A traffic monitoring antenna receiving channel phase and array surface error joint calibration method

Abstract

The application discloses a traffic monitoring antenna receiving channel phase and array error joint calibration method, comprising the following steps: S1) establishing a TCAS antenna array model; S2) establishing a TCAS antenna far-field antenna calibration model; S3) moving a radiation source to a preset mark position to emit a calibration signal, so that each receiving channel antenna of the TCAS receives the calibration signal; S4) repeating S3 until the radiation source traverses all preset mark positions; S5) performing FFT processing on the received signal after mixing to obtain a received signal spectrum; S6) searching for a spectrum peak of the received signal spectrum to calculate a phase difference between a reference channel and a channel to be calibrated; S7) using a least square method to solve a fixed phase difference and an installation error; and S8) compensating for the channel phase by using the solving result to complete the calibration. The application can comprehensively calibrate the influence of the channel fixed phase difference and the antenna array element position coordinate error, and further improves the accuracy of the antenna channel calibration.

Description

Technical Field

[0001] This invention relates to an antenna channel error calibration method, and more particularly to a method for joint calibration of phase and array error of a traffic monitoring antenna receiving channel. Background Technology

[0002] The Integrated Surveillance System (ISS) is a major component of modern aircraft avionics systems, integrating functions such as weather, traffic, and terrain surveillance. Traffic surveillance antennas are a crucial part of the ISS's traffic surveillance function, used for the radiation and reception of radio frequency signals from the Traffic Collision Avoidance System (TCAS), transponder (XPDR), and Automatic Dependent Surveillance-Broadcast (ADS-B). The TCAS utilizes a secondary radar mechanism to detect the positions of other nearby aircraft, analyzing the signals received by the traffic surveillance antennas to obtain the distance, altitude, and angle information of the target aircraft relative to the aircraft. Distance information is calculated based on the received signal delay, altitude information is obtained directly through message parsing, while angle information requires processing based on signal differences between the traffic surveillance antenna receiving channels.

[0003] To ensure flight safety, TCAS (Traffic Collision Avoidance System) is widely used in modern civil aircraft to mitigate potential collision risks between aircraft. The proper functioning of TCAS relies on acquiring the position of surrounding monitored target aircraft. The calculation of the target aircraft's horizontal azimuth depends primarily on the signal differences between different traffic antenna channels. Therefore, calibrating these different traffic antenna channels is crucial for accurately measuring the target's horizontal azimuth.

[0004] Currently, the TCAS system for civil aircraft generally uses four antenna channels for horizontal azimuth measurement. For scenarios involving horizontal azimuth measurement of four-channel traffic antenna arrays, existing traffic monitoring antenna receiving channel calibration mainly calibrates the fixed phase difference of the channels, while ignoring the influence of antenna element position deviations caused by factors such as installation errors, thus affecting the overall effect of channel calibration.

[0005] Accurately acquiring the target aircraft's angle information is crucial for TCAS to provide correct avoidance guidance (RA). Antenna channel errors severely affect the accuracy of the TCAS system's calculation of the target aircraft's angle, thus preventing the TCAS system from providing correct avoidance instructions. Therefore, antenna channel calibration is necessary to reduce antenna channel errors.

[0006] Currently, mainstream antenna channel calibration methods include: Fast Fourier Transform (FFT), matrix inversion, near-field scanning, rotation vector method, mutual coupling calibration, and commutation method. Calibration methods for TCAS antennas are scarce; existing technologies primarily focus on array antenna calibration methods.

[0007] The paper "Research on TCAS Receiver Channel Phase Calibration Technology" (Shi Zhiju et al., Proceedings of the 8th International Forum on Civil Aircraft Avionics) proposes a phase calibration method for TCAS receive channel antennas. Based on the causes of antenna errors, this method establishes an antenna error calibration model, uses FFT to obtain the frequency domain calibration factor of each channel relative to the reference channel, and then uses the frequency domain calibration factor to perform phase calibration on each channel. Simulation results show that this method effectively reduces the fixed phase difference of TCAS receive antenna channels. The hardware design of this method includes an additional built-in calibration excitation source, two additional calibration paths, and two path switching switches. During phase calibration, the path switches must be switched sequentially to select two ports of the TCAS as radiation sources; then, the signals from other paths are analyzed by A / D conversion. This method requires additional hardware design (built-in calibration excitation source, two additional calibration paths, and two path switching switches), thus increasing hardware design costs. Furthermore, this method can only calibrate the phase difference between channels, while TCAS antennas inevitably have certain installation errors during actual deployment; this method fails to calibrate for TCAS array installation errors. Furthermore, the calculation of path difference depends on accurate array size values, which are usually calculated using the design values ​​of the TCAS array. However, due to the manufacturing precision issues of TCAS antennas, the actual size values ​​of the TCAS array will deviate from the design values ​​to some extent. Therefore, in practical applications, this will affect the effectiveness of the aforementioned channel phase difference calibration method.

