Navigation system jamming signal direction finding system and method based on sum and difference ratio amplitude

Abstract

This application provides a navigation system interference signal direction finding system and method based on sum-difference amplitude ratio, belonging to the field of radio monitoring and signal direction finding technology. The system includes: a ground-based remote control device maneuvering a UAV to a preset altitude for autonomous rotation, cooperating with an airborne monitoring and direction finding platform to scan the airspace; the airborne monitoring and direction finding platform collecting and transmitting spectrum data and satellite signals in the navigation system frequency band to a ground terminal; the ground terminal identifying navigation system interference signals and triggering direction finding tasks; during the UAV's uniform rotation, the airborne monitoring and direction finding platform sampling navigation system interference signals, calculating the sum-difference amplitude ratio based on the sum and difference signals, and collecting the UAV's current nose-pointing azimuth angle; and the ground terminal calculating the direction finding results based on the nose-pointing azimuth angle, sum-difference amplitude ratio, position information, and attitude information. This application's solution can improve the accuracy and sensitivity of navigation system interference signal direction finding.

Description

Technical Field

[0001] This application relates to the field of radio monitoring and signal direction finding technology, specifically to a navigation system interference signal direction finding system and method based on sum-difference amplitude ratio. Background Technology

[0002] Currently, radio monitoring direction finding and interference signal investigation mainly rely on fixed monitoring stations and ground-based mobile monitoring vehicles. These traditional methods have significant limitations in long-distance coverage when facing high altitudes, mountainous areas, water bodies, and other complex terrains. Existing radio satellite monitoring platforms mostly adopt a single-channel architecture, with spectrum analysis and satellite signal interpretation processed sequentially.

[0003] In terms of direction finding systems, relying on traditional amplitude comparison or correlation interferometer systems not only results in large and heavy equipment with poor direction finding accuracy, but also insufficient sensitivity to weak signals. Traditional direction finding systems and ground monitoring methods are susceptible to ground multipath effects, leading to large direction finding errors and an inability to effectively locate weak interference sources.

[0004] Current technologies for navigation systems using interference signals have relatively low accuracy in direction finding. Therefore, improving the accuracy of direction finding using interference signals in navigation systems remains an unsolved problem. Summary of the Invention

[0005] The purpose of this application is to provide a navigation system interference signal direction finding system and method based on sum-difference amplitude, which can solve the problem of low accuracy of navigation system interference signal direction finding in the prior art.

[0006] In a first aspect, embodiments of this application provide a navigation system interference signal direction finding system based on sum-difference amplitude ratio, the system comprising: The ground remote control device is used to control the drone to take off to a preset altitude, hover and maintain stability, and control the drone to rotate autonomously; Unmanned aerial vehicles (UAVs) are used to scan the airspace by autonomously rotating in conjunction with an airborne monitoring and direction-finding platform. An airborne monitoring and direction finding platform, mounted on a UAV, is used to receive spectrum scanning tasks sent by a ground terminal, collect spectrum data and satellite signals in the navigation system frequency band, and transmit the spectrum data and satellite signals back to the ground terminal. The ground terminal is used to identify interference signals of the navigation system and trigger the direction finding task, send the direction finding task to the airborne monitoring and direction finding platform, and send flight control commands to the UAV. The airborne monitoring and orientation platform is also used to acquire the current position and attitude information of the UAV. During the process of the UAV rotating at a constant speed based on flight control commands, it samples the navigation system interference signal, calculates the sum and difference amplitude based on the sum and difference signals, and collects the current azimuth angle of the UAV's nose. The ground terminal is also used to calculate the direction finding results by employing interpolation fitting algorithms based on the azimuth angle of the nose, the sum-difference ratio, position information, and attitude information.

[0007] In one possible implementation of the first aspect, the airborne monitoring and direction finding platform includes: a dual-ridged horn antenna, a sum and difference feed network, and a receiver; The double-ridged horn antenna is installed at the bottom of the drone's mounting position. The output port of the double-ridged horn antenna is connected to the input port of the sum and difference feed network via an RF cable. The output port of the sum and difference feed network is connected to the channel input port of the receiver via an RF cable. A double-ridged horn antenna is used to receive interference signals from the navigation system during the process of a UAV rotating at a constant speed based on flight control commands; The sum and difference feed network is used to send navigation system interference signals to the receiver; The receiver is used to output the sum and difference signals in real time based on the interference signals of the navigation system, and to calculate the sum and difference amplitude based on the sum and difference signals, as well as to collect the current nose pointing azimuth angle of the UAV at a preset period. The receiver is also used to communicate with the drone's flight controller via a communication interface to obtain the drone's current position and attitude information.

[0008] In one possible implementation of the first aspect, the receiver is also used to obtain spectrum data based on full-band spectrum scanning, perform signal analysis and information extraction on whether the navigation system frequency signal is interfered with, and transmit the spectrum data and satellite signals back to the ground terminal via UAV image transmission link or dedicated data transmission link.

[0009] In one possible implementation of the first aspect, the receiver internally integrates a channel radio frequency front-end, a sum-difference amplitude network, and a signal processing unit. Channel radio frequency front end, used to receive interference signals from navigation systems; A sum-difference amplitude comparison network is used to output the sum and difference signals in real time based on navigation system interference signals. The signal processing unit is used to collect the current azimuth angle of the UAV's nose at a preset period, and to synchronously calculate the sum-difference ratio at the current moment based on the sum and difference signals.

[0010] Secondly, embodiments of this application provide a navigation system interference signal direction finding method based on sum-difference amplitude ratio, implemented based on the navigation system interference signal direction finding system based on sum-difference amplitude ratio ratio described in the first aspect. The method includes: The drone is controlled by a ground-based remote control device to ascend to a preset altitude, hover and remain stable, and then rotate autonomously. Based on unmanned aerial vehicles (UAVs), airspace scanning is performed through autonomous rotation in conjunction with an airborne monitoring and direction-finding platform. The airborne monitoring and direction finding platform receives spectrum scanning tasks sent by the ground terminal, collects spectrum data and satellite signals in the navigation system frequency band, and transmits the spectrum data and satellite signals back to the ground terminal. Based on the ground terminal, the navigation system interference signal identification and direction finding task triggering are performed, the direction finding task is sent to the airborne monitoring and direction finding platform, and flight control commands are sent to the UAV. Based on the airborne monitoring and orientation platform, the current position and attitude information of the UAV are obtained. During the process of the UAV rotating at a constant speed based on flight control commands, the navigation system interference signal is sampled, the sum and difference amplitude is calculated based on the sum and difference signals, and the current azimuth angle of the UAV's nose is collected. Based on the ground terminal, an interpolation fitting algorithm is used to calculate the direction finding results according to the azimuth angle of the nose, the sum and difference ratio, the position information, and the attitude information.

