A method for evaluating and verifying the signal quality of TACAN ground beacon

Abstract

The present invention discloses a method for evaluating and verifying the quality of TACAN ground beacon signals, which belongs to the field of flight verification technology. The method aims to solve the existing problems that the ground beacon signal strength cannot be adjusted, resulting in poor overall adaptability, affecting the stability of signal transmission, and being unable to determine the accuracy of the verification detection structure; and being unable to detect the ground beacon signal based on the flight signal, thereby evaluating the quality of the ground beacon signal. The signal strength is adjusted by amplitude modulation, and is flexibly adjusted according to the verification test to ensure the accuracy of the verification detection structure. The ground beacon station signal can be adjusted according to the test area, environment, and project, and the antenna coefficient can be accurately measured. Models under different flight attitudes are established to correct the impact on the signal strength. The difference between the two groups of signals is evaluated, and the noise content in the signal is used to make a more detailed evaluation of the signal quality, thereby improving the quality of the evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of flight calibration, and in particular to a method for evaluating and calibrating the quality of a TACAN ground beacon signal. Background Art

[0002] Flight verification is the process of inspecting and evaluating the quality and tolerances of space signals from various navigation, radar, and communications equipment, as well as airport arrival and departure procedures, to ensure flight safety, using a flight verification aircraft equipped with specialized verification equipment. This process then produces a flight verification report based on the results of the inspection and evaluation. The basic principle is to use an aircraft equipped with appropriate receiving equipment to fly along a prescribed trajectory. The onboard receiving equipment simultaneously records the navigation signal and the position signal. The actual signal received by the onboard equipment is compared with the theoretical value at that point to determine the verification error.

[0003] In the prior art, Chinese patent publication number CN114200387B discloses a method for evaluating the quality of TACAN ground beacon signals. This patent uses data information obtained through inversion and reconstruction to calculate channel information such as error, curvature, and jitter. Finally, it evaluates whether the navigation parameters meet the tolerance requirements and determines whether the TACAN signal field is safe and usable.

[0004] However, during the flight verification process, the following defects exist:

[0005] 1. The ground beacon signal strength cannot be adjusted, resulting in poor overall adaptability, affecting signal transmission stability and uncertainty about the accuracy of the calibration detection structure;

[0006] 2. Secondly, it is impossible to detect the ground beacon signal based on the flight signal, and thus evaluate the quality of the ground beacon signal. Summary of the Invention

[0007] The object of the present invention is to provide a method for evaluating and verifying the quality of TACAN ground beacon signals. The method of calculating the phase difference between the reference group pulse and the envelope zero point phase to obtain TACAN azimuth information is feasible, can obtain accurate TACAN azimuth information, improve the stability of model reception, facilitate signal reception, adjust its signal strength through amplitude modulation, flexibly adjust according to the verification test, ensure the accuracy of the verification detection structure, and can adjust the ground beacon station signal according to the test area, environment and project to improve overall adaptability and increase detection flexibility. It accurately measures the antenna coefficient and establishes models under different flight attitudes to correct the impact on signal strength. Evaluation is performed based on the difference between the two groups of signals. Based on the noise content in the signal, the signal quality can be more carefully evaluated to improve the quality of the evaluation. In addition, based on the different frequency harmonic components, the corresponding noise is removed, and the signal quality can be further improved and enhanced to solve the problems raised in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for evaluating and verifying the quality of a TACAN ground beacon signal includes a TACAN signal processing system and a ground management system;

[0010] The ground management system determines the position and distance of the TACAN ground beacon station according to the verification plan, so as to perform the TACAN ground beacon signal test during the flight. The TACAN signal processing system is arranged in the UAV flight system, and the TACAN signal processing system is connected to the ground management system;

[0011] The TACAN signal processing system in the UAV collects the pulse electromagnetic wave signals emitted by the TACAN ground beacon station, stores the collected data, and transmits it to the ground management system for processing and evaluation.

[0012] Furthermore, the TACAN signal processing system and the TACAN ground beacon station constitute the TACAN navigation system, whose azimuth measurement is achieved by rotating the ground beacon antenna to obtain a rotating multi-lobe pattern to provide azimuth information. The TACAN ground beacon station transmits pulses into the air with a rotating field of 15Hz and 135Hz composite modulation to form 15Hz and 135Hz pulse envelope modulation signals. The pulse envelope modulation signal includes north reference group pulses, auxiliary reference group pulses, station identification pulses, distance response pulses and random filling pulses.

[0013] Furthermore, the TACAN signal processing system includes a detection antenna for receiving signals, a broadband receiver for receiving incoming signals, a narrowband receiver for receiving incoming signals, a processing module for signal processing, and an analysis and extraction module for analyzing the obtained digital signals.

[0014] Furthermore, the TACAN signal processing system includes the following steps for signal processing:

[0015] S1: After the signal is received by the detection antenna, the broadband receiver detects the signal with a frequency of 962 to 1213 MHz;

[0016] S2: Find the center frequency of the signal through spectrum analysis, and use a narrowband receiver to detect the signal with a bandwidth of 1 MHz centered on the center frequency.

[0017] S3: The received signal is digitized by the processing module to obtain the digital signal;

[0018] S4: The digital signal is subjected to parameter measurement, signal pattern recognition, and sorting, and the obtained data is then subjected to position information analysis and extraction.

