Antenna device

An antenna device is provided for a vehicle. The antenna device includes a substrate, an antenna element and a capacitor part. The substrate includes a pair of main surfaces which face opposite sides each other. The antenna element includes a metal plate part which is disposed over and separated from one of the main surfaces, and a metal leg part which extends from the metal plate part toward the substrate. The capacitor part is electrically connected to the metal plate part through the metal leg part and includes two or more capacitors connected in series.

TECHNICAL FIELD

An aspect of the present invention relates to an antenna device.

BACKGROUND ART

An antenna device, which transmits and receives radio waves used for radio broadcasting, GPS, ETC, and the like, is attached to a vehicle such as a car. Patent Literature 1 discloses a so-called air gap-type antenna device including a dielectric substrate provided on a ground conductor, and a radiation conductor plate which is formed of a metal plate disposed at a predetermined interval on the dielectric substrate. In Patent Literature 1, additional capacitor is formed between the ground conductor and each solder land soldered to a single leg extending from the radiation conductor plate. According to Patent Literature 1, in a case where the additional capacitor is formed, transmission and reception efficiency of the antenna is improved.

SUMMARY

In Patent Literature 1, a dielectric substrate is interposed between a ground conductor and a solder land, thereby forming additional capacitor to be connected to a radiation conductor plate which is an antenna element. Capacitance of the additional capacitor changes according to a thickness of the dielectric substrate and a size of the solder land. Therefore, capacitance of the additional capacitor easily varies for each antenna device, and thus there is a problem in that it is not possible to sufficiently exhibit transmission and reception performance depending on the antenna device. That is, there is a problem in that the antenna device, in which transmission and reception efficiency of an antenna is not improved, is manufactured. Therefore, a method is desired which is capable of accurately setting the above-described additional capacitor.

An aspect of the disclosure is to provide an antenna device capable of accurately setting the additional capacitor to be connected to the antenna element.

According to an aspect of the disclosure, there is provided an antenna device for a vehicle including: a substrate including a pair of main surfaces which face opposite sides each other; an antenna element that includes a metal plate part which is provided over one of the main surfaces and is disposed to be separated from the one main surface, and a metal leg part which extends from the metal plate part toward the substrate and is fixed to the substrate; and a capacitor part electrically connected to the antenna element, in which the capacitor part is electrically connected to the metal plate part via the metal leg part and includes two or more capacitors connected in series.

In the antenna device, an electrostatic capacitance of the capacitor part to be connected to the antenna element is determined by the capacitors therein. Therefore, compared to a case where the capacitor part is formed using, for example, the substrate, a wiring provided on the substrate, and the like, it is possible to suppress a variation in the electrostatic capacitance of the capacitor part. Here, the capacitor part electrically connected to the antenna element includes two or more capacitors connected in series. In this case, it is possible to set a synthetic capacitance of the two or more capacitors connected in series to the electrostatic capacitance of the capacitor part. Therefore, it is possible to reduce the variation in the electrostatic capacitance of the capacitor part due to the capacitors. Therefore, according to the antenna device, it is possible to accurately set an additional capacitor to be connected to the antenna element.

The antenna device may further include a ground pattern provided in a first area of the substrate, in which the capacitor part is provided on a second area, which is different from the first area, of the substrate. In this case, for example, it is possible to suitably prevent the electrostatic capacitance of the capacitors in the capacitor part from being affected by the ground pattern. In addition, it is possible to prevent a parasitic capacitance due to the ground pattern, the substrate, and the wiring for connecting the capacitors from being generated at the capacitor part. Therefore, it is possible to further reduce the variation in the electrostatic capacitance of the capacitor part.

Each of the capacitors may have the same electrostatic capacitance, and the electrostatic capacitance of each of the capacitors may correspond to the product of an electrostatic capacitance of the capacitor part and the number of the capacitors in the capacitor part. In this case, it is possible to excellently reduce the variation in the electrostatic capacitance of the capacitor part.