[0008] Chinese patent document CN114070704B, entitled "A Multi-Channel Transceiver and Amplitude / Phase Calibration Method for Collision Avoidance Devices," proposes a method for calibrating the amplitude and phase error of a TCAS multi-channel antenna. This method uses first and second calibration signals to calibrate the upper and lower antennas of the TCAS. After multiple calibrations, the final calibration coefficients are stored in non-volatile memory. This method avoids the need for external host computer software, power meters, and other auxiliary instruments, automatically completing the amplitude and phase calibration of the signal. The calibration process is unmanned, improving the efficiency and accuracy of TCAS antenna debugging. However, this method is also based on a relatively complex hardware design, determining the calibration coefficients by comparing the amplitude and phase differences between channels. Compared to conventional designs, the method provided in this patent document requires a large-scale addition of hardware design, incurring additional hardware design and implementation costs. The technical solution in this document directly calculates the amplitude and phase of the channel sampling data without further processing; this makes it difficult to obtain further signal processing gain, thus making it susceptible to channel noise and reducing the reliability of the algorithm.

[0009] As can be seen from the above, although the existing methods can calibrate channel phase errors to a certain extent, they require certain hardware modification costs and do not calibrate the installation errors of the TCAS antenna, thus failing to eliminate the impact of array surface errors on TCAS angle measurement performance and limiting their practical application. Since it is impossible to guarantee perfectly consistent element spacing in the TCAS array during actual installation, and the installation state is not ideal, it is necessary to calibrate the installation errors of the TCAS antenna to ensure the channel accuracy of the antenna. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a method for joint calibration of phase and array error of traffic monitoring antenna receiving channel. Without further hardware modification, it can comprehensively calibrate the effects of fixed phase difference of channel and position coordinate error of antenna array elements, thereby further improving the accuracy of antenna channel calibration.

[0011] The technical solution adopted by this invention to solve the above-mentioned technical problems is to provide a joint calibration method for phase and array error of traffic monitoring antenna receiving channel, including the following steps: S1) Based on the physical layout of the TCAS antenna multi-element array, select one TCAS element as a reference, and simultaneously consider the error of the antenna elements to establish a TCAS antenna array model; S2) Establish a far-field antenna calibration model of the TCAS antenna and determine the deployment position of the far-field radiation source relative to the TCAS antenna; S3) Move the radiation source to a preset marked position, transmit a far-field calibration signal with a fixed carrier frequency, and collect the reception data of each channel of the TCAS. S4) Repeat step S3 until the radiation source traverses all the positions of the preset marks; S5) For each receiving channel, perform FFT processing on the received signal to obtain the spectrum of the received signal; S6) Search for the spectral peaks of the spectrum of each receiving channel and calculate the phase difference between the reference channel and the channel to be calibrated; S7) Use the phase difference and array antenna phase difference expression obtained in step S6 to construct a system of equations, and use the least squares method to solve for the fixed phase difference and installation error; S8) Use the obtained fixed phase difference and installation error to compensate for the channel phase and complete the calibration.

[0012] Further, step S1 includes: the TCAS antenna adopts a 4-antenna array configuration, selects one antenna as the reference antenna, establishes a horizontal XY coordinate system, with the reference antenna as the origin, the direction of the nose as the positive X-axis, and the direction perpendicular to the X-axis as the Y-axis, and then establishes a rectangular coordinate system. The theoretical coordinates of each antenna are then expressed as:

[0013]

[0014] In the formula, Indicates antenna x Axis coordinates Indicates antenna y Axis coordinates d Indicates the element spacing; installation error is included. and The actual coordinates of the antenna are then represented as:

[0015] .

