Interferometric passive microwave imaging system and method based on multi-beam feed reflector antenna

Abstract

The invention discloses an interference type passive microwave imaging system based on a multi-beam feed reflector antenna, the system comprises an interference array and a processing unit, the interference array comprises P multi-beam feed reflector antenna forming arrays, each multi-beam feed reflecting surface antenna comprises a reflecting surface for reflecting and focusing microwave signals and a phase control feed source array for receiving the microwave signals reflected and focused by the reflecting surface; the phased feed source array comprises M unit antennas, and the M unit antennas are divided into N phased array feed source clusters; each phased array feed source cluster receives a microwave signal with a set direction; and the processing unit is used for performing correlation operation on microwave signals of the phased array feed source clusters with the same pointing direction of the P multi-beam feed reflector antennas to form interference type passive microwave imaging of the pointing direction. According to the invention, the number of interference units and the interference operation scale of the high-resolution passive microwave imaging system are reduced, the sensitivity of the high-resolution passive microwave imaging system is improved, and the imaging field of view is expanded.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of passive microwave imaging detection, in particular to an interferometric passive microwave imaging system and method based on a multi-beam fed reflector antenna. BACKGROUND

[0002] A reflector antenna is a high-gain antenna commonly used in wireless communication and radar systems. Its basic principle is to reflect and focus electromagnetic waves from a feed source into a specific directional beam through the shape and material properties of the reflector, thereby achieving efficient signal transmission and reception. A reflector antenna is usually composed of a parabolic reflector and a feed source. The geometric properties of the parabolic reflector enable it to focus incident parallel waves to its focal point, for example, reference: Antenna Theory Analysis and Design (C. A. Balanis).

[0003] A passive microwave imaging system achieves target detection by receiving natural radiation microwave signals, and has the advantages of all-weather and all-day operation. In the prior art, an interferometric passive microwave imaging technology uses multiple synchronous receiving units to form an interference array, each receiving unit acts as an interference unit to participate in the pairwise correlation operation of the interference array, and completes effective coverage observation in the spatial frequency domain. Then, image inversion based on inverse Fourier operator is used to complete spatial domain imaging detection. For example, the patent document with publication number CN 115508832A and the name "An interferometric passive microwave imaging system and method based on array beam forming" discloses a technology: "An interferometric passive microwave imaging system and method based on array beam forming, wherein array beam forming includes phased array beam forming and digital beam forming. The data after array beam forming will be used to complete imaging detection by using an interferometric passive microwave imaging method. A plurality of antenna units form a phased subarray, and the phased array beams formed by all phased subarrays are pointing in the same direction. A plurality of phased subarrays form a digital subarray, and the digital subarray generates digital beams within the phased array beam pointing range. A plurality of digital subarrays form an interference array, and each digital subarray acts as a unit to participate in the interferometric correlation operation of the interference array, and the interference array completes interferometric passive microwave imaging within the digital beam range." However, the interferometric passive microwave imaging technology requires a large-size array to achieve high spatial resolution imaging, and a large-aperture interference unit is used to suppress system aliasing. The large-aperture interference unit reduces the instantaneous imaging field of view, and the large field of view imaging has low efficiency and low observation sensitivity. SUMMARY

[0004] The present application aims at overcoming the shortcomings of single reflector antenna, such as low resolution and small imaging area, overcoming the shortcomings of high resolution interferometric passive microwave imaging technology, such as small instantaneous imaging field of view, overcoming the shortcomings of array beam forming technology, such as large number of antenna units and low aperture sparse ratio, and providing an interferometric passive microwave imaging system and method based on multi-beam fed reflector antenna.

