Airborne Lightning Detection System

Abstract

The present invention discloses an airborne lightning detection system, which belongs to the technical fields of lightning early warning for aircraft and lightning monitoring and early warning for high-speed ground vehicles. It addresses the problem that existing technologies cannot achieve high-precision single-station measurements, making them unsuitable for use in mobile devices. The system includes vertical and horizontal antennas for acquiring vertical and horizontal electric field signals from a space lightning radiation source; an integration circuit for converting the electric field signals into voltages; a high-pass amplifier circuit for filtering out clutter from the integrated voltage signal, performing waveform identification and matching, and amplifying the radiation signal; a sampling analog-to-digital conversion circuit for sampling the signal output by the high-pass amplifier circuit and converting the analog signal into a digital signal; a radio positioning antenna for acquiring lightning direction information from the lightning radiation source; and an embedded Linux system that combines the digital signal and lightning direction information to calculate the distance from the lightning radiation source. The system is used to calculate the distance between the radiation source and an observation point.

Description

Technical Field

[0001] The invention relates to an airborne lightning detection system, which is used for calculating the distance between a radiation source and an observation point, and belongs to the technical field of lightning early warning for aircraft and lightning monitoring and early warning for ground high-speed vehicles. Background Art

[0002] Existing low-frequency / very low-frequency (VLF) lightning location technologies include magnetic direction finding (MDF), time difference of approach (TOA), and combined magnetic direction and time difference (IMPACT). Although MDF can determine two-dimensional information about lightning occurrence, its direction-finding accuracy is significantly affected by ground objects and terrain, and requires two or more detection points to determine the location. TOA also requires multiple sites for lightning location and has high timing accuracy requirements. IMPACT, which combines MDF and TOA, is currently the most practical lightning location technology and can guarantee excellent location accuracy with a sufficient number of sites. The above three lightning location technologies each have their own advantages and disadvantages, and the following technical issues exist:

[0003] 1. It is impossible to achieve high-precision measurement at a single station, making it unsuitable for application in mobile devices.

[0004] 2. The three methods are suitable for long-distance measurement. When detecting at short distances (10km-150km), they are subject to significant interference from terrain factors or insufficient echo time difference, and the detection accuracy is not high enough.

[0005] Current research in domestic lightning location technology primarily focuses on using a multi-site deployment approach. Existing single-point lightning location methods suffer from large errors, making them inadequate for timely lightning monitoring and early warning. Utilizing the relationship between lightning's horizontal and vertical electric fields offers high detection accuracy, maintaining an error of approximately 2% after correction. Furthermore, utilizing the relationship between electric field intensity to locate lightning is currently a niche technology in China. This represents a new direction in the application of lightning electric fields. Summary of the Invention

[0006] In response to the above research issues, the purpose of the present invention is to provide an airborne lightning detection system to solve the technical problem that the existing technology cannot achieve high-precision measurement of a single station and is therefore not suitable for application in mobile devices.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] An airborne lightning detection system includes a vertical antenna and a horizontal antenna for acquiring vertical and horizontal electric field signals of a space lightning radiation source; an integration circuit for converting the electric field signal into a voltage; a high-pass amplifier circuit for filtering out clutter signals from the integrated voltage signal to perform waveform recognition and matching of the radiation signal and amplify the signal; a sampling analog-to-digital conversion circuit for sampling the signal output by the high-pass amplifier circuit and converting the analog signal into a digital signal; a radio positioning antenna for acquiring lightning direction information of the lightning radiation source; and an embedded Linux system for calculating the distance to the lightning radiation source by combining the digital signal and the lightning direction information.

[0009] Furthermore, it also includes weather radar for detecting thunderstorms.

[0010] Furthermore, the embedded Linux system calculates the distance of the lightning radiation source based on the digital signal using the EE method of electric field measurement, that is, the distance between the radiation source and the observation point.

