Compact range dead zone amplitude and phase test method based on reference target method
By using the conductor rod reference target method and Fourier transform technology, the amplitude and phase testing of the static region in the compacted field is simplified, solving the problem of complexity and time consumption in existing methods, and realizing efficient and flexible static region performance testing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUOYU MICROWAVE TECH CO LTD
- Filing Date
- 2026-02-02
- Publication Date
- 2026-05-01
AI Technical Summary
Existing methods for calibrating and verifying the quiet zone in a compact field are complex, time-consuming, and costly, making it difficult to perform rapid periodic re-inspections. Furthermore, the scanning rig equipment interferes with the quiet zone environment, limiting the flexibility of the test.
Using a conductor rod as a reference target, radar cross-section data is acquired by rotation. By combining Fourier transform and time-domain gate filtering, the field distribution in the still region is inverted, simplifying the test setup and enabling high-precision measurement of the amplitude and phase performance in the still region.
It enables rapid and simple static zone amplitude and phase performance testing under normal conditions in a compressed field, reducing manpower and time costs and improving the flexibility and accuracy of testing.
Smart Images
Figure CN121955538A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microwave measurement technology, specifically relating to a method for measuring the amplitude and phase of a compressed field static region based on the reference target method. Background Technology
[0002] In a microwave anechoic chamber, the Compact Antenna Test Range (CATR) uses mirrors to convert spherical waves radiated from a point source into plane waves, thereby creating a wide quiet zone within a limited test distance. The performance of the quiet zone, including amplitude and phase uniformity, cross-polarization isolation, etc., is crucial for evaluating the performance of the compact antenna test range and ensuring the accuracy of antenna, radome, or radar cross section (RCS) measurements.
[0003] Currently, the industry commonly uses the scanning frame probe testing method for calibrating and verifying the quiet zone of a compressed field. This method requires building a large, precise two-dimensional scanning frame within the quiet zone and mounting a standard probe (such as a horn antenna) on it. The probe is then mechanically driven to move point by point across the quiet zone cross-section, precisely measuring the amplitude and phase at each location to create a field distribution map of the entire quiet zone. While this method provides detailed and highly accurate data, its setup process is extremely complex and time-consuming, making periodic re-inspection of the compressed field difficult. The size and metal structure of the scanning frame itself can easily interfere with the quiet zone environment, and its setup, alignment, and calibration processes require extremely high precision, resulting in a lengthy testing cycle and high labor and time costs. Furthermore, the bulky scanning frame equipment limits testing flexibility, making it difficult to quickly verify quiet zone performance during project breaks or after system maintenance. Summary of the Invention
[0004] In view of the above-mentioned defects or deficiencies in the prior art, the present invention provides a method for testing the amplitude and phase of the static zone in a compact field based on the reference target method. This testing method can support the detection of the static zone under the daily testing conditions of the compact field. The testing method uses the RCS of the reference target as a function of the azimuth angle, and inversely retrieves the static zone field distribution through data processing.
[0005] The implementation scheme of the present invention is as follows:
[0006] A method for testing the amplitude and phase of a compressed field static region based on the reference target method includes the following steps:
[0007] Step 1: Using the conductor rod as a reference target, install it horizontally or vertically with its center coinciding with the rotation center of the one-dimensional turntable in the compacted field and the rod perpendicular to the direction of the incoming wave.
[0008] Step 2: Establish the layout coordinate system and the target coordinate system with the center of rotation of the conductor rod as the origin, and record the change of the angle between the two coordinate systems as the rod rotates;
[0009] Step 3: Within the preset azimuth angle range, rotate the conductor rod step by step at set angle intervals, and synchronously collect frequency domain radar cross section (RCS) data at each angle to obtain target scattered electric field data.
[0010] Step 4: Perform inverse Fourier transform on the radar cross section (RCS) data, window it to obtain the time domain response, use the time domain gate function to extract the main lobe interval containing the target scattering center, and then transform it back to the frequency domain to obtain the clutter-suppressed target scattering field frequency domain data.
