Imaging diagnosis system and method for spurious signals in compact range darkroom

Abstract

The invention discloses a system and a method for imaging and diagnosing spurious signals in a compact range darkroom, and belongs to the technical field of microwave measurement. The system comprises a scanning frame, a transceiving feed source antenna, a parabolic reflecting surface, a feed source bracket, a vector network analyzer, a control computer and a compact range darkroom. The scanning frame is erected in front of the feed source support, and the transceiving feed source antenna is installed on the scanning frame and collects test data through scanning in the horizontal or vertical direction. The control computer controls scanning parameters of the scanning frame and triggering of the vector network analyzer, and stores and processes data. And performing imaging processing on test data through a projection algorithm to generate field imaging results of a horizontal section and a vertical section, analyzing distribution of strong scattering points in combination with darkroom layout, and quickly positioning a source of spurious signals. According to the invention, full-field imaging of the compact range darkroom is realized, the efficiency and accuracy of spurious signal diagnosis are remarkably improved, and the method is suitable for spurious source positioning of various compact range test systems.

Description

Technical Field

[0001] This invention belongs to the field of microwave measurement technology, specifically relating to a stray signal imaging diagnostic system and method in a compact dark room. Background Technology

[0002] The Compact Antenna Test Range (CATR) is an important facility in the field of microwave measurement. It simulates far-field plane wave conditions within a confined space using a parabolic reflector and is widely used for antenna performance testing and radar cross section (RCS) measurement. With the development of wireless communication and stealth technologies, the requirements for the accuracy and dynamic range of CATR measurements are increasingly stringent. Background noise and spurious signals are key factors affecting CATR performance; they degrade the field uniformity of the quiet zone, thereby reducing the reliability of the test results.

[0003] Traditional spurious signal detection methods primarily rely on standard gain horn antennas to measure the field distribution point-by-point within a quiet zone. However, this method can only assess the quality of the quiet zone and cannot directly pinpoint the spatial location of the spurious source. Due to the complex structure of a compact anechoic chamber, including parabolic reflectors, feed systems, and support structures, potential spurious signals may originate from diffraction at the reflector edges, scattering from the support structure, or reflections from the chamber walls. Traditional investigation methods are inefficient and struggle to accurately identify the specific location of the spurious source.

[0004] Currently, there is a lack of efficient and intuitive stray signal localization technology during the commissioning and maintenance of compact anechoic chambers. Existing methods typically require repeated equipment adjustments or rely on experience-based judgment, which is time-consuming and labor-intensive. Therefore, there is an urgent need for a technology that can rapidly image the entire compact anechoic chamber, visually presenting the distribution of stray signals, thereby providing a scientific basis for the accurate localization and elimination of stray sources. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a stray signal imaging diagnostic system and method for a compact anechoic chamber, which can perform full-field imaging of the compact anechoic chamber and directly locate the stray source.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A stray signal imaging diagnostic system for a compact, dark room, the system comprising:

[0008] A scanning frame is mounted in front of a feed source bracket, wherein a first feed source is installed on the feed source bracket.

[0009] A transceiver feed, mounted on the scanning frame, is used to scan and acquire test data in a horizontal or vertical direction, with the beam of the transceiver feed facing the parabolic reflector.

[0010] The parabolic reflector and the feed support jointly constitute a compact range system.

[0011] A vector network analyzer is connected with the transceiving feed, and provides radio frequency signals and receives test data.

[0012] A control computer is used for controlling the scanning parameters of the scanning frame and the triggering of the vector network analyzer, and based on the test data obtained by scanning, the horizontal and vertical cross-section imaging results of the site are generated by a projection algorithm to locate the source of the stray signal.

[0013] In another aspect, the application also provides a stray signal imaging diagnosis method in a compact range anechoic chamber, which is applied to the system described above, and comprises the following steps:

[0014] The scanning frame is erected in front of the feed support, and the position of the scanning frame is calibrated.

[0015] The compact range system is configured, and the scanning frame, the transceiving feed, the vector network analyzer and the control computer are connected.

