CN112968290A - Low-sidelobe antenna applied to vehicle communication system - Google Patents

Abstract

The invention provides a low sidelobe antenna applied to a vehicle communication system. The low-sidelobe antenna comprises an antenna body and a coaxial feed terminal, wherein the antenna body is made of metal, the antenna body is defined to have an up-down direction, the antenna body is sequentially provided with a feed cavity and a resonant cavity from bottom to top, the antenna body is also provided with a feed gap communicated with the feed cavity and the resonant cavity, and a plurality of radiation gaps communicated with the resonant cavity and the outside, and the radiation gaps are all positioned on the upper surface of the antenna body and are symmetrically distributed relative to the feed gap; the coaxial feed terminal is arranged through the antenna body and extends into the feed cavity. The technical scheme of the invention can ensure that the low side lobe antenna does not need to adopt a power divider for feeding, thereby simplifying the structure of the low side lobe antenna; and the size and the position of the radiation gaps are simply adjusted, so that the non-uniform amplitude can be easily obtained while the in-phase excitation of the plurality of radiation gaps is kept.

Description

Low-sidelobe antenna applied to vehicle communication system

Technical Field

The invention belongs to the field of antennas, and particularly relates to a low-sidelobe antenna applied to a vehicle communication system.

Background

The low sidelobe antenna has the advantages of reducing interference generated by the sidelobe and further improving the resolution capability of the main lobe, so that the low sidelobe antenna has a good characteristic of improving the communication quality between the vehicle and the infrastructure. The non-uniform amplitude distribution is a general and effective method for designing low-sidelobe antenna arrays, and the low-sidelobe antennas in the related art are basically fed through a power divider to obtain in-phase and non-uniform amplitude excitation. However, the structure of such low sidelobe antennas is complicated due to the use of the power divider.

Disclosure of Invention

The invention aims to provide a low sidelobe antenna applied to a vehicle communication system and aims to simplify the structure of the low sidelobe antenna.

To solve the above technical problem, the present invention is implemented as a low sidelobe antenna, including: the antenna comprises an antenna body, wherein the antenna body is made of metal, the antenna body is defined to have an up-down direction, the antenna body is sequentially provided with a feed cavity and a resonant cavity from bottom to top, the antenna body is also provided with a feed gap for communicating the feed cavity with the resonant cavity, and a plurality of radiation gaps for communicating the resonant cavity with the outside, and the plurality of radiation gaps are all positioned on the upper surface of the antenna body and are symmetrically distributed around the feed gap; and

the coaxial feed terminal penetrates through the antenna body and extends into the feed cavity.

In an embodiment of the present invention, the antenna body is further defined to have a length direction and a width direction perpendicular to the up-down direction, and the feed slot and each of the radiation slots are extended and opened along the length direction of the antenna body;

the plurality of radiation slots are distributed at intervals along the length direction of the antenna body to form a radiation slot group, and the antenna body is provided with at least one radiation slot group.

In an embodiment of the present invention, the number of the radiation gap groups is one, and one radiation gap group includes four radiation gaps;

the center line of the antenna body in the width direction of the antenna body and the center line of the feed gap in the width direction of the antenna body are located in the same vertical plane, and the four radiation gaps are symmetrically distributed relative to the center line of the antenna body in the width direction of the antenna body.

In an embodiment of the present invention, a length of the radiation slot close to a center line of the antenna body in a width direction thereof, of two radiation slots located at one side of the antenna body, is defined as L1, and a length of the radiation slot far from the center line of the antenna body in the width direction thereof is defined as L2, and a relationship is satisfied: 4/5 is less than or equal to L2/L1 is less than or equal to 6/5.

In an embodiment of the present invention, a width of one of the two radiation slots located on one side of the antenna body, which is far from a center line of the antenna body in a width direction thereof, is defined as W2, and a relationship is satisfied: 1/3 is not less than W2/L2 is not less than 3/4;

and/or, defining a distance D2 between a center line of the radiation slot, which is far away from the center line of the antenna body in the width direction, of the two radiation slots located at one side of the antenna body and the center line of the antenna body in the width direction, and satisfying a relationship: 3 is less than or equal to D2/L2 is less than or equal to 19/4.

In an embodiment of the present invention, the number of the radiation gap groups is one, and one radiation gap group includes seven radiation gaps;

the center line of the antenna body in the width direction and the center line of the feed slot in the width direction are located in the same vertical plane, the center line of the middle radiation slot in the width direction of the seven radiation slots and the center line of the antenna body in the width direction are located in the same vertical plane, and the rest radiation slots are symmetrically distributed around the center line of the antenna body in the width direction.

In an embodiment of the present invention, the lengths of the seven radiation slits are set to be equal;

or the lengths of the seven radiation gaps are reduced in the direction from the center of the antenna body to the two ends of the antenna body.

