Anti-interference satellite navigation terminal indoor test system

Abstract

The invention discloses an anti-interference satellite navigation terminal indoor test system, relates to the technical field of big data analysis, and aims at improving the quality of test excitation signals and improving the reliability and accuracy of test results by performing chip estimation and regeneration on authorization signals and removing noise in test excitation. The regenerative modulation reserves authorization signal components, synchronizes Doppler and phase, does not need to apply for an authorization module, avoids the security management problem, simplifies the test process, reduces the cost, and enhances the flexibility. The isolation module shields outdoor leakage signals, assists in increasing test excitation power and overcomes attenuation; the power measurement module monitors feedback in real time and adjusts the adjustable attenuation control module, so that the radiation signal power is maintained in a preset range, the authorized satellite navigation receiver with the anti-interference receiving antenna works normally indoors, and powerful support is provided for research, development and production of satellite navigation terminals.

Description

Technical Field

[0001] The invention relates to the technical field of satellite navigation, in particular to an indoor test system for an anti-interference satellite navigation terminal. Background Art

[0002] The global satellite navigation system plays a critical role in many fields of modern society and has become an indispensable part of people's daily life and the operation of various industries. From the precise positioning and navigation of vehicles in intelligent transportation systems to help efficient travel and logistics distribution, to the precise management of farmland based on satellite positioning in the field of precision agriculture to improve crop yield and quality, to the acquisition of high-precision geographic coordinate information by satellite navigation in surveying and mapping, geographic information and other industries, its application range is wide and far-reaching, greatly promoting the development and progress of various industries.

[0003] However, there are still some problems with the global satellite navigation system. Satellite signals are relatively weak during transmission, easily interfered by external factors, and there is a risk of being maliciously counterfeited. To cope with these situations, some satellite navigation receivers are equipped with adaptive nulling antennas (Controlled Pattern Radiation Antenna, CPRA) to enhance anti-interference capabilities, and are also equipped with authorization signal receiving modules to receive authorized encrypted signals broadcast by satellites, thereby reducing the possibility of signal counterfeiting. However, there is a limitation of the authorization signal. Since its key is installed on the satellite, there is a lack of corresponding generated signal sources on the ground, which makes the test method of the receiver authorization signal relatively limited. Usually, it can only be received by the sky, or in indoor testing, the outdoor signal is forwarded to the indoor for broadcasting with the help of a satellite transponder. Currently, satellite transponders used indoors mostly use non-regenerative forwarding when processing authorization signals, which results in a large proportion of noise in the forwarded test stimulus signal. When the receiver under test has both CRPA and authorization signal receiving modules, it is difficult to adjust the transmission power of the satellite transponder. If the power is too high, the forwarded excitation signal will be misjudged as an interference signal by CRPA and suppressed; if the power is too low, the signal-to-noise ratio of the entire link cannot meet the requirements and the authorization signal receiving module will have difficulty working normally. Summary of the invention

[0004] The purpose of the present invention is to provide an indoor test system for an anti-interference satellite navigation terminal to solve the problems raised in the prior art.

[0005] To achieve the above object, the present invention provides the following technical solutions: an anti-interference satellite navigation terminal indoor test system, the anti-interference satellite navigation terminal indoor test system comprising a navigation signal regeneration module, a radio frequency optical carrier conversion module, an adjustable attenuation control module, an isolation module, a companion test navigation antenna module and a power measurement module; The navigation signal regeneration module is configured outdoors and uses a high-gain multi-beam antenna to synchronize the navigation satellite signals of no less than 16 target satellite navigation systems in real time, estimate and regenerate the received signals chip by chip, and generate a regenerated radio frequency navigation signal; The navigation signal regeneration module includes a high-gain multi-beam antenna unit and a signal processing unit; The high-gain multi-beam antenna unit is configured as a digital multi-beam phased array or no less than 16 independently servo-controlled directional antennas; The signal processing unit is used to amplify, filter, digitize and estimate each satellite signal chip by chip, retain the authorized signal component during regeneration modulation, and synchronize the Doppler and phase of the original signal; The chip-by-chip estimation of the signal processing unit comprises: The authorization code in the Beidou B3 frequency band signal is recovered at the chip level. The modulation characteristics of the authorization code are retained during regeneration, and the RF carrier frequency is consistent with the original signal.

[0006] The high-gain multi-beam antenna unit is any of the following modes: Mode a: Digital multi-beam phased array, including a planar or curved array and a digital beamforming module, forming at least 16 independent beams; Mode b: no less than 16 independent high-gain passive antennas, each of which is aimed at a single satellite in real time through a servo drive mechanism.

