Patent Description:
In a conventional patch antenna, since a patch element as a radiation electrode is planar, a directivity in a direction perpendicular to the patch element is high, that is, a half-value angle (range of a directivity angle from a gain peak to -<NUM> dB) is narrow.

The document XP032968452 discloses a patch antenna according to the preamble of claim <NUM>.

As described above, the conventional patch antenna has the narrow half-value angle, in other words, a gain on a lateral side of a patch antenna in a direction parallel to the patch element is low. Therefore, the conventional patch antenna is not suitable for use in transmitting and receiving a radio wave in a wide angle range.

The present invention has been made in view of circumstances, and an object of the present invention to provide a patch antenna and an antenna device that can transmit and/or receive a radio wave in a wide angle range by forming a patch element into a curved surface or a bent surface to widen a half-power angle in directional characteristics.

The present invention concerns a patch antenna according to claim <NUM>. Further aspects of the present invention are defined in the dependent claims. The patch antenna includes a patch element, and a ground conductor facing the patch element, in which the patch element is convex toward a side opposite to a side facing the ground conductor.

It is preferable that the patch antenna is convex while centering around at least one center line, end portions on both sides of the patch element are positioned across the center line to face each other, and surfaces parallel to a direction toward the ground conductor from the respective end portions on the both sides at the shortest distance intersect or become a same surface.

It is preferable that the patch element has a plate shape that is curved and bent at a central portion.

It is preferable that a power is fed at one end portion side of the patch element in a direction of the center line.

It is preferable that wave sources are positioned at both end portions of the patch element in the direction of the center line.

It is preferable that the patch element has an outer surface on a side opposite to a side facing the ground conductor, one end portion of the outer surface is directed to a first direction, and the other end portion is directed to a second direction opposite to the first direction.

It is preferable that the patch element has a ridge line.

It is preferable that a dielectric body is provided between the patch element and the ground conductor.

It is preferable that an inner conductor of a coaxial cable is connected to the patch element, and an outer conductor of the coaxial cable is connected to the ground conductor.

Another aspect of the present invention is an antenna device. The antenna device includes said patch antenna.

It is preferable that the patch antenna is supported by a vehicle body so as to be used for vertically polarized waves.

Any combinations of the above constituent elements, and expressions of the present invention that are converted in methods and systems are also effective as aspects of the present invention.

According to the present invention, since the patch antenna includes the patch element having the curved surface or the bent surface shape, a half-value angle in directional characteristics can be widened, so that a radio wave can be transmitted and/or received in a wide angle range.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, processes, or the like illustrated in the drawings are denoted by the same reference numerals, and a repetitive description thereof will be omitted. In addition, the embodiments are not intended to limit the invention but are examples, and all the features and combinations thereof described in the embodiments are not necessarily essential to the invention.

<FIG> show a first embodiment of a patch antenna and an antenna device according to the present invention, <FIG> is a front view of a patch antenna portion, <FIG> is a side view showing the patch antenna portion, <FIG> is a back view showing the patch antenna portoin, and <FIG> is a plan view showing the patch antenna portion. <FIG> is a side sectional view showing an overall configuration of the antenna device including the patch antenna.

First, a patch antenna <NUM> will be described with reference to <FIG>. Here, the patch antenna <NUM> is used for, for example, V2X (Vehicle to Everything: Vehicle and Vehicle, Road and Vechile) communication. The patch antenna <NUM> is arranged vertically (that is, a vertical direction) with respect to a horizontal plane (a plane perpendicular to a direction of gravity) and is used for vertically polarized waves. The patch antenna <NUM> includes a patch element <NUM> being a radiation electrode, a ground conductor plate <NUM> facing the patch element <NUM>, a dielectric body <NUM> interposed between the patch element <NUM> and the ground conductor plate <NUM>, and a coaxial cable <NUM> as a power feeding line.