In an embodiment of the present invention, the number of the radiation slot groups is five, the five radiation slot groups are distributed at intervals along a width direction of the antenna body, and each radiation slot group includes four radiation slots;

the center line of the antenna body in the width direction and the center line of the antenna body in the length direction are respectively positioned in the same vertical plane with the center line of the feed gap in the width direction and the center line of the feed gap in the length direction;

the middle radiation slot group in the five radiation slot groups is positioned on the central line of the antenna body in the length direction, and the rest radiation slot groups are symmetrically distributed relative to the central line of the antenna body in the length direction; the four radiation slots in each radiation slot group are symmetrically distributed about the center line of the antenna body in the width direction of the antenna body.

In an embodiment of the present invention, the antenna body includes:

the resonance box is internally provided with a resonance groove, the notch of the resonance groove is arranged upwards, and the lower surface of the resonance box is provided with a feed gap communicated with the resonance groove;

the feed box is internally provided with a feed groove, the feed groove is connected to the lower surface of the resonance box and covers the outer side of the feed gap, and the feed groove and the lower surface of the resonance box enclose to form the feed cavity; and

the box cover plate is connected to the upper surface of the resonance box and covers the notch of the resonance groove, the box cover plate and the resonance groove are enclosed to form the resonance cavity, and the box cover plate is provided with the radiation gap communicated with the feed groove; the coaxial feed terminal penetrates through the feed box and extends into the feed slot.

According to the technical scheme, the cavity membrane formed in the resonant cavity of the antenna body of the low-sidelobe antenna can be excited by the feed gap perpendicular to the direction of the electric field, and then the plurality of radiation gaps are directly excited through the cavity membrane formed in the resonant cavity. At this time, compared with the low-sidelobe antenna in the prior art that the structure of the low-sidelobe antenna is complicated by feeding through the power divider to obtain in-phase and non-uniform amplitude excitation, the low-sidelobe antenna in the scheme does not need to use the power divider for feeding, so that the structure of the low-sidelobe antenna is simplified. In addition, the structure of the low-sidelobe antenna in the scheme is arranged, so that the non-uniform amplitude can be obtained easily while the in-phase excitation of a plurality of radiation gaps is kept only by simply adjusting the size and the position of the radiation gaps. In addition, the antenna body of the low-sidelobe antenna in the scheme is made of metal, so that the low-sidelobe antenna has the advantages of high gain, high efficiency, high power processing capacity and the like, and the transmission effect of the low-sidelobe antenna on signals is favorably improved.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of a low sidelobe antenna of the present invention;

fig. 2 is a top view and a side view of the low sidelobe antenna of fig. 1;

fig. 3 is a schematic diagram of the electric field distribution in the resonant cavity of the low sidelobe antenna in fig. 1;

fig. 4 is a schematic diagram of the electric field distribution in the radiation slot of the low sidelobe antenna of fig. 1;

fig. 5 is a schematic view from another perspective of the low sidelobe antenna of fig. 1;

FIG. 6 is a graph of simulation results of the amplitude of the low sidelobe antenna of FIG. 1 versus varying L2;

fig. 7 is a graph showing simulation results of the phase of the low sidelobe antenna of fig. 1 with respect to varying L2;

FIG. 8 is a graph of simulation results of the amplitude of the low sidelobe antenna of FIG. 1 versus varying D2 and W2;

FIG. 9 is a graph showing simulation results of the phase of the low sidelobe antenna of FIG. 1 with respect to varying D2 and W2;

FIG. 10 is a diagram illustrating the results of the calculation of the quaternary Chebyshev array of the low sidelobe antenna of FIG. 1 under different amplitude vectors;

fig. 11 is a graphical representation of the results of numerical simulations of the XZ plane radiation pattern of the quaternary array of the low sidelobe antenna of fig. 1;

FIG. 12 is a graph showing results of a simulation of S11 and the implementation of gain for two quaternary low sidelobe antenna arrays of type I and type II;

FIG. 13 is a diagram showing simulation results of normalization directions of two quaternary low-sidelobe antenna arrays of type I and type II on an XZ plane;

fig. 14 is a schematic structural diagram of another embodiment of the low sidelobe antenna of the present invention;

fig. 15 is a graph showing the results of amplitude and phase simulations when the respective radiating slots of the low sidelobe antenna of fig. 14 have the same length;

fig. 16 is a graph showing the results of amplitude and phase simulations when the individual radiating slots of the low sidelobe antenna of fig. 14 have different lengths;

FIG. 17 is a graph showing results of simulation of S11 and implementation gain for two seven-element low sidelobe antenna arrays of type III and type IV;