[0011] In one possible implementation of the second aspect, the method involves receiving a spectrum scanning task sent by a ground terminal based on an airborne monitoring and direction-finding platform, collecting spectrum data and satellite signals in the navigation system frequency band, and transmitting the spectrum data and satellite signals back to the ground terminal, including: Based on the spectrum data obtained by the receiver through full-band spectrum scanning, the navigation system frequency signal is analyzed and information on whether it is interfered with is extracted. The spectrum data and satellite signals are then transmitted back to the ground terminal through the UAV image transmission link or a dedicated data transmission link.

[0012] In one possible implementation of the second aspect, navigation system interference signal identification includes: Adaptive noise floor calculation and template comparison are performed on spectrum data and satellite signals; If the noise floor of the spectrum data in the frequency band rises beyond a preset threshold, or if the carrier-to-noise ratio of the satellite signal drops sharply, the corresponding spectrum data or satellite signal will be marked as the initial interference signal. Based on signal characteristic analysis, the initial interference signal is distinguished into suppression interference signal and deception interference signal.

[0013] In one possible implementation of the second aspect, based on an airborne monitoring and direction-finding platform, during the uniform rotation of the UAV based on flight control commands, navigation system interference signals are sampled, the sum-difference ratio is calculated based on the sum and difference signals, and the current azimuth angle of the UAV's nose is collected, including: Based on a double-ridged horn antenna, interference signals from the navigation system are received during the uniform rotation of the UAV based on flight control commands. Based on the sum-difference feed network, navigation system interference signals are sent to the receiver; Based on the receiver, the system outputs the sum and difference signals in real time based on the interference signals of the navigation system, calculates the sum and difference amplitude based on the sum and difference signals, and collects the current azimuth angle of the UAV's nose at a preset period.

[0014] In one possible implementation of the second aspect, an interpolation fitting algorithm is used to calculate the direction finding results based on the nose pointing azimuth angle, sum-difference ratio, position information, and attitude information, including: An interpolation fitting algorithm is used to locate the target nose pointing azimuth angle corresponding to the minimum point of the sum-difference ratio. Based on location information, attitude information, and the azimuth angle of the target aircraft's nose, a geographic direction line pointing to the interference source is generated; Among them, the geographic orientation line is the direction finding result.

[0015] In one possible implementation of the second aspect, the method further includes: Based on the ground terminal, during the direction finding process, a dynamic polar coordinate curve is generated in real time according to the sum and difference amplitude and the azimuth angle of the nose pointing, and the geographic direction line is displayed.

[0016] This application's solution uses an airborne monitoring and direction-finding platform mounted on a UAV to receive a spectrum scanning task sent by a ground terminal, collect and transmit spectrum data and satellite signals in the navigation system frequency band back to the ground terminal, then obtain the UAV's current position and attitude information, sample navigation system interference signals during the UAV's uniform rotation, calculate the sum-difference ratio based on the sum and difference signals, and collect the UAV's current nose pointing azimuth angle; finally, the ground terminal obtains the direction-finding results of the navigation system interference signals based on the nose pointing azimuth angle, sum-difference ratio, position information, and attitude information.

[0017] This application proposes an airborne monitoring and direction finding platform mounted on an unmanned aerial vehicle (UAV) to work with a ground terminal to find the direction of interference signals from the navigation system. It is less affected by ground multipath effects, has a small direction finding error, and can effectively locate weak interference sources, thereby improving the accuracy of direction finding of interference signals from the navigation system. It is highly user-friendly and practical.

[0018] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall structure of the navigation system interference signal direction finding system based on sum-difference amplitude provided in the embodiments of this application; Figure 2 This is a schematic diagram of the structure of the airborne monitoring and direction finding platform provided in the embodiments of this application; Figure 3 This is a schematic diagram of the receiver provided in an embodiment of this application; Figure 4 This is a schematic diagram of the steps of the navigation system interference signal direction finding method based on sum-difference amplitude provided in the embodiments of this application. Detailed Implementation

[0021] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application can also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0022] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or photovoltaic modules, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, photovoltaic modules and / or combinations thereof.

[0023] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0024] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0025] As used in this specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [the described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [the described condition or event] is detected," or "in response to detection of [the described condition or event]."

[0026] Furthermore, in the description of this application, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0027] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in some other embodiments," "in other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0028] Currently, radio monitoring direction finding and interference signal investigation mainly rely on fixed monitoring stations and ground-based mobile monitoring vehicles. These traditional methods have significant limitations in long-distance coverage when facing high altitudes, mountainous areas, water bodies, and other complex terrains. Existing radio ascent monitoring platforms mostly adopt a single-channel architecture, with spectrum analysis and satellite signal parsing processed serially, resulting in poor real-time performance, low efficiency, and high response delays.

[0029] In terms of direction finding systems, relying on traditional amplitude comparison or correlation interferometer systems not only results in large and heavy equipment with poor direction finding accuracy, but also insufficient sensitivity to weak signals. Furthermore, existing systems lack intelligent interference type identification capabilities (such as the inability to distinguish between suppression and deceptive interference) and false alarm elimination capabilities. The systems rely on manual experience for interpretation, making it difficult to meet current needs for mobile and rapid radio order management.

