Multiple-input multiple-output sparse antenna
Technical Field
The invention relates to the technical field of antenna arrays, in particular to a multiple-input multiple-output sparse antenna.
Background
In order to meet the requirements of low-cost, modularization and sparsity development of the antenna array, the reasonable antenna arrangement method is very valuable. Especially, the millimeter wave radar antenna has more unit channels and high integration level, and the arrangement method greatly determines the cost and the processing difficulty of the radar antenna. At present, an optimization algorithm such as a genetic algorithm is adopted to sparsify an antenna array according to a target directional diagram, the universality of the optimization algorithm-based sparsification method is poor, different target directional diagrams need to be optimized and calculated once, even if the same target directional diagram is adopted, results obtained by multiple times of optimization are different, and the requirement of modular array arrangement is difficult to meet.
In view of the above-mentioned drawbacks, the inventors of the present invention have finally obtained the present invention through a long period of research and practice.
Disclosure of Invention
In order to solve the technical defects, the technical scheme adopted by the invention is to provide a mimo sparse antenna, which comprises a plurality of mimo antenna sub-arrays, wherein the mimo antenna sub-arrays are sparsely arranged, each mimo antenna sub-array comprises 4 non-sparsely arranged transmitting sub-arrays and 1 sparsely arranged receiving sub-array, a gap is arranged between each transmitting sub-array and each receiving sub-array, and a periodically distributed planar artificial magnetic conductor structure is arranged in each gap.
Preferably, the mimo antenna subarray is entirely rectangular, 4 of the transmitting subarrays are respectively arranged at four corners of the mimo antenna subarray, the transmitting antenna units in the transmitting subarray are distributed in a rectangular grid, the array surface of the transmitting subarray is rectangular, the receiving subarray is arranged in the middle of the mimo antenna subarray, the receiving antenna units in the receiving subarray are distributed in a rectangular grid, and the array surface of the receiving subarray is cross-shaped.
Preferably, the transmitting subarrays are non-sparsely arranged, and the horizontal unit spacing and the vertical unit spacing of the transmitting antenna units need to satisfy a constraint relation of a corresponding scanning angle of the phased array to the antenna unit spacing:
d is the horizontal unit interval of the transmitting subarray, lambda is the working wavelength of the antenna, and theta is the scanning angle of the transmitting subarray in the horizontal direction;
wherein d 'is the vertical unit interval of the emission subarray, λ is the antenna working wavelength, and θ' is the scanning angle of the emission subarray in the vertical direction.
Preferably, the number of units required by the transmitting subarray and the receiving subarray in the horizontal direction and the vertical direction satisfies a formula:
wherein N is1The number of transmitting antenna units required for the transmitting subarray in the horizontal direction, λ is the antenna operating wavelength, B1The beam width required for the transmitting subarray in the horizontal direction, d1The unit interval of the transmitting subarray in the horizontal direction is obtained;
wherein N is2The number of receiving antenna units required for the receiving subarray in the horizontal direction, λ is the antenna operating wavelength, B2The required beam width in the horizontal direction for the receiving sub-array, d2The unit spacing of the receiving subarrays in the horizontal direction;
wherein N is3The number of transmitting antenna units required for the transmitting subarray in the vertical direction, λ is the antenna operating wavelength, B3The beam width required for the transmitting subarray in the horizontal direction, d3Is that it isThe unit interval of the emission subarray in the vertical direction;
wherein N is4The number of receiving antenna units required for the receiving subarray in the horizontal direction, λ is the antenna operating wavelength, B4The required beam width in the horizontal direction for the receiving sub-array, d4And the unit spacing of the receiving subarrays in the horizontal direction.
Preferably, the horizontal unit spacing of the receiving subarray is an integral multiple of the horizontal unit spacing 2-4 of the transmitting subarray, and the vertical unit spacing of the receiving subarray is an integral multiple of the vertical unit spacing 2-4 of the transmitting subarray.
Preferably, the number of elements of the receiving subarray in the horizontal direction is determined by the beam width of the receiving subarray in the horizontal direction, and the number of elements of the receiving subarray in the vertical direction is determined by the beam width of the receiving subarray in the vertical direction.
