A shortwave mixed polarization receiving antenna array

Abstract

The present invention discloses a short-wave hybrid polarization receiving antenna array. The antenna array includes n receiving sub-arrays, where 1 < n ≤ 4 and n is a natural number. The antenna elements in the n receiving sub-arrays have the same layout and are placed concentrically. A number of antenna elements in each receiving sub-array are evenly arranged. The ratio of the characteristic dimensions of adjacent two receiving sub-arrays satisfies 1 ≤ 3. The characteristic dimension of the receiving sub-array represents the maximum distance between the array elements in the horizontal direction and the array elements in the vertical direction in the nth receiving sub-array. The present invention arranges the antennas at a certain distance while maintaining polarization orthogonality, so that the array aperture is no longer sparse, and the effective operating frequency band of the array is extended to the entire short-wave frequency band, making it have good radiation pattern characteristics in the whole frequency band.

Description

Technical Field

[0001] The invention belongs to the field of shortwave broadband radar, and in particular relates to a shortwave mixed polarization receiving antenna array. Background Art

[0002] The receiving antenna array is an important component in the shortwave broadband radar system, and its performance has an important impact on the overall performance of the radar system. For shortwave radar systems such as ionospheric altimeters, the site size and manufacturing cost are limited, the working frequency band is very wide, and it is susceptible to interference from shortwave frequency band broadcasting, communication and other systems. Therefore, the receiving antenna array is required to have the characteristics of small unit size, large working bandwidth, narrow digital synthetic beam, low sidelobe, and low cost. At present, shortwave broadband radars such as ionospheric altimeters mostly use single antennas or antenna arrays with a small number of units for reception, which have the disadvantages of large beam width variation with frequency and high side lobes of grating lobes at the high-frequency end. In practical applications such as ionospheric detection, there is an urgent need for ultra-wideband, spatial synthetic beam reception, miniaturization, and low cost.

[0003] The existing 60m regular triangle array (such as Figure 1 (as shown) is mainly aimed at the vertical measurement and drift detection modes of the ionospheric altimeter. The maximum operating frequency of the ionospheric frequency and height map in the vertical measurement mode generally does not exceed 15MHz, and the operating frequency in the drift detection mode is generally around 5MHz. The use of the 60m array is mainly to improve the low-frequency receiving performance of the system. However, the applicable frequency band of this array is limited. When the frequency increases, the side lobes of its radiation pattern increase, and even grating lobes appear, which may introduce interference and reduce the received signal-to-noise ratio; the number of array units is small, the aperture is sparse, and the main lobe of the array pattern is wide. When digital beam synthesis technology is used, the measurement accuracy of the incoming wave direction is poor; when the system works in the oblique measurement mode, the maximum frequency of the ionogram trace can reach 30MHz. When digital beam synthesis technology is used, a large number of high side lobes and grating lobes appear, which may introduce interference and are not conducive to the effective extraction of long-distance oblique measurement signals. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a shortwave hybrid polarization receiving antenna array. By splitting the original multiple groups of orthogonal active antennas into a number of independent antennas with orthogonal polarization, annular, cross-shaped, and square hybrid polarization arrays are constructed to solve the problems of narrow effective working band and wide lobe of low-frequency directional pattern caused by the sparse aperture of the original array; by reducing the size of the array, the problem of high side lobe height and grating lobe in the high frequency band of the array is improved; by increasing the array units, multiple sub-arrays of different scales are constructed, and each sub-array is co-centeredly arranged, so as to improve the radiation characteristics of the receiving array in the entire shortwave band, so that it can simultaneously meet the requirements of vertical measurement, oblique measurement, and drift detection.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A short-wave hybrid polarization receiving antenna array, the antenna array includes n receiving sub-arrays, 1 < n ≤ 4, n is a natural number, the antenna elements in the n receiving sub-arrays have the same layout and are placed concentrically, and several antenna elements in each receiving sub-array are evenly arranged, and the characteristic dimensions of adjacent two receiving sub-arrays The ratio satisfies 1 < / ≤ 3, and the characteristic dimension of the receiving sub-array represents the maximum distance between the array elements in the horizontal direction and the array elements in the vertical direction in the nth receiving sub-array.

