Patent Description:
In an antenna device for satellites, for example, Global Navigation Satellite System (GNSS), which is arranged in an instrument panel of an automobile (in particular, at a position close to a windshield) in a related art, there has generally been used a patch antenna, and a metal plate being a ground plate is normally required. Further, a TEL (telephone) antenna is required to be mounted together with the GNSS satellite antenna. In the related art, a vertically polarized wave has been required.

However, in Long Term Evolution (LTE) using Multiple-Input Multiple-output (MIMO) technology, a horizontally polarized wave may be required to be generated in a horizontal plane. On this occasion, when an element is formed on the ground plate, there has been a problem in that the horizontally polarized wave is hardly generated in the plane parallel to the ground plate.

This problem is explained below. <FIG> shows a basic structural example of a GNSS patch antenna arranged in an instrument panel of an automobile to receive GNSS signals. A patch antenna <NUM> includes a radiation electrode <NUM> formed on a main surface of a dielectric body <NUM> and a ground plate <NUM> as a ground conductor provided on an opposite side of the main surface. A low noise amplifier (LNA) substrate <NUM> configured to amplify a received signal is arranged between the dielectric body <NUM> and the ground plate <NUM>. A surface opposite to the main surface of the dielectric body <NUM> is a ground (GND) electrode to be electrically connected to the ground plate <NUM>. The ground plate <NUM> is required to, due to antenna characteristics, have an area considerably larger than an area of a floor of the dielectric body <NUM>. In the GNSS patch antenna, the groundplate <NUM> is arranged horizontally, and the radiation electrode <NUM> is arranged upward, that is, is set at an elevation angle of <NUM> degrees.

<FIG> shows a conventional composite antenna device including a TEL antenna element <NUM> serving as a telephone transmission and/or reception antenna in addition to the GNSS patch antenna of <FIG>. The same members as those of <FIG> are denoted by the same symbols.

The TEL antenna element <NUM> of <FIG> stands in a vertical direction on the LNA substrate <NUM> with respect to the ground plate <NUM> and then extends parallel to the ground plate <NUM>. In this case, a portion vertically extending in the vertical direction to the ground plate <NUM> of the TEL antenna element <NUM> mainly generates an electromagnetic wave, and a polarized wave is generated in a perpendicular direction with respect to the ground plate <NUM>. The portion of the TEL antenna element <NUM> extending parallel to the ground plate <NUM> in a horizontal direction is closed to the ground plate <NUM>. For that reason, a current in an opposite phase is generated in the ground plate <NUM>, and an electromagnetic wave to be a polarized wave (horizontally polarized wave) parallel to the ground plate <NUM> is not generated. Substantially the same structure of <FIG> is disclosed in Patent Literature <NUM> below. However, a vertically polarized wave of an electromagnetic wave generated by the telephone antenna becomes strong for the same reason.

<FIG> is a view for illustrating an example including a flat-plate-like TEL antenna element <NUM> as a TEL transmission and/or reception antenna on the ground plate <NUM> in addition to the GNSS patch antenna of <FIG>, and the same members as those of <FIG> are denoted by the same symbols. As described in <FIG>, the TEL antenna element <NUM> is provided to be adjacent parallel to the ground plate <NUM>, and hence an electromagnetic wave of a polarized wave (horizontally polarized wave) parallel to the ground plate <NUM> is not generated for the same reason.

Patent Literature <NUM> discloses a radio wave receiver comprising a planar circuit board having a non-conductive region and an antenna being arranged in parallel to the non-conductive region of the circuit board.

Patent Literature <NUM> is directed at a vehicle-mounted integrated antenna device comprising a base plate made of a metal material as well as a GPS antenna and a short-range wireless communication antenna having directivity in a horizontal direction. The short-range wireless communication antenna is arranged in a region next to a protrusion extending within a cavity of the base plate and comprising a hook hole portion for mounting the base plate to a bracket holder. The short-range wireless communication antenna comprises a horizontal side portion aligned perpendicular to the base plate as well as a horizontal side portion aligned parallel to the base plate.

Patent Literature <NUM> relates to an antenna assembly comprising a ground spot and meander dipole antennas arranged next to the ground spot.

Patent Literature <NUM> discloses a wide band co-planar waveguide antenna comprising an outer perimeter conductive ground plane defining a cut-out elliptical slot accommodating an antenna radiating element.

