A beam broadening device for broadband array antenna

Abstract

The present application discloses a beam broadening device for a broadband array antenna, comprising at least four antenna elements, at least one low-pass filter, at least one phase matching unit, and only one power divider. The antenna elements are arranged along a straight line to form a one-dimensional array antenna; the one-dimensional array antenna adopts an unequal-spacing arrangement method; the minimum array spacing D in the entire array antenna is less than the high-frequency wavelength λ H . Each edge antenna element is respectively connected to a low-pass filter; the low-pass filter is used to achieve a gradient feed amplitude weighting; each central antenna element is respectively connected to a phase matching unit; the phase matching unit is used to compensate for the phase error caused by the introduction of the low-pass filter; the power divider is used to synthesize the output signals of all the antenna elements together to form the broadband array antenna. The present application can simultaneously meet the low-frequency gain and high-frequency beam width of the broadband array antenna.

Description

Technical Field

[0001] The present application relates to a beam broadening device for a broadband array antenna. Background Art

[0002] An array antenna, also known as an antenna array, refers to an antenna system composed of multiple identical single antennas (called array elements, antenna units or unit antennas) arranged in a certain pattern.

[0003] If the bandwidth is determined by the impedance characteristic, that is, the voltage standing wave ratio (VSWR), then whether the array antenna has broadband characteristics is determined by the antenna unit. The broadband characteristic of the antenna refers to the broadband characteristic of the antenna within an upper frequency limit f. H At least the lower frequency f L The directional characteristics and impedance characteristics of the antenna do not change significantly within a frequency band that is twice the frequency of the antenna. An antenna with broadband characteristics is called a broadband antenna.

[0004] An array antenna composed of multiple antenna units can achieve high gain, but at the same time the beam width in a certain direction becomes narrower. G = ηD (Formula 1), where G is gain, η is efficiency, and D is directivity coefficient. D = 40000 ÷ (θ E ×θ H )(Formula 2), where θ H is the horizontal (azimuth) beamwidth, θ E It is the vertical (elevation plane) beam width. From formula 1 and formula 2, we can know that the increase in the gain of the array antenna must be accompanied by a narrowing of the beam width in a certain direction. The beam width is usually measured by 3dB beamwidth.

[0005] See also Figure 1 , if the antenna is set at the origin O of the rectangular coordinate system, A is any point within the antenna pointing range (i.e., the antenna coverage range), and the projection of point A on the XOY plane is point B. The azimuth plane of the antenna is the XOY plane, and the elevation plane of the antenna is the AOB plane. The angle between line segment OB and the X-axis is is the azimuth of the antenna, and the angle θ between the line segment OA and the Z axis is the elevation angle of the antenna. H It refers to the beam width value corresponding to a 3dB drop in the maximum gain value of the antenna in the azimuth plane. Vertical beam width θ E It refers to the beam width value corresponding to a 3dB drop in the maximum gain value of the antenna in the elevation plane.

[0006] See also Figure 2 This is a one-dimensional array antenna, that is, an array antenna composed of multiple antenna units arranged along a straight line. For example, this is an equally spaced one-dimensional array antenna, and the array spacing (i.e., the spacing between any two adjacent antenna units) is d. The number of antenna units is N, and the feed amplitude weighting value of each antenna unit is Ii , i ranges from 0 to N-1. Assume that the pattern function of the antenna unit is F(θ) and the pattern function of the array antenna is E(θ). (Formula 3), where k = 2π / λ, λ is the wavelength of the center frequency of the antenna, d is the array spacing, and θ is the same elevation angle of all antenna units.

[0007] For a one-dimensional array antenna with equal amplitude weighting, that is, I 0 =I 1 =……=I N-1 =1, the beam width of the array antenna The unit is degree. Among them, θ B It refers to the beam width in the direction parallel to the arrangement direction of the antenna elements in a one-dimensional array antenna. For example, a one-dimensional array antenna is composed of multiple antenna elements along Figure 1 The Z-axis arrangement in the B Refers to the vertical beam width θ E For example, a one-dimensional array antenna is composed of multiple antenna units along Figure 1 The X-axis or Y-axis arrangement is composed of B refers to the horizontal beam width θ H .

[0008] The error of formula 4 is smaller when the value of N is larger, and the error is larger when the value of N is smaller. It can be clearly seen from formula 4 that the beam width θ of the array antenna B It is inversely proportional to the wavelength λ of the center frequency. For broadband array antennas, at the lower limit frequency f L To upper frequency limit f H It has broadband characteristics within the frequency band, and the lower limit frequency f L The corresponding low-frequency wavelength λ L Much larger than the upper frequency f H The corresponding high frequency wavelength λ H , so the corresponding relationship of its beam width can be approximately expressed as θ BL / θ BH ≈λ L / λ H =f H / f L (Formula 5). Wherein, the low-frequency beam width θ BL It refers to the direction parallel to the arrangement direction of the antenna elements in a one-dimensional array antenna at the lower limit frequency f L Beam width; high frequency beam width θ BH It refers to the direction parallel to the arrangement direction of the antenna elements in a one-dimensional array antenna at the upper limit frequency f. H beamwidth.

[0009] For a one-dimensional array antenna, the beam width orthogonal to the direction in which the antenna elements are arranged has no effect, and only the beam width along (i.e. parallel to) the direction in which the antenna elements are arranged is affected. For example, a one-dimensional array antenna is composed of multiple antenna elements along Figure 1 The horizontal beam width of the array antenna is not affected and is the same as that of a single antenna unit; the vertical beam width of the array antenna is affected and becomes narrower than that of a single antenna unit. According to the law that gain is inversely proportional to beam width, the low-frequency gain G of the broadband array antenna is L and high frequency gain G H Meet G L / G H ≈λ H / λ L =f L / f H (Formula 6). Wherein, the low-frequency gain G L It means at the lower frequency f L Gain value; high frequency gain G H It means at the upper frequency f H gain value.