[0007] Furthermore, the receiving sub-array adopts any one of a circular sub-array, a square sub-array, and a cross-shaped sub-array, and the n receiving sub-arrays are evenly arranged in any one of the shapes of a circle, a square, and a cross.

[0008] Furthermore, each receiving sub-array includes m north-south linearly polarized antennas and m east-west linearly polarized antenna elements. For the circular sub-array, m is not less than 3; for the square and cross-shaped sub-arrays, m is 4.

[0009] Furthermore, when the receiving sub-array is a circular sub-array, m north-south linearly polarized antennas and m east-west linearly polarized antennas are placed at equal intervals and staggered at the 2m vertices of an inscribed equilateral 2m-sided polygon of a circle with a radius of .

[0010] Furthermore, when the receiving sub-array is a square sub-array, 4 north-south linearly polarized antennas are placed at the four vertices of a square with a side length of , and 4 east-west linearly polarized antennas are placed at the four vertices of a square with a side length of - , where is the horizontal / vertical distance between the two closest orthogonal array elements in the nth receiving sub-array.

[0011] Furthermore, when the receiving sub-array is a cross-shaped sub-array, 4 north-south linearly polarized antennas are placed at the four vertices of a cross with a length of Ln, and 4 east-west linearly polarized antennas are placed at the four vertices of a cross with a length of - , where is the horizontal / vertical distance between the two closest orthogonal array elements in the nth receiving sub-array.

[0012] Furthermore, the antenna elements in the receiving sub-array adopt any one of active antennas or non-active antennas.

[0013] Furthermore, the receiving antenna array is applied to a receiving antenna array of a radar with a shortwave frequency band of 1-30 MHz.

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

[0015] The original integrated orthogonal active antenna is split and arranged at a certain distance while maintaining polarization orthogonality, so that the array aperture is no longer sparse, the radiation main lobe width is reduced, and the sidelobe level is reduced, thereby improving the performance of the existing ionospheric altimeter system; by adopting a scheme of co-center arrangement of sub-arrays of different scales, the effective working frequency band of the array is extended to the entire shortwave frequency band, so that it has good radiation pattern characteristics in the entire frequency band. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of a 60m regular triangle array structure in the prior art;

[0017] FIG. 2 (a) is a schematic diagram of a shortwave mixed polarization receiving antenna array structure according to the present invention;

[0018] FIG2( b ) is a second schematic diagram of a shortwave hybrid polarization receiving antenna array structure of the present invention;

[0019] FIG2 (c) is a third schematic diagram of a shortwave hybrid polarization receiving antenna array structure of the present invention;

[0020] FIG3 (a) is a schematic diagram of a shortwave hybrid polarization receiving antenna array subarray structure of the present invention;

[0021] FIG3 (b) is a second schematic diagram of a shortwave hybrid polarization receiving antenna array subarray structure of the present invention;

[0022] FIG3 (c) is a third schematic diagram of a shortwave hybrid polarization receiving antenna array subarray structure of the present invention;

[0023] FIG. 4 is a schematic diagram of an antenna unit of a shortwave hybrid polarization receiving antenna array subarray according to the present invention. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0025] Shortwave broadband radar systems such as ionospheric altimeters based on the prior art mostly use one group of receiving antennas or four groups of antenna units to form a receiving array, which has technical problems such as large variation of the receiving beam with frequency, high side lobes, and narrow available frequency band of digital beam synthesis technology. The present invention provides a low-cost, flexibly deployable, and scalable hybrid polarization receiving antenna array, which plays a very positive role in promoting the development and application of ionospheric altimeter technology and other shortwave broadband radar technologies.

