ANTENNA

Abstract

 It is provided an antenna, which is to be disposed on a window glass, comprising a hot-side element (10) and a ground-side element (20). The hot-side element (10) extends substantially horizontally along the metal flange (1) in a direction separating from the hot-side feed point (3). The ground-side element (20) includes a ground-side first conductive line (21), and at least one of a ground-side second conductive line (22) and a ground-side third conductive line (23). The ground-side first conductive line (21) extends downward along the metal flange (1). The ground-side second conductive line (22) extends downward substantially in parallel to the ground-side first conductive line (21) closer to a center of the window glass than the ground-side first conductive line (21). The ground-side third conductive line (23) extends upward closer to the center of the window glass than the ground-side feed point (4) and the hot-side feed point (3).

Description

BACKGROUND OF THE INVENTION

[0001] This invention relates to an antenna device, and more particularly, to an antenna that is disposed on a car window glass and is suitable for receiving a digital terrestrial broadcasting wave.

[0002] Conventionally, an antenna disposed on a car window glass is widely proposed as a glass antenna for digital terrestrial broadcasting.

[0003] For instance, JP 2009-164678 A filed by this applicant proposes a line antenna for digital terrestrial broadcasting, which is disposed in a space above a defogger on a car rear window glass.

[0004] In addition, JP 2009-33687 A filed by this applicant as well proposes a line antenna for digital terrestrial broadcasting disposed in corner parts of a windshield (a front window glass), a car rear window glass, and a car side window glass.

SUMMARY OF THE INVENTION

[0005] However, the antenna described in JP 2009-164678 A is a line antenna disposed on the rear window glass where it is difficult to obtain high antenna performance because of an influence of the defogger. In order to obtain high antenna performance, the antenna may occupy a large area of approximately 50 and 100 mm, vertically and horizontally.

[0006] In addition, the antenna described in JP 2009-33687 A occupies a smaller area than the antenna described in JP 2009-164678 A. However, when the antenna is disposed on a usually black ceramic layer formed like a band on a periphery of the internal surface of the car window glass, the antenna cannot be covered with the ceramic layer. Therefore, the antenna is conspicuous when viewed from the outside of the car.

[0007] This invention has been made in view of the above-mentioned problems, and it is an object of this invention to provide an inconspicuous glass antenna by adopting a configuration in which the entire antenna can be easily covered with a black ceramic layer formed on a periphery of a vehicle window glass, while securing conventional or higher antenna reception performance for a digital terrestrial television broadcasting wave and a small occupying area.

[0008] The representative one of inventions is an antenna, which is to be disposed on a window glass, comprising a hot-side element (10), a ground-side element (20), a hot-side feed point (3), and a ground-side feed point (4), characterized in that: the hot-side feed point (3) and the ground-side feed point (4) are disposed side by side in a position close to an upper corner part of a metal flange (1) defining an opening of a window; the hot-side element (10) is connected to the hot-side feed point (3); the ground-side element (20) is connected to the ground-side feed point (4); the hot-side element (10) extends substantially horizontally along the metal flange (1) in a direction separating from the hot-side feed point (3); the ground-side element (20) includes a ground-side first conductive line (21), and at least one of a ground-side second conductive line (22) and a ground-side third conductive line (23); the ground-side first conductive line (21) is connected to the ground-side feed point (4) and extends downward along the metal flange (1); the ground-side second conductive line (22) is connected to the ground-side feed point (4) and extends downward substantially in parallel to the ground-side first conductive line (21) closer to a center of the window glass (2) than the ground-side first conductive line (21); the ground-side third conductive line (23) is connected to the ground-side feed point (4) and extends upward closer to the center of the window glass (2) than the ground-side feed point (4) and the hot-side feed point (3).

[0009] According to this invention, an antenna pattern can be reduced without deteriorating antenna performance.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] 

FIG. 1 is an enlarged elevation view illustrating an antenna pattern of Example 1 of this invention,

FIG. 2 is an enlarged elevation view illustrating an antenna pattern of Example 2 of this invention,

FIG. 3 is an enlarged elevation view illustrating an antenna pattern of Example 3 of this invention,

FIG. 4 is an enlarged elevation view illustrating an antenna pattern of Example 4 of this invention,

FIG. 5 is an enlarged elevation view illustrating an antenna pattern of Example 5 of this invention,

FIG. 6 is an enlarged elevation view illustrating an antenna pattern of Example 6 of this invention,

