1. Field of the Invention
The present invention relates to a planar antenna, and in particular, relates to a planar antenna, which is appropriate to radio wave communication using a frequency from about 1 to about 30 GHz, in particular from about 1 to about 6 GHz, and which is appropriate to a glass antenna for vehicles. The present invention also relates to a window glass sheet for automobiles, which includes such a planar antenna.
2. Discussion of Background
The GPS (Global Positioning System), the ETC (Electric Toll Collection System) and other systems have been recently employed to communicate between an in-vehicle communication device and an external communication device by a radio wave in order to make vehicles run smoother.
For example, it may be considered that an in-vehicle antenna as shown in
However, this prior art discloses only two modes of provision of the paired linear conductors and provision of an annular conductor. This prior art is silent on the length of the linear conductors. Since this prior art is also silent on how to dispose the linear conductors in other kinds of antennas, there has been a problem that it is difficult to apply the prior art to other kinds of antennas.
When this prior art is applied to a window glass sheet of an automobile as a high frequency antenna, a radio wave, which is transmitted on the window glass sheet, cannot be blocked or reflected in a sufficient way, with the result that interference is caused between the antenna and a portion of the automobile body in the vicinity of the window glass sheet. As a result, plural null points are generated, causing a problem in that the directivity greatly varies from portion to portion.
It is an object of the present invention to provide a planar antenna, which is capable of solving the above-mentioned problems of the prior art.
The present invention provides a planar antenna comprising:
a dielectric substrate having an antenna conductor disposed thereon or therein, the antenna conductor comprising a monopole antenna; and
two conductors, each of which is spaced from the antenna conductor by a distance, and which are called independent conductor A and independent conductor B, respectively;
wherein when an imaginary straight line, which passes through the center of gravity of the antenna conductor or the center of the antenna conductor and extends in parallel with a longitudinal direction of the antenna conductor, is called an endless transverse line;
the antenna conductor is formed in such a shape and a size to have an antenna gain in the longitudinal direction;
independent conductor A is disposed on one of both sides of the antenna conductor, and independent conductor B is disposed on the other side of the antenna conductor; and
independent conductor A and independent conductor B are disposed on or in the dielectric substrate so that the endless transverse line passes through independent conductor A and independent conductor B or extends over or under independent conductor A and independent conductor B.
The present invention also provides a planar antenna comprising:
a dielectric substrate having a first antenna wire and a second antenna wire disposed thereon or therein so as to be close to each other, each of the first antenna wire and the second antenna wire being formed in a loop shape; and
two conductors, each of which is spaced from the first antenna wire and the second antenna wire by a distance, and which are called independent conductor A and independent conductor B, respectively;
wherein when it is assumed that there is a first imaginary straight line connecting between the center of gravity of the first antenna wire and the center of gravity of the second antenna wire or connecting between the center of the first antenna wire and the center of the second antenna wire, the first imaginary straight line is called a transverse line, and when it is assumed that there is a second imaginary line obtained by endlessly extending the transverse line, the second imaginary line is called an endless transverse line;
when the center between closest portions of the first antenna wire and the second antenna wire is called an antenna center,
independent conductor A is disposed on a side closer to the first antenna wire with respect to the antenna center;
independent conductor B is disposed on a side closer to the second antenna wire with respect to the antenna center; and
independent conductor A and independent conductor B are disposed on or in the dielectric substrate so that the endless transverse line passes through independent conductor A and independent conductor B or extends over or under independent conductor A and independent conductor B.
The present invention also provides a planar antenna comprising:
a window glass sheet having a first antenna wire and a second antenna wire disposed thereon or therein so as to be close to each other, each of the first antenna wire and the second antenna wire being formed in a loop shape and being disposed in the vicinity of a vehicle opening edge for a window;
wherein when it is assumed that there is an imaginary straight line connecting between the center of gravity of the first antenna wire and the center of gravity of the second antenna wire or connecting between the center of the first antenna wire and the center of the second antenna wire, the imaginary straight line is called a transverse line;
the window glass sheet has independent conductor C disposed thereon or therein; independent conductor C is formed in a shape having a longitudinal direction; and independent conductor C, the first antenna wire and the second antenna wire are disposed so that each of the longitudinal direction of independent conductor C and the transverse line extends in parallel or substantially parallel with the vehicle opening edge for a window and that the first antenna wire and the second antenna wire are disposed between independent conductor C and the vehicle opening edge for a window.
