Dynamic calibration method for radar antenna zero drift based on single-beam precision measurement

Abstract

The invention discloses a single-beam-based precise measurement radar antenna zero drift dynamic calibration method, which comprises the following steps of: arranging precise measurement radar transmitting end and receiving end test instruments, aligning an azimuth axis of an antenna pedestal telescope of a receiving end to an optical axis marker line at a signal source, and then carrying out mechanical error calibration on an antenna zero position. Then, the radiation field intensity value of the antenna is measured through step-by-step scanning of a frequency spectrograph, data segments symmetrically distributed near the zero depth value are selected, virtual zero point coordinates are constructed through a linear fitting algorithm, an error correction model is established based on the virtual zero point coordinates, and error values of different working frequency points are determined; and determining the zero offset compensation amount of each working frequency point, and completing antenna zero drift calibration. Based on the scheme, zero calibration is jointly realized on the antenna mechanical section and the rear-end signal processing side, error compensation is carried out, the tracking precision is greatly improved, and the method is simple and reliable, can be widely applied to the radar equipment antenna calibration process, and has good application prospects and comprehensive benefits.

Description

Technical Field

[0001] This invention belongs to the field of radar antenna calibration, specifically relating to a method for calibrating the zero-drift state of a radar antenna based on single-beam precision measurement. Background Technology

[0002] During radar tracking, the radar antenna beam must be continuously aimed at a specific target. When the target drifts off-axis, the antenna must be able to provide an off-axis signal so that the radar servo system can drive the antenna to reduce errors and achieve target tracking.

[0003] Tracking radar antennas play two crucial roles in radar systems: first, ensuring sufficient antenna gain to provide adequate tracking range, a requirement consistent with search radar; and second, guaranteeing sufficiently high angular error sensitivity (angle measurement sensitivity) to enable continuous target tracking and accurate angle measurement. These are the characteristics of tracking radar antennas and the key design considerations.

[0004] The zero-value depth of the differential beam is another important indicator of the differential channel. It generally refers to the ratio of the electric field at the zero point of the differential pattern center to the electric field at the maximum value (the differential beam itself or the sum beam). It is related to the tracking accuracy of the radar. The deeper the zero-value depth, the smaller the tracking error.

[0005] In monopulse antennas, the differential lobe null depth is generally required to be below -30dB (relative to the maximum differential beam value); the size of the null depth is related to the quality of the high-frequency adder / subtractor adjustment in the feed line and the antenna's manufacturing and installation tolerances.

[0006] However, due to antenna manufacturing issues, conventional precision measurement radar antennas often exhibit zero-point drift. Under wide-bandwidth frequency agility, azimuth and elevation errors are caused by the superposition of random errors, inherent errors, and drift errors, reducing tracking accuracy. Conventional existing antenna calibration methods often neglect the problem of antenna zero drift. Under fixed-frequency tracking, the tracking error is not apparent, but under wide-bandwidth frequency agility, the tracking accuracy decreases significantly. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a method for zero-drift dynamic calibration of radar antennas based on single-beam precision measurement.

[0008] The specific technical solution for achieving the objective of this invention is as follows:

[0009] A method for zero-point drift dynamic calibration of radar antenna based on single-beam precision measurement includes the following steps:

[0010] Step 1: Set up the test instruments at the transmitting end and the receiving end of the precision measurement radar, and determine the optical axis marker line at the signal source;

[0011] Step 2: Align the azimuth axis of the antenna mount telescope at the receiving end with the optical axis mark line at the signal source;

[0012] Step 3: Perform mechanical error calibration of the antenna null position by adjusting the antenna mount at the receiving end;

[0013] Step 4: Measure the radiated field strength of the antenna using a spectrum analyzer in a step scan. By selecting data segments symmetrically distributed near the zero depth, construct the virtual zero coordinates using a linear fitting algorithm.