[0007] The signal regeneration process of the navigation signal regeneration module is as follows: Perform code synchronization and carrier synchronization on the target frequency band signal and estimate the authorized signal spread spectrum chip sequence; Based on the real-time code phase, carrier Doppler and code Doppler parameters, a regenerated authorization signal with the same frequency and phase as the original signal is re-modulated.

[0008] The radio frequency to optical carrier conversion module is used to convert the regenerated radio frequency navigation signal into an optical carrier signal and transmit it indoors via optical fiber; The adjustable attenuation control module is used to radiate the attenuated signal towards the receiver under test; The attenuation adjustment of the adjustable attenuation control module satisfies that the single-element receiving power of the regenerated signal after attenuation is higher than -133dBm and lower than -100dBm, so that the authorization module of the terminal under test can demodulate normally and the adaptive nulling antenna does not start interference suppression.

[0009] The RF-to-optical carrier conversion module adopts RF-to-optical transmission technology (RFoF) to modulate the regenerated RF signal onto an optical carrier and transmit it indoors. After photoelectric conversion, it is restored to a RF signal for processing by the adjustable attenuation control module.

[0010] The isolation module is used to cover the test area and provide shielding with a calibrated attenuation amount for the satellite navigation frequency band, so that the external leakage signal is attenuated to below the receiving sensitivity; The isolation module uses metal or electromagnetic shielding materials to form a closed test environment. The attenuation of the target navigation frequency band is determined by calibration, and the power of the external leakage signal after attenuation is at least 10dB lower than the receiving sensitivity.

[0011] The accompanying navigation antenna module is placed beside the tested adaptive nulling antenna and is used to monitor the regenerated signal power; The power measurement module is connected to the accompanying navigation antenna, and measures and feeds back the frequency band power of the navigation signal in real time to adjust the attenuation.

[0012] The accompanying navigation antenna module is a single-element active navigation antenna, and the distance between its installation position and the element of the tested adaptive nulling antenna does not exceed 0.5 wavelengths, and is used for equivalently monitoring the receiving power of the regenerated signal at the nulling antenna.

[0013] The power measurement module includes a spectrum analyzer, a detector or a power meter, which monitors the total power of the regenerated signal in the target frequency band in real time, and controls the adjustable attenuation through feedback to dynamically maintain the signal power radiated to the terminal under test within a preset threshold range.

[0014] Through the above system, there is no need to apply for authorization of any satellite navigation system. For mainstream anti-interference authorized receivers, the authorized signal can be broadcast indoors in an almost noise-free manner, and the transmission power can be adjusted so that the anti-interference antenna cannot be controlled. It can also effectively shield the signals that may leak into the room. The anti-interference authorized receiver can carry out various functional performance tests indoors, avoiding the disadvantage of only being able to test against the sky outdoors.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention estimates and regenerates the authorization signal through the navigation signal regeneration module, effectively removing the noise in the test stimulus. Compared with the traditional non-regeneration forwarding method of the satellite transponder, the quality of the test stimulus signal is greatly improved, the test error caused by excessive noise is avoided, and the receiver under test can receive and process the signal more accurately, thereby improving the reliability and accuracy of the test results.

[0016] 2. The present invention avoids the security management problem of the satellite navigation system by retaining the authorization signal component during the regeneration modulation process and synchronizing the Doppler and phase of the original signal without applying for any authorization module. This not only simplifies the test process and reduces the test cost, but also makes the test process more flexible and convenient, and can meet the test requirements in different scenarios.

[0017] 3. The present invention shields normal satellite navigation signals that may leak from outdoors through an isolation module, and assists in increasing the power of the test stimulus, thereby overcoming the attenuation of the test stimulus. At the same time, the power measurement module is used to monitor and feedback the navigation signal frequency band power in real time, and the attenuation of the adjustable attenuation control module is adjusted to dynamically maintain the signal power radiated to the terminal under test within a preset threshold range. In this way, the authorized satellite navigation receiver with an anti-interference receiving antenna can work normally indoors, effectively verifying the correctness of the equipment, and providing strong support for the research and development and production of satellite navigation terminals. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of an indoor test of an anti-interference authorized satellite navigation receiver according to an embodiment of the present invention; Figure 2 A schematic diagram comparing regenerative authorization signal forwarding and non-regenerative forwarding according to an embodiment of the present invention; Figure 3 A schematic diagram showing a comparison of the carrier-to-noise ratios of regenerative and non-regenerative authorization signal forwarding in an embodiment of the present invention; Figure 4 This is a schematic diagram of comparing the navigation signal power of each node in the test system according to an embodiment of the present invention; Figure 5 This is a schematic diagram of a multi-beam phased array navigation signal regeneration function according to an embodiment of the present invention; Figure 6 Schematic diagram of the authorization signal regeneration process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Taking the B3 frequency band of BeiDou-3 as an example, this frequency band includes B3I public signals and authorized signals. For anti-interference receivers that can receive signals and use CPRA antennas, they have strong anti-interference and anti-spoofing capabilities, but their testing problems are generally solved through outdoor testing and cannot be completed indoors.

