Patent Description:
There is known a telematics antenna to be mounted on a vehicle. Telematics is a general term for services that provide information from a cloud server to a moving object (vehicle). Specifically, an on-vehicle antenna is connected to an on-vehicle telematics control unit (TCU). Through wireless communication between the on-vehicle antenna and a base station on the cloud, the TCU receives information from the cloud server and provides the information to a person on the vehicle (e.g., the TCU displays the information on a display).

The telematics antenna conforms to communication standards (protocols), such as Long-Term Evolution (LTE), 5th Generation Mobile Communication System (<NUM>), and Wideband Code Division Multiple Access (WCDMA; a registered trademark). The telematics antenna therefore needs to deal with a wide frequency range and requires an antenna length corresponding to the wavelengths of the frequency range. Accordingly, the antenna element tends to be large-sized.

There is also known a deformed folded dipole antenna in which an antenna element is folded once and disposed on both sides of a board in order to downsize the antenna (see <CIT>).

Herein, a known telematics antenna device 100D is described with reference to <FIG> is an exploded perspective view of the known antenna device 100D.

As shown in <FIG>, the antenna device 100D includes a top cover 10D, an antenna element 20D, a board 30D, a bracket 40D, and a cable C3. The antenna element 20D is a telematics antenna element made of metal and having a three-dimensional folded structure. The left and right side parts of the antenna element 20D are folded three times. As described above, the antenna element of a telematics antenna device tends to be large-sized, in particular for an antenna device that needs to deal with lower frequencies. This is because the lower the frequency is, the longer antenna length is required with respect to the wavelength. Accordingly, the antenna element 20D becomes large-sized.

The board 30D is mounted with the antenna element 20D and circuit elements. The cable C3 is a coaxial cable covered with sponge. The cable C3 is electrically connected to conductor patterns of the board 30D (feeding point, grounding point). The bracket 40D is a metal grounding plate. The antenna element 20D and the board 30D are mounted on a flat surface of the bracket 40D and covered by the resin top cover 10D.

The known antenna device 100D has the large antenna element 20D and the large bracket 40D that serves as a metal grounding surface for the antenna element 20D. Therefore, there is a demand to downsize an antenna device while retaining the antenna characteristic. Further, assembling the antenna device 100D places a burden on workers because the folding lines of the antenna element 20D are asymmetrical.

<CIT> discloses a folded dipole antenna.

An object of the present invention is to downsize an antenna device, increase the antenna characteristic, and simplify the built-up structure of the antenna device.

To achieve the above object, according to an aspect of the present invention, there is provided an antenna device including: a folded dipole antenna comprising an antenna element, the antenna element being a folded flat metal plate and having a folded structure; and a board on which the antenna element is mounted, wherein the antenna element includes an antenna element body, an unfolded shape of the antenna element body is in mirror symmetry with respect to a line of symmetry, and the antenna element body includes side parts parted by the line of symmetry, each of the side parts having four or more folding lines.

The accompanying drawings are not intended as a definition of the limits of the invention but illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention, wherein:.

Hereinafter, the first embodiment, the modification of the first embodiment, the second embodiment, and the third embodiment of the present invention are described in this order in detail with reference to the attached figures. However, the scope of the invention is not limited to the illustrated examples.

The first embodiment of the present invention is described with reference to <FIG>. Firstly, the external structure of an antenna device <NUM> in this embodiment is described with reference to <FIG> is a perspective external view of the antenna device <NUM> in this embodiment. <FIG> is a lateral view of the mounted antenna device <NUM> in this embodiment.

The antenna device <NUM> is a telematics antenna device to be mounted on a vehicle (moving object). The antenna device <NUM> conforms to the communication standards (protocols) of LTE, <NUM>, and WCDMA. However, the communication standards to which the antenna device <NUM> conforms are not limited to them.