FIG. 7 is an enlarged elevation view illustrating an antenna pattern of Example 7 of this invention,

FIG. 8 is an enlarged elevation view illustrating an antenna pattern of Example 8 of this invention,

FIG. 9 is an enlarged elevation view illustrating an antenna pattern of a conventional example,

FIG. 10 is an overall view illustrating antennas of Example 1 disposed on a windshield of a car,

FIG. 11 is an overall view illustrating antennas of Example 7 disposed on a windshield of a car,

FIG. 12 is a frequency response diagram of Example 1 and the comparative example, and

FIG. 13 is a frequency response diagram of Example 7 and the comparative example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] This invention relates to a glass antenna disposed in a vicinity of an upper corner part of a windshield, which can receive a digital terrestrial television broadcasting wave having a frequency of approximately 470 to 710 MHz with high performance.

[0012] As illustrated in FIG. 1, the glass antenna of this invention is disposed in a vicinity of a corner part of a window glass 2 so that a hot-side feed point 3 and a ground-side feed point 4 are close to each other. The glass antenna is constituted of two elements including a hot-side element 10 connected to the hot-side feed point 3 and a ground-side element 20 connected to the ground-side feed point 4. The hot-side feed point 3 and the ground-side feed point 4 are connected to a core wire of a coaxial cable and an outer conductor of the coaxial cable, respectively.

[0013] The hot-side element 10 is constituted of a hot-side first conductive line 11 connected to the hot-side feed point 3 and a hot-side second conductive line 12 that is connected to a endpoint of the hot-side first conductive line 11 and extends along an upper part of a body flange 1 (in a horizontal direction parallel to the upper part of the body flange 1, for example). The hot-side first conductive line 11 extends upward diagonally toward a center conductive line of the window glass 2 but may extend approximately horizontally or approximately vertically upward. Further, it is possible to directly connect the hot-side second conductive line 12 to the hot-side feed point 3 without disposing the hot-side first conductive line 11 as illustrated in FIG. 7.

[0014] By appropriately adjusting an inclination and a length of the hot-side first conductive line 11, a length of the hot-side second conductive line 12 and an interval between the hot-side second conductive line 12 and the body flange 1 can be adjusted so that good reception performance can be obtained.

[0015] According to an experiment by the inventors, good reception performance can be obtained if the sum of lengths of the hot-side first conductive line 11 and the hot-side second conductive line 12 is α·λ/6 to α·λ/2 (α represents a wavelength reduction ratio of the glass, and λ represents a wavelength of the center frequency of the received radio wave) and the interval between the hot-side second conductive line and the upper part of the body flange 1 is 10 to 25 mm.

[0016] The ground-side element 20 is constituted of a ground-side first conductive line 21, a ground-side second conductive line, and a ground-side third conductive line. The ground-side second conductive line has an L-shape formed by a downward conductive line 22 of the ground-side second conductive line and a connection line 24. The ground-side third conductive line has an L-shape formed by an upward conductive line 23 of the ground-side third conductive line and the connection line 24. Each of the ground-side first conductive line, the ground-side second conductive line, and the ground-side third conductive line is connected to the ground-side feed point 4.

[0017] It should be noted that the connection line may be the single conductive line 24 shared by the ground-side second conductive line and the ground-side third conductive line as illustrated in FIG. 1. Alternatively, as illustrated in FIG. 8, the connection line 24 of the ground-side second conductive line and a connection line 25 of the ground-side third conductive line may be disposed separately.

[0018] The ground-side first conductive line 21 extends from the ground-side feed point 4 along a side part of the body flange 1 (for example, downward in the vertical direction in parallel to the side part of the body flange 1). By changing at least one of a length of the ground-side first conductive line 21 and an interval between the ground-side first conductive line 21 and the side part of the body flange 1, the capacitance between the ground-side first conductive line 21 and the body flange 1 can be adjusted so that good reception performance can be obtained.

[0019] For instance, by adjusting the length of the ground-side first conductive line 21 to be α·λ/4 to α·λ/2 (λ represents a wavelength of the center frequency of the reception band) and by adjusting the interval between the ground-side first conductive line 21 and the side part of the body flange 1 to be 5 to 75 mm, good reception performance can be obtained.