[0016] The control computer controls the rotating shaft of the scanning frame to be horizontal, sets the test frequency band, the scanning frame stroke range, the step interval and the transmission power of the vector network analyzer, and starts the test.

[0017] The control computer controls the rotating shaft of the scanning frame to be vertical, sets the test frequency band, the scanning frame stroke range, the step interval and the transmission power of the vector network analyzer again, and performs the test.

[0018] The control computer processes the test data to perform imaging processing.

[0019] The imaging results are analyzed, and the position of the stray signal is determined according to the distribution of the strong scattering points in the imaging.

[0020] The application has the following beneficial effects:

[0021] Full-field fast imaging: the application drives the transceiving feed to perform horizontal and vertical direction scanning through the scanning frame, and combines the projection algorithm to process data, so that the horizontal cross-section and vertical cross-section imaging of the compact range anechoic chamber can be generated at one time, the visualization positioning of the full-field stray signal is realized, and the diagnosis efficiency is greatly improved.

[0022] Precise positioning of the stray source: the traditional method can only indirectly speculate the position of the stray signal through one-dimensional field distribution, while the application directly presents the distribution of the strong scattering points through two-dimensional imaging, and combined with the layout analysis of the anechoic chamber, the source of the stray signal (such as the edge of the reflector, the feed support or the support structure, etc.) can be accurately determined, and the positioning accuracy is significantly improved.

[0023] High efficiency test procedure: short scanning frame (usually within 1 meter), flexible scanning interval (such as 10 mm), combined with the fast trigger and data acquisition of the vector network analyzer, the full field imaging can be completed in a single test, which saves a lot of time compared with point-by-point measurement.

[0024] Strong compatibility: the system supports various parabolic reflectors (such as single-rotating parabolic surface, cylindrical parabolic surface) and linearly polarized feed (single / dual polarization), and covers the full working range of the compact range, which is suitable for compact range darkrooms of different scales and configurations.

[0025] Low cost and easy implementation: reuse the original RF system (such as feed and vector network analyzer) of the compact range, only need to add scanning frame and imaging algorithm, without complex modification or additional expensive equipment, which is convenient for popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A system block diagram for stray signal imaging diagnosis in a compact range darkroom is provided;

[0027] Figure 2 A schematic diagram for horizontal scanning is provided;

[0028] Figure 3 A schematic diagram for vertical scanning is provided;

[0029] Figure 4 A horizontal section 8-12 GHz field imaging result is provided;

[0030] Figure 5 A vertical section 8-12 GHz field imaging result is provided.

[0031] REFERENCE NUMERALS:

[0032] 1 is a scanning frame, 2 is a transceiving feed, 3 is a parabolic reflector, 4 is a feed support, 5 is a vector network analyzer, 6 is a control computer, and 7 is a compact range darkroom. DETAILED DESCRIPTION

[0033] The present application will be further described below in combination with the drawings and examples.

[0034] Due to the large number of devices in a compact anechoic chamber, even with low-scattering processing, each device may still introduce stray signals into the site, degrading the background level. Furthermore, locating stray sources in a large compact anechoic chamber is time-consuming, and conventional testing methods struggle to accurately and quickly pinpoint them. To address these limitations, this invention proposes a compact anechoic chamber stray signal imaging diagnostic system and method. By mounting a transceiver feed on a scanning rig for scanning within the compact anechoic chamber, imaging is performed. The scanned data is then processed to reveal the distribution of stray signals in the site. Combining the imaging results with the site layout, stray sources can be located. In the corresponding test frequency band, only one horizontal and one vertical scan are needed to image the entire site in both horizontal and vertical sections. The short scanning time significantly improves the efficiency of stray source localization.

[0035] like Figure 1 The diagram shows a block diagram of a stray signal imaging diagnostic system in a compact field darkroom according to the present invention. The system is located in a compact field darkroom 7, and the space inside the compact field darkroom 7 is the diagnostic object of the field imaging diagnostic system. The system includes a scanning frame 1, a transceiver feed 2, a parabolic reflector 3, a feed support 4, a vector network analyzer 5, and a control computer 6.