FIG. 18 is a diagram showing the results of a simulation of two types of type III and type IV seven-element low sidelobe antenna arrays on the XZ plane with normalized direction;

FIG. 19 is a schematic structural diagram of another embodiment of a low sidelobe antenna of the present invention

Fig. 20 is a top view of the low sidelobe antenna of fig. 19;

FIG. 21 is a schematic diagram of the electric field distribution within the resonant cavity and radiation slot of the low sidelobe antenna of FIG. 19

Fig. 22 is a graph showing simulation results of the low sidelobe antenna in fig. 19 for achieving gain and radiation efficiency

FIG. 23 is a graph showing simulation and measurement results of return loss and realized gain of the low sidelobe antenna of FIG. 19;

fig. 24 is a graph showing simulation and measurement results of the radiation efficiency of the low sidelobe antenna in fig. 19;

FIG. 25 is a schematic diagram of the lower sidelobe antenna of FIG. 19 simulated and measured at 3.44GHz in the XZ plane;

fig. 26 is a schematic diagram of the lower sidelobe antenna of fig. 19 simulated and measured at 3.44GHz in the YZ plane direction.

In the drawings, each reference numeral denotes: 10-antenna body, 11-feed cavity, 12-resonant cavity, 13-feed gap, 14-radiation gap, 15-resonant box, 16-feed box, 17-box cover plate and 30-coaxial feed terminal.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention provides a low sidelobe antenna applied to a vehicle communication system.

Referring to fig. 1 to 5, in an embodiment of the present invention, the low-sidelobe antenna includes an antenna body 10 and a coaxial feeding terminal 30, the antenna body 10 is made of metal, the antenna body 10 is defined to have an up-down direction, the antenna body 10 is sequentially provided with a feeding cavity 11 and a resonant cavity 12 from bottom to top, the antenna body 10 is further provided with a feeding gap 13 communicating the feeding cavity 11 and the resonant cavity 12, and a plurality of radiation gaps 14 communicating the resonant cavity 12 and the outside, the plurality of radiation gaps 14 are all located on an upper surface of the antenna body 10 and are symmetrically distributed about the feeding gap 13; the coaxial feeding terminal 30 is disposed through the antenna body 10 and extends into the feeding cavity 11.

The feeding cavity 11 of the antenna body 10 may be configured to form a waveguide transition section with the coaxial feeding terminal 30, and feed a waveguide signal into the resonant cavity 12 through the feeding slot 13. The resonant cavity 12 may be used to resonate a signal fed thereto and radiate the signal to the outside through the radiation slit 14. The material of the antenna body 10 may be exemplified by: iron, copper, silver, aluminum, or the like, and the specific material used for the antenna body 10 is not limited in the present application. In addition, as the fifth generation (5G) communication technology is emerging nowadays, and the commercial application of 5G communication in the sub-6G frequency band is starting, the low sidelobe antenna in the present application can be used for 5G-V2X communication, i.e. the frequency band of 3.3 GHZ-3.8 GHZ can be adopted to cater for the emerging wireless system, and it can help C-V2X to improve road safety, thereby improving signal transmission between vehicles or between vehicles and other things.

The cavity membrane formed in the resonant cavity 12 of the antenna body 10 of the low sidelobe antenna according to the technical scheme of the present invention can be excited by the feeding gap 13 perpendicular to the electric field direction, and then the plurality of radiation gaps 14 are directly excited by the cavity membrane formed in the resonant cavity 12. At this time, compared with the low-sidelobe antenna in the prior art that the structure of the low-sidelobe antenna is complicated by feeding through the power divider to obtain in-phase and non-uniform amplitude excitation, the low-sidelobe antenna in the scheme does not need to use the power divider for feeding, so that the structure of the low-sidelobe antenna is simplified. Moreover, the low sidelobe antenna in the present solution is structurally configured, so that the non-uniform amplitude can be obtained easily while keeping the plurality of radiation slots 14 excited in phase by simply adjusting the size and position of the radiation slot 14. In addition, the antenna body 10 of the low sidelobe antenna in the scheme is made of metal, so that the low sidelobe antenna has the advantages of high gain, high efficiency, high power processing capability and the like, and the transmission effect of the low sidelobe antenna on signals is favorably improved.

Referring to fig. 1, in an embodiment of the present invention, the antenna body 10 is defined to further have a length direction and a width direction perpendicular to the up-down direction, and the feeding slot 13 and each of the radiation slots 14 are extended along the length direction of the antenna body 10; the plurality of radiation slots 14 are distributed at intervals along the length direction of the antenna body 10 to form one radiation slot group, and the antenna body 10 is provided with at least one radiation slot group.