The patch element <NUM> is formed by bending a planar metal plate conductor into a bent surface shape (here, including a shape by bending a plane such that one or a plurality of ridge lines are formed) convex toward a side opposite to a side facing the ground conductor plate <NUM>. The patch element <NUM> is convex while centering around at least one center line. Further, end portions on both sides of the patch element <NUM> are positioned across the center line, and surfaces parallel to a direction toward the ground conductor plate <NUM> from the end portions on the both sides at the shortest distance intersect or become the same surface. That is, the patch element <NUM> has a plate shape that is curved and bent at a central portion. Specifically, the patch element <NUM> is formed by bending the sheet metal conductor so as to have four ridge lines, and an outer surface <NUM> (a surface on an opposite side to a surface on the side facing the ground conductor plate <NUM>) that does not face the ground conductor plate <NUM> has five rectangular planes partitioned by the four ridge lines in an upper-lower direction (parallel to the center line). That is, the outer surface <NUM> of the patch element <NUM> has a front surface portion <NUM>, first side surface portions 13A, 13B that are bent from the front surface portion <NUM>, and second side surface portions 14A, 14B that are bent from the first side surface portions 13A, 13B so as to be perpendicular to the front surface portion <NUM>. At this time, the center line is parallel to two ridge lines sandwiching the front surface portion <NUM>, and is positioned in the middle of the two ridge lines. When the patch element <NUM> is viewed from the front, the first side surface portion 13A and the second side surface portion 14A are directed leftward, and the first side surface portion 13B and the second side surface portion 14B are directed rightward. As a result, the patch element <NUM> has a predetermined length L in a front-rear direction (a direction orthogonal to the front surface portion) (<FIG>).

The ground conductor plate <NUM> is formed by bending a planar metal plate conductor so as to have four ridge lines similarly to the patch element <NUM>, and has portions respectively parallel to the front surface portion <NUM>, the first side surface portions 13A, 13B, and the second side surface portions 14A, 14B. Further, in the ground conductor plate <NUM>, a hole <NUM> is provided in a region including an position facing a center of an upper side of the front surface portion <NUM> of the patch element <NUM> and a periphery thereof.

The dielectric body <NUM> is, for example, an ABS resin and is sandwiched between the patch element <NUM> and the ground conductor plate <NUM>. The dielectric body <NUM> is molded in advance in accordance with a bent shape of the patch element <NUM>. The patch element <NUM> and the ground conductor plate <NUM> are integrated by the dielectric body <NUM> interposed therebetween, and the patch element <NUM> is held by the ground conductor plate <NUM> via the dielectric body <NUM>.

A power feeding conductor <NUM>, that is a thin sheet strip-shaped conductor (may be pin-shaped), penetrates the hole <NUM> in a non-contact manner and connects an inner conductor <NUM> of the coaxial cable <NUM> and the patch element <NUM>. For example, the power feeding conductor <NUM> may be formed by bending a strip-shaped conductor portion integral with the patch element <NUM>. An outer conductor <NUM> of the coaxial cable <NUM> is sandwiched by a pair of clamping pieces <NUM> provided on the ground conductor plate <NUM>, and is connected to the ground conductor plate <NUM>.

In the patch antenna <NUM>, the power feeding conductor <NUM> is connected to the patch element <NUM> at an end surface of the patch element <NUM> for impedance matching with characteristic impedance of the coaxial cable <NUM> (a power feeding point <NUM> is positioned at a height of the end surface of the patch element <NUM>). The power feeding conductor <NUM> may be connected to the patch element <NUM> at a position (for example, a position below the end surface) other than the end surface of the patch element <NUM> as long as the impedance matching with the characteristic impedance of the coaxial cable <NUM> can be performed. In addition, in the patch antenna <NUM>, the power feeding conductor <NUM> is connected to the patch element <NUM> at a central position of the patch element <NUM> when the patch element <NUM> is viewed in a horizontal plane (the power feeding point <NUM> is positioned at the central position of the patch element <NUM> when the patch element <NUM> is viewed in the horizontal plane). This is because, when the power geed point <NUM> is shifted from the central position of the patch element <NUM> with viewing the patch element <NUM> in the horizontal plane, distances from the power feeding point <NUM> to left and right ends of the patch element <NUM> are different on the left and right, and unnecessary resonance may occur in the patch antenna <NUM>. As shown in <FIG>, in a case where the patch element <NUM> is power-fed at one end portion side of the patch element <NUM> in a direction of the center line, wave sources are positioned at both end portions of the patch element <NUM> in the direction of the center line. That is, in the patch antenna <NUM> of <FIG>, since the power is fed from an upper side of the patch element <NUM> in the upper-lower direction, the wave sources are generated at an upper end portion and a lower end portion of the patch element <NUM> in the upper-lower direction. Even when the power is fed from a lower side of the patch element <NUM> in the upper-lower direction, the wave sources are generated at the upper end portion and the lower end portion of the patch element <NUM> in the upper-lower direction.

