WO2022210828A1

WO2022210828A1 - Antenna device

Info

Publication number: WO2022210828A1
Application number: PCT/JP2022/015806
Authority: WO
Inventors: 龍治小林; 茂樹工藤; 義久須田
Original assignee: 原田工業株式会社
Priority date: 2021-03-31
Filing date: 2022-03-30
Publication date: 2022-10-06

Abstract

An antenna device 1 comprises: a circuit board 12 having a ground region; a first antenna element 18a that has the base end-side connected to a first power feed point provided to the circuit board 12 and that forms a first monopole antenna; a second antenna element 18b that has the base end-side connected to a second power feed point provided to the circuit board 12 and that forms a second monopole antenna; and a connection part 20 connecting the distal end part of the first antenna element 18a and the distal end part of the second antenna element 18b.

Description

antenna device

The present invention relates to an antenna device in which a plurality of monopole antennas are arranged side by side.

With the increasing sophistication and performance of vehicles, antenna devices in which multiple antennas are housed in a common housing are becoming popular (see Patent Document 1). GPS (Global Positioning System) that provides location information, ETC (Electronic Toll Collection System) and VICS (Vehicle Information and Communication System) for realizing ITS (Intelligent Transport Systems) It is being standard equipment. The plurality of antennas are accommodated in one housing. Although ETC and VICS are registered trademarks, their descriptions are omitted in the following description.

In the antenna device described in Patent Document 1, an ETC antenna and a GPS antenna are arranged in the center of a common housing, and a pair of TEL antennas (monopole antennas) are arranged on both left and right sides of them. By providing multiple TEL antennas, it becomes easier to support MIMO (Multiple Input Multiple Output). MIMO is a technique for spatially multiplexing signals using a plurality of transmitting and receiving antennas, and can improve the transmission speed and quality of communication data.

By the way, since the number of in-vehicle devices increases as vehicles become more sophisticated, it is necessary to reduce the size of the antenna device as much as possible to save space. As for the pair of TEL antennas as described above, it is desirable that the distance between the antenna elements can be made as small as possible. On the other hand, when a plurality of antennas are installed side by side, it is necessary to ensure wideband isolation between them.

Conventionally, in order to secure the isolation of two antennas in this way, a technique of adjusting the isolation by interposing a circuit or an element near the feeding point between the antenna elements (see Patent Documents 2 and 3), A technique has been proposed in which the mutual influence is reduced by bringing the ends of the elements close to each other for capacitive coupling (see Patent Document 4). In addition to this, there is also a method of ensuring isolation by arranging adjacent antenna elements so as to be orthogonal.

JP 2009-218799 A JP 2014-112824 A JP 2012-175317 A WO2019/107553

However, the techniques described in Patent Documents 2 to 4 generally tend to have a limited frequency band in which good impedance characteristics (radiation efficiency) and good isolation are compatible. On the other hand, arranging adjacent antenna elements orthogonally leads to restrictions on equipment configuration, and there is a problem that it is difficult to meet the demand for miniaturization of the antenna device.

The present invention has been made in view of such problems, and one of its objects is to provide an antenna device in which a plurality of monopole antennas are arranged side by side, and to achieve wideband performance without degrading isolation in a specific frequency band. To provide a technology capable of ensuring good characteristics for

An aspect of the present invention is an antenna device. This antenna device includes a circuit board having a ground area, a first antenna element having a base end connected to a first feeding point provided on the circuit board and forming a first monopole antenna, and a first antenna element provided on the circuit board. a second antenna element having a base end connected to the second feeding point and forming a second monopole antenna; a connecting portion connecting a tip portion of the first antenna element and a tip portion of the second antenna element; Prepare.

According to the present invention, in an antenna device in which a plurality of monopole antennas are arranged side by side, good characteristics can be secured in a wide band without degrading isolation in a specific frequency band.

It is a perspective view showing the outline of the antenna device concerning a 1st embodiment. It is a top view showing the structure of an antenna unit. It is a figure showing the result of having analyzed the frequency characteristic of a TEL antenna. FIG. 8 is a plan view showing the configuration of an antenna unit according to a second embodiment; FIG. 11 is a plan view showing the configuration of an antenna unit according to a modification; It is a figure showing the relationship between the line width of a meandering structure, and a frequency characteristic. It is a figure showing the relationship between the meandering width of a meandering structure, and a frequency characteristic. FIG. 11 is a perspective view showing the configuration of an antenna unit according to a third embodiment; FIG. 11 is a plan view showing the configuration of an antenna unit according to a modification; FIG. 11 is a plan view showing the configuration of an antenna unit according to another modified example; Analyzes and results of effects of the first embodiment are shown. Analyzes and results of effects of the first embodiment are shown. The analysis and the result regarding the effect of 2nd Embodiment are shown. FIG. 21 is a plan view showing the configuration of an antenna unit according to modification 6; FIG. 12 is a diagram showing an effect of the configuration of modification 6;

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, about the following embodiment and its modification, the same code|symbol is attached|subjected about the substantially same component, and the description is abbreviate|omitted suitably.

