MMIC element distribution structure for near-field two-dimensional MIMO array radar imaging and the array

Abstract

The present invention is an MMIC array element distribution structure and array for near-field two-dimensional MIMO array radar imaging, belonging to the technical field of MIMO radar arrays. The MIMO array of the present invention is composed of a plurality of MMIC subarrays; the MMIC array element distribution structure is designed based on comprehensive aperture imaging, and under the conditions of a given two-dimensional aperture range and the number of MMIC units, the 2D beam width, maximum grating lobe level and eccentricity are used as evaluation indicators of the radar beam, and the redundancy in comprehensive aperture imaging, the number and position of UV distribution missing points are used as array design indicators to optimize the array element structure of each MMIC unit and the position of each MMIC unit. An embodiment of the present invention provides a 4-transmit and 4-receive antenna MIMO subarray and array structure. The array element distribution structure designed by the present invention has better imaging performance than the sparse arrangement with equal spacing, can improve the target imaging accuracy, and significantly reduce the grating lobe level in the imaging results.

Description

Technical Field

[0001] This invention belongs to the field of multiple-instance multiple-receiver (MIMO) radar array technology, and specifically relates to an array element distribution structure and the array for near-field two-dimensional MIMO array radar imaging. Background Technology

[0002] In array radar systems, multiple-transmitter-multiple-receiver (MIMO) architectures are typically used to reduce the number of antennas and transceiver modules, thereby lowering system cost and complexity. Two-dimensional MIMO array radar systems employ electronic scanning instead of mechanical scanning, offering high efficiency and spatial three-dimensional imaging capabilities, and are widely used in surveillance, security, and medical imaging fields.

[0003] For radar imaging, to obtain high-precision imaging results without grating lobes, the array needs to have a wide aperture and narrow element spacing. The main function of the antenna elements is to spatially sample the received echo signal. Because MIMO reduces the number of elements while separating the transmit and receive elements, the virtual element distribution will have a certain degree of sparsity, resulting in grating lobe problems in the imaging results. The main goal of a reasonable array design is to improve imaging accuracy by designing the array arrangement, under the same hardware configuration, for example, by sharpening the main lobe and suppressing side lobes and grating lobes.

[0004] There are two main existing design methods for two-dimensional MIMO radar arrays:

[0005] The first type is direct array at the single board level. Although direct array at the single board level offers flexible array arrangement, this distributed structure results in higher hardware complexity for the RF system, which is not conducive to achieving large-scale array deployment and has high manufacturing costs.

[0006] The second method involves a two-dimensional array based on subarrays constructed from monolithic microwave / millimeter-wave integrated circuit (MMIC) chips. Compared to direct arraying at the single-board level, this method maintains low hardware complexity, balances the scalability and low cost of two-dimensional MIMO arrays, and leverages the advantages of MMIC design in terms of ease of design and adjustment. Currently, with the development of MMIC technology, two-dimensional arraying methods based on MMICs are increasingly used in MIMO radars to expand array size.

[0007] When designing two-dimensional MIMO arrays, the ideal solution is to ensure that all virtual array elements uniformly cover the aperture plane, with almost no redundancy. However, in practical MMIC design, the fixed distribution of MMIC subarray elements, along with the definite physical size and boundaries of the MMIC subarrays, limits the flexibility in configuring virtual array elements, thus restricting array design. Therefore, how to arrange MMIC subarrays in a two-dimensional plane to maximize virtual array element coverage of the aperture plane and effectively suppress horizontal grating lobes in the imaging results is crucial for improving imaging accuracy and is an essential step towards the practical application and widespread adoption of MMIC large-aperture array design technology. Summary of the Invention

[0008] To address the shortcomings of the existing technologies and the need to improve the imaging accuracy of near-field two-dimensional MIMO array radar, this invention provides an array element distribution structure and the array itself for near-field two-dimensional MIMO array radar imaging. By designing a two-dimensional planar layout of multiple MMIC subarrays based on integrated aperture imaging processing, an array element distribution structure for near-field two-dimensional MIMO array imaging is created. Given a two-dimensional aperture width and the number of array elements, this two-dimensional array structure can improve target imaging accuracy and significantly reduce grating lobe levels.