[0019] Furthermore, there are two modulation modes for TACAN ground beacon stations: pulse modulation and amplitude modulation;

[0020] The AM modulation is generated by rotating the central antenna of the TACAN ground beacon station to generate a radiated signal;

[0021] After the radiation signal passes through the first-stage modulator, the modulator will continuously rotate at a speed of 15 revolutions per second, generating a 15Hz pulse envelope modulation signal.

[0022] After the radiation signal passes through the second-stage modulator, the modulator rotates continuously at a speed of 135 revolutions per second, generating a 135Hz pulse envelope modulation signal.

[0023] Furthermore, the central antenna of the TACAN ground beacon station rotates to generate a radiation signal, including:

[0024] Establishing an antenna array according to the position and distance of the TACAN ground beacon station, establishing a rotating array according to the rotation characteristics of the central antenna of the TACAN ground beacon station, and establishing an antenna rotation model based on the antenna array and the rotating array;

[0025] Obtaining a three-dimensional environmental model of the test area, and marking features in the three-dimensional environmental model according to the terrain, landform and environmental characteristics, and obtaining a three-dimensional dynamic environmental model based on the marking results;

[0026] Determine the flight attitude and flight trajectory of the UAV system according to the flight mission, and establish a UAV flight model based on the flight attitude and flight trajectory;

[0027] Based on the antenna rotation model and the UAV flight model, the UAV-antenna communication process is simulated in the time dimension, and the communication strength relationship between the UAV flight trajectory and attitude changes and the antenna rotation angle adjustment is determined based on the simulation results;

[0028] Based on the communication strength relationship, the flight trajectory and posture of the UAV at each time point and its corresponding optimal antenna angle are determined based on the preset time interval, and the angle change trend of the optimal antenna angle over time is obtained;

[0029] Determine whether there are two adjacent angle values ​​in the angle change trend whose angle adjustment amplitude is greater than a preset amplitude;

[0030] If so, obtain the communication strengths corresponding to two adjacent angle values, and select a second best angle value that satisfies a preset range from the communication strength relationship to replace the angle value with the stronger communication strength among the two adjacent angle values, and finally obtain the target angle change trend;

[0031] Otherwise, taking the angle change trend as the target angle change trend;

[0032] determining a first rotation characteristic of a central antenna of a TACAN ground beacon station based on the target angle change trend;

[0033] Determining, based on the three-dimensional dynamic environment model, an interference feature under the first rotation feature, and judging whether the interference feature can be resolved by changing the rotation angle;

[0034] If so, determining an adjustment range for the rotation angle based on the interference feature to obtain a second rotation feature, and using the second rotation feature as a target rotation feature;

[0035] otherwise, taking the first rotation feature as the target rotation feature;

[0036] The rotation angle of the central antenna of the TACAN ground beacon station is controlled according to the target rotation characteristics to generate a radiation signal.

[0037] Furthermore, the ground management system includes a collection module for collecting and storing route area data, a positioning processing module for determining the position and distance of the TACAN ground beacon, a signal processing module for receiving signals sent by the TACAN ground beacon station and the signals sent by the TACAN signal processing system, and an analysis module for analyzing the received signals, and also includes an evaluation module for comparing the two signals.

[0038] Furthermore, the ground management system is specifically implemented including the following steps:

[0039] S100: Collect route area data through multiple angles and channels, and store the collected data as a basis;

[0040] S200: Determine the TACAN ground beacon location and distance based on the UAV verification project and the ground condition data in the area, and verify the ground beacon signal quality through the UAV;

[0041] S300: Before the UAV is verified, the signal processing module detects the signal sent by the TACAN ground beacon and analyzes the signal quality. The TACAN signal processing system then collects the pulse electromagnetic wave signal emitted by the TACAN ground beacon and analyzes the signal.

[0042] S400: The evaluation module compares the two sets of signal analysis results and evaluates the ground beacon signal quality based on the signal difference.

[0043] Furthermore, the analysis module uses wavelet analysis with different time-frequency resolutions at different scales to distinguish signals with different frequency components and obtain the harmonic components of each frequency of the signal. By changing the scale, the amplitude of any frequency harmonic can be obtained. By analyzing the amplitude of each harmonic, the signal quality difference is obtained and evaluated based on the difference between the two groups of signals.

[0044] Furthermore, the specific steps of evaluating the difference between the two sets of signals are as follows:

[0045] aligning the signal sent by the TACAN ground beacon station with the signal received by the TACAN signal processing system according to the waveforms of the signal sent by the TACAN ground beacon station and the signal received by the TACAN signal processing system, and determining an alignment time period;

[0046] Based on the signal strength values ​​of the signal transmitted by the TACAN ground beacon station and the signal received by the TACAN signal processing system during the alignment time period, a correlation coefficient between the signal transmitted by the TACAN ground beacon station and the signal received by the TACAN signal processing system is determined according to the following formula;

[0047]

[0048] Wherein, γ represents the correlation coefficient between the signal sent by the TACAN ground beacon and the signal received by the TACAN signal processing system, e represents a natural constant with a value of 2.72, K represents the alignment coefficient of the two sets of signals with a value of (0.80, 1.00), τ represents a preset time delay, I(t) represents the signal received by the TACAN signal processing system, O(t) represents the signal sent by the TACAN ground beacon, T represents the alignment time period, and O(t-τ) represents the signal sent by the TACAN ground beacon under the time delay;