In the following embodiments, a vehicle antenna device (hereinafter simply referred to as "antenna device") in which two monopole antennas are arranged side by side will be exemplified. The monopole antenna illustrated here is a TEL antenna. In order to ensure broadband isolation of the two monopole antennas, the two antenna elements are connected to each other at the ends opposite their feed points. The details will be described below.

[First Embodiment]
FIG. 1 is a perspective view showing the outline of the antenna device according to the first embodiment. In the following description, for the sake of convenience, the positional relationship of the antenna device may be expressed in the front/rear, up/down, and left/right directions with reference to the mounted state of the vehicle.

The antenna device 1 includes an antenna unit 10 including a plurality of antennas. The antenna unit 10 is housed in a case (not shown). This case includes a lower case on which the antenna unit 10 is placed, and an upper case attached to the lower case so as to cover the antenna unit 10 from above. Both the upper case and the lower case are made of radio wave transparent resin.

The antenna unit 10 is configured by mounting a single GPS antenna 14 and a pair of

TEL antennas

16 a and 16 b on a circuit board 12 . Hereinafter, the

TEL antennas

16a and 16b will simply be referred to as "TEL antenna 16" unless otherwise distinguished. The circuit board 12 has a ground area, which will be described later, and functions as a ground plane.

The GPS antenna 14 is a patch antenna for GPS.

TEL antennas

16a and 16b are monopole antennas for telephones and include

antenna elements

18a and 18b, respectively. Antenna element 18a functions as a "first antenna element" and forms a first monopole antenna. Antenna element 18b functions as a "second antenna element" and forms a second monopole antenna. Hereinafter, the

antenna elements

18a and 18b are simply referred to as "antenna element 18" unless otherwise distinguished. The

antenna elements

18 a and 18 b are arranged symmetrically with respect to the circuit board 12 .

By providing a plurality of TEL antennas 16 in this manner, MIMO can be supported. The tip portions of the antenna element 18a and the antenna element 18b are connected to each other by a connecting portion 20 in order to improve isolation (details will be described later). A connector 22 having a feeding port for each antenna projects from the lower surface of the front end portion of the circuit board 12 . The antenna device 1 is mounted inside an instrument panel of a vehicle (not shown) or the like.

FIG. 2 is a plan view showing the configuration of the antenna unit. FIG. 2A shows the configuration of this embodiment, and FIG. 2B shows the configuration of a comparative example.
As shown in FIG. 2A, the circuit board 12 is a printed wiring board having a polygonal shape in plan view, and has a stepped shape in which the width of the front half is larger than the width of the rear half. The circuit board 12 has a symmetrical shape with respect to the centerline L. As shown in FIG. The antenna unit 10 has a symmetrical shape with respect to the center line L as a whole. A ground area 24 is provided on the surface of the circuit board 12 . A ground area 24 is common to the pair of TEL antennas 16 .

A GPS antenna 14 is arranged in the narrow area of the rear half of the circuit board 12 . The GPS antenna 14 is a dielectric patch antenna, and is configured by arranging a radiation electrode 28 on the surface of a dielectric layer 26 . The radiation electrode 28 is provided parallel to the upper surface of the circuit board 12 . A feeding point is provided on the radiation electrode 28 . An insertion hole is provided through the dielectric layer 26, and a feed pin for connecting a feed line provided on the back surface of the circuit board 12 and a feed point is inserted therethrough. In this embodiment, a one-point feeding type circularly polarized patch antenna is adopted as the GPS antenna 14, but a two-point feeding type patch antenna may be used. Since a known patch antenna is adopted for the GPS antenna 14, detailed description thereof will be omitted.

Feeding points P1 and P2 are provided at both left and right ends of the large region of the front half of the circuit board 12, and the base ends of the

antenna elements

18a and 18b are connected. The feeding point P1 functions as a "first feeding point" and the feeding point P2 functions as a "second feeding point". A pair of TEL antennas 16 are arranged on both left and right sides of the GPS antenna 14 . A pair of antenna elements 18 has a symmetrical structure with respect to the center line L. As shown in FIG.

The antenna element 18 is a conductor plate having an elongated rectangular (belt-shaped) main body 30 , and one end of the main body 30 extends inward (center line L side) to form a wide base end portion 32 . An inner end portion of the base end portion 32 is bent upward at a right angle to form a power supply portion 34 . A feeding portion of the antenna element 18a is connected to the feeding point P1, and a feeding portion 34 of the antenna element 18b is connected to the feeding point P2. In this embodiment, these connections are made by soldering. A tip portion 36 of the antenna element 18a and a tip portion 36 of the antenna element 18b are integrally connected via the connecting portion 20. As shown in FIG. The connecting portion 20 is a conductor plate having a width approximately equal to that of the main body 30, and is connected perpendicularly to the

antenna elements

18a and 18b.

