JP4387956B2 - Automotive V-shaped trapezoidal element antenna - Google Patents

Description

  The present invention relates to a trapezoidal element antenna, and more particularly to an in-vehicle V-shaped trapezoidal element antenna mounted on a vehicle such as an automobile.

  FIG. 15 is a structural diagram of the dipole antenna 20 in the conventional configuration. If the element length on one side of the dipole antenna 20 is λ / 4, the total length of the element is λ / 2. In general, the λ / 2 dipole antenna 20 is also called a half-wave dipole antenna. At this time, the antenna gain is 2.15 dBi.

  FIG. 16 is a characteristic diagram of a radiation pattern of the dipole antenna 20 in the conventional configuration. The antenna pattern cut in the XY plane has a peak in the direction perpendicular to the dipole and becomes a radiation pattern such as “8” as shown in the figure.

  FIG. 17 is a characteristic diagram showing the return loss of the dipole antenna 20 in the conventional configuration. According to the law of power conservation, the return loss measured electrically indicates the electromagnetic wave radiated to the space. Therefore, assuming that the resonance frequency of the radiated electromagnetic wave is 600 MHz and the target value of return loss is −10 dB, the bandwidth is 550 MHz to It becomes 650 MHz. However, in this state, sufficient characteristics cannot be expected for receiving terrestrial digital broadcasts having a bandwidth of 473 MHz to 701 MHz.

  In addition, when the dipole antenna 20 is used for receiving terrestrial digital broadcasts, and the antenna is mounted on an automobile and the dipole antenna 20 is used as an antenna for receiving terrestrial digital broadcasts, the bandwidth is narrow, so one element is used as a band. It is difficult to satisfy the width.

  Therefore, as disclosed in Patent Document 1, a technique for widening the bandwidth by flattening the element portion of the dipole antenna 20 has been disclosed, and the bandwidth can be widened.

  Furthermore, a technique for arranging a composite antenna composed of a plurality of antennas on a roof as shown in Patent Document 2 is also disclosed.

JP 2003-51708 A Japanese Patent Laid-Open No. 8-8637

  In the case of an automobile, the position of the vehicle and the direction of travel change each time the vehicle moves, and the directional relationship with the transmitter station changes. Therefore, the antenna directivity is preferably non-directional.

  FIG. 18 is a schematic diagram showing a situation in which an antenna is mounted inside a bumper of a vehicle. In order to receive a terrestrial digital television broadcast in an automobile, the dipole antenna 20 may be used by being mounted inside a synthetic resin bumper or an outer panel before and after the vehicle. The dipole antenna 20 installed at the front and rear of the vehicle only needs to cover the front or rear of 180 °, and does not need to receive radio waves coming from other directions. However, the dipole antenna 20 as it is is too large and difficult to install inside the bumper or outer panel.

  Further, in order to receive terrestrial digital television broadcasting, the bandwidth of the antenna needs to cover 473 MHz to 701 MHz. However, when it is built in the vehicle bumper, the distance (d) between the antenna and the metal body becomes narrow, and there is a problem that the bandwidth of the antenna becomes narrower than that of the antenna alone due to the influence of the metal body.

  FIG. 19 is a characteristic diagram of a directivity pattern when a dipole antenna 20 having a conventional configuration is mounted inside a bumper of a vehicle. Null is generated in the direction in which the antenna element extends along the metal body, that is, in the vicinity of the vehicle in the lateral direction (0 °, 180 °), and the antenna gain tends to decrease. There is a problem that a direction that cannot be performed (for example, 150 ° Null shown in the figure) occurs.

In order to solve the above problems, a V-shaped trapezoidal element antenna for in-vehicle use according to the present invention includes a plate-shaped trapezoidal conductor formed of opposed long sides and short sides, and a trapezoidal shape arranged side by side. A trapezoidal element antenna having a feeding point for feeding power to a conductor and a parasitic element arranged on the short side of the trapezoidal conductor, wherein the trapezoidal element is bent into a V shape across the feeding point An in-vehicle V-shaped trapezoidal element antenna, comprising: an antenna; a reflector connected to a body or ground of a conductive vehicle; and a support member that supports the trapezoidal element antenna and the reflector. wherein a parasitic element, said bent a reflector to the reflective plate direction to close the V-shape as a back side, and a diversity antenna arrangement disposed before and after the vehicle octopus The features.