[0009] This invention provides an MMIC element distribution structure for near-field two-dimensional MIMO array radar imaging. It is designed based on synthetic aperture imaging. Under the conditions of a pre-given aperture range of the two-dimensional MIMO array and the number of MMIC elements N, N MMIC elements are arranged to generate a two-dimensional MIMO array; wherein, the element structure of the N MMIC elements is the same.

[0010] First, determine the array element structure of each MMIC unit. Assume that the number of receiving array elements and transmitting array elements in the MMIC unit is k, and the minimum spacing between adjacent transmitting array elements and adjacent receiving array elements is λ / 2, where λ is the wavelength. Calculate the index parameters of the radar beam and adjust the array element structure of the MMIC unit so that the equivalent virtual array elements in the MMIC unit subarray have as few gaps as possible and do not exceed the given aperture range.

[0011] The layout of N MMIC units is as follows: On the planar space where the two-dimensional MIMO array needs to be laid out, the row and column references for the positions of the MMIC units are set with vertical spacing V and horizontal spacing H as the spacing. The first transmitting element of the MMIC unit is taken as the center element of the unit, and the position of the center element represents the position of the MMIC unit. Initially, the N MMIC units are arranged in a square array, and the position of each MMIC unit relative to the row and column references is determined. Then, for the current distribution structure of the MMIC unit array, the spatial frequency domain index is calculated. By adjusting the positions of the N MMIC units in the planar space of the layout, the layout result with the optimal spatial frequency domain index is obtained.

[0012] The radar beam's specifications include 2D beamwidth, maximum grating lobe level (MSLL), and eccentricity (Ecc). The 2D beamwidth is expressed as a 3dB beamwidth, approximating the radar beam illumination area with an ellipse. The maximum grating lobe level represents the intensity of the grating lobe's radiation relative to the main lobe. The eccentricity is a measure of the ellipse's flatness; the closer the eccentricity is to 1, the flatter the ellipse.

[0013] The spatial frequency domain indicators include redundancy, the number of missing points in the UV distribution, and the location of these missing points. Missing points in the UV distribution refer to regions where effective interference fringes cannot be obtained in the interferometer.

[0014] The N MMIC units refer to 16 MMIC units, with the first receiving element of each MMIC unit positioned at the center of the unit; the vertical spacing V is set to 8mm, the horizontal spacing H is set to 10mm, 5 row references and 4 column references are set, and the 16 MMIC unit arrays are distributed in a rectangular range to obtain the layout with optimal spatial frequency domain performance.

[0015] Furthermore, the present invention implements a two-dimensional MIMO array, which is obtained by splicing and expanding the distribution structure of K*K MMIC array elements, where K is a positive integer.

[0016] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0017] (1) The two-dimensional MIMO array designed in this invention takes advantage of the low cost of MMIC two-dimensional array, and can be reasonably arranged in a limited space to greatly improve the imaging accuracy and achieve high accuracy in azimuth and elevation.

[0018] (2) The MMIC element distribution structure designed in this invention adopts the integrated aperture imaging method. When arranging the elements, based on the distribution characteristics of the transmitting and receiving elements of each MMIC subarray, the number of missing values ​​of the virtual element baseline is minimized, effectively reducing the grating lobe level in the imaging results. For the same number of MMICs, a low-redundancy two-dimensional element distribution structure is constructed to minimize the missing values ​​of the UV distribution baseline in the array layout. By rationally arranging the MMICs, while maintaining low complexity of the hardware circuit, the imaging accuracy of the two-dimensional sparse array radar is improved, and the grating lobe level in the sparse array imaging results is reduced. This makes the designed array suitable for near-field imaging and can effectively reduce grating lobes under sparse MIMO array configuration. The array designed under this method is more suitable for the array layout scheme of MMICs.