The capacitors may be provided on the one of the main surfaces, and at least one of the capacitors may be disposed not to overlap the metal plate part. In this case, the electrostatic capacitance of the capacitor part is likely not to be affected by the metal plate part. Therefore, it is possible to more accurately set the additional capacitor to be connected to the antenna element.

The antenna device may receive circularly polarized radio waves through two-point feeding. In this case, it is possible to increase a wavelength capable of being received by the antenna device.

An opening part may be provided at a part of the metal plate part. In this case, it is possible to band-widen the wavelength capable of being received by the antenna device while suppressing a rise of manufacturing costs.

The antenna device may further include a shield case provided on an opposite side of the antenna element while interposing the substrate between the shield case and the antenna element, in which at least one of the capacitors may be disposed not to overlap the shield case. In this case, since it is possible to reduce the number of the capacitors which are capacitively coupled to the shield case, it is possible to suppress deterioration in performance of the antenna device.

The antenna device may further include an antenna provided on an opposite side of the substrate while interposing the antenna element between the antenna and the substrate, and receives radio waves in a different frequency band from the antenna element. In this case, the antenna device is capable of simultaneously transmitting and receiving the radio waves in a plurality of frequency bands.

According to an aspect of the present disclosure, it is possible to provide an antenna device capable of accurately setting additional capacitor connected to an antenna.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferable embodiments of the present invention will be described in detail with reference to the accompanying drawings. In description below, the same reference symbol is used for the same element or an element having the same function, and the description thereof will not be repeated.

An antenna device according to the present embodiment is a patch antenna for a vehicle and has a function of transmitting and receiving radio waves used for, for example, GPS, ETC, satellite radio, GNSS, and the like. The antenna device is connected to an in-vehicle external device through a cable. Hereinafter, an external housing of the antenna device and an inner wiring of the antenna device will not be described.

FIG. 1is a schematic perspective diagram illustrating the antenna device according to the present embodiment.FIG. 2is an enlarged diagram illustrating an area shown by a dashed line inFIG. 1.FIG. 3Ais a schematic bottom diagram illustrating the antenna device according to the present embodiment.FIG. 3Bis an enlarged plan diagram illustrating an area shown by a dashed line inFIG. 3A. The antenna device1illustrated inFIG. 1toFIG. 3Bincludes a substrate2having a pair of main surfaces11and12which face opposite sides each other, an antenna element3provided on the main surface11, a shield case4provided on the main surface12, and a cable5which electrically connects the antenna element3to the external device. The antenna device1is configured such that the shield case4, the substrate2, and the antenna element3are overlapped in order. The shield case4is provided on an opposite side of the antenna element3while interposing the substrate2therebetween. Hereinafter, a direction, in which the substrate2, the antenna element3, and the shield case4are overlapped with each other, is referred to as a “stack direction”. In the present embodiment, “viewed from the stack direction” corresponds to a “plan view”.

The substrate2is a plate-shaped circuit board on which a ground pattern, a capacitor, an amplifier circuit, and the like are provided, and the antenna element3and the shield case4are attached thereto. Each of the main surfaces11and12of the substrate2has, for example, an approximately square shape. The ground pattern, a guidance wiring, and the capacitor with respect to the antenna element3are mainly provided on the main surface11, and the amplifier circuit and the like are mainly provided on the main surface12. Most parts (parts other than a spot which is connected to the antenna element3or the like) of the ground pattern and the guidance wiring, which are provided on the main surface11, are covered by an insulating material such as a resin. In addition, the amplifier circuit or the like on the main surface12is covered by the shield case4. The ground pattern provided on the main surface11, the amplifier circuit provided on the main surface12, and the like are not illustrated in the drawing.

