CN109346840B

CN109346840B - Small-size antenna is with low section reflection bore structure printed antenna

Info

Publication number: CN109346840B
Application number: CN201811246256.5A
Authority: CN
Inventors: 周建明; 皮维超; 张磊; 董涛; 李兴旺
Original assignee: Beijing Institute of Technology BIT
Current assignee: Beijing Institute of Technology BIT
Priority date: 2018-10-25
Filing date: 2018-10-25
Publication date: 2021-06-08
Anticipated expiration: 2038-10-25
Also published as: CN109346840A

Abstract

The invention designs a low-profile printed antenna with a reflecting aperture surface structure for a small antenna, which has the characteristics of wide beam, wide frequency band, high front-to-back ratio and low-profile miniaturization, and relates to the technical field of antennas. The printed antenna is invented for solving the problem that the existing microstrip antenna can not simultaneously give consideration to broadband, wide beam, high front-to-back ratio, small size and low profile. The printed antenna adopts a multilayer structure, the top layer adopts a printed circuit board structure, and the upper layer and the lower layer adopt coupled microstrip line structures; the middle layer is a closed metal cavity filled with insulating foam, and the closed metal cavity comprises a coaxial line for feeding electricity; the bottom adopts a microstrip structure to carry out feed conversion from a microstrip to a coaxial line, and a low-profile large-height-difference parallel feed mode is formed. The invention can be used for near-field handheld radar detection equipment and small-sized mobile base stations.

Description

Small-size antenna is with low section reflection bore structure printed antenna

Technical Field

The invention relates to the technical field of antennas, in particular to a low-profile reflection caliber structure printed antenna for a small antenna.

Background

The printed antenna has the advantages of small thickness, controllable dielectric constant, relatively simple structural form, good processing performance and the like, thereby being widely applied. Printed antennas comprise a variety of structural forms, and from a structural point of view, a conventional printed antenna mainly comprises two basic components, namely a radiating element and a feeding structure.

The application scene aimed at by the scheme of the invention is that the wide-frequency-band low-profile printed circuit board antenna for the near-field portable detection radar has the working center frequency near 3.3GHz, and the distance from the top layer to the bottom layer of the antenna thickness is not more than 16 mm.

The existing microstrip antenna adopted on a large scale mostly adopts a traditional three-layer structure form, a radiation unit is generally arranged on a top layer and a reference ground is arranged on a bottom layer, and a bottom feed or side feed mode is usually adopted for feeding.

Disclosure of Invention

The embodiment of the invention provides a caliber loading reflection structure for a printed antenna, which can realize broadband wave beams on the premise of keeping the structural constraint of a low profile, thereby reducing the influence of backward target scattering on a handheld detection device.

In order to achieve the above object, in a first aspect, an embodiment of the present invention provides a semi-closed aperture-loaded reflective structure, where the aperture-loaded reflective structure is a rectangular metal cavity structure, the periphery of the cavity is closed, the top of the cavity is open, and the cavity is connected to a radiating element, and a circular hole is formed in the middle of the bottom of the cavity, so as to facilitate a coaxial feeder to pass through the cavity.

In a first possible implementation manner, with reference to the first aspect, the cavity is internally filled with air.

In a second possible implementation manner, in combination with the first aspect, the cavity is internally filled with a polyurethane foam material having a relative dielectric constant of approximately 1.0.

In a third possible implementation manner, in combination with the first aspect and the first possible implementation manner, the bottom opening is circular in shape.

In a fourth possible implementation manner, with reference to the first aspect and the first possible implementation manner, the bottom opening is a cross-shaped slot, and a center of the cross-shaped slot corresponds to the top feeding structure.

In a fifth possible implementation manner, with reference to the first aspect and the second possible implementation manner, the bottom opening is rectangular.

In a sixth possible implementation manner, with reference to the first aspect and the second possible implementation manner, the bottom opening is a cross-shaped slot, and a center of the cross-shaped slot corresponds to the top feeding structure.

In a second aspect, embodiments of the present invention provide a multilayer aperture-loaded low-profile broadband printed antenna form, wherein the reflective aperture structure form is formed using any of the aperture structure forms described in the above technical solutions.

In a first possible implementation manner, with reference to the second aspect, the radiation microstrip line unit is on the first layer, the dipole feed unit is on the second layer, the aperture-loaded reflection structure is on the third layer, the first layer and the second layer are separated by an insulating PCB substrate, and the second layer and the third layer are fixedly connected by reflow soldering.

