Small-size low-sidelobe millimeter wave array antenna structure

Abstract

The utility model provides a millimeter wave array antenna structure with small volume and low sidelobe, and aims to solve the problems that a millimeter wave antenna array occupies a large area of a PCB (Printed Circuit Board) and the sidelobe leaks in the prior art. The antenna mainly comprises a vertical direction (elevation angle) antenna array structure and a horizontal direction (azimuth angle) antenna array structure, and the vertical direction antenna array structure is provided with a plurality of feed microstrip antennas which are linearly arranged and connected in series so as to compress the wave beam range of the array antenna on the elevation angle. The horizontal antenna array structure is provided with a plurality of feed microstrip antennas which are arranged in parallel and are connected in series through a power divider so as to compress the wave beam range of the array antenna on the azimuth angle; according to the array antenna structure design provided by the utility model, the compact power divider structure is provided, the series feed microstrip antenna array is combined, the occupied PCB area is reduced, low sidelobe optimization is carried out on the design of the power divider and the antenna unit, and the characteristics of narrow beam and low negative lobe are shown on the overall radiation characteristic.

Description

Technical Field

[0001] The utility model relates to the technical field of millimeter-wave radar array antennas, in particular to a millimeter-wave array antenna structure with a small volume and low side lobes. Background Art

[0002] Millimeter waves are electromagnetic waves with wavelengths between 1 millimeter and 10 millimeters in the electromagnetic wave spectrum, and the frequency range is approximately 30 GHz to 300 GHz. The disadvantages of millimeter-wave applications in the prior art are as follows: in the millimeter-wave band, since the antenna element spacing in the array antenna is very narrow, it makes the design of the feeding network more difficult. The existing design uses via backfeeding and combines a power divider feeding network to feed the array antenna. The radio frequency circuit needs to be distributed on both sides of the printed circuit board (PCB). This layout greatly increases the area occupied by the radio frequency circuit on the PCB and requires better electromagnetic shielding to prevent the radio frequency circuit from affecting the digital circuit.

[0003] In the existing antenna array design, the microstrip antenna elements maintain the same structure. Such a design can complete beam forming (BF) in phased array applications and adjust the orientation of its beam and the width of the main lobe. However, in non-phased applications, if an attenuator is not separately equipped for the feeding line of each transmitting antenna element, the array antenna will form relatively large side lobes, which will reduce the antenna gain in the main lobe direction, that is, reduce the performance of the antenna.

[0004] In summary, the millimeter-wave antenna array in the prior art has the problems of large PCB area occupation and side lobe leakage. Summary of the Utility Model

[0005] Aiming at the above-mentioned disadvantages in the prior art, the present application provides a millimeter-wave array antenna structure with a small volume and low side lobes, which has a compact power divider structure and combines series-fed microstrip antennas to form an array, reducing the occupied PCB area. At the same time, low side lobe optimization is carried out in the design of both the power divider and the antenna elements, showing the characteristics of a narrow beam and low negative lobes in the overall radiation characteristics.

[0006] The technical solution adopted by the utility model is as follows:

[0007] A millimeter-wave array antenna structure with a small volume and low side lobes, which includes a vertical-direction antenna array structure and a horizontal-direction antenna array structure established according to a plane rectangular coordinate system. The vertical-direction antenna array structure is configured with a plurality of series-fed microstrip antennas arranged linearly to compress the beam range of the array antenna in the elevation angle. The horizontal-direction antenna array structure is configured with a plurality of series-fed microstrip antennas arranged side by side along the X-axis through a power divider to compress the beam range of the array antenna in the azimuth angle.

[0008] Further, the power divider is an octal T-type series-parallel power divider.

[0009] Further, the power divider is symmetric about the midline. One end interface is the input port with an input impedance of 50 ohms, and the other end has eight output ports for connecting series-fed microstrip antennas, and the impedance of each output port is 50 ohms.

[0010] Further, each series-fed microstrip antenna is composed of six microstrip antenna units. The length of each microstrip antenna unit is the same, and the width of each microstrip antenna unit changes with its position on the Y-axis.

[0011] Further, the spacing between each microstrip antenna unit is half-wavelength width, and a quarter-wavelength matching microstrip line is provided at the feed entrance of the entire series-fed microstrip antenna.

[0012] Further, the copper thickness of the series-fed microstrip antenna is set to 35 μm.

[0013] Further, the thickness of the dielectric substrate of the series-fed microstrip antenna is 128 μm.

[0014] Further, the dielectric constant of the series-fed microstrip antenna is 3.

[0015] Further, the operating frequency of the millimeter-wave array antenna structure is 77 GHz.

