JP2009188912A - Car antenna - Google Patents

Abstract

An in-vehicle antenna capable of improving the appearance and field of view of a vehicle as compared with the prior art and improving the transmission / reception characteristics of vertically polarized waves coming from a direction horizontal to the ground.
A first radiating conductor 2 provided on a vehicle body side and a second radiating conductor 3 connected to the first radiating conductor 2 via a power feeding portion 8 are provided. The radiation conductor 3 is formed symmetrically with respect to the horizontal axis 22 on the ground surface passing through the feeder 8, and the angle α around the horizontal axis 22 formed by the first radiation conductor 2 and the second radiation conductor 3 is 90. It is formed so as to be less than or equal to the degree.
[Selection] Figure 1

Description

  The present invention relates to a conductor plate type vehicle-mounted antenna mounted on a vehicle.

  A microstrip antenna (hereinafter referred to as MSA) having a structure in which a ground conductor and a circular or rectangular patch-like radiation conductor are sandwiched between dielectrics is often used as a small antenna installed on the vehicle interior side of a vehicle window glass. Since MSA can be reduced in size and thickness by using a high dielectric material such as ceramic, it is widely used as an in-vehicle antenna.

  Further, as an antenna installed on the vehicle interior side of the thin window glass for a vehicle, a planar antenna in which a radiation conductor and a ground conductor are formed on the same plane (for example, see Patent Document 1) and a ground conductor are not required. A film antenna using a balanced antenna (for example, see Patent Document 2) is known.

  These antennas have a peak gain in a direction (normal direction) perpendicular to a radiating element surface (vehicle window glass surface). In order to change this directivity, the antenna is tilted by using a spacer to make the peak gain close to the vertical direction (see, for example, Patent Document 3), or the vertically polarized wave coming from the horizontal direction to the ground. In order to increase reception sensitivity, an antenna (see, for example, Patent Document 4) in which a conductive reflecting member is installed at a predetermined angle with respect to a ground conductor surface (vehicle window glass surface) is known.

JP 2002-252520 A JP-A-8-340208 Japanese Patent Laid-Open No. 5-63424 JP 2005-26783 A

  When installing the antenna using the above-described conventional technology on a vehicle window glass such as a windshield and a rear glass, it is possible not to obstruct the occupant's visual field and to improve the appearance of the vehicle. It is desirable not to damage it.

  However, if the dimensions and arrangement are restricted based on securing the appearance and field of view of the vehicle, it becomes difficult to obtain a desired transmission / reception sensitivity. In particular, when a planar antenna is installed on a vehicle window glass surface that is inclined with respect to a plane horizontal to the ground, a desired reception sensitivity is obtained for vertically polarized waves coming from the horizontal direction with respect to the ground. It is very difficult.

  When using an antenna with a spacer, which is a conventional technology, the antenna must be installed in a vertical direction with respect to the ground, so that the size of the antenna is approximately the same (approximately λ / 2 to λ / 4). A spacer is required. For this reason, it becomes difficult to ensure the appearance and field of view of the vehicle.

  In addition, an antenna in which another conventional conductive reflecting member is installed at a predetermined angle can improve reception sensitivity with respect to vertically polarized waves coming from the horizontal direction, but has a size of about λ / 4 or less. Therefore, it is difficult to say that the appearance and the field of view of the vehicle are sufficiently secured.

  Accordingly, an object of the present invention is to provide an in-vehicle antenna capable of improving the appearance and field of view of a vehicle as compared with the prior art and improving the transmission / reception characteristics of vertically polarized waves coming from a direction horizontal to the ground. It is to provide.

  The present invention has been devised to achieve the above object, and includes a first radiating conductor provided on the vehicle body side, and a second radiating conductor connected to the first radiating conductor via a power feeding portion, The first radiating conductor and the second radiating conductor are formed symmetrically with respect to a horizontal axis that is horizontal on the ground surface passing through the feeding portion, and the horizontal axis formed by the first radiating conductor and the second radiating conductor. This is an in-vehicle antenna formed so that the turning angle α is 90 degrees or less.