In a second possible implementation manner, with reference to the second aspect, the dipole feed unit is on the first layer, the radiation unit is on the second layer, the aperture-loaded reflection structure is on the third layer, the first layer and the second layer are separated by an insulating PCB substrate, and the second layer and the third layer are fixedly connected in an adhesion manner.

In a third aspect, an embodiment of the present invention provides a low-profile height difference parallel feeding scheme for the printed antenna according to the second and third aspects, and a combined manner of a coaxial bottom and a microstrip side feed is adopted to implement non-planar parallel feeding, so that the overall height of the overall antenna and the feeding structure is reduced, and the overall integration is facilitated.

Drawings

For a clearer explanation of the embodiments of the present invention or the technical solutions in the prior art, a brief description will be given below of an embodiment and the drawings used in the description of the prior art, it is emphasized that the drawings described below are only some embodiments of the present invention, and that for a person skilled in the art, other drawings can be obtained from these drawings without creative efforts.

FIG. 1 is a schematic diagram of an aperture-loaded reflective structure for a printed antenna according to an embodiment of the present invention;

FIG. 2 is an exploded view of a printed antenna multilayer structure according to an embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view of a printed antenna according to an embodiment of the present invention;

FIG. 4 is a schematic cross-sectional view of a printed antenna according to an embodiment of the present invention;

FIG. 5 is a diagram illustrating return loss test results of a printed antenna according to an embodiment of the present invention;

FIG. 6 is a graph comparing simulation and test results of a printed antenna pattern from 2.9GHz to 3.8GHz according to an embodiment of the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it should be emphasized that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the scope of the present invention.

In the description of the present invention, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the devices or elements referred to must have a specific scope, be constructed and operated in a specific orientation, and thus, are not to be construed as limiting the present invention.

Referring to fig. 1, fig. 1 is a diagram of an aperture-loaded reflective structure 101 for a printed antenna according to an embodiment of the present invention, which is a metal cavity with a closed periphery, an open top and a bottom with a groove 102, where 103 is a microstrip-to-coaxial structure interface, 104 is a microstrip-to-coaxial feed port, and 105 is an electrical connector mounting limit slot.

The aperture loading reflection structure in the embodiment of the invention is integrally machined by adopting antirust aluminum alloy, the overall size is 56mm multiplied by 13mm, in order to reduce the weight, the peripheral wall thickness is 1mm, the bottom thickness is 1.5mm (locally increased by 1.5mm to form 103), the size of the aperture at the bottom is phi 8mm, the depth is 2mm, and the aperture size parameters can be selected in a simulation mode according to different working frequency bands and the front-to-back ratio requirement of the antenna. In this embodiment, the size of the coaxial feed port is phi 2.3mm, and is matched with the coaxial outer size of the feed port.

Referring to fig. 1, 101 is designed as a rectangular cavity structure mainly based on two considerations, one of which is that in order to suppress the backward radiation electric field as much as possible, reasonable boundary conditions need to be designed, the horizontal bottom surface of the cavity makes the horizontal component of the electric field zero, and the metal walls around make the vertical component of the electric field zero, so that compared with the use of a single horizontal reflecting plate, this way can produce better backward suppression capability.

Referring to fig. 1, the shape of 103 can be designed as a circle, a rectangle or a cross, and it is essential to make a discontinuous metal slot, so as to form a radiation current at the structural discontinuity, and this part of the current can further reduce the backward radiation wave of the antenna radiation unit, thereby improving the front-to-back ratio of the antenna radiation pattern.

Referring to fig. 2, fig. 2 is an exploded view of a multilayer structure of a printed antenna according to an embodiment of the present invention, where 201 is a bottom feed circuit, and a microstrip circuit is formed on a PCB by using an etching process, and is mainly used to implement microstrip-to-coaxial feed;

referring to fig. 2, 202 is the aperture loaded reflective structure of fig. 1, manufactured by integral machining, and in order to enable a soldering operation, silver plating surface treatment is performed at 202;

referring to fig. 2, 201 and 202 are screwed by 4 screws M2;

referring to fig. 2, 203 is a segment of coaxial line, and the outside is shielded by a shielding net to reduce energy leakage as much as possible; the bottom of the 203 is connected with the microstrip line on the 201 through a through hole on the 202 by spot welding;

referring to fig. 2, 204 is a printed circuit board, the top surface has a top feeding unit formed by etching process, and the bottom surface has a symmetrical dipole radiating unit formed by etching;

referring to fig. 2, the coaxial top outer copper sheet of 203 is connected with the bottom radiating element of 204 by spot welding, and the top inner conductor of 203 is connected with the top feeding element of 204 by spot welding;

referring to fig. 2, copper coated on the edge of the bottom surface 204 and the top surface of the 202 subjected to the surface silver plating treatment are connected and fixed through reflow soldering;

referring to fig. 2, 205 is a horizontal insertion electrical connector, which is structurally limited by a limiting groove on 202 and is fixed with the bottom of 202 by spot welding.