Patent Literature <NUM> relates to a communication device including a ground element and an inverted-F antenna element with a single branch, the antenna element disposed adjacent to an edge of the ground element.

Patent Literature <NUM> is directed at an antenna device comprising a ground part and a loading section arranged at an insulating substrate next to the ground part. A self-resonance frequency of the loading section is higher than an antenna operating frequency, such that the antenna device is not self-resonating when considering the antenna operating frequency as a reference.

Patent Literature <NUM> discloses an antenna that comprises a conductive area as well as a first dipole leg and a second dipole leg. A conductive strip forming the second dipole leg is co-planar with the conductive area comprising a ground plate.

Patent Literature <NUM> discloses an antenna with a radiating strip comprising a meandering portion. The radiating strip is co-planar with a ground plane.

Patent Literature <NUM> discloses an inverted F antenna, wherein a radiator and a ground plane are located on one plane of a substrate.

The present invention has been made in view of the above described circumstances, and has an object thereof to provide an antenna device capable of transmitting and/or receiving an electromagnetic wave of a horizontally polarized wave when an antenna element is horizontally arranged in the antenna device including a ground conductor.

The object is satisfied by an antenna device comprising the features of claim <NUM>.

In the present disclosure, the expression "an antenna element which is a resonant type" refers to an antenna element capable of transmitting or receiving an electric wave by resonance.

According to the antenna device of the present invention, the antenna device includes the ground conductor, and the antenna element extending at a position so as not to overlap with the ground conductor in the plane substantially parallel to the ground conductor, thereby being capable of transmitting and/or receiving the electromagnetic wave of a horizontally polarized when the antenna element is horizontally arranged.

Hereinafter, preferred embodiments of the present invention are described in detail with reference to the drawings. The same or equivalent structural elements, members, processes, and the like, illustrated in each drawing are denoted by the same symbols, and duplicate description thereof is omitted as appropriate. Further, the embodiments do not limit the invention and are illustrative. All of the features and combinations described in the embodiments are not necessarily essential to the present invention.

<FIG> illustrate an antenna device according to a first embodiment of the present invention. In these drawings, an antenna device <NUM> includes a GNSS patch antenna <NUM> arranged in an instrument panel of an automobile as a vehicle to receive GNSS signals, a ground plate <NUM> serving as a ground conductor, and a TEL antenna element <NUM> as an example of an antenna element of a resonant type. In the following description, the GNSS patch antenna is referred to as "patch antenna", and the TEL antenna element is referred to as "antenna element". Further, a portion including the patch antenna <NUM>, the ground plate <NUM>, and the antenna element <NUM> may be referred to as "body portion of the antenna device" or "main portion".

A portion (a portion of an end surface in this example) of the ground plate <NUM> is cut out toward an inner side thereof. Hereinbelow, for the sake of convenience, the cut-out portion is referred to as "notch". In the illustrated example, a notch <NUM> is formed to have both a right and left edge portions <NUM> with a predetermined width of an end surface of one side of the ground plate <NUM>. The antenna element <NUM> is, for example, a flat plate element having an L-shape, and is provided at a position not overlapping with the ground plate <NUM> in a plane substantially parallel to an LNA substrate <NUM> and the ground plate <NUM>, in other words, at the position in the notch <NUM>. At this time, a power feeding side (feeding end) of the antenna element <NUM> may be partially overlapped with the ground plate <NUM>, but the main portion of the antenna element <NUM> is configured not to overlap with the ground plate <NUM>.

One end serving as the feeding end (end portion on a short side in the L-shape) of the antenna element <NUM> is connected to a feeding conductive pattern (not shown in the drawings) of the LNA substrate <NUM>. Another end (end portion on a long side in the L-shape) of the antenna element <NUM> is an open end. Further, the antenna element <NUM> is arranged so as not to protrude from the notch <NUM>. The structure of the patch antenna <NUM> is similar to that of <FIG>, and description thereof is omitted.