[0036] Before site imaging diagnosis, the transceiver feed 2 needs to be mounted on the scanning frame 1 to perform horizontal imaging of the site (e.g., ...). Figure 2 As shown), vertical direction (such as) Figure 3 The scan is shown in the figure, with a scan height of H. The original transceiver feed on the feed bracket 4 inside the compact anechoic chamber 7 is referred to here as the first feed, serving as a reference feed. This first feed is used to implement the original test functions within the compact field and is unrelated to the site diagnostic system. When the transceiver feed 2 is located at the center of the scan frame 1's travel, its phase center should be at the same height as the phase center of the first feed mounted on the feed bracket 4. The transceiver feed 2 should be as close as possible to the first feed on the feed bracket 4. In the original RF system within the compact anechoic chamber 7, the corresponding frequency band RF line is connected to the first feed. The RF line connected to the first feed is led out from the first feed mounted on the feed bracket 4 and connected to the transceiver feed 2. The tilt angle of the transceiver feed 2 is similar to (e.g., angle difference < 5°) or the same as the tilt angle of the first feed on the feed bracket 4. The beam of the transceiver feed 2 faces the parabolic reflector 3. The parabolic reflector 3 and the feed bracket 4 together form the compact field system. The scanning frame 1 is equipped with a transceiver feed 2, which shares a radio frequency link with the first feed on the feed support 4 and is connected to the vector network analyzer 5; the control computer controls the scanning frame 1 and the vector network analyzer 5 to perform tests.

[0037] During the test, the control computer 6 controls the scanning frame 1 to scan the site, and the vector network analyzer 5 provides the transceiving feed source 2 with a radio frequency signal; the transceiving feed source 2 includes two feed sources, one of which acts as a transmitting end and the other of which acts as a receiving end. The scanning frame 1 is set to have a stroke of [-d, d] and a scanning interval of Δd. The frequency interval and the scanning interval can be set according to the site size and the imaging frequency band, the frequency interval is calculated according to the formula L = C / 2Δf, C is the speed of light, and L is the site imaging length, and the scanning interval Δd should be less than 1 / 2 wavelength.

[0038] The control computer 6 controls the scanning frame 1 to scan, and controls the vector network analyzer 5 to trigger the test and store the test data in real time. After the scanning is completed, the control computer 6 calls the imaging algorithm to process the test data to generate the site imaging of the corresponding section in the scanning direction, and judges the source of the stray signal according to the imaging result and in combination with the site layout.

[0039] A spatial coordinate system is established in the space of the compact range darkroom, the first feed source coordinate of the feed source support 4 is (0, 0, F), and the transceiving feed source 2 coordinate of the scanning frame 1 is A (Ax, Ay, F-Δz); the scanning frame 1 is horizontally scanned in the state of Ax = 0, and the scanning frame 1 is vertically scanned in the state of Ay = 0; the spatial pixel coordinate is P (x, y, z).

[0040] The site imaging diagnosis needs to process the test data for imaging, inverse Fourier transform is performed on the collected frequency domain test data S (f, Ax, Ay) to obtain the corresponding time domain signal S (t, Ax, Ay). For each spatial pixel point P (x, y, z) and each transceiving feed source 2 coordinate position A (Ax, Ay, F-Δz), the theoretical double-pass propagation time delay τ of electromagnetic waves propagating from the transceiving feed source 2 to the P point and then reflecting back to the transceiving feed source 2 is accurately calculated. According to the time delay τ, the signal value S (τ, Ax, Ay) at the corresponding time is extracted from the time domain signal S (t, Ax, Ay), and the value is added to the image intensity of the pixel P. The accumulation projection is completed by traversing all the pixel points and all the measurement positions, and finally the reconstructed image reflecting the spatial distribution of the scattering intensity of the target region is generated.

[0041] Wherein:

[0042] Time delay information: ;

[0043] Distance: R (A, P) = || vec (A) - vec (P) ||, which represents the complete distance of the signal from the transceiving feed source 2 to the spatial pixel, and vec represents the vector coordinates of the A point and the P point.

