Antenna and window glass for vehicle

An antenna includes a flat conductor, and the flat conductor includes a first slot extending in a first direction, a second slot connected to the first slot and extending in a second direction, a third slot connected to the first slot and including another end that is open through an outer edge of the conductor, the third slot extending to one side of the first slot opposite from the second slot, and a fourth slot connected to the second slot, the fourth slot extending to one side of the second slot opposite from the first slot, wherein the third slot has a wide portion, and the fourth slot has a wide portion, and the outer edge includes an inclined portion inclined with respect to a virtual line that passes through the another end of the third slot and that is perpendicular to a direction in which the third slot extends.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an antenna and a window glass for a vehicle.

2. Description of the Related Art

A high-speed communication system such as a telematics service, in which information is transmitted and received between a communication device on a vehicle and a device at the outside of the vehicle, uses an antenna that can attain impedance matching over a relatively wide frequency range. As an antenna supporting such a wide band, an antenna famed with a conductive film is known (for example, see PTL 1).

PRIOR ART DOCUMENT

Patent Literature

SUMMARY OF THE INVENTION

Technical Problem

However, an antenna formed with a flat conductor such as a conductive film is desired to not only support a wide frequency range but also further improve an antenna gain.

Accordingly, in the present disclosure, an antenna supporting a wide frequency range and improving an antenna gain and a window glass for a vehicle provided with the antenna are provided.

Solution to Problem

According to an aspect of the present invention, provided is an antenna including a flat conductor, the flat conductor including a first feeding point and a second feeding point located away from each other, a first slot extending in a first direction between the first feeding point and the second feeding point, a second slot including one end connected to one end of the first slot, the second slot extending in a second direction different from the first direction, a third slot including one end connected to another end of the first slot and another end that is open through an outer edge of the conductor, the third slot extending to one side of the first slot opposite from the second slot, and a fourth slot including one end connected to another end of the second slot, the fourth slot extending to one side of the second slot opposite from the first slot, wherein the third slot has a portion of which slot width is wider than the first slot, the fourth slot has a portion of which slot width is wider than the second slot, and the outer edge includes an inclined portion inclined with respect to a virtual line that passes through the another end of the third slot and that is perpendicular to a direction in which the third slot extends.

Effect of Invention

According to an aspect of the present disclosure, an antenna supporting a wide frequency range with an improved antenna gain and a window glass for a vehicle provided with the antenna can be provided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment for carrying out the present invention will be described with reference to the drawings. In each embodiment, deviations from directions such as parallel direction, perpendicular direction, orthogonal direction, horizontal direction, vertical direction, height direction, widthwise direction and the like are tolerated to such an extent that the effects of the present invention are not impaired. Further, the shape at a corner portion of an antenna element is not limited to a right angle, and may be rounded in a shape of a bow. Each top view illustrates a glass plate (hereinafter also referred to as “window glass”) for a window of a vehicle as seen from a vehicle-inner side (a viewpoint from the inside of the vehicle) by facing a glass surface of the glass plate, when the window glass is attached to the vehicle. In a case where the window glass is a windshield attached to a front portion of the vehicle or rear glass attached to a rear portion of the vehicle, a height direction in each top view corresponds to a height direction of the vehicle, and a widthwise direction in each top view corresponds to a widthwise direction of the vehicle. Further, the window glass is not limited to a windshield or a rear glass, and may be, for example, a side glass attached to a side portion of the vehicle. In each top view, the direction parallel to an X axis (X axis direction), the direction parallel to a Y axis (Y axis direction), and the direction parallel to a Z axis (Z axis direction) represent a widthwise direction of the glass plate, a height direction of the glass plate, and a direction perpendicular to the face of the glass plate (also referred to as a normal direction), respectively. The X axis direction, the Y axis direction, and the Z axis direction are orthogonal to each other.

FIG. 1is a plan view illustrating an example of a configuration of a window glass for a vehicle from a viewpoint at a vehicle-inner side. The window glass100for the vehicle as illustrated inFIG. 1is an example of a rear glass attached to the rear portion of a vehicle. The window glass100for a vehicle includes a glass plate60for a window of a vehicle, a defogger40disposed in the glass plate60, a right rear antenna1disposed in a right-hand lower side area of the glass plate60, and a left rear antenna2disposed in a left-hand lower side area of the glass plate60. In addition, an antenna (not illustrated), which is at least one of AM radio, FM radio, DAB (Digital Audio Broadcast), television broadcast, and remote keyless entry antennas, may be provided between the defogger40and an upper edge60aof the glass plate60.

The glass plate60is an example of a glass plate for a window of a vehicle. An outer shape of the glass plate60is substantially in a quadrilateral shape. The upper edge60arepresents a glass edge at an upper side of the glass plate60. A lower edge60crepresents a glass edge at a lower side of the glass plate60(i.e., a side opposite to the upper edge60a). A right edge60brepresents a glass edge at a right-hand side of the glass plate60. A left edge60drepresents a glass edge at a left-hand side of the glass plate60(i.e., a side opposite to the right edge60b). The right edge60bis a glass edge adjacent to the right-hand side portions of the upper edge60aand the lower edge60c. The left edge60dis a glass edge adjacent to left-hand side portions of the upper edge60aand the lower edge60c.

The glass plate60has a pair of side edges. The right edge60bis an example of a first side edge which is one of the pair of side edges. The left edge60dis an example of a second side edge which is the other of the pair of side edges. Although a connection portion between the upper edge60aand the right edge60bis connected with a curvature, the connection portion may be connected without a curvature. This is also applicable to the shapes of the connection portions between other edges.

The defogger40is an electrical heating type conductor pattern that defogs the glass plate60. The defogger40includes a plurality of heating wires extending in the widthwise direction of the glass plate60and a plurality of bus bars that feed power to the plurality of heating wires. In the present embodiment, a plurality of heating wires42extending in the widthwise direction of the glass plate60so as to run in parallel to each other, and a pair of bus bars41a,41bconnected to the plurality of heating wires42are provided on the glass plate60. When a voltage is applied between the pair of bus bars41a,41b, the plurality of heating wires42are energized to generate heat, which defogs the glass plate60.

The plurality of heating wires42are conductive patterns connected between the right bus bar41aand the left bus bar42b. The right bus bar41ais an example of a first bus bar, and is a conductive pattern extending in the height direction of the glass plate60along the right edge60b. The left bus bar41bis an example of a second bus bar, and is a conductive pattern extending in the height direction of the glass plate60along the left edge60d.

The window glass100for the vehicle is attached to a window frame70formed through a metal body of the vehicle. The window frame70includes frame edges (an upper frame edge71a, a right frame edge71b, a lower frame edge71c, and a left frame edge71d) for forming the window.

The right rear antenna1and the left rear antenna2are provided in a margin area at the lower side of the defogger40. In the present embodiment, the right rear antenna1and the left rear antenna2are provided in a margin area between lowermost heating wires42cof the plurality of heating wires42and the lower edge60cof the glass plate60. When the window glass100for the vehicle is attached to the window frame70, the right rear antenna1and the left rear antenna2are located in proximity to the lower frame edge71cof the window frame70. In the present embodiment, the right rear antenna1and the left rear antenna2are located between the lower frame edge71cand the lowermost heating wires42c.