[0049] Determining whether the correlation coefficient is greater than a preset coefficient;

[0050] If so, it indicates that the two groups of signals meet the first evaluation requirement, and the two groups of signals are further evaluated;

[0051] Otherwise, it indicates that the two groups of signals do not meet the first evaluation requirement, and the signal quality of the signal received by the TACAN signal processing system is determined to be the third level;

[0052] Further evaluation of both sets of signals includes:

[0053] The difference evaluation value R between the signal sent by the TACAN ground beacon station and the signal received by the TACAN signal processing system is calculated according to the following formula;

[0054]

[0055] Where n represents the number of frequencies of different frequencies, m represents the number of harmonic orders, and A ij It represents the amplitude of the signal sent by the TACAN ground beacon station at the jth harmonic order of the ith frequency, B ij It represents the amplitude of the signal received by the TACAN signal processing system at the jth harmonic order of the ith frequency, α i Indicates the frequency value weight corresponding to the i-th frequency, which is (0, 1), β j Indicates the harmonic order weight corresponding to the j-th harmonic order;

[0056] Determining whether the difference evaluation value is less than a preset evaluation value;

[0057] If so, determining that the signal quality of the signal received by the TACAN signal processing system is a first level;

[0058] Otherwise, it is determined that the signal quality of the signal received by the TACAN signal processing system is the third level.

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] 1. The present invention proposes a method for evaluating and verifying the quality of TACAN ground beacon signals. Before sorting and identifying TACAN signals, the pulse parameters of the TACAN signal must first be obtained. The detected pulse envelope is measured to obtain characteristic parameters such as pulse amplitude, pulse width, and pulse arrival time to form a pulse description word. RF sorting has been completed through a broadband receiver and a narrowband receiver. Pulse amplitude and pulse width are used for pre-sorting. The pulse amplitude is related to the distance and power. The pulse amplitude can be used to sort out TACAN signal sources with closer radiation sources. The pulse width of the TACAN signal is a fixed value. The pulse width can eliminate other signals. Through pre-sorting, the signal obtained is the TACAN signal of a single radiation source. Then, the PRI value of each pulse is calculated from the measured pulse arrival time. The TACAN signal parameter library stores the PRI values ​​of the main and auxiliary reference groups under various TACAN working modes. If the measured PRI satisfies the formula, the pulse is sorted out, thereby completing the signal mode identification, and obtaining the main and auxiliary reference group pulses. The method of calculating the phase difference between the reference group pulse and the envelope zero point phase to obtain the TACAN azimuth information is feasible, which can obtain accurate TACAN azimuth information, improve the stability of model collection, and facilitate signal reception.

[0061] 2. The present invention proposes a method for evaluating and verifying the signal quality of a TACAN ground beacon. After the radiation signal passes through the second-stage modulator, the modulator continuously rotates at a speed of 135 revolutions per second, generating a 135Hz pulse envelope modulation signal. The signal strength is adjusted through amplitude modulation, and flexible adjustments are made according to the verification test to ensure the accuracy of the verification detection structure. The ground beacon station signal can be adjusted according to the test area, environment and project, thereby improving overall adaptability and increasing detection flexibility.

[0062] 3. The present invention proposes a method for evaluating and verifying the quality of TACAN ground beacon signals. The ground management system includes a collection module for collecting and storing route area data, a positioning processing module for determining the position and distance of the TACAN ground beacon, a signal processing module for receiving signals emitted by the TACAN ground beacon station and the signals emitted by the TACAN signal processing system, and an analysis module for analyzing the received signals. It also includes an evaluation module for comparing the two signals. During the flight verification process, the navigation antenna used by the TACAN signal processing system is installed on the tail of the aircraft and then coupled into the receiver. Different flight attitudes affect the reception of the heading signal. The antenna coefficient is accurately measured, and models under different flight attitudes are established to correct the impact on the signal strength.

[0063] 4. The present invention proposes a method for evaluating and verifying the signal quality of a TACAN ground beacon. The analysis module uses wavelet analysis with different time-frequency resolutions at different scales to distinguish signals with different frequency components and obtain the harmonic components of each frequency of the signal. The amplitude of any frequency harmonic can be obtained by changing the scale. The difference in signal quality is obtained by analyzing the amplitude of each harmonic. The difference between the two groups of signals is evaluated based on the noise content in the signal, thereby enabling a more detailed assessment of the signal quality and improving the quality of the assessment. In addition, the corresponding noise can be removed based on the harmonic components of different frequencies, thereby further improving and enhancing the signal quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 is a system topology diagram of the present invention;

[0065] Figure 2 This is a schematic diagram of the TACAN signal processing system module of the present invention;

[0066] Figure 3 is a flow chart of the TACAN signal processing system of the present invention;

[0067] Figure 4 This is a schematic diagram of the ground management system module of the present invention;

[0068] Figure 5 This is a flow chart of the ground management system of the present invention. DETAILED DESCRIPTION

[0069] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0070] See also Figure 1 , a TACAN ground beacon signal quality evaluation and verification method, including a TACAN signal processing system and a ground management system;

[0071] The ground management system determines the position and distance of the TACAN ground beacon station according to the verification plan, so as to perform the TACAN ground beacon signal test during the flight. The TACAN signal processing system is arranged in the UAV flight system, and the TACAN signal processing system is connected to the ground management system;

[0072] The TACAN signal processing system in the UAV collects the pulse electromagnetic wave signals emitted by the TACAN ground beacon station, stores the collected data, and transmits it to the ground management system for processing and evaluation.