That is, the antenna element 18a includes a base end portion 32 (corresponding to a “first base end portion”) connected to the circuit board 12 and a main body 30 (“ corresponding to the "first extension"). The antenna element 18b includes a base end portion 32 (corresponding to a “second base end portion”) connected to the circuit board 12 and a body 30 (“second base end portion”) extending rearward from the circuit board 12 from the base end portion 32 (“second base end portion”). (corresponding to "extension"). The connecting portion 20 connects the tip portion 36 of the antenna element 18 a and the tip portion 36 of the antenna element 18 b in the horizontal direction of the circuit board 12 .

When manufacturing the antenna unit 10, the

antenna elements

18a and 18b and the connection portion 20 are formed integrally by punching out a conductor plate into a square frame shape with one side open and bending the open end. . In a modified example, the

antenna elements

18a and 18b may be formed separately and the connecting portion 20 may be joined by welding or the like.

Each feed point P1, P2 is connected to a feed line mounted on the circuit board 12. A feed line for each antenna is provided as a microstrip line on the back surface of the circuit board 12 and connected to each feed port of the connector 22 .

　Three cables connected to the vehicle-mounted device (not shown) are connected to the connector 22 (see FIG. 1). These cables are all coaxial cables and are connected to the feeder lines of the GPS antenna 14 and the pair of TEL antennas 16 via connectors 22 . The inner conductor of the coaxial cable for the TEL antenna 16 is connected via connector 22 to the feed points (P1, P2) and the outer conductor is connected via connector 22 to the ground area 24 .

In this embodiment, as shown, the

antenna elements

18a, 18b are connected to the circuit board 12 at their respective base ends 32, while their respective bodies 30 extend outwardly from the circuit board 12. Thereby, the spacing between the antenna element 18a and the antenna element 18b is properly adjusted.

By appropriately setting the interval between the

antenna elements

18a and 18b arranged in parallel on the left and right sides, the circuit is formed in the area surrounded by the

antenna elements

18a and 18b and the connection portion 20 in plan view (inside the outline of these projection areas). A substrate 12 can be accommodated. In other words, the circuit board 12 has a width that fits between the antenna element 18a and the antenna element 18b, and has a size that fits in the area described above. The distance between the antenna element 18a and the antenna element 18b is set to such an extent that substantially no capacitive coupling occurs between them. The GPS antenna 14 is separated from both

antenna elements

18a and 18b so as not to overlap the projected planes of the

antenna elements

18a and 18b in plan view.

As shown in FIG. 2(B), the antenna unit 110 according to the comparative example differs from the present embodiment in that it does not have a connecting portion for connecting the pair of

antenna elements

18a and 18b. The presence or absence of this connecting portion 20 affects the isolation of the left and right TEL antennas 16 . The results of analysis performed to verify this will be described below.

FIG. 3 is a diagram showing the result of analyzing the frequency characteristics of the TEL antenna 16. FIG. FIG. 3A shows analysis results of isolation (dB), and FIG. 3B shows analysis results of radiation efficiency (dB). In each figure, the solid line indicates the characteristics of this embodiment, and the dashed line indicates the characteristics of the comparative example. The horizontal axis of each figure indicates frequency.

Regarding isolation, it is generally considered good if an absolute value of 10 dB or more can be secured. In this regard, the comparative example fails to secure 10 dB in the frequency range of 1200 MHz or less, whereas the present embodiment secures 10 dB in the entire frequency range including 1200 MHz or less.

On the other hand, regarding radiation efficiency, the higher the number, the better. In this regard, both the present embodiment and the comparative example are good in the frequency range of 1600 MHz or higher. On the other hand, in the frequency region below 1600 MHz, significant improvement is seen in this embodiment. According to this embodiment, it can be seen that not only the isolation but also the radiation efficiency is improved in the range of 800 MHz to 1200 MHz.

As described above, according to the present embodiment, for two monopole antennas arranged adjacently, by physically connecting the tips of the antenna elements (on the side opposite to the feed point), the low frequency band Good characteristics (radiation efficiency) can be ensured in a wide band without degrading isolation in . By arranging the circuit board 12 between the two monopole antennas (more specifically, the area surrounded by the two antenna elements and the connecting portion), it is possible to effectively utilize the space.