Further, at least some of the functional units such as a bus bar, a heating wire, a feeding portion, and the antennas1,2may be arranged on a light shielding film65famed in a peripheral area of the glass plate60. A specific example of the light shielding film65includes ceramics such as a black ceramic film. When the window glass100for the vehicle is viewed from the outside of the vehicle, the portion overlapping the light shielding film65is not visible from the outside of the vehicle. This improves the design of the window glass100for the vehicle and improves the design of the vehicle.

In the present embodiment, the right rear antenna1and the left rear antenna2are arranged in a belt-like light shielding area between a light shielding film edge65cat a lower side of the light shielding film65and the lower edge60cof the glass plate60. Upper edges of the right rear antenna1and the left rear antenna2are formed along the light shielding film edge65cso that at least a part of the right rear antenna1and the left rear antenna2is not exposed from the light shielding film65. Therefore, the design of the window glass100for the vehicle and the design of the vehicle are improved.

FIG. 2is a drawing illustrating an example of a state in which a coaxial cable is connected to a pair of feeding points in the antenna according to the first embodiment.FIG. 2illustrates a state in which one end of a coaxial cable8cis indirectly connected by a connector8to a core-side feeding point7aand a ground-side feeding point7bof the antenna1. The core-side feeding point7ais an example of a first feeding point. The ground-side feeding point7bis an example of a second feeding point. The feeding portion includes a pair of feeding points. The other end of the coaxial cable8cis connected to, for example, a device having at least one of a transmission function and a reception function. The core-side feeding point7ais connected to a center conductor (core wire8ca) of the coaxial cable8cvia the connector8by solder and the like. The ground-side feeding point7bis connected to an outer conductor8cbof the coaxial cable8cvia the connector8by solder and the like. The core wire8caand the outer conductor8cbare insulated by an insulator8cc. It should be noted that the pair of feeding points may be directly connected to one end of a coaxial cable.

The antenna1is a slot antenna formed with a conductive film20. The antenna1functions as a slot antenna with a slot10(elongated cutout) formed in the conductive film20.

The conductive film20is an example of a film-shaped or plate-shaped flat conductor, and is a substantially rectangular film having conductivity. In the first embodiment, the conductive film20includes a lower-side outer edge91and an upper-side outer edge92, which are opposite to each other in the Y axis direction, and includes a left-side outer edge93and a right-side outer edge94, which are opposite to each other in the X axis direction perpendicular to the Y axis direction.

Here, four outer edges of the conductive film20are denoted as outer edges A, B, C, and D. An aspect in which the outer edge A and the outer edge B are opposite to each other in a first direction includes not only a case where each of the outer edge A and the outer edge B is perpendicular to the first direction, but also a case where at least one of the outer edge A and the outer edge B is inclined with respect to the first direction. An aspect in which the outer edge C and the outer edge D are opposite to each other in a second direction includes not only a case where each of the outer edge C and the outer edge D is perpendicular to the second direction, but also a case where at least one of the outer edge C and the outer edge D is inclined with respect to the second direction. The above features are also applicable to other embodiments.

In the first embodiment, the Y axis direction is an example of the first direction, and the X axis direction is an example of the second direction different from the first direction. The right-side outer edge94is an example of one outer edge. The upper-side outer edge92is an example of another outer edge. The lower-side outer edge91is an example of a third outer edge. The left-side outer edge93is an example of a fourth outer edge.

The conductive film20includes a core-side conductor21extending to one side of the slot10and a ground-side conductor22extending to another side of the slot10. The core-side conductor21includes a core-side feeding point7a. The ground-side conductor22includes a ground-side feeding point7b. In the present embodiment, the core-side conductor21and the ground-side conductor22are separated by the slot10. While the window glass100for the vehicle is attached to the window frame70, the ground-side conductor22comes into proximity with the lower frame edge71cof the window frame70, and the core-side conductor21is located farther from the lower frame edge71cthan the ground-side conductor22.

At least one of the core-side conductor21and the ground-side conductor22may have a perforated portion (a hole-formed portion) in which holes are formed in the conductive film20. In an aspect in which the conductive film20is formed on the glass plate60by printing, embedding, pasting, and the like, when a metal area of the conductive film20is too large, the formability of glass may be reduced due to a difference in heat absorption between glass and metal. By forming the hole-formed portion, the area of the conductive film20can be increased while ensuring the formability of the glass. As the area of the conductive film20increases, the degree of flexibility in designing a slot antenna improves.

In the present embodiment, in an area where the core-side feeding point7a, the ground-side feeding point7b, and the resistor9are not formed, the core-side conductor21is formed with a lattice-shaped hole-formed portion24, and the ground-side conductor22is famed with a lattice-shaped hole-formed portion23. The shape of each hole of the hole-formed portion is not limited to a quadrilateral shape, but may be a polygonal shape other than the quadrilateral shape (for example, triangular and hexagonal shapes), circular, and other shapes.

A resistor9for wire-breaking detection may be provided in the conductive film20. The resistor9is arranged to extend over the slot10, such that one end of the resistor9is connected to the core-side conductor21, and the other end of the resistor9is connected to the ground-side conductor22. As a result, a closed circuit is formed through the core wire8caof the coaxial cable8c, the core-side conductor21, the resistor9, the ground-side conductor22, and the outer conductor8cbof the coaxial cable8c. With the resistor9, a device connected to the other end of the coaxial cable8ccan determine that the antenna1is not connected to the coaxial cable8cin a case where a resistance value in a predetermined range is not detected from the closed circuit including the resistor9. Such a device may also determine breaking of the glass plate60by detecting a change in the resistance value.

FIG. 3is a plan view illustrating a configuration example of the antenna according to the first embodiment.FIG. 3illustrates a state in which the connector8(seeFIG. 2) connected to one end of the coaxial cable8cis detached from the conductive film20with which the antenna1is formed.

The conductive film20with which the antenna1is formed includes: the lower-side outer edge91and the upper-side outer edge92, which are opposite to each other in the Y axis direction; the left-side outer edge93and the right-side outer edge94, which are opposite to each other in the X axis direction; and a feeding portion including the core-side feeding point7aand the ground-side feeding point7b, which are opposite to each other in the X axis direction. InFIG. 3, the lower-side outer edge91includes a lower edge right portion115, a lower edge intermediate portion116, and a lower edge left portion117. The upper-side outer edge92includes an upper edge left portion111and an upper edge right portion112. The right-side outer edge94includes a right edge upper portion113and a right edge lower portion114.

The conductive film20includes the slot10. The slot10includes a vertical slot11, a horizontal slot12, a right wide slot14, and a left wide slot15. The right wide slot14, the vertical slot11, the horizontal slot12, and the left wide slot15are connected consecutively in this order.

