Comprehensive navigation station obstacle analysis system based on multipath effect

Abstract

The invention relates to a comprehensive navigation station obstacle analysis system based on a multipath effect. The comprehensive navigation station obstacle analysis system comprises a geographical environment construction module, a navigation station modeling module, an airborne equipment modeling module, a route modeling module and an obstacle influence analysis module, the obstacle influence analysis module processing method comprises the following steps: step 1, establishing a signal propagation scene; 2, finding out a disturbed area; 3, performing ray tracing simulation; step 4, an analysis result display system finds a superposition path which interferes with the reception of the navigation signal based on a ray tracing method and the position of a main obstacle, displays an analysis result on a three-dimensional electronic map in combination with the position of the navigation station and an interfered area, and visually displays the transmission path of the navigation signal influenced by the obstacle; and step 5, providing a solution. The system can be used for optimizing and upgrading an existing navigation system, and problems in signal transmission are found, displayed and solved through simulation analysis.

Description

Technical Field

[0001] The present invention relates to obstacle analysis, and more specifically, to an integrated navigation station obstacle analysis system based on multipath effects. Background Art

[0002] When an aircraft is flying on a route, the surrounding terrain and obstacles will have a significant impact on the transmission of navigation signals. In particular, tall obstacles will cause signal reflection, refraction or scattering, which will lead to multipath effects. For example, signals propagated by different paths are superimposed at the receiving end, and destructive interference may cause signal loss or deviation. This problem may seriously affect the ranging and angle measurement accuracy of the navigation signal and endanger the flight safety of the aircraft. Therefore, if the above situation occurs, it is necessary to accurately find the obstacles that cause the impact and solve this problem through relevant means.

[0003] Searching for keywords such as “TACAN obstacle”, “microwave obstacle” and “precision radar obstacle” did not find any relevant technical content. This shows that there is no published patent or literature that systematically explores the technical solutions for these navigation stations when encountering obstacles.

[0004] When searching for "instrument landing obstacles", several related patents and papers were found. For example, patent CN202120119897.5 and patent CN201110191755.0 both involve technologies related to instrument landing systems and obstacles, but they are limited to discussing how to avoid obstacles and display obstacle information, and do not deeply analyze the specific impact of obstacles on navigation signals.

[0005] By searching "instrument landing obstacles" on CNKI, some relevant academic papers were obtained. Among them, "Simulation Research on Glide Beacon Operation Protection Area of ​​Instrument Landing System" discussed the operation protection area of ​​​​the glide beacon under a specific operation category, and proposed research methods and protection suggestions for the glide beacon site protection, aiming to provide supplementary and practical engineering demonstration for the glide beacon protection area data in Annex 10, Volume 1 of the Convention on International Civil Aviation. However, this study mainly focuses on the simulation of the glide beacon protection area, and does not deeply explore the specific impact of obstacles on the performance of the navigation system.

[0006] In addition, the "Study on Electromagnetic Coverage and Multipath Interference of Instrument Landing System" proposed a method for calculating the multipath effect of obstacles at different locations in the sensitive area based on the improved radiation field model, and pointed out the areas in the airport sensitive area where obstacles should be checked. Although the study analyzed the multipath effect and electromagnetic interference of obstacles, its research object is still limited to specific problems within the electromagnetic coverage range.

[0007] Another paper, "Study on the Impact of Typical Obstacles and Terrain on the Electromagnetic Environment of Instrument Landing Systems," explores the impact of obstacles around airport runways on signal reflections and analyzes the impact of obstacle reflections on navigation signal patterns. This study provides an in-depth analysis of how specific obstacles and terrain factors affect the electromagnetic environment, but does not go further to explore how these effects specifically interfere with the overall performance of the navigation system.

[0008] In summary, existing patents and literature mainly focus on the identification and avoidance of obstacles, as well as the impact of obstacles on the reflection of electromagnetic signals, but fail to accurately analyze the impact of obstacles on various navigation station signals, such as the refraction points and reflection points where obstacles interfere with the signals. Summary of the invention

[0009] In order to achieve the purpose of the present invention, a multi-navigation station obstacle detection and analysis system based on multipath effect is constructed to provide an effective method for comprehensively analyzing and resolving the impact of obstacles on navigation signals.

[0010] The technical solution adopted by the present invention is: a comprehensive navigation station obstacle analysis system based on multipath effect, including: a geographical environment construction module, a navigation station modeling module, an airborne equipment modeling module, a route modeling module and an obstacle impact analysis module; the obstacle impact analysis module processing method includes:

[0011] Step 1: Establish a signal propagation scenario;

[0012] Step 2: Find the disturbed area;

[0013] Step 3: ray tracing simulation;

[0014] Step 4: The analysis result display system finds the superposition path and main obstacle positions that interfere with the reception of navigation signals based on the ray tracing method, combines the navigation station position and the disturbed area to display the analysis results on a three-dimensional electronic map, and intuitively displays the transmission path of the navigation signal affected by obstacles;

[0015] Step 5: Provide solutions.