[0019] (3) The MMIC array element distribution structure and two-dimensional MIMO array designed in this invention are based on the multi-MMIC two-dimensional planar array of integrated aperture imaging processing. The array designed has the characteristics of high precision and low grid lobe for imaging. It is an effective and universal method for two-dimensional sparse array under the condition of limited array element position. Attached Figure Description

[0020] Figure 1 This is an antenna distribution diagram of the MMIC subarray used in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of an MMIC array implemented in an embodiment of the present invention;

[0022] Figure 3 This is a diagram showing the distribution structure of the sparse array elements in an embodiment of the present invention.

[0023] Figure 4 This is a UV distribution diagram of sparse array elements according to an embodiment of the present invention;

[0024] Figure 5 For comparison, the antenna beam pattern of the two-dimensional array is shown in the diagram; where (1) is the antenna beam pattern of the existing sparse array with equal spacing, and (2) is the antenna beam pattern of the sparse array in the embodiment of the present invention.

[0025] Figure 6 For comparison, two-dimensional imaging results of point targets are shown; where (1) is the existing sparse array imaging result with equal spacing, and (2) is the imaging result of the sparse array in the embodiment of the present invention.

[0026] Figure 7 This is a diagram showing the distribution structure of the extended array formed by sparse array in an embodiment of the present invention;

[0027] Figure 8 The two-dimensional imaging results of the extended array formed by the sparse array in the embodiment of the present invention are shown below; where (1) is the imaging result of the point target; and (2) is the imaging result of the 5x5 point array. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. Here, the illustrative embodiments and descriptions of this invention are used to explain the invention, but are not intended to limit the invention.

[0029] Array radar systems typically utilize MIMO (Multi-Input Multiple-Output) to reduce the number of antennas and transceiver modules, thereby lowering system cost and complexity. For radar imaging, obtaining high-precision imaging results without grating lobes requires an array with a wide aperture and narrow element spacing. Currently, with the development of MMIC (Multi-Input Multiple-Output) technology, MIMO radar increasingly uses MMIC-based two-dimensional array methods. In near-field two-dimensional MIMO array radar imaging, the element distribution structure determines the level and position of grating lobes in the imaging result. Suppressing grating lobes caused by sparsity is an effective way to improve imaging performance based on MMIC layout. How to arrange MMICs in a two-dimensional plane to ensure that virtual elements cover the aperture plane as much as possible, effectively suppressing the level of grating lobes in the imaging result, is crucial for improving imaging accuracy and is a problem that needs to be solved in array design. To address this problem, this invention designs the array based on synthetic aperture imaging, and uses this to design performance indicators and the final imaging processing method.

[0030] Synthetic aperture imaging utilizes visibility function data obtained from array radar systems to image the target's field of view through specific mathematical operations. The basic principle of synthetic aperture imaging is to correlate each small antenna element constituting the antenna array pairwise. The correlation result is equivalent to a larger virtual aperture in the spatial frequency domain, further enabling spatial frequency domain measurements of the space to be imaged. The spatial frequency domain coordinates are represented by (u, v), and are called the UV distribution.

[0031] Under near-field conditions, the spatial brightness temperature distribution map and the visibility function no longer satisfy the Fourier transform relationship. Based on the relationship between synthetic aperture near-field imaging and near-field beamforming, by controlling the weight vector in near-field beamforming, the synthesized beam is focused on a specified location in space to obtain an estimate of the radiation source power at that location, i.e., the brightness temperature. Then, the synthesized beam is focused point-by-point on all specified locations in space to obtain the brightness temperature distribution of a specified region in space, thus completing the inversion of the millimeter-wave image.