[0005] To achieve the above-mentioned purpose, the present application provides an interferometric passive microwave imaging system based on multi-beam fed reflector antenna, characterized in that the system comprises an interference array (6) and a processing unit, the interference array (6) comprises P multi-beam fed reflector antennas (5) forming an array, each multi-beam fed reflector antenna (5) comprises a reflector (4) for reflecting and focusing microwave signals and a phased feed array (3) for receiving the reflected and focused microwave signals of the reflector (4); the phased feed array (3) comprises M unit antennas (1), and the M unit antennas are divided into N phased array feed clusters (2); each phased array feed cluster (2) receives microwave signals with a set direction; and the processing unit is used for performing correlation operation on the microwave signals of the phased array feed clusters (2) with the same direction of the P multi-beam fed reflector antennas (5) to form interferometric passive microwave imaging with the direction.

[0006] As an improvement of the above-mentioned system, the phased feed arrays (3) of the P multi-beam fed reflector antennas (5) are divided into N groups of phased feed clusters, the phased feed clusters in one group are set with the same direction, and the N groups of phased array feed clusters (2) realize spatial grouping of different set directions; and the processing unit simultaneously performs correlation operation on the microwave signals of the N groups of phased array feed clusters (2) to form interferometric passive microwave imaging with different directions.

[0007] As another improvement of the above-mentioned system, the system further comprises a control unit, which changes the set receiving direction of the N phased feed clusters (2) of the phased feed array (3) by changing the division mode of the phased feed clusters (2) in the phased feed array (3) and changing the amplitude and phase weighting of each unit antenna (1) in the phased feed cluster (2), so as to receive the microwave signals with N set directions of the multi-beam fed reflector antenna (5).

[0008] As a further improvement of the above-mentioned system, the unit antennas (1) in the phased feed array (3) are arranged at equal intervals according to a rectangular or triangular grid; and the unit antennas (1) within the envelope of the phased feed cluster (2) all belong to the phased feed cluster, so as to ensure the consistency of the signals in the cluster.

[0009] As another improvement of the above-mentioned system, the P multi-beam fed reflector antennas (5) form a Y-shaped array.

[0010] To achieve the above objectives, the present invention provides an interferometric passive microwave imaging method based on a multi-beam fed reflector antenna, the method comprising: P multi-beam fed reflector antennas (5) are formed into an interference array (6). Each of the multi-beam fed reflector antennas (5) includes a reflector (4) for reflecting and focusing microwave signals and a phased feed array (3) for receiving microwave signals reflected and focused by the reflector (4). The phased feed array (3) includes M unit antennas (1). The M unit antennas are divided into N phased array feed clusters (2); each phased array feed cluster (2) is adjusted to receive a microwave signal with a set direction. The processing unit performs correlation operations on the microwave signals of the phased array feed cluster (2) of P multi-beam fed reflector antennas (5) pointing in the same direction to form an interferometric passive microwave imaging in that direction.

[0011] As an improvement to the above method, it also includes: different settings of the N phased array feed clusters (2) of the interferometric array (6) simultaneously cover N regions. By changing the orientation of the N phased array feed clusters (2), Q observations can achieve large field-of-view imaging of Q×N regions in time division.

[0012] As a further improvement to the above method, the processing unit performs correlation operations on the microwave signals of the phased array feed cluster (2) of P multi-beam fed reflector antennas (5) pointing in the same direction to form interferometric passive microwave imaging, and also includes the following steps: Using P×N phased array feed clusters (2), P×N beam directions are formed by phased array beamforming method. After passing through the reflector (4), the microwave beams are received by the phased array feed clusters (2) with P×N directions. The P×N phased array feed clusters (2) are divided into N groups, and the beam directions of the P phased array feed clusters (2) in each group are consistent. By configuring the beamforming parameters of the phased feed array (3), the beam pointing of N sets of phased array feed clusters (2) is controlled to complete the scanning of the overall observation area; Interference correlation operations are performed within each of the N phased array feed clusters (2) of the interferometric array (6). Each phased array feed cluster (2) beam in each group participates in the interferometric correlation operation of each group as an interferometric unit beam. The interferometric correlation operation of each group completes the interferometric passive microwave imaging within the beam range of that group. The N groups of interferometric passive microwave imaging constitute a complete interferometric passive microwave imaging.