The present invention also provides a window glass sheet for an automobile, comprising a dielectric substrate, the dielectric substrate having the above-mentioned planar antenna disposed thereon or therein.
The present invention is advantageous in terms of antenna gain as an antenna for a circularly-polarized wave because of adopting the above-mentioned structure. The present invention is also advantageous in terms of axial ratio and non-directivity and can make the planar antenna compact. When the present invention is applied to a window glass sheet for an automobile, the present invention is advantageous in terms of insuring sight and is also advantageous in terms of reduced cost and productivity. The present invention is also applicable to an antenna for a vertically polarized wave or a horizontally polarized wave.
An electric field is generated from an end portion or a curved portion of the antenna conductor and an antenna wire or the like, and it is supposed that the electric field propagates in such a direction that the endless transverse line extents.
For this point of view, when independent conductor A and independent conductor B are disposed on the dielectric substrate, it is supposed that it is possible to prevent interference from being caused between a metal body existing in the vicinity of the dielectric substrate and the antenna conductor or an antenna wire. When independent conductor A and independent conductor B are disposed on an automobile window glass sheet, it is supposed that it is possible to prevent interference from being caused between a portion of the car body in the vicinity of the window glass sheet and the antenna conductor or an antenna wire.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
Now, the planar antenna according to the present invention will be described in detail based on preferred embodiments, which are shown in the accompanying drawings.
In
In the embodiment shown in
Provided that the window glass sheet 9 comprises a vehicle window glass sheet in the embodiment shown in
In the embodiment shown in
It is preferred from the viewpoint of improving a communication property that the first antenna wire 10 and the second antenna wire 20 be formed in the same shape or substantially the same shape as or in a similar shape to each other except for the directions to dispose both antenna wires on the window glass sheet 9. This is also applicable to the embodiment shown in
The paired coupling branch lines 1 and 2 form a first capacitive coupling wire, and the paired coupling branch lines 11 and 12 form a second capacitive coupling wire. The first capacitive coupling wire and the second capacitive coupling wire are disposed as required. When it is assumed that there is a first imaginary straight line connecting between the center of gravity of the first antenna wire 10 and the center of gravity of the second antenna wire 20, or when it is assumed that there is a first imaginary straight line connecting between the center of the first antenna wire 10 and the center of the second antenna wire 20, this first imaginary straight line is called the transverse line 8. When it is assumed that there is a second imaginary straight line obtained by endlessly extending the transverse line 8, this second imaginary straight line is called the endless transverse line 8a.
The center between the closest portions of the first antenna wire 10 and the second antenna wire 20 is called an antenna center. Independent conductor A is disposed on a side close to the first antenna conductor 10 with respect to the antenna center. Independent conductor B is disposed on a side close to the second antenna wire with respect to the antenna center.
Independent conductor A and independent conductor B are disposed on the window glass sheet 9 so that the endless transverse line 8a passes through independent conductor A and independent conductor B or extends over or under independent conductor A and independent conductor B. In the embodiment shown in
In the embodiment shown in
In the embodiment shown in
In the embodiment shown in
Although each of independent conductor A and independent conductor B comprises a linear conductor in the embodiment shown in
When each of independent conductor A and independent conductor B comprises an island-like conductor or the like, and when each of both independent conductors is formed in a shape having a longitudinal direction, it is preferred that the smaller one of the angles formed by the endless transverse line 8a and the longitudinal direction of independent conductor A be 72 to 108 deg, particularly 81 to 99 deg. It is also preferred that the smaller one of the angles formed by the endless transverse line 8a and the longitudinal direction of independent conductor B be 72 to 108 deg, particularly 81 to 99 deg. The longitudinal direction means a direction having the maximum width in each of independent conductor A and independent conductor B.
