A small array fed beamforming transmissive array antenna

Abstract

The application discloses a small-array-fed beamforming transmissive array antenna, which comprises a transmissive array surface and a small-array feed; the transmissive array surface is designed according to the conventional focusing transmissive array design theory, that is, a phase distribution is designed according to a focal length, so that the output of the transmissive array surface is an equal-phase surface under the irradiation of a feed located at a focal point, and a pencil beam is generated; the small-array feed is located at a focal plane of the transmissive array surface and is composed of M*N antenna units, and after irradiation to the transmissive array surface, M*N defocused scanning beams are generated; each antenna unit in the small-array feed is excited by using appropriate amplitude weight, so that a required beam can be generated. Compared with the existing beamforming transmissive array antenna synthesis technology, the application has flexible beamforming capability, is suitable for the design of beams with any shape, and has the advantages that the main lobe gain ripple of the designed beam is small, the side lobe level is low and the like.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, specifically a small array-fed beamforming transmission array antenna. Background Technology

[0002] Beamforming is an important antenna technology with wide applications in wireless communication, detection, and other fields. There are generally three methods to achieve beamforming. The first method is array antennas, which use specific amplitude and phase distributions to excite antenna elements to achieve the desired beamforming; however, this method often requires a complex feed network. The second method is phase-only reflective / transmittive array antennas, which design the phase of each reflective / transmittive element to generate the phase distribution required to radiate the target beam on the reflective / transmittive surface. Phase-only methods struggle to achieve high-performance beamforming, such as low sidelobe levels, small main lobe ripples, and steep transition regions. The third method is reflective / transmittive array antennas where both amplitude and phase can be designed. By controlling the reflection / transmission of a portion of the electromagnetic wave or by controlling the conversion of a portion of the electromagnetic wave to the desired polarization, amplitude modulation is introduced into the reflective / transmittive surface, thereby achieving high-performance beamforming. However, amplitude control can result in high backlobe levels or high cross-polarization, leading to a significant decrease in gain and efficiency.

[0003] In conclusion, design solutions for high-performance beamforming antennas still need to be explored. Summary of the Invention

[0004] The purpose of this invention is to provide a novel beamforming transmission array antenna with small array feeding, which has the advantages of low main lobe gain ripple and low side lobe level; and has flexible beamforming capability, suitable for the design of beams of arbitrary shapes.

[0005] The technical solution to achieve the purpose of this invention is: a beamforming transmission array antenna fed by a small array, the antenna comprising a transmission array and a fed small array;

[0006] The transmission array is designed according to the conventional focusing transmission array design theory, that is, the phase distribution is designed according to the focal length; under the illumination of the feed source located at the focal point, the output of the transmission array is an equiphase surface, generating a pencil beam.

[0007] The feed array, located at the focal plane of the transmission array, includes M×N antenna elements. After illuminating the transmission array, it generates M×N off-focus scanning beams.

[0008] Furthermore, the fed array, in which M×N antenna elements are fed through a power divider with a certain amplitude and phase, generates the desired shaped radiation pattern; the amplitude weight of the antenna elements is calculated by the following formula:

[0009] c = (a1, a2, ..., a M ) T (b1,b2,...,b N )

[0010] in,

[0011]

[0012] a i =F x (θ=θ xi ,0°),i=1,2,...,M

[0013] b j =F y (θ=θ yj (90°), j=1,2,...,N

[0014] In the formula, c is the amplitude weighting matrix of the antenna elements in the feed array. This is a two-dimensional target orientation pattern.

[0015] F x (θ,0°) and F y (θ, 90°) represent the target radiation patterns on the xoz and yoz planes, respectively. x1 ,θ x2 ,...,θ xM ), (θ y1 ,θ y2 ,...,θ yN ) are the scanning angles of the M and N off-focus scanning beams on the xoz and yoz planes, respectively.

[0016] Furthermore, the number M or N of the feed array in the x-axis or y-axis direction is calculated using the following formula:

[0017]

[0018]

[0019] In the formula, 2θ Dx0.5 2θ Dy0.5 The half-power beamwidths of the target beam in the xoz and yoz planes, respectively, and 2θ S0.5 This is the half-power beamwidth of the off-focus scanning beam.

[0020] Furthermore, in the feed array, the scanning angle of each off-focus scanning beam is obtained by sampling the main lobe region of the target beam at equal angular intervals.

[0021] Furthermore, in the fed array, the distance d between the x-axis or y-axis direction unit and the focal point.xi d yj It is calculated using the following formula:

[0022]

[0023]

[0024] In the formula, F is the focal length, and BDF is the beam deviation coefficient, which is usually less than 1.