[0030] The existing technology has the following problems: (1) Poor spatial mobility: Ground equipment is severely obstructed by terrain and objects, making it difficult to achieve rapid arrival and efficient inspection in wide and complex geographical environments; (2) Insufficient timeliness and real-time performance: The single-channel architecture makes it impossible to perform full-band scanning and target signal analysis synchronously, and it is easy to miss sudden or transient interference during rapid frequency scanning; (3) Low direction finding accuracy and sensitivity: Traditional direction finding systems and ground monitoring direction finding methods are easily affected by ground multipath effects, resulting in large direction finding errors and inability to effectively locate weak interference sources; (4) Low system integration: The existing monitoring and direction finding system (receiver, antenna, data link, monitoring software, etc.) lacks deep adaptation with the UAV flight control system, making it difficult to meet the UAV payload's requirements for lightweight, low power consumption and rapid entry into working state; (5) Information silos: Information such as spectrum data, satellite positioning information, interference situation, and direction finding is not integrated and visualized, and is not intuitive; (6) Lack of intelligent monitoring: Due to the lack of deep integration between the monitoring and direction finding system and the UAV flight control system, the monitoring system cannot achieve automatic patrol of the planned area in the air, autonomous interference identification, autonomous early warning and mission triggering.

[0031] To address the aforementioned shortcomings, this application provides a navigation system interference signal direction finding system and method based on sum-difference amplitude ratio. An airborne monitoring and direction finding platform mounted on a UAV receives a spectrum scanning task sent by a ground terminal, collects and transmits spectrum data and satellite signals in the navigation system frequency band back to the ground terminal, then obtains the UAV's current position and attitude information. During the UAV's uniform rotation, navigation system interference signals are sampled, the sum-difference amplitude ratio is calculated based on the sum and difference signals, and the UAV's current nose-pointing azimuth angle is collected. Finally, the ground terminal obtains the direction finding result of the navigation system interference signal based on the nose-pointing azimuth angle, sum-difference amplitude ratio, position information, and attitude information.

[0032] This application proposes an airborne monitoring and direction finding platform mounted on an unmanned aerial vehicle (UAV) to work with a ground terminal to find the direction of interference signals from the navigation system. It is less affected by ground multipath effects, has a small direction finding error, and can effectively locate weak interference sources, thereby improving the accuracy of direction finding of interference signals from the navigation system. It is highly user-friendly and practical.

[0033] This application specifically relates to a monitoring, direction finding, and positioning system and method for GNSS (Global Navigation Satellite System) and VHF / UHF band interference signals, applied to an unmanned aerial vehicle (UAV) launch platform. The specific implementation process of this application is described below through specific embodiments.

[0034] Please see Figure 1 , Figure 1 This is a schematic diagram of the overall structure of the navigation system interference signal direction finding system based on sum-difference amplitude ratio provided in the embodiments of this application. Figure 1 As shown, the system includes: a ground remote control device, a drone, an airborne monitoring and direction finding platform, and a ground terminal.

[0035] According to one embodiment of this application, a ground-based remote control device controls a drone to ascend to a preset altitude, hover and maintain stability, and controls the drone to perform autonomous rotation. The drone performs airspace scanning in conjunction with an airborne monitoring and direction-finding platform through autonomous rotation. The airborne monitoring and direction-finding platform, mounted on the drone, receives spectrum scanning tasks sent by a ground terminal, collects spectrum data and satellite signals in the navigation system frequency band, and transmits the spectrum data and satellite signals back to the ground terminal.

[0036] In one embodiment, the ground remote control device is a remote controller or other device with remote control functionality, and the preset altitude is below 120m above ground level. Ground operators use the ground remote control device to control the UAV to perform 360° autonomous rotation, and complete a 360° airspace scan by coordinating the UAV's spin with a monitoring and direction-finding payload (airborne monitoring and direction-finding platform).

[0037] In one embodiment, the UAV serves as an airborne platform, capable of hovering, rotating, and flying to preset waypoints; a quick-release interface is provided under the fuselage for mounting an airborne monitoring and direction-finding platform; and power and communication networks are provided for the airborne monitoring and direction-finding platform.

[0038] In one embodiment, the ground terminal issues a spectrum scanning task, the airborne monitoring and direction finding platform receives the spectrum scanning task, executes the spectrum scanning task, and collects and transmits spectrum data and satellite signals of the navigation system frequency band back to the ground terminal.

[0039] According to one embodiment of this application, the ground terminal identifies navigation system interference signals and triggers direction finding tasks, sends direction finding tasks to the airborne monitoring and direction finding platform, and sends flight control commands to the UAV. The airborne monitoring and direction finding platform acquires the current position and attitude information of the UAV. During the UAV's uniform rotation based on flight control commands, it samples navigation system interference signals, calculates the sum-difference amplitude ratio based on the sum and difference signals, and collects the current nose pointing azimuth angle of the UAV.

[0040] In one embodiment, the navigation system can be GNSS. After the ground terminal sends flight control commands to the UAV, the UAV receives the commands and automatically performs a constant-speed rotation at its original position (the rotation speed can be 6° / s - 12° / s), without the need for manual joystick intervention.

[0041] In one embodiment, the location information includes latitude and longitude, altitude, etc., and the attitude information includes heading angle, pitch angle, etc., which serve as direction finding reference data.

[0042] It should be noted that the specific implementation principle of this embodiment will be explained in subsequent method embodiments.

[0043] According to one embodiment of this application, the ground terminal uses an interpolation fitting algorithm to calculate the direction finding results based on the azimuth angle of the nose, the sum-difference ratio, the position information, and the attitude information.

[0044] It should be noted that the specific implementation principle of this embodiment will be explained in subsequent method embodiments.

[0045] In one embodiment, the ground terminal runs Supernova fusion display and control software (ground station software), which has functions such as task issuance, data reception, calculation, situation display and early warning.

[0046] Please see Figure 2 , Figure 2 This is a schematic diagram of the structure of the airborne monitoring and direction-finding platform provided in the embodiments of this application. Figure 2 As shown, the airborne monitoring and direction finding platform includes: a double-ridged horn antenna, a sum and difference feed network, and a receiver.

[0047] According to one embodiment of this application, a double-ridged horn antenna is installed at the bottom of the UAV mounting position. The output port of the double-ridged horn antenna is connected to the input port of the sum-difference feed network via an RF cable. The output port of the sum-difference feed network is connected to the channel input port of the receiver via an RF cable.