[0026] Figures 2(a), 2(b), and 2(c) are schematic diagrams of the structure of a hybrid polarization receiving antenna array according to an embodiment of the present invention, respectively. The hybrid polarization receiving antenna array comprises: a first receiving subarray 1, a second receiving subarray 2, ..., an nth receiving subarray n. The number n of subarrays in the hybrid polarization receiving antenna array is generally no more than 4 (1<n≤4, n is a natural number), which can be specifically determined according to the operating frequency band of the shortwave broadband radar system.

[0027] The layout of the first, second, ..., nth receiving subarrays 1, 2, ..., n is consistent and co-centered, and the characteristic size of two adjacent subarrays is The ratio satisfies 1< / ≤3. is the maximum distance between the horizontal array units and the vertical array units in the nth receiving subarray n, and the antenna units in each receiving subarray are evenly arranged.

[0028] The shapes of the first, second, ..., nth receiving antenna subarrays 1, 2, ..., n are generally ring-shaped, square-shaped, or cross-shaped, which can be selected according to the actual installation site. As shown in FIG2 (a), each element of the first receiving subarray 1 is represented as … , each element of the second receiving subarray 2 is expressed as … , each element of the nth receiving subarray n is represented as … Each receiving subarray includes m north-south linear polarized antennas and m east-west linear polarized antenna units. For a circular subarray, m is not less than 3; for a square or cross subarray, m is 4. Here, m=4 is selected as an example for each shape.

[0029] In combination with FIG. 2 (a) and FIG. 3 (a), when the first, second, ..., nth receiving subarrays 1, 2, ..., n are circular arrays, the hybrid polarization receiving antenna array is also a square, and the characteristic size is In the range of 5m-20m, the characteristic size In the range of 4.6m-18.5m, is the radius of the ring formed by the array elements in the nth receiving subarray n.

[0030] Combining FIG2(b) and FIG3(b), when the first, second, ..., nth receiving subarrays 1, 2, ..., n are square, the hybrid polarization receiving antenna array is also square, and the characteristic size is In the range of 7.5m-40m, the characteristic size In the range of 1m-5m, is the horizontal / vertical distance between the two closest orthogonal array elements in the nth receiving subarray n.

[0031] Combining FIG2(c) and FIG3(c), when the first, second, ..., nth receiving subarrays 1, 2, ..., n are in a cross shape, the hybrid polarization receiving antenna array is also in a cross shape, and the characteristic size is In the range of 7.5m-40m, the characteristic size In the range of 1m-5m, is the horizontal / vertical distance between the two closest orthogonal array elements in the nth receiving subarray n.

[0032] Without loss of generality, array layouts other than circular, square, and cross shapes may also be used, such as an equilateral triangle array.

[0033] FIG3 (a), FIG3 (b), and FIG3 (c) are schematic diagrams of specific structures of subarrays in a hybrid polarization receiving antenna array according to an embodiment of the present invention. Taking the nth receiving antenna subarray n as an example, it is assumed that it includes four north-south linearly polarized antennas. , , , , and 4 east-west linear polarized antenna units , , , .

[0034] The four north-south linear polarization antennas and four east-west linear polarization antennas of the circular subarray are placed at equal intervals and staggered at a radius of On the eight vertices of the equilateral octagon inscribed in the torus.

[0035] The four north-south linearly polarized antennas of the square subarray are placed on a At the four vertices of a square with a side length of - At the four vertices of the square.

[0036] The four north-south linearly polarized antennas of the cross-shaped subarray are placed at a length of At the four vertices of the cross, four east-west linearly polarized antennas are placed with a length of - At the four vertices of the cross.

[0037] Figure 4 FIG. 1 is a schematic diagram of the structure of an antenna unit constituting a subarray in a hybrid polarization receiving antenna array according to an embodiment of the present invention. The antenna unit is an electrically small active loop antenna ( Figure 4 (a)) or a small active dipole antenna ( Figure 4 Without loss of generality, non-active antennas can also be used as array elements, such as folded dipole antennas, Delta antennas, etc.

