1. Field of the Invention
The present invention relates to window glass for vehicle, having an antenna that utilizes a conductive film provided on a glass plate, and to the antenna utilizing the conductive film.
2. Description of the Related Art
In order to eliminate such inconvenience, known window glass may have an antenna function by utilizing a conductive film (for example, refer to Japanese Laid-Open Patent Publications No. 6-45817, No. 9-175166, and No. 2000-59123, and U.S. Pat. No. 5,012,255).
The Japanese Laid-Open Patent Publications No. 6-45817, No. 9-175166, and the U.S. Pat. No. 5,012,255 propose a slot antenna that utilizes a slot between the conductive film and a flange of a vehicle body to which the glass plate is fixed. In the case of the slot antenna that utilizes the slot between the conductive film and the flange of the vehicle body, the size of the slot is determined for each vehicle model, and it is difficult to cause resonance at a predetermined frequency, specifically, in order to receive radio waves in a high frequency band. Further, in order to receive radio waves in a high frequency band, a positional relationship of the flange and the conductive film needs to be accurately controlled. However, because there are differences among individual glass plates and the glass plate is fixed to the flange of the vehicle body by an adhesive, various errors may be generated in the adhesive thickness, the fixing position of the glass plate with respect to the flange, and the like. Accordingly, there is a problem in that it is difficult to form slots of identical sizes in mass production.
In addition, when a slot is provided in the conductive film in addition to the slot between the conductive film and the flange of the vehicle body as in the case of the U.S. Pat. No. 5,012,255, the effects of the conductive film may deteriorate when the additional slot is large, and there is a problem in that, when the glass plate is bent and formed by heating, a large heat distribution is generated on the glass plate depending on the existence of the conductive film, to thereby deteriorate the forming accuracy.
Accordingly, embodiments of the present invention may provide window glass for vehicle, such as automotive glass, utilizing a conductive film, and an antenna, that enable operation at a predetermined frequency regardless of the size of a slot between the conductive film and a flange of a vehicle body, and does not require accuracy in setting a glass plate to the flange of the vehicle body.
According to one aspect of the present invention, window glass for vehicle may include a glass plate, a dielectric, a conductive film arranged between the glass plate and the dielectric, and an antenna conductor having electrodes provided on a surface of the dielectric on a side opposite from the conductive film, wherein the conductive film is formed with a slot having a first end part that opens at a peripheral edge part of the conductive film, the antenna conductor includes a loop-shaped antenna element which the electrodes serve as a feeding point, wherein projections of the electrodes on a side of the glass plate are located at positions not overlapping the conductive film, and a projection of the loop-shaped antenna element on the side of the glass plate forms a crossover part that crosses the slot.
According to another aspect of the present invention, an antenna may include a glass plate, a dielectric, a conductive film arranged between the glass plate and the dielectric, and an antenna conductor having electrodes provided on a surface of the dielectric on a side opposite from the conductive film, wherein the conductive film is formed with a slot having a first end part that opens at a peripheral edge part of the conductive film, the antenna conductor includes a loop-shaped antenna element which the electrodes serve as a feeding point, projections of the electrodes on a side of the glass plate are located at positions not overlapping the conductive film, and a projection of the loop-shaped antenna element on the side of the glass plate forms a crossover part that crosses the slot.
A description will hereinafter be given of embodiments of the present invention with reference to the drawings. In the drawings used to describe the embodiments, directions refer to the directions in the figures unless otherwise indicated, and reference directions in the figures correspond to the directions indicated by symbols or reference numerals. In addition, directions that are parallel, perpendicular, and the like may tolerate an error to a certain extent that does not impair the effects of the embodiments. Further, the embodiments may be applied to a windshield mounted at the front of a vehicle, a rear window mounted at the rear of the vehicle, a side window mounted at the side of the vehicle and a window glass other than the vehicle window glass (for example, a building window glass, a ship window glass, and the like).
The vehicle window glass 100 includes the glass plate 11, the glass plate 12, a conductive film 13, and an antenna conductor 17. The glass plate 12 is used as a dielectric that sandwiches the conductive film 13 with the first glass plate 11. The glass plate 11 and the glass plate 12 have the same size, and outer peripheral edges 11a through 11d of the glass plate 11 and outer peripheral edges 12a through 12d of the glass plate 12 have matching shapes when viewed in a direction (hereinafter referred to as a “laminating direction”) in which the glass plate 12, the conductive film 13, and the glass plate 11 are laminated. An peripheral edge part 13a of the conductive film 13, that is interposed between the glass plate 11 and the glass plate 12, is offset by a predetermined distance in an in-plane direction from the outer peripheral edge 11a of the glass plate 11, and a slot 23, having a first end part 23a that opens at the peripheral edge part 13a of the conductive film 13, is formed. In addition, an antenna conductor 17 includes a loop-shaped antenna element 15, which a pair of electrodes 16 formed by electrodes 16A and 16B serve as a feeding point, on the glass plate 12 opposite to the conductive film 13.