[0010] From Formula 5 and Formula 6, we know that: θ BL / θ BH ≈G H / G L Please refer to Table 1, which takes a broadband 4-element one-dimensional array antenna as an example. "4-element" means that an array antenna is composed of 4 antenna elements. Assume that the relative bandwidth is 4:1, that is, the frequency band with broadband characteristics satisfies f H =4f L , the array spacing d is 1 times the high frequency wavelength λ H , the beam width of the antenna unit in the direction parallel to the arrangement direction of the antenna units in the one-dimensional array antenna is 90°, the efficiency of the array antenna is 0.9, and the beam width and gain value of the one-dimensional array antenna in the direction parallel to the arrangement direction of the antenna units at different frequencies are calculated.

[0011] Frequency value wavelength Beam width (°) Gain value (dBi) <![CDATA[f L ]]> <![CDATA[4λ H ]]> 67.72 7.7 <![CDATA[4f L / 3]]> <![CDATA[3λ H ]]> 50.8 9.0 <![CDATA[2f L ]]> <![CDATA[2λ H ]]> 33.86 10.7 <![CDATA[2.25f L ]]> <![CDATA[1.77λ H ]]> 30.0 11.2 <![CDATA[3f L ]]> <![CDATA[4λ H / 3]]> 22.57 12.48 <![CDATA[3.5f L ]]> <![CDATA[8λ H / 7]]> 20 12.9 <![CDATA[4f L ]]> <![CDATA[λ H ]]> 16.93 13.7

[0012] Table 1: Beamwidth and gain of one-dimensional array antenna at different frequencies

[0013] It can be seen from Table 1 that the 4-element equidistant one-dimensional array antenna with a relative bandwidth of 4:1 has a maximum frequency of f H The high-frequency beam width in the direction parallel to the arrangement direction of the antenna elements is only at the lower limit frequency f L The low-frequency beam width in the direction parallel to the antenna unit arrangement direction is 1 / 4, at the lower limit frequency f L The low-frequency gain at the upper frequency fH 1 / 4 (6dB) of the high frequency gain at .

[0014] When broadband array antennas are used, they usually require relatively consistent indicators within the entire broadband frequency band, such as requiring the horizontal beam width of the entire frequency band to be greater than a certain value, requiring the vertical beam width of the entire frequency band to be greater than a certain value, and requiring the gain of the entire frequency band to be greater than a certain value; the high-frequency beam width and low-frequency gain of broadband array antennas in the direction parallel to the arrangement direction of the antenna units are the most difficult indicators to meet. For example, the full-band gain of the array antenna is required to be ≥9dBi, and the beam width in any direction is required to be ≥20° (i.e. ±10°). For the array antennas described in Table 1, at a frequency value <4f L / 3 frequency range cannot meet the gain requirements, when the frequency value is > 3.5f L The frequency range cannot meet the beam width coverage requirements in the direction parallel to the antenna unit arrangement direction. L / 3 to 3.5f L The gain and beam width indicators can be met simultaneously within the frequency range.

[0015] Broadband array antennas can improve low-frequency gain by increasing the array spacing, but the coverage of high-frequency beam width in the direction parallel to the arrangement direction of the antenna units will be further deteriorated. Broadband array antennas can also improve the high-frequency beam width in the direction parallel to the arrangement direction of the antenna units by amplitude weighting and phase weighting, but the beam width of the entire frequency band will be widened, which will directly lead to further reduction in low-frequency gain. There are several existing solutions to the contradiction between the low-frequency gain of broadband array antennas and the high-frequency beam width in the direction parallel to the arrangement direction of the antenna units. First, use multiple array antennas in combination. For example, the first array antenna is located at f L To 2f L The second array antenna is at 2f L To 4f L The broadband characteristics are realized within the frequency band of f. Each array antenna independently meets the requirements of gain and beam width in the direction parallel to the arrangement direction of the antenna units. The combination of two array antennas can achieve broadband characteristics within the frequency band of f. L To 4f LFirst, the broadband characteristics, gain, and beam width in the direction parallel to the arrangement direction of the antenna units are achieved within the frequency band. Second, the beam width of the array antenna in the direction parallel to the arrangement direction of the antenna units is prioritized, and the gain index requirement is reduced. Third, the gain index of the array antenna is prioritized, and a rotation mechanism or beam scanning method is used to compensate for the insufficient beam width in the direction parallel to the arrangement direction of the antenna units. These existing technologies solve the contradiction between the low-frequency gain of the broadband array antenna and the high-frequency beam width in the direction parallel to the arrangement direction of the antenna units by increasing the number of array antennas, or reducing a certain index, or adding additional mechanisms, or adopting special scanning methods. Summary of the invention

[0016] The technical problem to be solved by the present application is to propose a beam broadening method for a broadband array antenna without increasing the number of array antennas, reducing any indicators, adding additional mechanisms, or adopting special scanning methods, which can broaden the high-frequency beam width in a direction parallel to the arrangement direction of the antenna units while improving the low-frequency gain.