The patch antenna <NUM> does not have a short-circuit conductor such as an inverted F-shaped antenna.

<FIG> is an antenna device <NUM> for a vehicle including the patch antenna <NUM>. An SXM antenna <NUM> for satellite digital radio broadcast reception, GNSS (Global Navigation Satellite System) antenna <NUM>, an AM/FM broadcast receiving antenna <NUM>, and the patch antenna <NUM> for V2X communication are mounted on an antenna base <NUM> mounted on a vehicle body roof from the front in this order, and a radio wave transmitting antenna case <NUM> is placed on the antenna base <NUM> so as to cover these antennas. In <FIG>, an upper-lower direction, and a front-rear direction of the antenna device <NUM> for a vehicle are defined. Upper, lower, left and right directions in a paper surface respectively indicate upper, lower, front and rear directions of the antenna device <NUM>.

The SXM antenna <NUM> and the GNSS antenna <NUM> are patch antennas configuring a planar antenna and have a directivity upward. The AM/FM broadcast receiving antenna <NUM> has a series connection between a capacitance loading element <NUM> being a conductive plate and a coil <NUM>. The capacitance loading element <NUM> has, for example, a meandering shape. In addition, the coil <NUM> may be disposed substantially at a center of the antenna device <NUM> for a vehicle or may be offset therefrom. The patch antenna <NUM> for the V2X communication is arranged so as to erect vertically on the antenna base <NUM> by fixing the ground conductor plate <NUM> to the antenna base <NUM>, and is arranged such that the front surface portion <NUM> of the patch element <NUM> is directed rearward. In addition, in a state in which the antenna device <NUM> for a vehicle is attached on the vehicle body roof, the patch element <NUM> of the patch antenna <NUM> forms a substantially vertical plane and is supported by the vehicle body, and the patch antenna <NUM> is used for the vertically polarized waves.

<FIG> is a directional characteristic diagram obtained by simulation showing a horizontal plane gain (solid line) of the patch antenna <NUM> according to the first embodiment in comparison with a horizontal plane gain (dotted line) according to a comparative example (described later in <FIG>), in which frequency: <NUM>, main lobe gain: <NUM> dB, main lobe azimuth: <NUM>°, and half-value angle (angle range from a gain peak to -<NUM> dB): <NUM>°. In the case of <FIG>, an azimuth angle <NUM>° in <FIG> is backward, and the half-value angle of the patch antenna <NUM> according to the first embodiment can be ensured to be <NUM>° or more as compared with the narrow half-value angle in the comparative example of <FIG>. The reason why the half-value angle is increased is that the patch element <NUM> is bent to form a curved surface convex toward the outer surface thereof, and the patch element <NUM> has the predetermined length L in the front-rear direction. <FIG> shows a simulation result in a case where the patch antenna <NUM> is present alone, but it is considered that an influence on horizontal plane directional characteristics can be ignored even if the capacitance loading element <NUM> extends above the patch antenna <NUM> as shown in <FIG>.

<FIG> is a VSWR characteristic diagram obtained by simulation of the patch antenna <NUM>. As shown in <FIG>, the VSWR is not low other than the frequency of <NUM>, and unnecessary resonance does not occur in the patch antenna <NUM> in the vicinity of <NUM>.

According to the present embodiment, the following effects can be achieved.

The reason why the patch element of the patch antenna is a curved surface or a bent surface will be described below with reference to <FIG>.