[0073] See also Figure 2 The TACAN signal processing system and the TACAN ground beacon station constitute the TACAN navigation system. Its azimuth measurement is to obtain a rotating multi-lobe pattern by rotating the ground beacon antenna to provide azimuth information. The TACAN ground beacon station transmits pulses into the air with a rotating field of 15Hz and 135Hz composite modulation to form 15Hz and 135Hz pulse envelope modulation signals. The pulse envelope modulation signal contains the north reference group pulse, the auxiliary reference group pulse, the station identification pulse, the distance response pulse and the random filling pulse. The TACAN signal processing system includes a signal receiving system. A detection antenna, a broadband receiver for receiving incoming signals, a narrowband receiver for receiving incoming signals, a processing module for signal processing, and an analysis and extraction module for analyzing the obtained digital signal. The receiver converts the TACAN RF signal to a 70MHz intermediate frequency and directly samples the signal at the intermediate frequency. According to the bandpass sampling theorem, the intermediate frequency sampling is performed at a 40MHz sampling rate to obtain a baseband signal with a center frequency of 10MHz and a bandwidth of 20MHz in the first Nyquist zone. After digital down-conversion, a digital baseband signal with a center frequency of zero is obtained.

[0074] Before sorting and identifying TACAN signals, we must first obtain the pulse parameters of the TACAN signal and measure the parameters of the detected pulse envelope to obtain characteristic parameters such as pulse amplitude, pulse width, and pulse arrival time to form a pulse description word. Through broadband receivers and narrowband receivers, RF sorting has been completed. Pulse amplitude and pulse width are used for pre-sorting. The pulse amplitude is related to the distance and power. The pulse amplitude can be used to sort out TACAN signal sources with closer radiation sources. The pulse width of the TACAN signal is a fixed value. The pulse width can be used to eliminate other signals. Through pre-sorting, the signal obtained is the TACAN signal of a single radiation source. Then, the PRI value of each pulse is calculated from the measured pulse arrival time. The TACAN signal parameter library stores the PRI values ​​of the main and auxiliary reference groups under various TACAN working modes. If the measured PRI satisfies the formula, the pulse is sorted out, thereby completing the signal mode identification, and obtaining the main and auxiliary reference group pulses. The method of calculating the phase difference between the reference group pulse and the envelope zero point phase to obtain the TACAN azimuth information is feasible. It can obtain accurate TACAN azimuth information, improve the stability of model reception, and facilitate signal reception.

[0075] In this embodiment, the central antenna of the TACAN ground beacon station rotates to generate a radiation signal, including:

[0076] Establishing an antenna array according to the position and distance of the TACAN ground beacon station, establishing a rotating array according to the rotation characteristics of the central antenna of the TACAN ground beacon station, and establishing an antenna rotation model based on the antenna array and the rotating array;

[0077] Obtaining a three-dimensional environmental model of the test area, and marking features in the three-dimensional environmental model according to the terrain, landform and environmental characteristics, and obtaining a three-dimensional dynamic environmental model based on the marking results;

[0078] Determine the flight attitude and flight trajectory of the UAV system according to the flight mission, and establish a UAV flight model based on the flight attitude and flight trajectory;

[0079] Based on the antenna rotation model and the UAV flight model, the UAV-antenna communication process is simulated in the time dimension, and the communication strength relationship between the UAV flight trajectory and attitude changes and the antenna rotation angle adjustment is determined based on the simulation results;

[0080] Based on the communication strength relationship, the flight trajectory and posture of the UAV at each time point and its corresponding optimal antenna angle are determined based on the preset time interval, and the angle change trend of the optimal antenna angle over time is obtained;

[0081] Determine whether there are two adjacent angle values ​​in the angle change trend whose angle adjustment amplitude is greater than a preset amplitude;

[0082] If so, obtain the communication strengths corresponding to two adjacent angle values, and select a second best angle value that satisfies a preset range from the communication strength relationship to replace the angle value with the stronger communication strength among the two adjacent angle values, and finally obtain the target angle change trend;

[0083] Otherwise, taking the angle change trend as the target angle change trend;

[0084] determining a first rotation characteristic of a central antenna of a TACAN ground beacon station based on the target angle change trend;

[0085] Determining, based on the three-dimensional dynamic environment model, an interference feature under the first rotation feature, and judging whether the interference feature can be resolved by changing the rotation angle;

[0086] If so, determining an adjustment range for the rotation angle based on the interference feature to obtain a second rotation feature, and using the second rotation feature as a target rotation feature;

[0087] otherwise, taking the first rotation feature as the target rotation feature;

[0088] The rotation angle of the central antenna of the TACAN ground beacon station is controlled according to the target rotation characteristics to generate a radiation signal.