In the structure of the first embodiment, the notch <NUM> is formed at a portion overlapping with the antenna element <NUM>. For that reason, an influence by a current in a reversed phase, which is generated in the ground plate <NUM> when the power is supplied to the antenna element <NUM>, can be eliminated, and hence variation in electric field is generated in a plane parallel to the antenna element <NUM> and the ground plate <NUM>, and a horizontally polarized wave is generated when the antenna element <NUM> is arranged horizontally to the ground. Further, a high frequency current is easily formed as a standing wave across a whole length of inner peripheral edge portions 22a, 22b, and 22c of three sides of the notch <NUM>. As compared to a case in which both of the right and left edge portions <NUM> are not left by being cut out straight, satisfactory antenna transmission and reception characteristics can be obtained in a desired frequency band.

<FIG> is a graph showing a result example of a measurement for gain in the horizontal plane of the antenna device <NUM>, and frequency characteristics of average gain (dBi) in the horizontally polarized waves are shown in comparison with a case of vertically polarized waves. It can be seen that, from <FIG>, the average gain in the vertically polarized waves is very small, but the average gain in the horizontally polarized waves is sufficiently large.

According to this embodiment, the following effects can be obtained.

<FIG> shows a second embodiment of the antenna device according to the present invention. In this drawing, the antenna device <NUM> includes the patch antenna <NUM> and the antenna element <NUM>, but the ground plate <NUM> has a different shape. That is, a notch <NUM> is formed to have one side edge portion <NUM> with a predetermined width in a part of an end surface of the ground plate <NUM>. Other structures are similar to those of the first embodiment.

In this case, the antenna element <NUM> is at the position so as not to overlap with the groundplate <NUM> in the plane substantially parallel to the ground plate <NUM>, that is, at the position in the notch <NUM> formed in the ground plate <NUM>. For that reason, an influence by a current in a reversed phase, which is generated in the ground plate <NUM> when the power is supplied to the antenna element <NUM>, can be eliminated, and when the antenna device <NUM> is arranged horizontally to the ground, an electromagnetic wave of a horizontally polarized wave can be transmitted and received satisfactorily.

Further, the total length of the inner peripheral edge portions of the notch <NUM> is longer than that in the case in which the notch is formed linearly without having the one side edge portion <NUM>. For that reason, satisfactory antenna transmission and reception characteristics can be obtained in desired frequency bands. Still further, the antenna element <NUM> is configured not to protrude from the notch <NUM>, and hence a mounting area for the antenna device <NUM> is not increased due to mounting the antenna element <NUM>.

<FIG> shows a third embodiment of the antenna device according to the present invention. In this drawing, an antenna device <NUM> includes the patch antenna <NUM> and the antenna element <NUM>, but the ground plate <NUM> has a different shape. That is, as a result of one end surface of the ground plate <NUM> which was cut out linearly from one edge to another edge, it seems as if the notch <NUM> described above were not formed. Other structures are similar to those in the first embodiment.

In this case, the antenna element <NUM> is positioned at the position so as not to overlap with the ground plate <NUM> in the plane substantially parallel to the groundplate <NUM>. For that reason, an influence by a current in a reversed phase, which is generated in the ground plate <NUM> when the power is supplied to the antenna element <NUM>, can be eliminated, and when the antenna device <NUM> is arranged horizontally to the ground, an electromagnetic wave of a horizontally polarized wave can be transmitted and received satisfactorily.

<FIG> shows a fourth embodiment of the antenna device according to the present invention. In this drawing, an antenna device <NUM> includes the patch antenna <NUM> and an antenna element <NUM>. The antenna element <NUM> is integrally formed with the ground plate <NUM>. That is, the antenna element <NUM> has a plurality of end portions, one end of which is electrically connected to the ground plate <NUM> (conductive surface), and another end of the antenna element <NUM> is used as a feeding end <NUM>. A shape, especially, an arrangement or the shape of the antenna element <NUM> illustrated in <FIG> is illustrative, and can be changed in accordance with a resonant length of a frequency to be used. Further, the antenna element <NUM> may be formed as a conductor plate of a separate component instead of being integrally formed with the ground plate <NUM>, and one end thereof may be connected by soldering or the like. Other structures are similar to those of the first embodiment.

In this embodiment, the antenna element <NUM> is positioned at the position so as not to overlap with the ground plate <NUM> in the plane substantially parallel to the ground plate <NUM>. For that reason, an influence by a current in a reversed phase, which is generated in the ground plate <NUM> when the power is supplied to the antenna element <NUM>, can be eliminated, and when the antenna device <NUM> is arranged horizontally to the ground, an electromagnetic wave of a horizontally polarized wave can be transmitted and received satisfactorily.