As shown in <FIG>, the antenna device <NUM> includes a top cover <NUM> and a cable C. <FIG> shows the X axis, Y axis, and Z axis on the basis of the antenna device <NUM>. The X, Y, Z axes are also shown in other figures. The antenna device <NUM> has a box shape (substantially cuboid) with the dimensions of <NUM> (length in the X axis direction) by <NUM> (length in the Y axis direction) by <NUM> (length in the Z axis direction), for example. The dimensions of the box-shaped antenna device <NUM> are not limited to these example dimensions and may be equal to or less than the example dimensions, for example.

The top cover <NUM> is made of resin, or more specifically, made of a combination of nonmetallic polycarbonate (PC) and acrylate styrene acrylonitrile (ASA) resin. The top cover <NUM> covers the antenna element <NUM> and the board <NUM>, which are described later, from their top surfaces facing in the +Z direction. The material of the top cover <NUM> is not limited to the PC and ASA resin.

The top cover <NUM> includes a top cover body <NUM>, a mount part <NUM>, and a label <NUM>. The top cover body <NUM> is the body of the box-shaped top cover <NUM>. The mount part <NUM> is for mounting the antenna device <NUM> on a vehicle. The mount part <NUM> is integrally formed on the top cover body <NUM>.

As shown in <FIG>, the antenna device <NUM> is mounted on an instrument panel I of the vehicle by inserting a round-head external screw <NUM> in a not-illustrated hole in the mount part <NUM> and screwing the external screw <NUM> into a not-illustrated internal screw formed in the instrument panel I.

The label <NUM> is attached to the top surface of the top cover body <NUM>. On the label <NUM>, information regarding the antenna device <NUM> is printed (e.g., a quick response (QR) code for identifying the antenna device <NUM>, product name).

The cable C is a coaxial cable. One end of the cable C is electrically connected to the board <NUM> (described later) of the antenna device <NUM>, and the other end is connected to the TCU on the vehicle.

Next, the internal configuration of the antenna device <NUM> is described with reference to <FIG>. <FIG> is an exploded perspective view of the antenna device <NUM> in this embodiment. <FIG> shows the unfolded antenna element <NUM> in this embodiment. <FIG> is a planar view of the board <NUM>.

As shown in <FIG>, the antenna device <NUM> includes the top cover <NUM>, the antenna element <NUM>, the board <NUM>, and the bracket <NUM>. The top cover body <NUM> of the top cover <NUM> includes a flat-head external screw <NUM>, a hole <NUM>, and a label attachment region <NUM>.

The external screw <NUM> is for fixing the top cover <NUM> to the bracket <NUM> from above the label <NUM> (from the +Z direction side). The hole <NUM> is a through hole for inserting the external screw <NUM>. The hole <NUM> is formed through the top cover body <NUM> in the Z axis direction. The label attachment region <NUM> is a recess part formed on the top surface of the top cover body <NUM> for attaching the label <NUM>.

The antenna element <NUM> is for a telematics antenna. The antenna element <NUM> is made of metal (e.g., galvanized steel plate (iron)) and has a three-dimensional folded structure. The telematics antenna of the antenna element <NUM> is a folded dipole antenna.

As shown in <FIG>, the antenna element <NUM> has an antenna element body <NUM> and a protrusion <NUM>. The antenna element body <NUM> is made of one flat metal plate (e.g., <NUM> thick). The antenna element <NUM> is flat when unfolded. The shape of the antenna element body <NUM> is in symmetry (mirror symmetry) with respect to a line of symmetry L1 as a central line. In other words, the two halves (two side parts) of the antenna element body <NUM> are line symmetrical with respect to the line of symmetry L1. In <FIG>, the right half (one side part) is the feeding-side antenna element part 21a, and the left half (one side part) is the grounding-side antenna element part 21b. That is, the feeding-side antenna element part 21a and the grounding-side antenna element part 21b are in line symmetry with respect to the line of symmetry L1.

The feeding-side antenna element part 21a includes a feeding point <NUM>. The feeding point <NUM> is electrically connected to an inner conductor of the cable C via the conductor pattern and circuit elements on the board <NUM>. The inner conductor of the cable C flows antenna currents of the cable C. The grounding-side antenna element part 21b includes a grounding point <NUM>. The grounding point <NUM> is electrically connected to an outer conductor of the cable C via the conductor pattern and circuit elements on the board <NUM>. The outer conductor of the cable C is grounded.

