CN114725667B - A Magnetoelectric Dipole Antenna for Autopilot Radar - Google Patents

Abstract

The invention discloses a magnetoelectric dipole antenna applied to an automatic driving radar, which belongs to the technical field of antenna engineering. The magnetoelectric dipole antenna is composed of a five-layer PCB board and a four-layer prepreg. It has high integration, strong stability, and a planar structure that is easy to conform to, and is suitable for autonomous driving MIMO radars. The magnetoelectric dipole antenna array is composed of three parts: a radiation part, a power divider part and a waveguide-to-coaxial structure part, and the impedance bandwidth of the antenna is widened through coupling. The antenna realizes the adjustable 3dB beam width by adding an adjustable dummy array and adjusting the unit spacing, which meets the performance requirements of the autonomous driving MIMO radar for the antenna.

Description

A Magnetoelectric Dipole Antenna for Autopilot Radar

technical field

The invention belongs to the technical field of antenna engineering, and relates to a magnetoelectric dipole antenna. The application background is MIMO radar for automatic driving, which has the characteristics of high integration, wide frequency band, and controllable 3dB beam width.

Background technique

The magnetoelectric dipole antenna obtains a symmetrical pattern on the E plane and the H plane by constructing magnetic poles and poles on the antenna radiation aperture, and its double resonance point can meet broadband matching. MIMO radar for autonomous driving has strict requirements on the 3dB beamwidth of the antenna. For example, in the paper "Patch Array Antenna Using a Dual Coupled FeedingStructure for 79GHz Automotive Radar Applications", a 3dB beamwidth of 8.1° in the ZX plane is achieved, and 70° in the ZY plane. ° beamwidth; in the paper "Hybrid thin film multilayer antenna for automotive radar at 77GHz", a 3dB beamwidth of 40° on the H plane and 12° on the E plane was achieved. In addition, in the 77GHz frequency band, the limitation of processing technology is also a major challenge to antenna design. Recently, LTCC technology has been widely studied in this field of automotive radar, for example in the paper "A 79-GHz resonant laminated waveguide slotted array antenna using novel shaped slots in LTCC In ", a waveguide slot antenna based on LTCC technology was proposed, which works by resonance; in the paper "A 79-GHz radar sensor in LTCC technology using gridarray antennas", a grid array applied to 79GHz radar was proposed antenna. However, due to material loss and other reasons, the efficiency of the antenna processed by the LTCC process is low, usually below 30%, so the low-loss PCB process is often used in the millimeter wave frequency band. For example, in the paper "A low-cost and high-gain 60-GHz differential phasedarray antenna in PCB process", a broadband multi-layer phased array antenna is proposed, which is based on the PCB process and finally achieves a radiation efficiency of 90%. .

Contents of the invention

On the basis of background technology, the present invention proposes a novel magnetoelectric dipole antenna array applied to automatic driving radar, which adopts the structure of multi-layer PCB board, has high integration, wide frequency band, and adjustable 3dB beam width, and The antenna performance required for autonomous driving radar is a good match.

The technical scheme that the present invention adopts is as follows:

A magnetoelectric dipole antenna applied to automatic driving radar, the antenna is stacked from bottom to top: the first layer of metal ground, the first layer of dielectric board, the second layer of metal ground, the first layer of prepreg, and the third layer of metal ground , The second layer of dielectric board, the second layer of prepreg, the fourth layer of metal ground, the third layer of dielectric board, the third layer of prepreg, the fifth layer of metal ground, the fourth layer of dielectric board, the fourth layer of prepreg, the sixth layer of metal Ground and fifth layer dielectric board;