<FIG> is an explanatory diagram obtained by simulation showing a relationship between the length of the patch element in the front-rear direction and the half-value angle of the patch antenna. <FIG> is a horizontal sectional view of a patch antenna <NUM> (normal patch antenna) according to the comparative example when the length in a front-rear direction of the patch element used in the simulation of <FIG> is <NUM>, <FIG> is a horizontal sectional view of a patch antenna <NUM> according to a second embodiment of the present invention used in the simulation of <FIG> when a length L of the patch element in a front-rear direction is <NUM>, and <FIG> is a horizontal sectional view of a patch antenna <NUM> according to a third embodiment of the present invention used in the simulation of <FIG> when a length L of the patch element in a front-rear direction is <NUM>. In the simulation of <FIG>, the half-value angle is obtained assuming that an operation frequency of the patch antenna of <FIG> is <NUM>. In addition, in a case where λ<NUM> is a wavelength in a free space, the length L of the patch element in the front-rear direction of <NUM> corresponds to <NUM>λ<NUM>, and the length L of the patch element in the front-rear direction of <NUM> corresponds to <NUM>λ<NUM>.

In the patch antenna <NUM> according to the comparative example of <FIG>, a patch element <NUM> and a ground conductor plate <NUM> are both flat plates and are arranged in parallel. A length L of the patch element <NUM> in a front-rear direction is <NUM>, and it can be seen from <FIG> that the half-value angle is the smallest.

In the patch antenna <NUM> according to the second embodiment shown in <FIG>, a patch element <NUM> has a plate shape that is curved and bent at a central portion, and a ground conductor plate <NUM> is bent at a center portion and is arranged parallel to the patch element <NUM>. A length L of the patch element <NUM> in a front-rear direction is <NUM>. Since the patch element <NUM> has a length component in the front-rear direction, as can be seen from <FIG>, the half-value angle is wider than that in the comparative example of <FIG>.

In the patch antenna <NUM> according to the third embodiment shown in <FIG>, a patch element <NUM> has a plate shape that is curved and bent in a substantially semicircular arc shape at a central portion, and one end portion of an outer surface of the patch element <NUM> is directed leftward and the other end portion thereof is directed rightward. A length L of the patch element <NUM> in a front-rear direction is <NUM>. A ground conductor plate <NUM> is a flat plate and is arranged parallel to a main part of the patch element <NUM>. In this case, as shown in <FIG>, the half-value angle is further widened to <NUM>°. The first embodiment described above has a structure corresponding to a case that the length L in the front-rear direction of the patch element shown in the third embodiment is <NUM>. In the simulation of <FIG>, the lengths (creepage distance) in a horizontal cross section of the patch element shown in <FIG> are all equal. In addition, the simulation shown in <FIG> is performed assuming that there is no coaxial cable in <FIG>.

As shown in <FIG>, when the length L of the patch antenna in the front-rear direction is increased by making patch element curved, the half-value angle increases. As shown in the patch antenna <NUM> in <FIG>, when the one end portion of the patch element <NUM> is directed leftward and the other end portion thereof is directed rightward, the half-value angle becomes <NUM>°. That is, in order to increase the half-value angle, it is effective that the length L in the front-rear direction is increased by making the patch element curved, that is, the patch element is directed to not only the front (directed rearward of a vehicle in an arrangement of the antenna device <NUM> in <FIG>) but also the left and right, and the half-value angle of <NUM>° can be realized by setting the length L of the patch element in the front-rear direction to an appropriate value.

Further, the patch element may be directed only to the front and left or only to the front and right (the horizontal cross section of the patch element has an L shape). Since the patch antenna has a high directivity in a direction perpendicular to the patch element, in this case, the half-value angle is larger than that of the planar patch element of the normal patch antenna. However, the half-value angle of the patch antenna is smaller than that of the patch antenna <NUM> according to the first embodiment and the patch antenna <NUM> according to the third embodiment in which the patch elements are directed not only to the front but also to the left and right.

In a case of the patch antenna designed for the V2X communication, a resonance mode of the patch antenna includes a dominant mode that resonates at the frequency of <NUM> for the V2X communication and a second mode that resonates at a frequency other than the frequency of <NUM>.