A first area11aand second areas11b, which are different from each other, are set on the main surface11. The first area11ais an area which occupies most of the main surface11, and, in contrast, the second areas11bare areas corresponding to respective corners2aof the substrate2. In the present embodiment, total four second areas11bare provided on the main surface11. The ground pattern is provided on the first area11a, and, in contrast, the ground pattern is not provided on the second area11b. In addition, the ground pattern is not provided on the main surface12which overlaps the second areas11b. Instead, a plurality of capacitors13, which are included in the capacitor part C with respect to the antenna element3, are provided on the respective second areas11b. The capacitors13and the capacitor part C will be described in detail later.

A through hole14which extends in the stack direction is provided at each corner2aof the substrate2(refer toFIG. 2and FIG.3B). A part (specifically, a metal leg part which will be described later) of the antenna element3is inserted into the through hole14. A surface of the through hole14may be covered by a conductive layer which is a part of the guidance wiring that is different from the ground pattern. In this case, the antenna element3and the guidance wiring are suitably conducted in the through hole14.

The antenna element3is a member which transmits and receives radio waves, and is formed by bending a metal plate or an alloy plate. The antenna element3includes a metal plate part21which is disposed to be separated from the main surface11of the substrate2, feeding parts22and23which extend from the metal plate part21toward the main surface11, and a plurality of metal leg parts24which extend from respective corners21aof the metal plate part21toward the main surface11and are fixed to the substrate2.

The metal plate part21is a part which transmits and receives the radio waves in the antenna element3, and has an approximately quadrangle plate shape. As described above, the metal plate part21is disposed to be separated from the substrate2, and there is a space provided between the metal plate part21and the substrate2in the stack direction. Therefore, the antenna device1according to the present embodiment is an air gap-type device, and air corresponds to a dielectric of the antenna device1. When viewed from the stack direction, the metal plate part21is slightly smaller than the main surface11of the substrate2. When viewed from the stack direction, an entirety of the metal plate part21overlaps the main surface11. The metal plate part21is provided with two cutout parts21band21cwhich are separated from each other. Each of the cutout parts21band21cis provided to extend from an edge which forms the metal plate part21toward a center of the metal plate part21in a plan view. In a plan view, parts of the main surface11are exposed from parts which are cut out by the cutout parts21band21c.

The feeding parts22and23are parts which electrically connect the metal plate part21to the wiring on the substrate2, and have bar shapes which extend along the stack direction. The feeding part22is provided to protrude from a bottom of the cutout part21bof the metal plate part21to the substrate2. In the same manner, the feeding part23is provided to protrude from a bottom of the cutout part21cof the metal plate part21to the substrate2. The bottom of the cutout part is a portion located closest to a center of the metal plate part in the cutout part. As described above, since the two feeding parts22and23are provided, the antenna device1is capable of receiving circularly polarized radio waves through two-point feeding.

The metal leg parts24are parts, which are fixed to the substrate2, of the antenna element3, and have bar shapes which extend along the stack direction. The metal leg parts24are inserted into the corresponding through holes14. Tips of the metal leg parts24are exposed from a side of the main surface12. As illustrated inFIG. 3A, the tips of the metal leg parts24are fixed to the substrate2using, for example, solders S, respectively. The metal leg parts24are electrically connected to the capacitor parts C formed on the second area11bof the main surface11, respectively.

The metal plate part21, the feeding parts22and23, and the metal leg parts24are formed of the same metal plate or the same alloy plate. The respective feeding parts22and23are formed by bending, for example, parts which protrude from the bottoms of the corresponding cutout parts21band21c. The metal leg parts24are formed by bending parts which protrude from the corners21aof the metal plate part21.

