Patent Application
20180219281
This application claims priority from Japanese Patent Application No. JP2017-016450 filed on Feb. 1, 2017. The content of this application is incorporated herein by reference in its entirety.
The present disclosure relates to an antenna device and a method for manufacturing the antenna device.
A wireless device has been known which includes a substrate, a wireless module that is mounted on the substrate, and a housing that houses the substrate and the wireless module (Japanese Unexamined Patent Application Publication No. 2015-8410). At the housing side from an antenna portion of the wireless module, a void having a length that is substantially equal to a multiple of a half wavelength of radio waves corresponding to a communication frequency of the antenna portion is ensured.
A stack type microstrip antenna including a passive element (parasitic element) above a driven element (feed element) of the microstrip antenna has been known (see Japanese Unexamined Patent Application Publication No. 03-74908). The parasitic element is attached to the inner surface of a radome that covers the entirety of the antenna or embedded within the radome. The driven element is mounted on a metal base, and the radome is mounted on the metal base so as to cover the driven element.
In the wireless device disclosed in Japanese Unexamined Patent Application Publication No. 2015-8410, it is necessary to ensure a void between the wireless module and the housing, and thus it is difficult to reduce the thickness of the wireless device. In the stack type microstrip antenna disclosed in Japanese Unexamined Patent Application Publication No. 03-74908, both the driven element and the radome are fixed to the metal base. In a step of mounting the driven element to the metal base and a step of mounting the radome to the metal base, alignment has to be performed such that the central axis of the driven element and the central axis of a parasitic element provided on the radome coincide with each other. If displacement occurs either in the step of mounting the driven element to the metal base or in the step of mounting the radome to the metal base, displacement occurs between the driven element and the parasitic element.
Accordingly, it is an object of the present disclosure to provide an antenna device that is suitable for thickness reduction of the device and in which displacement less likely to occur between a feed element and a parasitic element.
An antenna device according to a first aspect of the present disclosure includes:
an antenna module including a dielectric substrate and a feed element provided on, in, or above the dielectric substrate;
a radome comprising a dielectric and disposed so as to oppose the antenna module in a radiation direction of the feed element;
a parasitic element provided at a position on the radome at which electromagnetic coupling with the feed element is achieved; and
an adhesive layer disposed between the antenna module and the radome to bond the antenna module to the radome.
Since the parasitic element is provided on the radome and the radome and the antenna module are bonded to each other by the adhesive layer, the adhesive layer is interposed between the feed element of the antenna module and the parasitic element provided on the radome. It is possible to make the feed element and the parasitic element closer to each other as compared to a configuration in which a void is ensured therebetween, and thus it is possible to reduce the thickness of the antenna device.
Since the antenna module is directly bonded to the radome by the adhesive layer, displacement between the feed element of the antenna module and the parasitic element provided on the radome is less likely to occur, as compared to a configuration in which the antenna module and the radome are mounted to a common base member.
In an antenna device according to a second aspect of the present disclosure, in addition to the configuration of the antenna device according to the first aspect, the adhesive layer has a lower dielectric constant than the dielectric substrate.
It is possible to weaken electromagnetic coupling between the feed element and the parasitic element.
In an antenna device according to a third aspect of the present disclosure, in addition to the configurations of the antenna devices according to the first and second aspects,
the feed element of the antenna module is provided on a surface of the dielectric substrate, and the antenna module further includes a dielectric layer covering the surface of the dielectric substrate and the feed element, and
the dielectric layer is bonded to the radome by the adhesive layer.
The interval between the feed element and the parasitic element is large as compared to the case where the dielectric layer is not disposed. As a result, it is possible to weaken electromagnetic coupling between the feed element and the parasitic element.
In an antenna device according to a fourth aspect of the present disclosure, in addition to the configurations of the antenna devices according to the first to third aspects, a step surface restricting a position of the antenna module in an in-plane direction is provided on an inner surface of the radome.
In a step of bonding the antenna module to the radome, it is possible to easily position the antenna module relative to the radome.