[0016] Furthermore, step S2 considers the fixed phase difference of the antenna channel and the phase difference caused by the path difference, and further calculates the phase difference of different channels relative to the reference array element channel, establishing the phase relationship between different receiving channels and the reference channel. The corresponding calculation formula is as follows:

[0017]

[0018] In the formula, This indicates the fixed phase difference of the TCAS antenna channel. For the signal wavelength, θ This indicates the angular position of the far-field radiation source.

[0019] Further, step S3 includes: marking positions at several predetermined angles in the field, assembling an omnidirectional radiating antenna on the radiation source; and moving the radiation source into the field. A calibration signal is transmitted at the angular position, and the TCAS antenna receives the calibration signal, recording the angle reached by the TCAS antenna target at that position. And receive signals.

[0020] Furthermore, the number n of repeated preset angle positions in step S4 is set to 72. ， Starting from the 0° position, traverse the marked positions from 0° to 360° at equal intervals of 5°.

[0021] Further, step S5 includes:

[0022] For a far-field signal with a fixed carrier frequency, after mixing, the first... i Signal received by each element channel It can be represented as follows:

[0023]

[0024] In the formula, i Representing different array element channels, Indicates signal amplitude. Indicates the signal phase. Indicates the signal carrier frequency. The frequency of the local oscillator signal is represented by the frequency. An FFT is performed on each group of received signals to obtain the received signal spectrum.

[0025]

[0026] According to the above formula, each group of received signals will have a pair of spectral peaks in its spectrum.

[0027] Furthermore, in step S5, the carrier frequency of the received signal is 1090MHz, and the signal wavelength is... The value is 0.27m, and the element spacing is... The initial phase of the channel is set to The signal-to-noise ratio of the receiving channel is set to 20dB. In step S5, the frequency of the local oscillator is 1060Hz, the frequency of the intermediate frequency signal after mixing is 30MHz, and the ADC sampling rate of the intermediate frequency signal is set to 90MSamples / s, so that each group of received signals has a pair of spectral peaks at 30MHz and -30MHz.

[0028] Further, step S6 includes: performing peak detection on the spectrum of each receiving channel to obtain spectral peak data, and then calculating the phase difference between different channels relative to the reference channel. The mixed signal spectrum will... and A spectral peak is formed at one of the two locations, and the spectral peak signals at these two locations have a dual relationship. One of the spectral peaks is selected for calculation, and the spectrum of the reference channel signal is chosen to be at... The spectrum of the peak signal and the spectrum of the channel signal to be calibrated are in The spectral peak signal is used to calculate the phase difference between the reference channel and the channel to be calibrated. :

[0029]

[0030] In the formula, angle(*) represents the angle calculation, and the subscript 0 represents the reference channel.

[0031] Further, step S7 includes: using during the calibration process n By analyzing the received signals from several far-field calibration sources at different angles and simultaneously using the far-field antenna calibration model in S2, the following relationship can be obtained:

[0032]

[0033] Considering the effect of noise, the above formula can be further expressed as:

[0034]

[0035] In the formula, N This represents the fixed phase difference caused by noise. X This is the deviation that needs to be calibrated. H From the target angle A defined action matrix, Y It is the phase difference between the received channels as measured:

[0036]

[0037] The calculation result obtained using the least squares method can be expressed as:

[0038]

[0039] The fixed phase difference of each channel was calculated. , , and installation errors of each channel , , , , , .

[0040] Furthermore, step S8 involves obtaining the fixed phase difference from step S7. , , and installation errors of each channel , , , , , The parameters are converted into TCAS calibration configuration parameters to complete the joint calibration process of phase and array error of the traffic monitoring antenna receiving channel.

[0041] Compared with existing technologies, this invention offers the following advantages: The joint calibration method for phase and array error of the traffic monitoring antenna receiving channel provided by this invention can be implemented entirely within the conventional TCAS basic link hardware design, requiring no further hardware modifications. Simultaneously, array error is calculated while calibrating the channel phase error, achieving joint calibration and significantly improving TCAS angle measurement performance. This invention can complete calibration even when the antenna is already installed, eliminating the need for repeated antenna disassembly and reassembly during calibration, thus improving calibration efficiency. Furthermore, considering installation errors during actual antenna installation, the modeling process incorporates an optimal estimation method that comprehensively considers array error and fixed phase error of the channel, further enhancing the accuracy of antenna channel calibration. Attached Figure Description

[0042] Figure 1 This is a flowchart illustrating a TCAS antenna receiving channel error calibration method provided in this invention.