The metal ring of the shielding cavity is set on the upper surface of the dielectric plate of the fifth layer. The metal ring of the shielding cavity is a ring-shaped patch, and a circle of metal holes of the shielding cavity is evenly arranged at the corresponding position of the metal ring of the shielding cavity, which is used to connect the metal ring of the shielding cavity and the sixth layer. Metal ground; multiple groups of magnetoelectric dipole metal patches are set in the annular structure of the metal ring of the shielding cavity, each group includes 4 patches in an array of 2×2, and the opposite corners of the 4 patches are connected to each other, each A magnetoelectric dipole metal hole is set at the corresponding position of the patch, which is used to connect the patch and the sixth layer of metal ground;

A coupling seam is opened on the metal ground of the sixth layer, and a group of magnetoelectric dipole metal patches corresponds to a coupling seam;

A fork-shaped microstrip feeder is provided on the upper surface of the fourth layer dielectric plate, and one coupling slot corresponds to a fork-shaped microstrip feeder. The fork-shaped microstrip feeder includes a U-shaped coupling area and a U-shaped bottom located in the opposite direction to the U-shaped opening. In the raised feeding area, the two ends of the coupling slit just overlap with the two arms of the U-shaped structure of the coupling area, and the corresponding position of the feeding area is provided with a feeder input hole for connecting the second power divider located on the upper surface of the third layer dielectric board. There are metal holes for passing through the feeder input hole on the fifth layer of metal ground, so as to ensure that the feeder input hole does not contact the fifth layer of metal ground;

A plurality of second power divider patches on the upper surface of the third layer dielectric board, each output hole of the second power divider patch is correspondingly connected to a feeder input hole;

A first power divider patch is provided on the upper surface of the second layer dielectric board, and each output hole of the first power divider patch is correspondingly connected to an output hole of a second power divider patch, and is not connected with the first power divider patch. Four-layer metal ground contact; the first power divider patch only includes one input hole;

The metal ground of the first layer and the metal ground of the second layer are provided with a square hollow area, and a circle of waveguide cavity metal holes is arranged around the hollow area, and the metal hole of the waveguide cavity communicates with the metal ground of the first layer and the metal ground of the second layer; The size of the hollow area on the second layer of metal ground is larger than that on the first layer of metal ground; a rectangular coupling patch is arranged in the hollow area on the second layer of metal ground, and a waveguide cavity output hole is set on the edge of the rectangular coupling patch. The cavity output hole is connected to the patch input hole of the first power divider, and is not in contact with the metal ground of the third layer;

The area enclosed by the metal hole of the waveguide cavity is the input of the magnetoelectric dipole antenna.

Further, the plurality of groups of magnetoelectric dipole metal patches are arranged in a row, and a column of dummy arrays is respectively arranged on both sides of the row of magnetoelectric dipole metal patches, and the structure of the dummy array is the same as that of the magnetoelectric dipoles. The metal patch is the same, each magnetoelectric dipole metal patch in the dummy array corresponds to a coupling slot, and then corresponds to a fork-shaped microstrip feeder, but the feeder of the feeder area of the fork-shaped microstrip feeder corresponding to the dummy array The input hole is directly connected to the fifth layer metal ground.

The invention adopts a multi-layer PCB board structure, which is easy to process, has high integration, has a planar structure, and is easy to be conformal. The impedance bandwidth of the magnetoelectric dipole array is coupled and fed, and the 3dB beam width is adjustable by adding adjustable dummy elements and adjusting the unit spacing, which meets the performance requirements of the autonomous driving MIMO radar for the antenna. The radiation structure of the magnetoelectric dipole antenna array is magnetoelectric dipoles, and the middle parts of the magnetoelectric dipoles are cross-connected to improve the impedance matching performance of the antenna. In addition to the feed array, a dummy radiation structure is added on both sides of the array. The feeder of the dummy radiation structure is grounded. By adjusting the ground point, the reflection phase of the dummy can be adjusted, thereby realizing the adjustment of the 3dB beam width in the horizontal direction. The waveguide-to-coaxial structure of the magnetoelectric dipole antenna array is composed of a surrounding cavity composed of a square metal patch and a metal hole and a metal hole connected to the input end of the power divider, and the waveguide field is realized by coupling. Transformation of the coaxial field.