The electrodes 16 are provided on a surface of the glass plate 12 opposite to the conductive film 13, at positions not overlapping the conductive film 13 when the electrodes 16 are projected onto the glass plate 11, that is, at positions closer to the outer peripheral edge 11a of the glass plate 11 than the peripheral edge part 13a of the conductive film 13. In other words, as illustrated in
The loop-shaped antenna element 15 is provided on the surface of the glass plate 12 on the opposite side from the conductive film 13, so as to intersect with the slot 23 in the laminating direction. In other words, as illustrated in
According to such a configuration, when the electrodes 16 is fed, the loop-shaped antenna element 15 and the slot 23 that mutually cross in the laminating direction are electromagnetically coupled at the crossover part 26, to thereby excite a current flowing along the slot 23. As a result, compared to a case in which the slot 23 is not provided, an antenna gain may be improved. In addition, according to such a configuration, an operation at a predetermined frequency may be enabled regardless of the size of the slot between the conductive film and a flange of a vehicle body, and an antenna utilizing the conductive film may be realized without requiring accuracy in setting the glass plate to the flange of the vehicle body.
Next, a more detailed description will be given of the embodiment of the present invention. The vehicle window glass 100 illustrated in
An intermediate film 14A is arranged between the glass plate 11 and the conductive film 13, and an intermediate film 14B is arranged between the conductive film 13 and the glass plate 12. The glass plate 11 and the conductive film 13 are bonded by the intermediate film 14A, and the conductive film 13 and the glass plate 12 are bonded by the intermediate film 14B. The intermediate films 14A and 14B are formed from thermoplastic polyvinyl butyral, for example. A relative permittivity εr of the intermediate films 14A and 14B is 2.8 or higher and 3.0 or lower, which is the relative permittivity of a general intermediate film of laminated glass, for example.
The glass plates 11 and 12 are formed from a transparent plate-shaped dielectric. In addition, one of the glass plates 11 and 12 may be semitransparent, and both of the glass plates 11 and 12 may be semitransparent.
The conductive film 13 is a heat reflecting film capable of reflecting heat from the outside. The conductive film 13 may be transparent or semitransparent. For example, the conductive film 13 may be a conductive film formed on a surface of a film-shaped polyethylene terephthalate, or a conductive film formed on a surface of a glass plate, as illustrated in
The slot 23 is formed from the peripheral edge part 13a of the conductive film 13 towards the in-plane direction. The peripheral edge part 13a forms an outer peripheral edge of the conductive film 13. For example, the slot 23 may be formed by linearly cutting out the conductive film 13 from the open end 23a to a tip end (second end part) 23b.
In addition, the pair of electrodes 16 formed by the electrode 16A and the electrode 16B is arranged on the opposite side with respect to the position of the conductive film 13 via the glass plate 12. The electrodes 16 are exposed at the surface (that is, the surface on the opposite side with respect to the surface opposing the conductive film 13) on the vehicle interior side D2 of the glass plate 12, so that when the electrodes 16 are projected from the laminating direction, the projections 21 and 22 of the electrodes 16 are located at positions closer to the outer peripheral edge 11a of the glass plate 11 than the peripheral edge part 13a of the conductive film 13. The electrodes 16A and 16B are arranged side by side in a direction perpendicular to a longitudinal direction of the slot 23 and parallel to the surface of the glass plate 12. The positional relationship of the electrode 16A and the electrode 16B is not limited to the above. For example, the electrodes 16A and 16B may be arranged in an up and down direction (that is, the direction parallel to the longitudinal direction of the slot 23 in
Moreover, the loop-shaped antenna element 15 and the electrodes 16 are arranged on the same surface of the glass plate 12. The loop-shaped antenna element 15 is connected to the electrodes 16. In other words, the antenna conductor 17 forms a so-called loop antenna of dipole type together with the loop-shaped antenna element 15 and the electrodes 16 provided on the glass plate 12.
For example, in a case in which the electrode 16A is used as a signal line electrode and the electrode 16B is used as a ground line electrode, the electrode 16A is electrically connected to a signal line that is connected to a signal processing unit (for example, an amplifier and the like) that is mounted in the vehicle, and the electrode 16B is electrically connected to the ground line that is connected to a grounding part of the vehicle. For example, the grounding part may be the ground of the vehicle body, the ground of the signal processing unit to which the signal line connected to the electrode 16A connects, and the like. The electrode 16A may be used as the ground line electrode, and the electrode 16B may be used as the signal line electrode.