Preferably, the gap between the transmitting subarray and the receiving subarray is in an L shape;
the width of the vertical section of the gap is 2-4 times of the horizontal unit interval of the transmitting subarray, and the height of the vertical section of the gap is equal to the product of the vertical unit interval of the transmitting subarray and the number of units in the vertical direction of the transmitting subarray;
the width of the horizontal section gap of the gap is 2-4 times of the vertical unit interval of the transmitting subarray, and the length of the horizontal unit interval of the transmitting subarray is equal to the sum of the horizontal unit interval of the transmitting subarray multiplied by the number of units in the horizontal direction of the transmitting subarray and the width of the vertical section gap of the gap.
Preferably, the working bandwidth of the planar artificial magnetic conductor structure is consistent with the working bandwidth of the mimo sparse antenna.
Preferably, the mimo antenna subarray in the mimo sparse antenna has a horizontal element spacing 2 times as long as the mimo antenna subarray in the horizontal direction, and a vertical element spacing 2 times as long as the mimo antenna subarray in the vertical direction.
Preferably, the length of the mimo antenna subarray in the horizontal direction is the number of units of the receiving subarray in the horizontal direction multiplied by the horizontal unit spacing of the receiving subarray; the length of the MIMO antenna subarray in the vertical direction is the number of units of the receiving subarray in the vertical direction multiplied by the vertical unit interval of the receiving subarray.
Compared with the prior art, the invention has the beneficial effects that: the sparse array distribution method provided by the invention is simple and easy to implement, and optimization calculation by an optimization algorithm is not needed. The antenna array is composed of a plurality of identical transmitting sub-arrays and receiving sub-arrays, so that the antenna array has good expansibility. Compared with a receiving subarray array surface, the transmitting subarray array is smaller in size and easier to process and implement, modular design can be carried out on the transmitting subarray array and the receiving subarray array, complexity of antenna array processing can be obviously reduced, and cost can be reduced. By adopting the array arrangement method, the directional pattern grating lobe caused by sparse array arrangement can be effectively inhibited, and the method is particularly suitable for millimeter wave radar antennas, such as millimeter wave automobile radars, human body security check instruments and the like, and has higher engineering application value.
Drawings
Fig. 1 is a structural view of the mimo antenna subarray;
FIG. 2 is a vertical directional diagram of a single transmit subarray according to an embodiment;
FIG. 3 is a vertical composite directional diagram of four transmit sub-arrays according to an embodiment;
FIG. 4 is a vertical directional diagram of a single receive subarray according to an embodiment;
FIG. 5 is a diagram illustrating a vertical composite pattern of a single transmit subarray and a single receive subarray according to an embodiment;
FIG. 6 is a schematic diagram of an embodiment in which four transmit sub-arrays are combined with a single receive sub-array to form a vertical pattern;
FIG. 7 is a horizontal directional diagram of a single transmit subarray according to one embodiment;
FIG. 8 is a horizontal composite directional diagram of four transmit sub-arrays according to one embodiment;
FIG. 9 is a horizontal directional diagram of a single receiving subarray according to one embodiment;
FIG. 10 is a horizontal composite pattern of a single transmit subarray and a single receive subarray according to one embodiment;
FIG. 11 is a horizontal composite pattern of four transmit sub-arrays and a single receive sub-array according to one embodiment;
FIG. 12 is a diagram of an embodiment in which a single transmit subarray scans horizontally through a 60 directional pattern;
FIG. 13 is a 60 synthetic directional diagram of the horizontal sweep of four transmit subarrays according to one embodiment;
FIG. 14 is a diagram of an embodiment in which a single receive subarray scans a 60 ° horizontal pattern;
FIG. 15 is a composite horizontal 60 ° directional pattern of a single transmit subarray and a single receive subarray according to one embodiment;
fig. 16 is a composite pattern of an embodiment in which four transmit sub-arrays are scanned horizontally by 60 ° with a single receive sub-array;
fig. 17 is a sparse antenna array composed of 6 MIMO antenna small arrays according to the second embodiment.
The figures in the drawings represent:
1-transmitting a subarray; 2-receiving a subarray; 3-clearance; 4-a transmit antenna unit; 5-receive antenna element.
Detailed Description
The above and further features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.
As shown in fig. 1, fig. 1 is a structural view of the mimo antenna subarray; wherein, the circle is the position of the transmitting antenna unit, and the triangle is the position of the receiving subarray antenna unit.
The MIMO sparse antenna comprises a plurality of MIMO antenna sub-arrays, wherein the MIMO antenna sub-arrays are arranged in a sparse mode, the MIMO antenna sub-arrays comprise 4 transmitting sub-arrays 1 which are not arranged in a sparse mode and 1 receiving sub-arrays 2 which are arranged in a sparse mode, a gap 3 is arranged between the transmitting sub-arrays 1 and the receiving sub-arrays 2, and planar Artificial Magnetic Conductor (AMC) structures which are distributed periodically are arranged in the gap 3.