[0043] Figure 2 This is an antenna array model for a TCAS antenna receiving channel error calibration method provided in this invention.

[0044] Figure 3 This is a far-field calibration model of a TCAS antenna receiving channel error calibration method provided in this invention example;

[0045] Figure 4 This is a flowchart of the analog signal processing of the receiving channel in a TCAS antenna receiving channel error calibration method provided by an example of the present invention;

[0046] Figure 5 This is a schematic diagram of the antenna path difference for a TCAS antenna receiving channel error calibration method provided in this invention.

[0047] Figure 6This is an ADC data FFT spectrum diagram of a TCAS antenna receiving channel error calibration method provided in this invention. Detailed Implementation

[0048] The present invention will now be further described with reference to the accompanying drawings and embodiments.

[0049] TCAS uses a four-element traffic antenna for horizontal azimuth measurement. Calculating the target horizontal azimuth requires obtaining the difference in received signals between channels, typically based on amplitude or phase comparison methods. Amplitude comparison uses the amplitude difference between antenna channels to calculate the horizontal azimuth value, while phase comparison uses the phase difference between antenna channels. Both methods rely on obtaining correct receiving channel parameters.

[0050] When TCAS traffic antennas are installed on aircraft, installation errors during assembly inevitably result in a certain installation error between the actual antenna array and the designed antenna array. When the TCAS is in the installed state, it is difficult to obtain precise data on the antenna array position using direct dimensional measurements. Furthermore, deviations due to practical factors such as unequal antenna feed line lengths lead to a fixed phase error in the antenna receiving channel. To address the antenna array installation errors and fixed phase errors in the receiving channel under actual TCAS installation scenarios, this invention provides a calibration process based on the least squares method, which can achieve joint calibration of both antenna array errors and phase errors.

[0051] The purpose of this invention is to overcome the shortcomings of the prior art and provide a joint calibration algorithm for the phase and array error of the TCAS traffic antenna receiving channel. First, the mathematical model of channel deviation is summarized and analyzed. Then, based on the mathematical model of channel deviation, a method for calibration measurement is systematically proposed for each variable related to the deviation. Finally, the channel calibration algorithm proposed in this paper is systematically simulated and tested in a simulation environment, and the feasibility of the channel calibration algorithm is systematically verified.

[0052] The TCAS antenna receiving channel error calibration method provided by this invention considers the installation errors generated during the actual installation of the TCAS antenna in the modeling process, making the algorithm model more consistent with real-world scenarios. Furthermore, the least squares method is used in the calculation to solve for installation errors and fixed phase differences, improving the accuracy of TCAS antenna channel calibration. This invention also allows calibration to be performed even after the antenna is already installed, avoiding the repeated disassembly and reassembly of the antenna on the aircraft during calibration. This effectively improves calibration efficiency, reduces installation error fluctuations caused by repeated antenna assembly, and further enhances calibration accuracy.

[0053] Please see Figure 1 The method for joint calibration of phase and array error of traffic monitoring antenna receiving channel provided by the present invention has the following specific implementation steps:

[0054] Step S1: Based on the physical layout of the 4-element TCAS antenna, select one TCAS element as the reference, and at the same time consider the error of the antenna elements to establish the array model of the aircraft TCAS antenna.

[0055] Step S2: Establish a far-field calibration model of the aircraft TCAS antenna. Based on this, considering the fixed phase difference of the antenna channel and the phase difference caused by the path difference, further calculate the phase difference of different channels relative to the reference array element channel.