[0032] The basic unit of synthetic aperture imaging is a binary antenna array. Its basic function is to perform complex correlation operations on the output results of all array radar baselines. The result of the correlation operation can be regarded as the Fourier transform of a spatial function, and the synthetic aperture image can be obtained by means of two-dimensional fast Fourier transform.

[0033] The array radar baseline is defined as the line connecting the phase centers of two antenna elements at different spatial locations.

[0034] This invention selects 2D beamwidth, maximum grating level and eccentricity as evaluation indicators for radar beams, and uses redundancy, number of missing points in UV distribution and location of missing points as indicators in array design. Based on synthetic aperture imaging, an array structure for near-field two-dimensional MIMO array radar imaging based on MMIC is designed. This structure has better imaging performance than sparsely arranged arrays with equal spacing.

[0035] The 2D beamwidth is represented by a 3dB beamwidth, and the radar beam illumination area is approximated by an ellipse. The major and minor axes are represented by BW respectively. max and BW min 2D beamwidth (BW) DoA Represented as:

[0036]

[0037] The maximum grating lobe level (MSLL) represents the radiation level of the grating lobe relative to the intensity of the main lobe, i.e., the degree of attenuation of the grating lobe's radiation intensity relative to the main lobe. The maximum grating lobe level (MSLL) is expressed as:

[0038] MSLL = 10 × log(R) msl / R max )

[0039] Among them, R max It is the amplitude of the main lobe, R. msl That is the amplitude of the first grating lobe.

[0040] The eccentricity is a measure of an ellipse, indicating its flatness. The closer the eccentricity is to 1, the flatter the ellipse. In radar beams, the eccentricity Ecc is expressed as:

[0041]

[0042] As described above, the MMIC element distribution structure for near-field two-dimensional MIMO array radar imaging provided by this invention is designed based on synthetic aperture imaging. The distribution of spatial sampling points affects the imaging quality and can reflect the effectiveness of the design scheme from the UV space. Therefore, it is necessary to optimize the spatial frequency domain indicators of the array layout for synthetic aperture imaging processing.

[0043] The spatial frequency domain indicators include: redundancy, number of missing points in the UV distribution, and location of missing points.

[0044] The redundancy R is defined as follows:

[0045] R = S id / S re

[0046] Among them, S id S represents the ideal number of sampling points.re This represents the actual number of sampling points.

[0047] The arrangement of two-dimensional MIMO arrays inevitably introduces missing points in the UV distribution of the virtual array elements. These missing points correspond to certain spatial frequencies in the UV plane that cannot be obtained by the imaging system; in other words, missing points refer to regions where effective interference fringes cannot be obtained in the interferometer. These missing points lead to high-level grating lobes in the imaging system and degrade image quality. The array element distribution structure with equal spacing and sparse arrangement has more missing values ​​because the baseline is mostly redundant, the UV distribution has a large number of gaps, and the number of spatial sampling points is insufficient. Therefore, the imaging resolution decreases, the grating lobe level increases, and the imaging performance is limited.

[0048] Therefore, when designing the array element arrangement for synthetic aperture imaging, this invention, based on the distribution characteristics of the transmitting and receiving elements of each MMIC subarray, aims to minimize gaps in the equivalent virtual array elements, i.e., to reduce the number of missing values ​​in the virtual array element baseline, effectively lowering the grating lobe level in the imaging results. For the same number of MMIC elements, a low-redundancy two-dimensional array element distribution structure should be constructed to achieve optimal spatial frequency domain performance, i.e., to minimize the number of missing baseline values ​​in the UV distribution obtained by the array layout.

[0049] The position of each MMIC element is represented by the position of its central element. In this embodiment, the central element is the first transmitting element of each MMIC element. The spacing between each transmitting and receiving element in the MMIC subarray is λ / 2, where λ is the wavelength. The distribution structure of the MMIC elements is independent of the type of antenna used for the transmitting and receiving elements. The transmitting and receiving elements can be, but are not limited to, horn antennas.