[0044] Since the transceiving feed source 2 performs omnidirectional scanning, it will generate multiple position coordinates, and thus the final imaging value of the point P is generated by the coherent superposition of the positions A of all the transceiving feed sources 2. After the coherent superposition, the real scattering signal from the point P is enhanced, and the interference signals from other points are suppressed due to inconsistent phases.

[0045] After the imaging processing, the imaging in the compact field darkroom can be obtained. The strong scattering points in the imaging are caused by the stray signals in the compact field, and can reflect the stray distribution in the compact field. The position of the quiet zone can be determined by placing a calibration ball on the support structure in the compact field darkroom.

[0046] The parabolic reflecting surface 3 includes, but is not limited to, a single rotating paraboloid, a cylindrical paraboloid and various parabolic reflecting surfaces. The measurement can cover the entire microwave frequency band in the compact field test system.

[0047] The antenna of the transceiving feed source 2 adopts a linear polarization feed source antenna, including single polarization and dual polarization.

[0048] The scanning frame 1 can be replaced by a mechanical arm feed source support or a device with a translation axis function to achieve the same function.

[0049] In another aspect, the application also provides a stray signal imaging diagnosis method in a compact field darkroom, which is applied to the diagnosis system described above and includes the following steps:

[0050] Erect the scanning frame 1 in front of the feed source support 4, and calibrate the position of the scanning frame 1.

[0051] Complete the configuration of the compact field system, and connect the scanning frame 1, the transceiving feed source 2, the vector network analyzer 5 and the control computer 6.

[0052] Control the control computer 6 to rotate the axis of the scanning frame 1 to the horizontal state.

[0053] Set the test frequency band, the travel range of the scanning frame 1, the step interval and the transmission power of the vector network analyzer 5 by the control computer 6, and start the test.

[0054] Control the control computer 6 to rotate the axis of the scanning frame 1 to the vertical state. Set the test frequency band, the travel range of the scanning frame 1, the step interval and the transmission power of the vector network analyzer 5 again, and perform the test.

[0055] Process the test data by the control computer 6 to perform imaging.

[0056] Analyze the imaging results, and determine the stray position according to the distribution of the strong scattering points in the imaging.

[0057] Embodiment:

[0058] A diagnosis case of imaging in a compact range chamber is selected as a preferred embodiment below, the antenna operating frequency is 8-12GHz, the chamber size is 45m 65m, the scanning range is [-0.5m, 0.5m], and the scanning interval is 10mm. The scanning parameters can be set by a control computer.

[0059] During the test, the scanning frame is controlled to move by a control computer program, and the test is triggered by a vector network analyzer. The test data are stored in the control computer.

[0060] After the test, the control computer processes the test data. The test data are stored in the control computer, and the control computer calls an imaging algorithm to perform imaging. The imaging result is shown in Figures 4-5 .

[0061] Figure 4 The imaging result of the horizontal section at 8-12GHz is shown in the figure. The black frame part is a quiet zone. According to the analysis of the imaging of the chamber layout, the image below is a reflecting surface; there is a strong stray signal near the coordinate (0m, 18m), which is preliminarily inferred to be caused by the feed support; the stray signal is strong near the center of the quiet zone, which is preliminarily inferred to be caused by the foam support turntable; according to the chamber layout, the longitudinal coordinate 12m is the back wall of the chamber. Figure 5 The imaging result of the vertical section at 8-12GHz is shown in the figure. The black frame part is a quiet zone. According to the analysis of the image, the longitudinal distance-40m is a reflecting surface; the longitudinal distance-18m is a feed support; near the center of the quiet zone, the shape of the stray signal distribution is similar to that of the foam support, which can be judged to be caused by the foam support; the longitudinal 12m is the back wall of the chamber.