The feeding-side antenna element part 21a has five folding lines B1, B2, B3, B4, B5 in this order from the feeding point <NUM> in the direction in which the feeding-side antenna element part 21a extends. The feeding-side antenna element part 21a is folded at these folding lines B1 to B5. The grounding-side antenna element part 21b has five folding lines B1, B2, B3, B4, B5 in this order from the grounding point <NUM> in the direction in which the grounding-side antenna element part 21b extends. The grounding-side antenna element part 21b is folded at these folding lines B1 to B5. By folding the feeding-side antenna element part 21a and the grounding-side antenna element part 21b at the folding lines B1, B2, B3, B4 and B5, the three-dimensional antenna element <NUM> is formed, as shown in <FIG>.

In the known antenna device 100D shown in <FIG>, the antenna element 20D is asymmetrical (in mirror asymmetry) when unfolded. The respective side parts of the antenna element 20D have three folding lines. Although the antenna element <NUM> has more folding lines than the antenna element 20D, the feeding-side antenna element part 21a is symmetrical to the grounding-side antenna element part 21b. Therefore, in <FIG>, the folding lines B1 to B5 of the feeding-side antenna element part 21a are at the same positions in the up-down direction as the folding lines B1 to B5 of the grounding-side antenna element part 21b. That is, the folding lines of the feeding-side antenna element part 21a align with the folding lines of the grounding-side antenna element part 21b. Thus, the antenna element <NUM> has a simpler built-up structure than the known antenna element 20D.

Since the antenna element <NUM> has many folding lines, the antenna element <NUM> can secure a longer antenna length, which corresponds to the resonance frequency of a radio wave, as compared with an antenna element having a built-up structure of the equivalent size. In particular, with many folding lines, the antenna element <NUM> can easily have a long antenna element part and therefore resonate in low frequency ranges. It is preferable that each of the side parts of the antenna element <NUM> (each of the feeding-side antenna element part 21a and the grounding-side antenna element part 21b) have four folding lines or more.

The protrusion <NUM> has a rectangular loop shape and is connected to the feeding-side antenna element part 21a. The protrusion <NUM> as an antenna element connected to the feeding-side antenna element part 21a better contributes to the antenna characteristic because the antenna currents flow from the feeding point <NUM> to the grounding point <NUM>. Alternatively, the protrusion <NUM> may be connected to the grounding-side antenna element part 21b.

To improve the antenna characteristic, the antenna has to resonate in a specific frequency range. The resonance of the antenna changes depending on the length of the antenna element. The protrusion <NUM> is therefore loop-shaped in order to secure the length of the antenna element. Since the antenna currents mainly flow through the edge regions of the flat surface of the antenna element, the protrusion <NUM> without its rectangular internal region retains the antenna characteristic. The removal of the internal region of the protrusion <NUM> also contributes to weight reduction of the antenna device <NUM>.

The board <NUM> is a printed wiring board (PWB). The body of the board <NUM> is made of a nonconductive material, such as glass epoxy resin. On the board body, metal conductor patterns (e.g., copper foil) are formed, the antenna element <NUM> is mounted, and circuit elements are mounted as needed. For example, the board <NUM> may be provided with (i) a lumped constant circuit as a conductor pattern and a circuit element and (ii) a filter as a circuit element, in order to reduce noise of antenna signals. The board <NUM> is <NUM> thick, for example. The board <NUM> has holes <NUM> through which an attachment boss portion <NUM> and a support portion <NUM> (described later) of the bracket <NUM> are inserted.

In the antenna device <NUM>, the antenna element for the telematics antenna is mainly constituted of the antenna element <NUM>. By adding an antenna (element) pattern(s) to the conductor pattern of the board <NUM>, the antenna characteristic can be improved.

