A 60° Oblique Polarization Ultra-Wideband Low-Profile Array Antenna Element

Abstract

The present invention belongs to the field of radar antennas, and proposes a 60° slant-polarized ultra-wideband low-profile array antenna element, specifically a regular hexagonal planar stacked antenna element, mainly including a metal reflector, a dielectric layer and a radiation layer, wherein three rotationally symmetric dart-shaped radiation arms are etched on the surface of the radiation layer. Through the regular triangular grid arrangement, the radiation arms of the elements in the array are tightly capacitively connected to the radiation arms of the adjacent elements in the 90° direction and the 30° slant direction to form a tight coupling mode. By synthesizing the radiation currents in these two directions, the 60° slant polarization is equivalently realized, avoiding the bandwidth limitation problem caused by the direct connection of the elements in the 60° direction, and realizing the ultra-wideband and low-profile characteristics of the 60° slant-polarized array. Similarly, by reasonably rotating and arranging the antenna elements of the present invention, the -60°, ±30° slant-polarized ultra-wideband low-profile arrays can also be realized. This antenna element is applicable to the slant-polarized ultra-wideband low-profile array antennas with special requirements for the vertical polarization and horizontal polarization gains.

Description

Technical Field

[0001] The present invention relates to the field of radar antennas. Background Art

[0002] Currently, in the field of phased array radars, it is required that the planar array has ultra-wideband and low-profile characteristics, and the planar array also needs to have a specific polarization form, such as horizontal, vertical linear polarization or elliptical polarization, etc. In a detection system, in order to detect signals of horizontal polarization and vertical polarization, the antenna is usually designed in a dual-polarization form. Actually, in order to reduce the complexity of the multi-polarization detection system, the antenna is often designed as 45° oblique polarization, so that both the horizontal component and the vertical component can be received, and the polarization gain is the same. The disadvantage is that the antenna gain for detecting the main polarization of the other party decreases. If it is required that the vertical polarization gain is greater than the horizontal polarization gain, a special polarization form is needed, such as 60° oblique polarization deviating from the horizontal direction (the polarization angle is referenced to the ground).

[0003] For a 60° oblique polarization ultra-wideband array, the usual solution is to first design an ultra-wideband vertical polarization array, and then cover a broadband polarization cover directly above the array surface to deflect the vertical polarization into 60° oblique polarization. Due to the existence of the polarization cover, the overall height of the antenna is relatively high, which is not conducive to the realization of a low profile. Another design solution is to design a low-profile antenna element and arrange it obliquely in the 60° direction, and use the principle of tight coupling to achieve ultra-wideband. Since the adjacent unit antennas in the 60° direction need to be tightly capacitively connected, it will cause the transverse electrical size of the antenna element to be too large, and self-resonance will occur inside the element, showing independence, and the ultra-wideband characteristic cannot be realized; if the adjacent units in the 60° direction are loosely capacitively connected, the discontinuity of the current in this mode will also cause resonance points in the band, which is not conducive to the realization of the ultra-wideband characteristic of the array. For example, when designing an 8*16 scale 60° oblique polarization triple-frequency broadband array, the element spacing in the azimuth plane is half of the wavelength corresponding to the high-frequency point. At this time, arranging the elements according to a rectangular grid, the element antennas need to be arranged obliquely at 60°. From the geometric relationship, it can be determined that the transverse size of the element is about 2 times the azimuth plane spacing, that is, one wavelength corresponding to the high-frequency point. At this time, the principle of tight coupling is no longer applicable, and the bandwidth is limited. If the transverse size of the element antenna is shortened, the adjacent units in the 60° direction cannot form a tight capacitive connection, and resonance points appear in the band, resulting in the inability to achieve an ultra-wide frequency range. Therefore, for a 60° oblique polarization array antenna, it is a difficult problem to simultaneously achieve ultra-wideband and low profile. Summary of the Invention

[0004] In view of the above problems, the present invention designs an ultra-wideband low-profile array antenna element suitable for 60° oblique polarization, and solves the problem that it is difficult to simultaneously achieve ultra-wideband and low profile in the design of a 60° oblique polarization array.

