ANTI-ALIASING ROTATING OFFSET GROUP ANTENNA

Description

BACKGROUND OF THE INVENTION Field of the Invention

[0001] The invention relates to the field of passive microwave remote sensing under aperture synthesis system, in particular, to an anti-aliasing rotation dislocation array antenna.Description of the Prior Art

[0002] Aperture synthesis microwave radiation detection, as a passive microwave remote sensing technology that obtains target characteristics by receiving microwave energy radiated from the observed scene, is different from the principle of traditional real-aperture radiation detection that directly performs power measurement and imaging. It obtains the high spatial resolution that cannot be achieved due to the limitations on the size of the real-aperture antenna by using large-aperture antennas for equivalent real-aperture detection of multiple small-unit antennas according to a certain array layout (T-type, Y-type, O-type, etc.). Through the interferometry between every two small-unit antennas, the spatial frequency domain of the radiation brightness temperature distribution in the field of view is sampled to obtain the visibility function, and then the brightness temperature images are reconstructed by performing mathematical operations on the visibility function.

[0003] The array layout has a significant impact on the performance of synthesis aperture radiation detection: the maximum length of the array determines the spatial resolution of the system imaging, the minimum unit spacing of the array determines the alias-free field of view of the system imaging, and the system sensitivity is also closely related to the number of array units and the arrangement of array unit intervals. The performance in sampling the visibility function of different array layouts is different, and the impact on the imaging performance of the system is also different. Therefore, the optimal design of the array layout must comprehensively consider various factors such as system performance indicators (resolution, sensitivity, field of view, etc.) and realizability of the hardware.

[0004] Documents CN 103 616 667 A, CN 101 841 084 A and CN 101 975 947 are background prior art documents.SUMMARY OF THE INVENTION

[0005] The technical objective of the invention is to provide an anti-aliasing rotation dislocation array antenna, so as to solve the technical problems of serious aliasing and low sensitivity.

[0006] In order to solve the problems, the invention uses the following technical solutions: An anti-aliasing rotation dislocation array antenna is provided, the anti-aliasing rotation dislocation array antenna being distributed in a staggered manner based on a coordinate system for determining a spatial position of the anti-aliasing rotation dislocation array antenna, the anti-aliasing rotation dislocation array antenna comprising a first sub-array antenna, a second sub-array antenna, a third sub-array antenna and a fourth sub-array antenna; the first sub-array antenna comprises N+1 antenna elements arranged at an equal interval Δu in a straight line; the second sub-array antenna comprises N antenna elements arranged at an equal interval Δu in a straight line; the third sub-array antenna comprises N antenna elements arranged at an equal interval Δu in a straight line; the fourth sub-array antenna comprises N antenna elements arranged at an equal interval Δu in a straight line; wherein the first sub-array antenna, the second sub-array antenna and the third sub-array antenna are in a U-shaped layout, and the second sub-array antenna is parallel to the third sub-array antenna; the first sub-array antenna is perpendicular to the second sub-array antenna and the third sub-array antenna respectively, and the first array antenna is arranged at 45° to a positive direction of an x-axis of the coordinate system and 45° to a positive direction of a y-axis of the coordinate system; the fourth sub-array antenna is parallel to the first sub-array antenna; distances between the antenna unit of the fourth sub-array at one end of the fourth sub-array antenna and the antenna unit at one end of the second sub-array antenna away from the first sub-array antenna, and between the antenna unit of the fourth sub-array antenna at one end of the fourth sub-array antenna and the antenna unit of the third sub-array antenna at one end of the third sub-array antenna away from the first sub-array antenna are 2 2 Δ u.

[0007] Specifically, distances between the antenna unit of the second sub-array antenna and the antenna unit of the first sub-array antenna close to one end of the second sub-array antenna and between the antenna unit of the third sub-array antenna and the antenna unit of the first sub-array antenna close to one end of the third sub-array antenna are Δu.

[0008] Specifically, a formula for the total number of sample points N V of a visibility function of the anti-aliasing rotation dislocation array antenna is as follows: N v = 8N 2< + 8N + 1.

[0009] Specifically, a visibility sampling grid pitch of the anti-aliasing rotation dislocation array antenna is 2 2 Δ u, with a minimum unit area of Δs = Δ u 2 2 .