It can be understood that the plurality of radiation slots 14 in the radiation slot group are distributed at intervals along the length direction of the antenna body 10, so that the plurality of radiation slots 14 are relatively regular, and the resonant cavity 12 of the low-sidelobe antenna can have the same phase excitation for each radiation slot 14. Meanwhile, the plurality of radiation slots 14 can be machined by the same machining tool in the same process, so that the convenience of machining and manufacturing the low-sidelobe antenna is improved. Of course, the present application is not limited thereto, and in other embodiments, the plurality of radiation slots 14 may be alternatively staggered along the length direction of the antenna body 10, or may be arranged at random intervals.

Referring to fig. 1 and fig. 2 in combination, in an embodiment of the present invention, the number of the radiation slot groups is one, and one radiation slot group includes four radiation slots 14; the center line of the antenna body 10 in the width direction thereof and the center line of the feed slot 13 in the width direction thereof are located in the same vertical plane, and the four radiation slots 14 are symmetrically distributed with respect to the center line of the antenna body 10 in the width direction thereof.

It will be appreciated that the four radiating slots 14 are symmetrically distributed about the centre line of the antenna body 10 such that the electromagnetic field within the four radiating slots 14 is also symmetrical about the centre line of the antenna body 10 and corresponds to radiation such that the amplitude and phase excitation of the four radiating slots 14 is symmetrical. At this time, in the process of changing the size and position of the radiation slot 14 to adjust the amplitude ratio of the low side lobe antenna, the equal phase of each radiation slot 14 is self-maintained without an additional feeding structure. Of course, it should be noted that the present application is not limited thereto, and in other embodiments, one radiation slot group may also include three, five or more radiation slots 14.

Referring to fig. 2, in an embodiment of the present invention, a length of a radiation slot 14 close to a center line of the antenna body 10 in a width direction of the antenna body 10 among two radiation slots 14 located at one side of the antenna body 10 is defined as L1, and a length of a radiation slot 14 far from the center line of the antenna body 10 in the width direction is defined as L2, which satisfies a relationship: 4/5 is less than or equal to L2/L1 is less than or equal to 6/5.

Wherein, L1 can be 20mm, L2 can be 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm or 24mm, etc. Fig. 5 shows a simulation model for extracting the element amplitude and phase, the simulation results are shown in fig. 6 and 7, and the size information of each radiation slit 14 is provided in fig. 1 and 2. Also, since the extracted amplitude and phase are symmetrical along the x-axis (i.e., the length direction of the antenna body 10), only the parameters of | S21| and | S31| of two radiation slots 14 located on one side of the y-axis among the four radiation slots 14 are discussed (| S21| corresponds to the radiation slot 14 close to the center line of the antenna body 10 in the width direction thereof, | S31| corresponds to the radiation slot 14 far from the center line of the antenna body 10 in the width direction thereof). As can be seen from fig. 6, the increase in the length (L2) of the radiation slot 14 away from the center line of the antenna body 10 in the width direction thereof increases the magnitude of | S31 |. It follows that increasing the length of the radiation gap 14 increases the radiation energy of the cavity film formed within the resonant cavity 12, thereby decreasing the amplitude ratio of S21/S31. Fig. 7 shows that the change in the length of the radiation slot 14 has very little influence on the phase difference between two radiation slots 14 located on the center line side in the width direction of the antenna body 10 among the four radiation slots 14. This is because the electromagnetic field in the resonant cavity 12 propagates along the z-axis (i.e. the up-down direction of the antenna body 10), and the radiation slits 14 are located on the wave fronts at the same distance along the propagation direction, so that the same phase of the radiation slits 14 is realized, and the requirement that the low-sidelobe array design adopting non-uniform amplitude distribution needs in-phase excitation is met. That is, the structural arrangement of the low sidelobe antenna in the present application can easily obtain a non-uniform amplitude distribution by simply changing the size of the slit. Also, as can be seen from fig. 6 and 8, the relationship is satisfied at L1 and L2: 4/5L 2/L1 6/5, the low side lobe antenna has relatively small amplitude ratio, so that the low side lobe antenna has relatively high side lobe level and can obtain large gain. Of course, the present application is not limited thereto, and in other embodiments, L1 may be 16mm, 17mm, 18mm, 19mm, 21mm, or 22mm, etc., which may ensure that 4/5 ≦ L2/L1 ≦ 6/5.

In an embodiment of the present invention, the width of the radiation slot 14 away from the center line of the antenna body 10 in the width direction, of the two radiation slots 14 located on one side of the antenna body 10, is defined as W2, and the relationship: 1/3 is not less than W2/L2 is not less than 3/4. In an embodiment of the present invention, a distance between a center line of the radiation slot 14, which is far from a center line of the antenna body 10 in a width direction thereof, of the two radiation slots 14 located at one side of the antenna body 10 and the center line of the antenna body 10 in the width direction thereof is defined as D2, satisfying a relationship: 3 is less than or equal to D2/L2 is less than or equal to 19/4.