In an antenna device according to a fifth aspect of the present disclosure, in addition to the configurations of the antenna devices according to the first to fourth aspects, the radome also serves as a housing which houses the antenna module.
Since the radome also serves as a housing, it is possible to reduce the number of components and also further reduce the thickness of the antenna device.
In an antenna device according to a sixth aspect of the present disclosure, in addition to the configurations of the antenna devices according to the first to fifth aspects,
the antenna module includes a plurality of other feed elements provided on the dielectric substrate in addition to the feed element, and the plurality of the other feed elements constitutes an array antenna, and
a plurality of other parasitic elements are provided in, on, or above the radome in addition to the parasitic element, and the plurality of the other parasitic elements are electromagnetically coupled with the plurality of the other feed elements, respectively.
Even in the case where a plurality of feed elements and a plurality of parasitic elements are disposed, alignment thereof is easily performed, since displacement between the feed element of the antenna module and the parasitic element provided on the radome is less likely to occur.
A method for producing an antenna device according to a seventh aspect of the present disclosure includes the steps of:
preparing an antenna module including a dielectric substrate and a feed element provided on the dielectric substrate;
preparing a radome on which a parasitic element is provided and which is larger than the antenna module in a plan view; and
positioning and bonding the antenna module to the radome such that the feed element and the parasitic element are electromagnetically coupled with each other.
Since the antenna module including the feed element is bonded to the radome on which the parasitic element is provided, the adhesive layer is interposed between the feed element of the antenna module and the parasitic element provided on the radome. It is possible to make the feed element and the parasitic element closer to each other as compared to a configuration in which a void is ensured therebetween, and thus it is possible to reduce the thickness of the antenna device.
Since the antenna module is directly bonded to the radome by the adhesive layer, displacement between the feed element of the antenna module and the parasitic element provided on the radome is less likely to occur, as compared to a method in which the antenna module and the radome are mounted to a common base member.
Other features, elements, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments of the present disclosure (with reference to the attached drawings).
An antenna device according to a first embodiment will be described with reference to
Each of the plurality of feed elements 22 is connected to a high-frequency signal terminal of the high-frequency integrated circuit element 30 via a transmission line 24 provided within the dielectric substrate 21. The ground plane 23 is connected to a ground terminal of the high-frequency integrated circuit element 30 via a wire 25 provided within the dielectric substrate 21.
A plurality of conductor columns 31 project from the second surface 21B of the dielectric substrate 21. The plurality of conductor columns 31 and the high-frequency integrated circuit element 30 are embedded within a sealing resin layer 40. Each conductor column 31 reaches the surface of the sealing resin layer 40. A plurality of lands 41 are provided on the surface of the sealing resin layer 40 so as to correspond to the plurality of conductor columns 31. Some of the terminals of the high-frequency integrated circuit element 30 are connected to the corresponding lands 41 via wires 26 within the dielectric substrate 21 and the conductor columns 31. The ground plane 23 is connected to the lands 41 for grounding via wires 27 within the dielectric substrate 21 and the conductor columns 31.
Each feed element 22 is disposed so as to oppose the corresponding parasitic element 12, and each parasitic element 12 is electromagnetically coupled with the corresponding feed element 22. The dielectric constant of the adhesive layer 50 is lower than the dielectric constant of the dielectric substrate 21.
The radome 10 has a function to protect the antenna module 20. When the antenna module 20 is provided in a portable terminal such as a smartphone or a tablet terminal, the radome 10 also serves as a housing of the portable terminal that houses the antenna module 20.
Next, advantageous effects of the first embodiment will be described. By electromagnetically coupling the parasitic elements 12 with the feed elements 22, it is possible to widen the band of the antenna device. By adjusting the thickness of the adhesive layer 50, it is possible to accurately control the strength of the electromagnetic coupling between the feed elements 22 and the parasitic elements 12. By making the dielectric constant of the adhesive layer 50 lower than the dielectric constant of the dielectric substrate 21, it is possible to weaken the electromagnetic coupling between the feed elements 22 and the parasitic elements 12.