[0020] The downward conductive line 22 of the ground-side second conductive line is disposed in parallel to the ground-side first conductive line 21. By setting a length of the ground-side second conductive line to be α·λ/20 to α·λ/2 (λ represents a wavelength of the center frequency of the reception band), the ground-side second conductive line is strongly coupled to the ground-side first conductive line in an electrical manner. Then, it is possible to obtain the same effect as if a width of the ground-side first conductive line were increased, and hence antenna reception performance can be improved.

[0021] However, it is preferred that an interval A between the ground-side first conductive line 21 and the downward conductive line 22 of the ground-side second conductive line be α·λ/50 to α·λ/10. This is because if the interval A is larger than this range, the electrical coupling between the ground-side second conductive line and the ground-side first conductive line is weakened, and hence the optimal impedance cannot be obtained.

[0022] The antenna impedance of the ground-side third conductive line can be adjusted by adjusting a length thereof. Then, this impedance adjustment can provide a wide-band antenna. For instance, by adjusting a length of the ground-side third conductive line to be α·λ/20 to α·λ/5 (λ represents a wavelength of the center frequency of the reception band), good antenna performance can be obtained.

[0023] It is preferred that an interval B between the hot-side feed point 3 and the ground-side third conductive line be α·λ/50 or larger. It is because if the interval B is smaller than α·λ/50, electrical coupling between the ground-side third conductive line and the hot-side feed point 3 increases, and hence antenna performance is deteriorated.

[0024] In FIG. 1, the ground-side element 20 is constituted of three conductive lines including the ground-side first conductive line 21, the ground-side second conductive line, and the ground-side third conductive line. However, as illustrated in FIGS. 2, 4, and 6, the ground-side element 20 may be constituted of only the ground-side first conductive line and the ground-side third conductive line without the ground-side second conductive line. In addition, as illustrated in FIGS. 5 and 7, the ground-side element 20 may be constituted of only the ground-side first conductive line and the ground-side second conductive line without the ground-side third conductive line.

[0025] Further, the ground-side element 20 may be constituted of the ground-side first conductive line, the ground-side second conductive line, and the ground-side third conductive line. In this case, the ground-side second conductive line is directly connected to the ground-side feed point 4.

[0026] In addition, in FIG. 1, the ground-side second conductive line and the ground-side third conductive line share the entire connection line 24. However, as illustrated in FIG. 3, the downward conductive line 22 of the ground-side second conductive line may be connected to a midpoint of the connection line 24, and the upward conductive line 23 of the ground-side third conductive line may be connected to a endpoint of the connection line 24, so as to share a part of the connection line 24. Alternatively, it is possible to connect the downward conductive line 22 of the ground-side second conductive line to the endpoint of the connection line 24, and to connect the upward conductive line 23 of the ground-side third conductive line to a midpoint of the connection line 24.

[0027] In FIGS. 1 and 3, the ground-side second conductive line and the ground-side third conductive line share the connection line 24. However, it is possible to dispose a connection line for the ground-side second conductive line and a connection line for the ground-side third conductive line separately, and to extend the ground-side second conductive line and the ground-side third conductive line separately from the ground-side feed point 4 without a shared part.

[0028] In addition, as illustrated in FIGS. 4 and 5, besides the hot-side second conductive line 12, a hot-side third conductive line 13 substantially parallel to the hot-side second conductive line 12 may be disposed to the hot-side element 10. Specifically, the hot-side third conductive line 13 is constituted of a substantially horizontal conductive line 13a and a substantially vertical conductive line 13b.

[0029] The hot-side third conductive line 13 is an element disposed mainly for impedance adjustment. By setting a length of the hot-side third conductive line to be α·λ/6 or smaller, good antenna performance can be obtained.

[0030] In addition, the hot-side third conductive line 13 can be connected to any position of the hot-side first conductive line 11 and the hot-side second conductive line 12. For instance, in the antenna illustrated in FIG. 4, an end of the substantially vertical conductive line 13b is connected to a endpoint of the hot-side first conductive line 11. In addition, in the antenna illustrated in FIG. 5, an end of the substantially vertical conductive line 13b is directly connected to the hot-side feed point 3.

[0031] Further, the hot-side third conductive line 13 may be constituted of only the substantially horizontal conductive line 13a, and the substantially horizontal conductive line 13a may be directly connected to the hot-side feed point 3.

[0032] In addition, as illustrated in FIG. 6, instead of the hot-side third conductive line 13 substantially parallel to the hot-side second conductive line 12, a hot-side fourth conductive line 14 extending in a different direction from the hot-side second conductive line 12 may be used to constitute the hot-side element 10. In this case, the hot-side fourth conductive line 14 is directly connected to the hot-side feed point 3.