Wherein, L2 can be 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm or 24mm, etc., W2 can be 8mm, 10mm or 12mm, etc., L2 can be 72mm, 73mm, 74mm, 75mm or 76mm, etc. Fig. 8 and 9 show the relationship of the amplitude ratio (| S21|/| S31|) between two radiation slots 14 located on the side of the center line in the width direction of the antenna body 10 among the four radiation slots 14 with respect to the pairs L2, W2, and D2, which are parameters related to the radiation slots 14 located away from the center line of the antenna body 10 in the width direction thereof. The data shows that the amplitude ratio decreases as the length or width of the radiation slot 14 away from the center line of the antenna body 10 in its width direction increases. The larger the distance between the center line of the antenna body 10 in the width direction thereof and the center line of the antenna body 10 in the width direction, that is, the larger D2, the smaller the excitation amplitude of the radiation slot 14, so that the amplitude ratio ((| S21|/| S31|)) increases. The influence of the length and width of the radiation slot 14 on the amplitude ratio is greater than the influence of the distance between the radiation slot 14 and the center line of the antenna body 10 in the width direction on the amplitude ratio. Fig. 9 also shows that, in the tuning range (from 1:1 to 8:1) where the amplitude ratio is so large, the phase difference between two radiation slots 14 on the side of the center line in the width direction of the antenna body 10 among the four radiation slots 14 is less than 3 degrees. It can be seen that when the size and position of the radiation slits 14 are adjusted, a non-uniform amplitude distribution can be obtained, while the in-phase excitation of the elements remains almost unchanged. In addition, parameters similarly belonging to the radiation slot 14 near the center line of the antenna body 10 in the width direction thereof, i.e., L1, W1, and D1, can also be used for modifying the amplitude ratio with reference to the above adjustment.

For practical designs of low sidelobe antennas it is the amplitude ratio between the elements that corresponds to the implementation of the low sidelobe, and different sidelobes are required for different sidelobe levels. The Array Factor (AF) and amplitude vector for the 2n and 2n +1 cell arrays according to the Chebyshev array are as follows:

V_2n＝[α_n … α₂ α₁ α₁ α₂ … α_n] (3)

V_2n+1＝[α_n+1 … α₂ α₁ α₂ … α_n+1] (4)

where an represents the amplitude of the elements, k represents the propagation constant, and d represents the distance between the elements.

The side lobe level of the array factor of the quad array calculated with (1) depends on the amplitude ratio a1/a2, which is equivalent to the ratio of | S21|/| S31| shown in FIG. 8. While the amplitude vector for a quad-array with side-lobe levels of-20 dB/-25dB/-30dB is given in (5), where the amplitude a2 is normalized to 1. The calculation results are shown in fig. 10. It can be seen that in an actual slot array design, by varying the size of the radiating slot 14 and the distance between the radiating slot 14 and the center line of the antenna body 10, different amplitude ratios can be obtained, as shown in fig. 8). In addition, FIG. 10 shows that different a1/a2 ratios produce different side lobe levels. Thus, by modifying the size and position of the radiation slits 14, different side lobe levels will be obtained. Fig. 11 shows a simulated radiation pattern with varying L2 functions. It can be seen that a larger L2 produces a higher side lobe level because a larger L2 results in a lower amplitude ratio (as shown in fig. 8). It can be seen that the low sidelobe antenna proposed in the present application can be used to design different sidelobe level antennas. Here, two arrays with side lobe levels of-20 dB and-30 dB, referred to as Type-I and Type-II, respectively, were studied to show the feasibility of designing antennas with different side lobe levels. The magnitude vectors for type I and type II are [1, 1.735, 1.735, 1] and [1, 2.331, 2.331, 1], respectively. These values are then modified to match the given ratio using the previous extraction methods shown in fig. 8 and 9. The gain achieved is shown in fig. 12 and the normalized radiation pattern is shown in fig. 13. Both have good impedance matching at the operating frequency. For a specified-20 dB sidelobe level, the analog sidelobe is about-22 dB and the gain is 11.7dBi, while for a specified-30 dB rejection level, the analog sidelobe is about-30 dB and the gain is 11.3dBi, and the results are all closer. Thus, a trade-off between suppression level and radiation gain can be made, which also indicates that the low side lobe antennas in this application have flexibility in designing antenna arrays with variable side lobe levels, table one providing their final size.