[0025] Compared with the prior art, the present invention has the following significant advantages:

[0026] (1) It achieves high-performance shaped beams, including advantages such as small main lobe gain ripple and low side lobe level.

[0027] (2) It has flexible beamforming capabilities and is suitable for the design of beams of any shape.

[0028] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the beamforming transmission array antenna fed by a small array according to the present invention.

[0030] Figure 2 Figure (a) is a schematic diagram of the structure of the transmission unit used in the transmission array of the present invention, and Figure (b) is a schematic diagram of the overall structure and the structure of the second metal layer.

[0031] Figure 3 This is a characteristic curve of the transmission element used in the transmission array of the present invention.

[0032] Figure 4 This is a schematic diagram illustrating the working principle of the novel beamforming transmission array antenna with small array feeding according to the present invention in one-dimensional case.

[0033] Figure 5 This is a schematic diagram of the antenna element structure used in the feed array of the present invention.

[0034] Figure 6 This is a schematic diagram showing the arrangement and amplitude weighting of the power supply array in Example 1.

[0035] Figure 7 The radiation pattern of the flat-top beam transmission array antenna obtained from theoretical calculations in Example 1 is shown.

[0036] Figure 8 This is a structural diagram of the feed grid used in the feed array of Example 1.

[0037] Figure 9Figure (a) shows the normalized radiation pattern of the flat-top beam transmission array at the center frequency obtained from simulation and testing in Example 1, and Figure (b) shows the radiation pattern on the xoz plane.

[0038] Figure 10 This is a schematic diagram showing the arrangement and amplitude weighting of the power supply array in Example 2.

[0039] Figure 11 The radiation pattern of the flat-top cocut square transmission array antenna obtained by theoretical calculation in Example 2 is shown.

[0040] Figure 12 The normalized radiation patterns of the flat-top cocut square transmission array antenna obtained from the simulation in Example 2 are shown in the xoz and yoz planes. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0042] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0043] like Figure 1 As shown, the present invention provides a novel beamforming transmission array antenna fed by a small array, the antenna comprising a transmission array and a fed small array;

[0044] The transmission array is designed according to conventional focusing transmission array design theory, that is, the phase distribution is designed according to the focal length; so that when the feed source located at the focal point is illuminated, the output of the transmission array is an equiphase surface, generating a pencil beam.

[0045] Here, the transmission array is composed of transmission elements arranged in a quasi-periodic manner. The specific structure of the transmission elements can be arbitrary. By changing the parameters in the elements that affect the transmission phase, a pencil beam under focal illumination can be achieved.

[0046] Furthermore, select such as Figure 2The transmission element shown constructs a transmission array. The element size is 0.4λ, where λ is the free-space wavelength at the center frequency of 10 GHz. Three metal layers are separated by two 3 mm thick F4B dielectric substrates with a relative permittivity of 2.2. The first and third layers consist of orthogonal gratings, while the second layer is used for rotational polarization and phase shift; that is, x-polarized electromagnetic waves passing through this transmission element generate y-polarized electromagnetic waves, and the transmission phase is modulated by controlling the rotation angle β. A full-wave simulation of this transmission element is performed using periodic boundaries. Figure 3 The transmission amplitude and phase curves of the transmission element at the center frequency are shown. It can be seen that when the rotation angle β varies from 20° to 75°, the transmission amplitude is higher than -1.5dB, and the transmission phase range is 180°. By moving the element along... Figure 2 The red solid line in the diagram is radially symmetrical, enabling an additional 180° phase shift range. Therefore, this transmission element achieves a full 360° phase shift with high transmission amplitude. In all embodiments of this invention, the transmission array consists of 25 × 25 of these transmission elements, with dimensions of 300mm × 300mm (10λ × 10λ), and a focal length F of 7λ.

[0047] like Figure 1 and Figure 4 As shown, the feed array is located at the focal plane of the transmission array and consists of M×N antenna elements. After illuminating the transmission array, it generates M×N off-focus scanning beams.

[0048] The feed array, in which M×N antenna elements are fed by a power divider with a certain amplitude and phase, generates the desired shaped radiation pattern. The amplitude weight of the antenna elements is calculated by the following formula:

[0049] c = (a1, a2, ..., a M ) T (b1,b2,...,b N )

[0050] in,

[0051]

[0052] a i =F x (θ=θ xi ,0°),i=1,2,...,M

[0053] b j =F y (θ=θ yj (90°), j=1,2,...,N

[0054] In the formula, c is the amplitude weighting matrix of the antenna elements in the feed array. For a two-dimensional target pattern, F x (θ,0°) and F y (θ, 90°) represent the target radiation patterns on the xoz and yoz planes, respectively. x1 ,θ x2 ,...,θ xM ), (θ y1 ,θ y2 ,...,θ yN ) are the scanning angles of the off-focus scanning beams in the xoz and yoz planes, respectively.