[0050] This invention relates to near-field two-dimensional MIMO array radar imaging. The array includes MMIC elements and a two-dimensional MMIC arrangement structure using MMICs. The arrangement structure includes an MMIC antenna design structure and an MMIC element arrangement structure. In the embodiments of this invention, the structure of each MMIC subarray in the two-dimensional MIMO radar array is identical. Assume that the aperture range and the number of MMIC elements N = 16 of the predetermined two-dimensional MIMO array.

[0051] To ensure both azimuth and elevation imaging performance, the array implemented in this invention utilizes 16 MMICs arranged in a 4x4 distribution structure. Each MMIC's transceiver antenna design includes 4 transmit and 4 receive antennas. Specifically, the 4 receive antennas are arranged in a linear array at equal intervals on the same side, while the 4 transmit antennas are arranged in an L-shaped array with one antenna close to the chip edge and three antennas equally spaced vertically.

[0052] like Figure 1As shown, the subarray structure of the MMIC unit designed in this embodiment of the invention, with the first receiving antenna as the reference, has receiving antennas Rx1 to Rx4 arranged horizontally at equal intervals, with a spacing of R1 between each adjacent receiving antenna. The first transmitting antenna Tx1 is located to the lower right of the first receiving antenna Rx1, with a horizontal spacing of D1 and a vertical spacing of D2 between it and the first transmitting antenna. The second, third, and fourth transmitting antennas Tx2 to Tx4 are arranged vertically at equal intervals. The bottommost second transmitting antenna Tx2 is on the same horizontal line as the first transmitting antenna Tx1, and both are vertically distanced from the first receiving antenna Rx1 by D2. The horizontal distance between the second transmitting antenna Tx2 and the first receiving antenna Rx1 is D3. The adjacent vertical spacing of the second, third, and fourth receiving antennas is D4. The minimum spacing between adjacent array elements is set to half a wavelength. The spacing is set to minimize gaps in the equivalent virtual array elements within the subarray, while also not exceeding the aperture range of the MMIC.

[0053] This invention utilizes an array of 16 micro-microphones (MMICs). The center of each MMIC subarray is defined by the position of its first receiving element. Five row references and four column references are established with vertical spacing V and horizontal spacing H. The position of each MMIC is given relative to these row and column references. Each row and column reference line is shown as a dashed line. In this embodiment, the vertical spacing V is 8 mm, and the horizontal spacing H is 10 mm. The design uses the UV distribution corresponding to the virtual array elements as an evaluation metric, comparing baseline redundancy, the number of missing points, and their positions to design an ideal array structure. The design adjusts the positions of the MMIC subarrays based on the baseline metrics to optimize the baseline and achieve better imaging results. By adjusting the positions of each MMIC, spatial frequency domain metrics are calculated for the MMIC unit array distribution structure to obtain the optimal layout result. The optimized distribution positions of each MMIC unit in the array obtained in this embodiment are shown below. Figure 2 As shown.

[0054] like Figure 2As shown, the MMIC array of this embodiment is numbered in order from left to right and from top to bottom. The MMIC at the top of the leftmost column is designated as number 1. MMIC 1 is located 2mm below the reference line of row 1 and 8mm to the right of the reference line of column 1. MMIC 2 is located on the reference line of row 2 and 8mm to the right of the reference line of column 2. MMIC 3 is located 2mm below the reference line of row 1 and 2mm to the right of the reference line of column 3. MMIC 4 is located 4mm below the reference line of row 1 and 4mm to the right of the reference line of column 4. MMIC 5 is located 4mm below the reference line of row 2 and on the reference line of column 2. MMIC 6 is located 4mm below the reference line of row 3 and 6mm to the right of the reference line of column 2. MMIC 7 is located 6mm below the reference line of row 2 and 6mm to the right of the reference line of column 3. MMIC 8 is located 4mm below the reference line of row 2 and 4mm to the right of the reference line of column 4. The MMIC for code 9 is located 2mm below the reference in row 3 and 6mm to the right of the reference in column 1. The MMIC for code 10 is located 4mm below the reference in row 4 and 2mm to the left of the reference in column 2. The MMIC for code 11 is located 4mm below the reference in row 3 and 4mm to the left of the reference in column 3. The MMIC for code 12 is located 6mm below the reference in row 3 and 2mm to the left of the reference in column 4. The MMIC for code 13 is located 1mm below the reference in row 5 and on the reference in column 2. The MMIC for code 14 is on the reference in row 5 and on the reference in column 3. The MMIC for code 15 is on the reference in row 5 and 2mm to the left of the reference in column 4. The MMIC for code 16 is located 4mm below the reference in row 4 and 4mm to the right of the reference in column 4.