[0011] Step 5: Using the angle corresponding to the peak of the scattered field as the actual 0°, perform cyclic shifting on the entire set of data to complete the zero-angle correction, and interpolate the angle domain data according to the required spectral domain range to map the data from the angle domain to the spectral domain.
[0012] Step 6: Perform inverse Fourier transform on the spectral domain target scattering field data to invert the one-dimensional transverse incident field distribution of the compact field quiet region;
[0013] Step 7: Take the amplitude and phase of the incident field distribution, calculate the amplitude taper, amplitude ripple, phase taper and phase ripple, and complete the static zone amplitude and phase performance evaluation.
[0014] Preferably, the conductor rod is a metal rod with a length greater than the range of the quiet zone.
[0015] Preferably, a conductor rod is used as a reference target, and the one-dimensional lateral distribution of any target is characterized by rotating the conductor rod around its center.
[0016] Preferably, the test system required for the compact field static zone amplitude and phase testing method based on the reference target method includes a feed, a parabolic reflector, a reference target, a foam support turntable, a vector network analyzer, and a control computer. The feed is connected to the vector network analyzer via a compact field radio frequency link. The control computer controls the vector network analyzer and the foam support turntable for testing. When placing the reference target on the foam support turntable, its center is placed at the rotation center of the foam support turntable, and its direction is perpendicular to the direction of the incoming wave. After placement, the test parameters are set on the control computer, including the test frequency range. Frequency interval Angle range Angular interval .
[0017] Preferably, step 4 includes:
[0018] Obtain the radar cross section (RCS) data of the reference target in the azimuth direction. , These are the turntable angle and the test frequency, respectively.
[0019] By filtering out stray signals from the radar cross section (RCS) data in the target direction using the time-domain gate method, the time-domain data of the target's scattered field is obtained. ;
[0020] The time-domain gate method is executed as follows: the frequency domain data of the target scattered field is transformed to the time domain through inverse Fourier transform:
[0021] ;
[0022] in Apply a window function to the frequency domain;
[0023] Define the time-domain gate function G(t) as follows:
[0024] ;
[0025] By applying a time-domain gate function to the total time-domain response, the time-domain components of the target scattering data are extracted:
[0026] ;
[0027] Performing a Fourier transform on the time-domain data component of the target scattered field yields the frequency-domain data of the target scattered field after stray filtering. :
[0028] .
[0029] Preferably, step 5 includes:
[0030] Based on the target scattering field frequency domain data The peak value is determined to be at the actual 0° position. A cyclic shift is used to move the peak value back to 0°. The target scattering field data after angle adjustment is as follows: ;
[0031] Based on the relationship between the angular domain and the spectral domain For the spectral domain The target scattering field data is transformed from the angular domain to the spectral domain through interpolation. This refers to the amplitude and phase characteristic data of the static zone.
[0032] Preferably, step 6 includes: basing it on the relationship between the target scattered field and the incident field forming a surface current on the target surface, as shown in the following formula:
[0033] ;
[0034] In the formula, For the scattered electric field, The distribution of scattering points on the rod is one-dimensional. The incident field on the target surface is a one-dimensional transverse distribution, where In the antenna direction spatial coordinate system Axis position, For the spectral domain , Let k be the rotation angle of the turntable, and k be the propagation vector.
[0035] The one-dimensional lateral distribution of the scattering points of the reference target conductor rod is as follows:
[0036] ;
[0037] Based on the above formula relating the target scattered field and the surface current formed on the target surface by the incident field, the target incident field can be obtained. .
[0038] Preferred:
[0039] The static phase distribution and amplitude distribution can be obtained from the target incident field. for:
[0040] ;
[0041] Phase distribution for:
[0042] ;
[0043] Here, abs() is used to take the absolute value, imag() is used to take the imaginary part of the complex number, and real() is used to take the real part of the complex number.