For example, as shown in <FIG>, a conductor pattern <NUM> is formed on the top surface of the nonconductive board body <NUM> of the board <NUM>. <FIG> is a schematic view and omits illustration of holes <NUM> and so forth. The conductor pattern <NUM> includes antenna patterns <NUM>, <NUM>. The antenna pattern <NUM> has an antenna length that allows resonance at <NUM>. The antenna pattern <NUM> has an antenna length that allows resonance at <NUM> to <NUM>. For example, when a frequency range that cannot be covered by the antenna element <NUM> (<NUM>, <NUM> to <NUM>) occurs and the antenna element <NUM> cannot sufficiently resonate in the frequency range, the antenna patterns <NUM>, <NUM> improve the antenna characteristic of the telematics antenna of the antenna device <NUM>.

The board body <NUM> also includes an antenna element contact region <NUM> to be in contact with (mounted with) the antenna element <NUM>. The antenna patterns <NUM>, <NUM> of the board <NUM> are not formed on the antenna element contact region <NUM> to avoid interference between the antenna patterns <NUM>, <NUM> and the antenna element <NUM>.

The bracket <NUM> is made of resin (nonmetallic polycarbonate and ASA resin). The bracket <NUM> supports and covers the antenna element <NUM> and the board <NUM> from their bottom surfaces facing in the -Z direction. The bracket <NUM> is joined to the top cover <NUM>. The material of the bracket <NUM> is not limited to the combination of polycarbonate and ASA resin and may be other nonmetallic material.

The bracket <NUM> includes the base <NUM>, the attachment boss portion <NUM>, and the support portion <NUM>. The base <NUM> is the flat base of the bracket <NUM>. The attachment boss portion <NUM> is integrally formed on the base <NUM>. Inside the attachment boss portion <NUM>, an internal screw that engages with the external screw <NUM> is formed. The top cover <NUM> is attached to the bracket <NUM> by the external screw <NUM> screwed in the internal screw, so that the attachment boss portion <NUM> fixes and supports the top cover <NUM>. The support portion <NUM> is integrally formed on the base <NUM> and supports the top cover <NUM> and the board <NUM> on which the antenna element <NUM> is mounted.

The process of assembling (manufacturing) the antenna device <NUM> is explained briefly. A worker firstly folds the antenna element <NUM> in the unfolded state shown in <FIG> at the folding lines B1, B2, B3, B4, and B5 to form the three-dimensional antenna element <NUM>, as shown in <FIG>. The worker then mounts the three-dimensional antenna element <NUM> on the board <NUM>. The worker then performs soldering or the like to electrically connect the feeding side end of the conductor pattern of the board <NUM> to the inner conductor of the cable C and the grounding side end of the conductor pattern of the board <NUM> to the outer conductor of the cable C.

The worker causes the bracket <NUM> to support the board <NUM> mounted with the antenna element <NUM> and attaches the top cover <NUM> to the bracket <NUM>. The worker screws the external screw <NUM> into the attachment boss portion <NUM> through the hole <NUM>, the antenna element <NUM>, and the board <NUM>, so that the board <NUM> mounted with the antenna element <NUM> is housed inside the top cover <NUM> and the bracket <NUM>. The worker attaches the label <NUM> to the label attachment region <NUM>. Thus, the antenna device <NUM> is assembled.

Next, the antenna characteristic of the antenna device <NUM> is described with reference to <FIG>. <FIG> is a perspective view of the antenna element <NUM> and the board <NUM> of the antenna device <NUM> in this embodiment. <FIG> shows the frequency response of the voltage standing wave ratio (VSWR) of the antenna device <NUM> in this embodiment with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the antenna device <NUM> in this embodiment with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the antenna device <NUM> in this embodiment with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the known antenna device 100D with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the known antenna device 100D with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the known antenna device 100D with respect to the frequency range of <NUM> to <NUM>.

As shown in <FIG>, the frequency response of the VSWR of the antenna device <NUM> (the board <NUM> mounted with the antenna element <NUM>) was measured as the antenna characteristic of the antenna device <NUM>. The VSWR is a measure indicating how efficiently the radio-frequency electric power is transmitted from a power source to a load (antenna) via a transmission line. The lower the VSWR is, the better the resonance occurs.