[0016] Preferably, the establishment of the signal propagation scenario includes: constructing a three-dimensional propagation scenario of the navigation signal based on the geographic information (digital elevation model, topographic map) in the system database. The user adds and edits the terrain or object contours in the scenario according to the actual terrain and building distribution, and sets its height attribute to achieve a true simulation of the signal transmission environment. The propagation scenario construction formula is as follows:

[0017] P(x,y,z)=G(x,y)+H(x,y)

[0018] in:

[0019] P(x, y, z): is the spatial coordinate of a point in the propagation scene, and z is the total height of the point;

[0020] G(x, y): terrain height;

[0021] H(x, y): height of the ground feature.

[0022] Preferably, the ray tracing simulation includes: based on the path between the starting point and the disturbed point, using a ray tracing method to calculate the loss of different propagation paths of the signal, wherein an accurate signal propagation model and analysis results are provided, and the specific steps are as follows:

[0023] S1: map data preprocessing;

[0024] S2: Determine the effective tracing path and select the appropriate ray tracing model;

[0025] S3: Calculate the received power and calculate the total received power based on all valid paths

[0026] P i =P t +G t +G r -Li

[0027] in:

[0028] P t : Initial power of the transmitter;

[0029] G t : The gain of the transmitting antenna in the direction of the path;

[0030] G r : The gain of the receiving antenna in the direction of the path;

[0031] Li: The propagation loss of the path, which is the sum of the losses of direct, reflected and diffraction propagation modes;

[0032] S4: Output the propagation loss and received power of each effective path and the three-dimensional coordinates where reflection and diffraction occur.

[0033] Preferably, the map data preprocessing includes:

[0034] S101: profile information acquisition: according to the longitude and latitude coordinates of the transmitting end and the receiving end, the connecting line between the transmitting end and the receiving end is discretized in the rasterized geographic information elevation map to obtain the elevation of the discrete points;

[0035] S102: Establishing a visible surface list: Numbering the surfaces, judging the visible surfaces of the transmitting end through a visibility judgment method and a visible range judgment method, and storing the visible surfaces and visible ranges;

[0036] The visible surface of the receiving end is determined by the visibility determination method and the visible range determination method, and the visible surface and the visible range are stored;

[0037] For any transmitting point T and two points P on the surface to be judged 1 and P 2 , which can be obtained by the external normal vector Make visible surface judgment:

[0038]

[0039] If the visible surface judgment formula is satisfied, the surface is visible;

[0040] The visible range is calculated as follows:

[0041] Initialize the maximum slope and the previous slope

[0042] Starting from the second face, traverse all faces and calculate the slope of the current face

[0043] If the current slope is greater than the maximum slope, and the maximum slope is greater than the previous slope, the intersection calculation is used to obtain the K value starting from the launch point. SlpoeMax The intersection of the slope straight line and the current line segment, and the latter part is the visible range;

[0044] S103: Establishing a visible wedge list: Identify the local area by comparing the heights of discrete points; number the wedges, determine the visible wedges at the transmitting end by the slope, and store them; determine the visible wedges at the receiving end by the slope of the ray emitted by the receiving end, and store them.

[0045] Preferably, including:

[0046] S201: Determine the line of sight: determine whether the transmitter and receiver have line of sight based on the slope. If so, calculate the propagation loss based on the line of sight propagation loss formula.

[0047] S202: The reflection ray tracing module uses the previously stored transmitter, receiver, and visible surface table as a basis and is divided into several situations:

[0048] S2021: Calculate one reflection: Find the visible surface of the transmitter and receiver. For the common visible surface, obtain the mirror point of the transmitting point about the visible surface, connect the mirror point and the receiving point, and the intersection with the visible surface is the reflection point. Determine whether the reflection point is within the visible range of the transmitter and receiver. If so, it means that the transmitting point is valid and the reflection path is valid. Obtain the reflection path and further calculate the propagation delay, propagation loss, and receiving power of the path. If there is no one reflection path, consider the second reflection.

[0049] S2022: Calculate secondary reflection: traverse the visible surface of the transmitting point, obtain the mirror point for each visible surface, traverse each visible surface of the receiving point, first roughly determine whether the two surfaces are visible through the normal vector, if visible, obtain the mirror point of the receiving visible surface, the intersection of the line connecting the two mirror points and the visible surface is the two reflection points, judge the validity of the transmitting point, including whether it is in the visible area of ​​the transmitting and receiving points, and whether the reflection line of the visible surface of the transmitting end is valid and whether it is blocked;

[0050] S2023: If the ray meets one of the above conditions, it is a valid reflection path, and the propagation loss of the reflection path can be obtained by reflection:

[0051]

[0052] in:

[0053] λ is the wavelength;

[0054] l is the transmission distance;

[0055] f is the interaction loss each time, which is the reflection loss here;

[0056] α is the incident angle of the ray;

[0057] i is the number of reflections. Each reflection can take a fixed value or be accurately calculated based on the reflection theorem and the electrical parameters of the ground.