[0089] The beneficial effects of the above design scheme are: by establishing an antenna array according to the position and distance of the TACAN ground beacon station, the TACAN ground beacon station is composed of multiple beacons, and the antenna array is established to represent the antenna position and distance information of the TACAN ground beacon station, and then combining the rotation characteristics of the central antenna of the TACAN ground beacon station, such as the rotation range and rotation direction of the antenna, to obtain an antenna rotation model to simulate the rotation of the beacon station antenna, and then establishing a three-dimensional dynamic environment model based on the terrain, landform and environmental characteristics of the test area to simulate the environmental conditions around the TACAN ground beacon station, and also determining the flight attitude and flight trajectory of the UAV system according to the flight mission, and establishing a UAV flight model based on the flight attitude and flight trajectory to simulate the flight conditions of the UAV, and then simulating the UAV-antenna communication process based on the time dimension and the antenna rotation model and the UAV flight model, and determining the UAV flight trajectory and attitude changes and antenna rotation according to the simulation results. The communication strength relationship between angle adjustments is determined, and the communication strength comparison relationship brought about by different antenna rotation angles under the changes in the flight trajectory and attitude of the UAV is determined. According to the communication strength relationship, the trajectory and attitude of the UAV flight at each time point and the corresponding optimal antenna angle are determined based on the preset time interval, and the angle change trend of the optimal antenna angle over time is obtained, which ensures that the optimal antenna angle can maximize the communication with the UAV system. After obtaining the angle change trend of the optimal antenna angle over time, the amplitude of the two adjacent angle values ​​is judged, and the amplitude of the two adjacent angle values ​​that is too large is corrected. The correction method is to obtain the communication strength corresponding to the two adjacent angle values, and select the second best angle value that meets the preset amplitude from the communication strength relationship to replace the angle value with stronger communication strength in the two adjacent angle values, and finally obtain the target angle change trend, which can ensure the feasibility of the rotation angle of the central antenna of the TACAN ground beacon station during the rotation process and ensure the communication capability.

[0090] The beneficial effects of the above design scheme are: by establishing an antenna rotation model and a UAV flight model to simulate the UAV antenna communication process, the communication strength relationship between the UAV flight trajectory and posture changes and the antenna rotation angle adjustment is determined according to the simulation results, and combined with the constraints of the line rotation, the target angle change trend is obtained to ensure the feasibility and communication capability of the target angle change trend. Finally, based on the three-dimensional dynamic environment model of the test area, the interference of the environment on the communication under the target angle change trend is determined, and necessary adjustments are made to ensure the accuracy and actual fit of the rotation angle of the central antenna of the TACAN ground beacon station, and ultimately ensure the signal strength of the radiated signal.

[0091] See also Figure 3 , the TACAN signal processing system includes the following steps for signal processing:

[0092] S1: After the signal is received by the detection antenna, the broadband receiver detects the signal with a frequency of 962 to 1213 MHz;

[0093] S2: Find the center frequency of the signal through spectrum analysis, and use a narrowband receiver to detect the signal with a bandwidth of 1 MHz centered on the center frequency.

[0094] S3: The received signal is digitized by the processing module to obtain the digital signal;

[0095] S4: The digital signal is subjected to parameter measurement, signal pattern recognition, and sorting, and the obtained data is then subjected to position information analysis and extraction.

[0096] There are two modulation modes for ACAN ground beacon stations: pulse modulation and amplitude modulation;

[0097] The AM modulation is generated by rotating the central antenna of the TACAN ground beacon station to generate a radiated signal;

[0098] After the radiation signal passes through the first-stage modulator, the modulator will continuously rotate at a speed of 15 revolutions per second, generating a 15Hz pulse envelope modulation signal.

[0099] After the radiation signal passes through the second-stage modulator, the modulator rotates continuously at a speed of 135 revolutions per second, generating a 135Hz pulse envelope modulation signal. The signal strength is adjusted through amplitude modulation and can be flexibly adjusted according to the verification test to ensure the accuracy of the verification detection structure. The ground beacon station signal can be adjusted according to the test area, environment and project to improve overall adaptability and increase detection flexibility.

[0100] See also Figure 4 The ground management system includes a collection module for collecting and storing route area data, a positioning processing module for determining the position and distance of the TACAN ground beacon, a signal processing module for receiving signals sent by the TACAN ground beacon and the signal sent by the TACAN signal processing system, and an analysis module for analyzing the received signals. It also includes an evaluation module for comparing the two signals. During the flight verification process, the navigation antenna used by the TACAN signal processing system is installed on the tail of the aircraft and then coupled into the receiver. Different flight attitudes affect the reception of the heading signal. The antenna coefficient is accurately measured, and models under different flight attitudes are established to correct the impact on the signal strength.

[0101] See also Figure 5 , the specific implementation of the ground management system includes the following steps:

[0102] S100: Collect route area data through multiple angles and channels, and store the collected data as a basis;

[0103] S200: Determine the TACAN ground beacon location and distance based on the UAV verification project and the ground condition data in the area, and verify the ground beacon signal quality through the UAV;

[0104] S300: Before the UAV is verified, the signal processing module detects the signal sent by the TACAN ground beacon and analyzes the signal quality. The TACAN signal processing system then collects the pulse electromagnetic wave signal emitted by the TACAN ground beacon and analyzes the signal.

[0105] S400: The evaluation module compares the two sets of signal analysis results and evaluates the ground beacon signal quality based on the signal difference.

[0106] The analysis module uses wavelet analysis, which has different time-frequency resolutions at different scales, to distinguish signals with different frequency components and calculate the harmonic components of each frequency of the signal. By changing the scale, the amplitude of any frequency harmonic can be calculated. By analyzing the amplitude of each harmonic, the difference in signal quality is obtained. The difference between the two groups of signals is evaluated based on the noise content in the signal, so that the quality of the signal can be more carefully evaluated and the quality of the evaluation can be improved. In addition, according to the different frequency harmonic components, the corresponding noise can be removed to further improve and enhance the quality of the signal.