The frequency ranges to be used in telematics communication standards (herein, LTE, <NUM>, and WCDMA) are: <NUM> to <NUM>; <NUM> to <NUM>; <NUM> to <NUM>; and <NUM> to <NUM>. To cover the above frequency ranges, the VSWR of the antenna device <NUM> was measured with respect to <NUM> to <NUM>; <NUM> to <NUM>; and <NUM> to <NUM>.

<FIG> shows the VSWR of the antenna device <NUM> with respect to the frequency range of <NUM> to <NUM>. In <FIG>, Δ1 indicates the VSWR at <NUM>; Δ2 indicates the VSWR at <NUM>; Δ3 indicates the VSWR at <NUM>; Δ4 indicates the VSWR at <NUM>; Δ5 indicates the VSWR at <NUM>; Δ6 indicates the VSWR at <NUM>; and Δ7 indicates the VSWR at <NUM>. These frequencies indicated by Δ1 to Δ7 are the same as in <FIG> and so forth that show the graph of the frequency response of the VSWR of other antenna devices with respect to the same frequency range of <NUM> to <NUM>.

<FIG> shows the VSWR of the antenna device <NUM> with respect to the frequency range of <NUM> to <NUM>. In <FIG>, Δ1 indicates the VSWR at <NUM>; Δ2 indicates the VSWR at <NUM>; Δ3 indicates the VSWR at <NUM>; Δ4 indicates the VSWR at <NUM>; Δ5 indicates the VSWR at <NUM>; Δ6 indicates the VSWR at <NUM>; Δ7 indicates the VSWR at <NUM>; Δ8 indicates the VSWR at <NUM>; and Δ9 indicates the VSWR at <NUM>. These frequencies indicated by Δ1 to Δ9 are the same as in <FIG> and so forth that show the graphs of the frequency response of the VSWR of other antenna devices with respect to the same frequency range of <NUM> to <NUM>.

<FIG> shows the VSWR of the antenna device <NUM> with respect to the frequency range of <NUM> to <NUM>. In <FIG>, Δ1 indicates the VSWR at <NUM>; Δ2 indicates the VSWR at <NUM>; Δ3 indicates the VSWR at <NUM>; Δ4 indicates the VSWR at <NUM>; Δ5 indicates the VSWR at <NUM>; Δ6 indicates the VSWR at <NUM>; and Δ7 indicates the VSWR at <NUM>. These frequencies indicated by Δ1 to Δ7 are the same as in <FIG> and so forth that shows the graph of the frequency response of the VSWR of other antenna devices with respect to the same frequency range of <NUM> to <NUM>.

According to <FIG>, the antenna device <NUM> resonates at the VSWR that is lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna device <NUM> is therefore improved. Further, according to <FIG>, the antenna device <NUM> resonates at the VSWR that is lower than <NUM> and lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna device <NUM> is therefore improved. Further, according to <FIG>, the antenna device <NUM> resonates at the VSWR that is lower than <NUM> and lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna device <NUM> is therefore improved.

As described above, according to the first embodiment, the antenna device <NUM> includes: the antenna element <NUM> of a folded dipole antenna, the antenna element <NUM> being a folded flat metal plate and having a folded structure; and the board <NUM> on which the antenna element <NUM> is mounted. The antenna element <NUM> includes the antenna element body <NUM>. The unfolded shape of the antenna element body <NUM> is in mirror symmetry with respect to the line of symmetry L1. The antenna element body <NUM> includes side parts parted by the line of symmetry L1 (the feeding-side antenna element part 21a and the grounding-side antenna element part 21b), each of the side parts having five folding lines B1, B2, B3, B4 and B5. Thus, the antenna element <NUM> of the folded dipole antenna is folded at five folding lines B1 to B5. Such an antenna element <NUM> eliminates the need for a large metal bracket, allows downsizing of the antenna device <NUM>, and increases the antenna characteristic of the antenna device <NUM> without a large metal bracket. Further, the built-up structure of the antenna device <NUM> can be simplified because the unfolded shape of the antenna element <NUM> is mirror-symmetrical.