Reception signals of radio waves, corresponding to the current excited along the slot 23 and the current excited in the loop-shaped antenna element 15, are transmitted to the signal processing unit mounted in the vehicle via conductive members that are electrically connected to the pair of electrodes 16. Preferably, the conductive members are feeders, such as AV cables (low-voltage electric cables for automobiles) and coaxial cables.
In a case in which the coaxial cable is used as the feeders to feed to the antenna via the electrodes 16A and 16B, an inner conductor of the coaxial cable is electrically connected to the electrode 16A, and an outer conductor of the coaxial cable is electrically connected to the electrode 16B. In addition, a configuration may be employed in which connectors for electrically connecting the electrodes 16A and 16B to the conductive members, such as cables, that are connected to the signal processing unit, are mounted on the electrodes 16A and 16B. By use of such connectors, the mounting of the inner conductor of the coaxial cable to the electrode 16A is facilitated, and the mounting of the outer conductor of the coaxial cable to the electrode 16B is facilitated. Further, a configuration may be employed in which conductive members in the form of conductive projections are provided on the electrodes 16A and 16B, and the conductive projections fit into and make contact with feeding parts provided in a flange of the vehicle body to which the window glass 100 is mounted.
The shape of the electrode 16A and the electrode 16B and the separation between the electrodes 16A and 16B may be determined by taking into consideration the shapes of the conductive members or the connectors and the separation of the mounting surfaces. For example, a quadrate and a polygonal shape, such as a square shape, an approximately square shape, a rectangular shape, an approximately rectangular shape and the like, are preferable electrode shapes in view of mounting. Round shapes, such as a circular shape, an approximately circular shape, an oval shape, an approximately oval shape and the like are also preferable electrode shapes.
In addition, the antenna conductor 17, including the electrodes 16A and 16B and the loop-shaped antenna element 15, may be formed by printing and baking a paste that includes a conductive metal, for example a silver past, onto the surface of the glass plate 12 on the vehicle interior side D2. The method of forming the antenna conductor 17 is not limited to this method, and for example, a strips or films made of a conductive material such as copper and the like may be formed on the surface of the glass plate 12 on the vehicle interior side D2, and the conductive material may be adhered on the glass plate 12 by an adhesive or the like.
In addition, the antenna conductor 17 may be provided on a surface of a synthetic resin film, and the conductive film 13 formed with the slot 23 may be provided on the other surface of the synthetic resin film, in order to form a glass antenna. Moreover, a substrate such as a flexible substrate and the like may be used in place of the synthetic resin film. Such a glass antenna may be used by mounting the glass antenna on the surface of the glass plate 12 on the vehicle interior side D2 or on the vehicle exterior side D1.
Further, the position of the loop-shaped antenna element 15 on the glass plate is not limited to a particular position as long as the position is suited for receiving radio waves in a predetermined frequency band. For example, the antenna in the embodiment may be arranged in a vicinity of a vehicle body opening edge that is a mounting part to which the vehicle window glass is mounted. As illustrated in
The peripheral edge parts 13a through 13d forming the outer peripheral edges of the conductive film 13 are offset by the predetermined distance towards the inside from the outer peripheral edges 11a through 11d of the glass plate 11. By providing such an offset, the conductive film 13 may be prevented from corrosion caused by immersion and the like from matching surfaces of the glass plate 11 and the glass plate 12. In addition, in the example illustrated in
A concealing film may be formed on the glass plate 12, and a part or all of the antenna conductor 17 may be provided on this concealing film. Alternatively, a concealing film may be formed on the glass plate 11 in a region corresponding to a part or all of the antenna conductor 17. The part of the antenna conductor 17 is preferably a part of the loop-shaped antenna element 15 and the electrodes 16. For example, a ceramic film such as a black ceramic film and the like may be used as the concealing film. In this case, when viewed from the vehicle exterior side D1 of the vehicle window glass 200, the part of the antenna conductor provided on the concealing film is either not visible or difficult to identify due to the concealing film, to thereby improve the design of the window glass. In the example illustrated in
In the cases illustrated in
In addition, as illustrated in
As may be seen from
When a wavelength in air at a center frequency of the predetermined frequency band of the loop-shaped antenna element 15 is denoted by λ0, a shortening coefficient of wavelength for glass is denoted by k (where k=0.64), and λg=λ0·k, preferable results may be obtained from the point of view of improving the antenna gain in the predetermined frequency band when a loop length L1 of the loop-shaped antenna element 15 (=H1×2+W1×2) is λg or longer and (7/5)·λg or shorter. The loop length as used in the embodiments includes the separation between the electrodes 16A and 16B.
For example, in order to improve the antenna gain the predetermined frequency band having the center frequency of 310 MHz, and the velocity of the radio waves is 3.0×108 m/s, the loop length L1 of the loop-shaped antenna element 15 may be adjusted to 640 mm or longer and 900 mm or shorter.