The shield case4is a member which reduces electromagnetic noises, and has conductivity. The shield case4is formed by bending, for example, one metal plate or one alloy plate. The shield case4includes a main part4awhich has an octagonal shape when viewed from the stack direction, and a wall part4bwhich stands from an edge of the main part4a. There is a space provided between the main part4alocated on an inner side than the wall part4bin the shield case4and the main surface12of the substrate2. The edge of the main part4ais located on an inner side than an edge of the substrate2. In a plan view, the through holes14provided in the substrate2are located on an outer side of the edge of the main part4a. The metal leg parts24of the antenna element3are provided not to overlap the shield case4in the stack direction. As illustrated inFIG. 3B, the main part4aoverlaps a part of the second area11b. A slit, a protrusion, or the like may be provided in at least any of the main part4aand the wall part4b. Although potential of the shield case4is set to, for example, reference potential (ground), the potential of the shield case4is not limited thereto.

Subsequently, the above-described capacitor part C will be described in detail. The capacitor part C is an additional capacitor for making up a shortage of an electrostatic capacitance formed by the antenna element3and the substrate2, and is provided on each of the second areas11b. In the present embodiment, four capacitor parts C are provided on the main surface11, and the respective capacitor parts C are electrically connected to the corresponding metal leg parts24. Each of the capacitor parts C includes the plurality of above-described capacitors13, a wiring31for connecting the antenna element3to the capacitors13, and a wiring32for connecting the capacitors13to each other. In the present embodiment, each of the capacitor parts C includes two capacitors13, one wiring31, and one wiring32. In the present embodiment, total eight capacitors13are provided on the main surface11.

The capacitor13is, for example, a two terminal-type multilayer ceramic chip capacitor, and has a predetermined electrostatic capacitance. The electrostatic capacitance of the plurality of capacitors13included in each capacitor part C may be the same with each other or may be different from each other. In each capacitor part C, the plurality of capacitors13are connected in series to each other on the second area11b. As illustrated inFIG. 2andFIG. 3B, the capacitor13, which is disposed to be nearest to the metal leg part24, of the plurality of capacitors13, is electrically connected to the metal leg part24through the wiring31. The adjacent capacitors13are connected in series to each other through the wiring32. The respective capacitors13in the capacitor part C are electrically connected to the metal plate part21through the metal leg part24. In the present embodiment, although the respective capacitors13are disposed in a linear shape, the disposition is not specifically limited. In other words, as long as the respective capacitors13are connected in series to each other, for example, the wiring32may be disposed to have a folded shape. In each second area11b, the shapes of the wiring31and the wiring32and disposition states of the capacitors13may be different from each other. One terminal of the capacitor13, which is farthest from the metal leg part24on an equivalent circuit, is electrically connected to the ground pattern. A part of the capacitor13in the capacitor part C may be located on the first area11a(refer toFIG. 1andFIG. 2).

A synthetic capacitance of the capacitors13included in the capacitor part C corresponds to an electrostatic capacitance of the capacitor part C. The electrostatic capacitance of the capacitor part C is smaller than the electrostatic capacitance of the respective capacitors13. Here, in a case where the electrostatic capacitance of the capacitor part C is set to α and the electrostatic capacitance of the respective capacitors13are set to β1 and β2, the following Equation 1 is realized. In a case where the two capacitors13are included in the capacitor part C as in the present embodiment, the following Equation 2 is realized. In a case where the respective capacitors13included in the capacitor part C have the same electrostatic capacitance and the electrostatic capacitance of the respective capacitors13is set to β1, the electrostatic capacitance α of the capacitor part C becomes β1/2. That is, in the case where the respective capacitors13included in the capacitor part C have the same electrostatic capacitance, the electrostatic capacitance of each of the capacitors13included in the capacitor part C corresponds to the product of the electrostatic capacitance of the capacitor part C and the number of the capacitors13included in the capacitor parts C.
1/α=1/β1+1/β2  Equation 1
α=β1×β2/(β1+β2)  Equation 2

Subsequently, effects of the antenna device1according to the present embodiment will be described with reference to first and second comparative examples. An antenna device according to the first comparative example has the same configuration as the antenna device1according to the present embodiment other than a fact that the capacitor part includes one capacitor. In the first comparative example, the electrostatic capacitance of the one capacitor corresponds to the electrostatic capacitance of the capacitor part. An antenna device according to the second comparative example has the same configuration as the antenna device1according to the present embodiment other than a fact that the capacitor part includes parasitic capacitance of the multiple wiring. In the second comparative example, the sum of the parasitic capacitance between the multiple wiring and parasitic capacitance of a pair of wiring provided to interpose the substrate therebetween corresponds to the electrostatic capacitance of the capacitor part.

