An isolation device demodulates and receives these satellite navigation signals separately, reconstructing multiple corresponding regenerated navigation signals. Simultaneously, these satellite navigation signals are detected; if any satellite navigation signal is found to be a spoofing signal, the corresponding regenerated navigation signal output is blocked. For satellite navigation signals detected as genuine signals, the corresponding regenerated navigation signals are combined and output to the satellite navigation receiving device. This method and apparatus not only facilitate accurate isolation of spoofing satellite navigation signals but also help maintain the continuity and accuracy of receiving genuine satellite navigation signals, achieving an effective unification of blocking and isolating spoofing satellite navigation signals and uninterrupted reception of genuine signals. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the principle of satellite navigation signal transmission and reception in existing technologies;

[0017] Figure 2 This is a schematic diagram illustrating the composition principle of an embodiment of the satellite navigation signal security isolation method according to the present invention;

[0018] Figure 3 This is a flowchart of an embodiment of a satellite navigation signal security isolation method according to the present invention;

[0019] Figure 4 This is a schematic diagram illustrating the composition of an embodiment of a satellite navigation signal security isolation device according to the present invention;

[0020] Figure 5 This is a schematic diagram of the composition of the receiving and regenerating unit in an embodiment of the satellite navigation signal security isolation device according to the present invention;

[0021] Figure 6 This is a schematic diagram illustrating the composition of an embodiment of a satellite navigation signal security isolation device according to the present invention. Detailed Implementation

[0022] To facilitate understanding of the present invention, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0023] It should be noted that, unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0024] exist Figure 1 Based on the existing technical embodiments shown, Figure 2 It is shown that an isolation device 4 is also provided between the satellite navigation receiving antenna 2 and the satellite navigation receiving device 3. This isolation device is used to detect and identify whether there is a spoofing signal among the multiple satellite navigation signals received by the satellite navigation receiving antenna 2 (signals within the frequency range received by the antenna by default are satellite navigation signals). If there is a spoofing signal, the signal needs to be isolated to prevent it from entering the back-end satellite navigation receiving device 3. At the same time, other non-spoofing real satellite navigation signals can be transmitted normally to the back-end satellite navigation receiving device 4.

[0025] Figure 3 The flowchart illustrates an embodiment of a satellite navigation signal security isolation method according to the present invention, wherein an isolation device is provided between the satellite navigation receiving antenna and the satellite navigation receiving device, including the following steps:

[0026] S1: Step 1, the satellite navigation receiving antenna simultaneously receives the first to Nth satellite navigation signals from different navigation satellites. N is the signal received by the antenna simultaneously, which by default is the maximum value of all satellite navigation signals (including deceptive signals and real signals). Preferably, N is greater than or equal to 4, because at least 4 satellites are needed to accurately complete the positioning.

[0027] S2: Step two, the isolation device demodulates and receives the first to Nth satellite navigation signals respectively, and recovers the corresponding first to Nth regenerated navigation signals;

[0028] S3: Step 3, simultaneously detect the first to Nth satellite navigation signals. If any satellite navigation signal is found to be a spoofing signal, block the output of the corresponding regenerated navigation signal, and combine the detected genuine satellite navigation signals and output them to the satellite navigation receiving device.

[0029] exist Figure 3In the illustrated embodiment, it is possible to detect and identify multiple satellite navigation signals, as well as regenerate and recover multiple satellite navigation signals. Furthermore, the regenerated and recovered navigation signals are recovered through real-time demodulation, thereby ensuring that the regenerated and recovered navigation signals have a high degree of consistency and real-time performance with the satellite navigation signals received by the antenna, thus ensuring the reliability of receiving real satellite navigation signals.

[0030] Furthermore, demodulation reception is beneficial for analyzing the signal characteristics of the received satellite navigation signals, such as power and carrier. These are typically direct sequence spread spectrum signals, including PN code type, PN code phase, spread spectrum code clock period, and data clock period. Here, "data" refers to data that has been spread spectrum modulated by the spread spectrum code, so the data clock period is usually an integer multiple of the spread spectrum code clock period. Based on the information characteristics of the received satellite navigation signals (such as the navigation message content contained in the data), single feature detection can be performed on each satellite navigation signal to determine if it is a deceptive signal, and / or comprehensive feature detection can be performed on each satellite navigation signal to determine if it is a deceptive signal. Additionally, by comparing the detection features of multiple satellite navigation signals, the authenticity of a particular signal can be further verified.