[0048] In one embodiment, the dual-ridged horn antenna is composed of two high-gain dual-ridged horns and features a lightweight, wide-bandwidth design, operating within the existing GNSS operating frequency range. The antenna is mounted at the bottom of the UAV mounting position, and the connections from bottom to top are as follows: first, the output port of the dual-ridged horn antenna is connected to the two input ports of the sum-difference feed network via two RF cables; then, the two output ports of the sum-difference feed network are connected to the dual-channel input ports of the high-performance, low-power receiver (integrated receiver) via two RF cables.

[0049] According to one embodiment of this application, the dual-ridged horn antenna receives navigation system interference signals during the uniform rotation of the UAV based on flight control commands. The sum-difference feed network transmits the navigation system interference signals to the receiver.

[0050] According to one embodiment of this application, the receiver outputs a sum and difference signal in real time based on the navigation system interference signal, calculates the sum-difference amplitude ratio based on the sum and difference signals, and collects the current nose-pointing azimuth angle of the UAV at a preset period. The receiver also communicates with the UAV's flight controller via a communication interface to obtain the UAV's current position and attitude information.

[0051] In one embodiment, the preset period is a fixed period, such as 10ms. The azimuth angle of the drone's nose is obtained from the electronic compass of the drone's flight controller. The receiver communicates with the drone's flight controller via a Type-C interface to obtain information such as flight attitude, azimuth angle of the nose, latitude, longitude, and altitude.

[0052] According to one embodiment of this application, the receiver is also used to obtain spectrum data based on full-band spectrum scanning, perform signal analysis and information extraction on whether the navigation system frequency signal is interfered with, and transmit the spectrum data and satellite signal back to the ground terminal through the UAV image transmission link or a dedicated data transmission link.

[0053] In one embodiment, the receiver initiates dual-channel parallel acquisition. Channel 1 is responsible for rapid full-band spectrum scanning, while channel 2 is responsible for signal analysis and interference detection of GNSS frequency signals. The receiver interacts with the ground terminal at high speed via the UAV image transmission link / dedicated data transmission link, transmitting the spectrum data and satellite signals in the GNSS band (the analyzed GNSS frequency signals with interference detection information) back to the ground terminal, completing the first round of basic data transmission.

[0054] According to another embodiment of this application, the sum-difference feed network is replaced with a dual-mode reconfigurable sum-difference feed network. Based on the original fixed sum-difference feed network, an RF switch matrix and a phase shifter group are added to support real-time switching between sum-difference direction finding mode and adaptive null mode. During direction finding intervals, the dual-mode reconfigurable sum-difference feed network switches to adaptive null mode. The receiver calculates the optimal weights in real time based on the received interference signals, forming dynamic nulls in the radiation pattern of the double-ridge horn antenna. This actively suppresses strong interference in known directions, protecting the navigation system from suppression during direction finding.

[0055] In one embodiment, the RF switch matrix reconfigures the amplitude and phase distribution on the antenna aperture by controlling the on / off state of the RF path. In the sum-difference direction finding mode, the RF switch matrix connects the antenna port to the sum-difference amplitude comparison network, outputting standard sum and difference signals for sum-difference amplitude calculation; in the anti-interference mode (adaptive null mode), the RF switch matrix disconnects the sum-difference amplitude comparison network and connects different output ports of the antenna to the phase shifter group. In this case, the antenna is no longer used as a direction finding antenna, but as an adaptive array antenna.

[0056] In one embodiment, the phase shifter group, under the control of the signal processing unit inside the receiver, calculates the direction of the interference signal in real time, and then applies a specific phase delay (adjustable from 0° to 360°) to the signals of different channels of the antenna. These phase delays cause the electromagnetic waves entering the antenna from the direction of interference to cancel each other out in phase during synthesis.

[0057] In one embodiment, the RF switch matrix injects an internal standard calibration source (a signal with known amplitude and phase) into the antenna receiving link when idle. The phase shifter group actively adjusts the phase value for reverse compensation based on the measurement deviation of the calibration source, which is equivalent to adding a dynamic zeroing mechanism to the direction finding system, eliminating the zero bias of the hardware itself in real time during each direction finding.

[0058] In one embodiment, the interval is a millisecond-level idle time between two direction-finding sampling points (e.g., a 2ms window in a 5ms interval). At the instant of entering the interval, the RF switch matrix cuts off the sum-difference-amplitude network channel, sending the raw RF signal received by the antenna to the signal processing unit of the receiver.

[0059] The signal processing unit performs a Fast Fourier Transform on the received interference signal to extract two key parameters: the spatial phase difference of the interference and the amplitude envelope of the interference. Then, it calculates the optimal weights in real time: based on the extracted parameters, it uses the minimum variance distortionless response or the linearly constrained minimum variance criterion to calculate a set of complex weights (amplitude + phase) in real time.

[0060] The receiver converts the phase and amplitude weights into the control voltage for the phase shifter and the control current for the attenuator, and sends them to the phase shifter group in the feed network. After a null is formed, the signal from the interference source is significantly attenuated inside the feed network before entering the antenna port, thus protecting the navigation system.

[0061] Please see Figure 3 , Figure 3 This is a schematic diagram of the receiver provided in an embodiment of this application. Figure 3 As shown, the receiver integrates a channel RF front-end, a sum-difference amplitude comparison network, and a signal processing unit. The channel RF front-end receives navigation system interference signals, and the sum-difference amplitude comparison network outputs the sum and difference signals in real time based on the navigation system interference signals. The signal processing unit acquires the current azimuth angle of the UAV's nose at a preset period and simultaneously calculates the sum-difference amplitude at the current moment based on the sum and difference signals.

[0062] In one embodiment, the receiver integrates a dual-channel RF front-end, a sum-difference-amplitude network, and an FPGA (Field-Programmable Gate Array) high-speed baseband processing unit (signal processing unit).

[0063] Please see Figure 4 , Figure 4 This is a schematic diagram illustrating the steps of the navigation system interference signal direction finding method based on sum-difference amplitude ratio provided in this application embodiment. The navigation system interference signal direction finding system based on sum-difference amplitude ratio can implement this method, such as... Figure 4 As shown, the method includes the following steps: The S401 is a device that uses a ground-based remote control to control a drone to ascend to a preset altitude, hover and maintain stability, and control the drone to rotate autonomously.