It is assumed that the electrostatic capacitance of the capacitor part is set to 0.5 pF and variation in all the capacitors is ±0.1 pF (that is, the electrostatic capacitance of the capacitor is in a range of 0.4 pF to 0.6 pF) (hereinafter, simply referred to as “first assumption”). In a case of the first assumption, the electrostatic capacitance of the capacitor part according to the first comparative example is in the range of 0.4 pF to 0.6 pF. Alternatively, it is assumed that the electrostatic capacitance of the capacitor part is set to 0.75 pF and the variation in all the capacitors is ±0.1 pF (hereinafter, simply referred to as “second assumption”). In a case of the second assumption, the electrostatic capacitance of the capacitor part according to the first comparative example is in a range of 0.65 pF to 0.85 pF. As above, in the first comparative example, the electrostatic capacitance of the capacitor part has a variation of ±0.1 pF. Here, the variation in the electrostatic capacitance of the capacitor part corresponds to a peak variation in the resonant frequency of the antenna device. For example, in a case where the antenna device transmits and receives the radio waves used for the GPS, a variation of ±0.1 pF corresponds to a fact that the resonant frequency varies by ±80 MHz from a predetermined frequency. Therefore, depending on the variation in the electrostatic capacitance, there is a case where the gain, which is acquired when the predetermined frequency is received, of the antenna device may be largely deteriorated from an ideal value. Therefore, in the first comparative example, there is a problem in that a transmission and reception property of the antenna may not be sufficiently exhibited.

In the second comparative example, in either the first assumption or the second assumption, an actually measured value of the electrostatic capacitance of the capacitor part tends to vary rather than at least the first comparative example. Therefore, in the second comparative example, there is a high possibility that the transmission and reception property of the antenna device is not sufficiently exhibited rather than the first comparative example.

Subsequently, the variation in the electrostatic capacitance of the capacitor part C according to the present embodiment will be considered. First, the first assumption will be considered in a case where the respective capacitors13included in the capacitor part C have the same electrostatic capacitance. At this time, the electrostatic capacitance of the respective capacitors13become 1.0 pF based on Equations 1 and 2. As described above, since it is assumed that the variation in the capacitors13is ±0.1 pF, a minimum value of the electrostatic capacitance of the capacitor part C corresponding to the synthetic capacitance of the capacitors13is 0.45 pF, and the maximum value thereof is 0.55 pF. In this case, the variation in the electrostatic capacitance of the capacitor part C is ±0.05 pF. The first assumption will be considered in a case where the respective capacitors13included in the capacitor part C have different electrostatic capacitance. At this time, since the electrostatic capacitance of the capacitor part C is set to 0.5 pF, the electrostatic capacitance of one of the two capacitors13included in the capacitor part C is set to 1.5 pF and the electrostatic capacitance of another capacitor13is set to 0.75 pF. In this case, since the minimum value of the electrostatic capacitance of the capacitor part C is 0.56 pF and the maximum value thereof is 0.44 pF, the variation in the electrostatic capacitance of the capacitor part C is ±0.06 pF.