[0058] n is the number of effective multipaths;

[0059] g t is the directional gain of the transmitting antenna;

[0060] S203: Diffraction ray tracing module, searches for visible diffraction wedges at the transmitting point, searches for visible diffraction wedges at the receiving point, finds the diffraction wedges visible to both the transmitter and the receiver, obtains the diffraction path (diffraction angle and diffraction loss) according to the diffraction theorem, and calculates the path loss:

[0061]

[0062] in:

[0063] λ is the wavelength;

[0064] l is the transmission distance;

[0065] f is the interaction loss each time, which is the reflection loss here;

[0066] α is the incident angle of the ray;

[0067] i is the number of diffraction, and each diffraction can take a fixed value;

[0068] n is the number of effective multipaths;

[0069] g t is the directional gain of the transmitting antenna.

[0070] Preferably, the signal propagation path is simulated using the ray tracing model and antenna pattern, and the main path signal strength P at each point on the route is calculated. m , phase φ m And the strength of the multipath signal P i , phase φ i , the disturbed area is determined by the following formula:

[0071]

[0072] Where P is the path signal strength, which is calculated according to the path received power formula;

[0073] P m is the main path signal strength;

[0074] P i is the signal strength on the i-th path;

[0075] φ is the phase, calculated according to the phase formula:

[0076] φ m is the main path phase;

[0077] φ i is the phase on the i-th path;

[0078] λ is the wavelength;

[0079] D is the signal transmission distance;

[0080] φ 0 The initial phase of the signal is usually determined by the modulation method of the transmitting source or the antenna characteristics. In the wireless propagation model, if the initial phase is not explicitly specified, it is usually set to 0.

[0081] j is the imaginary unit;

[0082] e j The phase factor of the path is processed in complex form;

[0083] If ΔP exceeds a certain threshold, it is considered that the signal in this area is disturbed.

[0084] Preferably, the geographic environment construction module provides high-precision geographic environment data support for navigation signal propagation analysis and obstacle shadows through three-dimensional modeling of the airport and its surrounding environment.

[0085] Compared with the prior art, the present invention has the following beneficial effects:

[0086] The system can be used to optimize and upgrade existing navigation systems. It can discover, demonstrate and solve problems in signal transmission through simulation analysis. It can select the optimal location through simulation analysis of signal coverage and interference, and provide reliable technical support for the site selection and optimization of navigation equipment. It can build a variety of navigation station obstacle detection and analysis systems based on multipath effects, provide technical support for obstacle avoidance and signal optimization, and thus improve the reliability and accuracy of the navigation system. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Figure 1 This is a control flow chart of the obstacle impact analysis module of the present invention;

[0088] Figure 2 It is a data flow chart of the obstacle impact analysis function of the present invention;

[0089] Figure 3 It is the overall structure diagram of the geographic information three-dimensional model of the present invention;

[0090] Figure 4 This is the operation page for adding obstacles in the present invention;

[0091] Figure 5 It is a schematic diagram showing the obstacle impact analysis results of the present invention;

[0092] Figure 6 When the route of the present invention is a 3 degree glide angle, the obstacle impact analysis is displayed on the side.

[0093] Figure 7 When the route of the present invention is a circular flight, obstacles affect the bird's-eye view display.

[0094] Figure 8 When the route of the present invention is a circular flight, obstacles affect the side display.

[0095] Fig. 9 The obstacle affects the side display when the route of the present invention is five-side takeoff and landing DETAILED DESCRIPTION

[0096] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0097] Example:

[0098] Figures 1 to 9As shown, the present invention provides a technical solution: a comprehensive navigation station obstacle analysis system based on multipath effect, including: a geographical environment construction module, a navigation station modeling module, an airborne equipment modeling module, a route modeling module and an obstacle impact analysis module.

[0099] Among them, the geographic environment construction module aims to provide high-precision geographic environment data support for navigation signal propagation analysis and obstacle impact research through three-dimensional modeling of the airport and its surrounding environment. This module integrates multi-source data and combines user interactive modeling to accurately restore the terrain and obstacle characteristics around the airport.

[0100] Detailed description of main functions:

[0101] 1. Fusion of multi-source data to generate a 3D geographic environment model

[0102] Satellite imagery data: High-resolution satellite imagery is used to provide an intuitive visualization basis for surface texture and obstacle contours.