[0031] This allows for the identification and detection of each received satellite navigation signal. When a spoofed signal is detected, it can be precisely isolated and blocked, meaning only the regenerated navigation signal corresponding to the spoofed signal is isolated. This prevents the spoofed signal from reaching the downstream satellite navigation receiver, ensuring that the regenerated navigation signals input to the receiver correspond to genuine satellite navigation signals. This guarantees the continuity of the receiver's reception of genuine satellite navigation signals and improves its security.

[0032] Preferably, the different navigation satellites mentioned in step S1 include multiple different navigation satellites of the same satellite navigation system, such as multiple navigation satellites corresponding to the BeiDou Navigation Satellite System or multiple navigation satellites corresponding to the GPS system; or they can be multiple different navigation satellites of different satellite navigation systems, such as different satellites of both the BeiDou Navigation Satellite System and the GPS Navigation Satellite System. For example, the center frequency of the B1 band of the BeiDou Navigation Satellite System is 1561.098MHz, and the center frequency of the L1 band of the GPS system is 1575.42MHz. Although these two frequency points belong to two different satellite navigation systems, because the frequencies are relatively close and the corresponding spread spectrum signals occupy a large degree of overlap in frequency range, the satellite navigation receiving antenna can receive them together.

[0033] Therefore, when multiple different navigation satellites belonging to different satellite navigation systems are simultaneously received by the satellite navigation receiving antenna, the isolation method and isolation device of the present invention can simultaneously detect, identify, isolate and block multiple modes of satellite navigation signals, thereby enhancing the versatility and efficiency of its application.

[0034] Preferably, the first to Nth satellite navigation signals belong to the same satellite navigation system and coexist in a code division multiple access manner (distinguished by different spreading codes, address codes, or ranging codes), and have the same nominal carrier frequency.

[0035] Preferably, a portion of the first to Nth satellite navigation signals belong to signals coexisting in the first satellite navigation system using code division multiple access (CDMA) and have the same first nominal carrier frequency; another portion of the first to Nth satellite navigation signals belong to signals coexisting in the second satellite navigation system using CDMA and have the same second nominal carrier frequency; wherein the first and second nominal carrier frequencies are close but not the same, and the spreading code types used in the CDMA in the two satellite navigation systems are also different. Typically, the first and second nominal carrier frequencies belong to the same frequency band; for example, the aforementioned B1 and L1 frequencies both belong to the L band, and the spectral width occupied by the spread spectrum signals is also similar.

[0036] Correspondingly, in step two (S2), the isolation device demodulates, receives, and regenerates multiple satellite navigation signals included in the first satellite navigation system and multiple satellite navigation signals included in the second satellite navigation system, respectively. In step three (S3), each satellite navigation signal is also detected, and the regenerated navigation signal output corresponding to the spoofing signal is blocked. The regenerated navigation signal corresponding to the real signal is then combined and output to the satellite navigation receiving device. Therefore, this invention can simultaneously receive and separately detect and isolate satellite navigation signals from two different satellite navigation systems within the same isolation device, which is beneficial for intensive processing.

[0037] Preferably, in step S2, the isolation device includes multiple receiving and regenerating units to demodulate, receive, and regenerate the first to Nth satellite navigation signals, respectively. Preferably, as... Figure 4 As shown, it includes the first to the Lth receiving and regenerating units, wherein the number L of these receiving and regenerating units is greater than or equal to the maximum number N of satellite navigation signals received simultaneously.

[0038] Preferably, since navigation satellites are typically numerous and usually orbit the Earth, the number of satellites passing overhead is fixed within a given timeframe, but their positions are constantly changing. In another timeframe, some passing satellites will leave the receiving area's field of view, while new passing satellites will enter. Therefore, the isolation device can predict the satellite navigation signals transmitted by passing navigation satellites during different operating periods based on its geographical location. The isolation device can then adjust the number of satellite navigation signals received from the first to the Nth satellite and the corresponding reception parameters in real time. In this way, the isolation device can adjust the operating parameters (including frequency, PN code, etc.) and operating status (start working, stop working, spreading code acquisition, spreading code tracking, etc.) of each receiving and regenerating unit in real time according to the passing satellite situation, automatically adapting to changes in satellite operation.