[0005] The present invention is achieved through the following technical solutions:

[0006] A 60° slant polarized ultra-wideband low-profile array antenna element, where the antenna element is a regular hexagon laminated structure, and from bottom to top are a metal reflector 1, a first dielectric layer 2, a second dielectric layer 3, a metal radiation layer 4, a third dielectric layer 5, and the feeding form adopts a double-probe feeding structure 6; the metal radiation layer 4 is etched on the upper surface of the second dielectric layer 3, and the double-probe feeding structure 6 vertically penetrates through the metal reflector 1 to the metal radiation layer 4; the metal radiation layer 4 is composed of three dart-shaped radiation arms that are rotationally symmetric about the center, with a rotation angle of 120°, and one end of the dart-shaped radiation arm points to the center of rotation, and the other end points to the position of the regular hexagon vertex.

[0007] Further, among the three dart-shaped radiation arms of the metal radiation layer 4, the radiation arm 4-2 is metallically connected to the radiation arm 4-3 near the center of rotation, and the radiation arm 4-1 is not connected to the other two arms.

[0008] Further, in the metal radiation layer 4, one probe of the double-probe feeding structure 6 contacts the radiation arm 4-1, and the other probe contacts the connection part of the radiation arm 4-2 and the radiation arm 4-3.

[0009] Further, for the first dielectric layer 2, the second dielectric layer 3, and the third dielectric layer 5 of the regular hexagon structure, cylindrical holes are dug in each dielectric layer with three non-adjacent vertices as the centers of the circles, which not only does not affect the performance of the radiation arms but also reduces the weight of the unit.

[0010] Further, after the regular hexagon unit antennas are arranged in a regular triangular grid, the dart-shaped radiation arms of three adjacent units form a tight coupling mode at the hexagon vertices, and the equivalent radiation current direction is the 60° slant direction. Of course, after the regular hexagon unit antenna is rotated according to the axis of symmetry, through reasonable layout, -60°, ±30° slant polarized ultra-wideband low-profile arrays can also be realized.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] The present invention solves the problem that it is difficult for a 60° slant polarized array to simultaneously achieve ultra-wideband and low-profile. Through the regular triangular grid arrangement, the radiation arms of the units in the array are tightly capacitively connected to the radiation arms of adjacent units in the 90° direction and the 30° slant direction to form a tight coupling mode. By synthesizing the radiation currents in these two directions, the 60° slant polarization is equivalently realized, avoiding the bandwidth limitation problem caused by direct connection of units in the 60° direction, and finally realizing the ultra-wideband characteristic of the 60° slant polarized array. The antenna element of the present invention is a planar structure, and has the characteristic of low profile after arraying. Description of the Drawings

[0013] Figure 1 It is a schematic structural diagram of the antenna element of the present invention;

[0014] Figure 2It is an 8x16 array structure for the arrangement of the antenna units of the present invention;

[0015] Figure 3 It is the active voltage standing wave ratio at the port under the infinite periodic boundary of the antenna unit of the present invention;

[0016] Figure 4 It is the polarization components of the far-field pattern under the infinite periodic boundary of the antenna unit of the present invention.

[0017] Description of the drawings: 1, metal reflector; 2, first dielectric layer; 3, second dielectric layer; 4, radiation layer; 4-1, radiation arm 1; 4-2, radiation arm 2; 4-3, radiation arm 3; 5, third dielectric layer; 6, double-probe feeding structure. Detailed implementation manners

[0018] The present invention will be further described in detail below with reference to the drawings and specific implementation cases.

[0019] Embodiment 1

[0020] Refer to Figure 1 , a 60° obliquely polarized ultra-wideband low-profile array antenna unit. The antenna unit is a regular hexagonal stacked structure, which includes a metal reflector 1, a first dielectric layer 2, a second dielectric layer 3, a metal radiation layer 4, a third dielectric layer 5, and a double-probe feeding structure 6 from bottom to top; the metal radiation layer 4 is composed of three dart-shaped radiation arms that are rotationally symmetric about the center, and the inner ends of the dart-shaped radiation arms point to the center of rotation, and the outer ends point to the vertex positions of the hexagon and are spaced apart by a certain distance. The dart-shaped radiation arms 4-2 and 4-3 are connected together by metal near the feeding structure and are in contact with one probe of the double-probe feeding structure, and the inner end of the dart-shaped radiation arm 4-1 extends to the center of rotation position and is in contact with the other probe of the double-probe feeding structure.