[0103] Digital Elevation Model (DEM): Obtain terrain height data to describe terrain undulations. A 30-meter precision DEM is used for the 40-kilometer range around the airport, and a 15-meter precision DEM is used for sensitive areas (5 km × 5 km). Supported DEM formats include: Img format, Tiff format, USGS format, etc.

[0104] Obstacle modeling: For obstacles that are newly added or not included in the geographic information database, users can use interactive tools to complete the obstacle contour drawing and height assignment, realizing dynamic expansion and real-time updating of the geographic environment.

[0105] 2. User interactive modeling obstacles

[0106] Step 1: Outline drawing: the user selects the actual location of the obstacle in the system interface and draws its main outline in combination with the geographic satellite image. Supported shape types include: cylinder, polygon, prism, or manually customized shape.

[0107] Step 2: Type and material selection: users can select the corresponding type (such as hills, buildings, bungalows, trees, etc.) and material information (such as glass, cement, wood, etc.) for the obstacle. The material information will be used to calculate the reflection and absorption characteristics of the obstacle to the navigation signal.

[0108] Step 3: Height assignment. The system supports users to set the actual ground height for newly added obstacles to ensure that the model accurately reflects the impact of obstacles on the signal propagation path.

[0109] 3. Support ray tracing and signal propagation analysis

[0110] After the geographic environment model is generated, it can be directly used as the input of the ray tracing algorithm to provide basic data of terrain and obstacles for multipath effect analysis. The system can accurately simulate the signal propagation path, calculate the reflection points, refraction points and obstruction positions, and quantify the specific interference of obstacles on the signal.

[0111] Main technical features:

[0112] Flexibility and dynamic updates: Support users to dynamically add new obstacles that are not included, and further optimize the model expression through material and height settings.

[0113] Compatible with multiple formats: The system supports a variety of DEM and satellite image formats, adapts to a variety of geographic data sources, and facilitates data import and integration.

[0114] Through the geographic environment building blocks, the system is able to support the following key functions:

[0115] 1. Calculation of the impact of terrain on radio wave propagation: Based on digital elevation model (DEM) data, analyze the impact of terrain undulations on signal loss during radio wave propagation. In the propagation of radio waves, the rays may experience direct radiation, reflection, scattering, transmission or diffraction, and different propagation modes will cause different degrees of signal attenuation. The specific description is as follows:

[0116] (a) Calculation of radio wave transmission distance

[0117] Assume that the terrain height set is Z, and the three-dimensional coordinates of the transmitter and receiver are (x 1 ,y 1 , z 1 ) and (x 2 ,y 2 , z 2 ), where z 1 , z 2 ∈Z. The radio wave transmission distance d can be calculated using the Euclidean distance formula between two points:

[0118]

[0119] (b) Calculation of line-of-sight path loss:

[0120] When the ray path is in sight, its propagation loss PL can be calculated based on the formula for free space propagation of radio waves, combining the path loss exponent p and the wavelength λ:

[0121]

[0122] Where PL is the current propagation loss in dB, λ is the wavelength, p is the path loss exponent, and d is the transmission distance.

[0123] Through these calculations, the complex effects of terrain undulations and obstacles on radio wave propagation can be fully evaluated, providing accurate loss parameter support for subsequent ray tracing and signal analysis.

[0124] 2. Visibility determination during ray tracing calculation: Use the distance and height between the transmitter and the receiver to determine whether there is any obstruction to ensure accurate simulation of the signal path. The specific description is as follows:

[0125] Assume that the transmitter and receiver are located at points (x 1 ,y 1 , z 1 ) and (x 2 ,y 2 , z 2 ). In the direct judgment, the transmitting end is regarded as the source point, and the line connecting it and the receiving end is regarded as the x-axis. The height direction of the transmitting end is regarded as the y-axis to establish a two-dimensional profile:

[0126] The coordinates of the transmitting end are expressed as (0, h 1 ), where h 1 is the altitude of the launch point;

[0127] The receiving end coordinates are expressed as (d, h 2 ), where h 2 is the altitude of the receiving point, d is the horizontal distance between the two points,

[0128] In the path profile, the coordinates of discrete points are expressed as (d i ,h i ).

[0129] Calculate the slope:

[0130]

[0131] If k < k tr , then it is considered that the sender and receiver have visual communication, otherwise the sender and receiver do not have visual communication.

[0132] 3. Building height adjustment: By combining the height information input in obstacle modeling with the terrain height (DEM), the absolute height of the building is accurately determined. The absolute height of the building is

[0133] H total =H ground +H building

[0134] Among them, H ground is the terrain height, from DEM data, H building is the building height.

[0135] The navigation station modeling module systematically constructs the mobile position navigation database, which is convenient for users to query, create, modify and save various parameters of the navigation station and characterize the transmission and reception characteristics of the navigation station.