The vertical slot11is an example of a first slot. The vertical slot11extends in the Y axis direction between the core-side feeding point7aand the ground-side feeding point7b. The vertical slot11includes, in the Y axis direction, one end located at the same side as the lower-side outer edge91and another end located at the same side as the upper-side outer edge92.

The horizontal slot12is an example of a second slot. The horizontal slot12includes one end connected at a connection point11awith the one end of the vertical slot11located at the same side as the lower-side outer edge91. The horizontal slot12extends in the X axis direction at the same side as the left-side outer edge93with respect to the vertical slot11.

The right wide slot14is an example of a third slot. The right wide slot14includes one end connected at a connection point11bwith the another end of the vertical slot11located at the same side as the upper-side outer edge92and another end (open end14a) that is open through the right-side outer edge94. The connection point11bis located at a side opposite the connection point11awith respect to a portion where the vertical slot11is sandwiched between the core-side feeding point7aand the ground-side feeding point7b. The right wide slot14extends at one side of the vertical slot11opposite from the horizontal slot12. Specifically, the right wide slot14extends in the X axis direction at the same side as the right-side outer edge94with respect to the vertical slot11. The right wide slot14has a portion of which slot width is wider than the vertical slot11.

The left wide slot15is an example of a fourth slot. The left wide slot15has one end connected at a connection point12ewith another end of the horizontal slot12at the same side as the left-side outer edge93. The left wide slot15extends at one side of the horizontal slot12opposite from the vertical slot11. In other words, the horizontal slot12is located between the vertical slot11and the left wide slot15. The left wide slot15extends at the same side as the upper-side outer edge92with respect to a virtual extension line extending in a direction in which the horizontal slot12extends. The left wide slot15has a portion of which slot width is wider than the horizontal slot12.

Here, in a case where the vehicle body is made of metal, if a radiating element of a silver paste antenna in a line shape is placed near the vehicle body on window glass, the reception gain of the antenna will decrease due to interference with the metal.

However, because the antenna according to the present embodiment is a slot antenna, the electric field generated by a current flowing through the conductive film20is formed in a closed manner inside the conductive film20and is less susceptible to interference with metal or resin.

Therefore, even when a metal such as a defogger and a vehicle body or a resin portion of the vehicle body is in proximity to a peripheral area of the antenna according to the present embodiment, stable characteristics can be obtained. Furthermore, even if a metal film such as a transparent conductive film is famed in the peripheral portion, characteristics that are less susceptible to interference can be obtained.

The frequencies of communication waves differ from country to country, and carriers use different frequency bands within a country. Therefore, an antenna corresponding to a wide frequency range is preferable so as to be able to transmit and receive a plurality of communication waves.

In a UHF (Ultra High Frequency) wave used for communication, the antenna according to the present embodiment is configured to be able to communicate, for example, in three of the bands (0.698 GHz to 0.96 GHz (low band), 1.71 GHz to 2.17 GHz (medium band), and 2.5 GHz to 2.69 GHz (high band)) used for LTE (Long Term Evolution).

Furthermore, the antenna according to the present embodiment is also suitable for transmission and reception of electromagnetic waves in the ISM (Industry Science Medical) band. The ISM band includes 0.863 GHz to 0.870 GHz (Europe), 0.902 GHz to 0.928 GHz (USA), and 2.4 GHz to 2.5 GHz (used all over the world). Examples of communication standards using the 2.4 GHz band, which is one of the ISM bands, include wireless LAN (Local Area Network) using DSSS (Direct Sequence Spread Spectrum) compliant with IEEE802.11b, Bluetooth (registered trademark), and some of the FWA (Fixed Wireless Access) system. The electromagnetic waves transmitted and received by the antenna according to the present embodiment are not limited to these frequency bands, and can also be applied to frequency bands up to 6 GHz in the fifth generation communication (5G) standard.

In the antenna1according to the first embodiment, the vertical slot11, the horizontal slot12, the right wide slot14, and the left wide slot15are famed with the conductive film20. Therefore, the antenna1can support a plurality of wide frequency bands. The antenna1having the shape illustrated inFIG. 3is suitable for transmitting and receiving electromagnetic waves in wide frequency bands used for LTE.

Furthermore, in field tests of communication services in recent years, vertical polarization tends to be regarded as important in low frequency bands. In the antenna1according to the first embodiment, the horizontal slot12, the right wide slot14, and the left wide slot15have a slot component that extends in a substantially horizontal direction when the antenna1is attached to the vehicle. Therefore, the antenna1is suitable for transmitting and receiving vertically polarized electromagnetic waves.

Therefore, since the antenna according to the present embodiment is provided on the glass plate, the antenna has less impact on the design and aerodynamic characteristics of the vehicle, and since the antenna is provided on an outer peripheral area of the glass plate, the antenna has less impact on the appearance, and furthermore, the antenna can support transmission and reception of electromagnetic waves in wide frequency ranges.

It should be noted that when the antenna1is attached so that the horizontal slot12, the right wide slot14, and the left wide slot15have a slot component that extends in a substantially vertical direction when the antenna1is attached to the vehicle, the antenna1is suitable for transmitting and receiving horizontally polarized electromagnetic waves.

InFIG. 3, the right-side outer edge94has an inclined portion which is inclined with respect to a virtual line14bpassing through the open end14aand perpendicular to the direction in which the right wide slot14extends, and which extends at one side of the virtual line14bopposite from the right wide slot14. In the present embodiment, the right-side outer edge94includes a right edge lower portion114which is an inclined portion extending at the same side as the vertical slot11with respect to a virtual extension line extending in a direction in which the right wide slot14extends.

The right edge lower portion114is an outer edge portion of the right-side outer edge94at the same side as the lower-side outer edge91with respect to the open end14a. The right edge lower portion114extends at one side of the virtual line14bopposite from the right wide slot14in such a manner that a portion of the conductive film20expands. The right edge lower portion114is inclined with respect to a virtual extension line extending in a direction in which the right wide slot14extends, and extends in such a manner that the portion of the conductive film20protrudes from the virtual line14b. For example, the right edge lower portion114is inclined with respect to the virtual line14bin such a manner that a maximum external dimension W1of the conductive film20in the X axis direction increases.

The right wide slot14and the vertical slot11form a notch antenna in which a slot is bent into a right angle at one portion (connection point11b). Since the currents flowing along both sides of the right wide slot14flow in opposite phases and close to each other, a magnetic flux generated by the current flowing along one side and a magnetic flux generated by the current flowing along the other side are generated in directions to cancel each other. Likewise, since the currents flowing along both sides of the vertical slot11flow in opposite phases and close to each other, a magnetic flux generated by the current flowing along one side and a magnetic flux generated by the current flowing along the other side are generated in directions to cancel each other. Therefore, these currents represented by white arrows inFIG. 3do not appreciably contribute to the radiation of the antenna1.

Conversely, as for the currents flowing along the right-side outer edge94, a current flowing along the right edge upper portion113and a current flowing along the right edge lower portion114flow in substantially the same phase, and the magnetic fluxes generated by these currents are not in directions to cancel each other. Therefore, these currents represented by black arrows inFIG. 3contribute to the radiation of the antenna1. Since a relatively large conductor area exists between the right edge upper portion113and the virtual line14b, the flow of the current along the right edge lower portion114is less likely to be restricted.