[0017] In order to solve the above technical problems, the present application proposes a beam broadening device for a broadband array antenna, including at least four antenna units, at least one low-pass filter, at least one phase matching unit, and only one power divider. The antenna units are arranged along a straight line to form a one-dimensional array antenna; all antenna units are divided into two groups, the central antenna unit is at the center of the one-dimensional array antenna, and the edge antenna unit is at the edge of the one-dimensional array antenna; the edge antenna unit is axially symmetric with respect to the central antenna unit; the one-dimensional array antenna adopts an unequal spacing arrangement, that is: the distance between the centers of adjacent edge antenna units>the distance between the centers of adjacent edge antenna units and the center of the center antenna unit>the distance between the centers of adjacent center antenna units; the minimum array spacing D in the entire array antenna is less than the upper limit frequency f at which the broadband array antenna has broadband characteristics. H The corresponding wavelength λ H The number of the low-pass filters is the same as the number of edge antenna units, and each edge antenna unit is connected to a low-pass filter; the amplitude-frequency response characteristics of the low-pass filter are: the frequency band below the first frequency f0 is the full-pass zone, the frequency band between the first frequency f0 and the second frequency fd is the gradual decline zone, and the frequency band above the second frequency fd is the full-resistance zone, and the first frequency f0 is less than the second frequency fd; the low-pass filter is used to realize the gradual feeding amplitude weighting, f L 、f H are the lower limit frequency and upper limit frequency of the broadband array antenna with broadband characteristics, respectively, and f L to f HThe frequency band between is the working frequency band of the broadband array antenna; the gradient feeding amplitude weighting means that: the working frequency band of the broadband array antenna overlaps at least partially with the gradient drop zone of the amplitude frequency response of the low-pass filter, which is called the first overlapping frequency band, and the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradient drop curve of the amplitude frequency response in the first overlapping frequency band. The number of the phase matching units is the same as the number of the central antenna units, and each central antenna unit is connected to a phase matching unit; the phase matching unit is used to compensate for the phase error caused by the introduction of the low-pass filter. All low-pass filters and all phase matching units are connected to only one power divider, and the power divider is used to synthesize the output signals of all antenna units to form the broadband array antenna. The above device combines the one-dimensional array antenna arrangement mode with unequal spacing and the gradient feeding amplitude weighting, and widens the beam width (especially the high-frequency beam width) of the one-dimensional array antenna in the antenna unit arrangement direction under the premise of ensuring the full-band gain (especially the low-frequency gain).

[0018] Preferably, when the total number of antenna units is 4, the two middle antenna units are central antenna units, and the two outer antenna units are edge antenna units. When the total number of antenna units is 5, the middle antenna unit is the central antenna unit, and the four outer antenna units are edge antenna units; or, the three middle antenna units are central antenna units, and the two outer antenna units are edge antenna units. These are two preferred examples to illustrate the grouping method of the central antenna unit and the edge antenna unit.

[0019] Further, if there are no adjacent edge antenna units, the unequal spacing arrangement is as follows: the distance between the centers of adjacent edge antenna units and the center of the center antenna unit is greater than the distance between the centers of adjacent center antenna units. If there are no adjacent center antenna units, the unequal spacing arrangement is as follows: the distance between the centers of adjacent edge antenna units is greater than the distance between the centers of adjacent edge antenna units and the center antenna unit.

[0020] Further, if there are adjacent center antenna units, the minimum array spacing D in the entire array antenna is the distance between the centers of adjacent center antenna units; if there are no adjacent center antenna units, the minimum array spacing D in the entire array antenna is the distance between the centers of adjacent edge antenna units and the center of the center antenna unit; D≤λ H ; The minimum distance between the edges of adjacent antenna units is called the array gap, and the array gap is > 0.

[0021] Furthermore, the size of each antenna unit in the antenna unit arrangement direction of the broadband array antenna is less than the upper limit frequency f of the broadband characteristic of the broadband array antenna.H The corresponding wavelength λ H ; When the array gap is a×λ H When the size of each antenna unit in the broadband array antenna in the antenna unit arrangement direction is less than (1-a)×λ H , 0<a<1. Preferably, the antenna unit adopts tight coupling technology. This indicates that antenna units that meet the specific size requirements already exist in the prior art.

[0022] Furthermore, the gradient feeding amplitude weighting also includes: when the operating frequency band of the broadband array antenna partially overlaps with the full pass region of the amplitude frequency response of the low-pass filter, it is called a second overlapping frequency band, and the feeding amplitude weighting value of the broadband array antenna is always 1 in the second overlapping frequency band; when the operating frequency band of the broadband array antenna partially overlaps with the full resistance region of the amplitude frequency response of the low-pass filter, it is called a third overlapping frequency band, and the feeding amplitude weighting value of the broadband array antenna is always 0 in the third overlapping frequency band.

[0023] Preferably, when f L ≤f0<f H ≤fd, at f L In the frequency band from f0 to f0, the feeding amplitude weighting value of the broadband array antenna is 1; in the frequency band from f0 to f H In the frequency band, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band; at f H At , the feeding amplitude weighted value of the broadband array antenna is the lowest, which is Af, Af ≥ 0. This is the first case of the gradual feeding amplitude weighting. At this time, the first overlapping frequency band is f0 to f H frequency band, the second overlapping frequency band is f L To the f0 band, the third overlapping band does not exist.

[0024] Preferably, when f L ≤f0<fd≤f H When f L In the frequency band from f0 to f0, the feeding amplitude weighting value of the broadband array antenna is 1; in the frequency band from f0 to fd, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band; in the frequency band from fd to f H In the frequency band of , the feeding amplitude weighting value of the broadband array antenna is 0. This is the second case of the gradual feeding amplitude weighting. In this case, the first overlapping frequency band is the f0 to fd frequency band, and the second overlapping frequency band is f L to f0 band, the third overlapping band is fd to f H Frequency band.