Watch 1

Referring to fig. 14, in an embodiment of the present invention, the number of the radiation slot groups is one, and one radiation slot group includes seven radiation slots 14; the center line of the antenna body 10 in the width direction thereof and the center line of the feed slot 13 in the width direction thereof are located in the same vertical plane, the center line of the central radiation slot 14 in the width direction thereof and the center line of the antenna body 10 in the width direction thereof among the seven radiation slots 14 are located in the same vertical plane, and the remaining radiation slots 14 are symmetrically distributed with respect to the center line of the antenna body 10 in the width direction thereof.

Since the conventional power divider-based feeding low sidelobe antenna array is generally limited in designing an even number of elements, the structure of the low sidelobe antenna in the present application can be applied to an odd number of elements, and one radiation slot group as described above includes seven radiation slots 14. Where fig. 14 shows a top view with label dimensions, the other structures and dimensions are the same as for the quad-array shown in fig. 1. Fig. 15 and 16 show simulated amplitude and phase for a low sidelobe antenna with seven radiating slots 14: if the seven radiation slots 14 are provided with equal lengths, for example, L1-20, L2-20, L3-20, and L4-20 (all in mm), all the radiation slots 14 are fed in phase, but have different amplitude excitations, with an amplitude vector of [1, 2.89, 4.87, 6.4, 4.87, 2.89, 1] (as shown in fig. 12). When the lengths of the seven radiation slots 14 decrease in the direction from the center of the antenna body 10 to both ends thereof, if L1-20, L2-22, L3-24, and L4-26 (all in mm), the phase excitations of the seven radiation slots 14 are different but within 10 degrees, and the amplitude vector is [1, 1.75, 1.8, 1.68, 1.8, 1.75, 1 ]. It follows that the phase difference of the respective radiation slits 14 is small in the case where the amplitude ratio varies largely. Therefore, a low sidelobe antenna can be realized by appropriately modifying the size of the radiation slot 14. Similarly, to illustrate the feasibility of designing antenna arrays with different sidelobe levels for the low sidelobe antenna in this application, the present application proposes a seven-element antenna array with two sidelobe levels of-20 dB and-30 dB, respectively, referred to as type iii and type iv antennas. Their amplitude vectors are [1, 1.28, 1.68, 0.92, 1.68, 1.28, 1] and [1, 2.15, 3.31, 1.89, 3.31, 2.15, 1], respectively. The amplitude of the radiation slit 14 is then modified to match a given ratio using the previously extracted method shown in figure 6. The resulting | S11| and the gain achieved are shown in fig. 17, both of which have good impedance matching at the operating frequency, and the normalized radiation pattern is shown in fig. 18. For a specified-20 db sidelobe level, the analog sidelobe is about-22 db, and the gain is 13.3 dbi; while for a given-30 db suppression level the analog sidelobe is about-32 db and the gain is 12.7dbi, the results are all closer together, which further demonstrates the flexibility of the low sidelobe antenna of this application in designing antenna arrays with variable sidelobe levels. Table two provides their final dimensions.

Watch two

Referring to fig. 19, in an embodiment of the present invention, the number of the radiation slot groups is five, the five radiation slot groups are distributed at intervals along the width direction of the antenna body 10, and each radiation slot group includes four radiation slots 14; the center line of the antenna body 10 in the width direction and the length direction thereof is respectively positioned in the same vertical plane with the center line of the feed slot 13 in the width direction and the length direction thereof; the middle radiation slot group of the five radiation slot groups is located on the central line of the antenna body 10 in the length direction, and the rest radiation slot groups are symmetrically distributed around the central line of the antenna body 10 in the length direction; the four radiation slots 14 in each radiation slot group are symmetrically distributed about the center line of the antenna body 10 in the width direction thereof.

It will be appreciated that the number of radiation slot groups is five, each radiation slot group comprising an arrangement of four radiation slots 14 forming a 5 x 4 element antenna array. At this time, low side lobe levels can be realized on both the XZ plane and the YZ plane to improve the gain and radiation efficiency of the antenna. The structure of the antenna array of 5 × 4 elements is shown in fig. 19 and 20, i.e., the antenna has four columns and five rows of elements on the x-axis and y-axis, respectively. The slots are arranged symmetrically along the x and y axes and have symmetrical phase and amplitude excitation around the origin (the point where the center line of the antenna body 10 in the length direction and the center line in the width direction intersect). Thus, the same number of radiation slots 14 shown in fig. 20 have the same amplitude and phase and excitation. The radiation slit 14 has the size Li and Wi, where i ═ 1, 2, 3, 4, 5, 6, which is the label shown in fig. 20. The electric fields inside the resonant cavity 12 and across the radiation slot 14 are shown in fig. 21. It can be seen that in TE101 cavity film mode operation of the antenna within the resonant cavity 12, all slots have electric fields in the same direction as the TE101 mode electric fields. Thus, all radiation slots 14 are directly fed by the cavity mode TE 101. The goal is to achieve 20dB sidelobe suppression in both the XZ plane and the YZ plane. The amplitude vectors for the four elements on the x-axis and the five elements on the y-axis are [1, 1.736, 1.736, 1] and [1.035, 1.664, 1, 1.664, 1.035], respectively. While the amplitude vector for the 5 x 4 array is given in equation (6), where four elements in each row (x-axis) should match the amplitude vector [1, 1.736, 1.736, 1] and five columns of elements in each (y-axis) should match the amplitude vector [1.035, 1.664, 1, 1.664, 1.035 ]. The required amplitude ratio can be obtained by appropriately sizing the slots. After adjustment and optimization, a 5 x 4 plane antenna array is obtained, the analog side lobe level is-23 dB on an XZ plane, and the analog side lobe level is-20 dB on a YZ plane. As shown in fig. 22, the maximum realized gain was 18.3dBi and the simulated radiation efficiency was 97.4%.