When a radio wave for communication has a wavelength of λ0 in air, it is preferred that each of L1 and L2 be 10 mm to 0.51λ0. When each of L1 and L2 is 10 mm or above, independent conductor A and the first antenna wire 10 are unlikely to be capacitively coupled together, and independent conductor B and the second antenna wire 20 are also unlikely to be capacitively coupled together, improving an antenna gain, in comparison with a case where each of L1 and L2 is less than 10 mm.
When each of L1 and L2 is 0.51λ0 or below, the antenna is likely to be non-directional in comparison with a case where each of L1 and L2 is beyond 0.51λ0. Each of L1 and L2 more preferably ranges from 20 mm to 0.41λ0. Each of L1 and L2 particularly preferably ranges from 25 mm to 0.38λ0.
This condition is preferably applied to a case where the radio wave for communication has a frequency ranging from.1 to 6 GHz. This condition is more preferably applied to a case where the frequency ranges from 2.10 to 2.65 GHz.
In the embodiment shown in
The first antenna wire 10 and the second antenna wire 20 are disposed so that the transverse line 8 extends in parallel or substantially parallel with the vehicle opening edge 21 for a window and that the first antenna wire 10 and the second antenna wire 20 are disposed between the vehicle opening edge 21 for a window and independent conductor C. This arrangement is preferred in terms of improved antenna gain. However, the present invention is not limited to this mode. The first antenna wire 10 and the second antenna wire 20 may be disposed so that the transverse line 8 does not extend in parallel or substantially parallel with the vehicle opening edge 21 for a window. Independent conductor C may be omitted.
Even if the first antenna wire 10 and the second antenna wire 20 are sandwiched between independent conductor C and the vehicle opening edge 21 for a window as stated above without disposing independent conductor A and independent conductor B unlike in the embodiment shown in
In
In the embodiment shown in
The number of the independent conductors is not limited to eight as in the embodiment shown in
When it is assumed that there is the imaginary circle having a radius of R1 and having the center located at the antenna center, it is preferred that a portion or the entire portion of each of the plural independent conductors except for independent conductor A and independent conductor B be disposed in a doughnut-like region having a radius of R1=(0.3 to 0.68)·λ0. When R1 is 0.68·λ0 or below in this case, the antenna gain is improved since the electric field converges in a substantially perpendicular direction to the dielectric substrate without dispersing. When R1 is 0.3·λ0 or above, the antenna gain is improved since the antenna is likely to be matched with a receiver or a transmitter in terms of impedance.
It is preferred that all the plural independent conductors except for independent conductor A and independent conductor B satisfy this condition. However, when at least one of the plural independent conductors except for independent conductor A and independent conductor B satisfies this condition, the planar antenna is operable.
It is preferred that a main portion, the entire portion, the center or the center of gravity of at least one of the plural independent conductor except for independent conductor A and independent conductor B be disposed in the doughnut-like region having a radius of R1=(0.3 to 0.68)·λ0. R1 has a preferable range of (0.36 to 0.66)·λ0. R1 has a more preferable range of (0.40 to 0.65)·λ0.
In the present invention, in a case where each of the plural independent conductors is formed in a linear shape, where each of the independent conductors formed in s such a linear shape has a conductor length of LC, and where the dielectric substrate comprises a material having a shortening coefficient of wavelength of k, when both formulae of λg=λ0·k and k=0.51 are established, it is preferred that one or more of the independent conductors formed in such a linear shape satisfy the formula of LC/λg=0.2 to 0.65. It is possible to improve the antenna gain in this range in comparison with other ranges. However, the present invention is not limited to this mode. The planar antenna is operable as long as one or more of the independent conductors formed in such a linear shape satisfies the formula of LC/λg=0.2 to 0.65 in a case where at least one of the plural independent conductors is formed in a linear shape.
The value of LC/λg preferably ranges from 0.27 to 0.62, and the value of LC/λg more preferably ranges from 0.33 to 0.60 and particularly preferably ranges from 0.37 to 0.56.