[0013] As a further improvement to the above method, the unit antennas (1) in the phased feed array (3) are arranged at equal intervals in a rectangular or triangular grid; the unit antennas (1) within the envelope of the phased feed cluster (2) all belong to the phased feed cluster to ensure signal consistency within the cluster.

[0014] As a further improvement to the above method, the P multi-beam fed reflector antennas (5) form a Y-shaped array.

[0015] The advantages and technical effects of this invention are as follows: The system of this invention reduces the number of antenna elements and improves detection sensitivity, while the method of this invention reduces the complexity of interferometric correlation calculations. Specifically: Reducing the number of interferometric elements and the scale of interferometric computation in high-resolution passive microwave imaging systems: The spatial resolution of interferometric passive microwave imaging is proportional to the system size. By using multi-beam fed transmitting antennas as interferometric elements and increasing the sampling interval in the spatial frequency domain, the number of interferometric elements is reduced, thus lowering the scale of interferometric computation. Doubling the sampling interval halves the number of interferometric elements and reduces the scale of interferometric computation by 75%.

[0016] Improving the sensitivity of high-resolution passive microwave imaging systems: The sensitivity of interferometric passive microwave imaging is inversely proportional to the aperture sparsity ratio. With the size of the interferometric array remaining constant, the larger the total area of ​​the interferometric cells and the smaller the aperture sparsity ratio, the higher the sensitivity. The sensitivity doubles for every doubling of the spacing between the interferometric cells, thus expanding the imaging field of view. Attached Figure Description

[0017] Figure 1 A schematic diagram of an interferometric passive microwave imaging system array based on a multi-beam fed reflector antenna, according to a specific embodiment of the present invention; Figure 2 This is a schematic diagram of the secondary beam results in a specific implementation method; Figure 3 This is a schematic diagram of the interferometric passive microwave dual-point source imaging results based on a multi-beam fed reflector antenna, as shown in the specific implementation.

[0018] Explanation of reference numerals in the attached diagram: Detailed Implementation

[0019] The technical solutions provided by the present invention are further illustrated below with reference to embodiments. The description of exemplary embodiments is merely for illustrative purposes and is by no means a limitation on the present invention or its application or use.

[0020] This invention provides an interferometric passive microwave imaging system based on multi-beam-fed reflector antennas. The system includes an interferometric array formed by multiple multi-beam-fed reflector antennas. Each multi-beam-fed reflector antenna comprises a phased-array feed and a reflector. The reflector reflects weak microwave signals from the target object back to the phased-array feed. Data received by the phased-array feed is sent to a processing unit, which then uses an interferometric passive microwave imaging method to perform imaging detection based on the data received from the multiple phased-array feeds. The phased-array feed comprises multiple element antennas with amplitude and phase adjustment phase control functions. The phased array feed array is divided into multiple phased array feed clusters. Each phased array feed cluster forms its own directional beam (i.e., receives microwave signals reflected by the reflector in its own direction). When a microwave signal is reflected by the reflector in a certain direction to the phased array feed array, it will be received by the phased array feed cluster pointing to that direction. The phased array feed arrays of each multi-beam fed reflector antenna are divided into feed clusters in the same way, forming multiple feed clusters with the same number and direction in the interferometric array. The multiple feed clusters with the same direction in each multi-beam fed reflector antenna array are correlated, and the reflector antenna interferometric array simultaneously completes interferometric passive microwave imaging in multiple directions formed by the multiple feed cluster arrays.

[0021] Because multi-beam fed reflector antennas have the reversibility of both receiving and transmitting signals, the following description of transmitting a beam in a certain direction can also be understood as receiving a beam in a certain direction. This is only for the convenience of description and should be understood by those skilled in the art without causing any misunderstanding.