[0011] Furthermore, the specific steps of the EE method for electric field measurement are:

[0012] Step 1. According to the field superposition principle, arbitrarily oriented radiating dipoles Decompose the spatial coordinates into horizontal left and right components , horizontal front-back component and vertical component The projection formula in three directions is as follows:

[0013] (1)

[0014] in, is the spatial angle between the radiation source and the receiver;

[0015] Step 2. Based on the radiating dipole of , ,and Projection in three directions, then , The electric fields generated by the projection are projected into the spatial coordinate system, and the radiation dipole is obtained after projection Components of the electric field;

[0016] Step 3. Based on radiating dipole The components of the electric field are obtained by the square relationship of the vertical and horizontal values ​​of the electric field components of the radiating dipole;

[0017] Step 4. Obtain the lightning radiation source distance based on the square relationship between the vertical and horizontal values ​​of the electric field components of the radiation dipole.

[0018] Furthermore, in step 2, the radiating dipole The specific calculation formula of the components of the electric field is:

[0019] For the vertical component , the electric field components are calculated 、 and ,in, Represents the vertical component of the radiating dipole received by the vertical antenna The horizontal electric field components generated are Represents the vertical component of the radiating dipole received by the vertical antenna The horizontal front and rear electric field components generated, Indicates that the vertical antenna receives the vertical component of the radiating dipole The vertical electric field component generated is:

[0020]

[0021] (2)

[0022]

[0023] For horizontal left and right components , the electric field components are calculated 、 and ,in, Indicates the horizontal left and right components of the radiating dipole received by the horizontal antenna The horizontal electric field components generated are Indicates the horizontal left and right components of the radiating dipole received by the horizontal antenna The horizontal front and rear electric field components generated, Indicates that the horizontal antenna receives the horizontal left and right components of the radiating dipole The vertical electric field component generated is:

[0024] (3)

[0025]

[0026] For horizontal front-back component , the electric field components are calculated 、 and ,in, Represents the horizontal front and rear components of the radiating dipole received by the horizontal antenna The horizontal electric field components generated are Represents the horizontal front and rear components of the radiating dipole received by the horizontal antenna The horizontal front and rear electric field components generated, Indicates that the horizontal antenna receives the horizontal front and rear components of the radiating dipole The vertical electric field component generated is:

[0027] (4)

[0028]

[0029]

[0030] .

[0031]

[0032] in, is the wave number, is the distance between the detection point and the radiation point, that is, the distance from the lightning radiation source, is the vertical distance between the detection point and the radiation, is the vacuum dielectric constant of the antenna plate, is the angle between the field intensity generated by the radiation dipole component and the detection point, is a given constant, 、 、 、 、 、 、 、 are all intermediate quantities, In complex exponential form, in The plural number in .

[0033] Furthermore, in step 3, based on the radiation dipole The components of the electric field are obtained by the formula for the square relationship between the vertical and horizontal values ​​of the electric field components of the radiating dipole:

[0034] (5)

[0035] Simplifying to get:

[0036] (6)

[0037]

[0038] in, is the altitude of the detection point, 、 、 and To simplify the substitution.

[0039] Furthermore, step 4 is based on formula 5 and is obtained by receiving the vertical and horizontal values ​​of the electric field components of the radiation dipole, the wave number of the radiation source, and the altitude of the observation point, and the distance between the radiation source and the observation point is obtained by inversion.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] First, the present invention uses the EE method to calculate the distance between the radiation source and the observation point. It only requires a single observation point to set up a horizontal flat panel antenna and a vertical flat panel antenna. The different electric field signal values ​​of the two panels are used to deduce the distance information of the lightning radiation source. This method has high accuracy and is simpler and more convenient than using MDF, TOA, and IMPACT in the very low frequency band to obtain lightning distance information.