[0107] In this paper, the specific steps of evaluating the difference between the two sets of signals are as follows:

[0108] aligning the signal sent by the TACAN ground beacon station with the signal received by the TACAN signal processing system according to the waveforms of the signal sent by the TACAN ground beacon station and the signal received by the TACAN signal processing system, and determining an alignment time period;

[0109] Based on the signal strength values ​​of the signal transmitted by the TACAN ground beacon station and the signal received by the TACAN signal processing system during the alignment time period, a correlation coefficient between the signal transmitted by the TACAN ground beacon station and the signal received by the TACAN signal processing system is determined according to the following formula;

[0110]

[0111] Wherein, γ represents the correlation coefficient between the signal sent by the TACAN ground beacon and the signal received by the TACAN signal processing system, e represents a natural constant with a value of 2.72, K represents the alignment coefficient of the two sets of signals with a value of (0.80, 1.00), τ represents a preset time delay, I(t) represents the signal received by the TACAN signal processing system, O(t) represents the signal sent by the TACAN ground beacon, T represents the alignment time period, and O(t-τ) represents the signal sent by the TACAN ground beacon under the time delay;

[0112] Determining whether the correlation coefficient is greater than a preset coefficient;

[0113] If so, it indicates that the two groups of signals meet the first evaluation requirement, and the two groups of signals are further evaluated;

[0114] Otherwise, it indicates that the two groups of signals do not meet the first evaluation requirement, and the signal quality of the signal received by the TACAN signal processing system is determined to be the third level;

[0115] Further evaluation of both sets of signals includes:

[0116] The difference evaluation value R between the signal sent by the TACAN ground beacon station and the signal received by the TACAN signal processing system is calculated according to the following formula;

[0117]

[0118] Where n represents the number of frequencies of different frequencies, m represents the number of harmonic orders, and A ij It represents the amplitude of the signal sent by the TACAN ground beacon station at the jth harmonic order of the ith frequency, B ij It represents the amplitude of the signal received by the TACAN signal processing system at the jth harmonic order of the ith frequency, α i Indicates the frequency value weight corresponding to the i-th frequency, which is (0, 1), β j Indicates the harmonic order weight corresponding to the j-th harmonic order;

[0119] Determining whether the difference evaluation value is less than a preset evaluation value;

[0120] If so, determining that the signal quality of the signal received by the TACAN signal processing system is a first level;

[0121] Otherwise, it is determined that the signal quality of the signal received by the TACAN signal processing system is the third level.

[0122] In this embodiment, the signal qualities corresponding to the first level, the second level, and the third level decrease in sequence.

[0123] In this embodiment, the larger the harmonic order, the larger the corresponding harmonic order weight.

[0124] In this embodiment, the larger the frequency component of the signal is, the larger the corresponding frequency value weight is.

[0125] The working principle of the above design scheme is: first, after the two groups of signals are aligned, the correlation coefficient within the alignment time period is determined. Then, when determining the correlation coefficient, the alignment coefficient of the two groups of signals is added to eliminate the influence of the alignment error on the determination of the correlation coefficient. After the correlation coefficient meets the preset requirements, the amplitude difference of the signal at different frequencies and harmonic orders obtained by wavelet analysis is further compared. The harmonic order weight and frequency value weight are introduced to weight the important parts, so that the obtained difference evaluation value is more accurate, and finally the quality level of the received signal is determined.

[0126] The beneficial effects of the above design scheme are: first, after the two groups of signals are aligned, the correlation coefficient within the alignment time period is determined. The smaller the correlation coefficient, the greater the difference between the two signals, indicating that the quality of the received moral signal is worse. After the correlation coefficient meets the preset requirements, the two groups of signals are further evaluated by comparing the amplitude differences of the signals obtained by wavelet analysis transformation at different frequencies and harmonic orders, and finally the quality of the received signal is determined, which can make a more detailed assessment of the signal quality and improve the quality of the assessment.