[0064] The S402 is an unmanned aerial vehicle (UAV) that performs airspace scanning through autonomous rotation in conjunction with an airborne monitoring and direction-finding platform.

[0065] The S403, based on an airborne monitoring and direction finding platform, receives spectrum scanning tasks sent by ground terminals, collects spectrum data and satellite signals in the navigation system frequency band, and transmits the spectrum data and satellite signals back to the ground terminals.

[0066] According to one embodiment of this application, a spectrum scanning task sent by a ground terminal is received based on an airborne monitoring and direction finding platform, and spectrum data and satellite signals of the navigation system frequency band are collected. The spectrum data and satellite signals are then transmitted back to the ground terminal. The process includes: obtaining spectrum data through full-band spectrum scanning using a receiver, performing signal analysis and extracting information on whether the navigation system frequency signals are interfered with, and transmitting the spectrum data and satellite signals back to the ground terminal via a UAV image transmission link or a dedicated data transmission link.

[0067] S404 identifies navigation system interference signals and triggers direction finding tasks based on ground terminals, sends direction finding tasks to airborne monitoring and direction finding platforms, and sends flight control commands to UAVs.

[0068] According to one embodiment of this application, the navigation system interference signal identification includes: performing adaptive noise floor calculation and template comparison on spectrum data and satellite signals; if the noise floor rise of spectrum data in the frequency band exceeds a preset threshold, or the carrier-to-noise ratio of satellite signals drops sharply in a group, then the corresponding spectrum data or satellite signals are marked as initial interference signals; based on signal feature analysis, the initial interference signals are distinguished into suppression interference signals and deception interference signals.

[0069] In one embodiment, the ground terminal first calculates the current noise floor level from the spectrum data and satellite signals using a noise floor adaptive algorithm, and then compares it with the corresponding preset templates to identify signal anomalies or interference.

[0070] In one embodiment, if the noise floor of the spectrum data in the frequency band rises above a preset threshold (e.g., ≥10dB), or if the carrier-to-noise ratio (C / N0) of the satellite signal drops sharply in a group, the ground terminal will automatically mark it as a suspected interference signal and pop up a warning prompt on the ground terminal interface.

[0071] In one embodiment, the ground terminal further analyzes the signal characteristics to distinguish between suppression jamming signals (wideband noise floor increase) and deceptive jamming signals (pseudo-satellite signal characteristics).

[0072] In one embodiment, after receiving an early warning through a ground terminal, the ground operator clicks to confirm the direction finding through the ground terminal interface. The airborne monitoring and direction finding platform automatically enters the direction finding preparation state and simultaneously reads the current latitude, longitude, altitude, heading angle, pitch angle and other information of the UAV as the direction finding reference data.

[0073] The S405, based on an airborne monitoring and direction finding platform, acquires the current position and attitude information of the UAV. During the UAV's uniform rotation based on flight control commands, it samples navigation system interference signals, calculates the sum and difference amplitude based on the sum and difference signals, and collects the current azimuth angle of the UAV's nose.

[0074] According to one embodiment of this application, based on an airborne monitoring and direction-finding platform, during the uniform rotation of the UAV based on flight control commands, the system samples navigation system interference signals, calculates the sum-difference ratio based on the sum and difference signals, and collects the current azimuth angle of the UAV's nose, including: Based on a dual-ridge horn antenna, the system receives navigation system interference signals during the uniform rotation of the UAV based on flight control commands; based on a sum-difference feed network, the system sends navigation system interference signals to the receiver; based on the receiver, the system outputs sum and difference signals in real time based on the navigation system interference signals, and calculates the sum-difference amplitude ratio based on the sum and difference signals, and collects the current nose pointing azimuth angle of the UAV at a preset period.

[0075] In one embodiment, the sum-difference-amplitude network inside the receiver outputs the sum signal (Σ) and difference signal (Δ) in real time. The FPGA high-speed baseband processing unit acquires the current nose-pointing azimuth angle (θ) of the UAV at fixed intervals (e.g., 10ms). t (From the flight control electronic compass), and simultaneously calculate the sum-difference ratio R(θ) at the current moment. t = |Δ| / |Σ| = difference signal amplitude / sum signal amplitude.

[0076] In another embodiment, the complex vector sum-difference ratio is calculated based on the difference signal amplitude, the sum signal amplitude, and the instantaneous phase difference between the sum and difference channels. The specific calculation formula is as follows:

[0077] in, Represents the sum and difference magnitudes of complex vectors. This represents the instantaneous phase difference between the sum and difference channels. e It is a natural constant. j It is the imaginary unit.

[0078] The S406, based on a ground terminal, uses an interpolation fitting algorithm to calculate the direction finding results based on the nose pointing azimuth, sum-difference ratio, position information, and attitude information.

[0079] According to one embodiment of this application, an interpolation fitting algorithm is used to calculate the direction finding results based on the nose pointing azimuth, sum-difference ratio, position information, and attitude information. The calculation includes: using an interpolation fitting algorithm to locate the target nose pointing azimuth corresponding to the minimum point of the sum-difference ratio; and generating a geographic direction finding line pointing to the interference source based on the position information, attitude information, and target nose pointing azimuth. The geographic direction finding line represents the direction finding result.

[0080] In one embodiment, when the drone rotates to a specific nose pointing at an azimuth angle θ s At this time, the interference signal is exactly facing the main beam of the antenna, and the difference signal energy is at its minimum (Δ→0), and the sum-difference ratio R has a unique minimum point (valley).

[0081] In one embodiment, the ground terminal uses an interpolation fitting algorithm to locate the minimum point of the sum-difference ratio, corresponding to the nose-pointing azimuth angle θ. s The specific steps are as follows: (1) Establish a dynamic mapping relationship between the sum and difference ratio and the azimuth of the finger pointing, and construct the "nose pointing azimuth - sum and difference ratio" curve: Acquire a set of discrete data points and record multiple azimuth angles (independent variable, denoted as θ) of the drone's nose as it rotates. t The ratio of the sum and difference to the corresponding sum and difference (dependent variable, denoted as R(θ)) t The sum-difference ratio approaches zero near the direction of the main beam (i.e., the direction of the interference signal), forming a trough.