[0014] Step 5: Establish an error correction model based on virtual zero coordinates. By determining the error values ​​at different operating frequencies, determine the zero offset compensation amount at each operating frequency to complete the antenna zero drift calibration.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] The calibration method in this scheme achieves zero-position calibration and error compensation at both the antenna mechanical section and the back-end signal processing side, greatly improving tracking accuracy.

[0017] The calibration method of the present invention constructs virtual zero-point coordinates, combines the error values ​​of different operating frequencies, constructs an error correction model, and completes antenna null drift calibration at different frequencies. It can meet the dynamic error calibration under the condition of large bandwidth frequency agility and can significantly improve tracking accuracy.

[0018] This method is simple and reliable, and can be widely used in the antenna calibration process of radar equipment. It has good application prospects and comprehensive benefits.

[0019] The present invention will be further described below with reference to specific embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the calibration method for zero-drift dynamics of radar antenna based on single-beam precision measurement in this scheme.

[0021] Figure 2 This is a schematic diagram of the instrument connections for the precision measurement radar transmitter in this scheme.

[0022] Figure 3 This is a schematic diagram of the test instrument connection at the receiving end of this solution.

[0023] Figure 4 This is a schematic diagram of the optical axis calibration for this scheme.

[0024] Figure 5This is a schematic diagram of virtual zero-point coordinate fitting in this embodiment of the solution. Detailed Implementation

[0025] Example

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0028] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this application. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0029] Combination Figure 1 A method for zero-drift dynamic calibration of radar antenna based on single-beam precision measurement includes the following steps:

[0030] Step 1: Set up the test instruments at the transmitting end and the receiving end of the precision measurement radar, and determine the optical axis marker line at the signal source;

[0031] The test instruments at the transmitting end of the precision measurement radar include a microwave signal source, a microwave power amplifier, and a transmitting horn, which are connected in sequence, as follows: Figure 2 As shown;

[0032] Combination Figure 3The test instruments for the receiving end include a standard gain horn antenna, an antenna under test, a feed waveguide, an absorbing load, a four-way waveguide switch, and a spectrum analyzer.

[0033] The standard gain horn antenna and the antenna under test are mounted on the antenna mount and connected by a feed waveguide and a four-way waveguide switch, respectively. The four-way waveguide switch is connected to the spectrum analyzer. The standard gain horn antenna is used to radiate the signal source.

[0034] Step 2: Align the azimuth axis of the receiver's antenna mount telescope with the optical axis marker line at the signal source, such as... Figure 4 As shown;

[0035] Step 3: Perform mechanical error calibration of the antenna null position by adjusting the antenna mount at the receiving end.

[0036] Step 3-1: Adjust the mounting screws between the receiving antenna mount and the antenna under test. Specifically, adjust the length of the three mounting screws extending into the reflector on the high-frequency box of the antenna mount so that the azimuth zero depth at the center frequency point of the antenna under test meets the requirements. In this embodiment, the azimuth zero depth ZSΔH at the center frequency point is required to be ≤-30dB. When the azimuth zero point is cut, the center of the optical axis mark line at the signal source is at the azimuth zero value of the scale of the antenna mount telescope, that is, the "+" of the optical axis mark line at the signal source is at the azimuth zero value of the scale of the telescope.

[0037] Step 3-2: By adjusting the mounting screws between the receiving antenna mount and the antenna under test, the difference between the elevation axis of the antenna mount telescope and the optical axis mark line at the signal source is within the set range, for example, within ±5mrad, while the elevation zero depth value is less than the set threshold SLΔE≤-30dB.

[0038] Step 3-3: Step-by-step check whether the azimuth zero depth and elevation zero depth values ​​of the entire frequency band meet the requirements, for example, one test point every 100MHz; step-by-step check whether the difference between the azimuth zero position and elevation zero position of the entire frequency band and the theoretical value of the antenna is within the set range (±0.3mrad).

[0039] If the requirements are not met, the screw length must be readjusted until the full frequency band meets the specifications.