[Second embodiment]
FIG. 4 is a plan view showing the configuration of an antenna unit according to the second embodiment.
In the antenna unit 210 of this embodiment, the connecting portion 220 has an electrical length increasing structure for increasing the electrical length. This "electrical length increasing structure" includes a meandering structure having a plurality of folded portions 222 in the extending direction of the connecting portion 220, and the antenna characteristics are adjusted by setting the line width w1 and meandering width w2 of the meandering structure. It functions as an antenna characteristic adjustment structure. The length along the extending direction of the connecting portion 220 (the length along the meandering shape) is the same as that of the connecting portion 20 in which both tip portions 36 of the

antenna elements

18a and 18b are linearly connected as in the first embodiment. Greater than length. In this embodiment, the line width w1 is set to 5 mm, and the meandering width w2 is set to 20 mm.

FIG. 5 is a plan view showing the configuration of an antenna unit according to a modification. FIG. 5A shows Modification 1, and FIG. 5B shows Modification 2. FIG.
Modification 1 changes the line width w1 without changing the meandering width w2 of the meandering structure as compared with the second embodiment (FIG. 5A). Antenna unit 212 includes a connecting portion 230 having a meandering structure. In the illustrated example, the line width w1=2 mm and the meandering width w2=20 mm are set for the meandering structure.

On the other hand, in modification 2, the meandering width w2 is changed without changing the line width w1 of the meandering structure compared to the second embodiment (FIG. 5(B)). The antenna unit 214 has a connecting portion 232 having a meandering structure. In the illustrated example, the line width w1=5 mm and the meandering width w2=40 mm are set for the meandering structure. As described above, the antenna characteristics can be adjusted by appropriately setting the line width w1 and meandering width w2 of the meandering structure. Analysis results for verifying this are shown below.

FIG. 6 is a diagram showing the relationship between the line width of the meandering structure and the frequency characteristics. FIG. 6A shows analysis results of isolation (dB), and FIG. 6B shows analysis results of radiation efficiency (dB). In each figure, the solid line indicates the characteristics of the first embodiment that does not employ the meandering structure, and the others indicate the characteristics of the second embodiment that has the meandering structure and its modifications. The meandering width w2 is constant at 20 mm. Regarding the line width w1, the dotted line indicates a case of 5 mm (corresponding to the second embodiment), the dashed line indicates a case of 3 mm, and the one-dot chain line indicates a case of 2 mm (corresponding to the first modification). The horizontal axis of each figure indicates frequency.

According to this analysis result, by adopting the meander structure, both isolation and radiation efficiency can be significantly improved in the low frequency range of 1000 MHz or less. Isolation of 10 dB or more can be secured even in the frequency range of 1700 to 6000 MHz, and radiation efficiency is as good as in the case without the meander structure. In any frequency region, there is a slight difference in isolation depending on the line width w1.

FIG. 7 is a diagram showing the relationship between the meandering width of the meandering structure and the frequency characteristics. FIG. 7A shows analysis results of isolation (dB), and FIG. 7B shows analysis results of radiation efficiency (dB). The line width w1 is constant at 5 mm. Regarding the meandering width w2 in each figure, the solid line indicates 20 mm (corresponding to the second embodiment), the dotted line indicates 30 mm, the dashed line indicates 35 mm, and the one-dot chain line indicates 40 mm (corresponding to Modification 2). The horizontal axis of each figure indicates frequency.

From this analysis result, it can be seen that the isolation and radiation efficiency can also be adjusted by adjusting the meandering width w2 of the meander structure. In any frequency range, there is a slight difference in isolation depending on the meandering width w2. It can be seen that in the frequency region of 1200 MHz or less, the isolation decreases as the meandering width w2 increases. If the meandering width w2 is 35 mm or more, it becomes impossible to ensure isolation of 10 dB or more.

According to the present embodiment, by adopting a meandering structure in the connection portion and adjusting the line width and meandering width, the balance between isolation and radiation efficiency can be adjusted for a pair of monopole antennas, and the frequency characteristics can be improved. It was confirmed that In other words, depending on the balance between the line width and meandering width, the characteristics may be lower than those without the meander structure (first embodiment) in a specific frequency range. Therefore, it is preferable to adjust these according to the specifications (frequency band) of the monopole antenna. Regarding this embodiment, it was found that by setting the line width w1 to 2 mm or more and 5 mm or less and the meandering width w2 to 20 mm or more and 35 mm or less, the isolation can be improved particularly in the low frequency region.

[Third Embodiment]
FIG. 8 is a perspective view showing the configuration of an antenna unit according to the third embodiment.
Antenna unit 310 of the present embodiment has a connection portion 320 that is slightly different in structure from connection portion 220 of the second embodiment. The connecting portion 320 has stepped portions 322 at both ends so as to be maintained at a higher position than the main body 30 (the first extending portion and the second extending portion) of the antenna element 18 . Thereby, the cable connected to the vehicle-mounted device can be passed downward through the connection portion 320 and connected to the connector 22 .

According to this embodiment, it is possible to increase the degree of freedom in designing cable routing. In that case, a sufficient gap should be formed between the connecting portion 320 and the cable to prevent deterioration of the antenna performance. In addition, in this embodiment, the height of the stepped portion 322 is set to 10 mm or more.