[0010] Compared with the prior art, the invention has the following advantages and positive effects due to the adoption of the above technical solutions: Through the reasonable layout of the antenna units, an array antenna is obtained to achieve dislocated sampling of the visibility function, and the anti-aliasing rotation dislocation array antenna is obtained by rotating the array antenna by 45° to achieve dislocated sampling and rotation of the grids, so that the invention densifies the number of sampling points of the visibility function, and increases the detection area without aliasing and improve the detection sensitivity of the system, thereby widening the inversion imaging area and improving the clarity of the inversion image.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only used for the purpose of illustrating the preferred embodiments, and are not considered as a limitation to the invention. Fig. 1 is a view of an array layout of an anti-aliasing rotation dislocation array antenna according to the invention; Fig. 2 is a view of the sampling of a visibility function corresponding to the array layout based on Fig. 1; Fig. 3 is a view of a U-shaped array layout; Fig. 4 is a view of the sampling of a visibility function of a standard rectangular grid corresponding to the array layout based on Fig. 3; Fig. 5 is a view of a layout of adding a dislocated unit arm in the U-shaped array; Fig. 6 is a view of the sampling of a visibility function corresponding to the array layout based on Fig. 5; Fig. 7 is a view of an aliasing-free field of view of the new array layout acquired based on Fig. 1; Fig. 8 is a view of an aliasing-free field of view of a standard rectangular array acquired based on Fig. 3; Fig. 9 is an optical image of a certain scene; Fig. 10 is an inversion image acquired through the array layout of the invention based on Fig. 9; Fig. 11 is an inversion image acquired through the U-shaped array layout based on Fig. 9. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the specific implementation manners of the invention will be described below with reference to the accompanying drawings. Obviously, the drawings below are only some examples of the invention, and the ordinary artisans concerned may obtain other drawings on the basis of these drawings without making creative efforts and other embodiments.

[0013] In order to make the drawing concise, each drawing only schematically shows the parts related to the invention, and they do not represent the actual structure of the product. In addition, to make the drawings concise and easy to understand, in some drawings, only one of the components having the same structure or function is schematically shown, or only one of them is marked. Herein, "a" not only means "only one", but also means "more than one".

[0014] An anti-aliasing rotation dislocation array antenna proposed by the invention will be further described in combination with drawings and embodiments. Advantages and features of the invention will be apparent from the following description and claims.Embodiment 1

[0015] As shown in Fig. 1 and Fig.2, the embodiment provides an anti-aliasing rotation dislocation array antenna, and how it is obtained will now be described in detail.

[0016] As shown in Fig. 3, in the embodiment, first, several antenna units need to be placed in a coordinate system according to a U-shaped layout array, wherein the coordinate system is only for intuitively viewing the positional relationship of the antenna units, and has nothing to do with practical applications. The spacing 1 in the coordinate system represents 1*Δu. Specifically, the spacing between several adjacent antenna units is Δu, the U-shaped array includes three sides composed of antenna units, and each side is a straight line and two adjacent sides are perpendicular to each other. The U-shaped array is now divided into a first sub-array antenna, a second sub-array antenna and a third sub-array antenna, wherein the first sub-array antenna is a bottom side of the U-shaped array and includes N+1 antenna units, and the second sub-array antenna and the third sub-array antenna both include N antenna units, N being a positive integer. As shown in Fig. 3, combined with the coordinate system, x-coordinates of the antenna units of the second sub-array antenna are consistent and both are 0, and x-coordinates of the antenna units of the third sub-array antenna are consistent and both are 8. Based on the above U-shaped array layout, sampling of a standard rectangular grid is formed, a view of the sampling of the visibility function of the standard rectangular grid is shown in Fig. 4. A sampling spacing of the standard rectangular grid is Δu, a minimum unit area Δs = Δu 2< of a sampling plane of the visibility function is Δs = Δu 2< , with the total number of sample points of N v1 = 4N 2< + 4N + 1.

[0017] Next, as shown in Fig. 5, in the embodiment, the fourth sub-array antenna is added at an opening in the above U-shaped array layout; the number of the antenna units of the fourth sub-array antenna is N, the antenna units are arranged in a straight line with the spacing of Δu, and the fourth sub-array antenna is perpendicular to the first sub-array antenna. Combined with the coordinate system, coordinates of the antenna units at both ends of the fourth sub-array antenna are (0.5, 8.5), (7.5, 8.5) respectively, i.e., a distance between antenna unit at one end of the fourth sub-array antenna and the antenna unit of the nearest second sub-array antenna, and between the antenna unit at one end of the fourth sub-array antenna and the antenna unit of the third sub-array antenna is 2 2 Δ u. A dislocated grid sampling is formed by this arrangement, with a view of sampling of the visibility function shown in Fig. 6; the total number of samples of the visibility function is N v2 = 8N 2< + 8N + 1.

[0018] As shown in Fig. 1, finally, combined with the coordinate system, with the coordinate point (0, 0) as an origin of rotation, the above antenna units in the first sub-array antenna, the second sub-array antenna, the third sub-array antenna and the fourth sub-array antenna are rotated counterclockwise by 45°, then the anti-aliasing rotation dislocation array antenna of the embodiment is obtained. The rotation dislocated grid sampling is formed by this arrangement, with a specific view of sampling of the visibility function shown in Fig. 6; a sampling spacing of the visibility function is 2 2 Δ u, and the minimum unit area is Δs = Δ u 2 2 , with the total number of sample points of N v3 = N v2 = 8N 2< + 8N + 1.