[0082] (2) The confidence interval of the nose pointing azimuth corresponding to the minimum value of the sum-difference ratio is: First, a rough location is established: among the discrete data points, determine the point with the smallest sum-to-difference ratio, and denot the corresponding azimuth angle of the aircraft head as θ. min Then, extract the interval: using θ min Centered on the main lobe, a smaller angular range (e.g., 1 / 3 to 1 / 2 of the main lobe width) is selected. The sum-difference ratio amplitude and angle within this range approximately satisfy a linear relationship, which forms the basis for high-precision fitting.

[0083] (3) Perform interpolation fitting to construct a locally accurate model: Within the extracted confidence interval, a polynomial or Gaussian model is used to fit the discrete points. Polynomial fitting is used because the curve resembles a parabola near its minimum value; a quadratic polynomial is employed. The coefficients a, b, and c are determined using the least squares method for fitting. Gaussian fitting is employed: if the main lobe shape of the antenna pattern is closer to a Gaussian curve, then fitting with a Gaussian function will yield higher accuracy.

[0084] (4) Find the azimuth angle corresponding to the point where the sum-difference ratio amplitude is at its minimum: For a quadratic polynomial, its minimum point is the vertex of the parabola. By taking the derivative, we can obtain the nose pointing azimuth angle corresponding to the minimum value of the sum-difference ratio: For a Gaussian function, the x-coordinate of its minimum point is the mean parameter μ in the function. The mean parameter μ is used as the azimuth angle of the aircraft head corresponding to the minimum value of the sum-difference ratio.

[0085] In one embodiment, the target nose pointing azimuth angle θ is corrected by combining the UAV's real-time latitude and longitude altitude, heading angle, and magnetic declination. s Generate a geographic direction line pointing to the interference source, specifically by: based on the heading angle and θ s Calculate the azimuth of the interference source, draw a line pointing towards the interference source along its azimuth, and mark the real-time latitude, longitude, and altitude. Wherein, interference source azimuth = heading angle + θ s .

[0086] According to one embodiment of this application, the method further includes: based on a ground terminal, generating a dynamic polar coordinate curve in real time according to the sum-difference ratio and the azimuth angle of the aircraft head during the direction finding process, and displaying the geographic direction line.

[0087] In one embodiment, to eliminate single-point errors, the UAV is supported in flying to the next observation point, repeating the direction finding steps, and using the cross-positioning method to lock the precise location of the interference source.

[0088] In one embodiment, all process data (spectral graphs, geographic direction lines, flight trajectories, and early warning records) are stored uniformly to generate an interference investigation report.

[0089] It should be noted that for parts not described in detail in the method embodiments, please refer to the system embodiments.

[0090] The navigation system interference signal direction finding system and method based on sum-difference amplitude ratio provided in this application embodiment receive spectrum scanning tasks sent by ground terminals through an airborne monitoring and direction finding platform mounted on a UAV, and collect and transmit spectrum data and satellite signals of the navigation system frequency band back to the ground terminal. Then, the current position and attitude information of the UAV are obtained. During the uniform rotation of the UAV, the navigation system interference signal is sampled, the sum-difference amplitude is calculated based on the sum and difference signals, and the current nose pointing azimuth angle of the UAV is collected. Finally, the direction finding result of the navigation system interference signal is obtained by the ground terminal based on the nose pointing azimuth angle, sum-difference amplitude ratio, position information and attitude information.

[0091] This application proposes an airborne monitoring and direction finding platform mounted on an unmanned aerial vehicle (UAV) to work with a ground terminal to find the direction of interference signals from the navigation system. It is less affected by ground multipath effects, has a small direction finding error, and can effectively locate weak interference sources, thereby improving the accuracy of direction finding of interference signals from the navigation system. It is highly user-friendly and practical.

[0092] The core objective of this application is as follows: (1) Break through spatial limitations: Utilize the UAV launch platform to achieve full-domain, rapid and flexible aerial mobile monitoring; (2) Improve processing efficiency: Through a dual-channel parallel architecture, parallel real-time analysis of spectrum monitoring and satellite navigation data is achieved; (3) Improve direction finding accuracy: By using the improved sum-difference ratio amplitude direction finding algorithm and combining it with the open line of sight in the air, the direction finding accuracy is greatly improved, and the high-gain horn antenna enhances the ability to sense weak signals. (4) Achieve deep system integration: Design lightweight, low-power airborne payloads to achieve integrated collaborative operation of flight control, monitoring, and orientation finding; (5) Construct an intelligent closed-loop process: integrate the automatic interference identification and early warning triggering mechanism to form an automated operation closed loop of "monitoring-identification-direction finding-positioning".

[0093] The beneficial effects of this application are as follows: (1) Significant mobility and rapid response capability: By taking off with UAVs, deployment can be completed within 5 minutes, enabling high-altitude wide-area monitoring, effectively avoiding ground obstruction and multipath effects, and increasing the monitoring coverage by more than 10 times compared to ground equipment; (2) High-efficiency parallel processing capability: The dual-channel hardware architecture combined with FPGA parallel computing solves the pain point of traditional equipment losing satellites when scanning frequencies. Spectrum scanning and GNSS calculation are performed synchronously, and the system processing delay is less than 100ms. (3) High-precision direction finding performance: By utilizing the advantage of line-of-sight in the air to eliminate multipath, and combined with the sum-difference ratio amplitude algorithm which still has good monotonicity under low signal-to-noise ratio, the direction finding accuracy (RMS, Root Mean Square) is better than ±1°, and it is still effective for weak interference signals with sensitivity below -100dBm. (4) Highly integrated lightweight payload: It eliminates the need for long baseline antenna arrays and complex calibration networks required by interferometers, and the overall payload weight is less than 1.5kg. It can be adapted to a variety of mainstream UAVs on the market, achieving a balance between monitoring capabilities and flight performance; (5) Intelligent closed-loop operation process: Built-in automatic interference identification and self-rotation direction finding logic reduces the operation threshold and realizes the automatic transformation from manual discovery to system triggering, which greatly improves the investigation efficiency.