Further verifying the above results, the proposed 5 x 4 antenna array may be fabricated using silver plated lossy copper and based on a Computer Numerical Control (CNC) process. The results of comparison between the simulation results and the measurement results are plotted in fig. 23, 24, 25, and 26. The results were: the return loss measured at 3.44GHz was 25dB, and the maximum gain and radiation efficiency were 18.2dBi and 94%, respectively. It can be seen that the side lobe levels in the XZ plane and the YZ plane are better than-20 dB on average. While the cross-polarization (X-pol) in the XZ plane and YZ plane is-42 dB and-43 dB, respectively. Due to the purely directional field distribution of the TE101 mode, there is no field component in the orthogonal direction, so the degree of cross-polarization of the two is relatively low. The measured radiation pattern closely matched the simulated radiation pattern, with minor differences mainly due to solder discontinuities between the SMA and the expansion probe and conductor losses from the cavity. That is, the 5 × 4 antenna array structure in the present application has the advantages of simple structure, high efficiency, high gain, small side lobe, small cross polarization, and the like. It should be noted that, of course, the present application is not limited thereto, and in other embodiments, the low sidelobe antenna in the present application may also include three radiation slot groups, four radiation slot groups, six radiation slot groups, or more radiation slot groups. And the number of each radiation slot group may include three radiation slots 14, five radiation slots 14, or more radiation slots 14, etc.

Referring to fig. 1, in an embodiment of the present invention, an antenna body 10 includes a resonance box 15, a feeding box 16 and a box cover 17, a resonance slot is formed in the resonance box 15, a notch of the resonance slot is disposed upward, and a feeding gap 13 communicated with the resonance slot is disposed on a lower surface of the resonance box 15; a feed slot is formed in the feed box 16, the feed slot is connected to the lower surface of the resonance box 15 and covers the outer side of the feed gap 13, and the feed slot and the lower surface of the resonance box 15 enclose to form a feed cavity 11; the box cover plate 17 is connected to the upper surface of the resonance box 15 and covers the notch of the resonance groove, the box cover plate 17 and the resonance groove enclose to form the resonance cavity 12, and the box cover plate 17 is provided with a radiation gap 14 communicated with the feed groove; the coaxial feed terminal 30 is disposed through the feed box 16 and extends into the feed slot.

It can be understood that the antenna body 10 is composed of the resonance box 15, the feeding box 16 and the box cover plate 17, so that the antenna body 10 can be integrally formed after being separately processed and formed, and thus the complexity of processing for forming the feeding cavity 11 and the resonance cavity 12 is simplified, and the convenience of forming and manufacturing the antenna body 10 is improved. The resonance box 15, the feeding box 16 and the box cover plate 17 can be detachably connected, so that the resonance box, the feeding box 16 and the box cover plate 17 can be detached to improve the convenience of maintenance and replacement when the resonance box is damaged or the internal coaxial feeding terminal 30 is damaged. Specifically, the resonance box 15 and the feeding box 16 may be connected by screws, and the resonance box 15 and the box cover 17 may also be connected by screws. At this time, since the screw connection has the advantages of simplicity and reliability, it is possible to improve the assembling efficiency among the resonance box 15, the feed box 16, and the box cover 17 while ensuring the stability of the connection among them. Of course, the present application is not limited thereto, and in other embodiments, the resonant box 15 and the feeding box 16, and the resonant box 15 and the box cover 17 may be connected by a snap-fit connection, or may be directly fixed by welding. In addition, the projections of the resonant box 15, the feeding box 16 and the box cover 17 on the horizontal plane may be square, so that the shapes of the resonant box 15, the feeding box 16 and the box cover 17 are regular, and the convenience of the antenna body 10 in molding and manufacturing is further improved.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (9)

1. A low sidelobe antenna for use in a vehicle communication system, comprising:

the antenna comprises an antenna body, wherein the antenna body is made of metal, the antenna body is defined to have an up-down direction, the antenna body is sequentially provided with a feed cavity and a resonant cavity from bottom to top, the antenna body is also provided with a feed gap for communicating the feed cavity with the resonant cavity, and a plurality of radiation gaps for communicating the resonant cavity with the outside, and the plurality of radiation gaps are all positioned on the upper surface of the antenna body and are symmetrically distributed around the feed gap; and

the coaxial feed terminal penetrates through the antenna body and extends into the feed cavity.