[0044] Preferably, the conductor rod is a rectangular metal plate.
[0045] Preferably, the test angle range is (-25°, 25°), the test angle interval is 0.1°, and the sampling points are a sequence from -0.6m to 0.6m with an interval of 0.02m.
[0046] Compared with the prior art, the present invention has the following advantages:
[0047] Firstly, this invention uses a conductor rod as a reference target to obtain its azimuth radar cross section (RCS) distribution, obtains the static zone amplitude and phase distribution through algorithm inversion, and suppresses clutter signals outside the static zone through time-domain gates, thereby achieving high-precision measurement of amplitude and phase characteristics within the static zone.
[0048] Secondly, compared with the traditional method of using a scanning frame for probe scanning, the test device is easier to set up and the measurement method is simpler. It can be used to detect the static amplitude distribution during daily use in a compact field. Attached Figure Description
[0049] Figure 1 For reference, the target coordinate system and the rotating coordinate system of the turntable;
[0050] Figure 2The connection block diagram of the static zone amplitude and phase test system for reference method is shown below;
[0051] Figure 3 This describes the execution process of the compact field static zone amplitude phase test processing procedure based on the reference target method.
[0052] Figure 4 This is a schematic diagram of the time-domain gate filtering process;
[0053] Figure 5 The target scattering field data after processing with the 10GHz time-domain gate filtering method;
[0054] Figure 6 The amplitude and phase processing results are for the 8GHz quiet zone.
[0055] Figure 7 The result is the amplitude and phase processing result for the 10GHz quiet zone. Detailed Implementation
[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.
[0057] This invention provides a method for testing the amplitude and phase characteristics of a compressed field static region based on the reference target method. The static region to be tested is the original static region formed by a compressed field system consisting of a reflector, a feed, and a feed support. In this method, a conductor rod of length L is selected as the reference target. When testing the horizontal amplitude and phase characteristics of the compressed field static region, the rod can be placed on a foam support or a low-scattering metal support structure of a one-dimensional turntable within the compressed field, with the center of the conductor rod coinciding with the rotation center of the turntable for rotation testing. When testing the vertical amplitude and phase characteristics of the compressed field static region using the reference target method, a customized vertical rotating base can be used to achieve rotation testing of the reference target in a vertical state.
[0058] A spatial coordinate system is established based on the positions of the conductor rod and the center of rotation. The length of the conductor rod is L, and the origin is the center of rotation of the conductor rod, pointing in the direction of the antenna. The axis is perpendicular to the right. Establish layout coordinate system Taking the center of rotation of the conductor rod as the origin, and perpendicular to the rod as... The axis, along the direction of the rod, is Establish the target coordinate system using axes. As the conductor rod rotates, the angle between the two coordinates... Changes have occurred. A schematic diagram of the coordinate system establishment is shown below. Figure 1 As shown.
[0059] The radar cross section (RCS) value of the conductor rod within the preset azimuth angle range is obtained as the target scattered electric field data, which is the data to be processed by the algorithm.
[0060] During the test data processing, clutter in the target scattered electric field data is filtered out using the time-domain gating method. The target scattered electric field data undergoes angle zero-point adjustment and angle range truncation.
[0061] Interpolation can be used to transform the target scattering field data from the angular domain to the spectral domain.
[0062] Based on the principle formula, a Fourier transform is performed, and the one-dimensional lateral distribution of the target incident field can be obtained after the transform.
[0063] The block diagram for the test system setup required for the compact field static region amplitude phase test method based on the reference target method is shown below. Figure 2 The system includes a feed source 1, a parabolic reflector 2, a reference target 3, a foam support turntable 4, a vector network analyzer 5, a control computer 6, and a compacted field 7. The feed source 1, parabolic reflector 2, and foam support turntable 4 are positioned in their normal operating state within the compacted field 7 and require no adjustment. The feed source 1 is connected to the vector network analyzer 5 via an existing RF link within the compacted field. The control computer 6 controls the vector network analyzer 5 and the foam support turntable 4 for testing.