Although the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to those specific embodiments, and that various modifications are possible within the scope of the technical idea of the present invention. Nor.

[Modification]
FIG. 9 is a plan view showing the configuration of an antenna unit according to a modification.
The antenna unit 410 of Modification 3 includes a circuit board 412 that is larger than that of the above embodiment. The circuit board 412 is a printed wiring board having a rectangular shape in plan view, and the antenna element 418a (first antenna element), the antenna element 418b (second antenna element), and the connection portion 20 are arranged on the outer edge of the circuit board 412 in plan view. are arranged along.

The

antenna elements

418a and 418b and the connecting portion 20 each have an elongated rectangular shape, are positioned above the circuit board 412, and constitute a U-shaped element unit 420 in plan view. The element unit 420 extends parallel to the top surface of the circuit board 412 . A base end portion 432 of each antenna element does not have a wide shape as in the above embodiment. The inner end portion of the base end portion 432 is bent downward at right angles to form the power supply portion 34 . A lower end of the power feeding portion 34 is connected to the power feeding points (P1, P2).

On the upper surface of the circuit board 412, the area surrounded by the

antenna elements

418a and 418b and the connecting portion 20 (inside the projected area of the element unit 420) is sufficiently large, so that a patch antenna or the like other than the GPS antenna 14 can be arranged. There is extra space. Antenna elements such as patch antennas are arranged to avoid circuit components such as chips on the circuit board 412 . According to this modified example, the degree of freedom in design, such as circuit layout utilizing the extra space, is increased.

In addition, in this modified example, an example is shown in which the circuit board 412 is configured to be slightly larger than the element unit 420 in plan view, and its outer edge is positioned outside the element unit 420 . In another modification, the circuit board 412 may be configured to be smaller than the element unit 420 in plan view, and its outer edge may be positioned inside the element unit 420 . Alternatively, the circuit board 412 may be sized such that its outer edge is positioned within the projection plane of the element unit 420 . In either case, the

antenna elements

418a and 418b and the connection portion 20 are arranged along the outer edge of the circuit board 412 in plan view.

In addition, in this modification, the antenna element and the connecting portion of the TEL antenna (monopole antenna) are configured by a conductor plate as in the above embodiment, but in other modifications, the upper surface of the circuit board 412 ( surface), bottom surface (rear surface), or a wiring pattern mounted in a layer structure. In other words, the wiring pattern forming the antenna element and connection portion of the monopole antenna may be arranged along the outer edge of the circuit board 412 .

FIG. 10 is a plan view showing the configuration of an antenna unit according to another modification. FIG. 10A shows Modification 4, and FIG. 10B shows Modification 5. FIG.
In these modified examples, the frequency characteristics of the TEL antenna (monopole antenna) are adjusted by configuring the antenna element to have a tapered shape in plan view.

That is, in Modification 4, the antenna element 518 has a tapered shape in which the width gradually decreases from the base end portion 532 side toward the tip end portion 36 in the front-rear direction (FIG. 10(A)). Antenna element 518 also has a tapered shape in which the width decreases in the left-right direction as it approaches feeding point P1.

On the other hand, in Modification 5, the antenna element 618 has a tapered shape in which the width gradually increases from the base end portion 632 side toward the tip end portion 36 in the front-rear direction (FIG. 10(B)). In other words, the antenna element 618 has a tapered shape whose width decreases as it approaches the feeding point P1.

In this way, by configuring the antenna element so that the width becomes smaller as it approaches the feeding point (P1, P2), it is possible to improve the antenna performance in a high frequency band, for example. By adjusting the taper angle of the tapered shape, antenna performance can be improved in a specific frequency band.

In this modified example, a tapered shape is exemplified as a specific shape of the antenna element, but a stepped shape or other shape may be used as long as the width of the antenna element gradually decreases toward the feeding point. Further, depending on the frequency band to be improved, the width of the antenna element may be gradually increased. Further, as in the above embodiment, the width of the antenna element may be gradually decreased or increased only in the vicinity of the feeding point.

FIGS. 11 and 12 show the analysis and results of the effects of the first embodiment.
FIG. 11A shows an analysis model of the first embodiment, and FIG. 11B shows an analysis model of a comparative example. The configuration of the antenna unit 10 according to the first embodiment has already been described. On the other hand, the antenna unit 112 according to the comparative example has a structure in which left and

right antenna elements

118a and 118b are separated by providing a slit in the center of the connecting portion 20 of the first embodiment. The antenna element 118a functions as a "first antenna element", and the antenna element 118b functions as a "second antenna element". In this comparative example, the gap G between the tips of the

antenna elements

118a and 118b is 1 mm.