[0136] These include:

[0137] 1. Transmitter: Model the operating mode, characteristics, and capabilities of the transmitting equipment based on the relevant parameters of the navigation station, such as frequency, modulation type, occupied bandwidth, power, frequency characteristics, and spurious emission attenuation (harmonic attenuation, intermodulation attenuation).

[0138] 2. Antenna: This type of working component is used to characterize the radiation capability of various antennas for electromagnetic waves and the instantaneous radiation state. The main function is to simulate the process of the antenna radiating the input electromagnetic wave signal into space. The tentative subcategories mainly include: mechanical scanning antenna, semi-mechanical and semi-electronic scanning antenna, phase scanning antenna, frequency scanning antenna, active array, passive array, etc. Depending on the category, the main parameters include: frequency characteristics, beamforming time, mechanical limit, electronic scanning limit, beam shape, gain, polarization mode, etc. In addition to supporting users to manually edit the various parameters of the antenna pattern, the system also supports the import and use of external antenna modeling software, such as: HFSS constructed antenna model.

[0139] 3. Feeder: Characterizes the energy loss caused when signals of different frequencies are transmitted between the transmitter and the antenna or between the antenna and the receiver, such as frequency, impedance, attenuation characteristic curve, etc.

[0140] Airborne equipment modeling module, the system simulates the signal processing processes of the real navigation signal receiver, such as reception, amplification, and detection, by modeling the airborne equipment.

[0141] Its input mainly comes from working components such as antennas. Its output can be directly used as the final output of equipment and equipment. When it is necessary to be responsible for the processing process, its output can be used for various working components such as signal processing, signal measurement, and signal sorting.

[0142] In addition to modeling common parameters such as frequency, power, altitude, bandwidth, antenna gain, etc., the system provides airborne equipment models that meet the simulation analysis of different types of navigation signals for users to use in modeling, as the airborne equipment working modes of different types of navigation stations are different. The characteristic parameters of airborne equipment modeling for different navigation signals are as follows:

[0143] TACAN system:

[0144] Interrogator modeling: Model the interrogator based on the parameters of the bell pulse emitted by the interrogator, including the analog sampling rate, bell pulse rise time, bell pulse fall time, bell pulse half-width, etc.

[0145] Transponder modeling: Model the transponder based on the parameters of the bell pulse emitted by the interrogator, including the analog sampling rate, bell pulse rise time, bell pulse fall time, bell pulse half-width, etc.

[0146] Medium wave signal receiving equipment:

[0147] The modeling of the medium wave signal receiving equipment is mainly focused on the two antennas mounted on it: the loop antenna and the omnidirectional antenna.

[0148] Loop antenna: mainly models parameters such as receiving gain, noise coefficient, and antenna horizontal direction.

[0149] Omnidirectional antenna: mainly models parameters such as receiving gain, noise coefficient, and antenna height.

[0150] Instrument Landing System Receiver:

[0151] The modeling of the instrument landing system receiving equipment is divided into two categories: localizer beacon and glide path beacon. Since the two work in the same way, the modeling parameters remain consistent, including: operating frequency, channel bandwidth, sensitivity, receiver temperature, noise coefficient, receiving gain, etc.

[0152] Microwave landing system receiving equipment:

[0153] The modeling of the microwave landing system receiving equipment is divided into two categories: azimuth station and elevation station. Since the two work in the same way, the modeling parameters remain consistent, including: operating frequency, channel bandwidth, sensitivity, receiver temperature, noise coefficient, receiving gain, etc.

[0154] In the route modeling module, the system's internal database stores several commonly used flight routes, such as the 3-degree glide path, the final takeoff and landing path, etc. Users can directly call them during simulation calculations, and the flight route will automatically match the center point, direction, length, etc. of the currently selected runway. In addition, the system also supports users to customize routes for different flight scenarios. Users can choose straight lines, broken lines, arcs, circles, etc. to manually plan flight routes.

[0155] The obstacle impact analysis module simulates and analyzes the propagation of navigation signals on the aircraft route, identifies abnormal areas of signal field strength changes, and combines three-dimensional profiles and ray tracing to determine the interference of multipath effects on the main path signal. It traces the signal propagation path, finds the multipath paths that are superimposed on the main path and cause serious interference to the signal, locates key obstacles, and proposes corresponding solutions.

[0156] The obstacle impact analysis module processing methods include:

[0157] Step 1: Establish a signal propagation scenario;

[0158] Establish a signal propagation scenario. Based on the geographic information (digital elevation model, topographic map) in the system database, build a three-dimensional propagation scenario of the navigation signal. Users can add and edit the terrain or object contours in the scenario according to the actual terrain and building distribution, and set their height attributes to achieve a true simulation of the signal transmission environment. The propagation scenario construction formula is as follows:

[0159] P(x,y,z)=G(x,y)+H(x,y)

[0160] in:

[0161] P(x, y, z): is the spatial coordinate of a point in the propagation scene, and z is the total height of the point;

[0162] G(x, y): terrain height;

[0163] H(x, y): height of the ground feature.