In a case where at least one of the plural independent conductors includes a portion formed in a shape except for such a linear shape in the present invention, when one of the independent conductors has the maximum width of LCM, when the dielectric substrate comprises a material having a shortening coefficient of wavelength of k, and when the formula of λg=λ0·k is established, the formula of LCM/λg=0.2 to 0.65 is established. It is possible to improve the antenna gain in this range in comparison with other ranges. The value of LCM/λg preferably ranges from 0.27 to 0.62. The value of LCM/λg more preferably ranges from 0.33 to 0.60 and particularly preferably ranges from 0.37 to 0.56.
When the dielectric substrate or the window glass sheet 9 has a dielectric constant of 6 to 8, and when the dielectric substrate or the window glass sheet 9 has a thickness of 1.8 to 5 mm, the shortening coefficient of wavelength of k is 0.40 to 0.70 for a radio wave for communication having a frequency of 200 MHz to 6 GHz, is 0.40 to 0.64 for a radio wave for communication having a frequency of 400 MHz to 6 GHz and is 0.40 to 0.55 for a radio wave for communication having a frequency of 1 to 6 GHz.
In the embodiment shown in
When an odd number of independent conductors are disposed in the present invention, it is preferred that half of the independent conductors in the amount of (the odd number—1) have symmetrically or substantially symmetrically disposed independent conductors. When the number of the independent conductors is two, it is preferred that the two independent conductors be disposed so as to be symmetrical or substantially symmetrical with each other about the antenna center.
In a case where one or more of the plural independent conductors except for independent conductor A and independent conductor B have a straight portion in the present invention, when it is assumed that there is the imaginary straight line 7, which connects between the center of the circle having a radius of R1 and the center of the straight portion of the at least one independent conductor, it is preferred in terms of improved antenna gain that the angle α formed by the imaginary straight line 7 and the straight portion of the at least one independent conductor (for example, the fourth independent conductor 44 in
In a case where one or more of the plural independent conductors except for independent conductor A and independent conductor B have a curved portion, when it is assumed that there is an imaginary straight line, which connects between the center of the circle having a radius of R1 and the center of the curved portion of the at least one independent conductor, and when it is assumed that there is an imaginary tangent to the curve portion of the at least one independent conductor at the center of the curved portion, it is preferred that the angle α formed by the imaginary straight line and the imaginary tangent be 72 to 108 deg.
One or more of the plural independent conductors except for independent conductor A and independent conductor B may comprise a band-like conductor, a substantially band-like conductor, an island-like conductor or the like. In a case where at least one of the independent conductors comprises an island-like conductor or the like, and where the at least one independent conductor is formed in a shape having a longitudinal direction, when it is assumed that there is an imaginary straight line connecting the center of the circle having the radius of R1 and the center of the longitudinal direction of the at least one independent conductor, it is preferred in terms of improved antenna gain that the angle α formed by the imaginary straight line and the longitudinal direction be 72 to 108 deg.
The angle α more preferably ranges from 81 to 99 deg and particularly preferably ranges from 85 to 95 deg.
When an independent conductor comprises a linear conductor in the present invention, the independent conductor may be formed in a straight-line shape or a curved-line shape. Examples of the curved-line shape include a semicircular shape, a substantially semicircular shape, an arc shape and a substantially arc shape. When all independent conductors except for independent conductor A and independent conductor B are formed in a semicircular shape, a substantially semicircular shape, an arc shape or a substantially arc shape, it is preferred in terms of improved antenna gain that the center of an original circles, on which the semicircular shape, the substantially semicircular shape, the arc shape or the substantially arc shape is based, coincides or substantially coincides with the center of the above-mentioned circle having a radius of R1.
In the embodiment shown in
In the embodiment shown in
When the mode in this case is rephrased, the first to seventh, i.e., seven independent conductor 41 to 47 may be clockwise disposed in the numerical order of the first to seventh on the window glass sheet 9. The respective centers of gravity of the first to seventh independent conductors 41 to 47 are called first to seventh centers of gravity. When it is assumed that there are imaginary straight lines, each of which connects between the center of the circle having a radius of R1 and the center of gravity of each of the first to seventh centers of gravity, the respective imaginary straight lines are called first to seventh center-of-gravity lines. When N is a natural number, and when N varies from 1 to 6, a smaller one of the angles formed by the N-th center of gravity and the (N+1)-th center of gravity is 40.5 to 49.5 deg, and a smaller one of the angles formed by the first center of gravity and the seventh center of gravity is 81 to 99 deg. When it is assumed that there is an imaginary straight line, which connects between the first center of gravity and the seventh center of gravity, this imaginary straight line extends in parallel or substantially parallel with the vehicle opening edge 21, and the first independent conductor 41 is disposed closer to the vehicle opening edge 21 than the third independent conductor 43.