[0033] The hot-side fourth conductive line 14 is constituted of a lateral conductive line 14b connected to the hot-side feed point 3 and a downward conductive line 14a connected to a endpoint of the lateral conductive line 14b. The downward conductive line 14b is disposed in parallel and close to the upward conductive line 23 of the ground-side third conductive line so as to make capacitive coupling with the upward conductive line 23 in an electrical manner. By adjusting an interval between the hot-side fourth conductive line 14 and the upward conductive line 23 of the ground-side third conductive line, and by adjusting a length of the hot-side fourth conductive line, good antenna performance can be obtained. For instance, if a length of the hot-side fourth conductive line is α·λ/50 to α·λ/10 (λ represents a wavelength of the center frequency of the reception band), good antenna performance can be obtained.

[0034] In addition, the antenna of an embodiment of this invention may be an antenna for performing diversity reception in which the antenna pattern is arranged at left and right symmetric positions on the windshield to be symmetric with respect to the center line of the windshield as illustrated in FIG. 10.

[0035] The antenna of this embodiment is formed by printing each conductive line to have a width of 0.7 mm with conductive ceramic paste at predetermined positions on the internal surface of the window glass 2, drying, and burning in a heating furnace. However, the antenna pattern may be formed on a surface of other insulator. In addition, the antenna may be attached to a window glass, a wall, or a roof of a building. Further, it is possible to directly print the antenna pattern on a surface of a vehicle window glass 2 or to form the antenna pattern on a sheet made of a synthetic resin for adhering to a desired position on the window glass 2.

[0036] Further, the core wire of the coaxial cable (not shown) extending from a tuner (not shown) is connected to the hot-side feed point 3, and the outer conductor of the coaxial cable is connected to the ground-side feed point 4.

[0037] According to the antenna of this embodiment, the antenna pattern can be downsized without deteriorating the antenna performance. Therefore, it is possible to cover the most part of the antenna pattern with the black ceramic layer formed in a periphery of the windshield so as to arrange the glass antenna to be inconspicuous and not to be an obstacle in the field of view. In addition, the pattern of the glass antenna becomes simple, and hence the development man-hour for tuning can be reduced.

[0038] Various examples of this invention are now described.

<Example 1>

[0039] FIG. 1 illustrates an antenna pattern of Example 1 of this invention, and is a front enlarged view of the glass antenna disposed in a vicinity of an upper corner part of a car windshield.

[0040] In the antenna of Example 1, the hot-side feed point 3 and the ground-side feed point 4 are disposed close to each other in an upper and lower direction so as to be close to the upper corner part of the windshield. The hot-side feed point 3 is connected to the hot-side element 10, and the ground-side feed point 4 is connected to the ground-side element 20.

[0041] The hot-side element 10 is constituted of the hot-side first conductive line 11 that is connected to the hot-side feed point 3 and extends diagonally upward, and the hot-side second conductive line 12 that is connected to the endpoint of the hot-side first conductive line 11 and extends in parallel to the upper part of the body flange 1.

[0042] The ground-side element 20 is constituted of the ground-side first conductive line 21, the downward conductive line 22 of the ground-side second conductive line, the upward conductive line 23 of the ground-side third conductive line, and the connection line 24 shared by the ground-side second conductive line and the ground-side third conductive line.

[0043] The ground-side first conductive line 21 is a conductive line that extends in parallel to the side part of the body flange 1, has an end connected to the ground-side feed point 4, and extends downward from the ground-side feed point 4.

[0044] The ground-side second conductive line is an L-shaped line constituted of the connection line 24 that has an end connected to the ground-side feed point 4 and extends in the direction toward the center line of the window glass 2, and the downward conductive line 22 extending downward from the endpoint of the connection line 24 in parallel to the ground-side first conductive line.

[0045] Further, the ground-side third conductive line is an L-shaped conductive line constituted of the connection line 24 and the upward conductive line 23 extending upward from the endpoint of the connection line 24.

[0046] As illustrated in FIG. 1, lengths of the each of the conductive lines of the antenna of this example are as follows. A length of the hot-side first conductive line 11 is 20 mm, a length of the hot-side second conductive line 12 is 50 mm, and a length of the ground-side first conductive line 21 is 100 mm. A length of the connection line 24 is 5 mm, a length of the downward conductive line 22 of the ground-side second conductive line is 80 mm, and a length of the upward conductive line 23 of the ground-side third conductive line is 40 mm.