[0025] Preferably, when f0≤f L <fH ≤fd, at f L to f H In the frequency band, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band; at f L At f, the feeding amplitude weighted value of the broadband array antenna is the highest, which is Bf; at f H At , the feeding amplitude weighted value of the broadband array antenna is the lowest, which is Af, 0≤Af<Bf≤1. This is the third case of the gradual feeding amplitude weighting. At this time, the first overlapping frequency band is f L to f H frequency band, the second overlapping frequency band does not exist, and the third overlapping frequency band does not exist.

[0026] Preferably, when f0≤f L <fd≤f H When f L In the frequency band from fd to fd, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band; in the frequency band from fd to f H In the frequency band, the feeding amplitude weighting value of the broadband array antenna is 0; in the frequency band of f L At , the feeding amplitude weighted value of the broadband array antenna is the highest, which is Bf, Bf≤1. This is the fourth case of the gradual feeding amplitude weighting. At this time, the first overlapping frequency band is f L to fd band, the second overlapping band does not exist, and the third overlapping band is fd to f H Frequency band.

[0027] Furthermore, when the low-frequency gain of the broadband array antenna needs to be guaranteed, f0>f L When it is necessary to ensure the high-frequency beam width in the arrangement direction of the antenna units in the broadband array antenna, select f0<f H low-pass filter, and when fd = f H The effect is best when

[0028] Preferably, the phase matching unit is a delay line, which is consistent with the phase error generated by the low-pass filter within the working frequency band of the broadband array antenna.

[0029] Furthermore, when the antenna units are arranged along the Z axis of the rectangular coordinate system to form a one-dimensional array antenna, the broadband array antenna has an upper limit frequency f H The vertical beam width θ at E When the antenna units are arranged along any straight line in the XOY plane of the rectangular coordinate system to form a one-dimensional array antenna, the broadband array antenna has an upper limit frequency f H The horizontal beam width θ at HWidened. For a two-dimensional array antenna, define the Z axis of the linear coordinate system as the radiation direction of the two-dimensional array antenna, and the X axis and Y axis correspond to the two dimensions of the two-dimensional rectangular array antenna respectively; regard a column of antenna units on the Y axis as a whole, called the Y axis antenna unit group, and the two-dimensional rectangular array antenna is equivalent to a one-dimensional array of multiple Y axis antenna unit groups on the X axis, and use the beam widening device of the broadband array antenna to perform beam widening design in the X axis direction; regard a column of antenna units on the X axis as a whole, called the X axis antenna unit group, and the two-dimensional rectangular array antenna is equivalent to a one-dimensional array of multiple X axis antenna unit groups on the Y axis, and use the beam widening device of the broadband array antenna to perform beam widening design in the Y axis direction; finally, the beam widening design in two directions of the two-dimensional array antenna is completed. This shows that the beam widening device of the broadband array antenna proposed in this application can be extended to two-dimensional array antennas.

[0030] Optionally, all the low-pass filters are changed to step-type amplitude weighting modules; the amplitude-frequency response characteristics of the step-type amplitude weighting module are as follows: the frequency band below the first frequency f0 is the full-pass zone, the frequency band between the first frequency f0 and the second frequency fd is the step-down zone, the frequency band above the second frequency fd is the full-block zone, and the first frequency f0 < the second frequency fd; the step-down zone is divided into at least two frequency bands, the lower the frequency band, the more amplitude is allowed to pass, and the higher the frequency band, the lower the amplitude is allowed to pass; the step-type amplitude weighting module is used to realize step-type feeding amplitude weighting; the step-type feeding amplitude weighting means that: the working frequency band of the broadband array antenna and the step-down zone of the amplitude frequency response of the step-type amplitude weighting module are at least partially overlapped, which is called the first overlapping frequency band, and in the first overlapping frequency band, the feeding amplitude weighting value of the broadband array antenna is synchronously reduced following the step-down curve of the amplitude frequency response.

[0031] Furthermore, the stepped feeding amplitude weighting also includes: when the operating frequency band of the broadband array antenna partially overlaps with the full pass zone of the amplitude frequency response of the stepped amplitude weighting module, it is called a second overlapping frequency band, and the feeding amplitude weighting value of the broadband array antenna is always 1 in the second overlapping frequency band; when the operating frequency band of the broadband array antenna partially overlaps with the full resistance zone of the amplitude frequency response of the stepped amplitude weighting module, it is called a third overlapping frequency band, and the feeding amplitude weighting value of the broadband array antenna is always 0 in the third overlapping frequency band.

[0032] The technical effect achieved by the present application is: balancing the contradiction between the low-frequency gain and the high-frequency beam width of the broadband array antenna, and can simultaneously achieve the improvement of the low-frequency gain and the widening of the high-frequency beam width. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1It is a schematic diagram of the azimuth and elevation planes of the antenna.

[0034] Figure 2 It is a simplified structural diagram of a one-dimensional array antenna.

[0035] Figure 3 It is a structural schematic diagram of the beam broadening device of the broadband array antenna proposed in this application.

[0036] Figure 4 It is a schematic diagram of the amplitude-frequency response characteristic curve of the low-pass filter 20 used in the present application.

[0037] Figures 5 to 8 It is a schematic diagram of four situations of gradual feeding amplitude weighting adopted in this application.

[0038] Fig. 9 This is a diagram showing the relationship between gain and frequency for a single dipole antenna.

[0039] Fig.10 This is a schematic diagram showing the relationship between the gain and angle of a single dipole antenna.

[0040] Fig.11 It is a schematic diagram of the relationship between the gain and frequency of the original array antenna and the array antenna of the present application.

[0041] Fig.12 It is a schematic diagram of the relationship between the gain and angle of the original array antenna and the array antenna of the present application.