Preferably, the antenna element <NUM> may have the protrusion <NUM> connected to the antenna element body <NUM>. With the protrusion <NUM>, the unfolded shape of the antenna element <NUM> is asymmetrical (not in mirror symmetry) with respect to the line of symmetry L1. The protrusion <NUM> supplements the antenna characteristic of the antenna element body <NUM> and thereby increases the antenna characteristic of the antenna device <NUM>.

Preferably, the protrusion <NUM> may be connected to one side part among the side parts, the one side part being the feeding-side antenna element part 21a that includes the feeding point <NUM>. According to such a configuration, the protrusion <NUM> can better contribute to the antenna characteristic of the antenna device <NUM> as compared with the protrusion <NUM> connected to the grounding-side antenna element part 21b.

Preferably, the protrusion <NUM> may be loop-shaped. Therefore, the weight reduction of the antenna device <NUM> is achieved without decreasing its antenna characteristic.

Preferably, the board <NUM> may include the conductor antenna patterns <NUM>, <NUM> in a region that is not in contact with the antenna element <NUM> (the region different from the antenna element contact region <NUM>). The antenna patterns <NUM>, <NUM> can cover the resonance of the antenna element <NUM> in a specific frequency range and can avoid interference with the antenna element <NUM>.

Preferably, the antenna device <NUM> may include the nonmetal bracket <NUM> configured to support the antenna element <NUM> and the board <NUM>. The absence of a large metal bracket allows downsizing and weight reduction of the antenna device <NUM>.

A modification of the first embodiment is described with reference to <FIG> shows the unfolded antenna element 20A in the modification.

The antenna device in the modification includes the antenna element 20A shown in <FIG> instead of the antenna element <NUM> in the antenna device <NUM> in the first embodiment. The parts of the antenna device in the modification that are the same as the parts of the antenna device <NUM> are given the same reference numerals, and the description thereof is omitted.

The antenna element 20A includes the antenna element body <NUM> and the protrusion 22A.

The protrusion 22A has a rectangular shape and is connected to the feeding-side antenna element part 21a. Although the protrusion 22A is smaller than the protrusion <NUM> in the first embodiment, this is merely an example and the size of the protrusion 22A is not limited to this. The protrusion 22A may be connected to the grounding-side antenna element part 21b.

As described above, the antenna device in the modification includes the antenna element 20A and yields the same advantageous effects as the antenna device <NUM> in the first embodiment.

The second embodiment of the present invention is described with reference to <FIG>. <FIG> is a perspective view of the antenna element 20B and the board <NUM> of the antenna device 100B in the second embodiment. <FIG> shows the unfolded antenna element 20B in the second embodiment. <FIG> shows the frequency response of the VSWR of the antenna device 100B in this embodiment with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the antenna device 100B in this embodiment with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the antenna device 100B in this embodiment with respect to the frequency range of <NUM> to <NUM>.

As shown in <FIG>, the antenna device 100B in this embodiment includes the top cover <NUM>(not illustrated in <FIG>), the bracket <NUM> (not illustrated in <FIG>), the antenna element 20B, and the board <NUM>.

The antenna device 100B in this embodiment includes the antenna element 20B shown in <FIG> instead of the antenna element <NUM> in the antenna device <NUM> in the first embodiment. The parts of the antenna device 100B in the second embodiment that are the same as the parts of the antenna device <NUM> are given the same reference numerals, and the description thereof is omitted.

The antenna element 20B is an antenna element for a telematics antenna. The antenna element <NUM> is made of metal (e.g., galvanized steel plate (iron)) and has a three-dimensional folded structure. The telematics antenna of the antenna element 20B is a folded dipole antenna.

As shown in <FIG>, the antenna element 20B has an antenna element body 21B. The antenna element body 21B is made of one flat metal plate (e.g. <NUM> thick). The antenna element 20B is flat when unfolded. The shape of the antenna element body 21B is in symmetry with respect to the line of symmetry L1. The antenna element 20B does not include the protrusion <NUM> of the first embodiment or the protrusion 22A of the modification.