[0039] Preferably, each receiving and regenerating unit first demodulates and receives the corresponding satellite navigation signal to obtain real-time carrier information, coherent spreading code information, and navigation message information for real-time dynamic tracking of the satellite navigation signal. Then, based on the real-time carrier information and coherent spreading code information, the navigation message information is modulated to recover and generate the corresponding regenerated navigation signal.

[0040] For example, the BeiDou Regional Navigation Satellite System broadcasts five navigation signals on three L-bands (B1, B2, and B3) to provide public and licensed services. The carrier frequencies of B1, B2, and B3 are 1561.098MHz, 1207.140MHz, and 1268.520MHz, respectively. All signals use QPSK modulation. There are two B1 channels: the in-phase component B1I and the quadrature-phase component B1Q. B1I provides open services, and B1Q provides licensed services. Taking the B1 signal as an example, it consists of a QPSK signal composed of two independent quadrature BPSK channels. The B1 signal can be represented as:

[0041]

[0042] Where the superscript j is the satellite number, indicating that it comes from different satellites, and the parameters (i.e., the received information) include: and These represent the amplitudes of the in-phase component and the quadrature component, respectively. and These represent the ranging code or spreading code for the in-phase component and the quadrature component, respectively. and The data representing the in-phase and quadrature components are respectively contained within the navigation message. (f1) j It is the real-time carrier frequency of the B1 frequency point. and These are the initial phases of the real-time carriers of the in-phase and quadrature components at frequency B1, respectively.

[0043] After being demodulated and received by the receiving and regenerating unit, these parameters (i.e., the received information) can be obtained in real time. Then, the parameters obtained in real time are used to remodulate and obtain the corresponding regenerated navigation signal, that is:

[0044]

[0045] in, and These represent the amplitudes of the in-phase and quadrature components of the regenerated system, respectively. and These represent the ranging code or spreading code for the regenerated in-phase and quadrature components, respectively. and These represent the data for the regenerated in-phase and quadrature components, respectively. It is the regenerated carrier frequency of the B1 frequency point. and These are the initial carrier phases of the in-phase and quadrature components regenerated at frequency B1, respectively. In principle, these regenerated parameters...

[0046]

[0047] Parameters of the received satellite navigation signals They are exactly the same, but the difference in actual application is that there is a time delay in the process of receiving and regenerating. Therefore, it lags behind the satellite navigation signal in time. However, this lag is relatively fixed and predictable, and the regenerated navigation signal does not affect the normal reception of the backend equipment.

[0048] Preferred, such as Figure 4 As shown, the regenerated navigation signal output by each receiving and regenerating unit is controlled by a corresponding detection control signal. For example, the output of the first receiving and regenerating unit is controlled by the first detection control signal, which in turn controls the opening or closing of the first detection control switch. These detection control signals originate from the synchronous detection of the first to Nth satellite navigation signals in step three to detect and identify whether there are spoofing signals. When any satellite navigation signal is detected as a spoofing signal, the corresponding detection control signal will control the disconnection and isolation of the corresponding regenerated navigation signal output. Under normal circumstances, if any satellite navigation signal is considered to be a genuine signal, the corresponding detection control signal will maintain the corresponding regenerated navigation signal output.

[0049] There are various ways to detect satellite navigation signals. This can be done by detecting signal characteristics, such as signal power and carrier frequency offset, or by detecting information characteristics, such as the authenticity of navigation messages. This can be done by detecting a single satellite navigation signal and determining whether it is a deceptive signal, or by comprehensively detecting multiple satellite navigation signals and identifying one of them as a deceptive signal. Therefore, the isolation device in this invention can include various different satellite navigation signal detection and identification methods, thereby generating detection control signals to control the on / off output of the regenerated navigation signal.