[0164] Step 2: Find the disturbed area;

[0165] Using the ray tracing model and antenna pattern, the signal propagation path is simulated and the main path signal strength R at each point on the route is calculated. m , phase φ m And the strength of the multipath signal P i , phase φ i , the disturbed area is determined by the following formula:

[0166]

[0167] Where P is the path signal strength, which is calculated according to the path received power formula;

[0168] P m is the main path signal strength;

[0169] P i is the signal strength on the i-th path;

[0170] φ is the phase, calculated according to the phase formula:

[0171] φ m is the main path phase;

[0172] φ i is the phase on the i-th path;

[0173] λ is the wavelength;

[0174] D is the signal transmission distance;

[0175] φ 0The initial phase of the signal is usually determined by the modulation method of the transmitting source or the antenna characteristics. In the wireless propagation model, if the initial phase is not explicitly specified, it is usually set to 0.

[0176] j is the imaginary unit;

[0177] The phase factor of the ej path is processed in complex form;

[0178] If ΔP exceeds a certain threshold, it is considered that the signal in this area is disturbed.

[0179] Step 3: ray tracing simulation;

[0180] Ray tracing simulation uses ray tracing method to calculate the loss of different propagation paths of signals based on the path between the starting point and the disturbed point. It provides accurate signal propagation model and analysis results. The specific steps are as follows:

[0181] S1: map data preprocessing;

[0182] Among them, S101: profile information acquisition: according to the longitude and latitude coordinates of the sending end and the receiving end, the connecting line between the sending end and the receiving end is discretized in the rasterized geographic information elevation map to obtain the elevation of the discrete points;

[0183] S102: Establishing a visible surface list: Numbering the surfaces, judging the visible surfaces of the transmitting end through a visibility judgment method and a visible range judgment method, and storing the visible surfaces and visible ranges;

[0184] The visible surface of the receiving end is determined by the visibility determination method and the visible range determination method, and the visible surface and the visible range are stored;

[0185] For any transmitting point T and two points P on the surface to be judged 1 and P 2 , which can be obtained by the external normal vector Make visible surface judgment:

[0186]

[0187] If the visible surface judgment formula is satisfied, the surface is visible;

[0188] The visible range is calculated as follows:

[0189] Initialize the maximum slope and the previous slope

[0190] Starting from the second face, traverse all faces and calculate the slope of the current face

[0191] If the current slope is greater than the maximum slope, and the maximum slope is greater than the previous slope, the intersection calculation is used to obtain the K value starting from the launch point.SlpoeMax The intersection of the slope straight line and the current line segment, and the latter part is the visible range;

[0192] S103: Establishing a visible wedge list: Identify the local area by comparing the heights of discrete points; number the wedges, determine the visible wedges at the transmitting end by the slope, and store them; determine the visible wedges at the receiving end by the slope of the ray emitted by the receiving end, and store them.

[0193] S2: Determine the effective tracing path and select the appropriate ray tracing model;

[0194] Wherein, S201: judging the line of sight, judging whether the transmitter and receiver have line of sight according to the slope, and if so, calculating the propagation loss according to the line of sight propagation loss formula;

[0195] S202: The reflection ray tracing module uses the previously stored transmitter, receiver, and visible surface table as a basis and is divided into several situations:

[0196] S2021: Calculate one reflection: Find the visible surface of the transmitter and receiver. For the common visible surface, obtain the mirror point of the transmitting point about the visible surface, connect the mirror point and the receiving point, and the intersection with the visible surface is the reflection point. Determine whether the reflection point is within the visible range of the transmitter and receiver. If so, it means that the transmitting point is valid and the reflection path is valid. Obtain the reflection path and further calculate the propagation delay, propagation loss, and receiving power of the path. If there is no one reflection path, consider the second reflection.

[0197] S2022: Calculate secondary reflection: traverse the visible surface of the transmitting point, obtain the mirror point for each visible surface, traverse each visible surface of the receiving point, first roughly determine whether the two surfaces are visible through the normal vector, if visible, obtain the mirror point of the receiving visible surface, the intersection of the line connecting the two mirror points and the visible surface is the two reflection points, judge the validity of the transmitting point, including whether it is in the visible area of ​​the transmitting and receiving points, and whether the reflection line of the visible surface of the transmitting end is valid and whether it is blocked;

[0198] S2023: If the ray meets one of the above conditions, it is a valid reflection path, and the propagation loss of the reflection path can be obtained by reflection:

[0199]

[0200] in:

[0201] λ is the wavelength;

[0202] l is the transmission distance;

[0203] f is the interaction loss each time, which is the reflection loss here;

[0204] α is the incident angle of the ray;

[0205] i is the number of reflections. Each reflection can take a fixed value or be accurately calculated based on the reflection theorem and the electrical parameters of the ground.