[0042] Fig.13 It is a schematic diagram of the amplitude-frequency response characteristic curve of the stepped amplitude weighting module adopted in this application.

[0043] Explanation of the reference numerals in the figure: 10 is an antenna unit, 20 is a low-pass filter, 30 is a phase matching unit, and 40 is a power distributor. DETAILED DESCRIPTION

[0044] See also Figure 3 The beam broadening device of the broadband array antenna proposed in the present application includes at least four antenna units 10, at least one low-pass filter 20, at least one phase matching unit 30, and only one power divider 40.

[0045] All antenna units 10 are arranged along a straight line to form a one-dimensional array antenna. All antenna units 10 are divided into two groups according to their positions in the one-dimensional array antenna. The antenna unit at the center of the one-dimensional array antenna is called the center antenna unit, and the antenna unit at the edge of the one-dimensional array antenna is called the edge antenna unit. The edge antenna unit is axially symmetric with respect to the center antenna unit. For example, when the total number of antenna units is 4, the two middle antenna units are the center antenna units, and the two outer antenna units are the edge antenna units. For example, when the total number of antenna units is 5, there are two grouping methods. The first grouping method is: the middle antenna unit is the center antenna unit, and the four outer antenna units are the edge antenna units. The second grouping method is: the three middle antenna units are the center antenna units, and the two outer antenna units are the edge antenna units. When the total number of antenna units is more, the grouping method is analogous. The one-dimensional array antenna adopts an unequal spacing array method, usually using the method of keeping the array spacing of the center antenna unit of the equal spacing array antenna unchanged and appropriately increasing the array spacing of the edge antenna units. The "unequal spacing array" means: the distance between the centers of adjacent edge antenna units > the distance between the centers of adjacent edge antenna units and the center of the center antenna unit > the distance between the centers of adjacent center antenna units. If there are no adjacent edge antenna units, delete the term in the inequality. If there are no adjacent center antenna units, delete the term in the inequality. The minimum array spacing D in the entire array antenna is the distance between the centers of adjacent center antenna units. If there are no adjacent center antenna units, the minimum array spacing D in the entire array antenna is the distance between the centers of adjacent edge antenna units and the center of the center antenna unit. The array spacing refers to the distance between the centers of adjacent antenna units. D<λ H The minimum distance between the edges of adjacent antenna units is called the array gap. The array gap is usually > 0, that is, a certain gap needs to be kept between the edges of adjacent antenna units. Therefore, the size (length or width) of each antenna unit in the direction parallel to the antenna unit arrangement direction needs to be < λ H The existing miniaturized antenna units designed with tightly coupled technology can meet this size requirement. Preferably, when the array gap is 0.1λ H When the size (length or width) of each antenna unit in the direction parallel to the arrangement direction of the antenna units needs to be less than 0.9λ H .

[0046] The number of the low-pass filters 20 is the same as the number of the edge antenna units 10, and each edge antenna unit 10 is connected to a low-pass filter 20. The amplitude frequency response characteristics of the low-pass filter 20 are as follows: the frequency band below the first frequency f0 is a full pass zone (amplitude is 100%), the frequency band between the first frequency f0 and the second frequency fd is a gradual decline zone, and the frequency band above the second frequency fd is a full resistance zone (amplitude is 0), the first frequency f0 < the second frequency fd, as shown in FIG. Figure 4 shown.

[0047] The low-pass filter 20 is used to implement the gradual feeding amplitude weighting. Figures 5 to 8 The four situations shown. Among them, f L It is the lower limit frequency of the broadband characteristic of the array antenna, that is, the lowest frequency of the working frequency band of the broadband array antenna; f H It is the upper limit frequency of the broadband characteristic of the array antenna, that is, the highest frequency of the working frequency band of the broadband array antenna, f L to f H The frequency band between is the gradient feeding amplitude weighting area. Obviously, f L <f H . The gradient feeding amplitude weighting means that: the operating frequency band of the broadband array antenna and the gradient decreasing area of ​​the amplitude frequency response of the low-pass filter 20 at least partially overlap, which is called the first overlapping frequency band. In the first overlapping frequency band, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradient decreasing curve of the amplitude frequency response. The operating frequency band of the broadband array antenna may also partially overlap with the full pass area of ​​the amplitude frequency response of the low-pass filter 20, which is called the second overlapping frequency band. In the second overlapping frequency band, the feeding amplitude weighting value of the broadband array antenna is always 1. The operating frequency band of the broadband array antenna may also partially overlap with the full resistance area of ​​the amplitude frequency response of the low-pass filter 20, which is called the third overlapping frequency band. In the third overlapping frequency band, the feeding amplitude weighting value of the broadband array antenna is always 0.

[0048] See also Figure 5 , when f L ≤f0<f H ≤fd, at f L In the frequency band from f0 to f0, the feeding amplitude weighting value of the broadband array antenna is 1; in the frequency band from f0 to f H In the frequency band, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band. H At , the feeding amplitude weighted value of the broadband array antenna is the lowest, which is Af, Af≥0.

[0049] See also Figure 6 , when f L ≤f0<fd≤f HWhen f L In the frequency band from f0 to f0, the feeding amplitude weighting value of the broadband array antenna is 1; in the frequency band from f0 to fd, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band; in the frequency band from fd to f H In the frequency band, the feeding amplitude weighted value of the broadband array antenna is 0.

[0050] See also Figure 7 , when f0≤f L <f H ≤fd, at f L to f H In the frequency band, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band. L At f, the feeding amplitude weighted value of the broadband array antenna is the highest, which is Bf. H At , the feeding amplitude weighted value of the broadband array antenna is the lowest, which is Af, 0≤Af<Bf≤1.