[0056] Step S3: Move the radiation source to The corresponding location transmits a calibration signal, causing each receive channel antenna of the TCAS to receive the calibration signal; the target arrival angle of the signal at that location is recorded. And the received signal of each channel;

[0057] Step S4: Repeat step S3 until the radiation source traverses all the marked positions; the orientation of the radiation source should preferably cover 0 to 360°, preferably, it can be processed in an equally spaced manner with an interval of 5°, then n = 360 / 5 = 72;

[0058] Step S5: For each receiving channel, perform FFT processing on the received signal to obtain the received signal spectrum;

[0059] Step S6: Search for the spectral peaks of each receiving channel and calculate the phase difference between the reference channel and the channel to be calibrated;

[0060] Step S7: Construct a system of equations using the phase difference and array antenna phase difference expressions obtained in step S6, and solve for the fixed phase difference and installation error using the least squares method;

[0061] Step S8: Use the fixed phase difference and installation error obtained from the solution to compensate for the channel phase and complete the calibration.

[0062] Specifically, this embodiment establishes a realistic array model based on antenna installation errors, and establishes a far-field antenna calibration model based on the actual TCAS antenna system of an aircraft, utilizing the radiation source in... n A known angle is used to transmit a calibration signal, which is then measured by the TCAS antenna. n The calibration signal is mixed, and then the received signal is transformed to the frequency domain using FFT. The signal's spectral peaks are then searched for. The phase difference between the reference channel and the channel to be calibrated is calculated by determining the spectral peak signal at the location. Based on the phase difference expression of the array antenna, a set of equations relating the phase difference, array spacing, and the signal target arrival angle is constructed. The fixed phase difference and installation error are solved using the least squares method. The TCAS antenna channel is then calibrated using the obtained fixed phase difference and installation error.

[0063] Further, step S1 establishes an array model of the aircraft's TCAS antenna.

[0064] Specifically, in this embodiment, the TCAS antenna adopts a 4-antenna array configuration. One antenna is selected as the reference antenna, and a horizontal XY coordinate system is established with the reference antenna as the origin and the direction of the aircraft head as the coordinate axis. x The positive direction of the axis, perpendicular to x axial direction y Establish a rectangular coordinate system along the axis. The theoretical coordinates of each antenna can then be expressed as:

[0065]

[0066] In the formula, Indicates antenna x Axis coordinates Indicates antenna y Axis coordinates d Indicates the spacing between array elements;

[0067] like Figure 2 As shown, the white dots represent the theoretical antenna array model. Installation errors are factored in. and Then, the actual coordinates of each antenna can be expressed as:

[0068]

[0069] like Figure 2 As shown, the black dots represent the actual antenna array model, and the above formula represents the coordinates of each antenna in the array model.

[0070] Further, step S2 establishes a far-field antenna calibration model for the aircraft's TCAS antenna.

[0071] Specifically, such as Figure 3 The image shows the far-field antenna calibration model for an aircraft TCAS antenna. Calibration is performed in the far-field space. n There are [number] positions, and the target angle for each position is [angle]. White dots indicate the marked locations where no radiation source is placed, while black dots indicate the locations where the radiation source is placed. The radiation source emits omnidirectional radiation signals at each marked location.

[0072] Further, step S3 moves the radiation source to... The corresponding calibration position transmits a calibration signal, and the TCAS's four-channel receiving antenna receives the calibration signal, recording the target angle of arrival at that position. And the received signals of 4 channels.

[0073] Specifically, placing the radiation source At the corresponding calibration location, an omnidirectional radiation calibration signal is emitted. The aircraft uses a TCAS antenna to receive the calibration signal and records the received signals from the four TCAS antennas and the corresponding target angle of arrival. .

[0074] Further, step S4 repeats step S3 until the radiation source has traversed all the marked locations.

[0075] Specifically, in the antenna far-field calibration model, the following were calibrated: n At each marked location, the radiation source needs to transmit a calibration signal so that the antenna receives it. n Calibration signals for different target angles.

[0076] Further, after mixing in step S5, the received signal is subjected to FFT processing to obtain the received signal spectrum.

[0077] Specifically, such as Figure 4 As shown, after the received signal enters the receiving channel, it is first filtered, then mixed, and after mixing, the time-domain signal is obtained using A / D sampling. For the first... i The time-domain signal of the received signal of each array element channel is:

[0078]

[0079] Perform an FFT on the time-domain signal to obtain the signal spectrum:

[0080]

[0081] Further, in step S6, the received signal spectrum peaks are searched, and the phase between the reference channel and the channel to be calibrated is calculated.