[0094] The focus of this application is on the sum-difference amplitude direction finding method based on the coordination of the aircraft head pointing and the electronic compass, as well as the matching automated direction finding operation process.

[0095] The key points of this application are: (1) Integrated UAV mounting and take-off: lightweight integration; (2) Dual-channel parallel processing architecture: simultaneously complete spectrum monitoring and satellite data analysis; (3) Sum-difference amplitude direction finding method: combining nose pointing, electronic compass, and rotation direction finding logic; (4) Interference identification: adaptive noise floor, suppression / deception differentiation, and spectrum comparison; (5) Multi-information fusion of Supernova interface: unified presentation of spectrum, GPS, angle measurement, and interference situation.

[0096] The protection points of this application are: (1) Structural protection: the integrated structure of the airborne GNSS ultra-shortwave mobile monitoring system; (2) Method protection: the sum-difference amplitude direction finding and self-rotation positioning method; (3) Algorithm protection: the automatic interference identification and early warning threshold adaptive method; (4) System protection: the airborne-remote control-terminal linkage direction finding operation process and interaction logic.

[0097] This proposed solution is not constrained by terrain or other environmental conditions, allowing for rapid deployment to high-altitude areas without entering sensitive zones, thus enhancing safety for detecting illegal signals, unauthorized flights, and GNSS interference. The algorithm is simple, with lower hardware costs, making it simpler, requiring less calibration, and lighter than interferometer direction finding structures. It is suitable for UAV mounting, and the sum-difference network combined with dual-ridge horn antennas is small in size and lightweight, adapting to UAV payload limitations.

[0098] The proposed solution boasts high system sensitivity, enabling stable direction finding even under low-level GNSS interference and weak VHF / UHF signals. Combined with the high-altitude, open-view perspective of the UAV, the direction-finding accuracy reaches ≤±1°, far superior to traditional ground-based amplitude comparison direction finding. The high-altitude perspective avoids ground reflections and obstructions, resulting in cleaner direction-finding results and fewer misjudgments.

[0099] The proposed solution has the following features: (1) Adaptability to airborne sum-difference amplitude direction finding system: The traditional ground radar sum-difference amplitude technology, after algorithm improvement (especially optimization for minimum value determination) and lightweight hardware design, has been successfully adapted to the UAV launch platform for the first time. (2) Deep integration of attitude perception and direction finding algorithm: By synchronously collecting flight control data (nose pointing) and radio signal amplitude ratio (R value) at high frequency, and aligning the data with timestamps, the direction finding error caused by UAV shaking is solved. (3) Automated self-rotation direction finding logic: A clear set of UAV action command set of "hovering-rotation-acquisition-decomposition" is defined, realizing the standardization and automation of the direction finding process. (4) Intelligent prediction of interference type: A feature library based on spectrum noise floor and satellite signal is established, realizing the preliminary identification of suppression / deception interference.

[0100] This application has the following protections: (1) Product / system protection: A UAV-mounted GNSS / UHF integrated monitoring and direction finding system, specifically including the physical and data connection relationship between a dual-channel receiver integrating a sum-difference ratio network and the UAV. (2) Method protection: An airborne direction finding method for GNSS interference signals based on sum-difference ratio, specifically including a complete closed-loop logic of "rotation acquisition - synchronous reading of the nose pointing - real-time calculation of the sum-difference ratio - finding the minimum value of the ratio". (3) Algorithm / functional module protection: An automatic interference type identification method and an adaptive early warning threshold setting method based on signal feature analysis. (4) Interaction logic protection: An interactive process of "monitoring-early warning-confirmation-direction finding-feedback" linkage between airborne, remote controller and terminal.

[0101] The core technology of this application lies in the sum-difference amplitude direction finding system mounted on an unmanned aerial vehicle (UAV) and its operating method. This solution utilizes the open, unobstructed environment of the air to ensure the high sensitivity of the sum-difference amplitude algorithm for capturing weak signals. By replacing the electronic scanning of traditional fixed antenna arrays with UAV nose pointing, it greatly simplifies the antenna structure, reduces the load weight, and lowers the system calibration complexity, distinguishing it from existing ground-based direction finding equipment.

[0102] Currently, in the field of radio monitoring and direction finding, no superior technical solution has been found for direction finding of interference signals from UAV launch platforms compared to the "nose-pointing rotation + sum-difference amplitude comparison" method. Traditional correlation interferometer direction finding schemes require multi-element antennas and complex phase calibration networks, resulting in excessive weight and cost, making them difficult to implement on UAV payloads. Traditional directional antenna amplitude comparison direction finding schemes suffer from large direction finding accuracy errors due to insufficiently sharp antenna patterns.

[0103] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0104] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the above embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A direction-finding system for navigation system interference signals based on sum-difference amplitude ratio, characterized in that, The system includes: The ground remote control device is used to control the drone to take off to a preset altitude, hover and maintain stability, and control the drone to rotate autonomously; Unmanned aerial vehicles (UAVs) are used to scan the airspace by autonomously rotating in conjunction with an airborne monitoring and direction-finding platform. An airborne monitoring and direction finding platform, mounted on the UAV, is used to receive spectrum scanning tasks sent by the ground terminal, collect spectrum data and satellite signals in the navigation system frequency band, and transmit the spectrum data and satellite signals back to the ground terminal. The ground terminal is used to identify navigation system interference signals and trigger direction finding tasks, send the direction finding tasks to the airborne monitoring and direction finding platform, and send flight control commands to the UAV. The airborne monitoring and orientation platform is also used to acquire the current position and attitude information of the UAV, and to sample navigation system interference signals, calculate the sum and difference amplitude based on the sum and difference signals, and collect the current nose pointing azimuth angle of the UAV during the process of the UAV rotating at a constant speed based on the flight control command. The ground terminal is also used to calculate the direction finding results by employing an interpolation fitting algorithm based on the azimuth angle of the nose, the sum-difference ratio, the position information, and the attitude information.