[0042] 2. The present invention is a portable device suitable for mobile devices, with small errors in close-range measurements. In practical applications, it can provide real-time warnings. By measuring the distance between the device and lightning, it can avoid lightning clouds in advance or install protective facilities to reduce damage to facilities caused by lightning. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the lightning radiation source and the coordinates of the aircraft on the ground;

[0044] Figure 2 This is the overall block diagram of the system. The signal is received by the system through the antenna and the horizontal field strength is measured. Vertical field strength The value is then obtained by the square relationship between the vertical and horizontal values ​​of the electric field component of the radiating dipole. At the same time, the lightning direction H is measured. After processing and eliminating unreasonable data, the lightning location information is obtained. Then, by adding additional information such as altitude and radar thunderstorm data, the lightning location is finally displayed.

[0045] Figure 3 This is an example diagram of the EE method algorithm simulation. Input parameters are wave number k and height z. Different quantities are set by looping. , substitute into formula 7 to obtain the intermediate quantities m1, m2, m3, and m4. Substitute the intermediate quantities into formula 6. The right side of the obtained formula 6 is not equal to 0. Therefore, it is necessary to iterate to reduce the error Y. After Y is reduced to a certain range, the error Y is output. The closer the Y value is to 0, the more accurate the distance R is.

[0046] Figure 4 Z curves measured at different altitudes The horizontal axis is the distance R between the observation point and the lightning radiation source. The curves are from top to bottom at an altitude of 500m, 1km, 1.5km, 2km, 3km, 4km, 5km, and 10km respectively.

[0047] Figure 5 Measured for receiving signals of 5kHz and 1MHz at different distances Value, where the horizontal axis is the distance R and the vertical axis is value;

[0048] Figure 6 The error diagram of different distances R versus the frequency of the received radiation source, the horizontal axis is the frequency of the received radiation signal source, and the vertical axis is the error;

[0049] Figure 7 This is an analysis chart of the error between the measured distance and the actual distance at a fixed frequency and height. The horizontal axis is the measured distance and the vertical axis is the error percentage.

[0050] Figure 8 The curves of the equivalent dipole at different vertical deviations are shown in Figure 1, where the horizontal axis is the height of the observation point (aircraft) and the horizontal axis is the height of the dipole. The curves are 10° and 5° from top to bottom respectively.

[0051] Figure 9 is the error caused by the deviation of the equivalent dipole from the vertical direction, where is set as a constant, the abscissa is the height of the observation point, the ordinate is the error, the upper curve is 10° deviation from the vertical, the lower curve is 5° deviation from the vertical, the equivalent dipole is the vertical projection component Pz of the dipole, the relative error is the relative error with different degrees of deviation compared to no deviation, and the Altitude of aircraft, m is the height of the observation point (aircraft);

[0052] Figure 10 This is the distance measurement error diagram of the EE method. The horizontal axis is distance and the vertical axis is error. Among them, 1 is the uncorrected error and 2 is the calibrated error.

[0053] Figure 11 This is a comparison chart of the errors between the EE method and the HH method. The horizontal axis is the distance, the vertical axis is the error, 1 is the error of the HH method, and 2 is the error of the EE average method;

[0054] Figure 12This is the circuit diagram of a single-plate antenna. When lightning strikes, the circuit's single plate receives the electric field signal. After passing through the integrating amplifier circuit, the electric field signal is converted into a voltage signal. The high-pass amplifier circuit then filters out the noise signal and amplifies the signal appropriately. The signal passes through the analog-to-digital conversion circuit, which samples the continuous analog signal into a digital signal. The digital signal is input into the embedded Linux system for data processing. When this circuit acts as a horizontal antenna and a vertical antenna respectively, it can collect the horizontal and vertical electric field values ​​of the lightning. DETAILED DESCRIPTION

[0055] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0056] An airborne lightning detection system includes a vertical antenna and a horizontal antenna for acquiring vertical and horizontal electric field signals of a space lightning radiation source; an integration circuit for converting the electric field signal into a voltage; a high-pass amplifier circuit for filtering out clutter signals from the integrated voltage signal to perform waveform recognition and matching of the radiation signal and amplify the signal; a sampling analog-to-digital conversion circuit for sampling the signal output by the high-pass amplifier circuit and converting the analog signal into a digital signal; a radio positioning antenna for acquiring lightning direction information of the lightning radiation source; and an embedded Linux system for calculating the distance to the lightning radiation source by combining the digital signal and the lightning direction information.