FIG. 12 is a diagram showing analysis results of frequency characteristics. FIG. 12A shows analysis results of isolation (dB), and FIG. 12B shows analysis results of radiation efficiency (dB). In each figure, the solid line indicates the characteristics of the first embodiment, and the dashed line indicates the characteristics of the comparative example. The horizontal axis of each figure indicates frequency.

According to this analysis, in the low frequency range of 1200 MHz or less (especially 800 MHz or more and 1200 MHz or less), the first embodiment provides better isolation and radiation efficiency than the comparative example. On the other hand, almost no difference between the two is recognized in the high frequency region. This point is as described in the explanation of the first embodiment.

In another analysis (not shown), the influence on the other antenna element was verified by calculating the current distribution when the current was excited only at the feeding point of one of the first and second antenna elements. Specifically, the feeding point P2 (second feeding point) of the antenna element 118b is in an excited state, and the feeding point P1 (first feeding point) of the antenna element 118a is in a non-excited state.

According to this analysis, when a current is excited at one feeding point P2 with a frequency of 900 MHz, in the first embodiment, the current amplitude near the other feeding point P1 becomes small, that is, the current waveform can be a node. , and as a result, it was found that the isolation was good. On the other hand, in the comparative example, it was found that the current amplitude near the feeding point P1 was large, that is, the current waveform had an antinode, and as a result, good isolation could not be obtained. This result matches the analysis result of FIG.

In this analysis, one feeding point P2 is excited and the other feeding point P1 is de-excited, but the same applies when the excited states are exchanged. If the frequencies are the same, the current waveform (the positional relationship between the antinode and the node) at the feed point on the non-excited side will be the same.

In other words, in the first embodiment, in the low frequency region, the waveform of the current excited at the feeding point P1 becomes a node near the feeding point P2, and the waveform of the current excited at the feeding point P2 becomes a node at the feeding point P1. The lengths of the antenna element 18a, the antenna element 18b, and the connection portion 20 are set so as to form a node in the vicinity of .

FIG. 13 shows an analysis and its results regarding the effects of the second embodiment. FIG. 13A shows analysis results of isolation (dB), and FIG. 13B shows analysis results of radiation efficiency (dB). In each figure, the solid line indicates the characteristics of the second embodiment (more specifically, the modified example 1 of FIG. 5A), and the dashed line indicates the characteristics of the comparative example. The horizontal axis of each figure indicates frequency.

The configuration of the antenna unit 212 according to the second embodiment (modification 1) has already been described. On the other hand, the antenna unit according to the comparative example has a structure in which a slit is provided in the center of the connecting portion 230 of the modified example 1 to separate the left and right antenna elements. One of the antenna elements functions as a "first antenna element" and the other antenna element functions as a "second antenna element". Also in this comparative example, the gap between the tips of the left and right antenna elements is 1 mm.

According to this analysis, in the frequency range of 1200 MHz or less (especially 800 MHz or more and 1200 MHz or less), the second embodiment (Modification 1) provides better results than the comparative example in terms of isolation and radiation efficiency.

In another analysis (not shown), the influence on the other antenna element was verified by calculating the current distribution when the current was excited only at the feeding point of one of the first and second antenna elements. According to this analysis, when a current is excited at one feeding point P2 with a frequency of 900 MHz, in the second embodiment (modification 1), the current waveform near the other feeding point P1 can be used as a node. ration was found to be good. On the other hand, in the comparative example, it was found that the current waveform near the feeding point P1 has an antinode and good isolation cannot be obtained. This result matches the analysis result of FIG.

In other words, in the second embodiment (Modification 1), in the low frequency region, the waveform of the current excited at the feeding point P1 becomes a node near the feeding point P2, and the current excited at the feeding point P2 becomes a node. The lengths of the antenna element 18a, the antenna element 18b, and the connection portion 230 are set so that the waveform has a node near the feeding point P1.

Although FIGS. 11 to 13 show an example of analysis results for a specific form, similar results can be obtained for other forms. That is, the connecting portion has a meandering structure and has various forms with different line widths and meandering widths, a form in which the end of the connecting part has a rounded R shape, and a form in which the connecting part is inclined from the end toward the center. (A form forming an acute or obtuse angle with respect to the left and right antenna elements, a form approaching or separating from the patch antenna from the ends toward the center). Other forms are also applicable.

That is, the waveform of the current excited at the first feeding point becomes a node near the second feeding point, and the waveform of the current excited at the second feeding point becomes a node near the first feeding point. Isolation and radiation efficiency can be improved if the lengths of the first antenna element, the second antenna element, and the connecting portion are set.

14 is a plan view showing the configuration of an antenna unit according to modification 6. FIG.
In this modification, a metal plate 710 is added to the antenna unit 10 of the first embodiment. The metal plate 710 is a sheet metal component provided to face the side of the circuit board 12 opposite to the patch antenna (GPS antenna 14).