The MIMO antenna subarray is integrally arranged to be rectangular, 4 transmitting subarrays 1 are arranged at four corners of the MIMO antenna subarray, transmitting antenna units 4 in the transmitting subarrays 1 are distributed in a rectangular grid mode, the array surface of the transmitting subarrays 1 is rectangular, a receiving subarray 2 is arranged in the middle of the MIMO antenna subarray, receiving antenna units 5 in the receiving subarray 2 are distributed in a rectangular grid mode, and the array surface of the receiving subarray 2 is in a cross shape.
In order to ensure that the transmitting subarray 1 and the receiving subarray 2 both have beam scanning capability, the transmitting subarray 1 and the receiving subarray 2 are both in a phased array system.
The transmitting subarray adopts non-sparse array, and the horizontal unit spacing and the vertical unit spacing of the transmitting subarray need to satisfy the constraint relation of phased array scanning angle to the antenna unit spacing, namely
Wherein d is the unit interval, lambda is the antenna working wavelength, and theta is the scanning angle.
According to the horizontal and vertical scanning angles of the transmitting subarray and the requirements of the antenna beam width, the horizontal unit distance dty and the number nty of units in the transmitting subarray, the vertical unit distance dtx and the number ntx of units in the transmitting subarray can be determined.
Can adopt a formula
Estimating the number of units required by the transmitting subarray and the receiving subarray in the horizontal direction and the vertical direction,
wherein λ is the antenna operating wavelength, B is the beam width required by the corresponding antenna subarray in the corresponding direction, and d is the unit spacing of the corresponding antenna subarray in the corresponding direction.
Preferably, the horizontal cell pitch dry of the receiving sub-array is an integer multiple of the horizontal cell pitch dty of the transmitting sub-array, and is usually 2 to 4 times. Likewise, the vertical cell pitch drx of the receiving subarray is an integer multiple of the vertical cell pitch dtx of the transmitting subarray, typically 2-4 times. The number of elements nry in the horizontal direction of the receiving subarray, and the number of elements nrx in the vertical direction is determined by the beam width of the receiving subarray in the horizontal direction and the vertical direction.
Preferably, the gap between the transmitting subarray and the receiving subarray is in an L shape, the width of the gap of the L-shaped vertical section is 2-4 times dty, and the height is equal to the product of dtx multiplied by ntx. The width of the gap of the L-shaped horizontal section is 2-4 times of dtx, and the length is dty multiplied by nty plus the width of the gap of the L-shaped vertical section.
In the L-shaped gap space, a periodically distributed planar AMC structure is designed, and the AMC working bandwidth is consistent with the antenna working bandwidth. AMC structures should have "cross" symmetry, and reference may be made to publicly reported forms of AMC structures, such as square, circular, mushroom AMC structures.
Preferably, the MIMO antenna array is composed of a plurality of MIMO antenna small arrays, each MIMO antenna small array is a rectangular grid array, the horizontal element spacing of the MIMO antenna array is 2 times the horizontal length (nry × dry) of the MIMO antenna small array, and the vertical element spacing is 2 times the vertical length (nrx × dry) of the MIMO antenna small array. The MIMO antenna array can be expanded according to the application requirement by the array rule.
The sparse array distribution method provided by the invention is simple and easy to implement, and optimization calculation by an optimization algorithm is not needed. The antenna array is composed of a plurality of identical transmitting sub-arrays and receiving sub-arrays, so that the antenna array has good expansibility. Compared with a receiving subarray array surface, the transmitting subarray array is smaller in size and easier to process and implement, modular design can be carried out on the transmitting subarray array and the receiving subarray array, complexity of antenna array processing can be obviously reduced, and cost can be reduced. By adopting the array arrangement method, the directional pattern grating lobe caused by sparse array arrangement can be effectively inhibited, and the method is particularly suitable for millimeter wave radar antennas, such as millimeter wave automobile radars, human body security check instruments and the like, and has higher engineering application value.