[0038] The electrically small active loop antenna comprises: an electrically small loop antenna Lnm1, a preamplifier Lnm2, and a supporting column Lnm3. The electrically small active loop antenna Lnm1 is generally square, with a characteristic size of ≤1.5m, support column height Lnm3 ≤1.5m. The preamplifier Lnm2 is generally a current amplification type, which can achieve impedance matching between the electric small loop antenna and the 50 ohm feeder and achieve gain compensation.

[0039] The electrically small active dipole antenna comprises: an electrically small dipole antenna Dnm1, a preamplifier Dnm2, and a supporting column Dnm3. Characteristic dimensions of the electrically small active dipole antenna ≤2.5m, height from the ground ≤2.5m. The preamplifier Dnm2 is generally a voltage amplifier type, which can achieve impedance matching between the electrically small dipole antenna and the 50 ohm feeder and achieve gain compensation. Support column Dnm3, height ≤2.5m.

[0040] The specific working mode of the hybrid polarization receiving antenna array is as follows: In the example shown in Figure 2, each unit of the hybrid polarization receiving antenna array is connected to the multi-channel receiver of a broadband short-wave radar such as an ionospheric altimeter through equal-length coaxial cables, and the received target echo is converted into an electrical signal and transmitted to the receiver. The radar host adopts digital beamforming technology to control each channel of the receiver to achieve amplitude and phase control, or to achieve amplitude and phase control during data post-processing, and to determine the direction of the incoming wave through spatial domain beamforming to maximize the receiving signal-to-noise ratio.

[0041] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A shortwave mixed polarization receiving antenna array, characterized in that: The antenna array includes n receiving sub-arrays, where 1 < n ≤ 4 and n is a natural number. The antenna elements in the n receiving sub-arrays have the same layout and are centered together. A number of antenna elements in each receiving sub-array are evenly arranged, and the characteristic dimensions of adjacent two receiving sub-arrays satisfy 1 < / ≤ 3. The characteristic dimension of the receiving sub-array represents the maximum distance between the array elements in the horizontal direction and the array elements in the vertical direction in the nth receiving sub-array.

2. A shortwave hybrid polarization receiving antenna array according to claim 1, characterized in that: The receiving subarray is any one of a circular subarray, a square subarray and a cross subarray, and the n receiving subarrays are evenly arranged in any one of a circular, square and cross shape.

3. A shortwave hybrid polarization receiving antenna array according to claim 2, characterized in that: Each receiving subarray includes m north-south linear polarization antennas and m east-west linear polarization antenna units; for the circular subarray, m is not less than 3; for the square and cross subarrays, m is 4.

4. A shortwave hybrid polarization receiving antenna array according to claim 3, characterized in that: When the receiving subarray is a circular subarray, m north-south linear polarization antennas and m east-west linear polarization antennas are equally spaced and staggered at a radius of On the 2m vertices of the equilateral 2m-gon inscribed in the torus.

5. A shortwave hybrid polarization receiving antenna array according to claim 3, characterized in that: When the receiving subarray is a square subarray, four north-south linear polarization antennas are placed on a square subarray with a side length of At the four vertices of a square with a side length of - At the four vertices of the square, is the horizontal / vertical distance between the two nearest orthogonal array elements in the nth receiving subarray.

6. A shortwave hybrid polarization receiving antenna array according to claim 3, characterized in that: When the receiving subarray is a cross-shaped subarray, four north-south linear polarization antennas are placed at the four vertices of the cross with a length of Ln, and four east-west linear polarization antennas are placed at the four vertices of the cross with a length of - At the four vertices of the cross, is the horizontal / vertical distance between the two nearest orthogonal array elements in the nth receiving subarray.

7. A shortwave hybrid polarization receiving antenna array according to any one of claims 4 to 6, characterized in that: The antenna unit in the receiving subarray is an active antenna or a non-active antenna.

8. The shortwave hybrid polarization receiving antenna array according to claim 1, characterized in that: The receiving antenna array is applied to a receiving antenna array of a radar with a shortwave frequency band of 1-30 MHz.

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