The metal plate 710 has a symmetrical structure with respect to the center line L in plan view, and is arranged in a region surrounded by the antenna element 18a, the antenna element 18b, and the connection portion 20. The metal plate 710 may be arranged at the same height position as the

antenna elements

18a and 18b. With such a configuration, it is possible to improve the gain characteristics and axial ratio characteristics of the patch antenna.

FIG. 15 is a diagram showing the effect of the configuration of Modification 6. FIG. 15A shows elevation angle-average gain characteristics (frequency: 1575 MHz), FIG. 15B shows frequency-zenith gain characteristics, and FIG. 15C shows frequency-zenith axial ratio characteristics. In each figure, the solid line indicates the characteristics of Modification 6, and the dashed line indicates the characteristics of Comparative Example. The horizontal axis of each figure indicates frequency. Note that the comparative example referred to here has a configuration without the metal plate 710 and corresponds to the first embodiment. The zenith axial ratio is an index indicating the roundness of the received radio wave when the patch antenna receives the radio wave in the GNSS frequency band from an artificial satellite, in other words, the degree of distortion.

According to this modified example, by adding the metal plate 710, the average gain characteristic is improved regardless of how the elevation angle of the GNSS antenna (GPS antenna 14) is set (FIG. 15(A)). Also, it can be seen that the zenith gain characteristic and the zenith axial ratio characteristic are improved in the vicinity of the frequency region corresponding to the GNSS frequency band (FIGS. 15(B) and 15(C)).
In another modification, a member made of conductive resin or another conductive material may be provided as the “conductive member” instead of the metal plate 710 .

In the above-described first embodiment, an example was shown in which the antenna element 18 and the connecting portion 20 were integrally formed by punching out a single conductor plate, and the width and thickness of the connecting portion 20 were made equal to the main body 30 of the antenna element 18. In a modified example, at least one of the width and thickness of the connecting portion 20 may be different from that of the main body 30 . The antenna element and the connecting portion may be separately molded and joined, and in that case, materials with different thicknesses may be used for both. Also, the width and thickness of the connecting portion 20 may be changed in the extending direction. You may change the shape of the connection part 20 into shapes other than a planar view rectangle.

Although the configuration in which the antenna element 18 extends toward the rear of the circuit board 12 is shown in the above embodiment, it may be configured to extend toward the front of the circuit board 12 . Alternatively, it may be configured to extend forward and backward of the circuit board 12 . The "front-to-back direction of the circuit board" can include both the front and rear of the circuit board.

In the above-described second embodiment and modified example, the configuration is shown in which the entire area from one end to the other end of the connecting portion has a meandering structure. Also, a periodic rectangular wave shape is exemplified as the meander structure. In other modifications, the meandering structure may be provided partially, for example, limited to the central region, limited to the vicinity of the ends, or arranged at predetermined intervals, rather than the entire connecting portion. Moreover, the meandering structure may have a curvilinear wave shape, or may have no periodicity. The thickness may be partially varied along the meandering shape.

In the above-described second embodiment, an example in which the electrical length is increased by forming the connecting portion 220 from the same metal as the antenna element 18 and forming a meandering structure (electrical length increasing structure) is shown. In a modification, the electrical length may be adjusted by forming the connecting portion from a metal different from that of the antenna element without integrally molding the connecting portion and the antenna element. Alternatively, the electrical length may be adjusted by configuring the connecting portion by connecting a metal plate and a circuit element such as a chip inductor. Conversely, for the connection portion, an electrical length reduction structure may be employed in which the electrical length is made shorter than when the first antenna element and the second antenna element are linearly connected. That is, the connection portion may have an "electrical length adjustment structure" that makes the electrical length different from that in the case where the first antenna element and the second antenna element are linearly connected.

In the above embodiment, the elements of the GPS antenna 14 are positioned higher than the elements of the TEL antenna 16, but the elements of the GPS antenna 14 may be positioned lower than the elements of the TEL antenna 16. In that case, the feeding portion 34 may be bent downward at the base end portion 32 of the antenna element 18 and connected to the circuit board 12 from above.

In the above embodiment, the GPS antenna 14 was exemplified as the patch antenna provided on the circuit board 12, but instead of this, a patch antenna compatible with GLONASS (Global Navigation Satellite System) and other GNSS (Global Navigation Satellite Systems) is provided. good too. Alternatively, a patch antenna capable of receiving satellite radio, such as SiriusXM, may be provided. A patch antenna for ETC or VICS may be provided.

As shown in FIG. 2, when there is room in the area surrounded by the first antenna element, the second antenna element, and the connecting portion in a plan view, the circuit board 12 can be enlarged in the front-rear direction so that a plurality of patch antennas can be formed. may be arranged in the front and rear. Also in that case, the circuit board 12 is accommodated in the area surrounded by the first antenna element, the second antenna element, and the connecting portion (inside the outline of these projected areas).