[0206] n is the number of effective multipaths;

[0207] g t is the directional gain of the transmitting antenna;

[0208] S203: Diffraction ray tracing module, searches for visible diffraction wedges at the transmitting point, searches for visible diffraction wedges at the receiving point, finds the diffraction wedges visible to both the transmitter and the receiver, obtains the diffraction path (diffraction angle and diffraction loss) according to the diffraction theorem, and calculates the path loss:

[0209]

[0210] in:

[0211] λ is the wavelength;

[0212] l is the transmission distance;

[0213] f is the interaction loss each time, which is the reflection loss here;

[0214] α is the incident angle of the ray;

[0215] i is the number of diffraction, and each diffraction can take a fixed value;

[0216] n is the number of effective multipaths;

[0217] g t is the directional gain of the transmitting antenna.

[0218] S3: Calculate the received power and calculate the total received power based on all valid paths

[0219] P i =P t +G t +G r -Li

[0220] in:

[0221] P t : Initial power of the transmitter;

[0222] G t : The gain of the transmitting antenna in the direction of the path;

[0223] G r : The gain of the receiving antenna in the direction of the path;

[0224] Li: The propagation loss of the path, which is the sum of the losses of direct, reflected and diffraction propagation modes;

[0225] S4: Output the propagation loss and received power of each effective path and the three-dimensional coordinates where reflection and diffraction occur.

[0226] Step 4: The analysis result display system finds the superposition path and main obstacle positions that interfere with the reception of navigation signals based on the ray tracing method, combines the navigation station position and the disturbed area to display the analysis results on a three-dimensional electronic map, and intuitively displays the transmission path of the navigation signal affected by obstacles;

[0227] The spatial distribution of the disturbed area, multipath paths and obstacles is intuitively displayed through a three-dimensional electronic map, and the actual transmission path of the navigation signal to the disturbed point (multipath signal convergence point) due to reflection and refraction of obstacles during the transmission process is given.

[0228] Step 5: Provide solutions.

[0229] Based on the analysis of the impact of obstacles on signal propagation, the module proposes solutions to optimize navigation signal transmission, such as:

[0230] Adjust the flight altitude to avoid the area affected by obstacles.

[0231] Lower or remove critical obstructions.

[0232] Optimize antenna patterns to reduce signal strength on interfering paths.

[0233] The embodiments of the present invention disclose preferred embodiments, but are not limited thereto. A person skilled in the art can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. However, as long as they do not deviate from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A comprehensive navigation station obstacle analysis system based on multipath effect, characterized in that: include: Geographic environment construction module, navigation station modeling module, airborne equipment modeling module, route modeling module and obstacle impact analysis module; The obstacle impact analysis module processing method includes: Step 1: Establish a signal propagation scenario; Step 2: Find the disturbed area; Step 3: ray tracing simulation; Step 4: The analysis result display system finds the superposition path and main obstacle positions that interfere with the reception of navigation signals based on the ray tracing method, combines the navigation station position and the disturbed area to display the analysis results on a three-dimensional electronic map, and intuitively displays the transmission path of the navigation signal affected by obstacles; Step 5: Provide solutions.

2. The integrated navigation station obstacle analysis system based on multipath effect according to claim 1 is characterized in that: The establishing of the signal propagation scenario includes: Based on the geographic information in the system database, a three-dimensional propagation scenario of the navigation signal is constructed. According to the actual terrain and building distribution, the user can add and edit the terrain or object contours in the scenario and set their height attributes to achieve a true simulation of the signal transmission environment. The propagation scenario construction formula is as follows: P(x,y,z)=G(x,y)+H(x,y) in: P(x, y, z): is the spatial coordinate of a point in the propagation scene, and z is the total height of the point; G(x, y): terrain height; H(x, y): height of the ground feature.

3. The integrated navigation station obstacle analysis system based on multipath effect according to claim 1, characterized in that: The ray tracing simulation includes: Based on the path between the starting point and the disturbed point, the ray tracing method is used to calculate the loss of different propagation paths of the signal, wherein an accurate signal propagation model and analysis results are provided. The specific steps are as follows: S1: map data preprocessing; S2: Determine the effective tracing path and select the appropriate ray tracing model; S3: Calculate the received power and calculate the total received power based on all valid paths P i =P t +G t +G r -Li in: P t : Initial power of the transmitter; G t : The gain of the transmitting antenna in the direction of the path; G r : The gain of the receiving antenna in the direction of the path; Li: The propagation loss of the path, which is the sum of the losses of direct, reflected and diffraction propagation modes; S4: Output the propagation loss and received power of each effective path and the three-dimensional coordinates where reflection and diffraction occur.