A fifth embodiment of the antenna device according to the present invention is explained with reference to <FIG>. As illustrated in these drawings, the antenna device <NUM> includes a substrate <NUM> on which the patch antenna <NUM> and the antenna element <NUM> (<FIG> and <FIG>) are provided, the ground plate <NUM> as a ground conductor fixed to the substrate <NUM>, and a holder <NUM> which accommodates the body portion of the antenna device including the substrate <NUM> and the ground plate <NUM>, and which is detachable from and attachable to an antenna attachment mechanism (not shown in the drawings) provided in the vehicle. The substrate <NUM> is fixed to the ground plate <NUM> at a plurality of positions by screws <NUM>. The holder <NUM> holds the right and left edge portions <NUM> of the ground plate <NUM>.

In this case, as illustrated in <FIG> and <FIG>, the antenna element <NUM> is formed as a conductive pattern on a bottom surface of the substrate <NUM> (surface opposite to a mount surface for the dielectric body <NUM> of the patch antenna <NUM>). The antenna element <NUM> is arranged at a position so as to overlap with the notch <NUM> which is formed in the ground plate <NUM> in a plane parallel to the substrate <NUM> and the ground plate <NUM>. Though a GND conductive pattern <NUM> is formed as one example of a conductive surface so as to include a region, on which the dielectric body <NUM> is arranged, on an upper surface of the substrate <NUM>, the antenna element <NUM> is formed on a rear side region of a square region <NUM> at an upper surface in which the GND conductive pattern <NUM> is not formed.

The antenna element <NUM> has, for example, an F-shape, and includes a long element portion 30a and a short element portion 30b. The long element portion 30a is arranged to be close to an edge (in the case illustrated, along the edge) facing an opening of the notch <NUM>, and the short element portion 30b is arranged at an inner side of the long element portion 30a. One end serving as the feeding end of the antenna element <NUM> is conductive to a feeding conductive pattern <NUM> of the substrate <NUM> to be electrically connected to a terminal of a connector <NUM> fixed to the bottom surface of the substrate <NUM>. Received signals by the patch antenna <NUM> are also transmitted to another terminal of the connector <NUM>. As a result, the patch antenna <NUM> and the antenna element <NUM> are electrically connected to an in-vehicle electronic device via the connector <NUM>. Other structures are similar to those of the first embodiment.

As illustrated in <FIG> and <FIG>, the holder <NUM> includes a bottom surface portion <NUM>, and a frame-shaped portion <NUM> having a shape without one side of a square frame (U-shape) which extends from an edge of the bottom surface portion <NUM>. Both the edge portions <NUM> of the ground plate <NUM> are inserted and held in grooves <NUM> between protruding portions <NUM> formed on right and left inner surfaces toward an opening of the frame-shaped portion <NUM> and the bottom surface portion <NUM>. Here, in <FIG>, when a width direction of the opening of the frame-shaped portion <NUM> is defined as a lateral direction, and a direction orthogonal to the lateral direction is defined as a longitudinal direction, lengths in the lateral direction and a length in the longitudinal direction of the ground plate <NUM> are set to a size approximately the same as a width in the lateral direction and a length in the longitudinal direction of the bottom surface portion <NUM> of the holder facing the ground plate <NUM>. That is, the holder <NUM> is set to have a shape and a size capable of accommodating the body portion of the antenna device which includes the substrate <NUM> mounted with the patch antenna <NUM> and the antenna element <NUM> and which includes the ground plate <NUM> fixed to the substrate <NUM>. The holder <NUM> is fixed in the instrument panel.

According to the structure of the fifth embodiment, in addition to the effects of the first embodiment described above, the following effects can be obtained.

As described above, when the ground plate <NUM> is required to have a wide area, though the present invention is effective to generate an electromagnetic wave of a polarized wave parallel to the antenna elements <NUM> and <NUM> substantially parallel to the ground plate <NUM>, it is understood by those skilled in the art that each structure element and each process of the first to the fifth embodiments can be modified variously within a range of claims. Various modification examples are described below.

In the first embodiment to the third embodiment, the examples are illustrated in which the antenna element <NUM> has an L-shape, but as long as a horizontally polarized wave can be generated, the shape is not limited to the L-shape but may be the F-shape or the like of the fifth embodiment.