[0040] Step 4: Measure the antenna's radiated field strength using a spectrum analyzer with step scanning. When the antenna pattern exhibits an approximately symmetrical distribution near null depth, the linear portion deviating from the null point contains precise null location information. By selecting symmetrically distributed data segments near the null depth, a linear fitting algorithm is used to construct virtual null coordinates.

[0041] like Figure 5As shown, the linear model of the selected data segment is fitted using the least squares method, resulting in: y = kx + b, where y is the virtual antenna null point after fitting the frequency point calculated by the model, x is the antenna null point obtained by measurement, and b is the null point offset obtained by fitting.

[0042] If, ideally, the output should be 0 when the input is 0, then:

[0043] The real "virtual zero point" By solving 0= + get:

[0044]

[0045] Alternatively, b can be used directly as the zero-point offset, and the zero-point correction can be completed by subtracting b from the subsequent measurement value.

[0046] In this embodiment, the fitted slope obtained is 2.0560, the fitted intercept (zero offset estimate) is 0.2953, and the virtual zero position (input coordinates) is -0.1436.

[0047] Before zero-point correction, the mean of the data near the zero point is 0.2953; after correction, the mean of the data near the zero point is 0.0000. Zero-point offset compensation: 0.2953.

[0048] Step 5: Establish an error correction model based on virtual null coordinates. By determining the error values ​​at different operating frequencies, determine the null offset compensation amount for each operating frequency, and complete the antenna null drift calibration.

[0049] First, based on the zero-point offset obtained through fitting, a preliminary calibration model is obtained.

[0050]

[0051] However, this preliminary model uses a fixed error value for correction, meaning it cannot achieve dynamic calibration of antenna null drift based on changes in antenna frequency.

[0052] The root mean square error (RMSE) of angle measurements in monopulse radar can usually be approximated as:

[0053]

[0054] in, Indicates the antenna beamwidth. Indicates the signal-to-noise ratio. τ represents the servo noise bandwidth, and τ represents the correlation processing time. This represents the slope of a single pulse, i.e., the error slope factor;

[0055] A deeper, more stable zero depth directly corresponds to a larger, more linear single-pulse slope. Value. Therefore, in the formula, increasing and increase (By improving the zero depth) the angular error is reduced productively. Because monopulse tracking radar operates at multiple frequencies, the null depth of the antenna, once designed for a single frequency, cannot be adjusted. For monopulse tracking radar operating at multiple frequencies, improving tracking accuracy requires a sufficiently large null depth, assuming a sufficiently high signal-to-noise ratio, to push the tracking accuracy of the monopulse tracking radar towards its theoretical limit.

[0056] Therefore, after adjusting the length of the three mounting screws of the reflector, this application adjusts the different frequency points of the signal source and observes the center error Δazimuth(i) between the azimuth zero point and the optical axis mark line at the signal source through the antenna mount telescope at the receiving end;

[0057] At the same time, determine the center error Δelevation(i) between the pitch zero point and the optical axis marker line at the signal source;

[0058] Error values ​​are collected at multiple points within the data period. By recording these error values, the signal-to-noise ratio at different frequencies under the same conditions can be observed.

[0059] That is: based on the azimuth zero-point error value and elevation zero-point error value of each frequency point, determine the azimuth weighted compensation value and elevation weighted compensation value of each frequency point:

[0060] m n =(Error value - Mean error value at each frequency point) / Standard deviation of error value at each frequency point

[0061] Based on this, the azimuth zero-point offset compensation and elevation zero-point offset compensation for each frequency point are determined, an error correction model is constructed, and antenna null drift calibration is completed.

[0062]

[0063] In this embodiment, the collected error values ​​at different frequency points are F0:0.03, F1:0.03, F2:0.02, F3:0.04, F4:0.03, F5:0.05, F6:0.03, F7:0.02, F8:0.04, and F9:0.03, respectively. The mean value is 0.032. The weights are calculated for each value and substituted into the virtual zero-point formula. The zero depth and zero-point offset compensation amount are then calculated for each frequency point.