[0055] like Figure 3 As shown, the left side displays Figure 2 The image shows the element distribution of a 64*64 structure formed by the MMIC array, with the corresponding 256 equivalent virtual elements shown on the right. Figure 4 The image shown is a UV distribution diagram of the array elements calculated by the integrated aperture algorithm according to the embodiment of the present invention. Compared with uniform arrangement, the UV distribution has lower redundancy and fewer missing points.

[0056] Furthermore, the two-dimensional MIMO array implemented in this embodiment of the invention is a combination of multiple optimized arrays such as... Figure 2 The MMIC array shown is obtained by splicing and expanding it, with the number of rows and columns being the same.

[0057] Comparative Experiment 1:

[0058] In Comparative Experiment 1, two array element distribution structures were used: one with equal spacing and sparse array elements, and the other with the array element distribution structure described in this invention. Under the same simulation parameters and using the same imaging method, the UV distribution maps of the virtual array elements and baselines in the first quadrant were plotted. Compared to a directly equally spaced MMIC layout, the distribution structure of this invention has fewer default baselines. Therefore, its theoretical grating lobe level is lower.

[0059] contrast Figure 5 The antenna array patterns shown in the two examples demonstrate that the distributed structure designed in this invention achieves better beamforming. In the equidistant sparse array design, the beamwidth is 3.4928°, the maximum grating lobe level is -1.5dB, and the eccentricity is 0.8992. In contrast, the beamwidth using the embodiment of this invention is 1.88°, the maximum grating lobe level is -1.5dB, and the eccentricity is 0.5664. This comparison shows that the redundancy of the example of this invention is reduced by 69.34%.

[0060] Comparative Experiment 2:

[0061] In Experiment 2, both arrays were used to image point targets, employing the same imaging method. The experimental waveform was LFMCW at a frequency of 75 GHz, with an SNR of 5 dB. The ideal point target was 8 m from the array center. The imaging results are as follows: Figure 6 As shown, (1) is the imaging result of the existing sparse array with equal spacing, and (2) is the imaging result of the sparse array in the embodiment of the present invention. Experimental results show that the grating lobe level of the array element structure designed by the present invention is lower than that of the sparse array with equal spacing. In the embodiment of the present invention, the azimuth resolution is 1.61° and the elevation resolution is 1.54°. The grating lobe positions are distributed as follows: azimuth ±2.6° with an amplitude of -6.70dB; azimuth ±4.9° with an amplitude of -7.49dB; azimuth ±6.7° with an amplitude of -7.72dB. In the elevation direction, the grating lobe positions are ±3.2° with an amplitude of -7.67dB; ±6.9° with an amplitude of -7.47dB; and ±10° with an amplitude of -6.47dB.