The patch antenna <NUM> is not limited for the GNSS, and may be mounted for other satellites such as GPS (satellite broadcasting reception, etc.).

A sixth embodiment of the antenna device according to the present invention is explained with reference to <FIG>. <FIG> is an external perspective view of the body portion of the antenna device in this embodiment. An antenna device <NUM> of this embodiment is slightly different from that of the fifth embodiment in the shapes and the structures of the ground plate <NUM> and the substrate <NUM>, and an antenna element <NUM>. Other structures are the same as those of the fifth embodiment. That is, in the antenna device <NUM> of this embodiment, both the right and left edge portions <NUM> of the groundplate <NUM> are shorter than those of the fifth embodiment, therefore, an area of the notch <NUM> in a concave shape is smaller by that size. Mounting holes <NUM> to an antenna cover (not shown) are formed in both the right and left edge portions <NUM>. The body portion of the antenna device fixed with the antenna cover is inserted in and held by the holder <NUM>. The antenna device <NUM> having the body portion of the antenna device held by the holder <NUM> is fixed in the instrument panel.

Further, the substrate <NUM> fixed substantially parallel to the surface of the ground plate <NUM> has, for example, an integral shape in which a square and both ends thereof form an approximate trapezoid, and the GND conductive pattern <NUM> as a conductive surface is formed on a portion except the approximate trapezoidal region <NUM>. The GND conductive pattern <NUM> is electrically connected to the ground plate <NUM>. The patch antenna <NUM> is provided on a predetermined portion of the GND conductive pattern <NUM>, for example, on a surface of a substantially central portion through intermediation of the dielectric body <NUM>.

A length between both ends of the substrate <NUM> is substantially the same as a length of the ground plate <NUM> in the same direction. Further, a distal end portion of the approximate trapezoidal region <NUM> of the substrate <NUM> is on a line connecting distal end portions of the right and left end portions <NUM> of the ground plate <NUM>.

The approximate trapezoidal region <NUM> as a part of the substrate <NUM> forms a non-conductive surface, which is exposed from the notch <NUM>, having a radio wave transmission property, and the antenna element <NUM> is a conductive pattern formed on the non-conductive surface. Thus, the antenna element <NUM> is provided at a position so as not to overlap with the ground plate <NUM> in a plane substantially parallel to the ground plate <NUM>, and transmits or receives a polarized wave parallel to the ground plate <NUM>. The structure of such an antenna element <NUM> is illustrated in <FIG>.

<FIG> is a plan view for illustrating the body portion of the antenna device of <FIG> when viewed from below (antenna mount mechanism of the vehicle). The antenna element <NUM> includes a high-band portion <NUM> as a plate-shaped conductive pattern and a low-band portion <NUM> as a meander-shaped conductive pattern.

A distal end of the low-band portion <NUM> is open-ended, and, a proximal end thereof extends from a portion farther away with respect to the feeding end <NUM> of the high-band portion <NUM>. Further, the low-band portion <NUM> is formed such that an orientation of a portion at which the element is bent on a way along an outer periphery of the substrate <NUM> (hereinafter, "turn") and an element length are changed so as to be sized which allows signals in a low-band (<NUM> to <NUM>) of LTE to be transmitted and received.

The high-band portion <NUM> is designed to have a size which allows signals in a high-band (<NUM> to <NUM>) of LTE to be transmitted and received. The feeding conductive pattern <NUM> described above is electrically connected (conductive) to the feeding end <NUM> also serving as a proximal end of the high-band portion <NUM>.

The high-band portion <NUM> resonates at a higher frequency band than the low-band portion <NUM> to be relatively less susceptible to an influence by the ground plate <NUM>. For that reason, the high-band portion <NUM> is formed at a position closer to the ground plate <NUM> than the low-band portion <NUM>.

<FIG> is a VSWR characteristic graph. The vertical axis represents VSWR, and the horizontal axis represents a frequency (MHz). In <FIG>, a broken line is a VSWR characteristic example of the antenna device of <FIG> in which the ground plate <NUM> is provided as the same as the ground plate <NUM> of the antenna device <NUM>, and a solid line is a VSWR characteristic example of the antenna device <NUM> according to this embodiment. As illustrated in <FIG>, it can be seen that the antenna device <NUM> of this embodiment (solid line) has lower VSWR over entire frequency bands in the high-band and the low-band of LTE than the antenna device of <FIG> (broken line).