In a structure in which a void is ensured between the feed elements 22 and the parasitic elements 12, in order to prevent the contact between the feed elements 22 and the parasitic elements 12, it is preferable to increase the interval therebetween to some extent. In the first embodiment, the adhesive layer 50, which is formed from a dielectric, is disposed between the feed elements 22 and the parasitic elements 12. Thus, even when the interval between the feed elements 22 and the parasitic elements 12 is decreased, the contact therebetween does not occur. Thus, in the first embodiment, it is possible to reduce the thickness of the antenna device as compared to the structure in which a void is ensured between the feed elements 22 and the parasitic elements 12.
When the interval between the feed elements 22 and the parasitic elements 12 is increased, the electromagnetic coupling between one feed element 22 and the parasitic element 12 opposing to the feed element 22 adjacent to the one feed element 22 easily occurs. When the feed element 22 and the adjacent parasitic element 12 are electromagnetically coupled with each other, desired antenna characteristics are not obtained. In the first embodiment, it is possible to make the feed elements 22 and the parasitic elements 12 closer to each other, and thus the electromagnetic coupling between the feed element 22 and the adjacent parasitic element 12 is less likely to occur. In order to inhibit the electromagnetic coupling between the feed element 22 and the adjacent parasitic element 12, it is preferable to make the interval between each feed element 22 and each parasitic element 12 smaller than the interval between the adjacent feed elements 22.
When a structure in which each of the antenna module 20 and the radome 10 is fixed to another common base member is adopted, an error in positioning of the antenna module 20 and the base member and an error in positioning of the radome 10 and the base member are superimposed on an error in positioning of the antenna module 20 and the radome 10. In the first embodiment, since the antenna module 20 is directly positioned and fixed to the radome 10 via the adhesive layer 50, it is possible to reduce an error in positioning.
When a plurality of the feed elements 22 and a plurality of the parasitic elements 12 are disposed to constitute an array antenna, it is possible to enhance the accuracy of alignment of the feed elements 22 and the parasitic elements 12 corresponding to each other.
Next, a modification of the first embodiment will be described with reference to
In the present modification, it is possible to increase the interval between the feed elements 22 and the parasitic elements 12 as compared to the structure of the first embodiment. As a result, it is possible to weaken the electromagnetic coupling between the feed elements 22 and the parasitic elements 12. Whether the structure of the first embodiment or the structure of the modification is adopted may be determined in accordance with a target magnitude for the electromagnetic coupling between the feed elements 22 and the parasitic elements 12.
Next, an antenna device according to a second embodiment will be described with reference to
In the second embodiment, the strength of the electromagnetic coupling between the feed elements 22 and the parasitic elements 12 depends not only on the dielectric constant and the thickness of the adhesive layer 50 but also on the dielectric constant and the thickness of the dielectric layer 28. Thus, the flexibility in adjusting the strength of the electromagnetic coupling between the feed elements 22 and the parasitic elements 12 is increased.
In the second embodiment as well, the parasitic elements 12 may be embedded within the radome 10 as in the modification of the first embodiment shown in
Next, an antenna device according to a third embodiment will be described with reference to
In the third embodiment, by the antenna module 20 being brought into contact with the step surfaces 11A of the radome 10, the step surfaces 11A restrict the position of the antenna module 20 in the in-plane direction. Accordingly, it is possible to easily position the antenna module 20 relative to the radome 10. As a result, it is possible to easily position the feed elements 22 and the parasitic elements 12.
Next, modifications of the third embodiment will be described with reference to
Each embodiment is illustrative, and it is needless to say that the components shown in the different embodiments may be partially replaced or combined. The same advantageous effects achieved by the same configuration in multiple embodiments are not mentioned successively in each embodiment. Furthermore, the present disclosure is not limited to the above-described embodiments. For example, it is obvious to a person skilled in the art that various changes, modifications, combinations, etc. may be made.
While preferred embodiments of the disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. The scope of the disclosure, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-016450 | Feb 2017 | JP | national |