  Moreover, this invention is a vehicle-mounted antenna with which the said 1st radiation conductor is pinched | interposed into a transparent film, and is adhere | attached on the window glass plate for vehicles.

  Alternatively, the present invention is the vehicle-mounted antenna in which the first radiation conductor is directly formed on the vehicle window glass plate.

  Further, in the present invention, the first and second radiating conductors include a vertical portion extending vertically from the feeding portion and a horizontal portion extending horizontally from the vertical portion, and the vertical portion of the second radiating conductor is configured to transmit / receive The wavelength is λ and the vertical height is within 0.06λ, and the first radiating conductor and the second radiating conductor are connected or contacted by at least one plate-like element. It is a vehicle-mounted antenna.

  The present invention includes a first radiating conductor formed of a large grounding conductor such as a vehicle body roof, and a second radiating conductor connected to the first radiating conductor via a power feeding portion and extending in the vehicle width direction. The first radiating conductor and the second radiating conductor are formed symmetrically with respect to a horizontal horizontal axis on the ground surface passing through the feeding portion, and are formed by the first radiating conductor and the second radiating conductor. The vehicle-mounted antenna is formed so that an angle α around the horizontal axis is 90 degrees or less.

  According to the present invention, the first radiating conductor and the second radiating conductor are formed on the ground surface passing through the feeding portion so as to be axisymmetric with respect to a horizontal axis that is horizontal, and the first radiating conductor and the second radiating conductor are horizontally formed. By setting the angle α around the axis to 90 degrees or less, it is possible to improve the transmission / reception characteristics of vertically polarized waves coming from a direction horizontal to the ground as compared with the conventional planar antenna.

  In addition, according to the present invention, a small antenna with a height of the entire antenna of about 0.09λ and a protective case with a height of about 0.06λ can be realized. Can be improved.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of an in-vehicle antenna according to the present embodiment, and FIG. 2 is a perspective view thereof.

  In FIG. 1, 1 is a window glass plate for vehicles, such as a windshield or a rear glass. The vehicle window glass plate 1 is inclined by an angle β with respect to a plane horizontal to the ground.

  The in-vehicle antenna 100 includes a first radiating conductor 2 provided on the vehicle body side (vehicle window glass plate 1 in FIG. 1), a second radiating conductor 3 connected to the first radiating conductor 2 via a power feeding portion 8, and the like. The first radiating conductor 2 and the second radiating conductor 3 are formed symmetrically with respect to the horizontal axis 22 that is horizontal on the ground surface passing through the power feeding portion 8.

  The first radiation conductor 2 includes a vertical portion 2b extending vertically from the power supply portion 8 and a horizontal portion 2a extending horizontally from the vertical portion 2b, and is formed in a substantially inverted L shape. Similarly, the second radiation conductor 3 includes a vertical portion 3b extending vertically from the power supply portion 8 and a horizontal portion 3a extending horizontally from the vertical portion 3b, and is formed in an approximately L shape.

  The combined length of the horizontal portion 2a and the vertical portion 2b of the first radiating conductor 2 and the combined length of the horizontal portion 3a and the vertical portion 3b of the second radiating conductor 3 are λ / 4, where λ is the transmission / reception wavelength. It is formed to become.

  The first radiation conductor 2 is sandwiched between protective films (film sheets) 4 having high transparency, and is adhered to the vehicle interior side (lower right side in FIG. 1) of the vehicle window glass plate 1 with an adhesive layer 5 having high transparency. The

  The end of the vertical portion 2b of the first radiating conductor 2 on the feeding portion 8 side and the end of the vertical portion 3b of the second radiating conductor 3 on the feeding portion 8 side are connected by a short stub 23 for impedance matching. Is done.

  The power feeding unit 8 is fed with a coaxial cable or the like. Desirably, balanced power supply may be performed using a balun, two parallel lines, or the like, but even unbalanced power supply operates without problems.