Further, the GND conductive pattern <NUM> having a larger area is formed around the patch antenna <NUM>, thereby impedance of the patch antenna <NUM> is easily matched to stabilize VSWR characteristics. Further, a distance to the antenna element <NUM> becomes longer to suppress mutual interference with the antenna element <NUM>.

A seventh embodiment of the antenna device according to the present invention is explained with reference to <FIG> is a plan view for illustrating the body portion of the antenna device of <FIG> when viewed from below (direction in which the groundplate <NUM> is mounted). For convenience, the ground plate <NUM> is omitted. An antenna device <NUM> of this embodiment is the same as the sixth embodiment except that the antenna element <NUM> is formed on the approximate trapezoidal region <NUM> (non-conductive surface exposed from the notch <NUM>) of the substrate <NUM> and a shape thereof are different from those illustrated in <FIG>.

The antenna element <NUM> includes a high-band portion <NUM> having a plate-shaped conductive pattern, a distal end of which being an open end, and a low-band portion <NUM> having a meander-shaped conductive pattern, a distal end of which also being an open end. A feeding end <NUM> is shared by the respective high-band portion <NUM> and the low-band portion <NUM>. That is, the conductive pattern (feeding end <NUM>), which is integral with the proximal end (feeding end <NUM>) of the high-band portion <NUM> and the proximal end of the low-band portion <NUM>, is electrically connected (conductive) to the feeding conductive pattern <NUM> which is not conductive to the GND conductive pattern <NUM>. The GND conductive pattern <NUM> is formed near the approximate trapezoidal region <NUM> and is a different conductive pattern from the GND conductive pattern <NUM>.

The high-band portion <NUM> resonates at a higher frequency band than the low-band portion <NUM> to be relatively less susceptible to an influence by the groundplate <NUM>. For that reason, the high-band portion <NUM> is formed at a position closer to the ground plate <NUM> than the low-band portion <NUM>.

In the example of <FIG>, though a length from the proximal end to the distal end of the high-band portion <NUM> (length in right and left directions in <FIG>) is shorter than a length from the proximal end to the distal end of the low-band portion <NUM> (length in the right and left directions in <FIG>), the antenna element <NUM> is only required to have a size to resonate in a high-band of LTE. Therefore, the pattern illustrated in <FIG> is not always necessary to be used.

<FIG> is a VSWR characteristic graph. The vertical axis represents VSWR, and the horizontal axis represents a frequency (MHz). In <FIG>, a broken line indicates a VSWR characteristic example of the antenna device <NUM> of the sixth embodiment, and a solid line indicates a VSWR characteristic example of the antenna device <NUM> of this embodiment. As illustrated in <FIG>, it can be seen that the antenna device <NUM> has lower VSWR in a low-band of LTE than the antenna device <NUM> of the sixth embodiment, and has less variation in VSWR in a high-band.

An eighth embodiment of the antenna device according to the present invention is explained with reference to <FIG>. <FIG> is a plan view for illustrating the body portion of the antenna device of <FIG> when viewed from below (direction in which the groundplate <NUM> is mounted). For convenience, the ground plate <NUM> is omitted. The antenna device <NUM> of this embodiment is different from the seventh embodiment in that both a high-band portion <NUM> and a low-band portion <NUM> of an antenna element <NUM> include elements having a meander shape. A feeding end <NUM> is shared by the respective high-band portion <NUM> and the low-band portion <NUM>.

The low-band portion <NUM> has a plate-shaped element at a proximal end having a relatively larger area than a remaining element toward a distal end, and the element extending from the proximal end to the distal end has a meander shape. In this case, a first turn of the meander shape starts at a portion far away from the feeding end <NUM> and the GND conductive pattern <NUM>. Further, in the element on a way to the distal end, in a section not having the high-band portion <NUM> near the turns, the turns extend long downward (downward direction of <FIG>) than a portion parallel to the turns of the high-band portion <NUM>. Therefore, a length from the proximal end to the distal end of the low-band portion <NUM> (right and left directions in <FIG>) can be shortened.