[0021] Figure 1 This is a schematic diagram of an indoor test of an anti-interference authorized satellite navigation receiver according to an embodiment of the present invention; This test system consists of an outdoor navigation signal regeneration module, a radio frequency optical carrier conversion module, an indoor adjustable attenuation control module, a companion navigation antenna module, a power measurement module and an isolation module. The device under test is a satellite navigation receiver that has the ability to receive satellite navigation system authorization codes and is equipped with an adaptive nulling antenna.

[0022] The navigation signal regeneration module uses a high-gain multi-beam antenna to synchronize no less than 16 navigation satellites of the satellite navigation system of interest in real time, and digitize the frequency bands of interest. The high-gain multi-beam antenna unit is characterized by a large-aperture planar, spherical or other shaped digital multi-beam phased array, forming multiple real-time multi-beam synchronization of no less than 16 satellites; or no less than 16 directional high-gain passive antennas, each antenna synchronizes a satellite in real time through a motion servo mechanism. The high-gain multi-beam antenna unit amplifies, filters and digitally samples each satellite signal after receiving it, forming a digital stream equal to the number of satellites.

[0023] Specifically, a 16-beam phased array can be used to perform digital multi-beam forming on the B3 frequency of BeiDou-3 to form 16 digital streams, perform chip-by-chip estimation, and then perform chip-by-chip modulation. The modulation includes the authorized signal component. When the signal is regenerated, the Doppler and phase modulated for each satellite are the same as the received Doppler and phase.

[0024] The navigation signal regeneration module converts the regenerated radio frequency navigation signal into a radio frequency optical signal and transmits it through an optical fiber. The adjustable attenuation control module is characterized in that the regenerated navigation signal after being converted from an optical signal to a radio frequency signal is attenuated manually with a dynamic range of not less than 60 dB.

[0025] The adjustable attenuation control module is characterized in that the attenuated signal is radiated toward the receiver under test.

[0026] The isolation module is characterized by a shielding effect that attenuates the frequency band where the satellite navigation signal is located. The material is metal or electromagnetic shielding material, and the attenuation amount is known through calibration. The function of the isolation module is to attenuate the normal navigation signal that leaks into the room from the window or the open part of the non-fully enclosed shed to below the receiving sensitivity, so as not to interfere with the regenerated and forwarded test excitation signal.

[0027] The companion test navigation antenna module is characterized by a common active single-element navigation antenna placed close to the CPRA antenna under test to monitor the power of the regenerated authorization signal. The power measurement module is characterized by being able to measure the power of the navigation signal frequency band of interest, and can specifically be an electronic instrument such as a spectrum analyzer, detector or power meter with power measurement function.

[0028] The system's workflow is to use a high-gain multi-beam antenna to improve the signal-to-noise ratio of the authorized signal and then achieve regenerative forwarding, thereby eliminating the disadvantage of traditional non-regenerative satellite navigation repeaters that amplifies the received noise, resulting in a too low signal-to-noise ratio.

[0029] The regenerated authorized navigation signal is characterized by being a nearly pure signal, and the power can be increased to overcome the attenuation of the isolation module without affecting the overall carrier-to-noise ratio of the receiver under test.

[0030] After power adjustment, the regenerated authorized navigation signal is radiated to the receiver under test through the isolation module. The characteristic is that the power measurement module monitors the received power of a single array element and feeds back the power adjustment, which is required to be higher than the signal receiving sensitivity but lower than the thermal noise of the receiver under test.

[0031] Figure 2 A schematic diagram comparing regenerative authorization signal forwarding and non-regenerative forwarding according to an embodiment of the present invention; The navigation satellite to the outdoor navigation signal regeneration module and then to the receiver under test is equivalent to a signal forwarding system, and the signal waveform of each node is explained to illustrate the principle of the invention for regenerating and forwarding the authorization signal. For ordinary non-regenerative forwarding, the navigation signal is a pure signal when it starts from the satellite. When it reaches the outdoor phased array antenna, the signal is attenuated and superimposed with various interferences and noises to produce deformation. The non-regenerative forwarding amplifies the signal amplitude as a whole to compensate for the energy loss of the satellite signal in space transmission, but the signal-to-noise ratio will not be improved.