2. The navigation system interference signal direction finding system based on sum-difference amplitude ratio according to claim 1, characterized in that, The airborne monitoring and direction finding platform includes: a dual-ridge horn antenna, a sum and difference feed network, and a receiver; The double-ridged horn antenna is installed at the bottom of the UAV mounting position. The output port of the double-ridged horn antenna is connected to the input port of the sum and difference feed network via an RF cable. The output port of the sum and difference feed network is connected to the channel input port of the receiver via an RF cable. The dual-ridge horn antenna is used to receive interference signals from the navigation system during the process of the UAV rotating at a constant speed based on the flight control command; The sum and difference feed network is used to send the navigation system interference signal to the receiver; The receiver is used to output the sum and difference signals in real time based on the interference signals of the navigation system, and to calculate the sum and difference amplitude based on the sum and difference signals, and to collect the current nose pointing azimuth angle of the UAV at a preset period. The receiver is also used to communicate with the flight controller of the UAV via a communication interface to obtain the current position and attitude information of the UAV.

3. The navigation system interference signal direction finding system based on sum-difference amplitude ratio according to claim 2, characterized in that, The receiver is also used to obtain spectrum data based on full-band spectrum scanning, perform signal analysis and extract information on whether the navigation system frequency signal is interfered with, and transmit the spectrum data and the satellite signal back to the ground terminal through the UAV image transmission link or a dedicated data transmission link.

4. The navigation system interference signal direction finding system based on sum-difference amplitude ratio according to claim 2, characterized in that, The receiver integrates a channel radio frequency front-end, a sum-difference amplitude ratio network, and a signal processing unit. The channel radio frequency front end is used to receive interference signals from the navigation system; The sum-difference amplitude comparison network is used to output the sum and difference signals in real time based on the interference signals of the navigation system. The signal processing unit is used to collect the current azimuth angle of the drone's nose at a preset period, and to synchronously calculate the sum-difference ratio at the current moment based on the sum and difference signals.

5. A method for direction finding of interference signals in a navigation system based on sum-difference amplitude ratio, characterized in that, The method is based on the navigation system interference signal direction finding system based on sum-difference amplitude ratio as described in any one of claims 1-4, and includes: The drone is controlled by a ground-based remote control device to ascend to a preset altitude, hover and remain stable, and then rotate autonomously. Based on unmanned aerial vehicles (UAVs), airspace scanning is performed through autonomous rotation in conjunction with an airborne monitoring and direction-finding platform. The airborne monitoring and direction finding platform receives spectrum scanning tasks sent by the ground terminal, collects spectrum data and satellite signals in the navigation system frequency band, and transmits the spectrum data and satellite signals back to the ground terminal. Based on the ground terminal, the navigation system interference signal identification and direction finding task triggering are performed, the direction finding task is sent to the airborne monitoring and direction finding platform, and flight control commands are sent to the UAV; Based on the airborne monitoring and orientation platform, the current position and attitude information of the UAV are obtained. During the process of the UAV rotating at a constant speed based on the flight control command, the navigation system interference signal is sampled, the sum and difference amplitude is calculated based on the sum and difference signals, and the current nose pointing azimuth angle of the UAV is collected. Based on the ground terminal, an interpolation fitting algorithm is used to calculate the direction finding results according to the azimuth angle of the nose, the sum-difference ratio, the position information, and the attitude information.

6. The navigation system interference signal direction finding method based on sum-difference amplitude ratio according to claim 5, characterized in that, The system receives spectrum scanning tasks sent by ground terminals based on an airborne monitoring and direction-finding platform, collects spectrum data and satellite signals in the navigation system frequency band, and transmits the spectrum data and satellite signals back to the ground terminal, including: Based on the spectrum data obtained by the receiver through full-band spectrum scanning, the navigation system frequency signal is analyzed and information on whether it is interfered with is extracted. The spectrum data and the satellite signal are then transmitted back to the ground terminal through the UAV image transmission link or a dedicated data transmission link.

7. The navigation system interference signal direction finding method based on sum-difference amplitude ratio according to claim 5, characterized in that, Navigation system interference signal identification, including: The spectrum data and satellite signals are subjected to adaptive noise floor calculation and template comparison. If the noise floor of the spectrum data in the frequency band rises beyond a preset threshold, or if the carrier-to-noise ratio of the satellite signal drops sharply, the corresponding spectrum data or satellite signal will be marked as the initial interference signal. Based on signal feature analysis, the initial interference signal is distinguished into suppression interference signal and deception interference signal.

8. The navigation system interference signal direction finding method based on sum-difference amplitude ratio according to claim 6, characterized in that, Based on the airborne monitoring and direction-finding platform, during the uniform rotation of the UAV based on the flight control commands, the system samples navigation system interference signals, calculates the sum-difference ratio based on the sum and difference signals, and collects the current nose-pointing azimuth angle of the UAV, including: Based on a dual-ridge horn antenna, the navigation system interference signal is received during the uniform rotation of the UAV based on the flight control command. Based on the sum-difference feed network, the navigation system interference signal is sent to the receiver; Based on the receiver, the system outputs sum and difference signals in real time based on the interference signals of the navigation system, calculates the sum and difference amplitude ratio based on the sum and difference signals, and collects the current nose pointing azimuth angle of the UAV at a preset period.

9. The method for direction finding of navigation system interference signals based on sum-difference amplitude ratio according to any one of claims 5-8, characterized in that, An interpolation fitting algorithm is used to calculate the direction finding results based on the nose pointing azimuth angle, sum-difference ratio, position information, and attitude information, including: Using the interpolation fitting algorithm, the target nose pointing azimuth angle corresponding to the minimum point of the sum-difference ratio is located; Based on the location information, attitude information, and the azimuth angle of the target aircraft's nose, a geographic direction line pointing to the interference source is generated; The geographic direction-finding line is the direction-finding result.

10. The navigation system interference signal direction finding method based on sum-difference amplitude ratio according to claim 9, characterized in that, The method further includes: Based on the ground terminal, during the direction finding process, a dynamic polar coordinate curve is generated in real time according to the sum and difference ratio and the azimuth angle of the aircraft head, and the geographic direction line is displayed.

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