[0057] The embedded Linux system calculates the lightning radiation source distance of the digital signal based on the EE method of electric field measurement.

[0058] The specific steps of the EE method of electric field measurement are:

[0059] Step 1. According to the field superposition principle, arbitrarily oriented radiating dipoles Decompose the spatial coordinates into horizontal left and right components , horizontal front-back component and vertical component The projection formula in three directions is as follows:

[0060] (1)

[0061] in, is the spatial angle between the radiation source and the receiver;

[0062] Step 2. Based on the radiating dipole of , ,and Projection in three directions, then , The electric fields generated by the projection are projected into the spatial coordinate system, and the radiation dipole is obtained after projection Components of the electric field;

[0063] Radiating dipole The specific calculation formula of the components of the electric field is:

[0064] For the vertical component , the electric field components are calculated 、 and ,in, Represents the vertical component of the radiating dipole received by the vertical antenna The horizontal electric field components generated are Represents the vertical component of the radiating dipole received by the vertical antenna The horizontal front and rear electric field components generated, Indicates that the vertical antenna receives the vertical component of the radiating dipole The vertical electric field component generated is:

[0065]

[0066] (2)

[0067]

[0068] For horizontal left and right components , the electric field components are calculated 、 and ,in, Indicates the horizontal left and right components of the radiating dipole received by the horizontal antenna The horizontal electric field components generated are Indicates the horizontal left and right components of the radiating dipole received by the horizontal antenna The horizontal front and rear electric field components generated, Indicates that the horizontal antenna receives the horizontal left and right components of the radiating dipole The vertical electric field component generated is:

[0069] (3)

[0070]

[0071] For horizontal front-back component , the electric field components are calculated 、 and ,in, Represents the horizontal front and rear components of the radiating dipole received by the horizontal antenna The horizontal electric field components generated are Represents the horizontal front and rear components of the radiating dipole received by the horizontal antenna The horizontal front and rear electric field components generated, Indicates that the horizontal antenna receives the horizontal front and rear components of the radiating dipole The vertical electric field component generated is:

[0072] (4)

[0073] (4)

[0074]

[0075] .

[0076]

[0077] in, is the wave number, is the distance between the detection point and the radiation point, that is, the distance from the lightning radiation source, is the vertical distance between the detection point and the radiation, is the vacuum dielectric constant of the antenna plate, is the angle between the field intensity generated by the radiation dipole component and the detection point, is a given constant, 、 、 、 、 、 、 、 are all intermediate quantities, In complex exponential form.

[0078] Step 3. Based on radiating dipole The components of the electric field are obtained by the square relationship of the vertical and horizontal values ​​of the electric field components of the radiating dipole;

[0079] Based on radiating dipole The components of the electric field are obtained by the formula for the square relationship between the vertical and horizontal values ​​of the electric field components of the radiating dipole:

[0080] (5)

[0081] Simplifying to get:

[0082]

[0083]

[0084] in, is the altitude of the detection point, 、 、 and To simplify the substitution.

[0085] Step 4. Calculate the lightning radiation source distance based on the square relationship between the vertical and horizontal values ​​of the radiating dipole electric field components. Specifically, based on Equation 5, the vertical and horizontal values ​​of the radiating dipole electric field components, the radiation source wave number, and the observation point altitude are received, and the distance between the radiation source and the observation point is calculated through inversion.