<FIG> is a VSWR characteristic diagram obtained by simulation of the patch antenna when the lengths L of the patch element in the front-rear direction are <NUM> and <NUM>. In the simulation when the length L of the patch element in the front-rear direction in <FIG> is <NUM>, the patch antenna <NUM> according to the third embodiment shown in <FIG> was used. In addition, in the simulation when the length L of the patch element in the front-rear direction in <FIG> is <NUM>, a patch antenna <NUM> according to a fourth embodiment shown in <FIG> to be described later was used. In the case where λ<NUM> is the wavelength in the free space, the length L of the patch element in the front-rear direction of <NUM> corresponds to <NUM>λ<NUM>, and the length L of the patch element in the front-rear direction of <NUM> corresponds to <NUM>λ<NUM>.

<FIG> is a horizontal sectional view of the patch antenna <NUM> according to the fourth embodiment used in the simulation when the length L of the patch element in the front-rear direction in <FIG> is <NUM>. In the patch antenna <NUM> according to the fourth embodiment shown in <FIG>, a patch element <NUM> has a plate shape that is curved and bent in a substantially semicircular arc shape at a central portion, and one end portion of an outer surface of the patch element <NUM> is directed leftward and the other end portion thereof is directed rightward. A length L of the patch element <NUM> in a front-rear direction is <NUM>. A ground conductor plate <NUM> is a flat plate and is arranged parallel to a main part of the patch element <NUM>.

In the fourth embodiment, a radius of curvature of the patch element <NUM> is the same as that of the patch element <NUM> in the third embodiment shown in <FIG>. However, in order to make the length L of the patch element <NUM> in the front-rear direction larger than that of the patch element <NUM> in <FIG>, the length of the patch antenna <NUM> in the horizontal cross section (in other words, a creepage distance of the patch element <NUM>) is longer than the length of the patch antenna <NUM> (the creepage distance of the patch element <NUM>) in <FIG>. Therefore, as shown in <FIG>, when the length L of the patch element in the front-rear direction is <NUM> (in the case of solid line), the VSWR is not low other than the frequency of <NUM>, and the dominant mode is dominant, so that the unnecessary resonance (resonance by the second mode) does not occur in the vicinity of the dominant mode. On the other hand, when the length L of the patch element in the front-rear direction is <NUM> (in the case of dotted line), an influence of the second mode is strong, and characteristics of the dominant mode are deteriorated, so that the unnecessary resonance can be confirmed.

As can be seen from results of <FIG>, in order to suppress the occurrence of the unnecessary resonance, the length L of the patch element in the front-rear direction is shortened (not longer than necessary), that is, the length of the patch antenna in the horizontal cross section may be shortened (so as not to be longer than necessary).

The simulation of <FIG> is performed assuming that there is no coaxial cable in the comparative example of <FIG>, the second embodiment of <FIG>, and the third embodiment of <FIG>, but the patch antenna needs to be electrically connected to the coaxial cable for feeding. <FIG> is a plan view of a patch antenna <NUM> having a structure suitable for feeding by the coaxial cable <NUM> as viewed from above, according to a fifth embodiment. In this case, the patch antenna <NUM> includes a patch element <NUM>, a ground conductor plate <NUM> facing the patch element <NUM>, a dielectric body <NUM> interposed between the patch element <NUM> and the ground conductor plate <NUM>, and the coaxial cable <NUM> as a power feeding line.

The patch element <NUM> according to the fifth embodiment has a bent surface shape formed by bending a planar metal plate conductor so as to have two ridge lines, and an outer surface <NUM> has three rectangular planes partitioned by the two ridge lines in the upper-lower direction. That is, the outer surface <NUM> of the patch element <NUM> has a front surface portion <NUM>, and side surface portions 135A, 135B that are bent perpendicularly to the front surface portion <NUM>, respectively. When the patch element <NUM> is viewed from the front, the side surface portion 135A is directed leftward and the side surface portion 135B is directed rightward. The ground conductor plate <NUM> is formed by bending a planar metal plate conductor so as to have two ridge lines similarly to the patch element <NUM>, and has portions respectively parallel to the front surface portion <NUM> and the side surface portions 135A, 135B. A length L of the patch element <NUM> in a front-rear direction is set to the same length as that in the first embodiment. Other configurations are similar to those in the first embodiment.