[0047] In addition, an interval between the hot-side second conductive line 12 and the upper part of the body flange 1 is 15 mm, and an interval between the ground-side first conductive line 21 and the side part of the body flange 1 is 15 mm.

[0048] In addition, the hot-side feed point 3 and the ground-side feed point 4 each have a solid pattern of a square of 10 mm each side, and are respectively connected to a hot-side terminal and a ground-side terminal of a feed terminal (not shown). Further, an interval between the body flange 1 and a vertex of the hot-side feed point 3 closest to the body flange 1 is 6 mm, and an interval between the hot-side feed point 3 and the ground-side feed point 4 is 20 mm.

[0049] In the glass antenna of this example, a wavelength reduction ratio α of the glass is regarded to be 0.7, and sizes of the individual elements are adjusted so as to match a frequency (620 MHz) in a vicinity of the center frequency of the digital terrestrial broadcasting. The size of the antenna is not limited to the above-mentioned size.

[0050] Performance of the antenna of this example can be understood from comparison shown in FIG. 12 between a frequency response diagram of the antenna of Example 1 and a frequency characteristic diagram of the antenna of a comparative example of FIG. 9 described later (a solid line indicates Example 1, and a broken line indicates the comparative example). FIG. 12 is a result of measurement in which the antenna of Example 1 and the antenna of the comparative example were disposed on the windshield 2 of a vehicle. As understood from FIG. 12, the antenna of Example 1 can provide higher performance than the antenna of the comparative example in substantially all frequencies in the frequency band of 470 MHz to 710 MHz for digital terrestrial broadcasting.

[0051] FIG. 10 illustrates two antennas of Example 1 disposed at upper corner parts of the windshield 2. As illustrated in FIG. 10, because two antennas perform diversity reception, higher reception performance can be obtained than in the case where only a single antenna pattern is disposed.

<Example 2>

[0052] FIG. 2 illustrates an antenna pattern of Example 2 of this invention, and is a front enlarged view of the glass antenna disposed in the vicinity of the upper corner part of the windshield.

[0053] The antenna of Example 2 is different from the antenna of Example 1 in that the ground-side second conductive line is not disposed, and is the same as the antenna of Example 1 in other points. Therefore, the same component as Example 1 is denoted by the same reference numeral, and overlapping description thereof is omitted.

<Example 3>

[0054] FIG. 3 illustrates an antenna pattern of Example 3 of this invention, and is a front enlarged view of the glass antenna disposed in the vicinity of the upper corner part of the windshield.

[0055] The antenna of Example 3 is different in configuration from the antenna of Example 1 in that the upward conductive line 23 of the ground-side third conductive line is connected to the endpoint of the connection line 24, and that the downward conductive line 22 of the ground-side second conductive line is connected to a midpoint of the connection line 24. In other words, in the antenna of Example 3, the ground-side second conductive line and the ground-side third conductive line share only a part of the connection line 24.

[0056] In the antenna of Example 3, a length the upward conductive line 23 of the ground-side third conductive line and a length of the connection line 24 are changed from those of the antenna of Example 1, so as to obtain good antenna performance. Lengths of other conductive lines are the same as those of the antenna of Example 1. Therefore, the same component as Example 1 is denoted by the same reference numeral, and overlapping description thereof is omitted.

<Example 4>

[0057] FIG. 4 illustrates an antenna pattern of Example 4 of this invention, and is a front enlarged view of the glass antenna disposed in the vicinity of the upper corner part of the windshield.

[0058] The antenna of Example 4 is different from the antenna of Example 2 in that the hot-side third conductive line 13 is further connected to a junction of the hot-side first conductive line and the hot-side second conductive line. Other points are the same as those of the antenna of Example 2. Therefore, the same component as Example 1 is denoted by the same reference numeral, and overlapping description thereof is omitted.

[0059] The hot-side third conductive line 13 is constituted of the substantially vertical conductive line 13b extending downward from the junction of the hot-side first conductive line and the hot-side second conductive line, and the substantially horizontal conductive line 13a that is connected to a endpoint of the substantially vertical conductive line 13b and extends in the direction toward the center conductive line of the window glass 2.