[0016] The beneficial effects of the present utility model are as follows:

[0017] Compared with the prior art, for the array antenna structure design proposed by the present utility model, the 3dB width of the main lobe of the beam generated by the series-fed microstrip antenna is 29.6 degrees, the side lobe suppression is greater than 15dB, the overall width of the array is 18.853 mm, the length is 17.66 mm, and it contains 48 radiation units in total. This array antenna has a compact power divider structure and combines series-fed microstrip antennas to reduce the occupied PCB area. At the same time, low side lobe optimization is carried out in the design of the power divider and antenna units, showing the characteristics of narrow beam and low negative lobe in the overall radiation characteristics. Description of the Drawings

[0018] Figure 1 This is a schematic structural diagram of the power divider in the present utility model.

[0019] Figure 2 This is a schematic structural diagram of the array antenna of the present utility model. Specific embodiments

[0020] The following combines with the attached drawings to illustrate the specific embodiments of the present utility model.

[0021] The present utility model provides a millimeter-wave array antenna structure with a small volume and low side lobes, aiming to solve the problems that the millimeter-wave antenna array in the prior art occupies a large PCB area and has side lobe leakage.

[0022] As Figure 1 and Figure 2 shown, the present utility model includes a vertical-direction antenna array structure and a horizontal-direction antenna array structure established according to a plane rectangular coordinate system, wherein the plane rectangular coordinate system is: a two-dimensional Cartesian coordinate system (i.e., XY coordinate system) constructed by the radar azimuth plane and the vertical angle plane; the vertical-direction antenna array structure is configured with multiple linearly arranged series-fed microstrip antennas to compress the beam range of the array antenna in the elevation angle, and the horizontal-direction antenna array structure is configured with multiple series-fed microstrip antennas arranged side by side along the X-axis through a power divider to compress the beam range of the array antenna in the azimuth angle.

[0023] In one embodiment of the present utility model, the power divider is a one-to-eight T-type series-parallel power divider.

[0024] In one embodiment of the present utility model, the power divider has a left-right symmetric structure along the midline, one end interface is the input port with an input impedance of 50 ohms, and the other end has eight output ports for connecting series-fed microstrip antennas, and the impedance of each output port is 50 ohms.

[0025] In one embodiment of the present utility model, each series-fed microstrip antenna is composed of six microstrip antenna units, the length of each microstrip antenna unit is kept consistent, and the width of each microstrip antenna unit changes with its position on the Y-axis.

[0026] In one embodiment of the present utility model, the spacing between each microstrip antenna unit is half-wavelength width, and a quarter-wavelength matching microstrip line is provided at the feed inlet of the entire series-fed microstrip antenna.

[0027] In one embodiment of the present utility model, the copper thickness of the series-fed microstrip antenna is set to 35 μm.

[0028] In an embodiment of the present utility model, the thickness of the dielectric substrate of the series-fed microstrip antenna is 128 μm.

[0029] In an embodiment of the present utility model, the dielectric constant of the series-fed microstrip antenna is 3.

[0030] In an embodiment of the present utility model, the operating frequency of the millimeter-wave array antenna structure is 77 GHz.

[0031] The specific structure and working principle of the present utility model:

[0032] In a preferred embodiment, a two-dimensional rectangular coordinate system is established in the plane where the antenna is located, and the two dimensions are respectively named the X dimension and the Y dimension. In order to achieve an ultra-narrow beam, the antenna array needs to shrink its beam range simultaneously in the X dimension (azimuth angle) and the Y dimension (elevation angle). In the Y dimension, a series-fed microstrip antenna is used to compress the beam range of the array antenna in the Y dimension. In the X dimension, by using a one-to-multiple power divider, multiple series-fed microstrip antennas are arranged side by side along the X axis, thereby achieving beam compression in the X dimension.

[0033] In order to avoid the problem of sidelobe leakage of the array antenna, it is necessary to change the radiation power of each micro-single antenna unit so that it conforms to the power distribution of low-sidelobe designs such as Chebyshev distribution and Taylor distribution. In the Y dimension, the radiation power distribution of the overall antenna array in the Y dimension is achieved by changing the width of each microstrip antenna unit in the series-fed microstrip antenna. In the X dimension, the power distribution in the X dimension is achieved by setting the impedance of each microstrip line in the series-parallel T-shaped power divider network.

[0034] Substrate and copper foil parameters:

[0035] The copper thickness of the microstrip antenna is set to 35 microns. The thickness of the dielectric substrate of the microstrip antenna is 128 microns, and the dielectric constant is 3. The operating frequency designed for the array antenna is set to 77 GHz.

[0036] Power divider structure:

[0037] As Figure 1 shown, the power divider uses a 1-to-8 T-shaped series-parallel power divider. From a structural perspective, it can be divided into left and right ends, and the left and right ends are symmetric along the center line aw. Among them, port 0 is the input port, and the input impedance is 50 ohms. Ports 1 to 8 are 8 output ports, which are connected to the series-fed microstrip antennas. The impedance of the 8 output ports is 50 ohms.