Description of drawings

Fig. 1 is an exploded 3D view of the magnetoelectric dipole antenna array of the present invention.

Fig. 2 is a side view of the magnetoelectric dipole antenna array of the present invention.

Fig. 3 is a top view of the key structure of the magnetoelectric dipole antenna array of the present invention. Among them, Fig. 3(a) is the top view of the antenna radiation structure without adding dummy elements, Fig. 3(b) is the top view of the fork-shaped feeder and H-shaped coupling slot of the antenna, and Fig. 3(c) is the structure of the one-to-two power splitter Top view, Figure 3(d) is a top view of the waveguide-to-coaxial structure.

FIG. 4 is a schematic diagram of the antenna dummy array. Figure 4(a) is a top view of the array radiation structure after adding dummy elements, and Figure 4(b) is a schematic diagram of the grounding change of the dummy array fork feeder.

FIG. 5 is a horizontal plane gain pattern of the antenna structure 24 in FIG. 3( b ) with different lengths.

Figure 6 shows the variation of return loss with frequency for this antenna.

Fig. 7 is the gain pattern of the structure 24 = 0.45mm in Fig. 3(b) of this antenna.

In Figure 2, structure 1 is the first layer of metal ground, structure 2 is the first layer of dielectric board, structure 3 is the second layer of metal ground, structure 4 is the first layer of prepreg, structure 5 is the third layer of metal ground, and structure 6 is The second layer of dielectric board, structure 7 is the second layer of prepreg, structure 8 is the fourth layer of metal ground, structure 9 is the third layer of dielectric board, structure 10 is the third layer of prepreg, structure 11 is the fifth layer of metal ground , structure 12 is the fourth layer of dielectric board, structure 13 is the fourth layer of prepreg, structure 14 is the sixth layer of metal ground, and structure 15 is the fifth layer of dielectric board. In Fig. 3 (a), structure 16 is the metal ring of the shielding cavity, structure 17 is the metal hole of the shielding cavity, structure 18 is the metal hole of the magnetoelectric dipole, structure 19 is the metal patch of the magnetoelectric dipole, and structure 20 is the metal connection place. In FIG. 3( b ), structure 21 is a coupling slot, structure 22 is a fork-shaped microstrip feeder, and structure 23 is a feeder input hole. In Fig. 3(c), structure 25 is the output hole of the power divider, structure 26 is the input hole of the power divider, and structure 27 is the patch of the second power divider. In FIG. 3( d ), structure 28 is the metal hole of the waveguide cavity, structure 29 is the rectangular coupling patch, structure 30 is the output hole of the waveguide cavity, and structure 31 is the missing part of the upper layer metal. The structure 32 in Fig. 4(a) is a dummy array. The structure 33 in Fig. 4(b) is the grounding point.

Detailed ways

The exploded 3D view of the magnetoelectric dipole antenna array in this embodiment is shown in Figure 1. The antenna works in the W frequency band and consists of 5 layers of dielectric boards and 4 layers of prepreg for bonding. The material of the dielectric board is RO3003, and the relative permittivity is 3. The prepreg material is RLP30 with a relative dielectric constant of 3. The pitch of the antenna elements in the antenna array is 2.4mm. Fig. 2 is a side view of the magnetoelectric dipole antenna array, wherein all the metal formations have a thickness of 0.03mm, the thickness of the first and fifth dielectric plates 2 and 15 is 0.508mm, and the second, third and fourth dielectric plates 6, The thickness of 9 and 12 is 0.254mm, and the thickness of all prepreg layers is 0.111mm.