<FIG> is a directional characteristic diagram obtained by simulation showing a horizontal plane gain (solid line) of the patch antenna <NUM> according to the fifth embodiment in comparison with the horizontal plane gain (dotted line) according to the comparative example (<FIG>). At a frequency of <NUM>, the half-value angle (angle range from a gain peak to -<NUM> dB) can be ensured to be <NUM>° or more.

<FIG> is a VSWR characteristic diagram obtained by simulation of the patch antenna <NUM> adapted to the coaxial cable according to the fifth embodiment. In the patch antenna <NUM> according to the fifth embodiment of <FIG>, since the patch element <NUM> has a curved surface shape having the two ridge lines, one end portion of the patch element <NUM> is directed leftward and the other end portion is directed rightward, so that the half-value angle is <NUM>° or more. However, as shown in <FIG>, the unnecessary resonance can be confirmed in the patch antenna <NUM> of <FIG>. This is because a creepage distance of the patch element <NUM> is longer than the creepage distance of the patch element <NUM> according to the first embodiment when the length L of the patch element <NUM> in the front-rear direction is set to the same value as in the first embodiment.

That is, in order to shorten the length of the patch antenna in the horizontal cross section while maintaining that the patch element is directed not only to the front but also to the left and right and the half-value angle is <NUM>°, the patch element <NUM> of the patch antenna <NUM> in the first embodiment is formed into a bent surface shape having the four ridge lines, and is provided with the first side surface portions 13A, 13B between the second side surface portions 14A, 14B orthogonal to the front surface portion <NUM> and the front surface portion <NUM> (close to a circular arc-shaped curved surface).

<FIG> and <FIG> show the patch antenna and the antenna device according to a sixth embodiment of the present invention, in which an antenna device <NUM> is arranged inside a windshield <NUM> of the vehicle body having the windshield <NUM>, a roof <NUM>, a hood <NUM>, or the like. In the antenna device <NUM>, the patch antenna <NUM> as like in the first embodiment is accommodated in an antenna case <NUM> that is a combined structure of a front case portion (radio wave transmitting radome) <NUM> and a rear case portion <NUM>. In this case, the patch antenna <NUM> is arranged such that the front surface portion <NUM> of the patch element <NUM> is directed to the front of the vehicle body, and the patch element <NUM> is held by the front case portion <NUM> via an attachment member <NUM>, and the ground conductor plate <NUM> is held parallel to the patch element <NUM> at a predetermined interval (the ground conductor plate <NUM> may not be attached to the antenna case <NUM>). Further, in this case, the patch element <NUM> of the patch antenna <NUM> forms a substantially vertical plane and is supported by the vehicle body, and the patch antenna <NUM> is used for the vertically polarized waves. The coaxial cable <NUM> that feeds the power to the patch antenna <NUM> is drawn out from the antenna case <NUM> along the inside of the windshield <NUM> and the roof <NUM>.

In the sixth embodiment, the half-value angle of <NUM>° or more including the front of the vehicle body can be ensured. Other operations and effects are similar to those of the first embodiment described above.

Although the present invention has been described above by taking the embodiments as an example, it will be understood by those skilled in the art that various modifications can be made to each component and each processing process of the embodiments within the scope of the appended claims. Hereinafter, a modification will be described.

In each embodiment, a space by omitting the dielectric body may be used as long as the patch element and the ground conductor plate can be held at the predetermined interval.

In addition, as long as the outer surface of the patch element is a curved surface shape convex toward the outside, the number of ridge lines may be any number, and the outer surface of the patch element may be a combination of a curved surface having no ridge line and a flat surface.

Claim 1:
A patch antenna (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) comprising:
a patch element (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>); and
a ground conductor (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) facing the patch element (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>), wherein
the patch element (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is convex toward a side opposite to a side facing the ground conductor (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) while centering around a center line,
characterized in that
wave sources are positioned at both end portions of the patch element (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) in the direction of the center line.