[0060] In this antenna, if a length of the hot-side third conductive line 13 is set to be 40 mm, the impedance is reduced so that good antenna performance is obtained. Depending on a junction position of the hot-side third conductive line 13 and the hot-side first conductive line 11 as well as the hot-side second conductive line 12, the antenna impedance changes. Therefore, the length of the hot-side third conductive line 13 may be adjusted so that good antenna performance can be obtained.

<Example 5>

[0061] FIG. 5 illustrates an antenna pattern of Example 5 of this invention, and is a front enlarged view of the glass antenna disposed in the vicinity of the upper corner part of the windshield.

[0062] The antenna of Example 5 is different from the antenna of Example 1 in that the hot-side third conductive line 13 is connected to the hot-side feed point 3, and that the ground-side third conductive line from the ground-side element 20 is not disposed. Other points are the same as those of the antenna of Example 1. Therefore, the same component as Example 1 is denoted by the same reference numeral, and overlapping description thereof is omitted.

[0063] In the antenna of this example, by adjusting the length of the hot-side third conductive line 13, the impedance can be adjusted so that good antenna performance can be obtained.

<Example 6>

[0064] FIG. 6 illustrates an antenna pattern of Example 6 of this invention, and is a front enlarged view of the glass antenna disposed in the vicinity of the upper corner part of the windshield.

[0065] The antenna of Example 6 is different from the antenna of Example 2 in that the hot-side fourth conductive line 14 is disposed, and is the same as the antenna of Example 2 in other points. Therefore, the same component as Example 2 is denoted by the same reference numeral, and overlapping description thereof is omitted.

[0066] The hot-side fourth conductive line 14 is constituted of the lateral conductive line 14b that is connected to the hot-side feed point 3 and extends in the direction toward the center conductive line of the window glass 2, and the downward conductive line 14b that is connected to the endpoint of the lateral conductive line 14b and extends downward so as to be close and in parallel to the upward conductive line of the ground-side third conductive line.

[0067] In the antenna of this example, a size of the ground-side third conductive line is adjusted and changed from that of Example 2 so that good antenna performance can be obtained. Lengths of other conductive lines are the same as those of the antenna of Example 2.

<Example 7>

[0068] FIG. 7 illustrates an antenna pattern of Example 7 of this invention, and is a front enlarged view of the glass antenna disposed in the vicinity of the upper corner part of the windshield.

[0069] The antenna of Example 7 is different from the antenna of Example 5 in that the hot-side second conductive line is directly connected to the hot-side feed point 3 without the hot-side first conductive line 11 and the hot-side third conductive line 13. Other points are the same as those of the antenna of Example 5. Therefore, the same component as Example 5 is denoted by the same reference numeral, and overlapping description thereof is omitted.

[0070] As illustrated in FIG. 7, lengths of conductive lines of the antenna of this example are as follows. A length of the hot-side second conductive line is 50 mm, a length of the ground-side first conductive line 21 is 110 mm, a length of the connection line 24 of the ground-side second conductive line is 20 mm, and a length of the downward conductive line 22 of the ground-side second conductive line is 85 mm.

[0071] In addition, the interval between the hot-side second conductive line 12 and the upper part of the body flange 1 is 15 mm, and the interval between the ground-side first conductive line 21 and the side part of the body flange 1 is 15 mm.

[0072] In addition, the hot-side feed point 3 and the ground-side feed point 4 each have a solid pattern of a square of 10 mm each side, and are respectively connected to the hot-side terminal and the ground-side terminal of the feed terminal (not shown). Further, the interval between the body flange 1 and a vertex of the hot-side feed point 3 closest to the body flange 1 is 6 mm, and the interval between the hot-side feed point 3 and the ground-side feed point 4 is 20 mm.

<Example 8>

[0073] FIG. 8 illustrates an antenna pattern of Example 8 of this invention, and is a front enlarged view of the glass antenna disposed in the vicinity of the upper corner part of the windshield.

[0074] The antenna of Example 8 is different from the antenna of Example 1 in that the connection line 24 is not shared by the ground-side second conductive line and the ground-side third conductive line. Other points are the same as those of the antenna of Example 1. Therefore, the same component as Example 1 is denoted by the same reference numeral, and overlapping description thereof is omitted.

[0075] The ground-side element 20 is constituted of the ground-side first conductive line 21, the ground-side second conductive line, and the ground-side third conductive line. The ground-side second conductive line is constituted of the connection line 24 connected to the ground-side feed point 4, and the downward conductive line 22 connected to the endpoint of the connection line 24. The ground-side third conductive line is constituted of the connection line 25 connected to the ground-side feed point 4, and the upward conductive line 23 connected to a endpoint of the connection line 25.