  A dielectric material 7 is provided on the second radiation conductor 3. This dielectric material 7 is for adjusting the electric length of the second radiating conductor 3 to be equal to the electric length of the first radiating conductor 2, and is preferably close to the relative dielectric constant of glass.

  The second radiation conductor 3 and the dielectric material 7 are covered with a protective cover 6, and are adhered to the vehicle window glass plate 1 with the adhesive layer 5 in the same manner as the first radiation conductor 2.

  Now, in the in-vehicle antenna 100 of the present invention, the angle α around the horizontal axis 22 formed by the first radiation conductor 2 and the second radiation conductor 3 is formed to be 90 degrees or less.

  Hereinafter, the reason why the angle α around the horizontal axis 22 formed by the first radiation conductor 2 and the second radiation conductor 3 is 90 degrees or less will be described.

  First, the transmission / reception sensitivity of the vertically polarized wave coming from the horizontal direction of the in-vehicle antenna 100 will be described with reference to FIGS. 3 (a) and 3 (b).

  FIG. 3A shows a current path of the conventional planar antenna 300. The planar antenna 300 has a structure in which the second radiation conductor 3 is in contact with the vehicle window glass plate 1 in the in-vehicle antenna 100 of FIG. 1, that is, the horizontal axis 22 formed by the first radiation conductor 2 and the second radiation conductor 3. The turning angle α is 180 degrees.

  In the planar antenna 300, for example, a current flows as indicated by a dotted line in FIG. Here, the current 9 flowing through the horizontal portion 2a of the first radiating conductor 2 and the current 12 flowing through the horizontal portion 3a of the second radiating conductor 3 have the same magnitude and are in opposite phases and cancel each other out. You can ignore it. This is an effect caused by the symmetric structure of the first radiating conductor 2 and the second radiating conductor 3. When the radiating conductors 2 and 3 are asymmetrical structures, they are not completely canceled out. Further, in the planar antenna 300, the current 9 and the current 12 are not equal in magnitude even when unbalanced feeding is performed instead of balanced feeding, and they do not cancel out completely.

  Therefore, only the current 10 and the current 11 flowing through the vertical portions 2b and 3b contribute to the radiation. However, since the vehicle window glass plate 1 is inclined by the angle β, the currents 10 and 11 are It is decomposed into a vertical component 14. It can be said that only the vertical component 14 of the current relates to the transmission / reception sensitivity of the vertically polarized wave coming from the horizontal direction on the ground, and the horizontal component 13 radiates unnecessary energy.

  On the other hand, FIG. 3B shows the case of the in-vehicle antenna 310 in which the angle α around the horizontal axis 22 of the first radiating conductor 2 and the second radiating conductor 3 is smaller than 180 degrees. In the in-vehicle antenna 310, for example, a current flows as shown by a dotted line in FIG.

  3A, the current 15 and the current 18 flowing through the horizontal portions 2a and 3a cancel each other and can be ignored. Only the current 16 and the current 17 flowing through the vertical portions 2b and 3b can be ignored. Contributes to radiation.

  As shown in FIG. 3B, in the in-vehicle antenna 310, the vertical component 20 of the currents 16 and 17 related to the transmission / reception sensitivity of the vertical polarization is larger than the vertical component 14 of the planar antenna 300. Furthermore, the horizontal component 19 of the current that radiates unnecessary energy is smaller than the horizontal component 13 of the planar antenna 300.

  Here, the vertical component 20 is maximized when α = 90 + β, that is, when the second radiation conductor 3 is arranged in the vertical direction. That is, the angle α around the horizontal axis 22 formed by the two radiation conductors 2 and 3 is expressed by the following equation.

α ≦ 90 + β
Therefore, by making the angle α around the horizontal axis 22 formed by the first radiating conductor 2 and the second radiating conductor 3 smaller than 90 + β, unnecessary horizontal components can be reduced, and radiation to the horizontally polarized wave is reduced. It can be seen that the transmission / reception sensitivity of vertically polarized waves can be improved.

  In FIG. 4, the simulation result of the planar antenna 300 and the vehicle-mounted antenna 310 is shown.

