The present invention relates to an antenna substrate.
A communication device that uses a wireless network includes an antenna substrate as described in Patent Document 1, for example, for transmission and reception of electrical signals.
In a known antenna substrate, when an antenna has resonance points (points at which transmission characteristics are good) in a plurality of frequency bands, a filter structure or the like for removing radio waves having frequencies other than a desired frequency band is separately required. Thus, the known antenna substrate has a complicated structure, and is difficult to reduce in size.
An antenna substrate according to the present disclosure includes a first insulation layer including a first surface, a second surface located opposite the first surface, and a first through-hole conductor extending from the first surface to the second surface, a ground conductor located at the first surface, the ground conductor including a slot, a second insulation layer including a second through-hole conductor connected to the first through-hole conductor, the second insulation layer covering the ground conductor located at the first surface, and a first antenna conductor located at a surface located on the opposite side to the other surface of the second insulation layer, the other surface covering the ground conductor. The slot has a cross shape in which a horizontal slot extending in an X axis direction in a plane direction and a vertical slot extending in a Y axis direction in a plane direction intersect with each other. The first antenna conductor includes a first pattern, two second patterns, and a third pattern. The first pattern has a rectangular shape including a first long side and a second long side in the X axis direction and short sides in the Y axis direction. The first long side includes a portion overlapping with the horizontal slot. The second long side does not overlap with the horizontal slot but overlaps the vertical slot. The two second patterns are individually located in contact with the second long sides with the vertical slot interposed between the two second patterns. The third pattern has a rectangular shape including short sides in the X axis direction and long sides in the Y axis direction. The third pattern is in contact with the second long side of the first pattern at a position within the vertical slot in plane perspective. The third pattern extends in a direction away from the first long side. The third pattern is connected to the second through-hole conductor. The horizontal slot is within the first pattern in plane perspective except for a portion protruding in the Y axis direction. The short sides of the first pattern are longer than the short sides of the third pattern.
As described above, the known antenna substrate separately requires a filter structure or the like for removing radio waves having frequencies other than a desired frequency band. Because of this, the known antenna substrate has a complicated structure and reducing the size thereof is difficult. Thus, an antenna substrate that can improve transmission characteristics in a specific frequency band and that can be reduced in size is required.
The antenna substrate according to the present disclosure has the specific configuration as described above, which can improve transmission characteristics in a specific frequency band and reduce the size thereof.
An antenna substrate according to a first embodiment of the present disclosure will be described with reference to
The first insulation layer 2 includes a first surface S1, a second surface S2, and a first through-hole conductor 21. The first insulation layer 2 is not particularly limited as long as the first insulation layer 2 is made of a material having an insulation property. Examples of the material having the insulation property include resins such as an epoxy resin, a bismaleimide-triazine resin, a polyimide resin, a polyphenylene ether resin, and Teflon (Registered Trademark) (a fluorine resin), and a ceramic. Two or more of these resins may be mixed and used.
The first insulation layer 2 may contain a reinforcing material. Examples of the reinforcing material include insulation fabric materials such as glass fiber, glass non-woven fabric, aramid non-woven fabric, aramid fiber, and polyester fiber. Two or more types of reinforcing materials may be used in combination. An inorganic insulation filler made of, for example, silica, barium sulfate, talc, clay, glass, calcium carbonate, or titanium oxide may be dispersed in the insulation layer.
The first insulation layer 2 includes a through hole that passes through from the first surface S1 up to the second surface S2. A first through-hole conductor 21 is located in the through hole. A material of the first through-hole conductor 21 is not particularly limited as long as the material has electrical conductivity. Examples of a material having electrical conductivity include metals such as copper. Specifically, the first through-hole conductor 21 is made by metal plating such as copper plating.
The ground conductor 3 including a slot 31 is located on the first surface S1 of the first insulation layer 2. A material of the ground conductor 3 is not particularly limited as long as the material has electrical conductivity. Examples of a material having electrical conductivity include metals such as copper. Specifically, the ground conductor 3 is made of a metal foil such as a copper foil or made by metal plating such as copper plating.
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Similarly to the first insulation layer 2, the second insulation layer 4 is also formed with a through hole penetrating from the upper surface up to the lower surface. The second through-hole conductor 41 is located in the through hole. The second through-hole conductor 41 is at a position facing the first through-hole conductor 21, and is electrically connected to the first through-hole conductor 21.
The first antenna conductor 5 is located on a surface of the second insulation layer 4 located on the opposite side to the other surface thereof being in contact with the ground conductor 3. The first antenna conductor 5 is provided to receive and transmit electromagnetic waves. The material of the first antenna conductor 5 is not particularly limited as long as the material is a material having electrical conductivity. Examples of a material having electrical conductivity include metals such as copper. Specifically, the first antenna conductor 5 is made of a metal foil such as a copper foil or formed by metal plating such as copper plating.
The first antenna conductor 5 includes a first pattern 51, two second patterns 52, and a third pattern 53. In the antenna substrate 1 according to the first embodiment, the arrangement of the first pattern 51, the two second patterns 52, and the third pattern 53 is important to improve transmission characteristics in a specific frequency band and to reduce the size of the antenna substrate 1.
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That is, when radio waves having different frequencies are mixed, the antenna substrate 1 according to the first embodiment can transmit and receive only radio waves in one frequency band without providing a filter, for example. In the first antenna conductor 5, the third pattern 53 is located at a space formed by the first pattern 51 and the two second patterns 52 (a cove-like portion). Thus, the entire length (in the Y axis direction) of the first antenna conductor 5 can be shortened. As described above, the fact that the antenna substrate 1 according to the first embodiment is capable of improving transmission characteristics in a specific frequency band and is capable of being reduced in size can be understood.