[0076] It should be noted that the downward conductive line 22 may be connected to a midpoint of the connection line 24 instead of the endpoint of the connection line 24. Further, the upward conductive line 23 may be connected to a midpoint of the connection line 25 instead of the endpoint of the connection line 25.

[0077] In the glass antenna of this example, a wavelength reduction ratio α of the glass is regarded to be 0.7, and sizes of the individual elements are adjusted so as to match a frequency (620 MHz) in a vicinity of the center frequency of the digital terrestrial broadcasting. The size of the antenna is not limited to the above-mentioned size.

[0078] Performance of the antenna of this example can be understood from comparison shown in FIG. 13 between a frequency characteristic diagram of the antenna of Example 7 and a frequency characteristic diagram of the antenna of the comparative example of FIG. 9 described later (a solid conductive line indicates Example 7, and a broken conductive line indicates the comparative example). FIG. 13 is a result of measurement in which the antenna of Example 7 and the antenna of the comparative example were disposed on the windshield 2 of a vehicle. As understood from FIG. 13, the antenna of Example 7 can provide higher performance than the antenna of the comparative example in substantially all frequencies in the frequency band of 470 MHz to 710 MHz for digital terrestrial broadcasting.

[0079] FIG. 11 illustrates two antennas of Example 7 disposed at upper corner parts of the windshield 2. As illustrated in FIG. 11, because the two antennas perform diversity reception, higher reception performance can be obtained than in the case where only a single antenna is disposed.

<Comparative example>

[0080] FIG. 9 illustrates an antenna pattern of the comparative example to be compared with the antenna of this invention, and is a front enlarged view of the glass antenna disposed in the vicinity of the upper corner part of the windshield.

[0081] The antenna of the comparative example is based on the antenna described in JP 2009-33687 A. In the antenna pattern, a wavelength reduction ratio α of the glass is regarded to be 0.7, and lengths of individual elements are adjusted so as to match a frequency (620 MHz) in a vicinity of the center frequency of the digital terrestrial broadcasting.

[0082] In the antenna of this comparative example, the hot-side feed point 3 and the ground-side feed point 4 are disposed close to each other in the upper and lower direction so as to be close to the upper corner part of the windshield. The hot-side element 10 is connected to the hot-side feed point 3, and the ground-side element 20 is connected to the ground-side feed point 4.

[0083] The hot-side element 10 is constituted of the hot-side first conductive line 11 that is connected to the hot-side feed point 3 and extends diagonally upward, the hot-side second conductive line 12 that is connected to the endpoint of the hot-side first conductive line 11 and extends in parallel to the upper part of the body flange 1, a hot-side fifth conductive line that is connected to the hot-side feed point 3 and extends downward, and a hot-side sixth conductive line that is connected to a endpoint of the hot-side fifth conductive line and extends in a horizontal direction.

[0084] In addition, the ground-side element 20 is constituted of only the ground-side first conductive line 21 that is connected to the ground-side feed point 4 and extends downward to be vertical to the side part of the body flange 1.

[0085] The antenna of the examples of this invention is different from the antenna of the comparative example in that the ground-side element of the former antenna is connected to at least one of the ground-side second conductive line and the ground-side third conductive line for impedance adjustment, while the ground-side element of the latter antenna is not connected to a line for impedance adjustment.

Claims

1. An antenna, which is to be disposed on a window glass, comprising a hot-side element (10), a ground-side element (20), a hot-side feed point (3), and a ground-side feed point (4),
characterized in that:

the hot-side feed point (3) and the ground-side feed point (4) are disposed side by side in a position close to an upper corner part of a metal flange (1) defining an opening of a window;

the hot-side element (10) is connected to the hot-side feed point (3);

the ground-side element (20) is connected to the ground-side feed point (4);

the hot-side element (10) extends substantially horizontally along the metal flange (1) in a direction separating from the hot-side feed point (3);

the ground-side element (20) includes a ground-side first conductive line (21), and at least one of a ground-side second conductive line (22) and a ground-side third conductive line (23);

the ground-side first conductive line (21) is connected to the ground-side feed point (4) and extends downward along the metal flange (1);

the ground-side second conductive line (22) is connected to the ground-side feed point (4) and extends downward substantially in parallel to the ground-side first conductive line (21) closer to a center of the window glass (2) than the ground-side first conductive line (21); and

the ground-side third conductive line (23) is connected to the ground-side feed point (4) and extends upward closer to the center of the window glass (2) than the ground-side feed point (4) and the hot-side feed point (3).