[0019] The anti-aliasing capabilities of the U-shaped array layout and the array layout of the embodiment are now compared. According to the relationship between the synthesis aperture sampling interval Δl and the aliasing-free field of view, if a range of the aliasing-free field of view is |ξ min , ξ max |, a condition for aliasing-free in the field of view is Δ l ≤ 1 ξ max − ξ min , i.e., the smaller the sampling interval, the larger the range of aliasing-free. An interval of the U-shaped array layout is Δu, with corresponding aliasing-free field of view shown in Fig. 8; an interval of the rotation dislocation array layout of the embodiment is 2 2 Δ u, with corresponding aliasing-free field of view shown in Fig. 7; by comparison, the range of aliasing-free field of view is expanded by 2 times.

[0020] As shown in Figs. 9 to 11, in order to further illustrate the performance of the embodiment, the clarities of the inversion for the images of the same scene performed by the embodiment and the U-shaped array layout are described. In the field of microwave remote sensing, sensitivity is an important index to measure the effect of remote sensing, which reflects the minimum detectable degree of brightness temperature changes of each pixel in the image, and is expressed as the clarity of the inverted images, thereby providing beneficial help for subsequent extraction of required information from images. According to the relationship formula Δ T ∝ Δ s N v between the sensitivity of synthesis aperture and the array layout, the sensitivity ΔT is proportional to the product of the square root N v of the minimum unit area Δs of the visibility sampling plane and the number of sample points of the visibility function. In the U-shaped array layout, the minimum unit area is Δs = Δu 2< , and the total number of sample points is N v1 = 4N 2< + 4N + 1; in the embodiment, the minimum unit area is Δs = Δ u 2 2 , and the total number of sample points is N v3 = 8N 2< + 8N + 1; by comparison and calculation, the sensitivity of the array layout of the embodiment is 2 times higher than that of the U-shaped array layout; the smaller the sensitivity value is, the more sensitive it is. MATLAB software is used for inversion simulation. Fig. 9 is the optical image of the scene, Fig. 11 is the inversion image of the U-shaped array layout using inverse Fourier transform, and Fig. 10 is an inversion image based on the array layout of the embodiment using inverse Fourier transform. It can be seen that the inversion image based on the new layout of the embodiment reflects more detailed information, the outline is clearer, and the performance is better.

[0021] As a supplementary note, if the alias-free field of view required by the system detection is certain, in the dislocation layout corresponding to the embodiment, the spacing between antenna units is 2 times that of the U-shaped layout. Under the condition that the spatial resolution (i.e., the maximum length of the sampling plane of the visibility function) remains unchanged, the new layout may greatly reduce the number of units, and reduce the design and engineering requirements for unit antennas.

[0022] The implementations of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above implementations.

Claims

1. An anti-aliasing rotation dislocation array antenna, the anti-aliasing rotation dislocation array antenna being distributed in a staggered manner based on a coordinate system for determining a spatial position of the anti-aliasing rotation dislocation array antenna, the anti-aliasing rotation dislocation array antenna comprising a first sub-array antenna, a second sub-array antenna, a third sub-array antenna, and a fourth sub-array antenna; the first sub-array antenna comprises N+1 antenna units arranged at an equal interval Δu in a straight line, N being a positive integer; the second sub-array antenna comprises N antenna units arranged at an equal interval Δu in a straight line; the third sub-array antenna comprises N antenna units arranged at an equal interval Δu in a straight line; the fourth sub-array antenna comprises N antenna units arranged at an equal interval Δu in a straight line; wherein the first sub-array antenna, the second sub-array antenna, and the third sub-array antenna are in a U-shaped layout, and the second sub-array antenna is parallel to the third sub-array antenna; the first sub-array antenna is perpendicular to the second sub-array antenna and the third sub-array antenna respectively, and the first array antenna is arranged at 45° to a positive direction of an x-axis of the coordinate system and 45° to a positive direction of a y-axis of the coordinate system; the fourth sub-array antenna is parallel to the first sub-array antenna; distances between the antenna unit of the fourth sub-array at one end of the fourth sub-array antenna and the antenna unit of the second sub-array antenna at one end of the second sub-array antenna away from the first sub-array antenna, and between the antenna unit of the fourth sub-array antenna at one end of the fourth sub-array antenna and the antenna unit of the third sub-array antenna at one end of the third sub-array antenna away from the first sub-array antenna are 2 2 Δ u.

2. The anti-aliasing rotation dislocation array antenna according to claim 1, wherein distances between the antenna unit of the second sub-array antenna and the antenna unit of the first sub-array antenna close to one end of the second sub-array antenna and between the antenna unit of the third sub-array antenna and the antenna unit of the first sub-array antenna close to one end of the third sub-array antenna are Δu.

3. The anti-aliasing rotation dislocation array antenna according to claim 1, wherein a formula for the total number of sample points NV of a visibility function of the array layout is as follows: Nv = 8N2 + 8N + 1.

4. The anti-aliasing rotation dislocation array antenna according to claim 1, wherein a visibility sampling grid pitch of the anti-aliasing rotation dislocation array antenna is 2 2 Δ u, with a minimum unit area of Δs = Δ u 2 2 .