[0082] Specifically, according to the signal spectrum formula in step S5, the frequency domain signal in... and A spectral peak is formed at a certain point. Since the time-domain signal is a real signal, the two spectral peaks are dual in the frequency domain. Therefore, this invention only needs to select one of the spectral peaks for subsequent processing. Calculate the phase difference between the channel to be calibrated and the reference channel based on the spectral peak at the specified location.

[0083]

[0084] Further, in step S7, the phase difference and array antenna phase difference expressions obtained in step S6 are used to construct a set of equations, and the fixed phase difference and installation error are solved using the least squares method.

[0085] Specifically, such as Figure 5 The diagram shows the path difference between antennas. The path difference of the antenna to be calibrated is:

[0086]

[0087] The phase difference between the reference antenna and the antenna to be calibrated is solved using the path difference between the antennas:

[0088]

[0089] In the formula, f This represents the signal frequency. Based on the above equation and the phase difference obtained in step 6, we can obtain the following equation:

[0090]

[0091] In step 4, the TCAS antenna received... n Given calibration signals at different angles, the above equation is transformed into a system of equations:

[0092]

[0093] Considering noise error, the least squares expression is:

[0094]

[0095] According to the above equation, the derived system of equations is a standard least squares problem:

[0096]

[0097] To perform channel calibration, it is necessary to estimate the values ​​of the coefficient matrix X in order to minimize the root mean square error of the X estimate. The estimated value of X can be obtained by using the least squares estimation method.

[0098] Solve the system of equations using the least squares method:

[0099]

[0100] The fixed phase difference of each channel was calculated. , , and installation errors of each channel , , , , , .

[0101] Furthermore, step S8 uses the fixed phase difference and installation error obtained from the solution to compensate for the channel phase, thus completing the calibration.

[0102] Specifically, using , , , , , , , , Calibrate the fixed phase difference and installation error of the TCAS antenna channel. Convert the calibration coefficients into TCAS calibration configuration parameters to complete the joint calibration process of phase and array error of the traffic monitoring antenna receiving channel.

[0103] The TCAS antenna receiving channel calibration method of the present invention can also be extended to other multi-faceted phased array antennas; only the forms of the X matrix and Y matrix need to be changed accordingly, while the H matrix remains basically the same.

[0104] In summary, compared to existing TCAS antenna channel error calibration methods, the TCAS antenna receiving channel calibration method provided in this example solves two major problems: installation errors caused by the installation process and the need for repeated disassembly and reassembly for channel calibration after installation in current TCAS systems. In this example, a far-field radiation source is used to calibrate the already installed TCAS antenna receiving channel, avoiding repeated antenna disassembly and reassembly, effectively improving calibration efficiency and avoiding the problem of installation error fluctuations caused by repeated antenna assembly. The calibration algorithm model considers antenna installation errors, making the algorithm model more consistent with reality. The least squares method is an optimization algorithm, and this algorithm uses least squares to solve for the fixed phase difference and installation error, resulting in optimal calculation results. Compared to other TCAS antenna channel calibration algorithms, the calibration accuracy of this invention is higher.

[0105] To verify the effectiveness of the TCAS antenna receiving channel error calibration method provided in this application, this embodiment further illustrates the method through the following simulation experiment.

[0106] In the simulation scenario, the received signal carrier frequency is 1090MHz, and the signal wavelength is... The value is 0.27m, and the element spacing is... The initial phase of the channel is set to The fixed phase difference and installation error are set to 5%. The signal-to-noise ratio of the receiving channel is set to 20dB. The local oscillator frequency is 1060Hz, the intermediate frequency (IF) after mixing is 30MHz, and the ADC sampling rate of the IF signal is set to 90M Samples / s. Figure 6 The spectrum shown is obtained by mixing the received signal, sampling it with an ADC, and then performing FFT processing. Spectral peaks appear at 30MHz and -30MHz in the spectrum. The simulation results are consistent with the theoretical derivation above.

[0107] To verify the algorithm's performance, 1000 Monte Carlo experiments were conducted. The table below shows the calibration performance comparison results between the algorithm of this invention and the existing FFT channel calibration algorithm. The results show that the root mean square error (RMSE) of the algorithm of this invention is smaller, and compared with the existing algorithm, the algorithm of this invention has higher calibration accuracy and better performance.