2. The antenna according to claim 1, wherein:

the ground-side second conductive line (22) has an L-shape formed by a connection line (24) connected to the ground-side feed point (4) and a conductive line (22) that is connected to one of a endpoint and a midpoint of the connection line (24) and extends downward; and

the ground-side third conductive line (23) has an L-shape formed by the connection line (24) and a conductive line (23) that is connected to one of the endpoint and the midpoint of the connection line (24) and extends upward.

3. The antenna according to claim 1, wherein:

the ground-side second conductive line (22) has an L-shape formed by a first connection line (24) connected to the ground-side feed point (4)and a conductive line (22) that is connected to one of a endpoint and a midpoint of the first connection line (24) and extends downward; and

the ground-side third conductive line (23) has an L-shape formed by a second connection line (25) connected to the ground-side feed point (4) and a conductive line (23) that is connected to one of a endpoint and a midpoint of the second connection line (25) and extends upward.

4. The antenna according to claim 1, wherein each of the hot-side feed point (3) and the ground-side feed point (4) is disposed at a position separated from the metal flange (1) by 5 mm or larger.

5. The antenna according to claim 1, wherein:

the hot-side element (10) includes:

a hot-side first conductive line (11) that is connected to the hot-side feed point (3) and extends in a direction toward a center line of the window glass (2); and

a hot-side second conductive line (12) that is connected to a endpoint of the hot-side first conductive line (11) and extends substantially horizontally along the metal flange (1) in the direction separating from the hot-side feed point (3); and

the hot-side first conductive line (11) is disposed at a position where an interval between the hot-side first conductive line (11) and an upper part of the metal flange (1) is 10 to 25 mm.

6. The antenna according to claim 5, wherein a sum of a length of the hot-side first conductive line (11) and a length of the hot-side second conductive line (12) is α·λ/6 to α·λ/2, where α represents a wavelength reduction ratio of the window glass (2), and λ represents a center frequency of a received radio wave.

7. The antenna according to claim 1, wherein the ground-side first conductive line (21) is disposed at a position where an interval between the ground-side first conductive line (21) and a side part of the metal flange (1) is 15 mm or larger.

8. The antenna according to claim 1, wherein:

the hot-side element includes a hot-side third conductive line (13); and

the hot-side third conductive line (13) includes only a substantially horizontally part that is connected to one of the hot-side feed point (3), the hot-side first conductive line (11), and the hot-side second conductive line (12), and extends in the direction separating from the hot-side feed point (3), and otherwise the hot-side third conductive line (13) includes a substantially vertical part (13b) that is connected to one of the hot-side feed point (3), the hot-side first conductive line (11), and the hot-side second conductive line (12), and a substantially horizontally part (13a) that is connected to a endpoint of the substantially vertical part (13b) and extends in the direction separating from the hot-side feed point (3).

9. The antenna according to claim 8, wherein a length of the hot-side third conductive line (10) is α·λ/6 or smaller, where α represents a wavelength reduction ratio of the window glass (2), and λ represents a center frequency of a received radio wave.

10. The antenna according to claim 1, wherein:

the hot-side element (10) includes a hot-side fourth conductive line (14); and

the hot-side fourth conductive line (14) is connected to the hot-side feed point (3) and is disposed close to the ground-side third conductive line (23).

11. The antenna according to claim 10, wherein a length of the hot-side fourth conductive line (24) is α·λ/50 to α·λ/10, where α represents a wavelength reduction ratio of the window glass (2), and λ represents a center frequency of a received radio wave.

12. The antenna according to claim 1, wherein:

a length of the ground-side first conductive line (21) is α·λ/4 to α·λ/2;

a length of the ground-side second conductive line (22) is α·λ/20 to α·λ/2;

a length of the ground-side third conductive line (23) is α·λ/20 to α·λ/5;

an interval between the ground-side first conductive line (21) and the ground-side second conductive line (22) is α·λ/50 to α·λ/10; and

an interval between the ground-side third conductive line (23) and the hot-side feed point (3) in a vertical direction with respect to the ground-side third conductive line (23) is α·λ/50 to α·λ/10,

where α represents a wavelength reduction ratio of the window glass (2), and λ represents a center frequency of a received radio wave.

Drawing