Flexible anti-interference receiving system of navigation receiver based on double antennas

Abstract

The invention relates to a smart anti-interference receiving system of a navigation receiver based on double antennas. The system comprises a receiving antenna installed in an opposite-to-the-sky direction and a reference antenna installed in an opposite-to-the-ground direction. A signal received by the receiving antenna is a navigation signal; a signal received by the reference antenna is a reference interference signal; a radio frequency interference cancellation module is arranged; and inputting the reference interference signal into the radio frequency interference cancellation module for amplitude adjustment and phase adjustment, performing interference cancellation according to the reference interference signal after amplitude and phase adjustment and the signal received by the receiving antenna, and sending the navigation signal after interference cancellation into the navigation receiving module for navigation signal receiving processing. By adopting the system, the smart unmanned aerial vehicle navigation anti-interference can be realized.

Description

Technical Field

[0001] This application relates to the technical field of satellite navigation, and particularly to an anti-jamming receiving system for a smart navigation receiver based on dual antennas. Background Art

[0002] With the vigorous development of unmanned aerial vehicle (UAV) technology, its application fields are becoming increasingly extensive. When a UAV is working, it relies on a satellite navigation system for navigation. However, due to the low power of the navigation signal reaching the ground and the low working altitude of the UAV, it is extremely vulnerable to malicious ground interference, resulting in large positioning errors or even inability to position. Currently, the satellite navigation anti-jamming technologies used at home and abroad mainly include frequency-domain filtering anti-jamming technology, time-domain filtering anti-jamming technology, space-domain filtering anti-jamming technology, space-time adaptive filtering anti-jamming technology, etc. However, the above technologies are all implemented through antenna arrays or dedicated anti-jamming modules, either using relatively complex antenna arrays or dedicated anti-jamming processors, which are relatively large in terms of volume, weight, power consumption, cost, etc., and are not suitable for small UAVs. Summary of the Invention

[0003] Based on this, it is necessary to provide an anti-jamming receiving system for a smart navigation receiver based on dual antennas that can achieve anti-jamming for UAV-borne navigation in view of the above technical problems.

[0004] An anti-jamming receiving system for a smart navigation receiver based on dual antennas, the system includes a receiving antenna installed in the skyward direction, a reference antenna in the groundward direction, a radio frequency interference cancellation module, and a navigation receiving module; The receiving antenna is used to receive navigation signals; the reference antenna is used to receive reference interference signals; The radio frequency interference cancellation module is used to adjust the amplitude and phase of the reference interference signal, and perform interference cancellation on the reference interference signal after amplitude and phase adjustment and the signal received by the receiving antenna to obtain a navigation signal after interference cancellation; The navigation receiving module is used to perform navigation signal receiving and processing on the navigation signal after interference cancellation.

[0005] The above anti-jamming receiving system for a smart navigation receiver based on dual antennas. In this application, a radio frequency analog cancellation scheme based on dual antennas is adopted. According to the correlation between the signals received by different antennas, the amplitude-phase characteristics of the interference signal received by the reference antenna are adjusted to eliminate the interference signal superimposed on the receiving antenna, achieving the purpose of anti-jamming. The installation position of the antenna is not restricted. Unlike an anti-jamming antenna array, there is no strict restriction on the installation position of the sub-antennas, so the versatility is stronger. Moreover, the components used in the hardware solution of the set radio frequency interference cancellation module all have relatively low costs, which can effectively control the cost. By adopting the analog cancellation scheme, the types of interference signals suppressed are more extensive, not limited to specific interference types, and it also has a good suppression effect on broadband interference signals that are difficult to suppress by traditional anti-jamming algorithms, and can achieve smart unmanned aerial vehicle (UAV) navigation anti-jamming. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a schematic diagram of the framework of an anti-jamming receiving system for a smart navigation receiver based on dual antennas in an embodiment; Figure 2 It is a schematic diagram of the interference cancellation control process in an embodiment; Figure 3 It is a schematic diagram of the detailed process of interference cancellation in an embodiment; Figure 4 It is a spectrogram before interference cancellation for a broadband interference with a bandwidth of 10 MHz in another embodiment; Figure 5 It is a spectrogram after interference cancellation for a broadband interference with a bandwidth of 10 MHz in an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0007] In order to make the objectives, technical solutions, and advantages of this application clearer, the following further details this application in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0008] In an embodiment, as Figure 2 shown, an anti-jamming receiving system for a smart navigation receiver based on dual antennas is provided, including: A receiving antenna installed in the skyward direction and a reference antenna installed in the groundward direction; the signal received by the receiving antenna is a navigation signal; the signal received by the reference antenna is a reference interference signal.