[0108]

[0109] Installation error setting value:

[0110] Δx1= 0.00364077, Δy1= 0.00364077

[0111] Δx2= 0.00364077, Δy2= -0.00364077

[0112] Δx3= -0.00364077, Δy3= -0.00364077

[0113] Simulation calculation values ​​of installation error:

[0114] Δx1= 0.00366224, Δy1= 0.00362249

[0115] Δx2= 0.00365146, Δy2= -0.00360518

[0116] Δx3= -0.00356551, Δy3= -0.00360943.

[0117] As can be seen, this invention can simultaneously obtain relatively accurate antenna receiving channel array installation errors. Antenna receiving channel phase errors are easier to analyze and model than array surface errors, and the corresponding calibration process is simpler to implement. Therefore, existing calibration methods in the TCAS field mainly focus on channel amplitude and phase calibration. This invention combines antenna receiving channel array installation errors and channel phase errors for simultaneous calibration, avoiding the effect of array installation errors being masked by the fixed phase effect of the channel. This solves the technical problem that existing FFT channel calibration algorithms can only calculate channel phase errors and cannot calibrate array surface errors.

[0118] The calibration method of this invention can be implemented entirely within the conventional TCAS basic link hardware design, without any further hardware modifications. Simultaneously, the array surface error is calculated while calibrating the channel phase error, achieving joint calibration and significantly improving TCAS angle measurement performance. This method comprehensively considers array surface error and channel fixed phase error factors, completing a complete and rigorous mathematical model, and theoretically verifying the feasibility of the joint calibration algorithm. Furthermore, based on the mathematical model, an optimal estimation method is employed to design in detail the optimal estimation method for array surface error and channel phase error, further improving the accuracy of antenna channel calibration.

[0119] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be defined by the claims.

Claims

1. A method for joint calibration of phase and array error of a traffic monitoring antenna receiving channel, characterized in that, Includes the following steps: S1) Based on the physical layout of the TCAS antenna multi-element array, select one TCAS element as the reference, and at the same time consider the error of the antenna elements to establish a TCAS antenna array model. S2) Establish a far-field antenna calibration model for the TCAS antenna and calibrate it in the far-field space. n One location, n The value is 72, and the target angle corresponding to each position is... θ i ( i = 1,2,…, n This is used to transmit calibration signals from the radiation source at different angles; and to determine the deployment position of the far-field radiation source relative to the TCAS antenna. S3) Move the radiation source to the preset marked position, transmit the far-field calibration signal with a fixed carrier frequency, and collect the digital sampling signal of each receiving channel antenna of the TCAS antenna; S4) Repeat step S3 until the radiation source has traversed all the positions of the preset markers; S5) For each receiving channel, digitally sample the signal, perform FFT processing on the received signal, and obtain the spectrum of the received signal; S6) Search for the spectral peaks of each receiving channel and calculate the phase difference between the reference channel and the channel to be calibrated; S7) Construct a system of equations using the phase difference and array antenna phase difference expressions obtained in step S6. The fixed phase difference and installation error are solved using the least squares method; where N represents the phase difference effect caused by noise, X is the deviation that needs to be calibrated and measured, including the installation errors Δx and Δy of each antenna channel and the fixed phase difference ΔΦ, H is the action matrix determined by the target arrival angle, and Y is the observation matrix, whose elements are the phase differences of each antenna channel at different angles obtained in step S6. Establish the phase relationship between different antenna channels i and the reference channel. i The corresponding array antenna phase difference expressions for = 1, 2, 3 are: In the formula, This represents the fixed phase difference between antenna channel i (i = 1,2,3) and reference channel 0. For the signal wavelength, θ Indicates the angular position of the far-field radiation source. Indicates antenna channel i x Theoretical values ​​of axis coordinates Indicates antenna channel i y Theoretical values ​​of axis coordinates Indicates the installation error of antenna channel i x Components of the axis, Indicates the installation error of antenna channel i y The components of the axis; S8) The channel phase is compensated using the fixed phase difference and installation error obtained from the solution, and the calibration is completed.

