Near-field scattering imaging diagnostic system for non-cooperative large target at channel entrance

Abstract

The near-field scattering characteristic test technology can be used for detecting the structure and internal composition of a large target (such as an airplane, a tank and a civil automobile), and has important application in the aspects of safety, production, transportation, test, detection and the like. The invention discloses a channel entrance non-cooperative large-target near-field scattering imaging diagnosis system in order to overcome the defects that in a traditional near-field scattering imaging diagnosis method, complete target cooperation is needed, and the testing process is complex. The system is composed of a multi-angle one-dimensional MIMO array antenna, an amplitude-phase regulation and control network, a radio frequency transceiver, a three-dimensional laser scanner and an upper computer, wherein the multi-angle one-dimensional MIMO array antenna is arranged on a four-wall frame of a channel entrance. The system performs full-angle electromagnetic wave irradiation on a moving non-cooperative target to obtain near-field scattering data of the target; obtaining the position and track information of the target through optical scanning point cloud imaging; and performing comprehensive processing on the near-field scattering data and the position track information of the target to obtain a near-field imaging result and performing diagnosis. The method has the advantages of convenience, low cost and high flexibility, and is expected to play an important role in non-cooperative target imaging diagnosis.

Description

Technical Field

[0001] The present invention relates to electromagnetic scattering characteristics testing technology, and in particular to a near-field scattering imaging system and method for non-cooperative targets traveling at the entrance of a channel structure with a four-wall frame. The system is suitable for near-field scattering imaging diagnosis of large equipment such as aircraft, tanks, and civilian vehicles in a non-cooperative state. Background Art

[0002] Scattering characteristic measurement technology is an important means of measuring the electromagnetic scattering properties of targets. It can detect the structure and internal components of large targets (such as aircraft, tanks, and civilian vehicles) and has important applications in security, production, transportation, testing, and inspection. Scattering characteristic measurements are generally performed using three methods: far-field, near-field, and compact-field. Traditional far-field testing requires a maximum phase deviation of no more than 22.5° on the target under test. This increases the test distance, resulting in a larger measurement site and often requiring outdoor measurements, which are susceptible to interference from complex backgrounds such as weather, ground clutter, and multipath. While compact-field measurements can be performed in a microwave anechoic chamber, effectively avoiding complex background interference from the outdoor field and significantly reducing the measurement distance, they require high machining precision for the compact-field reflector. Larger targets require larger reflectors, and operating frequencies below 2 GHz result in lower measurement accuracy, high equipment operation and maintenance costs, and low space utilization. Near-field testing technology offers more flexible site and equipment requirements, is convenient and fast, and is a key method for measuring target scattering properties. Combining a spherical wave feed with a near-to-far-field transformation algorithm can reduce test site construction costs and facilitate testing of large targets. After obtaining the scattering characteristic data of the target, the spatial distribution of the target's equivalent scattering center, that is, the scattering image of the target, can be obtained through the imaging algorithm, and the structure and internal composition of the target can be diagnosed through the image.

[0003] Traditional near-field scattering imaging diagnostic methods have harsh testing conditions and have disadvantages such as requiring full cooperation from the target and complex testing procedures. The patent "Target Electromagnetic Defect Positioning and Identification Method Based on ISAR Imaging" (Patent No.: CN118131233A) published by Yao Ai'ai et al. uses point source spherical waves as the feed source, and has the advantages of short testing cycle, simple and fast system construction, and strong functional scalability, but still requires a turntable and support structure to enable the target to complete the movement required to obtain scattering characteristic data. The patent "A MIMO Array Near-Field Measurement System and Method" (Patent No.: CN116203324A) published by Ren Qunting et al. can reduce the number of required antennas and increase aperture utilization through antenna transceiver multiplexing, but it also requires a rotating mechanism and antenna bracket to drive the antenna array to rotate, and the testing process is relatively complicated.