As described above, the right-side outer edge94includes a right edge lower portion114inclined with respect to the virtual line14bas an inclined portion that extends at one side of the virtual line14bopposite from the right wide slot14. Since an inclined portion such as the right edge lower portion114extends, a current excited along the right-side outer edge94(i.e., a current contributing to radiation of the antenna1) increases. As a result, the antenna gain of the antenna1increases. In the antenna1, not only the slot10but also an inclined portion such as the right edge lower portion114achieves an effect (i.e., the antenna1does not operate in a single frequency), so that the antenna1functions as a slot antenna operating at frequencies in wide frequency ranges.

In the present embodiment, the right edge lower portion114extends from the open end14a. Alternatively, the right edge lower portion114may be configured to extend to an intermediate point along the virtual line14bfrom the open end14a, and the right edge lower portion114may be inclined from the intermediate point with respect to the virtual line14b.

The inclined portion that is inclined with respect to the virtual line14band that extends at one side of the virtual line14bopposite from the right wide slot14may be the right edge upper portion113. When the right edge upper portion113is inclined in this manner, the antenna gain of the antenna1improves. As for the aspect in which the right edge upper portion113is inclined, the above explanation about the right edge lower portion114is incorporated herein by reference. The inclined portion that is inclined with respect to the virtual line14band that extends at one side of the virtual line14bopposite from the right wide slot14may include both of the right edge upper portion113and the right edge lower portion114. Even in an aspect in which the right-side outer edge94has an inclined portion that is inclined with respect to the virtual line14band that extends at the same side as the right wide slot14with respect to the virtual line14b, the antenna gain of the antenna1improves, and the antenna1functions as a slot antenna operating at frequencies in wide frequency ranges.

InFIG. 3, the conductive film20may have a recessed portion11cpartially expanding a slot width of the vertical slot11. The recessed portion11cis a portion of the vertical slot11where the ground-side conductor22is recessed. When the recessed portion11cis provided, the capacitive coupling between the core wire8caof the coaxial cable8cand the ground-side feeding point7bdecreases, and accordingly, the return loss characteristics and the antenna gain of the antenna1improves. The recessed portion11ccan suppress fluctuations in the characteristic of the antenna1, even when the position where the connector8is mounted on the feeding portion is slightly shifted. The recessed portion11callows the mounting surface of the connector8to be easily bonded to the recessed portion11cwith an adhesive member such as double-sided tape, and accordingly, the ease of installation of the connector8improves.

InFIG. 3, the conductive film20includes, for example, another outer edge that extends at one side of the virtual extension line, extending in the direction in which the right wide slot14extends, opposite from the vertical slot11. The upper-side outer edge92is an example of the another outer edge. The upper-side outer edge92includes a second inclined portion that is inclined with respect to the virtual extension line extending in the direction in which the right wide slot14extends. The upper edge right portion112is an example of the second inclined portion. A distance a1between the upper edge right portion112and the right wide slot14at the another end (the open end14a) of the right wide slot14is longer than a distance a2between the upper edge right portion112and the right wide slot14at the one end (the connection point11b) of the right wide slot14. In the present embodiment, the distance in the Y axis direction between the upper edge right portion112and the right wide slot14increases away from the connection point11btoward the open end14a. In other words, the conductor area width, in the Y axis direction, of the conductor area21a, which is present between the upper edge right portion112and the right wide slot14, increases away from the connection point11btoward the open end14a. InFIG. 3, the shortest distance in the Y axis direction between the upper edge right portion112and the open end14ais longer than the shortest distance in the Y axis direction between the upper edge right portion112and the connection point11b.

In this manner, the upper-side outer edge92includes the upper edge right portion112as an example of the second inclined portion. Because of the existence of the second inclined portion such as the upper edge right portion112, the size of the conductive film20in the Y axis direction can be reduced (in particular, the size in the Y axis direction can be reduced in a central area of the conductive film20in the X axis direction). The upper edge right portion112is formed along the light shielding film edge65c(seeFIG. 1) so that a part of the conductive film20is not exposed from the light shielding film65. As a result, the design of the window glass100for the vehicle and the design of the vehicle improve.

InFIG. 3, the conductive film20includes, for example, a third outer edge that extends at one side of the virtual extension line, extending in the direction in which the horizontal slot12extends, opposite from the vertical slot11. The lower-side outer edge91is an example of a third outer edge. The lower-side outer edge91includes a third inclined portion inclined with respect to the virtual extension line extending in a direction in which the right wide slot14extends. The lower edge right portion115is an example of the third inclined portion. A distance a3between the lower edge right portion115and the right wide slot14at the another end (the open end14a) of the right wide slot14is shorter than a distance a4between the lower edge right portion115and the right wide slot14at the one end (the connection point11b) of the right wide slot14. In the present embodiment, a distance in the Y axis direction between the lower edge right portion115and the right wide slot14decreases away from the connection point11btoward the open end14a. In other words, the conductor area width, in the Y axis direction, of the conductor area22a, which is present between the lower edge right portion115and the right wide slot14, decreases away from the connection point11btoward the open end14a.

In this manner, the lower-side outer edge91includes the lower edge right portion115as an example of the third inclined portion. Because of the extension of the third inclined portion such as the lower edge right portion115, the size of the conductive film20in the Y axis direction can be reduced (in particular, the size in the Y axis direction can be reduced in a right end area of the conductive film20in the X axis direction). The lower edge right portion115is formed along the lower frame edge71cof the window frame70(seeFIG. 1), so that a part of the conductive film20does not overlap the frame edge of the window frame70while the window glass100for the vehicle is attached to the window frame70. Accordingly, a contact between the conductive film20and the window frame70can be prevented. In addition, an adhesive pasted to a peripheral portion along the frame edge of the window frame70can be prevented from coming into contact with the conductive film20. The adhesive bonds a peripheral portion along the glass edge of the glass plate60and a peripheral portion along the frame edge of the window frame70.

It should be noted that the shortest distance between the lower-side outer edge91and the window frame70(more specifically, the lower frame edge71c) is preferably equal to or more than 5 mm and equal to or less than 100 mm. Since the shortest distance is set to this kind of dimension, the lower-side outer edge91can be brought into proximity with the window frame70(more specifically, the lower frame edge71c). For this reason, even when the width of the light shielding film65is narrow, at least a part of the antenna1, more preferably, the entire antenna1, is hidden by the light shielding film65. As a result, the design of the window glass100for the vehicle and the design of the vehicle improve. The sizes of the shortest distance in the antenna2are similar to the sizes described above.