Next, the antenna characteristic of the antenna device 100B is described with reference to <FIG>.

The frequency response of the VSWR of the antenna device 100B shown in <FIG> (the antenna element 20B mounted on the board <NUM>) was measured as the antenna characteristic of the antenna device 100B.

<FIG> shows the VSWR of the antenna device 100B with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the VSWR of the antenna device 100B with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the VSWR of the antenna device 100B with respect to the frequency range of <NUM> to <NUM>.

According to <FIG>, the antenna device 100B resonates at the VSWR that is on the whole lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna device 100B is therefore improved. Further, according to <FIG>, the antenna device 100B resonates at the VSWR that is on the whole lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna device 100B is therefore improved. Further, according to <FIG>, the antenna device 100B resonates at the VSWR that is lower than <NUM> and lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna device 100B is therefore improved.

As described above, unlike the antenna device <NUM> in the first embodiment, the antenna device 100B in the second embodiment does not have a protrusion. This further simplifies the built-up structure of the antenna device 100B and reduces the weight of the antenna device 100B.

The third embodiment of the present invention is described with reference to <FIG>. <FIG> is a perspective view of an antenna system 100C in the third embodiment that includes antenna portions <NUM>, <NUM> and a bracket 40C. <FIG> shows the unfolded antenna element 20C in the third embodiment. <FIG> shows the frequency response of the VSWR of the antenna portion <NUM> in this embodiment with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the antenna portion <NUM> in this embodiment with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the antenna portion <NUM> in this embodiment with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the antenna portion <NUM> in this embodiment with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the antenna portion <NUM> in this embodiment with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the frequency response of the VSWR of the antenna portion <NUM> in this embodiment with respect to the frequency range of <NUM> to <NUM>.

As shown in <FIG>, the antenna system 100C in this embodiment includes a top cover (not illustrated in <FIG>), the antenna portions <NUM>, <NUM> as the antenna device, and the bracket 40C. The antenna portion <NUM> includes the antenna element 20C and the board <NUM>. The antenna portion <NUM> includes the antenna element 20C and the board <NUM>.

The antenna portions <NUM>, <NUM> have the same structure. The antenna portions <NUM>, <NUM> function as multiple-input and multiple-output (MIMO) antennas, for example. The MIMO is a technology for improving the transmission speed and transmission quality in wireless communication by using multiple antennas for the transmitter and receiver (in the antenna system 100C, two antenna portions <NUM>, <NUM>).

The antenna portion <NUM> includes the antenna element 20C shown in <FIG> instead of the antenna element <NUM> of the antenna device <NUM> (the antenna element <NUM> and the board <NUM>) in the first embodiment. The parts of the antenna portions <NUM>, <NUM> in the third embodiment that are the same as the parts of the antenna device <NUM> are given the same reference numerals, and the description thereof is omitted.

The antenna element 20C is an antenna element for a telematics antenna. The antenna element <NUM> is made of metal (e.g., galvanized steel plate (iron)) and has a three-dimensional folded structure. The telematics antenna of the antenna element 20C is a folded dipole antenna.

As shown in <FIG>, the antenna element 20C has an antenna element body 21C and protrusions <NUM>, <NUM>. The antenna element body 21C is made of one flat metal plate. The antenna element 20C is flat when unfolded. The shape of the antenna element body 21C is in symmetry with respect to the line of symmetry L1. In <FIG>, the right half is the feeding-side antenna element part 21c, and the left half is the grounding-side antenna element part 21d, with the line of symmetry L1 as the borders.

The protrusion <NUM> is the same as the protrusion <NUM> in the first embodiment, and is connected to the feeding-side antenna element part 21c. The protrusion <NUM> has a rectangular shape and is connected to the grounding-side antenna element part 21d. The protrusion <NUM> may be connected to the feeding-side antenna element part 21c.