The embodiment shown in
In the present invention, it is preferred in terms of improved antenna gain that the second antenna wire 20 be disposed so as to be symmetrical or substantially symmetrical with the first antenna wire about the antenna center. However, the present invention is not limited to this mode. Even when the second antenna wire 20 is not disposed so as to be symmetrical or substantially symmetrical with the first antenna wire 10 about the antenna center, the planar antenna is operable.
In the present invention, it is preferred that each of the first antenna wire 10 and the second antenna wire 20 comprise a complete loop wire for a circularly polarized wave as shown in
Each of the embodiments shown in
Each of the first antenna wire 10 and the second antenna wire 20 shown in
The present invention may be configured so as to include not only means for capacitively coupling a first point of the first antenna wire 10 and a second point of the first antenna wire 10 except for the first point but also means for capacitively coupling a first point of the second antenna wire 20 and a second point of the second antenna wire 20 except for the first point. Specific examples of these means are the first capacitive coupling wire and the second capacitive coupling wire shown in
In the following description, a combination of the first antenna wire 10 and the wire connected to the first antenna wire 10 (e.g., the first capacitive coupling wire in the embodiment shown in each of
In order to simplify the following description, when the specifications for the shape and the dimensions in connection with only the first antenna are referred to, the specifications for the shape and the dimensions in connection with the first antenna are also applicable to the second antenna on the assumption that the first antenna and the second antenna have the same shape and dimensions or substantially the same shape and dimensions as each other.
In the embodiment shown in each of
Although not shown in
Supposing that the paired coupling branch lines 1 and 2 extend beyond the respective open ends, it is preferred in terms of improved communication property that the paired coupling branch lines be positioned in such a positional relationship that the respective extensions collide with each other and connected to each other. However, the present invention is not limited to this mode. Even if none of the extensions collide with each other or be connected to each other since both extensions are out of alignment with each other, the planar antenna is operable as long as the open end of the coupling branch line 1 and the open end of the second coupling s branch line 2 are close to each other so as to be capacitively coupled together, and as long as the open end of the coupling branch line 1 and the open end of the second coupling branch line 2 are positioned at the closest portions since the paired coupling branch lines 1 and 2 are close to each other.
Although it is preferred in terms of improved communication property that the paired coupling branch lines 1 and 2 be in alignment with or substantially alignment with each other, the present invention is not limited to this mode. The planar antenna is operable even if the paired coupling branch lines 1 and 2 are out of alignment or out of substantially alignment with each other.
In the embodiment shown in
In consideration of improved productivity, it is preferred that the first antenna wire 10 and the first auxiliary line 26 be integrally formed with the first conductive film 28 in region A. It is also preferred that the second antenna wire 20 and the second auxiliary line 27 be also integrally formed with the second conductive film 29 in region B. It is preferred in terms of improved antenna gain that the first conductive film 28 and the second conductive film 29 be disposed in this way.
In the embodiment shown in
In an another embodiment, a third conductive film is disposed in at least one portion of region C (a region other than region A), which is surrounded by the first antenna wire 10 and the first auxiliary line 26, and which has contact with the closest portion of the first antenna wire, and a fourth conductive film is disposed in at least one portion of region D (a region other than region B), which is surrounded by the second antenna wire 20 and the second auxiliary line 27, and which has contact with the closest portion of the second antenna wire 20.
In consideration of improved productivity, it is preferred that the first antenna wire 10 and the first auxiliary line 26 be integrally formed with the third conductive film in region C. Additionally, it is preferred that the second antenna wire 20 and the second auxiliary line 27 be integrally formed with the fourth conductive film in region D. It is preferred in terms of improved antenna gain that the third conductive film and the fourth conductive film be disposed in this way.