InFIG. 3, the conductive film20includes, for example, a step portion130that includes a plurality of slot edges135,136extending in parallel with the direction in which the horizontal slot12extends, and that changes the slot width of the left wide slot15in a stepwise manner with the plurality of slot edges135,136. The step portion130improves the return loss characteristics of the antenna1. In addition, since one of the slot edges is formed in a stepwise manner, the current path is extended and the degree of coupling with an opposing slot edge is changed, so that the frequency characteristics of the antenna gain are flattened. The step portion130includes two steps, i.e., the slot edges135,136, and is formed between the virtual extension line extending in the direction in which the horizontal slot12extends and the slot lower edge of the left wide slot15. The left wide slot15includes slot portions131to134.

The slot portion131includes one end connected at the connection point12eto the another end of the horizontal slot12. The slot portion131is inclined toward the upper-side outer edge92with respect to the virtual extension line extending in the direction in which the horizontal slot12extends. The slot width of the slot portion131is substantially the same as the slot width of the horizontal slot12.

The slot portion132includes one end connected to another end of the slot portion131. The slot portion132is formed by the slot edge135and the slot edge138both of which are in parallel with the direction in which the horizontal slot12extends. The slot width of the slot portion132is substantially the same as the slot width of the slot portion131.

The slot portion133includes one end connected to another end of the slot portion132. The slot portion133is formed by the slot edge136and a slot edge139. The slot edge136is in parallel with the virtual extension line extending in the direction in which the horizontal slot12extends. The slot edge139is inclined toward the upper-side outer edge92with respect to the virtual extension line. The slot width of the slot portion133is wider than the slot width of the slot portion132, and the slot width of the slot portion133gradually increases away from the one end of the slot portion133toward the another end of the slot portion133.

The slot portion134includes one end connected to another end of the slot portion133and another end (open end15a) that is open through the upper-side outer edge92. The open end15arepresents an open end of the left wide slot15. The upper-side outer edge92is divided by the open end15ainto the upper edge left portion111and the upper edge right portion112. The slot width of the slot portion134is substantially the same as the slot width of the slot portion133. The slot portion134extends in parallel with the vertical slot11.

The step portion130includes an inclined slot edge137which is a slot edge for a slot portion connecting the slot portion133and the slot portion134. The inclined slot edge137improves the return loss characteristics of the antenna1. The inclined slot edge137is inclined toward the upper-side outer edge92with respect to the slot edge136.

FIG. 4is a drawing illustrating an example of a state in which a coaxial cable5cis connected to a pair of feeding points4a,4bin the antenna2according to a second embodiment.FIG. 4illustrates a state in which one end of the coaxial cable5cis indirectly connected by the connector5to the core-side feeding point4aand to the ground-side feeding point4bof the antenna2.

In the second embodiment, descriptions about configurations and effects similar to those of the first embodiment will be omitted or simplified by referring to the above descriptions.

The core-side feeding point4a, the ground-side feeding point4b, the coaxial cable5c, a core wire5ca, an outer conductor5cb, an insulator5cc, a connector5, and a resistor6have configurations similar to the core-side feeding point7a, the ground-side feeding point7b, the coaxial cable8c, the core wire8ca, the outer conductor8cb, the connector8, and the resistor9, respectively.

The antenna2is a slot antenna formed with a conductive film25. The antenna2functions as a slot antenna with a slot30(elongated cutout) formed in the conductive film25. In the second embodiment, the conductive film25includes a lower-side outer edge96and an upper-side outer edge97, which are opposite to each other in the Y axis direction, and includes a right-side outer edge98and a left-side outer edge99, which are opposite to each other in the X axis direction perpendicular to the Y axis direction.

In the second embodiment, the Y axis direction is an example of the first direction, and the X axis direction is an example of the second direction different from the first direction. The left-side outer edge99is an example of one outer edge. The upper-side outer edge97is an example of another outer edge. The lower-side outer edge96is an example of a third outer edge. The right-side outer edge98is an example of a fourth outer edge.

The conductive film25includes a core-side conductor26extending to a first side with respect to the slot30and a ground-side conductor27extending to a second side with respect to the slot30. In the present embodiment, in an area where the core-side feeding point4a, the ground-side feeding point4b, and the resistor6are not formed, the core-side conductor26is formed with a lattice-shaped hole-formed portion29, and the ground-side conductor27is formed with a lattice-shaped hole-formed portion28.

FIG. 5is a plan view illustrating a configuration example of the antenna2according to the second embodiment.FIG. 5illustrates a state in which the connector5(seeFIG. 4) connected to one end of the coaxial cable5cis detached from the conductive film25with which the antenna2is formed.

The conductive film25with which the antenna2is formed includes: the lower-side outer edge96and the upper-side outer edge97, which are opposite to each other in the Y axis direction; the right-side outer edge98and the left-side outer edge99, which are opposite to each other in the X axis direction; and a feeding portion including the core-side feeding point4aand the ground-side feeding point4b, which are opposite to each other in the X axis direction. InFIG. 5, the lower-side outer edge96includes a lower edge left portion125, a lower edge intermediate portion126, and a lower edge right portion127. The upper-side outer edge97includes an upper edge right portion121and an upper edge left portion122. The left-side outer edge99ofFIG. 5includes at least one straight portion. The right-side outer edge98ofFIG. 5includes a corner portion129in an upper portion of the right-side outer edge98. The shape of the right-side outer edge98is in a stepped shape. The left-side outer edge99includes a left edge upper portion123and a left edge lower portion124.

The conductive film25includes a slot30. The slot30includes a vertical slot31, a horizontal slot32, a left wide slot34, and a right wide slot35. The left wide slot34, the vertical slot31, the horizontal slot32, and the right wide slot35are connected consecutively in this order.

The vertical slot31is an example of a first slot. The vertical slot31extends in the Y axis direction between the core-side feeding point4aand the ground-side feeding point4b. The vertical slot31includes one end located at the same side as the lower-side outer edge96in the Y axis direction and another end located at the same side as the upper-side outer edge97in the Y axis direction.

The horizontal slot32is an example of the second slot. The horizontal slot32includes one end connected at a connection point31awith the another end of the vertical slot31at the same side as the lower-side outer edge96. The horizontal slot32extends in the X axis direction at the same side as the right-side outer edge98with respect to the vertical slot31.

The left wide slot34is an example of the third slot. The left wide slot34includes one end connected at a connection point31bwith the another end of the vertical slot31at the same side as the upper-side outer edge97and another end (open end34a) that is open through the left-side outer edge99. The connection point31bis located at a side opposite the connection point31awith respect to a portion where the vertical slot31is sandwiched between the core-side feeding point4aand the ground-side feeding point4b. The left wide slot34extends at one side of the vertical slot31opposite from the horizontal slot32. More specifically, the left wide slot34extends in the X axis direction at the same side as the left-side outer edge99with respect to the vertical slot31. The left wide slot34has a portion of which slot width is wider than the vertical slot31.

The right wide slot35is an example of the fourth slot. The right wide slot35includes one end connected at a connection point32ewith another end of the horizontal slot32at the same side as the right-side outer edge98. The right wide slot35extends at one side of the horizontal slot32opposite from the vertical slot31. More specifically, the horizontal slot32is located between the vertical slot31and the right wide slot35. The right wide slot35extends at the same side as the upper-side outer edge97with respect to a virtual extension line extending in a direction in which the horizontal slot32extends. The right wide slot35has a portion of which slot width is wider than the horizontal slot32.