[0127] In summary, the present invention proposes a method for evaluating and verifying the quality of TACAN ground beacon signals. Before sorting and identifying TACAN signals, the pulse parameters of the TACAN signals must first be obtained, and the detected pulse envelope must be measured to obtain characteristic parameters such as pulse amplitude, pulse width, and pulse arrival time to form a pulse description word. The RF sorting has been completed through a broadband receiver and a narrowband receiver. The pulse amplitude and pulse width are used for pre-sorting. The pulse amplitude is related to the distance and power. The pulse amplitude can be used to sort out TACAN signal sources with closer radiation sources. The pulse width of the TACAN signal is a fixed value. The pulse width can be used to eliminate other signals. Through pre-sorting, The signal received is the TACAN signal of a single radiation source. Then, the PRI value of each pulse is calculated from the measured pulse arrival time. The TACAN signal parameter library stores the PRI values ​​of the main and auxiliary reference groups under various TACAN working modes. If the measured PRI satisfies the formula, the pulse is sorted out to complete the signal mode recognition and obtain the main and auxiliary reference group pulses. The method of calculating the phase difference between the reference group pulse and the envelope zero point phase to obtain the TACAN azimuth information is feasible. It can obtain accurate TACAN azimuth information, improve the stability of the model collection, and facilitate the reception of signals. After the radiation signal passes through the second-stage modulator, the modulator rotates continuously at a speed of 135 turns per second, generating a 135Hz pulse packet The network modulated signal is adjusted by amplitude modulation, and its signal strength is adjusted by amplitude modulation. It is flexibly adjusted according to the verification test to ensure the accuracy of the verification detection structure. The ground beacon station signal can be adjusted according to the test area, environment and project to improve the overall adaptability and increase the flexibility of detection. The ground management system includes a collection module for collecting and storing route area data, a positioning processing module for determining the position and distance of the TACAN ground beacon, a signal processing module for receiving the signal sent by the TACAN ground beacon station and the signal sent by the TACAN signal processing system, and an analysis module for analyzing the received signal. It also includes an evaluation module for comparing the two signals. During the flight verification, the TACAN signal processing module The navigation antenna used in the navigation system is installed on the tail of the aircraft and then coupled into the receiver. Different flight attitudes affect the reception of the heading signal. The antenna coefficient is accurately measured, and models under different flight attitudes are established to correct the impact on the signal strength. The analysis module uses wavelet analysis, which has different time-frequency resolutions at different scales, to distinguish signals with different frequency components and calculate the harmonic components of each frequency of the signal. By changing the scale, the amplitude of any frequency harmonic can be calculated. By analyzing the amplitude of each harmonic, the difference in signal quality is obtained. The difference between the two groups of signals is evaluated. According to the noise content in the signal, the quality of the signal can be more carefully evaluated to improve the quality of the evaluation. In addition, according to the harmonic components of different frequencies, the corresponding noise is removed.It can also improve and enhance the quality of the signal.

[0128] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for evaluating and verifying the quality of a TACAN ground beacon signal, characterized by: Includes TACAN signal processing system and ground management system; The ground management system determines the position and distance of the TACAN ground beacon station according to the verification plan, so as to perform the TACAN ground beacon signal test during the flight. The TACAN signal processing system is arranged in the UAV flight system, and the TACAN signal processing system is connected to the ground management system; The TACAN signal processing system in the UAV collects pulse electromagnetic wave signals emitted by the TACAN ground beacon station, stores the collected data, and transmits it to the ground management system for processing and evaluation; There are two modulation methods for TACAN ground beacon stations: pulse modulation and amplitude modulation; The amplitude modulation is generated by the rotation of the central antenna of the TACAN ground beacon station to generate a radiated signal, including: Establishing an antenna array according to the position and distance of the TACAN ground beacon station, establishing a rotating array according to the rotation characteristics of the central antenna of the TACAN ground beacon station, and establishing an antenna rotation model based on the antenna array and the rotating array; Obtaining a three-dimensional environmental model of the test area, and marking features in the three-dimensional environmental model according to the terrain, landform and environmental characteristics, and obtaining a three-dimensional dynamic environmental model based on the marking results; Determine the flight attitude and flight trajectory of the UAV system according to the flight mission, and establish a UAV flight model based on the flight attitude and flight trajectory; Based on the antenna rotation model and the UAV flight model, the UAV-antenna communication process is simulated in the time dimension, and the communication strength relationship between the UAV flight trajectory and attitude changes and the antenna rotation angle adjustment is determined based on the simulation results; Based on the communication strength relationship, the flight trajectory and posture of the UAV at each time point and its corresponding optimal antenna angle are determined based on the preset time interval, and the angle change trend of the optimal antenna angle over time is obtained; Determine whether there are two adjacent angle values ​​in the angle change trend whose angle adjustment amplitude is greater than a preset amplitude; If so, obtain the communication strengths corresponding to two adjacent angle values, and select a second best angle value that satisfies a preset range from the communication strength relationship to replace the angle value with the stronger communication strength among the two adjacent angle values, and finally obtain the target angle change trend; Otherwise, taking the angle change trend as the target angle change trend; determining a first rotation characteristic of a central antenna of a TACAN ground beacon station based on the target angle change trend; Determining, based on the three-dimensional dynamic environment model, an interference feature under the first rotation feature, and judging whether the interference feature can be resolved by changing the rotation angle; If so, determining an adjustment range for the rotation angle based on the interference feature to obtain a second rotation feature, and using the second rotation feature as a target rotation feature; otherwise, taking the first rotation feature as the target rotation feature; The rotation angle of the central antenna of the TACAN ground beacon station is controlled according to the target rotation characteristics to generate a radiation signal.

2. The method for evaluating and verifying the signal quality of a TACAN ground beacon according to claim 1, wherein: The TACAN signal processing system and the TACAN ground beacon station constitute a TACAN navigation system, whose azimuth measurement is to obtain a rotating multi-lobe radiation pattern by rotating the ground beacon antenna to provide azimuth information. The TACAN ground beacon station transmits pulses into the air with a rotating field of 15Hz and 135Hz composite modulation to form 15Hz and 135Hz pulse envelope modulation signals. The pulse envelope modulation signal includes a north reference group pulse, an auxiliary reference group pulse, a station identification pulse, a distance response pulse and a random filling pulse.

3. The method for evaluating and verifying the signal quality of a TACAN ground beacon according to claim 2, wherein: The TACAN signal processing system includes a detection antenna for receiving signals, a broadband receiver for receiving incoming signals, a narrowband receiver for receiving incoming signals, a processing module for signal processing, and an analysis and extraction module for analyzing the obtained digital signals.