[0051] See also Figure 8 , when f0≤f L <fd≤f H When f L In the frequency band from fd to fd, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band; in the frequency band from fd to f H In the frequency band of f, the feeding amplitude weighting value of the broadband array antenna is 0. L At , the feeding amplitude weighted value of the broadband array antenna is the highest, which is Bf, Bf≤1.

[0052] Preferably, when the low-frequency gain of the broadband array antenna needs to be guaranteed, f0>f L The low-pass filter corresponds to Figure 5 or Figure 6 Preferably, when it is necessary to ensure the high-frequency beam width of the broadband array antenna in a direction parallel to the arrangement direction of the antenna units, f0 < f H The low-pass filter corresponds to Figure 5 or Figure 6 or Figure 7 or Figure 8 The situation shown, and when fd = f H Therefore, Figure 5 , Figure 6 The illustrated situation can expand the high-frequency beam width in the direction parallel to the arrangement direction of the antenna elements while achieving low-frequency gain.

[0053] The number of the phase matching units 30 is the same as the number of the central antenna units 10, and each central antenna unit 10 is connected to a phase matching unit 30. The phase matching unit 30 is used to compensate for the phase error caused by the introduction of the low-pass filter 20. Preferably, the phase matching unit 30 is a delay line, which is consistent with the phase error generated by the low-pass filter 20 in the working frequency band of the broadband array antenna.

[0054] All low-pass filters 20 and all phase matching units 30 are connected to only one power divider 40, and the power divider 40 is used to combine the output signals of all antenna units 10 to form a broadband array antenna.

[0055] When there are at least four antenna elements along Figure 1 When the Z axis in the array is arranged to form a one-dimensional array antenna, the beam broadening device of the broadband array antenna proposed in the present application can be used to expand the upper limit frequency f H The vertical beam width θ at E When there are at least four antenna elements along Figure 1 When any straight line in the X-axis or Y-axis or XOY plane is arranged to form a one-dimensional array antenna, the beam broadening device of the broadband array antenna proposed in the present application can be used to expand the upper limit frequency f H The horizontal beam width θ at H .

[0056] Based on the same technical principle, the beam widening device of the broadband array antenna proposed in the present application can also be extended to the two-dimensional array antenna. Taking the two-dimensional rectangular array antenna as an example, the Z axis of the linear coordinate system is defined as the radiation direction of the two-dimensional rectangular array antenna, and the X axis and the Y axis correspond to the two dimensions of the two-dimensional rectangular array antenna respectively. A column of antenna units on the Y axis is regarded as a whole, called the Y-axis antenna unit group. The two-dimensional rectangular array antenna is equivalent to a one-dimensional array of multiple Y-axis antenna unit groups on the X axis. The beam widening scheme of the broadband array antenna proposed in the present application is used to design the beam widening in the X-axis direction. A column of antenna units on the X axis is regarded as a whole, called the X-axis antenna unit group. The two-dimensional rectangular array antenna is equivalent to a one-dimensional array of multiple X-axis antenna unit groups on the Y axis. The beam widening scheme of the broadband array antenna proposed in the present application is used to design the beam widening in the Y-axis direction. Finally, the beam widening design of the two-dimensional rectangular array antenna in two directions is completed.

[0057] The technical solution of the present application is described below with a specific example. For example, the broadband frequency band of a vertically polarized array antenna is 800MHz to 3000MHz, and the relative bandwidth is 3.75:1. It is required to achieve a full-band gain of ≥9dBi, a horizontal 3dB beamwidth of ≥90 degrees in the full band, and a vertical 3dB beamwidth of ≥20 degrees in the full band. For this technical requirement, the array antenna must first use antenna units with a horizontal 3dB beamwidth of ≥90 degrees, usually dipole antennas. Please refer to Fig. 9 The gain of a single dipole antenna is generally between 5dBi and 9dBi. To meet the low-frequency gain requirement, four dipole antennas are required to form a one-dimensional array. Fig.10 , the horizontal 3dB beamwidth and vertical 3dB beamwidth of a single dipole antenna cannot meet the requirements. Figure 1 After the Z axis in the array is formed into a one-dimensional array antenna, it is assumed that the original array antenna is a high-frequency wavelength λ H The array spacing is equidistant. The array antenna of this application considers that the original array antenna has a low-frequency gain of about 7.7dBi, which needs to be increased by 1.3dBi to meet the requirements, so the spacing on both sides is adjusted to 1.2 times the high-frequency wavelength 1.2λ H The array antenna of this application also considers that the high-frequency vertical beam width of the original array antenna is about 10 degrees, which needs to be increased to 20 degrees, so a gradual amplitude weighting is adopted to select f L =800M, f0=2000M, f H =3000M, fd = 3200M low pass filter, f H The amplitude weighting at is 0.1. Fig.11 and Fig.12 , the array antenna of this application has achieved a low-frequency gain increase to 9dBi and a high-frequency vertical beam width increase to 20°. This shows that this application has balanced the contradiction between low-frequency gain and high-frequency beam width in the broadband array antenna array technology through the optimization of array spacing and gradual amplitude weighting technology, and can simultaneously achieve an increase in low-frequency gain and a widening of the high-frequency beam. This application does not require an increase in the number of array antennas, nor does it require the use of complex methods such as turntables or phase scanning. It has the advantages of simple structure, easy operation, and strong feasibility.