[0064] When placing the reference target 3 onto the foam support turntable 4, its center should be placed at the rotation center of the foam support turntable 4, and its direction should be perpendicular to the direction of the incoming wave. After placement, set the test parameters, including the test frequency range, on the control computer 6. Frequency interval Angle range Angular interval Once everything is ready, the test can begin. The post-test data processing flow is as follows: Figure 3 As shown:
[0065] After the test, the radar cross section (RCS) data of the reference target in the azimuth direction was obtained. , The turntable angle and test frequency were measured separately.
[0066] By filtering out stray signals from the radar cross section (RCS) data in the target direction using the time-domain gate method, the time-domain data of the target's scattered field is obtained. .
[0067] The time-domain gate method is executed as follows: the frequency domain data of the target scattered field is transformed to the time domain through inverse Fourier transform:
[0068] ;
[0069] in, Apply a window function to the frequency domain; window functions such as Hamming windows and Kaiser windows can be used to suppress time-domain sidelobes.
[0070] The next step is to determine the time domain interval corresponding to the target scattering center. This can be determined using the time domain image at the 0° position. The 0° reference target has the strongest reflected signal, and a high peak will appear at the target scattering center position. The center time delay corresponds to the echo time.
[0071] ;
[0072] See attached Figure 4 (a), where c is the speed of light and D is the distance between the target scattering center and the signal source.
[0073] The time-domain gate width can be determined by the target length and rotation angle. Should be greater than ;
[0074] Define the time-domain gate function G(t) as follows:
[0075] ;
[0076] By applying a time-domain gate function to the total time-domain response, the time-domain components of the target scattering data are extracted:
[0077] ;
[0078] Performing a Fourier transform on the time-domain data component of the target scattered field yields the frequency-domain data of the target scattered field after stray filtering. :
[0079] ;
[0080] The reference target-based test method for static amplitude and phase measurement has high requirements for angle intervals. In high frequencies such as the Ka band, the angle interval often needs to be 0.01°. It is difficult to ensure that the reference target is at 0° on the one-dimensional turntable when it is perpendicular to the direction of the incoming wave when it is manually placed. Therefore, it is necessary to adjust the zero position of the reference target and cut off the angle range.
[0081] Based on the target scattering field frequency domain data The peak value can be used to determine the actual position at 0°. A cyclic shift is used to move the peak value to 0°, and the target scattering field data after angle adjustment is as follows: .
[0082] Based on the relationship between the angular domain and the spectral domain For the spectral domain The target scattering field data is transformed from the angular domain to the spectral domain through interpolation. , This is the propagation vector.
[0083] The target scattering field refers to the target scattering electric field data obtained from the test. The incident field is the electric field data that is directly irradiated onto the reference target by the reflecting surface, which is the static phase characteristic data.
[0084] This test method is based on the relationship between the target scattered field and the surface current formed on the target surface by the incident field, as shown in the following formula:
[0085] ;
[0086] In the formula, For scattered electric field data, The one-dimensional distribution of scattering points on the conductor rod. The incident field on the target surface is a one-dimensional transverse distribution, where In the antenna direction spatial coordinate system Axis position, For the spectral domain , The rotation angle of the turntable. This is the propagation vector.
[0087] In this invention, the reference target conductor rod is generally selected as a square metal conductor rod, and the one-dimensional lateral distribution of the scattering points is as follows:
[0088] ;
[0089] Based on the above formula relating the target scattered field and the surface current formed on the target surface by the incident field, the target incident field can be obtained. .
[0090] The static phase distribution and amplitude distribution can be obtained from the target incident field. for:
[0091] ;
[0092] Phase distribution for:
[0093] ;
[0094] Among them, abs() is for taking the absolute value, imag() is for taking the imaginary part of the complex number, and real() is for taking the real part of the complex number.