[0022] The technical solution of the specific embodiments of the present invention is detailed below: like Figure 1 As shown, an interferometric passive microwave imaging system based on a multi-beam-fed reflector antenna is generally characterized by the coordinated operation of an interferometric array (6) and a multi-beam-fed reflector antenna (5). Specifically, the microwave imaging system includes an interferometric array (6), which comprises multiple multi-beam-fed reflector antennas (5); the array configuration can be arbitrarily selected as needed, for example, the multiple multi-beam-fed reflector antennas (5) can be arranged in a Y-shape. As an integral structure, the interferometric array (6) achieves multi-channel signal reception and interferometric measurement through P spatially distributed multi-beam-fed reflector antennas.

[0023] Each multi-beam fed reflector antenna (5) includes a phased-array feed array (3) and a reflector (4). The phased-array feed array (3), as a key component for receiving the beam, divides the M unit antennas (1) into N phased-array feed clusters (2), so that each phased-array feed cluster (2) can independently control the beam characteristics, that is, it can independently receive microwave signals with a set direction; the reflector (4) is used to reflect and focus microwave signals, converting the primary beam into a high-gain secondary beam, improving signal directivity and signal-to-noise ratio. The unit antenna (1), as a basic receiving unit, for example, adopts a microstrip or horn antenna structure and operates in the microwave frequency band (such as 1-10GHz). By dividing the phased-array feed clusters (2), the flexible generation of the beam is realized, that is, the microwave signal is received in a set direction by amplitude and phase adjustment.

[0024] The system's processing unit performs correlation operations on microwave signals from P multi-beam-fed reflector antennas (5) pointing to the same phased array feed cluster (2) to form interferometric passive microwave imaging in that direction. Overall, the system solves the problems of small field of view and low efficiency by integrating multiple antennas, multiple beams, and reflector focusing: the interferometric array (6) provides high spatial resolution, the multi-beam-fed reflector antennas (5) achieve simultaneous coverage of multiple regions, and the feed cluster (2) division supports dynamic beam adjustment, thereby achieving high spatial resolution and flexible observation with a large field of view in passive microwave imaging.

[0025] As an improvement to the above implementation, the phased array feed array (3) divides into N phased array feed clusters (2). Each phased array feed cluster uses amplitude and phase weighting to form primary beams pointing in different directions, that is, it forms a primary beam that receives microwave signals from the reflector (4) in a set direction. After these primary beams are reflected by the reflector (4), they are converted into secondary beams pointing in different directions due to the focusing and direction transformation of the reflector (4). That is, the reflector (4) focuses and transforms the microwave signal in the set direction and receives it from the phased array feed cluster (2) in the set direction. The interference array (6) thus forms N groups of secondary beams. Each group consists of beams pointing in the same direction generated by P multi-beam fed reflector antennas (5), realizing spatial grouping of beams. That is, the P phased array feed clusters (2) in a group are set in the same direction, and the N groups of phased array feed clusters (2) are spatially grouped with different set directions, so that the N groups of phased array feed clusters (2) cover the entire space. The beneficial effects of this are improved imaging efficiency and instantaneous imaging field of view: by processing multiple points in parallel, the system can simultaneously acquire radiation data from multiple regions and perform high-resolution interferometric imaging in each region.

[0026] As an improvement to the above implementation, the system also includes a control unit that dynamically adjusts the partitioning of the phased array feed cluster (2) through software or hardware control, for example, changing from uniform partitioning to non-uniform partitioning, to optimize the beam shape and pointing. Simultaneously, the amplitude and phase weighting of the unit antenna (1) employs digital beamforming technology, implemented through phase shifters and attenuators, for example, by applying Taylor or Chebyshev weighting functions to reduce sidelobes. Thus, the change in the primary beam pointing is mapped to the secondary beam via the reflector (4), achieving rapid scanning and multi-area coverage. Beneficial effects include: the system can adapt to different observation scenarios, such as switching from wide-area scanning to high-resolution fixed-point observation; dynamic adjustment reduces hardware dependence, improving reliability and maintainability; and it supports time-series observation strategies, expanding the field of view by changing the pointing over time.