In the antenna2according to the second embodiment, the vertical slot31, the horizontal slot32, the left wide slot34, and the right wide slot35are formed with the conductive film25. Therefore, the antenna2can support a plurality of wide frequency bands. The antenna2having the shape illustrated inFIG. 5is particularly suitable for transmitting and receiving electromagnetic waves used for ISM. In the antenna2according to the second embodiment, the horizontal slot32, the left wide slot34, and the right wide slot35have a slot component that extends in a substantially horizontal direction when the antenna2is attached to the vehicle. Therefore, the antenna2is suitable for transmitting and receiving vertically polarized electromagnetic waves.

It should be noted that when the antenna2is attached so that the horizontal slot32, the left wide slot34, and the right wide slot35have a slot component that extends in a substantially vertical direction when the antenna2is attached to the vehicle, the antenna2is suitable for transmitting and receiving horizontally polarized electromagnetic waves.

InFIG. 5, the left-side outer edge99has the left edge lower portion124as an inclined portion that is inclined with respect to the virtual line34band that extends at one side of the virtual line34bopposite from the left wide slot34. Since an inclined portion such as the left edge lower portion124extends, a current excited along the left-side outer edge99(i.e., a current contributing to radiation of the antenna2) increases. As a result, the antenna gain of the antenna2increases. For example, the left edge lower portion124is inclined with respect to the virtual line34bin such a manner that a maximum external dimension W3of the conductive film25in the X axis direction increases.

Alternatively, the left edge lower portion124may be configured to extend to an intermediate point along the virtual line34bfrom the open end34a, and the left edge lower portion124may be inclined from the intermediate point with respect to the virtual line34b. The inclined portion that is inclined with respect to the virtual line34band that extends at one side of the virtual line34bopposite from the left wide slot34may be any one of or both of the left edge upper portion123and the left edge lower portion124. Even in an aspect in which the left-side outer edge99has an inclined portion that is inclined with respect to the virtual line34band that extends at the same side as the left wide slot34with respect to the virtual line34b, the antenna gain of the antenna2improves, and the antenna2functions as a slot antenna operating at frequencies in wide frequency ranges.

InFIG. 5, the conductive film25may have a recessed portion31cpartially expanding a slot width of the vertical slot31. The recessed portion31cimproves the return loss characteristics of the antenna2and the antenna gain. The recessed portion31ccan suppress fluctuations in the characteristic of the antenna2, even when the position where the connector5is mounted on the feeding portion is slightly shifted. In addition, the recessed portion31cimproves the ease of installation of the connector5.

The upper-side outer edge97includes an upper edge left portion122as an example of a second inclined portion. Because of the existence of the second inclined portion such as the upper edge left portion122, the size of the conductive film25in the Y axis direction can be reduced (in particular, the size in the Y axis direction can be reduced in a central area of the conductive film25in the X axis direction). The upper edge left portion122is formed along the light shielding film edge65c(seeFIG. 1) so that a part of the conductive film25is not exposed from the light shielding film65. As a result, the design of the window glass100for the vehicle and the design of the vehicle improve.

The lower-side outer edge96includes the lower edge left portion125as an example of the third inclined portion. Because of the existence the third inclined portion such as the lower edge left portion125, the size of the conductive film25in the Y axis direction can be reduced (in particular, the size in the Y axis direction can be reduced in a left end area of the conductive film25in the X axis direction). The lower edge left portion125is formed along the lower frame edge71cof the window frame70(seeFIG. 1), so that a part of the conductive film25does not overlap the frame edge of the window frame70while the window glass100for the vehicle is attached to the window frame70. Accordingly, a contact between the conductive film25and the window frame70can be prevented. In addition, an adhesive pasted to a peripheral portion along the frame edge of the window frame70can be prevented from coming into contact with the conductive film25.

InFIG. 5, the conductive film25includes, for example, a step portion140that includes a plurality of slot edges145,146extending in parallel with the direction in which the horizontal slot32extends, and that changes the slot width of the right wide slot35in a stepwise manner with the plurality of slot edges145,146. The step portion140improves the return loss characteristics of the antenna2. The step portion140includes two steps, i.e., the slot edges145,146, and is formed between the virtual extension line extending in the direction in which the horizontal slot32extends and the slot lower edge of the right wide slot35. The right wide slot35includes slot portions141to144.

The slot width of the slot portion141is substantially the same as the slot width of the horizontal slot32. The slot portion142is formed by the slot edge145and the slot edge148both of which are in parallel with the direction in which the horizontal slot32extends. The slot width of the slot portion142is wider than the slot width of the slot portion141. The slot portion143is formed by a slot edge146and a slot edge149. The slot edge146is in parallel with the virtual extension line extending in the direction in which the horizontal slot32extends. The slot edge149is inclined toward the upper-side outer edge97with respect to the virtual extension line extending in the direction in which the horizontal slot32extends. The slot width of the slot portion143is wider than the slot width of the slot portion142, and the slot width of the slot portion143gradually increases away from the one end of the slot portion143toward the another end of the slot portion143. The slot portion144includes one end connected to another end of the slot portion143and another end (open end35a) that is open through the upper-side outer edge97. The open end35arepresents an open end of the right wide slot35. The upper-side outer edge97is divided by the open end35ainto the upper edge right portion121and the upper edge left portion122. The slot width of the slot portion144is substantially the same as the slot width of the slot portion143. The slot portion144extends in parallel with the vertical slot31.

The conductive film25includes a protruding portion26bpartially narrowing the slot width of the right wide slot35. The protruding portion26bimproves the antenna gain of the antenna2. The protruding portion26bis formed to protrude in the Y axis direction from the core-side conductor26, i.e., extend toward the lower-side outer edge96from a portion at the same side as the upper-side outer edge97.

The conductive film25includes an upper-side outer edge97and a right-side outer edge98, i.e., an example of a pair of an outer edge forming the corner portion129of the conductive film25. The upper-side outer edge97includes the open end35aof the right wide slot35, and the right-side outer edge98extends at one side of the right wide slot35opposite from the horizontal slot32. The corner portion129, where the upper-side outer edge97and the right-side outer edge98intersect, is recessed toward the inside of the conductive film25. Since the corner portion129is recessed toward the inside, the antenna gain of the antenna2improves. In the corner portion129, a length recessed in the Y axis direction with respect to the upper-side outer edge97is longer than a length recessed in the X axis direction with respect to the right-side outer edge98.

FIG. 6is an exploded view illustrating a connector for supplying power to an antenna. The connector illustrated inFIG. 6corresponds to the connector5or the connector8described above. The connector has a three-layer structure in which first to third layers are stacked in the Z axis direction.