[0055] The number of units M or N in the x-axis or y-axis direction of the feed array is calculated by the following formula, and the scanning angle of each off-focus scanning beam is obtained by sampling the main lobe region of the target beam at equal angular intervals.

[0056]

[0057]

[0058] In the formula, 2θ Dx0.5 2θ Dy0.5 θ represents the half-power beamwidth of the target beam in the xoz or yoz plane, respectively. S0.5 This is the half-power beamwidth of the off-focus scanning beam.

[0059] The scanning angle of each off-focus scanning beam in the feed array is obtained by sampling the main lobe region of the target beam at equal angular intervals.

[0060] The distance of the feed array elements from the focal point in the x-axis or y-axis direction is calculated using the following formula:

[0061]

[0062] In the formula, F is the focal length, BDF is the beam deviation coefficient, which is usually less than 1, (θ x1 ,θ x2 ,...,θ xM ), (θ y1 ,θ y2 ,...,θ yN ) are the scanning angles of the M and N off-focus scanning beams on the xoz and yoz planes, respectively.

[0063] Furthermore, select such as Figure 5The slotted coupled patch unit shown is used to construct an array antenna. This slotted coupled patch unit consists of two dielectric substrates with a ground plane between them. The patch is located on the upper surface of the upper dielectric substrate, and the feed line is located on the lower surface of the lower dielectric substrate. Energy from the feed line is coupled to the patch through a slot in the ground plane. The upper dielectric substrate is an F4B dielectric substrate with a relative permittivity of 2.2 and a thickness of 3 mm, while the lower dielectric substrate is a Rogers RO4003 dielectric substrate with a relative permittivity of 3.55 and a thickness of 0.813 mm.

[0064] The design scheme and advantages of the present invention are illustrated below with reference to two specific embodiments.

[0065] Example 1

[0066] Example 1 illustrates a transmissive array antenna with a radiating square flat-top beam. The target beamwidth is 30° in both orthogonal planes, meaning the main lobe range is [-15°, 15°]. According to the proposed design, six off-focus scanning beams with a beamwidth of 5° and scanning angles of -15°, -9°, -3°, 3°, 9°, and 15° are used along both the x and y axes. Therefore, the feed array consists of 6×6 slotted coupled patch elements. Along the x and y axes, the distances of the six elements from the focal point are -2.07λ0, -1.16λ0, -0.43λ0, 0.43λ0, 1.16λ0, and 2.07λ0, respectively, and the amplitude weight of each antenna element is the same. Figure 6 This demonstrates the arrangement of the fed array and the amplitude weight of each antenna element. When all antenna elements are excited simultaneously, the theoretically calculated square flat-top beam radiated by the transmission array antenna is as follows: Figure 7 As shown.

[0067] Figure 8 This illustrates the actual physical structure of the feed grid used in the feed array of this embodiment. Figure 9 The normalized radiation patterns on the xoz and yoz planes at the center frequency, obtained from simulation and testing, are shown. It can be seen that the test results are basically consistent with the simulation results. A flat-top beam with a beamwidth of 30° is achieved in both the xoz and yoz planes. The gain ripple within the main lobe is below 1.92dB and 2.93dB, respectively, and the sidelobe levels are below -19dB and -14.95dB, respectively. Therefore, this embodiment realizes a transmissive array antenna with a square flat-top beamwidth of 30°, and the realized flat-top beam exhibits small main lobe gain ripple and low sidelobe levels.

[0068] It should be noted that this invention is applicable to the design of square flat-top beams with different beamwidths, and can also be used to design circular flat-top beams by using a circular feed array.