2. The low sidelobe antenna for use in a vehicle communication system according to claim 1, wherein said antenna body is defined to have a length direction and a width direction perpendicular to the up-down direction, said feed slot and each of said radiation slots being formed to extend in the length direction of said antenna body;

the plurality of radiation slots are distributed at intervals along the length direction of the antenna body to form a radiation slot group, and the antenna body is provided with at least one radiation slot group.

3. The low sidelobe antenna for use in a vehicle communication system according to claim 2, wherein said number of said radiation slot groups is one, and one of said radiation slot groups includes four of said radiation slots;

the center line of the antenna body in the width direction of the antenna body and the center line of the feed gap in the width direction of the antenna body are located in the same vertical plane, and the four radiation gaps are symmetrically distributed relative to the center line of the antenna body in the width direction of the antenna body.

4. The low sidelobe antenna applied to a vehicle communication system according to claim 3, wherein a length of said radiation slot close to a center line of said antenna body in a width direction thereof out of two said radiation slots located at one side of said antenna body is defined as L1, a length of said radiation slot far from a center line of said antenna body in a width direction thereof is defined as L2, and a relationship is satisfied: 4/5 is less than or equal to L2/L1 is less than or equal to 6/5.

5. The low sidelobe antenna applied to a vehicle communication system according to claim 4, wherein a width of said radiation slot, which is distant from a center line of said antenna body in a width direction thereof, of two said radiation slots located at one side of said antenna body is defined as W2, satisfying a relation: 1/3 is not less than W2/L2 is not less than 3/4;

and/or, defining a distance D2 between a center line of the radiation slot, which is far away from the center line of the antenna body in the width direction, of the two radiation slots located at one side of the antenna body and the center line of the antenna body in the width direction, and satisfying a relationship: 3 is less than or equal to D2/L2 is less than or equal to 19/4.

6. The low sidelobe antenna for use in a vehicle communication system according to claim 2, wherein said number of said radiation slot groups is one, and one of said radiation slot groups includes seven of said radiation slots;

the center line of the antenna body in the width direction and the center line of the feed slot in the width direction are located in the same vertical plane, the center line of the middle radiation slot in the width direction of the seven radiation slots and the center line of the antenna body in the width direction are located in the same vertical plane, and the rest radiation slots are symmetrically distributed around the center line of the antenna body in the width direction.

7. The low sidelobe antenna for use in a vehicle communication system according to claim 6, wherein lengths of seven said radiating slots are equally set;

or the lengths of the seven radiation gaps are reduced in the direction from the center of the antenna body to the two ends of the antenna body.

8. The low sidelobe antenna for a vehicle communication system according to claim 2, wherein the number of said radiation slot groups is five, the five radiation slot groups are spaced apart in a width direction of said antenna body, and each of said radiation slot groups includes four radiation slots;

the center line of the antenna body in the width direction and the center line of the antenna body in the length direction are respectively positioned in the same vertical plane with the center line of the feed gap in the width direction and the center line of the feed gap in the length direction;

the middle radiation slot group in the five radiation slot groups is positioned on the central line of the antenna body in the length direction, and the rest radiation slot groups are symmetrically distributed relative to the central line of the antenna body in the length direction; the four radiation slots in each radiation slot group are symmetrically distributed about the center line of the antenna body in the width direction of the antenna body.

9. The low sidelobe antenna for use in a vehicle communication system according to any one of claims 1 to 8, wherein the antenna body comprises:

the resonance box is internally provided with a resonance groove, the notch of the resonance groove is arranged upwards, and the lower surface of the resonance box is provided with a feed gap communicated with the resonance groove;

the feed box is internally provided with a feed groove, the feed groove is connected to the lower surface of the resonance box and covers the outer side of the feed gap, and the feed groove and the lower surface of the resonance box enclose to form the feed cavity; and

the box cover plate is connected to the upper surface of the resonance box and covers the notch of the resonance groove, the box cover plate and the resonance groove are enclosed to form the resonance cavity, and the box cover plate is provided with the radiation gap communicated with the feed groove; the coaxial feed terminal penetrates through the feed box and extends into the feed slot.

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