2. The method for joint calibration of phase and array error of traffic monitoring antenna receiving channel as described in claim 1, characterized in that, Step S1 includes: The TCAS antenna uses a 4-antenna array configuration. One antenna is selected as the reference antenna, and a horizontal XY coordinate system is established. With the reference antenna as the origin, the direction of the nose as the positive x-axis, and the direction perpendicular to the x-axis as the y-axis, a rectangular coordinate system is established. The theoretical coordinates of each antenna are then expressed as follows: In the formula, Indicates antenna x Axis coordinates Indicates antenna y Axis coordinates d Indicates the element spacing; considering installation errors. and The actual coordinates of the antenna are then represented as: 。 3. The method for joint calibration of phase and array error of traffic monitoring antenna receiving channel as described in claim 1, characterized in that, Step S3 includes: marking positions at several predetermined angles in the field; assembling an omnidirectional radiating antenna on the radiation source; and moving the radiation source into the field. The position of the angle transmits a calibration signal. The angle ranges from 0 to 360°; the TCAS antenna receives the calibration signal and records the target angle reached by the TCAS antenna at that location. And receive signals.

4. The method for joint calibration of phase and array error of traffic monitoring antenna receiving channel as described in claim 3, characterized in that, In step S4, the number of repeated preset angle positions n is set to 72. ， Starting from the 0° position, traverse the marked positions from 0° to 360° at equal intervals of 5°.

5. The method for joint calibration of phase and array error of traffic monitoring antenna receiving channel as described in claim 1, characterized in that, Step S5 includes: For a far-field signal with a fixed carrier frequency, after mixing, the first... i Signal received by each element channel It can be represented as follows: In the formula, i Representing different array element channels, Indicates signal amplitude. Indicates the signal phase. Indicates the signal carrier frequency. The frequency of the local oscillator signal is represented by the frequency. An FFT is performed on each group of received signals to obtain the received signal spectrum. According to the above formula, each group of received signals will have a pair of spectral peaks in its spectrum.

6. The method for joint calibration of phase and array error of traffic monitoring antenna receiving channel as described in claim 1, characterized in that, In step S5, the received signal carrier frequency is 1090MHz, and the signal wavelength is... The value is 0.27m, and the element spacing is... The initial phase of the channel is set to The signal-to-noise ratio of the receiving channel is set to 20dB. In step S5, the frequency of the local oscillator is 1060MHz, the frequency of the intermediate frequency signal after mixing is 30MHz, and the ADC sampling rate of the intermediate frequency signal is set to 90MSamples / s, so that each group of received signals has a pair of spectral peaks at 30MHz and -30MHz.

7. The method for joint calibration of phase and array error of traffic monitoring antenna receiving channel as described in claim 5, characterized in that, The processing step S6 includes: Peak detection is performed on the spectrum of each receiving channel to obtain spectral peak data. Then, the phase difference between different channels relative to the reference channel is calculated. The spectrum of the mixed signal will be... and A spectral peak is formed at one of the two locations, and the spectral peak signals at these two locations have a dual relationship. One of the spectral peaks is selected for calculation, and the spectrum of the reference channel signal is chosen to be at... The spectrum of the peak signal and the spectrum of the channel signal to be calibrated are in The spectral peak signal is used to calculate the phase difference between the reference channel and the channel to be calibrated. : In the formula, angle(*) represents the angle calculation, and the subscript 0 represents the reference channel.

8. The method for joint calibration of phase and array error of traffic monitoring antenna receiving channel as described in claim 2, characterized in that, Step S7 includes: Used during calibration n The received signals from three far-field calibration sources at different angles, with n set to 72, and using the far-field antenna calibration model from step S2, yield the following relationship: Indicates the location of the far-field calibration source. n The angle of the far-field radiation source, Indicates when the far-field calibration source is in The phase difference between the reference channel 0 and the channel i to be calibrated (i = 1,2,3) at the position; Considering the effect of noise, the above formula can be further expressed as: ； The calculation result obtained using the least squares method can be expressed as: The fixed phase difference of each channel was calculated. , , and installation errors of each channel , , , , , .

9. The method for joint calibration of phase and array error of traffic monitoring antenna receiving channel as described in claim 8, characterized in that, Step S8 will obtain the fixed phase difference from step S7. , , and installation errors of each channel , , , , , The parameters are converted into TCAS calibration configuration parameters to complete the joint calibration process of phase and array error of the traffic monitoring antenna receiving channel.

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