[0021] Refer to Figure 2 , and arrange the antenna units in Figure 1 according to a regular triangular grid into an 8*16 array. In the adjacent areas of three antenna units, each unit has a dart-shaped radiation arm capacitively connected to form a tightly coupled mode. It can be seen that the antenna units in the 60° oblique direction are not directly capacitively connected. By capacitively connecting with the two units in the 90° direction and the 30° oblique direction, the in-band resonance problem caused by direct tight capacitive connection in the 60° direction is avoided, which is beneficial to the realization of the ultra-wideband array.

[0022] The maximum lateral dimension of the antenna unit is 0.2λ 0 ~0.3λ 0 (λ 0 is the wavelength corresponding to the lowest frequency point f 0 ), and the total height of the antenna unit is less than 0.1λ 0 .

[0023] 1. Simulation Conditions and Contents

[0024] The unit antenna in Embodiment 1 is simulated using commercial simulation software. The simulation is set with periodic boundary conditions, and the simulation results are the active standing wave of the unit in an infinite array, the main polarization of the array, and the gains of the horizontal and vertical polarization components.

[0025] 2. Analysis of Simulation Results

[0026] Referring to Figure 3 , this simulation result is the active standing wave under normal scanning with periodic boundary conditions. It can be seen that within the frequency band of f 0 ~3f 0 , the active standing wave is less than 2.5, and it has good impedance matching characteristics within the three-octave bandwidth;

[0027] Referring to Figure 4 , this simulation result is the gain curves of the main polarization of the array and the horizontal and vertical polarization components at normal incidence under periodic boundary conditions. It can be seen that within the frequency band of f 0 ~3f 0 , the vertical polarization gain of the array is about 4.8 dB higher than the horizontal polarization, meeting the requirement that the vertical polarization gain is greater than the horizontal polarization gain.

[0028] In summary, the unit antenna designed by the present invention has good transmission and radiation characteristics within the three-octave bandwidth after being arrayed, and the total height of the array is less than 0.1 times the wavelength corresponding to the low-frequency point, having the structural characteristic of a low profile. The main polarization is 60° obliquely polarized. Of course, -60°, ±30° polarization forms can also be achieved through reasonable layout to meet special polarization requirements. Therefore, this antenna unit is suitable for obliquely polarized ultra-wideband low-profile array antennas with special requirements for vertical and horizontal polarization gains.

Claims

1. A 60° obliquely polarized ultra-wideband low-profile array antenna element, characterized in that: The antenna element is a regular hexagonal stacked structure, which successively includes a metal reflector (1), a first dielectric layer (2), a second dielectric layer (3), a metal radiation layer (4), and a third dielectric layer (5) from bottom to top. The feeding form adopts a double-probe feeding structure (6); the metal radiation layer (4) is etched on the upper surface of the second dielectric layer (3), and is composed of three dart-shaped radiation arms that are rotationally symmetric about the center, with a rotation angle of 120°. One end of the dart-shaped radiation arm points to the rotation center, and the other end points to the position of the regular hexagonal vertex. Among them, radiation arm 2 (4-2) is metallically connected to radiation arm 3 (4-3) near the rotation center, and radiation arm 1 (4-1) is not connected to the other two arms; the double-probe feeding structure (6) vertically penetrates the metal reflector (1), the first dielectric layer (2), the second dielectric layer (3) to the metal radiation layer (4), and one of the probes contacts radiation arm 1 (4-1), and the other probe contacts the connection part of radiation arm 2 (4-2) and radiation arm 3 (4-3); the first dielectric layer (2), the second dielectric layer (3) and the third dielectric layer (5) are all centered on three non-adjacent vertices of the regular hexagon, and cylindrical hole structures are dug out without affecting the radiation arm structure.

2. The 60° obliquely polarized ultra-wideband low-profile array antenna element according to claim 1, characterized in that: The regular hexagonal antenna element has rotational symmetry and can be used for -60°, ±30° obliquely polarized ultra-wideband low-profile array design.

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