[0027] As one of the improvements to the above implementation, the equidistant arrangement of the unit antennas (1) (e.g., the row and column spacing of a rectangular grid are both half a wavelength, or the triangular grid is arranged in a hexagonal pattern) optimizes the aperture utilization and beamforming performance, and reduces grating lobes and mutual coupling effects; the envelope of the phased array feed cluster (2) is defined as a geometric region (e.g., circular or rectangular), and all unit antennas (1) within the envelope participate in the beamforming of the cluster, ensuring signal consistency within the cluster. For example, in a rectangular grid, the cluster envelope can cover a subset of specific rows and columns. The beneficial effects of this are improved beam accuracy and system stability: regular arrangement reduces design complexity and facilitates large-scale integration; the well-defined cluster division avoids signal confusion and enhances the independence and controllability of multiple beams.

[0028] This invention also provides an interferometric passive microwave imaging method based on a multi-beam fed reflector antenna, the method comprising: P multi-beam fed reflector antennas (5) are formed into an interference array (6). Each of the multi-beam fed reflector antennas (5) includes a reflector (4) for reflecting and focusing microwave signals and a phased feed array (3) for receiving microwave signals reflected and focused by the reflector (4). The phased feed array (3) includes M unit antennas (1). The M unit antennas (1) are divided into N phased array feed clusters (2); each phased array feed cluster (2) is adjusted to receive a microwave signal with a set direction. The processing unit performs correlation operations on the microwave signals of the phased array feed cluster (2) of P multi-beam fed reflector antennas (5) pointing in the same direction to form an interferometric passive microwave imaging in that direction.

[0029] The core of this method lies in the signal processing and imaging process. First, the P reflective surfaces of the interferometric array (6) receive N sets of signals, each set of P signals pointing to the same area. The passive microwave signals received by the unit antenna (1) with a set direction are synthesized by amplitude and phase weighting (e.g., using complex weighting coefficients) to generate a combined signal representing the set direction beam area. The processing unit obtains the visibility function of the image of the pointing area through interferometric correlation operation, and finally generates N two-dimensional images (e.g., brightness temperature distribution map). The N phased feed clusters of a phased feed array (3) output N combined signals, and the interferometric array (6) containing P multi-beam fed reflective surface antennas (5) outputs N sets of N×P combined signals. The P combined signals with the same beam direction are subjected to interferometric correlation operation and the beam coverage area is imaged to obtain a total of N two-dimensional images.

[0030] As an improvement to the above implementation method, time-division observation is achieved by dynamically adjusting the beam pointing of the phased-array feed cluster (2). For example, the system can cover Q×N regions in Q observations. For instance, the first observation covers regions 1-N, the second covers regions N+1-2N, and so on. The beneficial effect of this is that it significantly improves imaging efficiency and field of view expansion: the time-division observation strategy reduces the single scan time and is suitable for large field of view observations.

[0031] As an improvement to the above implementation method, scanning is achieved by controlling the beam pointing of the phased array feed cluster (2) through parameter configuration (such as weighting coefficients and phased array feed cluster division); multiple primary beams are formed by the phased array feed array and multiple secondary beams are formed after reflection by the reflector (in passive target detection, the microwave signal is received by the phased array feed array after reflection by the reflector). The interferometric operation step performs interferometric imaging in a group of phased array feed clusters (2) with the same beam pointing, and uses relevant algorithms (such as Fourier transform method and G matrix method) to generate a two-dimensional brightness temperature image in the beam, and finally merges the images with different pointing directions into a complete image.

[0032] Example 1 like Figure 1 The diagram shown is an array schematic of an interferometric passive microwave imaging system based on a multi-beam fed reflector antenna according to Embodiment 1 of the present invention. The antenna elements are arranged at equal intervals to form a phased feed array.