[0050] Preferably, conventional detection and identification methods utilize comparisons of positioning results or clock biases from different frequency points or navigation systems to identify deceptive signals. However, such schemes have significant vulnerabilities; if all frequency points exhibit deceptive interference signals, identification becomes impossible. Preferably, this invention detects the presence of suppression interference after the isolation device is powered on. If a situation exists that completely suppresses the real signal, an alarm is triggered directly, focusing only on satellite navigation signal acquisition and tracking without PVT calculation to avoid being deceived. If no suppression interference is detected, the deceptive detection method includes: a full search of the time and frequency domains for each satellite acquisition; when multiple correlation peaks are detected, multiple correlation peaks are submitted for tracking and multi-peak detection; the carrier-to-noise ratio combined with the noise floor is used to detect abnormal signal power; PVT is performed using the data observed per second to obtain the clock bias and frequency bias of the local rubidium clock in real time, followed by discipline and output of time and frequency, prediction of clock bias changes, and verification of the current clock bias. This multi-faceted approach significantly improves the probability of detecting deceptive interference.

[0051] Preferred, such as Figure 5 The diagram illustrates an embodiment of the internal structure of a receiver-regenerator unit Z1, which includes a receiver subunit Z11 and a regenerator subunit Z12, used for receiving the input satellite navigation signal and recovering the regenerated navigation signal, respectively. Preferably, the receiver subunit Z11 includes mixing, despreading, and demodulation processing. The mixing process involves mixing the carrier of the input satellite navigation signal (specifically, it can be implemented as a quadrature two-path complex frequency conversion) to obtain a baseband signal with a carrier frequency of zero. Since the carrier of the satellite navigation signal is affected by the Doppler effect, there will be a deviation between it and its nominal frequency. Therefore, it is necessary to continuously track the carrier changes of the satellite navigation signal during the reception process.

[0052] Preferably, in the mixing process, the local carrier, i.e. the reproducible coherent carrier generated by the receiving subunit, is used to perform mixing processing on the satellite navigation signal. The local carrier also receives the demodulation frequency generated from the demodulation process for correction and adjustment, thereby enabling real-time tracking of the carrier changes of the satellite navigation signal.

[0053] Preferably, after mixing, the satellite navigation signal undergoes despreading. The local reproducible PN code is used to despread the spreading code in the satellite navigation signal to recover the data. Therefore, the despreading process requires input of the locally generated reproducible PN code (including the reproducible PN code clock) and the reproducible data clock. The reproducible PN code and the reproducible data clock must have accurate phase alignment and be able to adjust and track the satellite navigation signal in real time. The despreading process outputs three despread signals: an early half-chip spread spectrum output (E branch or early branch output, i.e., Early), a late half-chip spread spectrum output (L branch or late branch output, i.e., Late), and a timely output (P branch or timely branch output, Prompt). The timely output is then demodulated in the demodulation loop to obtain the reproducible navigation message. The outputs of the E branch and the L branch enter the delay-locked loop for loop tracking and locking processing, respectively outputting the real-time tracking accurate reproduction PN code and reproduction data clock, which are used for despreading and demodulation processing.

[0054] Therefore, in step two, the demodulation reception includes real-time carrier tracking, despreading, and demodulation of the satellite navigation signal, which respectively yield the reconstructed coherent carrier, the reconstructed PN code, and the reconstructed navigation message.

[0055] Furthermore, in Figure 5 The receiving subunit Z11 has three outputs to the regenerating subunit Z12: a reconstructed coherent carrier, a reconstructed PN code, and a reconstructed data clock, all generated in real time during reception. The reconstructed coherent carrier is generated from the local carrier after demodulation and frequency correction. The reconstructed PN code is generated after delay-locking processing (including the PN code clock and dynamically changing code phase, and real-time PN code tracking of the satellite navigation signal). The reconstructed data clock is also generated after delay-locking processing (including the data clock and phase, and real-time data synchronization tracking of the satellite navigation signal).

[0056] In the regenerating subunit Z12, after the receiving subunit outputs the original data bits corresponding to the reconstructed navigation message, the data is buffered, then reframed according to the navigation message format, and the frame start phase is aligned with the satellite navigation system time phase before being sent out as the reconstructed navigation data. Then, spread spectrum modulation is performed using the reconstructed PN code, for example, by performing an XOR operation. The result after spread spectrum modulation is then carrier modulated using the reconstructed coherent carrier to generate the corresponding output reconstructed navigation signal.