[0009] Traditional anti-interference antenna arrays have strict requirements for the installation positions of sub-antennas. This is because the working principle of the antenna array is based on a specific spatial layout and signal processing method among multiple antennas to achieve the anti-interference function. In this application, a dual-antenna group is set up. The dual-antenna group consists of 2 identical antennas. One is installed in the skyward direction as the receiving antenna, and the corresponding received signal is used as the navigation signal; the other is installed in the groundward direction as the reference antenna, and the corresponding received signal is used as the reference interference signal. Considering the interference cancellation effect, the parameters of the two antennas should be kept as consistent as possible. And their installation positions do not need to be precisely coordinated with other antennas like an antenna array to implement a specific anti-interference algorithm. This installation method is more flexible. Whether it is installed on different models of unmanned aerial vehicles or at different parts of the unmanned aerial vehicle, as long as the basic direction requirements of the receiving antenna facing the sky and the reference antenna facing the ground are ensured, it can work normally, so the universality is stronger.

[0010] Set up a radio frequency interference cancellation module; input the reference interference signal into the radio frequency interference cancellation module for amplitude adjustment and phase adjustment, perform interference cancellation based on the reference interference signal after amplitude and phase adjustment and the signal received by the receiving antenna, and send the navigation signal after interference cancellation to the navigation receiving module for navigation signal receiving processing.

[0011] The radio frequency interference cancellation module consists of a digital controlled attenuator, a power splitter-phase shifter, an IQ vector modulator, a microcontroller, a power measurement module, a combiner, and a splitter. The digital controlled attenuator is used to adjust the amplitude of the reference interference signal, and the IQ vector modulator is used to adjust the phase of the reference interference signal. The reference interference signal enters the power splitter-phase shifter after passing through the digital attenuator, and outputs two orthogonal signals to the IQ vector modulator, and the IQ vector modulator adjusts the phase of the reference interference signal. The reference interference signal after phase adjustment and power adjustment is combined with the signal input by the other antenna and output to the power measurement module for power estimation. The microcontroller reads the power and adjusts the amplitude and phase of the reference interference signal to cancel it out with the interference signal received by the receiving antenna, eliminate the influence of the interference signal on the navigation signal reception, and finally send it to the navigation receiving module for navigation signal receiving processing.

[0012] In traditional anti-interference technologies, some use dedicated anti-interference processors. For example, devices such as FPGA (Field Programmable Gate Array) may be used. FPGA is a high-performance programmable logic device with powerful parallel processing capabilities and high flexibility, which can implement complex digital signal processing algorithms. However, the cost of FPGA is relatively high because its manufacturing process is complex and the R & D and production costs are high. In this application, the components used in the hardware solution have a lower cost. For example, a microcontroller such as a single-chip microcomputer can be used as the controller. A single-chip microcomputer is a microcontroller that integrates basic functional components such as a CPU, memory, and input / output interfaces, and its cost is relatively low. By using low-cost microprocessors such as single-chip microcomputers to control components such as the radio frequency interference cancellation module, the hardware cost can be effectively controlled without sacrificing the anti-interference performance.

[0013] The radio frequency cancellation process includes two-dimensional searches: 1) Phase search: The I and Q of vector modulation are determined by the phase. During the search, the phase values of I and Q are first searched. By stepping the phase values and based on the result of power estimation, the phase value corresponding to the minimum power is selected as the initial phase search result. 2) Gain search: Based on the obtained phase search value, the gain value is searched. According to the power estimation result, the phase value corresponding to the minimum power is selected as the initial gain search result.

[0014] Since the ground level of the navigation signal is low and it is usually submerged in noise, while the interference signal usually has a higher power. Therefore, when the interference and the useful navigation signal coexist, the interference will be suppressed and the navigation signal will not be greatly affected. In addition, for an unmanned aerial vehicle, the interference source is usually on the ground. Therefore, the elevation angle of the interference signal is negative, the reference antenna is installed facing the ground, and a strong interference signal can be received as the reference signal. The receiving antenna is installed facing the sky, which has a certain inhibitory effect on the ground interference signal entering from a negative elevation angle. The combination of the two antennas can effectively implement the analog cancellation scheme.