[0033] Specifically, this invention proposes an interferometric passive microwave imaging system based on a multi-beam fed reflector antenna. The system includes: a phased feed array (3) composed of M unit antennas (1), each phased feed array (3) being divided into N phased feed clusters (2) in the same manner, and these N phased feed clusters (2) pointing in different directions; a phased feed array (3) and a reflector (4) forming a multi-beam fed reflector antenna (5), and the phased feed clusters (2) being set to receive the image after passing through the reflector (4). Pointing beam; P multi-beam fed reflector antennas (5) constitute an interferometric array (6). The interferometric array (6) contains N groups of phased array feed clusters (2). Each group contains P phased array feed clusters (2) with the same beam pointing. The set pointing beam received by each phased array feed cluster (2) is used as an interferometric unit beam to participate in the interferometric correlation operation of all phased array feed clusters (2) with the same pointing in the interferometric array (6). The interferometric array (6) completes interferometric passive microwave imaging in the pointing beam corresponding to the phased array feed cluster (2).

[0034] The interferometric array (6) contains P×N phased array feed clusters (2). P is the number of phased array feed arrays (3) in the interferometric array (6), and N is the number of phased array feed clusters (2) in a single phased array feed array (3). Each phased array feed cluster (2) is configured with a receiving beam direction. The beam directions of identical phased array feed clusters (2) in each phased array feed array (3) are consistent, forming N groups of phased array feed clusters (2). Each group contains P phased array feed clusters (2) with the same direction. By dividing the phased array feed clusters into different phased array feed clusters and configuring the phase parameters of the unit antennas respectively, the multi-beam fed reflector antenna is controlled to complete the scanning of the overall observation area.

[0035] The interferometric array (6) performs interferometric correlation operations within each of the N groups of phased feed clusters (2). The interferometric correlation operation of each group completes the interferometric passive microwave imaging within the beam pointing range of that group. The N groups of interferometric passive microwave imaging constitute a complete interferometric passive microwave imaging.

[0036] Example 2 This invention proposes an interferometric passive microwave imaging method based on a multi-beam fed reflector antenna, implemented using the aforementioned system. The method includes the following steps: First, P×N phased array feed clusters (2) are used to form P×N beam pointing directions through a phased array beamforming method. After passing through the reflector (4), the microwave beams are received by the phased array feed clusters (2) with P×N pointing microwave beams. The P×N phased array feed clusters (2) are divided into N groups of phased array feed clusters (2), and the beam pointing of the P phased array feed clusters (2) in each group is consistent. By dividing the phased array feed clusters and configuring the amplitude and phase parameters of the unit antennas (1) respectively, the multi-beam fed reflector antennas (5) are controlled to complete the scanning of the overall observation area; that is, by configuring the beamforming parameters of the phased array feed array (3), the beam pointing of N sets of phased array feed clusters (2) is controlled to complete the scanning of the overall observation area.

[0037] Finally, interferometric correlation operations are performed within each of the N phased array feed clusters (2) of the interferometric array (6). Each phased array feed cluster (2) beam in each group participates in the interferometric correlation operation of each group as an interferometric unit beam. The interferometric correlation operation of each group completes the interferometric passive microwave imaging within the beam pointing range of that group. The N groups of interferometric passive microwave imaging constitute a complete interferometric passive microwave imaging.

[0038] The embodiments shown in this invention are illustrated with reference to... Figure 1 The diagram illustrates an interferometric passive microwave imaging system array based on a phased array-fed transmitting surface antenna. In the above embodiment, the interferometric passive microwave imaging system based on a phased array-fed transmitting surface antenna has an antenna element spacing of [missing information]. , To detect the wavelength, a phased feed array (3) is constructed from M=144 unit antennas 1. The phased feed array is divided into N=9 phased feed clusters 2. The beam directions of the N=9 phased feed clusters (2) within the same phased feed array (3) are different. An interferometric array (6) is constructed from P=7 multi-beam fed reflector antennas (5). For example, the 7 multi-beam fed reflector antennas (5) can be arranged in a Y shape. The interferometric array (6) contains P×N=63 phased feed clusters (2), which can be divided into N=9 groups. The beam directions of the P=7 phased feed clusters (2) in each group are consistent. P×N=63 phased array feed clusters (2) will receive microwave signals that form P×N=63 beams after passing through the reflector. Each phased array feed cluster (2) participates in the interferometric correlation operation of the interferometric array (6) as an interferometric unit beam. The interferometric array (6) completes interferometric passive microwave imaging within the beam range of the phased array feed clusters (2). This embodiment is a Y-type interferometric array with a hexagonal spatial frequency coverage and an angular resolution of 0.85°. Compared with traditional imaging technology, it achieves higher spatial resolution with fewer antennas and improves the aperture sparsity ratio.