The second assumption in a case where the respective capacitors13included in the capacitor part C have the same electrostatic capacitance will be considered. At this time, the electrostatic capacitance of the respective capacitors13is 1.5 pF based on Equations 1 and 2. Since it is assumed that the variation in the capacitors13is ±0.1 pF, the minimum value of the electrostatic capacitance of the capacitor part C corresponding to the synthetic capacitance of the capacitors13becomes 0.8 pF and the maximum value becomes 0.7 pF. In this case, the variation in the electrostatic capacitance of the capacitor part C is ±0.05 pF. In addition, the second assumption will be considered in a case where the respective capacitors13included in the capacitor part C have the different electrostatic capacitance. At this time, since the electrostatic capacitance of the capacitor part C is set to 0.75 pF, the electrostatic capacitance of one of the two capacitors13included in the capacitor parts C is set to 1 pF and the electrostatic capacitance of another capacitor13is set to 3 pF. In this case, since the minimum value of the electrostatic capacitance of the capacitor part C becomes 0.688 pF and the maximum value thereof becomes 0.812 pF, the variation in the electrostatic capacitance of the capacitor part C is ±0.062 pF.

Therefore, in either the first or second assumption, the electrostatic capacitance of the capacitor part C according to the present embodiment is likely not to vary rather than the first and second comparative examples regardless of a relationship between the electrostatic capacitance of the capacitors13included in the capacitor part C. Therefore, in the present embodiment, a gain, which is acquired in the case where the predetermined frequency is received, of the antenna device is likely not to be deteriorated rather than the first and second comparative examples. In addition, since the electrostatic capacitance of the capacitor part C corresponds to the synthetic capacitance of the plurality of capacitors13, a distribution of the variation in the electrostatic capacitance of the capacitor part C tends to be small. In other words, a probability that the electrostatic capacitance of the capacitor part C becomes a set value or be close to the set value tends to be high.

Here, with reference toFIG. 4, an influence of the gain of the antenna device accompanying a change in the electrostatic capacitance of the capacitor part will be described using a detailed example.FIG. 4is a graph illustrating an example of a gain with respect to the resonant frequency in an antenna device which transmits and receives the radio waves used for the GPS. InFIG. 4, a horizontal axis indicates a frequency and a vertical axis indicates the gain. As illustrated inFIG. 4, in a case where the electrostatic capacitance of the capacitor part is the ideal value, setting is performed such that the gain of the antenna device becomes the largest at a frequency (approximately 1575 MHz) of the radio wave used for the GPS. In contrast, in a case where the electrostatic capacitance of the capacitor part deviates from the ideal value, a maximum value of the gain is located at a spot which is different from the frequency (approximately 1575 MHz). For example, the larger the electrostatic capacitance becomes, the closer the maximum value of the gain to a side of a low frequency. The smaller the electrostatic capacitance, the closer the maximum value of the gain to a side of a high frequency. Therefore, as the antenna device is resonated at a frequency separated from the above frequency, the gain is reduced at the frequency of the radio wave used for the GPS.

The capacitor part according to the first comparative example is applied as the capacitor part of the antenna device. In this case, as described above, the resonant frequency varies by at most approximately ±80 MHz from the predetermined frequency (approximately 1575 MHz). In this case, the gain of the antenna device at the predetermined frequency is reduced by at most 9 dB or more. In a case where the capacitor part according to the second comparative example is applied, there is a case where the gain of the antenna device at the predetermined frequency is further reduced. In contrast, in the embodiment, the variation in the capacitor part C is suppressed up to at most ±0.05 pF. In this case, the variation in the resonant frequency of the antenna device is suppressed up to at most approximately ±40 MHz. At this time, the reduction in the gain of the antenna device at the predetermined frequency becomes at most approximately 5 dB. In addition, in the present embodiment, in a case where it is assumed that the variation in each of the capacitors13is ±0.05 pF, the variation in the capacitor part C is suppressed up to at most ±0.025 pF. In this case, the variation in the resonant frequency of the antenna device C is suppressed up to at most approximately ±18 MHz. At this time, it is possible to suppress the reduction in the gain of the antenna device at the predetermined frequency up to at most approximately 1 dB. From the results, it is understood that the variation in the gain of the antenna device at the predetermined frequency is reduced by reducing the variation in the capacitor part.