[0032] In the regenerative authorization signal forwarding, the signal is deformed when it reaches the outdoor phased array antenna, but the noise is removed through the large-aperture antenna and the regenerative signal processing flow, and it is regenerated into a pure authorization navigation signal and radiated to the receiver under test.

[0033] Figure 3 Schematic diagram of comparison of carrier-to-noise ratios of regenerative and non-regenerative authorization signal forwarding in an embodiment of the present invention.

[0034] For non-regenerative forwarding, assuming that the outdoor receiving B3 band signal carrier-to-noise ratio is 45dBHz, then the signal-to-noise ratio in the B3 band B=20.46MHz bandwidth is -28.1dB, which is equivalent to a signal-to-noise power ratio of 646:1. When the received power of a single antenna array element of the terminal under test is P, the thermal noise floor of the receiver under test is considered. If the signal level is -100dBm, the total carrier-to-noise ratio is calculated as follows: ; In the formula, CN0 represents the total carrier-to-noise ratio; B represents the working bandwidth of the receiver under test in the B3 frequency band; P represents the received power of a single antenna array element of the terminal under test; N0 represents the thermal noise floor of the receiver under test; ; As the power continues to increase, the carrier-to-noise ratio of non-regenerative forwarding will not exceed the receiving carrier-to-noise ratio of the outdoor unit antenna, and gradually enters a nonlinear growth, while the carrier-to-noise ratio of the regenerative forwarding signal can increase linearly. However, since the noise floor of the satellite navigation receiver in the B3 frequency band is about -100dBm, generally when the test excitation signal is higher than a certain detection threshold of the noise floor, the receiver will start the CPRA antenna for adaptive zeroing, resulting in the non-regenerative forwarding signal cannot be received normally. Regenerative forwarding can control the test excitation level to be lower than -100dBm, not triggering adaptive zeroing, and at the same time far higher than the receiving threshold of -133dBm.

[0035] Figure 4 This is a schematic diagram of the comparison of navigation signal powers of each node in the test system of an embodiment of the present invention. In the BeiDou-3 B3 navigation band, the signal center frequency is 1268.52MHz, the bandwidth is ±10.23MHz, and the thermal noise power within the signal bandwidth is generally fixed at -100dBm. The satellite navigation signal level leaking in from the window or the side of a non-fully enclosed shed is about -133dBm, which is within the receiving threshold, but after the assumed 40dB isolation, the level is attenuated to -173dBm and cannot be received normally. The test excitation signal power after adjustable attenuation can reach -70dBm, and there is still -110dBm after isolation, which is higher than the signal receiving threshold, but lower than the thermal noise floor of the receiver, and will not trigger the adaptive zeroing antenna control. Combined with the regeneration of the authorization signal, the receiver can normally receive the authorization signal component, thereby completing the functional test.

[0036] Figure 5 This is a schematic diagram of the multi-beam phased array navigation signal regeneration function of an embodiment of the present invention. This implementation adopts a digital multi-beam phased array antenna with an antenna gain of not less than 20dBi. Each oscillator is equipped with an independent RF channel and analog-to-digital conversion (ADC). The digital sampling signals of all oscillators enter the digital beamforming unit, and beam synthesis of no less than 16 satellites is performed to obtain a digital sampling stream with the same number of satellites. The subsequent signal processing unit estimates the authorized signal spread spectrum code contained in the frequency point from the digital sampling stream, records the real-time estimated code and carrier Doppler and phase, and remodulates according to the navigation signal format of the frequency point, and regenerates according to the real-time estimated code and carrier Doppler and phase during modulation.

[0037] Figure 6The figure is a schematic diagram of the authorization signal regeneration process of an embodiment of the present invention. The digital code stream formed by digital multi-beam first performs code synchronization and carrier synchronization on the signal with a code rate of 10.23Mcps at the B3 frequency point, and then determines to obtain an estimate of the spread spectrum code chips of each authorization signal. During code synchronization and carrier synchronization, the real-time code phase and carrier Doppler and code Doppler are synchronously recorded, and then the estimated code chips are used to regenerate the authorization signal in real time according to the Doppler and phase information, and up-converted to the B3 frequency point to obtain the RF signal, and then the RF Over Fiber (RFoF) technology is used to convert the RF signal into an optical signal for indoor transmission. Optical signals have the advantages of long transmission distance and low loss, and support the regeneration of outdoor navigation signals and the long-distance deployment of indoor units.