Further, the turn portions at the distal end and in the vicinity of the distal end of the low-band portion <NUM> do not exceed a width of the element of the high-band portion <NUM> (width in up and down directions of <FIG>). That is, a distance between each turn portion or the distal end of the element having a meander shape and the GND conductive pattern <NUM> is always longer than that of the high-band portion <NUM>. Therefore, in a low-band of LTE, narrowing a band can be restrained in a frequency range in which VSWR is reduced to a practical level.

<FIG> is a VSWR characteristic graph. The vertical axis represents VSWR and the horizontal axis represents a frequency (MHz). In <FIG>, a broken line is a VSWR characteristic example of the antenna device <NUM> of the seventh embodiment, and a solid line is a VSWR characteristic example of the antenna device <NUM> of this embodiment. As illustrated in <FIG>, in case of the eighth embodiment, it can be seen that VSWR in the low-band of LTE becomes lower than that of the antenna device <NUM> as a whole, and a phenomenon in which VSWR rapidly changes in the high-band of LTE can be alleviated.

The meander-shaped conductive patterns having a meander shape of the high-band portion <NUM> and the low-band portion <NUM> are not limited to the example described in this embodiment, and can be optionally changed as long as the antenna device resonates in a frequency band of LTE. For example, conductive patterns of an antenna device <NUM>' illustrated in <FIG> may be used. In the example shown in <FIG>, a length from a proximal end to a distal end of a high-band portion <NUM> is formed to be shorter than that illustrated in <FIG>, and the distal end is formed to be lower than a height of the proximal end (up and down directions of <FIG>). Further, the low-band portion <NUM> has a proximal end having a larger area than that of the example illustrated in <FIG>. The number of turns having a meander shape is fewer than that of the example illustrated in <FIG> by that size. The low-band portion <NUM> has a first turn of the element extending from the proximal end to the distal end. The first turn starts at a portion closest to a feeding end <NUM> and the GND conductive pattern <NUM>. The feeding end <NUM> is shared by the respective high-band portion <NUM> and the low-band portion <NUM>.

<FIG> is a VSWR characteristic graph for this case. In <FIG>, a broken line is a VSWR characteristic example of the antenna device <NUM> including the antenna element <NUM> illustrated in <FIG>, and a solid line is a VSWR characteristic example of the antenna device <NUM>' including an antenna element <NUM> illustrated in <FIG>. As illustrated in <FIG>, it can be seen that, in case of the antenna device <NUM>', VSWR in a frequency band exceeding <NUM> in the low-band of LTE is lower, and a widening a band can be achieved.

In the examples of <FIG> and <FIG>, the positions of the turns near the distal ends of the low-band portions <NUM> and <NUM> do not exceed widths (up and down directions in the drawing) of the high-band portions <NUM> and <NUM>. However, when the positions exceed the widths of the high-band portions <NUM> and <NUM> to be close to the GND conductive pattern <NUM>, it is known that a range, in which VSWR in the low-band of LTE can be satisfactorily maintained, is sharply narrowed.

A ninth embodiment of the antenna device according to the present invention is explained with reference to <FIG> is a plan view of the body portion of the antenna device of <FIG> when viewed from below (direction in which the ground plate <NUM> is mounted), and <FIG> is a plan view of the body portion of the antenna device of <FIG> when viewed from above (rear side of <FIG>). An antenna device <NUM> of this embodiment is different from the eighth embodiment in the shape and the formed position of an antenna element <NUM>.

The antenna device <NUM> of this embodiment has the antenna element <NUM> which is formed on a non-conductive surface in a front surface of the approximately trapezoidal region <NUM> in the substrate <NUM>, and which is electrically connected (conductive) via a through hole to the feeding conductive pattern <NUM> formed on a rear surface of the region <NUM>. A high-band portion <NUM> is formed along an outer edge shape of the GND conductive pattern <NUM> having a constant distance from the outer edge. That is, in a section in which the outer edge of the GND conductive pattern <NUM> is protruded in a direction of the antenna element <NUM>, an element extending from a proximal end of the high-band portion <NUM> is straight, and, in a section in which the outer edge of the GND conductive pattern <NUM> is away from the antenna element <NUM>, the element has a meander shape and a distal end has the same height as the proximal end (up and down directions in <FIG>). For that reason, as compared with the high-band portions <NUM>, <NUM>, and <NUM> as illustrated in <FIG>, <FIG>, and <FIG>, the high-band portion <NUM> is less susceptible to an influence by the GND conductive patterns <NUM> and <NUM>, and the ground plate <NUM>, thereby VSWR in the high-band of LTE is lowered. Further, in addition to alleviation of variation in VSWR, there is an effect of improvement in an average gain of a horizontally polarized wave.