The upper layer81is an example of a first layer, and is an insulating layer having a substantially T-shaped outer shape. The upper layer81is a resin layer such as, for example, a polyimide film. Openings81a,81b, and81cpenetrating the upper layer81are provided at three vertices of a substantially T-shape. The opening81bis formed in one of side portions of the substantially T-shape, and the opening81cis formed in the other of the side portions of the substantially T-shape. The opening81ais formed in a trunk portion of the substantially T-shape. Between the opening81band the opening81c, an opening81epenetrating the upper layer81is famed. Between the opening81eand the opening81a, an opening81dpenetrating the upper layer81is famed. The openings81a,81b, and81chave circular shapes. The opening81ehas a notch shape, one end of which is open. The opening81dhas a substantially rectangular shape.

The lower layer84is an example of the third layer, and is an insulating layer having a substantially T-shaped outer shape. The lower layer84is a resin layer such as, for example, a polyimide film. Openings84a,84b, and84cpenetrating the lower layer84are provided at three vertices of a substantially T-shape. The opening84bis formed in one of side portions of the substantially T-shape, and the opening84cis formed in the other of the side portions of the substantially T-shape. The opening84ais formed in a trunk portion of the substantially T-shape. The openings84a,84b, and84chave circular shapes. A central portion of the lower layer84corresponds to a contact surface (an attachment surface of the connector) where the connector comes into contact with the recessed portion11c(seeFIG. 3) or the recessed portion31c(seeFIG. 5). An adhesive member85such as a double-sided tape is attached to the surface of the central portion of the lower layer84.

The middle layers82,83are examples of a second layer, and is a layer sandwiched by the first layer and the third layer. The middle layer82is a conductor layer including, in a state where the middle layer82is sandwiched between the upper layer81and the lower layer84, a portion facing the openings81b,84b, a portion facing the openings81c,84c, and a portion connecting between these portions. The middle layer83is a conductor layer including, in a state where the middle layer83is sandwiched between the upper layer81and the lower layer84, a portion facing the openings81a,84a, a portion facing the opening81d, and a portion connecting between these portions. The middle layers82,83are not electrically connected with each other. The middle layers82,83are, for example, metal layers made of copper, silver, or the like.

In this manner, the connector connecting a coaxial cable to the antenna has a three-layer structure in which the middle layers82,83are sandwiched between the upper layer81and the lower layer84. One end of the coaxial cable is arranged on the upper layer81of the connector having the layer structure described above. A tip of the core wire of the coaxial cable is bonded with the middle layer83through the opening81dby solder or the like. Therefore, the core wire is electrically connected to the core-side feeding point7afacing the opening84avia the middle layer83. The outer conductor of the coaxial cable is bonded with the middle layer82through the opening81eby solder or the like. The outer conductor is electrically connected to the ground-side feeding point7bfacing the openings84b,84cvia the middle layer82.

First Example

The first example illustrates a result obtained by measuring an antenna gain of the antenna1according to the first embodiment (FIGS. 2, 3) and an antenna that did not have an inclined right edge lower portion114(hereinafter referred to as “comparative antenna”). The antenna1had a right edge lower portion114inclined with respect to the virtual line14b. In contrast, the comparative antenna did not have an inclined portion such as the right edge lower portion114.

The antenna gain was measured by setting, in the center of a turn table, a center of a vehicle on which a rear glass attached with an antenna was installed. At this time, the rear glass was inclined about 20 degrees with respect to the horizontal plane. Then, a vertically polarized electromagnetic wave and a horizontally polarized electromagnetic wave were transmitted from a transmission antenna, and the antenna gains for the vertical polarization and the horizontal polarization were measured by changing an elevation θe with respect to the antenna and an azimuth θr in a horizontal plane with respect to the antenna. When the transmission antenna was in a plane in parallel with the ground, the elevation θe was defined as 0 degrees, and when the transmission antenna was in the zenith direction, the elevation θe was defined as 90 degrees. When the transmission antenna was in front of the vehicle, the azimuth θr was defined as 0 degrees, and when the transmission antenna was at sides of the vehicle, the azimuth θr was defined as ±90 degrees. This is also applicable to the examples explained below, unless otherwise specified.

While the elevation θe was changed by 2 degrees from 0 degrees to 20 degrees, and the azimuth θr was changed by 2 degrees from 0 degrees to 360 degrees, average values of antenna gains for the vertical polarization and the horizontal polarization measured at every 10 MHz in each frequency band of LTE were adopted as a vertical polarization average antenna gain and a horizontal polarization average antenna gain, respectively. A combination of a vertical polarization average antenna gain and a horizontal polarization average antenna gain was adopted as a vertical-polarization-and-horizontal-polarization-combined average antenna gain. In the examples described below, unless otherwise specified, the vertical-polarization-and-horizontal-polarization-combined average antenna gain will be referred to as an average antenna gain. The frequency bands of LTE here are considered to include three bands, i.e., 698 GHz to 0.96 GHz (low band), 1.71 GHz to 2.17 GHz (medium band), and 2.5 GHz to 2.69 GHz (high band). This is also applicable to the examples described later, unless otherwise specified.

With regard to the average antenna gain, an obtained result was that the antenna1having the inclined right edge lower portion114achieved an antenna gain 0.1 dB higher in the low band, an antenna gain 0.4 dB higher in the medium band, and an antenna gain 0.2 dB higher in the high band than the corresponding antenna gains of the comparative antenna that did not have an inclined right edge lower portion114.

Second Example

FIG. 7is a graph illustrating a return loss in a case where the antenna1according to the first embodiment did not have the recessed portion11c.FIG. 8is a graph illustrating a return loss in a case where the antenna1according to the first embodiment had the recessed portion11c. When the recessed portion11cwas provided, the capacitive coupling between the core wire8caof the coaxial cable8cand the ground-side feeding point7bdecreases. An obtained result was that the return loss characteristics of the antenna1in the low band improved (see black arrows in the figures) when the recessed portion11cwas provided as compared with when the recessed portion11cwas not provided.

FIG. 9is a graph illustrating frequency characteristics of an antenna gain in a case where the antenna1according to the first embodiment did not have the recessed portion11c.FIG. 10is a graph illustrating frequency characteristics of an antenna gain in a case where the antenna1according to the first embodiment had the recessed portion11c. The vertical axis represents an average antenna gain.

As illustrated in the figures, the frequency characteristics of the average antenna gain of the antenna1in the low band was flattened when the recessed portion11cwas provided as compared with when the recessed portion11cwas not provided. When the recessed portion11cwas not provided, the average antenna gain of the antenna1in the low band was −6.4 dBi, and when the recessed portion11cwas provided, the average antenna gain of the antenna1in the low band was −6.2 dBi, which means that the antenna gain improved. When the recessed portion11cwas not provided, the average antenna gain of the antenna1in the high band was −5.1 dBi, and when the recessed portion11cwas provided, the average antenna gain of the antenna1in the high band was −4.8 dBi, which means that the antenna gain improved.

Third Example

FIG. 11is a graph illustrating a return loss in a case where the antenna1according to the first embodiment did not have the step portion130.FIG. 12is a graph illustrating a return loss in a case where the antenna1according to the first embodiment had the step portion130. An obtained result was that the return loss characteristics of the antenna1in the low band improved (see black arrows in the figures) when the step portion130was provided as compared with when the step portion130was not provided.