[0038] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. An anti-interference satellite navigation terminal indoor test system, characterized in that: The anti-interference satellite navigation terminal indoor test system includes a navigation signal regeneration module, a radio frequency optical carrier conversion module, an adjustable attenuation control module, an isolation module, a companion test navigation antenna module and a power measurement module; The navigation signal regeneration module is configured outdoors and uses a high-gain multi-beam antenna to synchronize the navigation satellite signal of the target satellite navigation system in real time, perform chip-by-chip estimation and regenerative modulation on the received signal, and generate a regenerated radio frequency navigation signal; The radio frequency to optical carrier conversion module is used to convert the regenerated radio frequency navigation signal into an optical carrier signal and transmit it indoors via optical fiber; The adjustable attenuation control module is used to radiate the attenuated signal towards the receiver under test; The isolation module is used to cover the test area and provide shielding with a calibrated attenuation amount for the satellite navigation frequency band, so that the external leakage signal is attenuated to below the receiving sensitivity; The accompanying navigation antenna module is placed beside the tested adaptive nulling antenna and is used to monitor the regenerated signal power; The power measurement module is connected to the accompanying navigation antenna, and measures and feeds back the frequency band power of the navigation signal in real time to adjust the attenuation.

2. The anti-interference satellite navigation terminal indoor test system according to claim 1, characterized in that: The navigation signal regeneration module includes a high-gain multi-beam antenna unit and a signal processing unit; The high-gain multi-beam antenna unit is configured as a digital multi-beam phased array or no less than 16 independently servo-controlled directional antennas; The signal processing unit is used to amplify, filter, digitize and estimate each satellite signal chip by chip, retain the authorized signal component during regeneration modulation, and synchronize the Doppler and phase of the original signal.

3. The anti-interference satellite navigation terminal indoor test system according to claim 2, characterized in that: The high-gain multi-beam antenna unit is any of the following modes: Mode a: Digital multi-beam phased array, including a planar or curved array and a digital beamforming module, forming at least 16 independent beams; Mode b: no less than 16 independent high-gain passive antennas, each of which is aimed at a single satellite in real time through a servo drive mechanism.

4. The anti-interference satellite navigation terminal indoor test system according to claim 1, characterized in that: The signal regeneration process of the navigation signal regeneration module is as follows: Perform code synchronization and carrier synchronization on the target frequency band signal and estimate the authorized signal spread spectrum chip sequence; Based on the real-time code phase, carrier Doppler and code Doppler parameters, a regenerated authorization signal with the same frequency and phase as the original signal is re-modulated.

5. The anti-interference satellite navigation terminal indoor test system according to claim 1, characterized in that: The attenuation adjustment of the adjustable attenuation control module satisfies that the single-element receiving power of the regenerated signal after attenuation is higher than -133dBm and lower than -100dBm, so that the authorization module of the terminal under test can demodulate normally and the adaptive nulling antenna does not start interference suppression.

6. The anti-interference satellite navigation terminal indoor test system according to claim 1, characterized in that: The isolation module uses metal or electromagnetic shielding materials to form a closed test environment. The attenuation of the target navigation frequency band is determined by calibration, and the power of the external leakage signal after attenuation is at least 10dB lower than the receiving sensitivity.

7. The anti-interference satellite navigation terminal indoor test system according to claim 1, characterized in that: The power measurement module includes a spectrum analyzer, a detector or a power meter, which monitors the total power of the regenerated signal in the target frequency band in real time, and controls the adjustable attenuation through feedback to dynamically maintain the signal power radiated to the terminal under test within a preset threshold range.

8. The anti-interference satellite navigation terminal indoor test system according to claim 2, characterized in that: The chip-by-chip estimation of the signal processing unit comprises: The authorization code in the Beidou B3 frequency band signal is recovered at the chip level. The modulation characteristics of the authorization code are retained during regeneration, and the RF carrier frequency is consistent with the original signal.

9. The anti-interference satellite navigation terminal indoor test system according to claim 1, characterized in that: The RF optical carrier conversion module adopts RF optical fiber transmission technology to modulate the regenerated RF signal into an optical carrier and transmit it indoors, and then restores it into a RF signal through photoelectric conversion for processing by the adjustable attenuation control module.

10. The anti-interference satellite navigation terminal indoor test system according to claim 1, characterized in that: The accompanying navigation antenna module is a single-element active navigation antenna, and the distance between its installation position and the element of the tested adaptive nulling antenna does not exceed 0.5 wavelengths, and is used for equivalently monitoring the receiving power of the regenerated signal at the nulling antenna.

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