The top view of the key structure of the magnetoelectric dipole antenna array in this embodiment is shown in Fig. 3 . Figure 3(a) is a top view of the antenna radiation structure without adding dummy elements. The metal ring 16 of the shielding cavity has a width of 0.8mm, and the diameter of the shielding metal hole 17 is 0.5mm. This shielding cavity can reduce the coupling between the antenna array and other components in the MIMO system , and then reduce the deterioration of the coupling to the performance of the antenna, the magnetoelectric dipole metal hole 18, the magnetoelectric dipole metal iron sheet 19, and the metal connection 20 are the parts that constitute the magnetoelectric dipole, and the magnetoelectric dipole metal hole The diameter of 18 is 0.4mm, the side length of magnetoelectric dipole metal patch 19 is 0.8mm, and the metal connection 20 can greatly improve the matching performance of the antenna, and its width is 0.1mm. Fig. 3(b) is a top view of the fork-shaped feeder and the H-shaped coupling slot of the antenna, wherein the width of the coupling slot 21 is 0.1 mm, the length of the extensions on both sides of the H-shape is 0.19 mm, and the overall length of the slot is 0.8 mm. Wherein the width of the fork-shaped opening of the fork-shaped microstrip feeder 22 is 0.82mm, the overall width of the microstrip line is 0.11mm, the cut corner part is a right-angled triangle, and the length of the right-angled side is 0.1mm, and the feeder input hole 23 is a metallized through hole. The diameter of the fork-shaped microstrip feeder 22 is 0.2mm, and it is connected to the output end of the power divider on the lower layer. Its width on one side of the metal pad on the microstrip line layer is 0.1mm. The diameter of the through hole after adding the pad is the same. Through the fork-shaped feeder, the electromagnetic field can be better coupled to the two ends of the H-shaped slot, so that there is a current around the two ends of the H-shaped slot in the slot layer, and then the energy is upward. Coupled to the radiation structure of the antenna, the length of the H-shaped slot affects the length of the current path, which in turn can affect the central operating frequency of the antenna. The part 24 from the metal via to the fork-shaped feeder opening is composed of a metal patch with a length of 0.35mm . Figure 3(c) is a top view of the one-to-two power divider. There are two types of one-to-two power dividers, which respectively play the role of dividing energy into two and two into four. The two power dividers have the same structure and different details. , wherein the power splitter output hole 25 has a diameter of 0.2 mm, which is the output end of the power splitter, and is connected with the input end of the superstructure, and the power splitter input hole 26 has a diameter of 0.2 mm, which is the input end of the power splitter. Connected to the output end of the lower structure, the power divider patch 27 and the two metal pads of the power divider output hole 25 together constitute the microstrip line part of the power divider, and the size of the two power dividers is only in the power divider There are differences in the length and width of the patch 27, the length of the patch 27 of the splitter patch 27 of the one-to-two splitter is 4.8mm and the width is 0.1mm, and the splitter patch 27 of the splitter patch 27 of the splitter is 2.4mm in length , the width is 0.5mm, and the two-stage power divider is cascaded to form a one-point four-power divider. Figure 3(d) is a top view of the waveguide-to-coaxial structure, which is composed of two layers of etched rectangular metal floor patches, some metal holes and a rectangular metal coupling patch, in which the diameter of the waveguide cavity metal hole 28 is 0.2mm , the length of the rectangular coupling patch 29 is 1.5 mm, the width is 0.9 mm, the output hole 30 of the waveguide cavity is connected to the input end of the power divider, and the diameter is 0.2 mm, and the upper and lower metal layers can be seen at the missing part 31 of the upper layer metal The width of the etched part on the patch floor is different. The width of the rectangle etched on the lower metal floor is 1.27mm, and the length is 2.54mm, while the width of the rectangle etched on the upper metal floor is 0.26mm wider than that of the lower layer. The purpose of doing this is because the rectangular cavity will form electromagnetic resonance, which will deteriorate the matching performance of the antenna. Widening the width of the etched rectangle on the upper layer can move this resonance to a lower frequency and improve the matching performance of the antenna array.