FIG. 13is a graph illustrating frequency characteristics of an antenna gain in a case where the antenna1according to the first embodiment did not have the step portion130.FIG. 14is a graph illustrating frequency characteristics of an antenna gain in a case where the antenna1according to the first embodiment had the step portion130. The vertical axis represents an average antenna gain. As illustrated in the figures, the frequency characteristics of the average antenna gain of the antenna1in the low band was flattened when the step portion130was provided as compared with when the step portion130was not provided.

Fourth Example

FIG. 15is a graph illustrating a return loss in a case where the antenna2according to the second embodiment did not have the protruding portion26b.FIG. 16is a graph illustrating a return loss in a case where the antenna2according to the second embodiment had the protruding portion26b. An obtained result was that the return loss characteristics of the antenna2in the high band improved when the protruding portion26bwas provided as compared with when the protruding portion26bwas not provided.

FIG. 17is a graph illustrating frequency characteristics of an antenna gain in a case where the antenna2according to the second embodiment did not have the protruding portion26b.FIG. 18is a graph illustrating frequency characteristics of an antenna gain in a case where the antenna2according to the second embodiment had the protruding portion26b. The vertical axis represents an average antenna gain. When the protruding portion26bwas not provided, the average antenna gain of the antenna2in the band of 2.4 GHz to 2.48 GHz of the ISM bands was −5.2 dBi, and when the protruding portion26bwas provided, the average antenna gain was −4.8 dBi, which means that the antenna gain improved.

Fifth Example

FIG. 19is a graph illustrating a return loss in a case where the corner portion129of the antenna2according to the second embodiment was not recessed.FIG. 20is a graph illustrating a return loss in a case where the corner portion129of the antenna2according to the second embodiment was recessed. An obtained result was that the return loss characteristics of the antenna2in the band of 2.4 GHz to 2.48 GHz of the ISM bands improved when the recessed corner portion129was provided as compared with when the recessed corner portion129was not provided.

FIG. 21is a graph illustrating frequency characteristics of an antenna gain in a case where the corner portion129of the antenna2according to the second embodiment was not recessed.FIG. 22is a graph illustrating frequency characteristics of an antenna gain in a case where the corner portion129of the antenna2according to the second embodiment was recessed. The vertical axis represents an average antenna gain. When the corner portion129is not recessed, the average antenna gain of the antenna2in the band of 2.4 GHz to 2.48 GHz of the ISM bands was −4.7 dBi, and when the corner portion129was recessed, the average antenna gain was −4.4 dBi, which means that the antenna gain improved.

Sixth Example

The antenna gain and the return loss characteristics depending on a difference in the size of the width W2of the inner area22bof the ground-side conductor22(seeFIG. 3) of the antenna1according to the first embodiment were measured. The inner area22brepresents a conductor area of the ground-side conductor22between the left-side outer edge93and the virtual extension line extending in the Y axis direction through the open end15aof the left wide slot15.

FIG. 23is a graph illustrating a return loss in a case where the width W2of the inner area22bof the ground-side conductor22of the antenna1according to the first embodiment was short.FIG. 24is a graph illustrating a return loss in a case where the width W2of the inner area22bof the ground-side conductor22of the antenna1according to the first embodiment was long.FIG. 23illustrates a case where the number of rows of opened holes in the hole-formed portion23in the inner area22bwas four.FIG. 24illustrates a case where the number of rows of opened holes in the hole-formed portion23in the inner area22bwas five as illustrated inFIG. 3. An obtained result was that the return loss characteristics of the antenna1in the low band improved when the width W2of the inner area22bwas long as compared with when the width W2was short.

FIG. 25is a graph illustrating frequency characteristics of an antenna gain in a case where the width W2of the inner area22bof the ground-side conductor22of the antenna1according to the first embodiment was short.FIG. 26is a graph illustrating frequency characteristics of an antenna gain in a case where the width W2of the inner area22bof the ground-side conductor22of the antenna1according to the first embodiment was long. The vertical axis represents an average antenna gain. As illustrated in the figures, an obtained result was that the frequency characteristics of the average antenna gain of the antenna1in the low band was flattened when the width W2was long as compared with when the width W2was short.

As described above, the antenna and the window for the vehicle have been described with reference to the embodiments, but the present invention is not limited to the above-described embodiments. Various modifications and improvements are possible within the scope of the present invention, such as a combination or replacement with some or all of the other embodiments.

For example, an “end” of a slot may be a start or end point of an extension of the slot, or may be a point in proximity to the start or end point. Also, a connection portion between the slots may be connected with a curvature.

An “end” of a conductor (for example, an antenna element, a heating wire, a bus bar, or the like) may be a start or end point of an extension of the conductor, or may be a point in proximity to the start or end point which is a part of the conductor before the start or end point. Also, a connection portion between the conductors may be connected with a curvature.

The bus bar, the heating wires, the antenna element, and the feeding portion are formed by printing and sintering paste (for example, silver paste, and the like) containing, for example, a conductive metal on the surface of a vehicle-inner side of window glass. However, the method for forming the bus bar, the heating wire, the antenna element, and the feeding portion are not limited thereto. For example, the bus bar, the heating wires, the antenna element, or the feeding portion may be formed by providing a wire or foil containing a conductive substance such as copper on a vehicle-inner side surface or a vehicle-outer side surface of window glass. Alternatively, the bus bar, the heating wires, the antenna element, or the feeding portion may be pasted to window glass with an adhesive and the like, or may be provided in the inside of the window glass.

The shape of the feeding portion may be determined according to the shape of the surface on which the conductive member or the connector is mounted. For example, rectangular or polygonal shapes such as a square, an approximate square, a rectangle, or an approximate rectangle are preferable in terms of mounting. Circular shapes such as a circle, an approximate circle, an ellipse, or an approximate ellipse may be adopted.

In addition, it may be possible to employ a structure in which a conductive layer that forms at least one of a bus bar, a heating wires, and antenna element, and a feeding portion is provided inside or on a surface of a synthetic resin film, and the synthetic resin film with the conductive layer is pasted to a vehicle-inner side face or a vehicle-outer side face of a window glass. Furthermore, it may be possible to employ a structure in which a flexible circuit board formed with antenna elements is provided on a vehicle-inner side surface or a vehicle-outer side surface of a window glass.

For example, inFIG. 1, the arrangement positions of the right rear antenna1and the left rear antenna2may be exchanged with each other. The right rear antenna1and the left rear antenna2may be arranged in an upper area of the glass plate60. For example, the right rear antenna1may be arranged in a right upper area, and the left rear antenna2may be arranged in a left upper area. In a case where the right rear antenna1and the left rear antenna2are arranged in an upper area of the glass plate60, the right rear antenna1and the left rear antenna2are arranged upside-down.

Since a vehicle is a mobile object, a diversity antenna may be formed by a plurality of antennas. A multiple-input and multiple-output (MIMO) antenna, which is a function of increasing communication capacity with a plurality of antennas, may be famed.