[0058] Alternatively, the low-pass filter 20 can also be completely changed into a step-type amplitude weighting module. The amplitude frequency response characteristics of the step-type amplitude weighting module are: the frequency band below the first frequency f0 is a full pass zone (amplitude is 100%), the frequency band between the first frequency f0 and the second frequency fd is a step-down zone, and the frequency band above the second frequency fd is a full resistance zone (amplitude is 0), the first frequency f0 < the second frequency fd, such as Fig.13The step-down area is divided into at least two frequency bands. The lower the frequency band, the more amplitude is allowed to pass through, and the higher the frequency band, the lower the amplitude is allowed to pass through. The step-type amplitude weighting module is used to implement the step-type feeding amplitude weighting, similar to Figures 5 to 8 The four situations shown. The stepped feeding amplitude weighting means that: the operating frequency band of the broadband array antenna at least partially overlaps with the stepped descent area of ​​the amplitude frequency response of the stepped amplitude weighting module, which is called the first overlapping frequency band. In the first overlapping frequency band, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the step-descent curve of the amplitude frequency response. The operating frequency band of the broadband array antenna may also partially overlap with the full-pass area of ​​the amplitude frequency response of the stepped amplitude weighting module, which is called the second overlapping frequency band. In the second overlapping frequency band, the feeding amplitude weighting value of the broadband array antenna is always 1. The operating frequency band of the broadband array antenna may also partially overlap with the full-blocking area of ​​the amplitude frequency response of the stepped amplitude weighting module, which is called the third overlapping frequency band. In the third overlapping frequency band, the feeding amplitude weighting value of the broadband array antenna is always 0.

[0059] Compared with the prior art, the main innovations and beneficial effects of this application are as follows.

[0060] First, the low-frequency gain of the array antenna is improved by forming an array antenna with multiple unit antennas (i.e., increasing the array aperture), and at the same time, an unequal spacing arrangement is used to minimize the further compression of the high-frequency beam width in the direction parallel to the arrangement direction of the antenna units due to the increased aperture.

[0061] Second, the high-frequency beam width in the direction parallel to the arrangement direction of the antenna units is widened by gradual amplitude weighting or step amplitude weighting, while avoiding the influence of gradual amplitude weighting or step amplitude weighting on the low-frequency gain; a low-pass filter is used as a specific implementation device of frequency gradual amplitude weighting, or a step amplitude weighting module is used as a specific implementation device of step amplitude weighting in frequency division, and the gradual change part or step change part between the passband and the stopband is used to realize the gradual change or step change of amplitude weighting with frequency.

[0062] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should all be included in the protection scope of the present application.

Claims

1. A beam broadening device for a broadband array antenna, characterized in that: It includes at least four antenna units, at least one low-pass filter, at least one phase matching unit, and only one power distributor; The antenna units are arranged along a straight line to form a one-dimensional array antenna; all antenna units are divided into two groups, the central antenna unit is at the center of the one-dimensional array antenna, and the edge antenna unit is at the edge of the one-dimensional array antenna; the edge antenna unit is axially symmetric with respect to the central antenna unit; the one-dimensional array antenna adopts an unequal spacing arrangement, that is: the distance between the centers of adjacent edge antenna units> the distance between the centers of adjacent edge antenna units and the center of the center antenna unit> the distance between the centers of adjacent center antenna units; the minimum array spacing D in the entire array antenna is less than the upper limit frequency f of the broadband array antenna having broadband characteristics H The corresponding wavelength λ H ; The number of the low-pass filters is the same as the number of the edge antenna units, and each edge antenna unit is connected to a low-pass filter; the amplitude-frequency response characteristics of the low-pass filter are: the frequency band below the first frequency f0 is the full-pass zone, the frequency band between the first frequency f0 and the second frequency fd is the gradual decline zone, and the frequency band above the second frequency fd is the full-resistance zone, and the first frequency f0 is less than the second frequency fd; the low-pass filter is used to realize the gradual feeding amplitude weighting, f L 、f H are the lower limit frequency and upper limit frequency of the broadband array antenna with broadband characteristics, respectively, and f L to f H The frequency band between is the operating frequency band of the broadband array antenna; the gradient feeding amplitude weighting means that: the operating frequency band of the broadband array antenna and the gradient decreasing region of the amplitude frequency response of the low-pass filter at least partially overlap, which is called the first overlapping frequency band, and within the first overlapping frequency band, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradient decreasing curve of the amplitude frequency response; The number of the phase matching units is the same as the number of the central antenna units, and each central antenna unit is connected to a phase matching unit; the phase matching unit is used to compensate for the phase error caused by the introduction of the low-pass filter; All low-pass filters and all phase matching units are connected to only one power divider, and the power divider is used to combine the output signals of all antenna units to form the broadband array antenna.

2. The beam broadening device of the broadband array antenna according to claim 1, characterized in that: When the total number of antenna units is 4, the two middle antenna units are central antenna units, and the two outer antenna units are edge antenna units; When the total number of antenna units is 5, the middle antenna unit is the central antenna unit, and the four outer antenna units are edge antenna units; or, the middle three antenna units are the central antenna units, and the two outer antenna units are edge antenna units.

3. The beam broadening device for a broadband array antenna according to claim 1, characterized in that: If there are no adjacent edge antenna units, the unequal spacing arrangement is as follows: the distance between the center of the adjacent edge antenna units and the center of the central antenna unit is greater than the distance between the centers of the adjacent central antenna units; If there are no adjacent central antenna units, the unequal spacing arrangement is as follows: the distance between the centers of adjacent edge antenna units>the distance between the centers of adjacent edge antenna units and the center of the central antenna unit.