[0038] The specific dimensions on the right side of the power divider are as follows:

[0039] Line segment Length in millimeters ab 0.15 bc 2.3 ca 0.495 ad, ef 0.280 de 0.544 fg, ij, mn 1.899 ug, hi 0.099 gh 0.623 Jk, ml 0.247 kl 0.607 no 0.433 op 0.748 pq 1.276 rq 0.3 rs 0.623 ys 2.197 wt 1.102

[0040] The 8 output ports are evenly distributed and have the same size as port 8.

[0041] Series-fed microstrip antenna structure:

[0042] Each series-fed microstrip antenna is composed of 6 microstrip antenna elements. The length of each microstrip antenna element is kept consistent at 1.05 mm. The widths of the 6 microstrip antenna elements change with their positions on the Y-axis, being 0.78, 1.17, 1.3, 1.3, 1.04, and 0.78 mm in sequence. The spacing between each antenna is half-wavelength width. After considering the influence of the circuit board substrate, the corrected half-wavelength length is 1.22 mm. The width of the microstrip line connecting each antenna element is 0.14 mm. At the feeding entrance of the entire series-fed microstrip antenna, in order to achieve impedance matching, a quarter-wavelength matching microstrip line is set. The width of the matching microstrip line is 0.25 mm.

[0043] After integrating the power divider and the series-fed microstrip antenna, the overall structure of the array antenna is as Figure 2 shown.

[0044] The simulation results show that the 3dB beamwidth of the main lobe generated by this series-fed microstrip antenna is 29.6 degrees, and the side lobe suppression is greater than 15dB. This antenna has the characteristics of a narrow beam and low side lobes. The overall width of the array is 18.853 mm, the length is 17.66 mm, and it contains 48 radiation units in total.

[0045] The array antenna structure design proposed by the present utility model. This array antenna has a compact power divider structure and combines a series-fed microstrip antenna, enabling the array to occupy a very small PCB area. In the design of the power divider and antenna elements, low side lobe optimization has been carried out, and it shows the characteristics of a narrow beam and low negative lobes in the overall radiation characteristics.

[0046] The above description is an interpretation of the present utility model, not a limitation of the utility model. The scope defined by the present utility model can be seen in the claims. Any form of modification can be made within the protection scope of the present utility model.

Claims

1. A millimeter-wave array antenna structure with a small volume and low sidelobes, characterized in that: It includes a vertical antenna array structure and a horizontal antenna array structure established according to the plane rectangular coordinate system. The vertical antenna array structure is configured with multiple linearly arranged series-fed microstrip antennas to compress the beam range of the array antenna in the elevation angle. The horizontal antenna array structure is configured with multiple series-fed microstrip antennas arranged in parallel along the X-axis through a power divider to compress the beam range of the array antenna in the azimuth angle.

2. The millimeter-wave array antenna structure with a small volume and low sidelobes according to claim 1, characterized in that: The power divider is an octal T-type series-parallel power divider.

3. The millimeter-wave array antenna structure with small volume and low sidelobe according to claim 2, characterized in that: The power divider has a left-right symmetric structure along the midline. One end of it is an input port with an input impedance of 50 ohms, and the other end has eight output ports for connecting series-fed microstrip antennas, and the impedance of each output port is 50 ohms.

4. A millimeter-wave array antenna structure with a small volume and low sidelobes as described in claim 1, characterized in that: Each of the series-fed microstrip antennas is composed of six microstrip antenna elements. The length of each microstrip antenna element is kept the same, and the width of each microstrip antenna element changes with its position on the Y-axis.

5. The millimeter-wave array antenna structure with small volume and low sidelobe according to claim 4, characterized in that: The spacing between each of the microstrip antenna elements is half-wavelength width, and a quarter-wavelength matching microstrip line is provided at the feed inlet of the entire series-fed microstrip antenna.

6. A millimeter-wave array antenna structure with a small volume and low sidelobes as described in claim 1, characterized in that: The copper thickness of the series-fed microstrip antenna is set to 35 μm.

7. A millimeter-wave array antenna structure with a small volume and low sidelobes as described in claim 1, characterized in that: The thickness of the dielectric substrate of the series-fed microstrip antenna is 128 μm.

8. A millimeter-wave array antenna structure with a small volume and low sidelobes as claimed in claim 1, characterized in that: The dielectric constant of the series-fed microstrip antenna is 3.

9. A millimeter-wave array antenna structure with a small volume and low sidelobes as described in claim 1, characterized in that: The operating frequency of the millimeter-wave array antenna structure is 77 GHz.

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