[0057] Correspondingly, in step two, the recovery and regeneration includes spreading the regenerated navigation data using the reproduced PN code, and then using the reproduced coherent carrier to perform carrier modulation on the result of the spreading modulation to obtain the corresponding regenerated navigation signal.

[0058] Therefore, when the regenerating subunit Z12 regenerates navigation signals, it mainly utilizes the carrier wave, PN code, and data information generated in real time during the reception of satellite navigation signals. Then, it uses this information to complete the regeneration modulation. Thus, the recovered regenerated navigation signal not only has the same technical parameters and data information as the received satellite navigation signal, but also has time correlation, which can ensure the consistency and real-time performance of the regenerated navigation signal with the satellite navigation signal.

[0059] Furthermore, in Figure 4 Based on the illustrated embodiment, Figure 6 This further demonstrates a digital implementation of the isolation device. Figure 6 In the process, after entering the isolation device, the first step is to perform down-conversion processing. This is because the carrier frequencies of the multiple satellite navigation signals received by the satellite navigation receiving antenna are relatively high, such as the L-band frequency. Therefore, it is necessary to down-convert the carrier frequencies of these satellite navigation signals to a low-intermediate frequency, which is beneficial for reducing the sampling rate and digital processing.

[0060] Therefore, after down-conversion, AD sampling is performed to obtain multiple time-discrete satellite navigation signals, which are then fed into various receiving and regenerating units for digital reception and regeneration. Each receiving and regenerating unit, due to its different set receiving PN code, can filter and receive the satellite navigation signals it needs to receive and regenerate accordingly.

[0061] Simultaneously, these satellite navigation signals are also detected and identified. If any satellite navigation signal is found to be a spoofing signal, the corresponding regenerated navigation signal is isolated and blocked, while the regenerated navigation signals corresponding to other genuine satellite navigation signals are combined and output. After output, these digitized and combined regenerated navigation signals are first converted into analog combined regenerated navigation signals through DA conversion. Then, they undergo unified up-conversion processing to increase the carrier frequency of these combined regenerated navigation signals to be equal to the carrier frequency of the satellite navigation signals before the down-conversion processing before entering the isolation device. Therefore, this up-conversion processing corresponds to the previous down-conversion processing.

[0062] Preferably, the power of the combined regenerated navigation signal after up-conversion processing is further regulated so that the total power of the multiple output regenerated navigation signals is equal to the total power of the multiple satellite navigation signals entering the isolation device. Therefore, the combined regenerated navigation signal output by the isolation device is consistent with its corresponding satellite navigation signal in terms of carrier frequency, signal power, PN code, data, and modulation method for each regenerated navigation signal. This ensures that the combined regenerated navigation signal output by the isolation device is consistent with the multiple satellite navigation signals entering the isolation device. The main difference lies in detecting and isolating deceptive satellite navigation signals, ensuring that the signal entering the back-end receiving equipment is genuine.

[0063] Therefore, based on Figure 6 In the embodiment shown, before receiving and processing each of the satellite navigation signals, each of the satellite navigation signals is uniformly down-converted and AD sampled; and after the regenerated navigation signals that are detected as corresponding to the real signals are combined, they are subjected to DA conversion and up-conversion before being transmitted to the satellite navigation receiving device.

[0064] Based on the same concept, the present invention also provides a satellite navigation signal security isolation device, in conjunction with the foregoing, and with reference to Figures 4 to 6 As shown, the isolation device includes an input interface and an output interface, and also includes multiple parallel-arranged first to Lth receiving and regenerating units, where L is greater than or equal to the maximum value of the multiple satellite navigation signals received simultaneously; the input interface is connected to the input terminal of each receiving and regenerating unit, and the output interface is connected to the output terminal of each receiving and regenerating unit respectively through the first to Lth detection and control switches.