The bracket 40C is made of the same material as the bracket <NUM> in the first embodiment. The bracket 40C is shaped to support the antenna portions <NUM>, <NUM> from the bottom. Thus, the size of the bracket 40C for housing the antenna device (antenna portions) is increased according to the number of antenna portions <NUM>, <NUM> (herein, two antenna portions). One end of the cable C1 is electrically connected to the conductor pattern of the board <NUM> of the antenna portion <NUM>, and the other end of the cable C1 is connected to the TCU. One end of the cable C2 is electrically connected to the conductor pattern of the board <NUM> of the antenna portion <NUM>, and the other end of the cable C2 is connected to the TCU. The top cover (not illustrated) of the antenna system 100C is made of the same material as the top cover <NUM> in the first embodiment, and the shape of the top cover conforms to the shape of the bracket 40C. That is, the antenna portions <NUM>, <NUM> are housed in the space inside the top cover and the bracket 40C of the antenna system 100C.

Next, the antenna characteristic of the antenna system 100C is described with reference to <FIG>.

For each of the antenna portions <NUM>, <NUM> of the antenna system 100C shown in <FIG>, the frequency response of the VSWR was measured as the antenna characteristic.

<FIG> shows the VSWR of the antenna portion <NUM> with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the VSWR of the antenna portion <NUM> with respect to the frequency range of <NUM> to <NUM>. <FIG> shows the VSWR of the antenna portion <NUM> with respect to the frequency range of <NUM> to <NUM>.

According to <FIG>, the antenna portion <NUM> resonates at the VSWR that is on the whole lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna portion <NUM> is therefore improved. Further, according to <FIG>, the antenna portion <NUM> resonates at the VSWR that is lower than <NUM> and lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna portion <NUM> is therefore improved. Further, according to <FIG>, the antenna portion <NUM> resonates at the VSWR that is lower than <NUM> and lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna portion <NUM> is therefore improved.

According to <FIG>, the antenna portion <NUM> resonates at the VSWR that is on whole lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna portion <NUM> is therefore improved. Further, according to <FIG>, the antenna portion <NUM> resonates at the VSWR that is on the whole lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna portion <NUM> is therefore improved. Further, according to <FIG>, the antenna portion <NUM> resonates at the VSWR that is lower than <NUM> and lower than the VSWR of the antenna device 100D shown in <FIG> with respect to the frequency range of <NUM> to <NUM>. The antenna characteristic of the antenna portion <NUM> is therefore improved.

As described above, according to the third embodiment, the antenna system 100C includes the antenna portions <NUM>, <NUM>. Thus, multiple antenna devices (antenna portions <NUM>, <NUM>) are downsized, the antenna characteristic is improved, and the built-up structure is simplified. Therefore, the antenna system 100C is downsized, the antenna characteristic of the antenna system 100C is improved, and the built-up structure of the antenna system 100C is simplified.

Preferably, the antenna system 100C may include the nonmetal bracket 40C configured to support the multiple antenna devices (antenna portions <NUM>, <NUM>). The absence of a large metal bracket allows downsizing and weight reduction of the antenna system 100C.

The embodiments and the modification described above are examples of the antenna device and the antenna system according to the present invention and do not limit the present invention. For example, at least two among the embodiments and the modification may be appropriately combined.

In the above embodiments and the modification, the antenna device <NUM>, the antenna device 100B, and the antenna system 100C include the cable C or the cables C1, C2 that is/are electrically connected to the conductor pattern of the board <NUM>. However, the present invention is not limited to this configuration. For example, the antenna device <NUM>, the antenna device 100B, and the antenna system 100C may include a connector that is electrically connected to the conductor pattern of the board <NUM>.

Claim 1:
An antenna device (<NUM>) comprising:
a folded dipole antenna comprising an antenna element (<NUM>),
the antenna element being a folded flat metal plate and having a folded structure; and
a board (<NUM>) on which the antenna element is mounted, wherein
the antenna element includes an antenna element body (<NUM>),
an unfolded shape of the antenna element body is in mirror symmetry with respect to a line of symmetry (L1), and
the antenna element body includes side parts (21a, 21b) parted by the line of symmetry, characterized in that each of the side parts has four or more folding lines (B1 to B5).