Referring to fig. 2, in the implementation of this embodiment, the connection should be made in the following order,

firstly, fixing the top end inner conductor of the 203 and the top surface of the 204 by spot welding;

secondly, the outer conductor at the top of the 203 and the radiation unit 204 are fully welded by soldering tin, so that the welding area of the 203 and the 204 is large enough, the whole stress is uniform and reliable, and the whole radiation unit can bear certain external force to pull;

thirdly, performing reflow soldering fixation on the 203 and the 204 as a whole with the 202, and ensuring that the 203 extends out of the bottom surface of the 202 through the via hole before reflow soldering;

fourthly, screwing and fixing the whole body formed by 201, 202, 203 and 204 by using countersunk head screws;

fifthly, pushing the probe 205 into a limit groove on the probe 202, and fixedly welding the probe on the probe 205 and the microstrip on the bottom surface of the probe 201 by using soldering tin;

and sixthly, fixing the tail parts of the 205 and the 202 by full welding, thereby ensuring that the external force for plugging and unplugging the cable cannot be transmitted to the probe end on the opposite side of the 205.

Fig. 3 and 4 show cross-sectional views of the printed antenna at different angles in this embodiment.

Fig. 5 shows the actual test result of the reflection parameter of the present embodiment at the frequency band of 3000MHz to 5000MHz, and it can be seen that the internal reflection coefficients at the designed frequency band of 2900MHz to 3500MHz of the present embodiment are all less than-15 dB, thereby meeting the design and use requirements.

Fig. 6 shows the printed antenna pattern at a typical frequency point, and it can be seen that the difference between the actual test result and the simulation result is very small in the pitching direction and the azimuth direction, and the front-to-back ratio is larger than 18dB, so that the actual use requirement is met.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes that can be easily made by those skilled in the art within the technical scope of the present invention should be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A small-sized antenna is with low section reflection bore structure printed antenna, characterized by that, adopt the design of the multilayer structure, the design of the multilayer structure includes radiating element, loading reflection bore structure, feed structure;

the loading reflection caliber structure is a rectangular cavity structure with an aperture at the bottom, and a cross-shaped metal groove is arranged at the upper part of the bottom surface of the loading reflection caliber structure, so that a loading effect is formed;

in the multilayer structure, the top layer is a printed circuit board, the top surface of the printed circuit board is a microstrip feed unit, and the bottom surface of the printed circuit board is a symmetrical printed dipole radiation unit; the middle layer is a loading reflection caliber structure and forms a reference ground and a loading reflection layer; the bottom layer is a large-height-difference parallel feed circuit part;

the top layer top surface microstrip feed unit feeds power through the coaxial top inner conductor, and the dipole radiation unit on the top layer bottom surface is connected with the coaxial top outer conductor;

the feed structure adopts a two-stage conversion feed mode of converting a horizontal micro-strip with a low section into a vertical coaxial micro-strip and then converting the horizontal micro-strip into the vertical coaxial micro-strip, so that the requirement of large-height difference parallel feed is met, and the design simultaneously considers the structural constraint of the handheld equipment and the basic requirement of antenna feed.

2. A printed antenna as claimed in claim 1, wherein the loaded reflective aperture structure is a rectangular cavity enclosed at the periphery, the top surface of the cavity is open, and the bottom surface of the cavity is provided with a coaxial feed circular hole and a cross-shaped metal groove.

3. The printed antenna of claim 2, wherein the loaded reflective aperture structure is internally filled with a polyurethane foam material having an air-filling or dielectric constant of approximately 1.0.

4. A printed antenna according to claim 3, wherein the centre of the feed hole is concentrically aligned with the centre of the loaded structural shape on the loaded reflective aperture.

5. The printed antenna according to any one of claims 1 to 4, wherein the printed antenna has an operating frequency of 2900MHz to 3800MHz, an external dimension of the loaded reflector aperture structure of 55mm to 60mm, and a height of 12mm to 15 mm; the total height of the printed antenna is 13-16 mm.

6. The printed antenna of claim 5, wherein a four-layer structure is adopted, the top layer is a top-layer microstrip feed element, the second layer is a symmetric dipole radiation element, the third layer is a loaded reflective aperture structure, and the fourth layer is a feed circuit; the coaxial feed line vertically passes through the loaded reflective aperture structure.