[0086] The accuracy of the distance estimated by the above EE-method depends on several reasons. It is analyzed by formulas 2 and 5, among which: 1) the error caused by assuming that the equivalent lightning dipole is located near the surface of the earth; 2) the error caused by the deviation of the equivalent dipole from the vertical direction; 3) the error in measuring the electric field strength. This method is applicable to the technology of estimating the distance of lightning discharge from a position (for example, in aircraft equipment). By establishing a mathematical model of the discharge radiation field component, it is concluded that when the distance is 30km, the error caused by the first reason is about 11%. When the distance is 100km, this error gradually decreases to 1.5%. This error can be corrected by calculating the error, so that the error is reduced by 5-6 times. The error of the distance between the radiation source and the observation point before and after correction is as follows: Figure 10 The problem is that the spatial location of the lightning channel is unknown to the observer a priori, making it difficult to make corrections. However, it can generally be determined through auxiliary measurements, such as using radar echo patterns to verify the correctness of the measured distance. For single-point distance measurements, electronic measurement techniques based on orthogonal planes offer higher accuracy than those based on magnetic components.

[0087] The comparison of the amplitude method (AA-method), electromagnetic method (EH-method), magnetic method (HH-method) and electric field intensity polarization method (EE-method) is shown in the following table:

[0088] method Measuring range Measurement accuracy Method characteristics AA-Law The range depends on the energy of the lightning Low-precision distance measurement Based solely on the power of its own lightning emitter EH-method Within a limited distance of no more than 60 kilometers But within a limited range, the accuracy is no worse than 10% Measurement of the ratio of certain properties of the electric and magnetic components based on lightning measurements HH-method The maximum distance measurement range is 200 kilometers A maximum deviation of 200 km allows for 10% of the required accuracy Based on the measurement of the ratio of the magnetic components of the lightning discharge radiation field EE-Law Measurement range within 100 kilometers Reduce the margin of error to accurately estimate the range Based on the measurement of the strength of the two components of the electric field in two orthogonal planes

[0089] According to the comparison of the four methods, the AA method is too dependent on the intensity of the radiation source and has low accuracy. When the radiation intensity is weak, it cannot complete the positioning and detection of lightning. The EH method has a short detection distance and is not suitable for application on high-speed aircraft. The HH method is suitable for medium and long-distance detection, but the error is too large for close-range detection below 50 kilometers. The EE method determines the lightning distance by the ratio of the horizontal and vertical field strength components. It does not depend on the intensity of the radiation source and has an error within 3% within 100 kilometers. In terms of aircraft application, it is significantly better than the other three methods. Example

[0090] When the EE method is used to measure distances of 30km-100km without correction, the error in the distance between the radiation source and the observation point is between 11% and 1.5%. One of the reasons is that the height of the equivalent lightning dipole is assumed to be zero. As the distance increases, the influence of this factor decreases. The second error is caused by the deviation of the equivalent dipole from the vertical position. This error can be reduced by identifying vertical discharges. Data processing can use the averaging method to reduce the error in electric field strength measurement. Figure 10 The error after correction is less than 1.8%. Averaging can reduce measurement errors. The EE method can be implemented on a single frequency or using a specially processed spectrum. Figure 11 The accuracy comparison of HH method and average and EE method is given.

[0091] The present invention studies a method for measuring the distance and direction of high-altitude thunderstorm discharges. The method is based on measuring the intensity of two components of the electric field on two orthogonal planes to determine the method for estimating the lightning discharge distance from a location (for example, in aircraft equipment), that is, the EE method. It is assumed that the lightning radiation source has an equivalent dipole P characteristic. If the distance to the lightning R exceeds 30 kilometers, the field superposition principle is used to represent the radiation field in the near field area. In other words, by measuring the ratio of the electric field intensity in the vertical plane to the horizontal plane at the same frequency, the distance between the lightning and the airborne receiver can be determined. The algorithm uses the electric field intensity of the radiation field as an information parameter, and the very low frequency band where the main energy is concentrated is a better choice.

[0092] The above are only representative embodiments of the present invention in many specific application scopes and do not constitute any limitation on the protection scope of the present invention. Any technical solutions formed by transformation or equivalent replacement fall within the scope of protection of the present invention.