  The graph of FIG. 4A shows the relationship between the angle β of the vehicle window glass plate 1 and the average gain in the horizontal direction of the vertical polarization when the planar antenna 300 is attached to the vehicle window glass plate 1. Is. The horizontal axis represents the angle β between the vehicle window glass plate 1 and the ground (horizontal plane), and the vertical axis represents the average value of the radiation gain [dBi] on a plane horizontal to the ground.

  As shown to Fig.4 (a), as angle (beta) of the window glass plate 1 for vehicles becomes small, a vertical polarization decreases and a horizontal polarization increases. When the angle β is around 45 degrees, the vertical polarization and the horizontal polarization become substantially equal, and when the angle β is smaller than 45 degrees, the horizontal polarization becomes larger than the vertical polarization. That is, in the planar antenna 300, the transmission / reception sensitivity of vertically polarized waves decreases as the angle β of the vehicle window glass plate 1 decreases.

  On the other hand, the graph of FIG. 4B shows the relationship between the angle α around the horizontal axis 22 formed by the two radiation conductors 2 and 3 and the average gain of the vertical polarization in the horizontal direction using the vehicle-mounted antenna 310. It is. The angle β of the vehicle window glass plate 1 was 25 degrees. The horizontal axis represents the angle α around the horizontal axis 22 formed by the first radiation conductor 2 and the second radiation conductor 3, and the vertical axis represents the average value of the radiation gain [dBi] on the plane horizontal to the ground.

  As shown in FIG. 4B, as the angle α around the horizontal axis 22 formed by the two radiating conductors 2 and 3 is decreased from the state of α = 180 degrees (planar antenna 300), the horizontal polarization is changed. It can be seen that the vertical polarization increases. The vertical polarization is maximized in the vicinity of α = 90 degrees, and there is a gain improvement effect of about 6 dB as compared with the case where α = 180 degrees (planar antenna 300). Further, it can be seen that when α is made smaller than 90 degrees, the horizontal polarization decreases rapidly.

  As described above, by setting the angle α formed by the first radiating conductor 2 and the second radiating conductor 3 to 90 degrees or less, the transmission / reception sensitivity of the vertically polarized wave can be improved, and the horizontal direction is higher than that of the conventional planar antenna 300. It can be seen that the average gain of the vertical polarization can be improved by about 6 dB. The effect is maximized when the angle α is about 90 degrees, but a sufficient effect can be obtained even if the angle α is smaller than 90 degrees.

  Thus, the in-vehicle antenna 100 according to the present embodiment is formed such that the angle α around the horizontal axis 22 formed by the first radiation conductor 2 and the second radiation conductor 3 is 90 degrees or less. Thereby, even if the angle (beta) of the window glass plate 1 for vehicles is small, the transmission / reception sensitivity of the vertically polarized wave which arrives from a horizontal direction can be improved.

  In the in-vehicle antenna 100, the first radiating conductor 2 and the second radiating conductor 3 are formed symmetrically with respect to the horizontal axis 22. As a result, the current 15 flowing through the horizontal portion 2a of the first radiating conductor 2 and the current 18 flowing through the horizontal portion 3a of the second radiating conductor 3 cancel each other out of phase, and the radiant energy leaks into the horizontally polarized wave. As a result, the transmission / reception sensitivity of vertical polarization can be improved.

  Further, in the in-vehicle antenna 100, the first radiation conductor 2 is sandwiched between protective films 4 with high transparency, and an adhesive layer 5 with high transparency is provided between the vehicle window glass plate 1 and the protective film 4. Thereby, the obstruction | occlusion of a passenger | crew's visual field at the time of mounting the vehicle-mounted antenna 100 can be reduced.

  Further, as in the present invention, the radiation conductor structure is a low-profile antenna in which an inverted L-shaped dipole and a short stub are combined. It can be suppressed to the size of.