4. The integrated navigation station obstacle analysis system based on multipath effect according to claim 3 is characterized in that: The map data preprocessing includes: S101: profile information acquisition: according to the longitude and latitude coordinates of the transmitting end and the receiving end, the connecting line between the transmitting end and the receiving end is discretized in the rasterized geographic information elevation map to obtain the elevation of the discrete points; S102: Establishing a visible surface list: Numbering the surfaces, judging the visible surfaces of the transmitting end through a visibility judgment method and a visible range judgment method, and storing the visible surfaces and visible ranges; Determine the visible surface of the receiving end through the visibility determination method and the visible range determination method, and store the visible surface and the visible range; For any transmitting point T and two points P1 and P2 on the surface to be judged, the external normal vector Make visible surface judgment: If the visible surface judgment formula is satisfied, the surface is visible; The visible range is calculated as follows: Initialize the maximum slope and the previous slope Starting from the second face, traverse all faces and calculate the slope of the current face S103: Establishing a visible wedge list: Identify the local area by comparing the heights of discrete points; number the wedges, determine the visible wedges at the transmitting end by the slope, and store them; determine the visible wedges at the receiving end by the slope of the ray emitted by the receiving end, and store them.

5. The integrated navigation station obstacle analysis system based on multipath effect according to claim 4 is characterized in that: include: S201: Determine the line of sight: determine whether the transmitter and receiver have line of sight based on the slope. If so, calculate the propagation loss based on the line of sight propagation loss formula. S202: The reflection ray tracing module uses the previously stored transmitter, receiver, and visible surface table as a basis and is divided into several situations: S2021: Calculate one reflection: Find the visible surface of the transmitter and receiver. For the common visible surface, obtain the mirror point of the transmitting point with respect to the visible surface. Connect the mirror point and the receiving point. The intersection with the visible surface is the reflection point. Determine whether the reflection point is within the visible range of the transmitter and receiver. If so, it means that the transmitting point is valid and the reflection path is valid. Obtain the reflection path and further calculate the propagation delay, propagation loss, and receiving power of the path. If there is no primary reflection path, consider the secondary reflection; S2022: Calculate secondary reflection: traverse the visible surface of the emission point, obtain the mirror point for each visible surface, traverse each visible surface of the receiving point, first roughly determine whether the two surfaces are visible through the normal vector, if visible, obtain the mirror point of the receiving visible surface, the intersection of the line connecting the two mirror points and the visible surface is the two reflection points, and determine the validity of the emission point; S2023: If the ray meets one of the above conditions, it is a valid reflection path, and the propagation loss of the reflection path can be obtained by reflection: in: λ is the wavelength; l is the transmission distance; f is the interaction loss each time, which is the reflection loss here; α is the incident angle of the ray; i is the number of reflections. Each reflection can take a fixed value or be accurately calculated based on the reflection theorem and the electrical parameters of the ground. n is the number of effective multipaths; g t is the directional gain of the transmitting antenna; S203: Diffraction ray tracing module, searches for visible diffraction wedges at the transmitting point, searches for visible diffraction wedges at the receiving point, finds the diffraction wedges visible to both the transmitter and the receiver, obtains the diffraction path (diffraction angle and diffraction loss) according to the diffraction theorem, and calculates the path loss: in: λ is the wavelength; l is the transmission distance; f is the interaction loss each time, which is the reflection loss here; α is the incident angle of the ray; i is the number of diffraction, and each diffraction can take a fixed value; n is the number of effective multipaths; g t is the directional gain of the transmitting antenna.

6. The integrated navigation station obstacle analysis system based on multipath effect according to claim 3 is characterized in that: Using the ray tracing model and antenna pattern, the signal propagation path is simulated and the main path signal strength P at each point on the route is calculated. m , phase φ m And the strength of the multipath signal P i , phase φ i , the disturbed area is determined by the following formula: Where P is the path signal strength, which is calculated according to the path received power formula; P m is the main path signal strength; P i is the signal strength on the i-th path; φ is the phase, calculated according to the phase formula: φ m is the main path phase; φ i is the phase on the i-th path; λ is the wavelength; D is the signal transmission distance; φ0 is the initial phase of the signal, which is usually determined by the modulation method of the transmitter or the antenna characteristics. In the wireless propagation model, if the initial phase is not explicitly specified, it is usually set to 0. j is the imaginary unit; e j The phase factor of the path is processed in complex form; If ΔP exceeds a certain threshold, it is considered that the signal in this area is disturbed.

7. The integrated navigation station obstacle analysis system based on multipath effect according to claim 1, characterized in that: The geographic environment construction module provides high-precision geographic environment data support for navigation signal propagation analysis and obstacle shadows by three-dimensional modeling of the airport and its surrounding environment.

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