A schematic diagram of an antenna dummy array in this embodiment is shown in FIG. 4 . Figure 4(a) is a top view of the radiation structure of the array after adding dummy elements, in which the position of the dummy element array 32 is 1.95mm on both sides of the central array, and the dummy element array only retains the first, second and third layer structures of the original array, because The fork feed structure is grounded, so the metal structure part of the lower layer is omitted. Figure 4(b) is a schematic diagram of the grounding change of the dummy array fork-shaped feeder. The grounding point 33 is a metal through hole with a diameter of 0.2 mm. The length of the part 24 of the shaped feeder opening can be adjusted for its reverse phase, thereby achieving the purpose of adjusting the phase distribution of the antenna front to control the 3dB beamwidth of the horizontal angle.

Fig. 5 shows the horizontal plane gain pattern of the antenna at different lengths from the metal via hole to the fork-shaped feeder opening. It can be seen that as the length of the metal via to the fork-shaped feeder opening 24 becomes longer, The horizontal 3dB beam width of the antenna is also gradually widening, and an appropriate size can be selected according to the needs of the MIMO radar for autonomous driving.

Figure 6 shows the return loss of the antenna as a function of frequency, and includes a variety of situations at different lengths of the part 24 from the metal via to the fork-shaped feeder opening, and the part 24 from the metal via to the fork-shaped feeder opening is The performance of the antenna return loss is less affected, and the antenna array can achieve a return loss of less than 10dB at 74.5-80GHz (or even higher frequencies).

Figure 7 shows the gain pattern of the antenna from the metal via to the fork-shaped feeder opening at 24 = 0.45mm. At this time, the 3dB beamwidth of the antenna in the horizontal plane is -10.38°～9.47°, and in the vertical plane The 3dB beam width is -52.42°～52.37°, which meets the performance requirements of MIMO radar for autonomous driving.

It can realize broadband, high gain, 3dB beamwidth of ±50°～±55° in the horizontal plane, and 3dB beamwidth of ±10° in the vertical plane. It is characterized in that: it is divided into three parts: antenna, power divider, and waveguide to coaxial structure; in that: the antenna part is composed of three layers of PCB boards, the top PCB board is used to realize radiation, the second and third layers of PCB The board is used for coupling and feeding; because: the power splitter part is composed of four-layer PCB boards, and three one-two power splitters are connected to form one-point four-power splitter; because: the waveguide-to-coaxial structure is composed of two-layer PCB boards Composition, its size can be matched with WR-10 waveguide. The antenna structure is composed of improved magnetoelectric dipoles, and the centers of the magnetoelectric dipole radiation patches can improve the impedance matching performance of the antenna and widen the impedance bandwidth of the antenna. There is a surrounding cavity structure composed of rectangular ring patches and metal holes around the magnetoelectric dipole. The surrounding cavity structure can reduce the coupling interference of other components in the MIMO system to the antenna, and reduce the deterioration of antenna performance caused by electromagnetic interference in integrated applications. The magnetoelectric dipole is fed through coupling, and the electromagnetic field is coupled from the fork-shaped microstrip line to the H-shaped slot, and then coupled to the magnetoelectric dipole radiation structure. The impedance matching performance of the antenna can be improved by coupling, and the antenna can be widened. The impedance matching bandwidth of the antenna increases the ability of the antenna to resist the error caused by the tolerance. The magnetoelectric dipole array achieves a 3dB beamwidth of ±10° in the vertical plane by controlling the cell spacing in the vertical direction, which can improve the antenna gain and increase the detection range of the MIMO radar for autonomous driving. The magnetoelectric dipole array adds dummy arrays with adjustable reflection phases on both sides of the array in the horizontal direction, thereby changing the radiation phase distribution of the antenna array, and controlling the 3dB beamwidth in the horizontal direction to ±50°~±55°, increasing the Detection angle of MIMO radar for large autonomous driving. The magnetoelectric dipole is fed by a one-to-four power divider to form a 1×4 array. The one-to-four power divider is composed of three one-to-two power dividers cascaded. The structure of the microstrip line occupies a small horizontal space. For measurement, a waveguide-to-coaxial structure is added to the antenna array, and the waveguide field is converted into a microstrip field and then into a coaxial field through coupling, and the impedance transformation is completed, so that the antenna can complete the measurement.