4. The method for evaluating and verifying the signal quality of a TACAN ground beacon according to claim 2, wherein: The TACAN signal processing system includes the following steps for signal processing: S1: After the signal is received by the detection antenna, the broadband receiver detects the signal with a frequency of 962 to 1213 MHz; S2: Find the center frequency of the signal through spectrum analysis, and use a narrowband receiver to detect the signal with a bandwidth of 1 MHz centered on the center frequency. S3: The received signal is digitized by the processing module to obtain the digital signal; S4: The digital signal is subjected to parameter measurement, signal pattern recognition, and sorting, and the obtained data is then subjected to position information analysis and extraction.

5. The method for evaluating and verifying the signal quality of a TACAN ground beacon according to claim 2, wherein: There are two modulation modes for the TACAN ground beacon station: pulse modulation and amplitude modulation; The AM modulation is generated by rotating the central antenna of the TACAN ground beacon station to generate a radiated signal; After the radiation signal passes through the first-stage modulator, the modulator will continuously rotate at a speed of 15 revolutions per second, generating a 15Hz pulse envelope modulation signal. After the radiation signal passes through the second-stage modulator, the modulator rotates continuously at a speed of 135 revolutions per second, generating a 135Hz pulse envelope modulation signal.

6. The method for evaluating and verifying the signal quality of a TACAN ground beacon according to claim 1, wherein: The ground management system includes a collection module for collecting and storing route area data, a positioning processing module for determining the position and distance of TACAN ground beacons, a signal processing module for receiving signals emitted by TACAN ground beacons and signals emitted by TACAN signal processing systems, and an analysis module for analyzing received signals, and also includes an evaluation module for comparing the two signals.

7. The method for evaluating and verifying the quality of a TACAN ground beacon signal according to claim 6, wherein: The specific implementation of the ground management system includes the following steps: S100: Collect route area data through multiple angles and channels, and store the collected data as a basis; S200: Determine the TACAN ground beacon location and distance based on the UAV verification project and the ground condition data in the area, and verify the ground beacon signal quality through the UAV; S300: Before the UAV is verified, the signal processing module detects the signal sent by the TACAN ground beacon and analyzes the signal quality. The TACAN signal processing system then collects the pulse electromagnetic wave signal emitted by the TACAN ground beacon and analyzes the signal. S400: The evaluation module compares the two sets of signal analysis results and evaluates the ground beacon signal quality based on the signal difference.

8. The method for evaluating and verifying the signal quality of a TACAN ground beacon according to claim 6, wherein: The analysis module uses wavelet analysis with different time-frequency resolutions at different scales to distinguish signals with different frequency components and calculate the harmonic components of each frequency of the signal. By changing the scale, the amplitude of any frequency harmonic can be calculated. By analyzing the amplitude of each harmonic, the difference in signal quality is obtained and evaluated based on the difference between the two groups of signals.

9. The method for evaluating and verifying the quality of a TACAN ground beacon signal according to claim 8, wherein: The specific steps for evaluating the difference between two sets of signals are as follows: aligning the signal sent by the TACAN ground beacon station with the signal received by the TACAN signal processing system according to the waveforms of the signal sent by the TACAN ground beacon station and the signal received by the TACAN signal processing system, and determining an alignment time period; Based on the signal strength values ​​of the signal transmitted by the TACAN ground beacon station and the signal received by the TACAN signal processing system during the alignment time period, a correlation coefficient between the signal transmitted by the TACAN ground beacon station and the signal received by the TACAN signal processing system is determined according to the following formula; Wherein, γ represents the correlation coefficient between the signal sent by the TACAN ground beacon and the signal received by the TACAN signal processing system, e represents a natural constant with a value of 2.72, K represents the alignment coefficient of the two sets of signals with a value of (0.80, 1.00), τ represents a preset time delay, I(t) represents the signal received by the TACAN signal processing system, O(t) represents the signal sent by the TACAN ground beacon, T represents the alignment time period, and O(t-τ) represents the signal sent by the TACAN ground beacon under the time delay; Determining whether the correlation coefficient is greater than a preset coefficient; If so, it indicates that the two groups of signals meet the first evaluation requirement, and the two groups of signals are further evaluated; Otherwise, it indicates that the two groups of signals do not meet the first evaluation requirement, and the signal quality of the signal received by the TACAN signal processing system is determined to be the third level; Further evaluation of both sets of signals includes: The difference evaluation value R between the signal sent by the TACAN ground beacon station and the signal received by the TACAN signal processing system is calculated according to the following formula; Where n represents the number of frequencies of different frequencies, m represents the number of harmonic orders, and A ij It represents the amplitude of the signal sent by the TACAN ground beacon station at the jth harmonic order of the ith frequency, B ij It represents the amplitude of the signal received by the TACAN signal processing system at the jth harmonic order of the ith frequency, α i Indicates the frequency value weight corresponding to the i-th frequency, which is (0, 1), β j Indicates the harmonic order weight corresponding to the j-th harmonic order; Determining whether the difference evaluation value is less than a preset evaluation value; If so, determining that the signal quality of the signal received by the TACAN signal processing system is a first level; Otherwise, it is determined that the signal quality of the signal received by the TACAN signal processing system is the third level.

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