[0015] Compared with traditional anti-jamming technologies, such as the frequency-domain filtering anti-jamming technology, which analyzes the differences between interference signals and navigation signals in the frequency domain and designs filters to filter out interference signals. This technology has a good suppression effect on interference signals with obvious frequency characteristics. However, for broadband interference signals, since their frequency range is relatively wide and may cover the frequency range of navigation signals, it is very difficult to effectively separate the interference signals and navigation signals using frequency-domain filtering. The time-domain filtering anti-jamming technology mainly suppresses interference based on the characteristics of signals in the time domain and is effective for some interference signals with specific time characteristics, but it also has limitations for complex and variable broadband interference signals. In this application, the reference interference signal is amplitude-phase adjusted by the radio frequency interference cancellation module and then interference cancellation is performed with the signal received by the receiving antenna. This method does not depend on the specific frequency or time characteristics of the interference signal, but performs cancellation based on information such as the actual waveform and phase of the interference signal. Therefore, the types of interference signals suppressed by this application are more extensive. Whether it is narrowband interference or broadband interference, as long as accurate information about the reference interference signal can be obtained, cancellation can be performed by adjusting the amplitude and other operations, and it also has a good suppression effect on broadband interference signals that are difficult to suppress by traditional anti-jamming algorithms.

[0016] For the above-mentioned anti-jamming receiving system of a smart navigation receiver based on dual antennas, in this application, a radio frequency analog cancellation scheme based on dual antennas is adopted. According to the correlation between signals received by different antennas, the amplitude-phase characteristics of the interference signal received on the reference antenna are adjusted to eliminate the interference signal superimposed on the receiving antenna and achieve the anti-jamming purpose. The installation position of the antenna is not restricted. Unlike an anti-jamming antenna array, there is no strict restriction on the installation position of sub-antennas. Therefore, it has stronger versatility; and the components used in the hardware scheme of the set radio frequency interference cancellation module all have relatively low costs, which can effectively control costs; adopting the analog cancellation scheme, the types of interference signals suppressed are more extensive, not limited to specific interference types, and it also has a good suppression effect on broadband interference signals that are difficult to suppress by traditional anti-jamming algorithms, and can achieve smart unmanned aerial vehicle (UAV) navigation anti-jamming.

[0017] In one embodiment, the radio frequency interference cancellation module includes a digital control attenuator, a power splitter-phase shifter, an IQ vector modulator, a microcontroller, a power measurement module, a combiner, and a splitter.

[0018] In one embodiment, the radio frequency interference cancellation module is used to perform amplitude adjustment and phase adjustment on the reference interference signal, including: Input the reference interference signal S1 into the radio frequency interference cancellation module and pass it through the digital control attenuator. After attenuation, it is denoted as , and then enter the power splitter-phase shifter, which outputs two orthogonal signals to the IQ vector modulator. The IQ vector modulator adjusts the phase of the reference interference signal to obtain , where A represents the amplitude and θ represents the phase.

[0019] In one embodiment, the interference cancellation is performed between the reference interference signal adjusted according to the amplitude and phase and the signal received by the receiving antenna, including: The signal adjusted in amplitude and phase is combined with the signal S0 received by the receiving antenna to obtain S2, which is then output to the power measurement module for power estimation. The microcontroller reads the power estimation result and adjusts the amplitude and phase of the reference interference signal to cancel the interference between the reference interference signal and the interference signal received by the receiving antenna.

[0020] In one embodiment, as Figure 2 and Figure 3 shown, the process of interference cancellation includes: Initialize the phase adjustment step, amplitude adjustment step, phase search times, and amplitude search times; Adjust the phase of the reference interference signal according to the step, and obtain the power of the combined signal after each phase adjustment through the power measurement chip; After the phase search is completed, search for the minimum power value and obtain the corresponding optimal phase value; at the optimal phase value, adjust the attenuation of the digital controlled attenuator for amplitude adjustment; Adjust the attenuation in sequence, and obtain the power of the combined signal after each amplitude adjustment from the power measurement module; after the amplitude search is completed, search for the minimum extreme value of the power and obtain the corresponding optimal amplitude; Output the optimal phase and optimal amplitude to the digital controlled attenuator and IQ vector modulator to complete the current interference cancellation process.