[0039] In this embodiment, the interferometric array (6) contains a total of P×N=63 phased array feed clusters (2), which can be divided into N=9 groups. The P=7 phased array feed clusters (2) in each group have the same beam pointing and receive the microwave beam with the set direction formed after passing through the reflector. The beam pointing can be completed by dividing the phased array feed clusters and configuring the amplitude and phase parameters of the unit antennas to complete the scanning of the overall observation area. When the beamforming parameters of the phased array feed clusters are configured so that they point to the center of the observation area, Figure 2The image shows the beam pointing in the direction cosine coordinate system. The power pattern formed by the multi-beam reflector antenna at this time (unit: dB) is shown in the figure. The imaging results of the system for two point targets at this time are as follows: Figure 3 As shown.

[0040] In this embodiment, the interferometric array (6) performs interferometric correlation operations within each group of N=9 phased array feed clusters (2), and the interferometric correlation operations of each group complete the interferometric passive microwave imaging within the beam pointing range of that group; N=9 groups of interferometric passive microwave imaging constitute a complete interferometric passive microwave imaging.

[0041] Based on the above description of specific embodiments, the technical innovations of this invention can be summarized as follows: (1) Use a multi-beam fed reflector antenna as the interferometric unit for passive interferometric imaging to reduce the aperture sparse ratio of the large aperture interferometric array and improve the system sensitivity.

[0042] (2) Passive interferometric imaging is performed simultaneously in multiple beams to expand the instantaneous imaging field of the high-resolution passive microwave imaging system.

[0043] As can be seen from the above description of the specific embodiments of the present invention, the advantages of the present invention are: Reducing the number of interferometric elements and the scale of interferometric computation in high-resolution passive microwave imaging systems: The spatial resolution of interferometric passive microwave imaging is proportional to the system size. By using multi-beam fed transmitting antennas as interferometric elements and increasing the sampling interval in the spatial frequency domain, the number of interferometric elements is reduced, thus lowering the scale of interferometric computation. Doubling the sampling interval halves the number of interferometric elements and reduces the scale of interferometric computation by 75%.

[0044] Improving the sensitivity of high-resolution passive microwave imaging systems: The sensitivity of interferometric passive microwave imaging is inversely proportional to the aperture sparsity ratio. With the size of the interferometric array remaining constant, the larger the total area of ​​the interferometric cells and the smaller the aperture sparsity ratio, the higher the sensitivity. The sensitivity doubles for every doubling of the spacing between the interferometric cells, thus expanding the imaging field of view.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An interferometric passive microwave imaging system based on a multi-beam fed reflector antenna, characterized in that, The system includes an interferometric array (6) and a processing unit. The interferometric array (6) includes P multi-beam fed reflector antennas (5) forming an array. Each multi-beam fed reflector antenna (5) includes a reflector (4) for reflecting and focusing microwave signals and a phased feed array (3) for receiving microwave signals reflected and focused by the reflector (4). The phased feed array (3) includes M unit antennas (1), which are divided into N phased array feed clusters (2). Each phased array feed cluster (2) receives a microwave signal with a set direction. The processing unit is used to perform correlation operations on the microwave signals of the P multi-beam fed reflector antennas (5) pointing to the same phased array feed cluster (2) to form an interferometric passive microwave imaging in that direction.

2. The interferometric passive microwave imaging system based on a multi-beam fed reflector antenna according to claim 1, characterized in that, The phased feed array (3) of the P multi-beam fed reflector antennas (5) is divided into N phased feed clusters. The phased feed clusters within a group are set with the same direction. The N phased feed clusters (2) realize spatial grouping with different set directions. The processing unit simultaneously performs correlation operations on the microwave signals of the N phased feed clusters (2) to form interferometric passive microwave imaging with different directions.