[0004] Whether the target is placed on a turntable and rotated, or the antenna array is placed on a rotating mechanism and rotated, the purpose is to obtain full-angle test data of the target. This patent proposes that a four-wall structural frame in the shape of a passage, tunnel, warehouse entrance, etc. can be used to arrange antennas at multiple angles on the four-wall frame at the entrance, and full-angle illumination of the target can be achieved by flexibly controlling the transmission and reception of the antenna. Using this form, the present invention combines a near-field scattering data measurement device and an optical scanning point cloud imaging device to propose a near-field scattering imaging diagnostic system for non-cooperative targets at the entrance of a channel, in which the position and trajectory of the target are irregular and non-uniform. This system can improve the applicability of near-field scattering imaging diagnostic technology, and is of great significance in the fields of production, testing, transportation, etc. where this technology is used. Summary of the Invention

[0005] The purpose of the present invention is to provide a near-field scattering imaging system and method for a moving non-cooperative target using a channel four-wall structural frame, so as to solve the problems existing in the prior art of near-field scattering imaging diagnosis of large targets, such as harsh conditions, complex measurement process, long time consumption, and significant environmental influence.

[0006] The technical solution adopted by the present invention is: a near-field scattering imaging system for a moving non-cooperative target, which uses a multi-angle one-dimensional MIMO array antenna arranged on the four wall frames of the channel entrance to perform 360-degree full-angle electromagnetic wave irradiation on the moving non-cooperative target; uses a radio frequency transceiver to transmit and receive electromagnetic signals to obtain the target's near-field scattering data; uses a three-dimensional laser scanner to perform optical scanning imaging on the target to obtain the target's position and trajectory information; uses a host computer to set the working parameters of the radio frequency transceiver and the on-off status of each transceiver control switch in the amplitude and phase control network, and comprehensively processes the near-field scattering data and optical scanning imaging results, and uses point cloud and other methods to determine the target's position and trajectory, thereby obtaining near-field imaging results and performing diagnosis.

[0007] The near-field scattering imaging system consists of a MIMO array antenna, an amplitude and phase control network, a radio frequency transceiver, a three-dimensional laser scanner and a host computer.

[0008] The MIMO array antenna is arranged in a one-dimensional array on the four walls of the channel entrance, such as the door beam, door frame, and ground groove. The array elements are flexibly controlled to be in the transmitting or receiving state as needed. By switching different array element combinations, 360-degree full-angle illumination of the target is completed. The length is set according to the channel entrance size and test requirements. To ensure resolution, the array antennas of the MIMO array antenna should maintain a certain spacing, such as λ / 2.

[0009] The amplitude and phase control network is connected to the MIMO array antenna and is used to control the amplitude and phase of the antenna unit. It includes multiple transceiver control switches. The isolation of each transceiver control switch should be greater than a certain value, such as not less than 80dB.

[0010] Each antenna element in the antenna array is connected to the transmit link of the radio frequency transceiver device through the corresponding transceiver control switch in one amplitude and phase control network, and is connected to the receive link of the radio frequency transceiver device through the corresponding transceiver control switch in another amplitude and phase control network.

[0011] The radio frequency transceiver is used to transmit and receive frequency sweep signals.

[0012] The three-dimensional laser scanner is used to transmit and receive optical scanning signals.

[0013] The host computer is connected to the amplitude and phase control network, the radio frequency transceiver device and the three-dimensional laser scanner, and is used to set the operating parameters of the radio frequency transceiver device and the on-off status of each transceiver control switch in the microwave switch array according to the input setting instructions, and is used to comprehensively process and diagnose the near-field scattering data and the optical scanning point cloud imaging results.

[0014] The beneficial effects of the present invention are:

[0015] 1. Combined with the optical scanning imaging results, the position and trajectory of the target can be accurately determined, and near-field scattering imaging diagnosis can be performed on moving non-cooperative targets. The test conditions are relatively loose and do not require full cooperation from the target. The measurement process is simple, time-saving, low-cost, and widely applicable.

[0016] 2. Compared with existing far-field electromagnetic scattering measurements, the present invention can set different excitations for the transmitting antenna array units by adjusting the amplitude and phase control network, so that the required test beam is generated at a shorter distance, thereby greatly reducing the test distance. Combined with the layout of the MIMO antenna suspended on the entrance frame or placed in the ground groove, the flexibility of the system layout is improved.