[0062] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above-described specific embodiments are only for the specific embodiments of the present application and are not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A tight-field darkroom stray signal imaging diagnostic system, characterized by, The system comprises: a scanning frame (1) erected in front of a feed support (4) on which a first feed is mounted; a transceiving feed (2) mounted on the scanning frame (1) for scanning and collecting test data in horizontal or vertical directions, the beam of the transceiving feed (2) being directed towards a parabolic reflector (3); the parabolic reflector (3) and the feed support (4) together forming a compact range system; a vector network analyzer (5) connected to the transceiving feed (2) for providing radio frequency signals and receiving test data; a control computer (6) for controlling the scanning parameters of the scanning frame (1) and the triggering of the vector network analyzer (5), and for generating horizontal and vertical cross-sectional site imaging results based on the test data obtained by scanning, so as to locate the source of the stray signal.

2. The tight-field darkroom internal stray signal imaging diagnostic system of claim 1, wherein, The system further comprises a compact range darkroom (7) for providing a darkroom environment for the diagnostic system.

3. The tight-field darkroom internal stray signal imaging diagnostic system of claim 1, wherein, When the transceiving feed (2) is located at the center of the travel of the scanning frame (1), the phase center of the transceiving feed (2) is at the same height as the phase center of the first feed mounted on the feed support (4).

4. The tight-field darkroom internal stray signal imaging diagnostic system of claim 3, wherein, The tilt angle of the transceiving feed (2) is the same as the tilt angle of the first feed or has an angle difference within a preset range.

5. The tight-field darkroom internal stray signal imaging diagnostic system of claim 4, wherein, The preset range is that the angle difference is less than 5°.

6. The tight-field darkroom internal stray signal imaging diagnostic system of claim 1, wherein, The transceiving feed (2) and the first feed share the same radio frequency line and the same set of radio frequency links connected to the vector network analyzer (5).

7. The tight-field darkroom internal stray signal imaging diagnostic system of claim 1, wherein, The control computer (6) controls the travel of the scanning frame (1) to be [-d, d] and the scanning interval to be Δd; the frequency interval and the scanning interval of the scanning frame (1) are set according to the size of the site and the imaging frequency band, the frequency interval is calculated according to the formula L=C / 2Δf, C is the speed of light, and L is the site imaging length, and the scanning interval Δd is less than 1 / 2 wavelength.

8. The tight-field darkroom internal stray signal imaging diagnostic system of claim 1, wherein, The generation of the horizontal and vertical cross-sectional site imaging results by the projection algorithm comprises: performing inverse Fourier transform on the collected test data to convert the frequency domain data into time domain, and using time delay information to reversely project the time domain signal to a spatial pixel.

9. The tight-field darkroom internal stray signal imaging diagnostic system of claim 8, wherein, Performing inverse Fourier transform on the collected frequency domain test data to obtain corresponding time domain signals, for each spatial pixel point and each coordinate position of the transceiving feed (2), calculating the theoretical double-pass propagation time delay τ of electromagnetic waves propagating from the transceiving feed (2) to the spatial pixel point and then reflecting back to the transceiving feed (2), according to the time delay τ, extracting the signal value at the corresponding time from the time domain signal, and accumulating the signal value to the image intensity of the pixel spatial pixel point, and completing the accumulation projection by traversing all spatial pixel points and all measurement positions to generate a reconstructed image reflecting the spatial distribution of the scattering intensity of the target region.

10. A method of stray signal imaging diagnosis in a compact range darkroom, applied to the system of any one of claims 1-9, characterized in that, The method comprises: erecting the scanning frame (1) in front of the feed support (4) to calibrate the position of the scanning frame (1); configuring the compact range system, connecting the scanning frame (1), the transceiving feed (2), the vector network analyzer (5) and the control computer (6); controlling the rotation axis of the scanning frame (1) to be horizontal by the control computer (6), setting the test frequency band, the travel range of the scanning frame (1), the stepping interval and the transmission power of the vector network analyzer (5), and starting the test; The control computer (6) controls the rotation shaft of the scanning frame (1) to be vertical, and sets the test frequency band, the scanning frame (1) stroke range, the stepping interval and the vector network analyzer (5) transmission power again to perform the test; The control computer (6) processes the test data to perform imaging processing; The imaging result is analyzed, and the stray position is judged according to the distribution of strong scattering points in the imaging.

Images