4. The beam broadening device for a broadband array antenna according to claim 3, characterized in that: If there are adjacent center antenna units, the minimum array spacing D in the entire array antenna is the distance between the centers of adjacent center antenna units; if there are no adjacent center antenna units, the minimum array spacing D in the entire array antenna is the distance between the centers of adjacent edge antenna units and the center of the center antenna unit; D≤λ H ; The minimum distance between the edges of adjacent antenna units is called the array gap, and the array gap is > 0.

5. The beam broadening device for a broadband array antenna according to claim 1, characterized in that: The gradient feeding amplitude weighting also includes: when the operating frequency band of the broadband array antenna partially overlaps with the full pass region of the amplitude frequency response of the low-pass filter, it is called the second overlapping frequency band, and the feeding amplitude weighting value of the broadband array antenna is always 1 in the second overlapping frequency band; when the operating frequency band of the broadband array antenna partially overlaps with the full resistance region of the amplitude frequency response of the low-pass filter, it is called the third overlapping frequency band, and the feeding amplitude weighting value of the broadband array antenna is always 0 in the third overlapping frequency band.

6. The beam broadening device for a broadband array antenna according to claim 5, characterized in that: When f L ≤f0<f H ≤fd, at f L In the frequency band from f0 to f0, the feeding amplitude weighting value of the broadband array antenna is 1; in the frequency band from f0 to f H In the frequency band, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band; at f H At , the feeding amplitude weighted value of the broadband array antenna is the lowest, which is Af, Af ≥ 0; When f L ≤f0<fd≤f H When f L In the frequency band from f0 to f0, the feeding amplitude weighting value of the broadband array antenna is 1; in the frequency band from f0 to fd, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band; in the frequency band from fd to f H In the frequency band, the feeding amplitude weighting value of the broadband array antenna is 0; When f0≤f L <f H ≤fd, at f L to f H In the frequency band, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band; at f L At f, the feeding amplitude weighted value of the broadband array antenna is the highest, which is Bf; at f H At , the feeding amplitude weighted value of the broadband array antenna is the lowest, which is Af, 0≤Af<Bf≤1; When f0≤f L <fd≤f H When f L In the frequency band from fd to fd, the feeding amplitude weighting value of the broadband array antenna decreases synchronously with the gradual decrease curve of the amplitude frequency response of this frequency band; in the frequency band from fd to f H In the frequency band, the feeding amplitude weighting value of the broadband array antenna is 0; in the frequency band of f L At , the feeding amplitude weighted value of the broadband array antenna is the highest, which is Bf, Bf≤1.

7. The beam broadening device for a broadband array antenna according to claim 1, characterized in that: The phase matching unit is a delay line, which is consistent with the phase error generated by the low-pass filter in the working frequency band of the broadband array antenna.

8. The beam broadening device for a broadband array antenna according to claim 1, characterized in that: When the antenna units are arranged along the Z axis of the rectangular coordinate system to form a one-dimensional array antenna, the broadband array antenna has an upper limit frequency f H The vertical beam width θ at E When the antenna units are arranged along any straight line in the XOY plane of the rectangular coordinate system to form a one-dimensional array antenna, the broadband array antenna has an upper limit frequency f H The horizontal beam width θ at H be widened; For a two-dimensional array antenna, the Z axis of a linear coordinate system is defined as the radiation direction of the two-dimensional array antenna, and the X axis and the Y axis correspond to the two dimensions of the two-dimensional array antenna respectively; a column of antenna units on the Y axis is regarded as a whole, called a Y-axis antenna unit group, and the two-dimensional array antenna is equivalent to a one-dimensional array of multiple Y-axis antenna unit groups on the X axis, and the beam widening device of the broadband array antenna described in claim 1 is used to perform beam widening design in the X-axis direction; a column of antenna units on the X axis is regarded as a whole, called an X-axis antenna unit group, and the two-dimensional array antenna is equivalent to a one-dimensional array of multiple X-axis antenna unit groups on the Y axis, and the beam widening device of the broadband array antenna described in claim 1 is used to perform beam widening design in the Y axis direction; finally, the beam widening design in two directions of the two-dimensional array antenna is completed.

9. The beam broadening device for a broadband array antenna according to claim 1, characterized in that: The low-pass filters are all changed into step-type amplitude weighting modules; the amplitude-frequency response characteristics of the step-type amplitude weighting module are as follows: the frequency band below the first frequency f0 is the full-pass zone, the frequency band between the first frequency f0 and the second frequency fd is the step-down zone, the frequency band above the second frequency fd is the full-block zone, and the first frequency f0 < the second frequency fd; the step-down zone is divided into at least two frequency bands, the lower the frequency band, the more amplitude is allowed to pass, and the higher the frequency band, the lower the amplitude is allowed to pass; the step-type amplitude weighting module is used to realize step-type feeding amplitude weighting; the step-type feeding amplitude weighting means that: the working frequency band of the broadband array antenna and the step-down zone of the amplitude frequency response of the step-type amplitude weighting module are at least partially overlapped, which is called the first overlapping frequency band, and in the first overlapping frequency band, the feeding amplitude weighting value of the broadband array antenna is synchronously reduced following the step-down curve of the amplitude frequency response.

10. The beam broadening device for a broadband array antenna according to claim 9, characterized in that: The stepped feeding amplitude weighting also includes: when the operating frequency band of the broadband array antenna partially overlaps with the full pass zone of the amplitude frequency response of the stepped amplitude weighting module, it is called a second overlapping frequency band, and the feeding amplitude weighting value of the broadband array antenna is always 1 in the second overlapping frequency band; when the operating frequency band of the broadband array antenna partially overlaps with the full resistance zone of the amplitude frequency response of the stepped amplitude weighting module, it is called a third overlapping frequency band, and the feeding amplitude weighting value of the broadband array antenna is always 0 in the third overlapping frequency band.

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