[0017] 3. The production requirements for test equipment are lower than those for compact ranges, and the production cost of test equipment is lower than the cost of compact range equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The channel non-cooperative large target near-field scattering imaging system of the first embodiment of the present invention;

[0019] Figure 1 Description of the reference numerals:

[0020] 1-Multi-angle MIMO array antennas arranged on the four walls of the channel; 2-Amplitude and phase control network; 3-RF transceiver equipment; 4-3D laser scanner; 5-Host computer; 6-Frame at the entrance of the channel with four walls; 7-Groove; 8-Target to be measured. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of implementation of the present invention is not limited thereto.

[0022] like Figure 1 As shown, the channel non-cooperative large target near-field scattering imaging system of this embodiment includes: a multi-angle MIMO array antenna 1 arranged on the four walls of the channel, used to generate a full-angle illumination beam and receive scattered waves; an amplitude and phase control network 2, used to control the transmission and reception state and amplitude and phase of the antenna unit to complete the synthesis of test waves and the reception of full-angle scattered waves; a radio frequency transceiver device 3, used to transmit and receive swept frequency signals; a three-dimensional laser scanner 4, used to transmit and receive optical scanning signals; a host computer 5, used to set the operating parameters of the radio frequency transceiver device and the on-off state of each transceiver control switch in the microwave switch array according to the input setting instructions, and used to comprehensively process and diagnose the near-field scattering data and the optical scanning point cloud imaging results.

[0023] Example 1

[0024] At the entrance of a certain airport hangar, a non-cooperative large-target near-field scattering imaging diagnostic system for the entrance of the passageway is installed. The one-dimensional MIMO array antenna at the door beam and in the ground groove is 60 meters long and consists of 240 antenna elements. The one-dimensional MIMO array antenna at the door frames on both sides is 20 meters long and consists of 80 antenna elements. The distance between antenna elements is 0.25 meters, and the measurement frequency band is 0.4GHz-2GHz. The antenna is buried 10cm deep in the ground groove, and the space between the antenna and the ground should ensure that only air is used as a medium. The groove width is 20cm and does not affect the movement of the aircraft. Each antenna element in the antenna array is connected to the transmit link of the radio frequency transceiver device through the corresponding transceiver control switch in one of the amplitude and phase control networks, and is connected to the receive link of the radio frequency transceiver device through the corresponding transceiver control switch in another amplitude and phase control network. The three-dimensional laser scanner and host computer are installed at the same time.

[0025] When an aircraft enters the hangar, the host computer sends instructions to the amplitude and phase control network. By switching different array element combinations, the MIMO array antenna generates the required test waves and illuminates the aircraft at all angles. Simultaneously, the array elements are controlled accordingly so that the system can receive the target's full-angle scattering data. The radio frequency transceiver transmits and receives electromagnetic signals to obtain the aircraft's near-field scattering data. The three-dimensional laser scanner performs an optical scan of the aircraft to obtain its position and trajectory information. The host computer comprehensively processes the near-field scattering data and optical scanning imaging results, determines the aircraft's position and trajectory using a point cloud method, and then obtains near-field imaging results and performs diagnosis, successfully locating and identifying electromagnetic defects on the aircraft's surface.

[0026] Example 2

[0027] At the entrance of a large truck warehouse, a non-cooperative large-target near-field scattering imaging diagnostic system for the entrance is installed. The one-dimensional MIMO array antenna at the door beam and in the ground groove is 6 meters long and consists of 120 antenna elements. The one-dimensional MIMO array antenna at the door frames on both sides is 4 meters long and consists of 80 antenna elements. The distance between antenna elements is 0.05 meters, and the measurement frequency range is 8GHz-12GHz. The antenna is buried 10cm deep in the ground groove, and the space between the antenna and the ground should be only air as a medium. The groove is 5cm wide and does not affect the movement of the truck. Each antenna element in the antenna array is connected to the transmit link of the radio frequency transceiver device via a corresponding transceiver control switch in the amplitude and phase control network, and is connected to the receive link of the radio frequency transceiver device via a corresponding transceiver control switch in another amplitude and phase control network. The three-dimensional laser scanner and host computer are also installed.