[0095] The following is an example of obtaining the amplitude and phase distribution of the quiet zone in a 1.2m quiet zone at the test frequencies of 8GHz and 10GHz using a compact field quiet zone amplitude and phase testing algorithm based on the reference target method:
[0096] Step 1: Connect to the test system and confirm that the test link is fault-free.
[0097] Step 2: Select a metal plate with dimensions of 1500mm (length) × 100mm (width) × 10mm (thickness) as the reference target, place it on the foam support, and adjust the plate to ensure that its center is located at the rotation center of the foam support and its direction is perpendicular to the direction of the incoming wave.
[0098] Step 3: According to the test requirements, the quiet zone to be tested is 1.2m, the frequency points to be tested are 8GHz and 10GHz, and the expected sampling step size is 0.02m. Therefore, it can be calculated that the required test angle range is (-25°, 25°) and the test angle interval is 0.1°; the sampling points are a sequence from -0.6m to 0.6m with an interval of 0.02m.
[0099] Step 4: Input the test parameters into the test computer and start the test process.
[0100] Step 5: After the test process is completed, obtain the azimuth RCS data of the metal plate.
[0101] Step 6: Call the static zone amplitude and phase characteristic processing program based on the reference target method to obtain the one-dimensional distribution of the target incident direction.
[0102] Step 7: Perform amplitude and phase calculations on the one-dimensional incident distribution of the target to obtain the amplitude and phase distribution of the static region.
[0103] Figure 4 A schematic diagram of adding time-domain gating to the reference target time-domain test results, where... Figure 4 (a) shows the time-domain test results of the reference target before adding the time-domain gate, where the dashed line represents the time-domain gate region; Figure 4 (b) is the time-domain test result of the reference target after adding the time-domain gate.
[0104] Figure 5 The above image shows the target scattering field data after processing with a 10GHz time-domain gate filter. The image below shows the amplitude data, and the angle needs to be adjusted according to the position of the amplitude peak.
[0105] Figure 6 The results of the 8GHz quiet zone amplitude and phase tests are shown in the top figure, which shows the amplitude inversion results and the phase inversion results, respectively. The quiet zone amplitude and phase tests were conducted using the reference target method. The amplitude taper was 0.9dB, the amplitude ripple was ±0.3dB, the phase taper was 9.2°, and the phase ripple was ±2.1°.
[0106] Figure 7 The results of the 10GHz quiet zone amplitude and phase tests are shown in the top figure, which shows the amplitude inversion results, and the bottom figure shows the phase inversion results. The quiet zone amplitude and phase tests were conducted using the reference target method. The amplitude taper was 1.0dB, the amplitude ripple was ±0.3dB, the phase taper was 11°, and the phase ripple was ±2.8°.
Claims
1. A method for testing the amplitude and phase of a compressed field static region based on the reference target method, characterized in that, Includes the following steps: Step 1: Using the conductor rod as a reference target, install it horizontally or vertically with its center coinciding with the rotation center of the one-dimensional turntable in the compacted field and the rod perpendicular to the direction of the incoming wave. Step 2: Establish the layout coordinate system and the target coordinate system with the center of rotation of the conductor rod as the origin, and record the change of the angle between the two coordinate systems as the rod rotates; Step 3: Within the preset azimuth angle range, rotate the conductor rod step by step at set angle intervals, and synchronously collect frequency domain radar cross section (RCS) data at each angle to obtain target scattered electric field data. Step 4: Perform inverse Fourier transform on the radar cross section (RCS) data, window it to obtain the time domain response, use the time domain gate function to extract the main lobe interval containing the target scattering center, and then transform it back to the frequency domain to obtain the clutter-suppressed target scattering field frequency domain data. Step 5: Using the angle corresponding to the peak of the scattered field as the actual 0°, perform cyclic shifting on the entire set of data to complete the zero-angle correction, and interpolate the angle domain data according to the required spectral domain range to map the data from the angle domain to the spectral domain. Step 6: Perform inverse Fourier transform on the spectral domain target scattering field data to invert the one-dimensional transverse incident field distribution of the compact field quiet region; Step 7: Take the amplitude and phase of the incident field distribution, calculate the amplitude taper, amplitude ripple, phase taper and phase ripple, and complete the static zone amplitude and phase performance evaluation.