Example one
As shown in fig. 2 to 16, fig. 2 is a vertical directional diagram of a single transmitting subarray of the present embodiment; fig. 3 is a vertical synthetic directional diagram of four transmitting sub-arrays according to the present embodiment; fig. 4 is a vertical directional diagram of a single receiving subarray of the present embodiment; fig. 5 is a vertical combined directional diagram of a single transmitting subarray and a single receiving subarray according to the present embodiment; fig. 6 is a vertical direction diagram synthesized by four transmitting sub-arrays and a single receiving sub-array in the present embodiment; FIG. 7 is a horizontal directional diagram of a single transmitting subarray of the present embodiment; fig. 8 is a horizontal synthetic directional diagram of four transmitting sub-arrays in the present embodiment; FIG. 9 is a horizontal directional diagram of a single receiving sub-array of the present embodiment; fig. 10 is a horizontal combined directional diagram of a single transmitting subarray and a single receiving subarray according to the present embodiment; fig. 11 is a horizontal combined directional diagram of four transmitting sub-arrays and a single receiving sub-array in the present embodiment; fig. 12 is a horizontal 60 ° directional diagram of a single transmitting subarray of the present embodiment; fig. 13 shows the horizontal scanning 60 ° synthetic directional diagram of four transmitting sub-arrays in the present embodiment; fig. 14 is a diagram of a single receiving subarray of the present embodiment scanning 60 ° horizontally; fig. 15 is a horizontal 60 ° synthetic direction diagram of a single transmitting subarray and a single receiving subarray according to the present embodiment; fig. 16 shows a horizontal 60 ° synthetic pattern of four transmitting sub-arrays and a single receiving sub-array in this embodiment.
Aiming at the vehicle-mounted millimeter wave radar antenna, the invention provides a multi-input multi-output sparse antenna formed by a sparse array arrangement method, wherein the multi-input multi-output sparse antenna comprises 4 non-sparse array arrangement transmitting sub-arrays, 1 sparse array arrangement receiving sub-array and a gap between the transmitting sub-array and the receiving sub-array.
The designed antenna works at 79GHz, the horizontal direction of the transmitting subarray has the phase scanning capability, the horizontal unit distance dty is 1.9mm, and the number of units nty is 8. The transmitting subarray does not perform phase scanning vertically, the unit distance dtx is 2.5mm, and the number of units ntx is 4. The transmit sub-array comprises 32 antenna elements.
The receiving subarray is located in the middle, the horizontal unit distance dry is 2 × dry ═ 3.8mm, and the vertical unit distance drx is 2 × dtx ═ 5 mm. The receive subarrays add up to 365 antenna elements.
The gap between the transmitting subarray and the receiving subarray is in an L shape, the vertical width of the L shape is 2 × dty being 3.8mm, the height is ntx × dtx being 10mm, the horizontal width of the L shape is 2 × dtx being 5mm, and the length is nty × dty +2 × dty being 8 × 1.9+2 × 1.9 being 19 mm.
The MIMO small array formed by 4 transmitting sub-arrays and 1 receiving sub-array has length dry multiplied by 25-dty of 93.1mm and width dry multiplied by 17-dtx of 82.5mm
The directional diagram calculation results of the arranged MIMO antenna array are shown in fig. 2 to 16 below. The directional diagram calculation result shows that the synthetic directional diagrams between the single receiving subarray and the transmitting subarray form grating lobes, but the synthetic directional diagram of the transmitting antenna and the receiving antenna obtained by the array arrangement method has no grating lobes, a single main lobe directional diagram is obtained, the level of a side lobe is effectively inhibited, and the feasibility of the array arrangement method is proved. The attached figures list normal directional diagrams when the directional diagrams are not scanned in the vertical direction and the horizontal direction, and meanwhile, the directional diagrams are scanned in the horizontal direction for example, and the fact that the directional diagram grating lobes caused by sparseness can be effectively restrained by the arraying method is proved.
Example two
As shown in fig. 17, fig. 17 is a schematic diagram of a sparse antenna array composed of 6 MIMO antenna small arrays according to this embodiment.
On the basis of the first embodiment, 6 MIMO arrays are combined into an MIMO antenna array, wherein the MIMO antenna array is rectangular, the length of the MIMO antenna array is 5 times the length of the MIMO antenna array, and the width of the MIMO antenna array is 5 times the width of the MIMO antenna array. After the transmitting directional diagram and the receiving directional diagram are synthesized, grating lobes caused by sparse array arrangement of the MIMO antenna array directional diagram can be effectively inhibited, and the directional diagram example is similar to the case one and is not repeated.
The foregoing is merely a preferred embodiment of the invention, which is intended to be illustrative and not limiting. It will be understood by those skilled in the art that various changes, modifications and equivalents may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.