Meanwhile, the low-band portion <NUM> has a plate-shaped portion at the proximal end having a relatively larger area than a remaining element toward the distal end. Further, in the element in middle up to the distal end, in a section not having the high-band portion <NUM> near portions of the turns having a meander shape, a turn length (length extending downward of <FIG>) becomes longer than a section in which the turns are parallel to the turns of the high-band portion <NUM>. Therefore, a length extending from the proximal end of the low-band portion <NUM> (right and left directions in <FIG>) can be shortened. Still further, any turn portion of the low-band portion <NUM> is not configured to extend toward the GND conductive pattern <NUM> compared to an element farthest away from the GND conductive pattern <NUM> in the high-band portion <NUM>. For that reason, the low-band portion <NUM> is less susceptible to an influence by the GND conductive patterns <NUM> and <NUM>, and the ground plate <NUM>, thereby VSWR in the low-band of LTE is lowered. Further, in addition to alleviation of variation in VSWR, there is an effect of improvement in the average gain of a horizontally polarized wave.

A feeding end <NUM> is shared by the respective high-band portion <NUM> and the low-band portion <NUM>.

The non-conductive surface of the substrate <NUM> is transmittable by radio waves, so that radio waves can be transmitted or received on the front surface (surface on which the patch antenna <NUM> is provided) of the substrate <NUM> on which the antenna element <NUM> is formed. Then, an average gain in the low-band and the high-band of the LTE is increased.

<FIG> and <FIG> are graphs showing average gain characteristics when the ground plate <NUM>, the antenna element <NUM>, the substrate <NUM>, and the GND conductive patterns <NUM> and <NUM> of the antenna device <NUM> of the embodiment are arranged parallel to the ground, and an operation is simulated. In this case, a radio wave to be transmitted or received by the antenna element <NUM> is a horizontally polarized wave. <FIG> is the graph showing the average gain characteristic example of the horizontally polarized wave in the horizontal plane in the low-band of LTE, and <FIG> is the graph showing the average gain characteristic example of the horizontally polarized wave in the horizontal plane in the high-band of LTE. In these drawings, the vertical axis represents average gain of the horizontally polarized wave (dBi), and the horizontal axis represents a frequency (MHz). Further, a broken line represents an average gain characteristic example when the antenna element <NUM> is formed on the rear surface of the substrate <NUM>, that is, in the region <NUM> illustrated in <FIG>, and a solid line represents an average gain characteristic example in the antenna device <NUM> according to this embodiment.

As in this embodiment, it can be seen that, when the antenna element <NUM> is formed on the front surface of the substrate <NUM>, the average gain becomes higher in most frequency bands.

Claim 1:
An antenna device configured to be mounted on a vehicle, comprising:
a ground conductor (<NUM>) having a planar shape; and
an antenna element (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) which is a resonant type, is provided at a position so as not to overlap with the ground conductor (<NUM>) within a plane substantially parallel to the ground conductor (<NUM>), and is configured to transmit or receive a polarized wave parallel to the ground conductor (<NUM>),
wherein the antenna element (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) includes a low-band portion (30a, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) for Long Term Evolution, LTE, low-band operation and a high-band portion (30b, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) for Long Term Evolution, LTE, high-band operation,
the low-band portion (30a, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is arranged at a position farther from a surface portion which is electrically connected to the ground conductor (<NUM>) than the high-band portion (30b, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>),
wherein each of the high-band portion (<NUM>, <NUM>, <NUM>) and the low-band portion (<NUM>, <NUM>, <NUM>) has at least a portion having a meander shape, and is configured to share a feeding end (<NUM>, <NUM>, <NUM>),
wherein distal end portions of the low-band portion (30a, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) and the high-band portion (30b, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) are arranged substantially parallel to each other from the feeding end (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>),
wherein an element having a meander shape of the low-band portion (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is configured to start turning from a closest portion with respect to the high-band portion (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>).