Claims (2)

1. A magnetoelectric dipole antenna applied to automatic driving radar, the antenna is stacked from bottom to top: the first layer of metal ground, the first layer of dielectric board, the second layer of metal ground, the first layer of prepreg, the third layer The first layer of metal ground, the second layer of dielectric board, the second layer of prepreg, the fourth layer of metal ground, the third layer of dielectric board, the third layer of prepreg, the fifth layer of metal ground, the fourth layer of dielectric board, the fourth layer of prepreg, the fourth layer of Six layers of metal ground, fifth layer of dielectric board; The metal ring of the shielding cavity is set on the upper surface of the dielectric plate of the fifth layer. The metal ring of the shielding cavity is a ring-shaped patch, and a circle of metal holes of the shielding cavity is evenly arranged at the corresponding position of the metal ring of the shielding cavity, which is used to connect the metal ring of the shielding cavity and the sixth layer. Metal ground; multiple groups of magnetoelectric dipole metal patches are set in the annular structure of the metal ring of the shielding cavity, each group includes 4 patches in an array of 2×2, and the opposite corners of the 4 patches are connected to each other, each A magnetoelectric dipole metal hole is set at the corresponding position of the patch, which is used to connect the patch and the sixth layer of metal ground; A coupling seam is opened on the metal ground of the sixth layer, and a group of magnetoelectric dipole metal patches corresponds to a coupling seam; A fork-shaped microstrip feeder is provided on the upper surface of the fourth layer dielectric plate, and one coupling slot corresponds to a fork-shaped microstrip feeder. The fork-shaped microstrip feeder includes a U-shaped coupling area and a U-shaped bottom located in the opposite direction to the U-shaped opening. In the raised feeding area, the two ends of the coupling slit just overlap with the two arms of the U-shaped structure of the coupling area, and the corresponding position of the feeding area is provided with a feeder input hole for connecting the second power divider located on the upper surface of the third layer dielectric board. There are metal holes for passing through the feeder input hole on the fifth layer of metal ground, so as to ensure that the feeder input hole does not contact the fifth layer of metal ground; A plurality of second power divider patches on the upper surface of the third layer dielectric board, each output hole of the second power divider patch is correspondingly connected to a feeder input hole; A first power divider patch is provided on the upper surface of the second layer dielectric board, and each output hole of the first power divider patch is connected to an input hole of a second power divider patch, and is not connected with the first power divider patch. Four-layer metal ground contact; the first power divider patch only includes one input hole; The metal ground of the first layer and the metal ground of the second layer are provided with a square hollow area, and a circle of waveguide cavity metal holes is arranged around the hollow area, and the metal hole of the waveguide cavity communicates with the metal ground of the first layer and the metal ground of the second layer; The size of the hollow area on the second layer of metal ground is larger than that on the first layer of metal ground; a rectangular coupling patch is arranged in the hollow area on the second layer of metal ground, and a waveguide cavity output hole is set on the edge of the rectangular coupling patch. The cavity output hole is connected to the patch input hole of the first power divider, and is not in contact with the metal ground of the third layer; The area enclosed by the metal hole of the waveguide cavity is the input of the magnetoelectric dipole antenna. 2. A kind of magnetoelectric dipole antenna that is applied to automatic driving radar as claimed in claim 1, is characterized in that, described multiple groups of magnetoelectric dipole metal patches are arranged in a row, and the row of magnetoelectric dipoles A row of dummy element arrays are respectively arranged on both sides of the sub-metal patch, and the structure of the dummy element array is the same as that of the magnetoelectric dipole metal patch, and each magnetoelectric dipole metal patch in the dummy element array corresponds to a coupling slot, and then Corresponds to a fork-shaped microstrip feeder, but the feeder input hole of the feeder area of the fork-shaped microstrip feeder corresponding to the dummy array is directly connected to the fifth-layer metal ground.

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