In the first antenna conductor 5, adjusting the lengths of the long sides or the lengths of the short sides of the first pattern 51, the two second patterns 52, and the third pattern 53 enables the center frequency of the resonance point to be adjusted. Adjusting the length of the short side of the first pattern 51 (the length in the Y axis direction) enables the bandwidth of the resonance point to be widened or narrowed.
The manufacturing method of the antenna substrate 1 according to the first embodiment is not limited. The antenna substrate 1 may be manufactured, for example, by the follow procedure. First, a through hole is formed in an insulation layer serving as the first insulation layer 2. The through hole is formed, for example, by drilling, laser machining, or blasting process. After the through hole is formed, the ground conductor 3 is formed on the first surface S1 of the insulation layer serving as the first insulation layer 2, and the first through-hole conductor 21 and the grounding-use through-hole conductor 33 are formed in the through hole. These conductors are formed by, for example, copper plating by a semi-additive method.
An insulation layer serving as the second insulation layer 4 is formed. The insulation layer covers the first surface S1 of the first insulation layer 2. At this time, the slot 31 formed in the ground conductor 3 is filled with the insulation layer (the material having the insulation property and the reinforcing material described above) serving as the second insulation layer 4. A through hole is formed in the insulation layer serving as the second insulation layer 4 at a position facing the first through-hole conductor 21.
The first antenna conductor 5 is formed on the surface of the second insulation layer 4, and the second through-hole conductor 41 is formed inside the through hole. These conductors are also formed by copper plating by, for example, a semi-additive method. As for the first antenna conductor 5, the first pattern 51, the two second patterns 52, and the third pattern 53 are formed in the arrangement described above. The antenna substrate 1 according to the first embodiment can be obtained in this manner.
The antenna substrate according to the present disclosure is not limited to the antenna substrate 1 according to the first embodiment described above. For example, as in an antenna substrate 1′ according to a second embodiment illustrated in
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Similarly to the first insulation layer 2 and the second insulation layer 4, a material of the third insulation layer 6 is not particularly limited as long as the material has an insulation property. The third insulation layer 6 may contain a reinforcing material the same as or similar to the first insulation layer 2 and the second insulation layer 4. The material having the insulation property and the reinforcing material are as described above, and detailed description thereof will be omitted.
The fourth pattern 54 of the second antenna conductor 5′ is a member corresponding to the first pattern 51 of the first antenna conductor 5. The two fifth patterns 55 of the second antenna conductor 5′ are members corresponding to the two second patterns 52 of the first antenna conductor 5. The sixth pattern 56 of the second antenna conductor 5′ is a member corresponding to the third pattern 53 of the first antenna conductor 5.
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When the second antenna conductor 5′ is further included as in the antenna substrate 1′ according to the second embodiment, not only transmission and reception of a radio wave only in one direction but also expansion of the directivity of a radio wave can be achieved. A circularly polarized wave (transmission of a radio wave in a spiral manner) can improve a transmission property in a place where there are many obstacles.
The present disclosure is not limited to the above-described examples of the embodiments, and various variations can be made without departing from the gist of the present disclosure. For example, the lengths of the two second patterns 52 and the length of the third pattern 53 in the Y axis direction are different from each other in the above-described examples of the embodiments. However, the lengths may be the same. This may reduce the length of the first antenna conductor 5 in the Y axis direction, and thus, the reduction may be advantageous for reducing the size of the antenna substrate, in some cases. Similarly, when the lengths of the two fifth patterns 55 and the length of the sixth pattern 56 are the same, the length of the second antenna conductor 5′ in the X axis direction may be reduced, which may be advantageous for reducing the size of the antenna substrate in some cases. When both of the first antenna conductor 5 and the second antenna conductor 5′ have such a configuration, the configuration is more advantageous for size reduction.
In the above-described examples of the embodiments, when the first antenna conductor 5 is viewed in a plan view, the interval between the second pattern 52 and the third pattern 53 is constant. However, the interval between the second pattern 52 and the third pattern 53 does not need to be constant.
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As described above, making the interval between the second pattern 52 and the third pattern 53 narrower with decreasing distance to the first pattern 51 can reduce the reflection of a current flowing through the third pattern 53, which is advantageous for improving the electrical characteristics.
Although the corner portions of the first antenna conductor 5 and the second antenna conductor 5′ are right-angled in the above-described examples of the embodiments, at least some of the corner portions may have a curved shape. Forming the corner portion of the antenna conductor into a curved shape as described above can reduce reflection of a current flowing in the vicinity of the outer periphery of the antenna conductor, which is advantageous for improving electrical characteristics.
The wavelength of a radio wave becomes smaller in an insulation layer having a dielectric constant larger than a dielectric constant of air. Thus, as in the second embodiment described above, the second antenna conductor 5′ that transmits and receives radio waves in the insulation layer may be smaller than the first antenna conductor 5 that transmits and receives radio waves in the air. In other words, in the X axis direction and the Y axis direction, the length of the second antenna conductor 5′ may be smaller than the length of the first antenna conductor 5 in some cases. As a result, the area occupied by the second antenna conductors 5′ in the third insulation layer 6 can be reduced, and the length of the vertical slot 31b overlapping the second antenna conductors can be shortened, which are advantageous for reducing the size of the antenna substrate.
Number | Date | Country | Kind |
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2020-181700 | Oct 2020 | JP | national |
2021-026542 | Feb 2021 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP21/39072 | 10/22/2021 | WO |