[0069] Example 2

[0070] Example 2 illustrates a transmission array antenna with a radiating flat-top and cosecant square beam. The target beam in the xoz plane is a flat-top beam with a beamwidth of 30°, and the target beam in the yoz plane is a cosecant square beam within the range of [10°, 40°]. According to the proposed design, along the x-axis, six off-focus scanning beams with a beamwidth of 5° and scanning angles of -15°, -9°, -3°, 3°, 9°, and 15° are used to design the flat-top beam. Along the y-axis, six off-focus scanning beams with a beamwidth of 5° and scanning angles of 10°, 16°, 22°, 28°, 34°, and 40° are used to design the cosecant square beam. Therefore, the feed array consists of 6×6 slotted coupled patch elements. Along the x-axis, the distances of the six elements from the focal point are -2.07λ0, -1.16λ0, -0.43λ0, 0.43λ0, 1.16λ0, and 2.07λ0, respectively, with equal magnitude weights. Along the y-axis, the distances of the six elements from the focal point are 2.1λ0, 1.25λ0, 0.4λ0, -0.4λ0, -1.15λ0, and -1.9λ0, respectively, with magnitude weights of 1, 0.74, 0.56, 0.43, 0.33, and 0.25, respectively. Figure 10 The arrangement of the feed array and the amplitude weight of each antenna element are shown. When all antenna elements are excited simultaneously, the radiation pattern of the transmission array antenna obtained by theoretical calculation is as follows. Figure 11 As shown.

[0071] Figure 12 The normalized radiation patterns on the xoz and yoz planes are obtained from the simulation of a transmission array antenna with a flat-top, cosecant square beam in this embodiment. The simulation results show that a flat-top beam with a beamwidth of 30° is achieved in the xoz plane, with a maximum main lobe gain ripple of 1.72 dB and a sidelobe level below -25 dB. In the yoz plane, a cosecant square beam in the range [10°, 40°] is achieved, with a maximum main lobe gain ripple of 2.2 dB and a sidelobe level below -17.3 dB.

[0072] In summary, this invention has flexible beamforming capabilities, is suitable for designing beams of arbitrary shapes, and the designed beams have the advantages of low main lobe gain ripple and low sidelobe level.

[0073] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A beamforming transmission array antenna fed by a small array, characterized in that, The antenna includes a transmission array and a feed array; The transmission array is designed according to the design theory of focused transmission arrays, and the phase distribution is designed according to the focal length. Under the illumination of the feed source located at the focal point, the output of the transmission array is an equiphase surface, generating a pencil beam. The feed array, located at the focal plane of the transmission array, includes M×N antenna elements. After illuminating the transmission array, it generates M×N off-focus scanning beams. The feed array, in which M×N antenna elements are fed through a power divider with a certain amplitude and phase, generates the desired shaped radiation pattern; the amplitude weight of the antenna elements is calculated by the following formula: in, In the formula, c is the amplitude weighting matrix of the antenna element in the feed array, and F D (θ,φ) represents the two-dimensional target pattern, F x (θ,0°) and F y (θ, 90°) represent the target radiation patterns on the xoz and yoz planes, respectively. x1 , θ x2 ,...,θ xM ), (θ y1 , θ y2 ,...,θ yN ) represent the scanning angles of the M and N off-focus scanning beams on the xoz and yoz planes, respectively; The number M or N of the feed array in the x-axis or y-axis direction is calculated using the following formula: In the formula, 2θ Dx0.5 2θ Dy0.5 The half-power beamwidths of the target beam in the xoz and yoz planes, respectively, and 2θ S0.5 This is the half-power beamwidth of the off-focus scanning beam; The distance of the feed array elements from the focal point in the x-axis or y-axis direction. , It is calculated using the following formula: In the formula, F is the focal length, and BDF is the beam deviation coefficient, which is less than 1; Each transmission unit in the transmission array includes three metal layers separated by two dielectric substrates. The first and third metal layers are composed of orthogonal grids, and the second metal layer is used for rotational polarization and providing phase shift. The x-polarized electromagnetic wave passes through the transmission unit to generate the y-polarized electromagnetic wave, and the transmission phase is modulated by controlling the rotation angle β.

2. The beamforming transmission array antenna fed by a small array according to claim 1, characterized in that, The scanning angle of each off-focus scanning beam in the feed array is obtained by sampling the main lobe region of the target beam at equal angular intervals.

3. The beamforming transmission array antenna fed by a small array according to claim 1, characterized in that, The dielectric substrate is an F4B dielectric substrate with a relative permittivity of 2.2 and a thickness of 3 mm.

4. The beamforming transmission array antenna fed by a small array according to claim 1, characterized in that, The antenna unit is a slotted coupling patch unit, which includes two dielectric substrates with a ground plane in between. A patch layer is disposed on the upper surface of the upper dielectric substrate, and a feed line layer is disposed on the lower surface of the lower dielectric substrate. The energy on the feed line layer is coupled to the patch layer through the slot on the ground plane.

5. The beamforming transmission array antenna fed by a small array according to claim 4, characterized in that, The upper dielectric substrate is an F4B dielectric substrate with a relative permittivity of 2.2 and a thickness of 3 mm, and the lower dielectric substrate is a Rogers RO4003 dielectric substrate with a relative permittivity of 3.55 and a thickness of 0.813 mm.

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