In this embodiment, it is preferred in terms of improved antenna gain that the conductive film be disposed in each of the entire portion of region C and the entire portion of region D. However, the present invention is not limited to this mode. The planar antenna is operable as long as the conductive film is disposed in at least one portion of each of region C and region D.
When the center between the closest portions of the first antenna wire 10 and the second antenna wire 20 is called the antenna center, the first antenna wire 10 and the second antenna wire 20 are disposed so that the center of gravity of the first antenna wire 10, the antenna center and the center of gravity of the second antenna wire 20 are in alignment or substantially in alignment with one another in the embodiments shown in
In other words, in the embodiments shown in
In the embodiments shown in
In the present invention, it is preferred in terms of improved antenna gain that a first feeding point be disposed at or in the vicinity of the closest portion of the first antenna wire 10, and that a second feeding point be disposed at or in the vicinity of the closest portion of the second antenna wire 20.
When the planar antenna according to the present invention is used as a receiving antenna, power is fed from the first antenna wire 10 and the second antenna wire 20. When the planar antenna according to the present invention is used as a transmitting antenna, power is fed to the first antenna wire 10 and the second antenna wire 20.
Power feeding means will be described in connection with the embodiments shown in FIGS. 1 to 6. In an example of the power feeding means, the central conductor of a coaxial cable (not shown) is connected to one of the first feeding point and the second feeding point by, e.g., soldering, and the outer conductor of the coaxial cable is connected to the other feeding point by, e.g., soldering. However, the present invention is not limited to this mode. The first power feeding point and the second power feeding point may be, respectively, connected to lead wires, power feeding pins or the like by, e.g., soldering, and the respective lead wires, the respective power feeding pins or the like may be connected to the central conductor and the outer conductor of the coaxial cable.
When the planar antenna according to the present invention is directly connected to a coaxial cable, lead wires, power feeding pins or the like, it is preferred that the feeding points be formed so as to make the line width of the first feeding point wider than the line width of the first antenna wire 10 and/or to make the line width of the second feeding point wider than the line width of the second antenna wire 20. This is effective to improve the reliability of connection.
In another example of the power feeding means, the first power feeding point is connected to a first power feeding line, the second power feeding point is connected to a second power feeding line, the central conductor of a coaxial cable is connected to one of the first and second power feeding lines by, e.g., soldering, and the outer conductor of the coaxial cable is connected to the other power feeding line by, e.g., soldering, although not shown.
The first and second power feeding lines may have respective feeding points provided thereon, and the respective feeding points may be connected to a coaxial cable, lead wires, power feeding pins or the like by, e.g., soldering, or make use of electromagnetic coupling. The present invention is not limited to this mode. Any power feeding means is applicable as long as it is possible to feed power.
The antenna conductor 51 is disposed along with the two conductors, which are spaced from each other by a certain distance and are called independent conductor A and independent conductor B, respectively. The imaginary endless transverse line 58 is a line, which passes through the center of gravity of the antenna conductor 51 or the center of the antenna conductor 51 and extends in parallel with a longitudinal direction of the antenna conductor 51. Independent conductor A is disposed on one of both sides of the antenna conductor 51, and independent conductor B is disposed on the other side of the antenna conductor 51. Independent conductor A and independent conductor B are disposed on the window glass sheet 9 as the dielectric substrate so that the imaginary endless transverse line 51 passes through or extends over or under independent conductor A and independent conductor B. The longitudinal direction of the antenna conductor 51 means a direction having the maximum width.
The antenna conductor 51 shown in
The endless transverse line 58 corresponds-to the endless transverse line 8a in the embodiment shown in
The embodiment shown in
In the present invention, conductor patterns for, e.g., the first antenna wire 10, the second antenna wire 20, the first capacitive coupling wire, the second capacitive coupling wire, the first feeding line and the second feeding line, may be normally fabricated by forming conductive patterns on a dielectric substrate, such as a circuit board.