[0021] In one embodiment, the system further includes a power evaluation module; the power evaluation module is used to evaluate the power of the navigation signal after interference cancellation, and uses the power evaluation result to reset the phase adjustment step, amplitude adjustment step, phase search times, and amplitude search times for interference cancellation.

[0022] In one embodiment, the process of the power evaluation module for evaluating the power of the navigation signal after interference cancellation includes: ; where, ICR represents the interference cancellation ratio, and the unit is dB, represents the power of the received signal before cancellation, the power of the signal after cancellation, represents the signal of the receiving channel, represents the signal after cancellation, and N is the data length.

[0023] In a specific embodiment, as Figure 4 and Figure 5As shown, it is a comparison chart before and after broadband interference cancellation for a broadband interference with a bandwidth of 10 MHz. It can be seen that the technical solution effectively suppresses the broadband interference signal, verifying the effectiveness of the technical solution.

[0024] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0025] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A dexterous navigation receiver anti-jamming receiving system based on dual antennas, characterized in that The system includes a receiving antenna installed in the skyward direction, a reference antenna in the groundward direction, a radio frequency interference cancellation module, and a navigation receiving module; The receiving antenna is used to receive navigation signals; the reference antenna is used to receive reference interference signals; The radio frequency interference cancellation module is used to adjust the amplitude and phase of the reference interference signal, and perform interference cancellation on the reference interference signal after amplitude and phase adjustment and the signal received by the receiving antenna to obtain a navigation signal after interference cancellation; The navigation receiving module is used to perform navigation signal receiving processing on the navigation signal after interference cancellation.

2. The system according to claim 1, wherein The radio frequency interference cancellation module includes a digital control attenuator, a power splitter and phase shifter, an IQ vector modulator, a microcontroller, a power measurement module, a combiner, and a splitter.

3. The system according to claim 2, wherein The radio frequency interference cancellation module is used to adjust the amplitude and phase of the reference interference signal, including: Input the reference interference signal S1 into the radio frequency interference cancellation module through the digital control attenuator. After attenuation, it is denoted as , and then enter the power splitter phase shifter, output two orthogonal signals to the IQ vector modulator. The IQ vector modulator adjusts the phase of the reference interference signal to obtain , where A represents the amplitude and θ represents the phase.

4. The system according to claim 3, wherein Performing interference cancellation on the reference interference signal after amplitude and phase adjustment and the signal received by the receiving antenna, including: Combining the signal after amplitude and phase adjustment with the signal S0 received by the receiving antenna to obtain S2, and outputting it to the power measurement module for power estimation. The microcontroller reads the power estimation result and adjusts the amplitude and phase of the reference interference signal to cancel the interference between the reference interference signal and the interference signal received by the receiving antenna.

5. The system according to claim 4, wherein The process of the interference cancellation includes: Initializing the phase adjustment step, amplitude adjustment step, phase search times, and amplitude search times; Adjusting the phase of the reference interference signal according to the step, and obtaining the power of the combined signal after each phase adjustment through the power measurement chip; After the phase search is completed, searching for the minimum power value and obtaining the corresponding optimal phase value; at the optimal phase value, adjusting the attenuation amount of the digital control attenuator for amplitude adjustment; Adjusting the attenuation amount in sequence, and obtaining the power of the combined signal after each amplitude adjustment from the power measurement module; after the amplitude search is completed, searching for the minimum extreme value of the power and obtaining the corresponding optimal amplitude; Outputting the optimal phase and optimal amplitude to the digital control attenuator and the IQ vector modulator to complete the current interference cancellation process.

6. The system according to claim 1, characterized in that, The system further includes a power evaluation module; the power evaluation module is used to evaluate the power of the navigation signal after interference cancellation, and use the power evaluation result to reset the phase adjustment step, amplitude adjustment step, phase search times, and amplitude search times for interference cancellation.

7. The system according to claim 6, wherein The process by which the power evaluation module is further used to evaluate the power of the navigation signal after interference cancellation includes: Among them, ICR represents the interference cancellation ratio, with the unit of dB. represents the received signal power before cancellation. The signal power after cancellation. represents the received channel signal. represents the signal after cancellation, and N is the data length.

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