[0062] The four arrays are combined to form an extended array, the distribution structure of which is as follows: Figure 7 As shown. This extended array was used to image point targets and array targets respectively. The experimental waveform was LFMCW, with a frequency range of 75 GHz, SNR = 5 dB, and the ideal point target distance was 8 m from the array center. Twenty-five equally spaced point targets were covered in the azimuth and elevation angle range (-10°, 10°). The two-dimensional imaging results of the extended array constructed in this embodiment are shown below. Figure 8 As shown, based on the imaging results, the azimuth resolution of the extended array is calculated to be 0.83°, and the elevation resolution is 0.97°.

[0063] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not limiting. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the scope of protection of the present invention.

Claims

1. A MMIC element distribution structure for near-field two-dimensional MIMO array radar imaging, based on the principle of synthetic aperture imaging, wherein, given the aperture range of the two-dimensional MIMO array and the number N of MMIC elements, N monolithic microwave / millimeter-wave integrated circuit MMIC elements are arranged to generate a two-dimensional MIMO array; characterized in that, The arrangement of the N MMIC units is as follows: The array element structure of each MMIC unit is determined. The number of receiving and transmitting elements in each MMIC unit is k, and the minimum spacing between adjacent transmitting and receiving elements is λ / 2, where λ is the wavelength. The array element structures of the N MMIC units are identical. The radar beam parameters are calculated, and the array element structure of the MMIC units is adjusted to minimize gaps in the equivalent virtual array elements within the MMIC unit subarray and to ensure that the aperture does not exceed a given range. The radar beam parameters include 2D beamwidth, maximum grating level, and eccentricity. An ellipse is used to approximate the radar beam illumination area; the 2D beamwidth is represented by a 3dB beamwidth; the maximum grating level is the intensity of the grating lobe's radiation relative to the main lobe; and the eccentricity is a metric of the ellipse. Determine the layout of N MMIC units: On the planar space where the two-dimensional MIMO array needs to be laid out, set the row and column references for the positions of the MMIC units with vertical spacing V and horizontal spacing H as the spacing. Take the first transmitting element of the MMIC unit as the center element of the unit, and use the position of the center element to represent the position of the MMIC unit. Initially, arrange the N MMIC units in a square array and determine the position of each MMIC unit relative to the row and column references. Then, calculate the spatial frequency domain index for the current distribution structure of the MMIC unit array. Adjust the positions of the N MMIC units on the planar space of the layout to obtain the layout result with the optimal spatial frequency domain index. The spatial frequency domain index includes redundancy, the number of missing points in the UV distribution, and the location of missing points. Among them, redundancy is the ratio of the number of ideal sampling points to the number of actual sampling points. The missing points refer to the areas where effective interference fringes cannot be obtained in the interferometer.

2. The MMIC element distribution structure as described in claim 1, characterized in that, The array element structure of the MMIC unit is 4 transmit and 4 receive antennas. The layout is as follows: the 4 receive antennas are arranged in a linear array at equal distances on the same side, and the 4 transmit antennas are arranged in an L-shaped array with 1 antenna close to the edge of the chip and 3 antennas distributed vertically at equal distances. With the first receiving antenna as the reference, the receiving antennas are arranged horizontally at equal intervals; the first transmitting antenna is located to the lower right of the first receiving antenna; the second, third, and fourth transmitting antennas are arranged vertically at equal intervals, and the second transmitting antenna at the bottom is on the same horizontal line as the first transmitting antenna.

3. The MMIC element distribution structure as described in claim 1, characterized in that, The vertical spacing V is set to 8mm, and the horizontal spacing H is set to 10mm.

4. The MMIC element distribution structure as described in claim 3, characterized in that, The MMIC unit consists of 16 elements. The center of each MMIC unit is the position of the first receiving element. Five row references and four column references are set with vertical spacing V and horizontal spacing H as the spacing. The 16 MMIC unit arrays are distributed in a rectangular range to obtain the layout with the optimal spatial frequency domain index.

5. A two-dimensional MIMO array, characterized in that, The distribution structure of MMIC array elements as described in claim 1, 2, 3, or 4 is obtained by splicing and expanding K*K, where K is a positive integer.

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