  Moreover, in the vehicle-mounted antenna 100, since the transmission / reception sensitivity of vertical polarization becomes good, the height (vertical height) of the second radiation conductor 3 protruding from the vehicle window glass plate 1 can be reduced, Even if the size of the protective cover 6 is included, it can be reduced to about 0.06λ. Thereby, the height of the entire vehicle-mounted antenna 100 from the upper part of the first radiation conductor 2 to the lower part of the second radiation conductor 3 can also be suppressed to about 0.09λ.

  Therefore, it is possible to prevent the vehicle occupant's visual field from being obstructed as compared with the prior art and not to impair the appearance of the vehicle.

  A modification of the present invention will be described.

  A vehicle-mounted antenna 500 shown in FIG. 5 has basically the same structure as the vehicle-mounted antenna 100 of FIG. 1 except for the first radiation conductor 51.

  The first radiation conductor 51 uses a plurality of thin conductors 52 and 53 of about 80 μm or less, and the conductor 52 is parallel to the vertical portion 2a (vertical direction in FIG. 1), and the conductor 53 is the conductor 52. Are arranged in a grid structure by wiring in the horizontal direction (left and right in FIG. 1) so as to be orthogonal to each other. In general, if the lattice spacing is sufficiently small to be about λ / 20 or less, an operation substantially equivalent to that of a plate conductor is possible.

  The first radiation conductor 51 is sandwiched between transparent films and adhered to the vehicle window glass plate 1 or directly formed on the vehicle window glass plate 1.

  By changing the first radiating conductor 51 into a lattice shape, the occupant's field of view can be further improved.

  In the in-vehicle antenna 500, the conductors 52 and 53 are vertically and horizontally wired to form the first radiating conductor 51 in a lattice shape. For example, a metal plate is used as the first radiating conductor, and a number of rectangular shapes are used on the metal plate. Holes may be provided in a matrix to form the first radiating conductor 51 in the form of a lattice.

  The in-vehicle antenna 600 shown in FIG. 6 is obtained by directly forming the first radiation conductor 2 on the vehicle window glass plate 1. In the in-vehicle antenna 600, the first radiating conductor 2 and the second radiating conductor 3 are formed separately, and the first radiating conductor 2 and the second radiating conductor 3 are connected via the spring terminal 21. ing. The protective cover 6 covering the second radiation conductor 3 is bonded to the vehicle window glass plate 1 by the adhesive layer 5 in the same manner as the vehicle-mounted antenna 100 of FIG.

  The in-vehicle antenna 600 has a structure like a kind of connector with a built-in antenna in which the second radiating conductor 3 is covered by the protective cover 6, so that the handling becomes easy.

  The in-vehicle antenna 700 shown in FIG. 7 has a plate-like structure with a large size so that the first radiation conductor 71 can be regarded as a ground conductor.

  In the in-vehicle antenna 700, the securing of the appearance and the field of view, which are the objects of the present invention, is greatly impaired, but the use of the vehicle body roof as the first radiation conductor 71 does not impair the securing of the appearance and the field of view. It is feasible.

  That is, the in-vehicle antenna 700 is formed by forming the first radiating conductor 71 with a vehicle body roof and connecting the second radiating conductor 3 via the feeding portion 8 provided at the end portion on the vehicle window glass plate 1 side. It is. The end of the first radiating conductor 71 on the vehicle window glass plate 1 side and the end of the second radiating conductor 3 on the power feeding unit 8 side are connected by a short stub 72.

  In the in-vehicle antenna 700, since the second radiation conductor 3 is attached to the end of the vehicle body roof on the vehicle window glass plate 1 side, it is possible to further improve the appearance and the field of view. Moreover, according to the vehicle-mounted antenna 700, the transmission / reception sensitivity equivalent to the vehicle-mounted antenna 100 of FIG. 1 can be expected.

  The in-vehicle antenna 800 shown in FIG. 8 is such that the first radiation conductor 2 provided on the vehicle window glass plate 1 is also covered with a protective cover 81. While securing the appearance and field of view, which are the objects of the present invention, is greatly impaired, the in-vehicle antenna 800 can be handled completely as a cable assembly, so that the handling becomes very easy.