[0065] Each receiving and regenerating unit includes a receiving subunit and a regenerating subunit, which are respectively used to receive and demodulate the input satellite navigation signal, and to recover and generate the corresponding regenerated navigation signal using the reconstructed coherent carrier, reconstructed PN code, and reconstructed navigation message generated during the receiving and demodulation process.

[0066] The output of each receiving and regenerating unit is also controlled by a corresponding detection control switch. If the satellite navigation signal received by the receiving and regenerating unit is detected as a spoofing signal, the corresponding detection control switch is turned off; if the satellite navigation signal received by the receiving and regenerating unit is detected as a real signal, the corresponding detection control switch is turned on.

[0067] Preferred, based on Figure 5As shown, the receiving subunit includes a mixer, a local carrier generator, a despreader, a delay locker, and a demodulator. After the satellite navigation signal enters the mixer, it is mixed with the reproducible coherent carrier output by the local carrier generator to obtain the baseband signal. Then, the despreader despreads the baseband signal through the reproducible PN code output by the delay locker. The despread timely branch is input to the demodulator for demodulation to obtain the reproducible navigation message. The despread advance branch and lag branch are input to the delay locker for spreading code synchronization tracking. The reproducible PN code and reproducible data clock are output to the despreader and demodulator.

[0068] The regenerative subunit includes a carrier modulator, a spread spectrum modulator, and a regenerative navigation data buffer. The reconstructed navigation message, demodulated by the demodulator, is input to the regenerative navigation data buffer for processing and buffering. Its main function is to receive the original data bits of the navigation signal message, store them in the data buffer, reframe them according to the navigation message format, align the frame start phase with the satellite navigation system's time phase, and then transmit them. The spread spectrum modulator then performs spread spectrum modulation of the reconstructed PN code on the regenerative navigation data. Finally, the carrier modulator performs carrier modulation of the spread spectrum modulation result using the reconstructed coherent carrier to obtain the corresponding regenerative navigation signal.

[0069] Preferred, based on Figure 6 As shown, a common downconverter and AD sampler are connected in series before the first receiving and regenerating unit to the Lth receiving and regenerating unit, which are arranged in parallel, and a common DA converter, upconverter and power regulator are connected in series afterward.

[0070] For further explanation of the isolation device, please refer to the foregoing explanation of the isolation method, which will not be repeated here.

[0071] Therefore, this invention discloses a method and apparatus for secure isolation of satellite navigation signals. The isolation method includes a satellite navigation receiving antenna simultaneously receiving multiple satellite navigation signals from different navigation satellites. An isolation device demodulates and receives these satellite navigation signals separately, reconstructing multiple corresponding regenerated navigation signals. Simultaneously, these satellite navigation signals are detected; if any satellite navigation signal is found to be a deceptive signal, the corresponding regenerated navigation signal output is blocked. For satellite navigation signals detected as genuine signals, the corresponding regenerated navigation signals are combined and output to the satellite navigation receiving device. This method and apparatus not only facilitate accurate isolation of deceptive satellite navigation signals but also help maintain the continuity and accuracy of receiving genuine satellite navigation signals, achieving an effective unification of satellite navigation signal detection, deceptive signal blocking and isolation, and uninterrupted reception of genuine signals.

[0072] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for secure isolation of satellite navigation signals, characterized in that, The isolation device between the satellite navigation receiving antenna and the satellite navigation receiving equipment also includes: Step 1: The satellite navigation receiving antenna simultaneously receives satellite navigation signals from different navigation satellites, from the 1st to the Nth satellite navigation signals, where N is the maximum value of the satellite navigation signals received simultaneously. Step 2: The isolation device demodulates and receives the first to Nth satellite navigation signals respectively, and uses the received information to recover and regenerate the corresponding first to Nth regenerated navigation signals in real time. The demodulation reception includes real-time carrier tracking, despreading, and demodulation of the satellite navigation signal, and the received information includes reproducing the coherent carrier, reproducing the PN code, and reproducing the navigation message. The recovery and regeneration includes spreading the regenerated navigation data based on the regenerated navigation message using the regenerated PN code, and then using the regenerated coherent carrier to perform carrier modulation on the result of the spreading modulation to obtain the corresponding regenerated navigation signal. Step 3: Simultaneously detect the first to Nth satellite navigation signals. If any satellite navigation signal is found to be a spoofing signal, block the output of the corresponding regenerated navigation signal. At the same time, for satellite navigation signals detected as genuine signals, the corresponding regenerated navigation signals are combined and output to the satellite navigation receiving device.