2. The method according to claim 1, characterized in that, The conductor rod is a metal rod whose length is greater than the range of the quiet zone.
3. The method according to claim 1, characterized in that, The reference target support equipment includes, but is not limited to, foam supports and low-scattering metal supports.
4. The method according to claim 1, characterized in that, Using a conductor rod as a reference target, the one-dimensional lateral distribution of any target can be characterized by rotating the conductor rod around its center.
5. The method according to claim 1, characterized in that, Using a conductor rod as a reference target, its rotation direction includes, but is not limited to, horizontal rotation and vertical rotation.
6. The method according to claim 1, characterized in that, The test system required for the compact field still zone amplitude and phase testing method based on the reference target method includes a feed, a parabolic reflector, a reference target, a foam support turntable, a vector network analyzer, and a control computer. The feed is connected to the vector network analyzer via a compact field radio frequency link. The control computer controls the vector network analyzer and the foam support turntable for testing. When placing the reference target on the foam support turntable, its center is positioned at the rotation center of the foam support turntable, with its direction perpendicular to the direction of the incoming wave. After placement, test parameters are set on the control computer, including the test frequency range. Frequency interval Angle range Angular interval .
7. The method according to claim 1, characterized in that, Step 4 includes: Obtain the radar cross section (RCS) data of the reference target in the azimuth direction. , , These are the turntable angle and the test frequency, respectively. By filtering out stray signals from the radar cross section (RCS) data in the target direction using the time-domain gate method, the time-domain data of the target's scattered field is obtained. ; The time-domain gate method is executed as follows: the frequency domain data of the target scattered field is transformed to the time domain through inverse Fourier transform: ； in, Apply a window function to the frequency domain; Define the time-domain gate function G(t) as follows: ； By applying a time-domain gate function to the total time-domain response, the time-domain components of the target scattering data are extracted: ； Performing a Fourier transform on the time-domain data component of the target scattered field yields the frequency-domain data of the target scattered field after stray filtering. : 。 8. The method according to claim 5, characterized in that, Step 5 includes: Based on the target scattering field frequency domain data The peak value is determined to be at the actual 0° position. A cyclic shift is used to move the peak value back to 0°. The target scattering field data after angle adjustment is as follows: ; Based on the relationship between the angular domain and the spectral domain For the spectral domain The target scattering field data is transformed from the angular domain to the spectral domain through interpolation. This refers to the amplitude and phase characteristic data of the static zone.
9. The method according to claim 6, characterized in that, Step 6 includes: based on the relationship between the target scattered field and the incident field forming a surface current on the target surface, as shown in the following formula: ； In the formula, For the scattered electric field, The distribution of scattering points on the rod is one-dimensional. The incident field on the target surface is a one-dimensional transverse distribution, where In the antenna direction spatial coordinate system Axis position, For the spectral domain , Let k be the rotation angle of the turntable, and k be the propagation vector. The one-dimensional lateral distribution of the scattering points of the reference target conductor rod is as follows: ； Based on the above formula relating the target scattered field and the surface current formed on the target surface by the incident field, the target incident field can be obtained. .
10. The method according to claim 7, characterized in that, The static phase distribution and amplitude distribution can be obtained from the target incident field. for: ； Phase distribution for: ； Among them, abs() is for taking the absolute value, imag() is for taking the imaginary part of the complex number, and real() is for taking the real part of the complex number.
11. The method according to claim 2, characterized in that, The conductor rod is a rectangular metal plate.
12. The method according to claim 4, characterized in that, The test angle range is (-25°, 25°), the test angle interval is 0.1°, and the sampling points are a sequence from -0.6m to 0.6m with an interval of 0.02m.