[0028] When a truck enters the warehouse, the host computer sends instructions to the amplitude and phase control network. By switching different array element combinations, the MIMO array antenna generates the required test waves and illuminates the truck 360 degrees. Simultaneously, the array elements are controlled accordingly so that the system can receive scattering data from the target at all angles. The radio frequency transceiver transmits and receives electromagnetic signals to obtain near-field scattering data from the truck. The 3D laser scanner performs an optical scan of the truck to obtain its location and trajectory. The host computer comprehensively processes the near-field scattering data and the optical scanning imaging results, using point cloud methods to determine the truck's location and trajectory. This in turn generates near-field imaging results for diagnosis and analysis of the cargo's structure and internal composition.

Claims

1. A non-cooperative large target near-field scattering imaging diagnostic system at the channel entrance, characterized in that: The system includes a multi-angle one-dimensional MIMO array antenna arranged on the four wall frames of the channel entrance, an amplitude and phase control network, a radio frequency transceiver, a three-dimensional laser scanner and a host computer: The MIMO array antenna is arranged in a one-dimensional array on the four wall frames of the channel entrance. The array elements are flexibly controlled to be in the transmitting or receiving state according to the needs. By switching different array element combinations, the target is irradiated with electromagnetic waves at 360 degrees. The amplitude and phase control network is connected to the MIMO array antenna and is used to control the amplitude and phase of the antenna unit, and includes multiple transceiver control switches, and the isolation of each transceiver control switch is not less than a certain value; Each antenna element in the antenna array is connected to the transmit link of the radio frequency transceiver device via the corresponding transmit / receive control switch in one amplitude / phase control network, and is connected to the receive link of the radio frequency transceiver device via the corresponding transmit / receive control switch in another amplitude / phase control network; The radio frequency transceiver is used to transmit and receive sweep frequency signals; The three-dimensional laser scanner is used to transmit and receive optical scanning signals; The host computer is connected to the amplitude and phase control network, the radio frequency transceiver device and the three-dimensional laser scanner, and is used to set the operating parameters of the radio frequency transceiver device and the on-off status of each transceiver control switch in the amplitude and phase control network according to the input setting instructions, and is used to comprehensively process and diagnose near-field scattering data and optical scanning imaging results.

2. The non-cooperative large target near-field scattering imaging diagnostic system at the channel entrance according to claim 1, characterized in that: The MIMO array antennas are respectively arranged on the four walls of the passage entrance, such as the door beam, door frame and ground groove, to form full-angle illumination and testing for the target.

3. The non-cooperative large target near-field scattering imaging diagnostic system at the channel entrance according to claim 1, characterized in that: Each group of the MIMO array antennas is a one-dimensional antenna array, and the length is set according to the channel entrance size and test requirements.

4. The non-cooperative large target near-field scattering imaging diagnostic system at the channel entrance according to claim 1, characterized in that: The amplitude and phase control network is used to control the transmitting and receiving states and the amplitude and phase of the antenna unit to achieve full-angle illumination and testing of the target.

5. The non-cooperative large target near-field scattering imaging diagnostic system at the channel entrance according to claim 1, characterized in that: The swept frequency signals transmitted and received by the radio frequency transceiver are used to obtain near-field scattering data of the target.

6. The non-cooperative large target near-field scattering imaging diagnostic system at the channel entrance according to claim 1, characterized in that: The three-dimensional laser scanner is used to perform optical scanning and imaging on a target to obtain the position and trajectory information of the target.

7. The non-cooperative large target near-field scattering imaging diagnostic system at the channel entrance according to claim 1, characterized in that: The host computer comprehensively processes the near-field scattering data and the optical scanning imaging results, determines the position and trajectory of the target through methods such as point cloud, and then obtains the near-field imaging results and performs diagnosis.

Images