Considering the above comparison results, according to the antenna device1of the present embodiment, it is possible to suppress the variation in the electrostatic capacitance of the capacitor part C, compared to the second comparative example in which the capacitor part is formed using, for example, the substrate, the wiring provided on the substrate, and the like. Here, the capacitor part C, which is electrically connected to the antenna element3, includes the two capacitors13connected in series. At this time, it is possible to set the synthetic capacitance of the two capacitors13connected in series to the electrostatic capacitance of the capacitor part C. In this case, it is possible to reduce the variation in the electrostatic capacitance of the capacitor part C due to the capacitors13, compared to the first comparative example in which one capacitor is included in the capacitor part. Therefore, according to the antenna device1, it is possible to accurately set the additional capacitor to be connected to the antenna element3.

The antenna device1includes the ground pattern provided in the first area11aof the substrate2, and the capacitor part C is provided on the second area11bwhich is different from the first area11aof the substrate2. Therefore, for example, it is possible to suitably prevent the electrostatic capacitance of the capacitors13in the capacitor part C from being influenced by the ground pattern. In addition, at the capacitor part C, it is possible to prevent a capacitor from being formed by the ground pattern, the substrate, and the wiring32for connecting the capacitors13. Therefore, it is possible to further reduce the variation in the electrostatic capacitance of the capacitor part C.

The respective capacitors13may have the same electrostatic capacitance, and the electrostatic capacitance of the respective capacitors13may correspond to the product of the electrostatic capacitance of the capacitor part C and the number of the capacitors13in the capacitor part C. In this case, it is possible to excellently reduce the variation in the electrostatic capacitance of the capacitor part C.

The antenna device1receives the circularly polarized radio wave by two-point feeding through the feeding parts22and23. Therefore, it is possible to increase a wavelength capable of being received by the antenna device1.

FIG. 5is a schematic perspective diagram illustrating an antenna device according to a first modified example of the present embodiment. As illustrated inFIG. 5, an antenna element3A of an antenna device1A is not provided with the feeding parts22and23, and is provided with a feeding part25which extends from a center of the metal plate part21A toward the substrate2. In addition, the metal plate part21A is provided with opening parts26aand26b. The opening parts26aand26bmay have the same shapes with each other, or may have different shapes from each other. The opening parts26aand26bmay have a point symmetry relationship with respect to the center of the metal plate part21A. In the first modified example, it is possible to band-widen the wavelength capable of being received by the antenna device1A while suppressing a rise of manufacturing costs. The number of opening parts provided in the metal plate part may be one or may be three or more. The metal plate part21A may be provided with cutouts part instead of the opening parts.

FIG. 6is a schematic perspective diagram illustrating an antenna device according to a second modified example of the present embodiment. As illustrated inFIG. 6, an antenna device1B is provided with an antenna41on an opposite side of the substrate2while interposing the metal plate part21between the antenna41and the substrate2. The antenna41is an antenna which receives a radio wave in a different frequency band of the antenna element3, and is a ceramic patch antenna provided on the metal plate part21. According to the second modified example, the antenna device1B is capable of simultaneously transmitting and receiving radio waves in a plurality of frequency bands. The antenna41may be an antenna which receives the radio wave in the different frequency band of the antenna element3, and the antenna41is not limited to the ceramic patch antenna.

An antenna device according to an aspect of the present invention is not limited to the above-described embodiment and the modified examples, and other various modifications are possible. The embodiment and the modified examples may be appropriately combined. For example, the first modified example may be combined with the second modified example, and the antenna41may be provided on the antenna device1A. In a case where the number of feeding parts is one as in the first modified example, the opening parts26aand26bmay not be essentially provided in the metal plate part21. In the first modified example, the number of opening parts provided in the metal plate part21is not limited.