In addition, when the slot length H2 from the crossover part 26 where the loop-shaped antenna element 15 and the slot 23 cross to the tip end 23b of the slot 23 is ( 3/16)·λg or longer and ( 5/16)·λg or shorter, preferable results may be obtained from the point of view of improving the antenna gain in the predetermined frequency band.
For example, in order to improve the antenna gain the predetermined frequency band having the center frequency of 310 MHz, and the velocity of the radio waves is 3.0×108 m/s, the slot length H2 may be adjusted to 120 mm or longer and 200 mm or shorter.
Numerical calculation was performed on a computer with respect to the antenna 19 of the embodiment illustrated in
In addition, dimensions of each of the other parts are set as follows, where the units of the values are in mm.
W1: 341.25
With respect to the antenna 19 set with these numerical values, an electromagnetic field simulation based on the FDTD method (Finite-Difference Time-Domain method) was made to perform numerical calculation of a return loss (reflection coefficient) (S11) for every 5 Hz in frequencies of 200 MHz to 400 MHz. The closer the S11 value is to zero the larger the return loss and the smaller the antenna gain, and the larger the negative value of the S11 the smaller the return loss and the larger the antenna gain.
As may be seen from a comparison of the simulation results for the case “a” and the case “b”, the provision of the conductive film 13 not formed with the slot 23 will not enable an antenna function. However, by providing the slot 23 that crosses the loop-shaped antenna element 15 with respect to the case “b”, the loop-shaped antenna element 15 and the slot 23 become electromagnetically coupled and a current may flow along the slot 23, to thereby enable satisfactory matching in a vicinity of 300 MHz as indicated in the case “c” and enable the antenna function.
Hence, according to the configuration described above, an antenna utilizing a conductive film may be configured without using a slot between a flange of a vehicle body and the conductive film. Because the flange of the vehicle body is not utilized, accuracy in setting a glass plate to the flange of the vehicle body may not be required. In addition, since it is unnecessary to form a hole in the glass plate and it is unnecessary to provide a feeding conductor that uses a detour route on an outer side of the outer peripheral edge of the glass plate, the antenna utilizing the conductive film may be realized with a simple configuration.
According to the embodiments, it is possible to realize an antenna utilizing a conductive film, that enables operation at a predetermined frequency regardless of the size of the slot between the conductive film and the flange of the vehicle body, and does not require accuracy in setting a glass plate to the flange of the vehicle body.
The embodiments may preferably be utilized as an antenna for an automobile to receive digital terrestrial television broadcasting, analog television broadcasting in the UHF band, digital television broadcasting in the United States, digital television broadcasting in the European Union states, or digital television broadcasting in the People's Republic of China, for example. Other usages of the antenna may include the FM broadcasting band (76 MHz to 90 MHz) in Japan, the FM broadcasting band (88 MHz to 108 MHz) in the U. S., television VHF bands (90 MHz to 108 MHz, 170 MHz to 222 MHz), or keyless entry system (300 MHz to 450 MHz) for vehicles, for example.
In addition, other usages may include communication in the 800 MHz band (810 MHz to 960 MHz) for mobile phones, the 1.5 GHz band (1.429 GHz to 1.501 GHz) for mobile phones, GPS (Global Positioning System) (the satellite GPS signal: 1575.42 MHz), and the VICS (registered trademark) (Vehicle Information and Communication System: 2.5 GHz).
Furthermore, other usages may include communication in the ETC (Electronic Toll Collection system: non-stop automatic toll collection system) communication (transmission frequency of road side wireless device: 5.795 GHz or 5.805 GHz, reception frequency of road side wireless device: 5.835 GHz or 5.845 GHz), the DSRC (Dedicated Short Range Communication, 915 MHz band, 5.8 GHz band, 60 GHz band), the microwave communication (1 GHz to 3 THz), the millimeter-wave communication (30 GHz to 300 GHz), and the SDARS (Satellite Digital Audio Radio Service, 2.34 GHz, 2.6 GHz).
The vehicle window glass and the antenna are described above with reference to the embodiments, however, it may be apparent to those skilled in the art that the present invention is not limited to the above embodiments, and various variations and modifications may be made without departing from the spirit and scope of the present invention.
Number | Date | Country | Kind |
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2010-267532 | Nov 2010 | JP | national |
This application is a continuation application filed under 35 U.S.C. 111(a) claiming the benefit under 35 U.S.C. 120 and 365(c) of a PCT International Application No. PCT/JP2011/077090 filed on Nov. 24, 2011, which is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2010-267532 filed on Nov. 30, 2010, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/JP2011/077090 | Nov 2011 | US |
Child | 13904589 | US |