Claims

1. An airborne lightning detection system, characterized in that: The system includes a vertical antenna and a horizontal antenna for acquiring vertical and horizontal electric field signals of a space lightning radiation source; an integration circuit for converting the electric field signal into a voltage; a high-pass amplifier circuit for filtering out clutter signals from the integrated voltage signal to perform waveform recognition and matching of the radiation signal and amplify the signal; a sampling analog-to-digital conversion circuit for sampling the signal output by the high-pass amplifier circuit and converting the analog signal into a digital signal; a radio positioning antenna for acquiring lightning direction information of the lightning radiation source; and an embedded Linux system for calculating the distance to the lightning radiation source by combining the digital signal and the lightning direction information. The embedded Linux system calculates the distance of the lightning radiation source based on the digital signal using the EE method of electric field measurement, that is, the distance between the radiation source and the observation point; The specific steps of the EE method of electric field measurement are: Step 1. According to the field superposition principle, arbitrarily oriented radiating dipoles Decompose the spatial coordinates into horizontal left and right components , horizontal front-back component and vertical component The projection formula in three directions is as follows: （1） in, is the spatial angle between the radiation source and the receiver; Step 2. Based on the radiating dipole of , ,and Projection in three directions, then , The electric fields generated by the projection are projected into the spatial coordinate system, and the radiation dipole is obtained after projection Components of the electric field; Step 3. Based on radiating dipole The components of the electric field are obtained by the square relationship of the vertical and horizontal values ​​of the electric field components of the radiating dipole; Step 4. Obtain the lightning radiation source distance based on the square relationship between the vertical and horizontal values ​​of the electric field components of the radiation dipole; In step 2, the radiating dipole The specific calculation formula of the components of the electric field is: For the vertical component , the electric field components are calculated 、 and ,in, Represents the vertical component of the radiating dipole received by the vertical antenna The horizontal electric field components generated are Represents the vertical component of the radiating dipole received by the vertical antenna The horizontal front and rear electric field components generated, Indicates that the vertical antenna receives the vertical component of the radiating dipole The vertical electric field component generated is: （2） For horizontal left and right components , the electric field components are calculated 、 and ,in, Indicates the horizontal left and right components of the radiating dipole received by the horizontal antenna The horizontal electric field components generated are Indicates the horizontal left and right components of the radiating dipole received by the horizontal antenna The horizontal front and rear electric field components generated, Indicates that the horizontal antenna receives the horizontal left and right components of the radiating dipole The vertical electric field component generated is: （3） For horizontal front-back component , the electric field components are calculated 、 and ,in, Represents the horizontal front and rear components of the radiating dipole received by the horizontal antenna The horizontal electric field components generated are Represents the horizontal front and rear components of the radiating dipole received by the horizontal antenna The horizontal front and rear electric field components generated, Indicates that the horizontal antenna receives the horizontal front and rear components of the radiating dipole The vertical electric field component generated is: （4） in, is the wave number, is the distance between the detection point and the radiation point, that is, the distance from the lightning radiation source, is the vertical distance between the detection point and the radiation, is the vacuum dielectric constant of the antenna plate, is the spatial angle between the field intensity generated by the radiating dipole component and the detection point, is a given constant, 、 、 、 、 、 、 、 are all intermediate quantities, In complex exponential form, in The plural number in .

2. The airborne lightning detection system according to claim 1, wherein: Also included is weather radar for detecting thunderstorms.

3. The airborne lightning detection system according to claim 1, wherein: In step 3, based on the radiating dipole The components of the electric field are obtained by the formula for the square relationship between the vertical and horizontal values ​​of the electric field components of the radiating dipole: （5） Simplifying to get: （6） in, is the altitude of the detection point, 、 、 and To simplify the substitution.

4. The airborne lightning detection system according to claim 3, wherein: The step 4 is based on formula 5 and is to obtain the vertical and horizontal values ​​of the electric field components of the radiation dipole, the wave number of the radiation source, and the altitude of the observation point by receiving, and to obtain the distance between the radiation source and the observation point by inversion.

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