In the embodiment and the modified examples, the ground pattern, the guidance wiring, and the capacitor with respect to the antenna element3are mainly provided on the main surface11and the amplifier and the like are mainly provided on the main surface12. However, the present invention is not limited thereto. For example, the ground pattern, the amplifier circuit, and the like may be provided on both sides of the main surfaces11and12.

In the embodiment and the modified examples, at least one capacitor13of the capacitors13provided on the main surface11may be disposed to be not overlapped with the metal plate part21in the stack direction. In this case, the electrostatic capacitance of the capacitor part C is likely not to be affected by the metal plate part21. Therefore, it is possible to more accurately set the additional capacitor to be connected to the antenna element3.

In the embodiment and the modified examples, at least one capacitor13of the capacitors13provided on the main surface11may be disposed to be not overlapped with the shield case4in the stack direction. In this case, since it is possible to reduce the number of the capacitors13which are capacitively coupled to the shield case4, the electrostatic capacitance of the capacitor part C is likely not to be affected by the shield case4. Therefore, since it is possible to more accurately set the additional capacitor to be connected to the antenna element3, it is possible to suppress deterioration in performance of the antenna device1. All the capacitors13may be disposed to be not overlapped with the shield case4in the stack direction.

In the embodiment and the modified examples, the electrostatic capacitance of the respective capacitor parts C may be different. For example, an optimal electrostatic capacitance according to the corresponding metal leg part24may be set to the capacitor part C. That is, the number of the capacitors13included in each of the capacitor parts C may be different. The number of the capacitors13included in at least a part of the capacitor parts C may be one or two or more. For example, in a case where the number of the capacitors13included in the capacitor part C is three, the electrostatic capacitance of the capacitor part C is set to α, and the electrostatic capacitance of the respective capacitors13are set to β1, β2, and β3, the following Equation 3 is established. In a case where the respective capacitors13included in the capacitor part C have the same electrostatic capacitance and the electrostatic capacitance of the respective capacitors13are set to β1, the electrostatic capacitance α of the capacitor part C becomes β1/3. Therefore, in a case where the number of the capacitors13included in the capacitor part C is three or more and the respective capacitors13included in the capacitor part C have the same electrostatic capacitance, the electrostatic capacitance of the respective capacitors13included in the capacitor parts C correspond to the product of the electrostatic capacitance of the capacitor part C and the number of the capacitors13included in the capacitor part C.
1/α=1/β1+1/β2+1/β3  Equation 3

In the embodiment and the modified examples, in a case where the number of the capacitors13included in the capacitor part C is three or more, all the capacitors13may have the same electrostatic capacitance. Therefore, it is possible to further excellently reduce the variation in the electrostatic capacitance of the capacitor part C. In addition, the distribution of the variation in the electrostatic capacitance of the capacitor part C tends to be small. The capacitor part C may not be provided at a part of the second areas11b.

In the embodiment and the modified examples, at least some of the capacitors13included in the capacitor parts C may be provided on the main surface12. In this case, it is possible to reduce an area of the second areas11bwhile securing the electrostatic capacitance of the capacitor part C. At least one capacitor13in the capacitor parts C may be disposed to be not overlapped with the metal plate part21. In this case, the electrostatic capacitance of the capacitor part C is likely not to be affected by the metal plate part21. Therefore, it is possible to more accurately set the additional capacitor to be connected to the antenna element3. The second area11bprovided with the capacitor part C may not be essentially provided at the corner2aof the substrate2. Therefore, some of the capacitors13may be provided other than the corner2aof the substrate2.

In the embodiment and the modified examples, the main part4aof the shield case4is provided to overlap at least some of the capacitors13. However, the present invention is not limited thereto. For example, the main part4amay be provided to overlap all the capacitors13, or may be provided not to overlap all the capacitors13.

REFERENCE SIGNS LIST