[0064] This step improves tracking accuracy by dynamically increasing the zero depth at different frequency points under the inherent signal-to-noise ratio, pushing the tracking accuracy towards the theoretical design value.

[0065] This solution also provides a single-beam precision measurement radar antenna zero-drift dynamic calibration system, including the following modules:

[0066] Mechanical calibration unit: used to set up test instruments for the transmitter and receiver of precision measurement radar, determine the optical axis mark line at the signal source; align the azimuth axis of the antenna mount telescope at the receiver with the optical axis mark line at the signal source; and perform mechanical error calibration of the antenna null position by adjusting the antenna mount at the receiver.

[0067] The error calibration module based on virtual zero coordinates is used to measure the radiated field strength of the antenna using a spectrum analyzer in step scan mode. By selecting data segments symmetrically distributed near the zero depth value, a virtual zero coordinate is constructed using a linear fitting algorithm. An error correction model is established based on the virtual zero coordinates. By determining the error values ​​at different operating frequencies, the zero offset compensation amount at each operating frequency is determined, thus completing the antenna zero drift calibration.

[0068] This solution also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to perform the following steps:

[0069] Step 1: Set up the test instruments at the transmitting end and the receiving end of the precision measurement radar, and determine the optical axis marker line at the signal source;

[0070] Step 2: Align the azimuth axis of the antenna mount telescope at the receiving end with the optical axis mark line at the signal source;

[0071] Step 3: Perform mechanical error calibration of the antenna null position by adjusting the antenna mount at the receiving end;

[0072] Step 4: Measure the radiated field strength of the antenna using a spectrum analyzer in a step scan. By selecting data segments symmetrically distributed near the zero depth, construct the virtual zero coordinates using a linear fitting algorithm.

[0073] Step 5: Establish an error correction model based on virtual zero coordinates. By determining the error values ​​at different operating frequencies, determine the zero offset compensation amount at each operating frequency to complete the antenna zero drift calibration.

[0074] This solution also provides a computer-readable storage medium on which a computer program is stored, wherein the computer program, when executed by a processor, performs the following steps:

[0075] Step 1: Set up the test instruments at the transmitting end and the receiving end of the precision measurement radar, and determine the optical axis marker line at the signal source;

[0076] Step 2: Align the azimuth axis of the antenna mount telescope at the receiving end with the optical axis mark line at the signal source;

[0077] Step 3: Perform mechanical error calibration of the antenna null position by adjusting the antenna mount at the receiving end;

[0078] Step 4: Measure the radiated field strength of the antenna using a spectrum analyzer in a step scan. By selecting data segments symmetrically distributed near the zero depth, construct the virtual zero coordinates using a linear fitting algorithm.

[0079] Step 5: Establish an error correction model based on virtual zero coordinates. By determining the error values ​​at different operating frequencies, determine the zero offset compensation amount at each operating frequency to complete the antenna zero drift calibration.

[0080] The embodiments described above are merely one implementation method of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for zero-point drift dynamic calibration of radar antenna based on single-beam precision measurement, characterized in that, Includes the following steps: Step 1: Set up the test instruments at the transmitting end and the receiving end of the precision measurement radar, and determine the optical axis marker line at the signal source; Step 2: Align the azimuth axis of the antenna mount telescope at the receiving end with the optical axis mark line at the signal source; Step 3: Perform mechanical error calibration of the antenna null position by adjusting the antenna mount at the receiving end; Step 4: Measure the radiated field strength of the antenna using a spectrum analyzer in a step scan. By selecting data segments symmetrically distributed near the zero depth, construct the virtual zero coordinates using a linear fitting algorithm. Step 5: Establish an error correction model based on virtual zero coordinates. By determining the error values ​​at different operating frequencies, determine the zero offset compensation amount at each operating frequency to complete the antenna zero drift calibration.