2. The satellite navigation signal security isolation method according to claim 1, characterized in that, The first to Nth satellite navigation signals belong to the same satellite navigation system and coexist in code division multiple access mode, and have the same nominal carrier frequency.

3. The satellite navigation signal security isolation method according to claim 1, characterized in that, A portion of the first to Nth satellite navigation signals belong to signals coexisting in the first satellite navigation system using code division multiple access and have the same first nominal carrier frequency. Another portion of the first to Nth satellite navigation signals belong to signals coexisting in the second satellite navigation system using code division multiple access and have the same second nominal carrier frequency. The first and second nominal carrier frequencies are close but not the same.

4. The satellite navigation signal security isolation method according to claim 3, characterized in that, In step two, the isolation device performs demodulation reception and recovery / regeneration processing on multiple satellite navigation signals included in the first satellite navigation system and multiple satellite navigation signals included in the second satellite navigation system, respectively. In step three, each satellite navigation signal is also detected, and the output of the regenerated navigation signal corresponding to the spoofing signal is blocked. The regenerated navigation signal corresponding to the real signal is combined and output to the satellite navigation receiving device.

5. The satellite navigation signal security isolation method according to claim 1, characterized in that, Before demodulating and receiving each of the satellite navigation signals, each of the satellite navigation signals is uniformly down-converted and AD sampled; and after the regenerated navigation signals that are detected as real signals are combined, they are DA converted and up-converted before being transmitted to the satellite navigation receiving device.

6. A satellite navigation signal security isolation device, comprising an input interface and an output interface, characterized in that, It includes multiple parallel-configured first to Lth receiving and regenerating units, where L is greater than or equal to the maximum value of the multiple satellite navigation signals received simultaneously; the input interface is connected to the input terminal of each receiving and regenerating unit, and the output interface is connected to the output terminal of each receiving and regenerating unit respectively through the first to Lth detection and control switches. Each receiving and regenerating unit includes a receiving subunit and a regenerating subunit, which are respectively used to receive and demodulate the input satellite navigation signal, and to recover and generate the corresponding regenerated navigation signal using the reconstructed coherent carrier, reconstructed PN code, and reconstructed navigation message generated in the receiving and demodulation process; The output of each receiving and regenerating unit is also controlled by a corresponding detection control switch. If the satellite navigation signal received by the receiving and regenerating unit is detected as a spoofing signal, the corresponding detection control switch is turned off; if the satellite navigation signal received by the receiving and regenerating unit is detected as a real signal, the corresponding detection control switch is turned on.

7. The satellite navigation signal security isolation device according to claim 6, characterized in that, The receiving subunit includes a mixer, a local carrier generator, a despreader, a delay lockout, and a demodulator. After the satellite navigation signal enters the mixer, it is mixed with the reproducible coherent carrier output by the local carrier generator to obtain the baseband signal. Then, the despreader despreads the baseband signal through the reproducible PN code output by the delay lockout. The despreading timely branch is input to the demodulator for demodulation to obtain the reproducible navigation message. The despreading advance branch and lag branch are input to the delay locker for spreading code synchronization tracking. The reproducible PN code and reproducible data clock are output to the despreader and demodulator. The regenerative subunit includes a carrier modulator, a spread spectrum modulator, and a regenerative navigation data buffer. The reproducible navigation message generated by the demodulator is input into the regenerative navigation data buffer for buffering and processing to obtain regenerative navigation data. The reproducible PN code is then used by the spread spectrum modulator to spread spectrum modulate the reproducible navigation data. Finally, the carrier modulator uses the reproducible coherent carrier to perform carrier modulation on the spread spectrum modulation result to obtain the corresponding regenerative navigation signal.

8. The satellite navigation signal security isolation device according to claim 7, characterized in that, The first receiving and regenerating unit to the Lth receiving and regenerating unit are connected in series with a down-converter and an AD sampler, and then connected in series with a shared DA converter, up-converter and power regulator.

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