When the planar antenna according to the present invention is configured as a glass antenna for a vehicle, a window glass sheet is used as the dielectric substrate, and the conductors of the planar antenna according to the present invention (the conductors disposed on the dielectric substrate, such as the antenna wires 10 and 20, the coupling branch lines 1 and 2, the independent conductors 41 to 48, the antenna conductor 51 and the power source 54) are normally formed by printing paste containing conductive metal, such as silver paste, on an interior surface of the window glass sheet and baking the paste. However, the present invention is not limited to this forming method. Linear members or foil-like members, which are made of a conductive substance, such as copper, may be formed on an interior surface or an exterior surface of the window glass sheet or in the window glass sheet per se.
The antenna device according to the present invention is appropriate to be employed in communication having a frequency band of 1 to 6 GHz and more appropriate to be employed in communication having a frequency band of 2.10 to 2.65 GHz. In other words, it is preferred that the frequency of a radio wave for communication contain a frequency ranging from 1 to 6 GHz. It is more preferred that the frequency of a radio wave for communication contain a frequency ranging from 2.10 to 2.65 GHz. The planar antenna according to the present invention is applicable to communication using a linearly polarized wave, such as a horizontally polarized wave and a vertically polarized wave for, e.g., a digital television, and communication using a circularly polarized wave, such as a satellite wave.
Although the present invention will be described with reference to examples, the present invention will not be limited to these examples. Various variations or modifications are included in the present invention as long as the variations and modifications do not depart from the spirit of the invention. Now, the examples will be described in detail, referring to the accompanying drawings.
A planar antenna, which was configured in the same way as the planar antenna shown in
When the horizontal direction is defined as being an elevation angle of 0 deg, and when the zenith is defined as being an elevation angle of 90 deg, the directivity of the planar antenna was measured at an elevation angle of 60 deg on the rear side of the automobile as viewed from the antenna center. The measurement results are shown in
A front side and a rear side of the automobile are shown on the portion in a right direction and the portion in a left direction portion in
With respect to the antenna gain shown in
A planar antenna was fabricated in the same way as Example 1 except that the eight independent conductors 41 to 48 were disposed as shown in
The directivity was measured. The measurement results are shown in
A planar antenna was fabricated in the same way as Example 2 except that the independent conductor 48 was not disposed. The directivity was measured. The measurement results are shown in
A planar antenna was fabricated in the same way as Example 2 except that none of the independent conductors 41, 43, 45, 47 and 48 was disposed (in other words, in the same way as the planar antenna shown in
As described, explanation of Examples 1 to 4 has been made. When the difference between the maximum value and the minimum value of the antenna gain in each of Examples 1 to 4 is called Z, and when respective Examples 1 to 4 have Z1 to Z4 in connection with Z, the difference between Z1 and each of Z1 to Z4 is listed in Table 1.
The planar antenna according to the present invention is applicable to communication using, e.g., a circularly polarized wave, such as the ETC or the SDARS (Satellite Digital Audio Radio System having a band of 2.1 to 2.65 GHz). The planar antenna according to the present invention is also applicable to various kinds of data communication, such as the DSRC (Dedicated Short Range Communication) using a frequency similar to the ETC system. The planar according to the present invention is also applicable to transmit and receive a radio wave for digital terrestrial television broadcasting (473 to 767 MHz); a radio wave in the 800 MHz band, the 1.5 GHz band, the 1.8 GHz band, and the 1.9 GHz band for cellular phones, and in the 1.2 GHz band and the 1.5 GHz band for the GPS; and a radio wave using a frequency of 2.5 GHz for the VICS (Vehicle Information and Communication System). The planar antenna according to the present invention is also applicable to transmit and receive a radio wave in the UHF band (300 MHz to 3 GHz) to transmit a radio wave in the Keyless Entry System for automobiles, and to transmit or receive a radio wave in a high frequency band (3 GHz to 30 GHz) and a millimeter-wave band (30 GHz to 300 GHz).
The entire disclosure of Japanese Patent Application No. 2005-281725 filed on Sep. 28, 2005 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.
Number | Date | Country | Kind |
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2005-281725 | Sep 2005 | JP | national |