3. The interferometric passive microwave imaging system based on a multi-beam fed reflector antenna according to claim 1, characterized in that, It also includes a control unit, which changes the division method of the phased feed clusters (2) in the phased feed array (3) and changes the amplitude and phase weighting of each unit antenna (1) in the phased feed cluster (2) to change the set receiving direction of the N phased feed clusters (2) in the phased feed array (3), thereby receiving the microwave signals of the N set directions of the multi-beam fed reflector antenna (5).

4. The interferometric passive microwave imaging system based on array beamforming according to any one of claims 1-3, characterized in that, The unit antennas (1) in the phased feed array (3) are arranged at equal intervals in a rectangular or triangular grid; the unit antennas (1) within the envelope of the phased feed cluster (2) all belong to the phased feed cluster to ensure signal consistency within the cluster.

5. The interferometric passive microwave imaging system based on array beamforming according to claim 1, characterized in that, The P multi-beam fed reflector antennas (5) form a Y-shaped array.

6. An interferometric passive microwave imaging method based on a multi-beam fed reflector antenna, characterized in that, The method includes: P multi-beam fed reflector antennas (5) are formed into an interference array (6). Each of the multi-beam fed reflector antennas (5) includes a reflector (4) for reflecting and focusing microwave signals and a phased feed array (3) for receiving microwave signals reflected and focused by the reflector (4). The phased feed array (3) includes M unit antennas (1). The M unit antennas are divided into N phased array feed clusters (2); each phased array feed cluster (2) is adjusted to receive a microwave signal with a set direction; The processing unit performs correlation operations on the microwave signals of the phased array feed cluster (2) of P multi-beam fed reflector antennas (5) pointing in the same direction to form an interferometric passive microwave imaging in that direction.

7. The interferometric passive microwave imaging method based on array beamforming as described in claim 6, characterized in that, Also includes: The N phased array feed clusters (2) of the interferometric array (6) have different settings and directions that simultaneously cover N regions. By changing the direction of the N phased array feed clusters (2), Q observations can achieve large field-of-view imaging of Q×N regions in time division.

8. The interferometric passive microwave imaging method based on array beamforming as described in claim 6, characterized in that, The processing unit performs correlation operations on the microwave signals of the phased array feed cluster (2) pointing in the same direction from the P multi-beam fed reflector antennas (5) to form an interferometric passive microwave image pointing in that direction, and also includes the following steps: Using P×N phased array feed clusters (2), P×N beam directions are formed by phased array beamforming method. After passing through the reflector (4), the microwave beams are received by the phased array feed clusters (2) with P×N directions. The P×N phased array feed clusters (2) are divided into N groups, and the beam directions of the P phased array feed clusters (2) in each group are consistent. By configuring the beamforming parameters of the phased feed array (3), the beam pointing of N sets of phased array feed clusters (2) is controlled to complete the scanning of the overall observation area; Interference correlation operations are performed within each of the N phased array feed clusters (2) of the interferometric array (6). Each phased array feed cluster (2) beam in each group participates in the interferometric correlation operation of each group as an interferometric unit beam. The interferometric correlation operation of each group completes the interferometric passive microwave imaging within the beam range of that group. The N groups of interferometric passive microwave imaging constitute a complete interferometric passive microwave imaging.

9. The interferometric passive microwave imaging method based on array beamforming according to claim 6, characterized in that, The unit antennas (1) in the phased feed array (3) are arranged at equal intervals in a rectangular or triangular grid; the unit antennas (1) within the envelope of the phased feed cluster (2) all belong to the phased feed cluster to ensure signal consistency within the cluster.

10. The interferometric passive microwave imaging method based on array beamforming according to any one of claims 6-9, characterized in that, The P multi-beam fed reflector antennas (5) form a Y-shaped array.

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