2. The method for zero-drift dynamic calibration of radar antenna based on single-beam precision measurement according to claim 1, characterized in that, The test instruments for the precision measurement radar transmitter include a microwave signal source, a microwave power amplifier, and a transmitting horn, which are connected in sequence.

3. The method for zero-drift dynamic calibration of radar antenna based on single-beam precision measurement according to claim 1, characterized in that, The test instruments for the receiver include a standard gain horn antenna, an antenna under test, a feed waveguide, an absorbing load, a four-way waveguide switch, and a spectrum analyzer. The standard gain horn antenna and the antenna under test are mounted on the antenna mount and connected by a feed waveguide and a four-way waveguide switch, respectively. The four-way waveguide switch is connected to the spectrum analyzer.

4. The method for zero-drift dynamic calibration of radar antenna based on single-beam precision measurement according to claim 1, characterized in that, The mechanical error calibration of the antenna null position in step 3 specifically involves: Step 3-1: Adjust the mounting screws between the receiving antenna mount and the antenna under test so that the azimuth zero depth value at the center frequency point of the antenna under test meets the requirements. When the azimuth zero point is cut, the center of the optical axis mark line at the signal source is at the azimuth zero value of the antenna mount telescope. Step 3-2: By adjusting the mounting screws between the receiving antenna mount and the antenna under test, the difference between the elevation axis of the antenna mount telescope and the optical axis mark line at the signal source is within the set range, while the elevation zero depth value is less than the set threshold. Step 3-3: Step-by-step check whether the azimuth null depth and elevation null depth values ​​of the entire frequency band meet the requirements; Step-by-step checks are performed to ensure that the difference between the azimuth zero point and the elevation zero point of the entire frequency band and the theoretical value of the antenna is within the set range.

5. The method for zero-drift dynamic calibration of radar antenna based on single-beam precision measurement according to claim 1, characterized in that, The construction of virtual zero-point coordinates in step 4 specifically involves: By fitting a linear model of the selected data segment using the least squares method, we obtain: y = kx + b, where y is the virtual antenna null point after fitting the frequency point calculated by the model, x is the antenna null point obtained by measurement, and b is the null point offset obtained by fitting.

6. The method for zero-drift dynamic calibration of radar antenna based on single-beam precision measurement according to claim 5, characterized in that, The determination of the zero-point offset compensation amount for each operating frequency point in step 5 is specifically as follows: Adjust different frequency points of the signal source, and observe the center error Δazimuth(i) between the azimuth zero point and the optical axis mark line at the signal source through the antenna mount telescope at the receiving end; At the same time, determine the center error Δelevation(i) between the pitch zero point and the optical axis marker line at the signal source; Based on the azimuth zero-point error values ​​and elevation zero-point error values ​​for each frequency point, determine the azimuth weighted compensation value and elevation weighted compensation value for each frequency point: m n =(Error value - Mean error value at each frequency point) / Standard deviation of error value at each frequency point Based on this, the azimuth zero-point offset compensation and elevation zero-point offset compensation for each frequency point are determined, an error correction model is constructed, and antenna null drift calibration is completed. 。 7. A single-beam precision measurement radar antenna zero-drift dynamic calibration system, characterized in that, Includes the following modules: Mechanical calibration unit: used to set up test instruments for the transmitter and receiver of precision measurement radar, and to determine the optical axis marker line at the signal source; Align the azimuth axis of the antenna mount telescope at the receiving end with the optical axis mark line at the signal source; Mechanical error calibration of the antenna null position is performed by adjusting the antenna mount at the receiving end. The error calibration module based on virtual zero coordinates is used to measure the radiated field strength of the antenna using a spectrum analyzer in step scan mode. By selecting data segments symmetrically distributed near the zero depth value, a virtual zero coordinate is constructed using a linear fitting algorithm. An error correction model is established based on the virtual zero coordinates. By determining the error values ​​at different operating frequencies, the zero offset compensation amount at each operating frequency is determined, thus completing the antenna zero drift calibration.

8. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1-6.

9. A computer-storable medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1-6.

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