When an ETC antenna is included in a plurality of patch antennas, the antenna element of the ETC antenna may be inclined with respect to the circuit board 12 from the viewpoint of directivity. In such a case, it is preferable to arrange the ETC antenna in front of the other patch antennas.

Although the antenna element is made of metal in the above embodiment, it may be made of conductive resin or other conductive material.

In the above embodiment, so-called inverted L antennas are illustrated as two monopole antennas, but inverted F antennas may be used. Also, a rod-shaped monopole antenna or a tapered monopole antenna may be used.

In Modifications 3 to 5, the connecting portion 20 has a rectangular shape similar to that of the first embodiment. It goes without saying that this is also a good thing.

In the above embodiment, the antenna device is installed inside the instrument panel, but it may be installed at other positions on the vehicle body. Further, the antenna device is not limited to a vehicle, and may be an antenna device installed in a ship or other means of transportation.

In the above embodiment, the two monopole antennas arranged adjacently (arranged in parallel) are TEL antennas, but other antennas compatible with MIMO may be used. Further, in the above embodiment, the two monopole antennas extend in the front-rear direction parallel to the circuit board, but they may extend perpendicularly to the circuit board. Also in that case, the circuit board may have a width that fits between the first antenna element and the second antenna element.

It should be noted that the present invention is not limited to the above embodiments and modifications, and can be embodied by modifying the constituent elements without departing from the scope of the invention. Various inventions may be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments and modifications. Also, some constituent elements may be deleted from all the constituent elements shown in the above embodiments and modifications.

1 Antenna device, 10 Antenna unit, 12 Circuit board, 14 GPS antenna, 16 TEL antenna, 18 Antenna element, 20 Connection part, 22 Connector, 24 Ground area, 32 Base part, 34 Feeding part, 36 Tip part, 110 Antenna unit, 212 antenna unit, 214 antenna unit, 220 connection part, 222 folded part, 230 connection part, 232 connection part, 310 antenna unit, 320 connection part, 322 step part, 410 antenna unit, 412 circuit board, 420 element unit, 432 base end, 518 antenna element, 532 base end, 618 antenna element, 632 base end, P1 feeding point, P2 feeding point.

Claims

a circuit board having a ground area;
a first antenna element having a proximal end connected to a first feeding point provided on the circuit board and forming a first monopole antenna;
a second antenna element having a proximal end connected to a second feeding point provided on the circuit board and forming a second monopole antenna;
a connecting portion that connects the tip portion of the first antenna element and the tip portion of the second antenna element;
An antenna device comprising:
The first antenna element has a first base end portion connected to the first feeding point, and a first extension portion extending from the first base end portion in the front-rear direction of the circuit board,
The second antenna element has a second base end connected to the second feeding point, and a second extension extending from the second base end in the front-rear direction of the circuit board,
2. The antenna according to claim 1, wherein the connecting portion connects the first extending portion and the second extending portion in the left-right direction of the circuit board on the side opposite to each base end portion. Device.
3. The antenna device according to claim 1, wherein the circuit board has a width that fits between the first antenna element and the second antenna element.
4. The circuit board according to any one of claims 1 to 3, wherein the circuit board has a size that fits within an area surrounded by the first antenna element, the second antenna element, and the connecting portion in plan view. antenna device.
The antenna device according to claim 4, wherein the circuit board is provided with a patch antenna.
The antenna device according to any one of claims 1 to 5, wherein the first antenna element and the second antenna element are arranged along the outer edge of the circuit board.
7. The connection portion according to claim 1, wherein the connection portion has an electrical length adjustment structure that makes the electrical length different from that in the case where the first antenna element and the second antenna element are linearly connected. An antenna device as described.
The antenna device according to any one of claims 1 to 7, wherein the connecting portion has an electrical length increasing structure for increasing the electrical length.
The antenna device according to claim 8, wherein the electrical length increasing structure includes a meandering structure having a plurality of folded portions in the extending direction of the connection portion.
The antenna device according to claim 9, comprising an antenna characteristic adjustment structure in which antenna characteristics are adjusted by setting the line width and meandering width of the meandering structure.
11. The antenna device according to claim 10, wherein the meandering structure has a line width of 2 mm or more and 5 mm or less and a meandering width of 20 mm or more and 35 mm or less.
The waveform of the current excited at the first feeding point becomes a node near the second feeding point, and the waveform of the current excited at the second feeding point becomes a node near the first feeding point. The antenna device according to any one of claims 1 to 11, wherein the lengths of the first antenna element, the second antenna element, and the connection portion are set as follows.
further comprising a conductive member provided to face a side surface of the circuit board opposite to the patch antenna;
6. The antenna device according to claim 5, wherein the conductive member is arranged in a region surrounded by the first antenna element, the second antenna element, and the connecting portion in plan view.