  A vehicle-mounted antenna 900 shown in FIG. 9 is a dual-band antenna in which a pair of radiation conductors 91 and 92 are formed in addition to the vehicle-mounted antenna 100 of FIG.

  The first radiating conductor 2 and the third radiating conductor 91, and the second radiating conductor 3 and the fourth radiating conductor 92 are formed on the same plane, and are connected by connecting portions 93 and 94, respectively, in which the feeding portion 8 is provided at the center. Is done.

  The third radiating conductor 91 includes a vertical portion 91b extending vertically from the connection portion 93 and a horizontal portion 91a extending horizontally from the vertical portion 91b in the opposite direction to the first radiating conductor 2. Similarly, the fourth radiating conductor 92 includes a vertical portion 92b extending vertically from the connection portion 94 and a horizontal portion 92a extending horizontally from the vertical portion 92b in the opposite direction to the second radiating conductor 3.

  The vehicle-mounted antenna 900 can be used as, for example, a dual-band antenna shared by the AMPS band (850 MHz band) and the PCS band (1950 MHz band).

It is sectional drawing of the vehicle-mounted antenna which shows suitable embodiment of this invention. It is a perspective view of the vehicle-mounted antenna which shows suitable embodiment of this invention. FIG. 3A is a diagram schematically showing the current flow of the planar antenna, and FIG. 3B is a schematic diagram showing the current flow of the vehicle-mounted antenna in which the angle α formed by the two radiation conductors is smaller than 180 degrees. FIG. 4A is a graph showing the relationship between the angle β of the vehicle window glass plate and the average gain of the vertical polarization in the horizontal direction in the planar antenna of FIG. 3A, and FIG. 4 is a graph showing a relationship between an angle α formed by two radiation conductors and an average gain in the horizontal direction of vertical polarization in the in-vehicle antenna in FIG. It is a perspective view of the vehicle-mounted antenna which shows one modification of this invention. It is sectional drawing of the vehicle-mounted antenna which shows one modification of this invention. It is a perspective view of the vehicle-mounted antenna which shows one modification of this invention. It is sectional drawing of the vehicle-mounted antenna which shows one modification of this invention. It is a perspective view of the vehicle-mounted antenna which shows one modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle window glass plate 2 1st radiation conductor 3 2nd radiation conductor 4 Protective film 5 Adhesive layer 6 Protective cover 7 Dielectric material 8 Feed part 22 Horizontal axis 23 Short stub

Claims (5)

  A first radiating conductor provided on the vehicle body side and a second radiating conductor connected to the first radiating conductor via a feeding portion, and the first radiating conductor and the second radiating conductor pass through the feeding portion. It is formed symmetrically with respect to a horizontal horizontal axis on the ground surface, and formed so that an angle α around the horizontal axis formed by the first radiation conductor and the second radiation conductor is 90 degrees or less. In-vehicle antenna.   The in-vehicle antenna according to claim 1, wherein the first radiation conductor is sandwiched between transparent films and adhered to a vehicle window glass plate.   The in-vehicle antenna according to claim 1, wherein the first radiation conductor is directly formed on a vehicle window glass plate.   The first and second radiating conductors include a vertical portion extending vertically from the power feeding portion and a horizontal portion extending horizontally from the vertical portion, and the vertical portion of the second radiating conductor is vertical with a transmission / reception wavelength as λ. The height of the direction is formed to be within 0.06λ, and the first radiating conductor and the second radiating conductor are connected or contacted by at least one plate-like element. 3. The on-vehicle antenna according to any one of 3 above.   A first radiating conductor formed of a large grounding conductor such as a vehicle body roof, and a second radiating conductor connected to the first radiating conductor via a power feeding portion and extending in the vehicle width direction. The first radiating conductor and the second radiating conductor are formed symmetrically with respect to a horizontal axis that is horizontal on the ground surface passing through the feeding portion, and the horizontal axis formed by the first radiating conductor and the second radiating conductor. The vehicle-mounted antenna is characterized in that the angle α of the antenna is 90 degrees or less.

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