  In the in-vehicle V-shaped trapezoidal element antenna according to the present invention, the feeding point is supported by a support member at a position farther from the reflector than the trapezoidal conductor.

  Furthermore, in the in-vehicle V-shaped trapezoidal element antenna according to the present invention, the parasitic element of the trapezoidal element antenna has a narrow rectangular shape or a trapezoidal shape that is bent toward the reflecting plate with an axis passing through a feeding point as a center. It is characterized by being.

  Furthermore, in the in-vehicle V-shaped trapezoidal element antenna according to the present invention, the bending angle of the trapezoidal element antenna is greater than 0 degree and less than 180 degrees.

Furthermore, in the vehicle V-shaped trapezoidal elements antenna according to the present invention, the by the trapezoid element antenna and the parasitic element in a shape close to a V-shape, a Null the gain is decreased reflecting plate side It is characterized by having been arranged in .

  By using the present invention, generation of null is suppressed, a non-directional radiation pattern in the range of 180 ° behind the vehicle has a wide frequency characteristic even when mounted in the vicinity of the body, and terrestrial digital television broadcasting (band) There is an effect that it is possible to realize a vehicle antenna capable of receiving (width: 473 MHz to 701 MHz).

  In addition, when compared with a dipole antenna that is planarized by using a parasitic element for miniaturization of the element portion, the element size can be reduced.

  Hereinafter, a configuration (hereinafter referred to as a reference configuration) which is a reference of the present invention and an embodiment of the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings.

  First, a description will be given using the first reference configuration. FIG. 6 is an element pattern diagram of the trapezoidal element antenna 1 in the first reference configuration. The trapezoidal element antenna 1 has a trapezoidal element 3, a feeding point 2, and a parasitic element 4 arranged on the short side of the trapezoidal element pattern. The trapezoidal element 3 is a plate made of conductive metal or the like, and the feeding point 2 is connected to the trapezoidal element 3.

  FIG. 7 is a return loss characteristic diagram of the trapezoidal element antenna in the first reference configuration. Hereinafter, a description will be given with reference to FIGS. The resonance frequencies f1 and f2 are within the target value of the return loss, the length of the lower side of the trapezoidal element antenna 1 including the trapezoidal element 3 and the feeding point 2 is L1, and the length of the upper side is L2. Each length is experimentally required to be approximately λ / 2 = (L1 + L2) / 2 with respect to the wavelength λ of the resonance frequency f1 in FIG. Note that the bandwidth BW1 of the resonance frequency f1 in FIG. 7 is determined by the height H1 of the trapezoidal element 3.

  The parasitic element 4 is a conductive metal plate and is not connected to other components. The length of the parasitic element 4 is experimentally obtained by approximately λ / 2 = L3 and H2 with respect to the wavelength λ of the resonance frequency f2 in FIG. Note that the bandwidth BW2 of the resonance frequency f2 in FIG. 7 is determined by the height H3 of the parasitic element 4.

  Next, the operation will be described. First, when a current flows from the feed point 2 to the trapezoidal element 3 that is the feed element and resonates with respect to the resonance frequency f1, a current is induced in the parasitic element 4 from the short side of the trapezoidal element 3 that is the feed element. And resonates at the resonance frequency f2. And each resonance overlaps and the broadband is realized.

  The trapezoidal element antenna 1 covers a low frequency band with respect to the target frequency bandwidth, and the parasitic element 4 covers a high frequency band with respect to the target frequency bandwidth, thereby realizing a wide band. . Then, the size of the dipole antenna is simply changed from a rod shape to a planar shape by using a parasitic element 4 to make two resonances and making the trapezoidal element 3 itself wider in bandwidth. Compared to the case of changing to, it has a feature that it can be downsized about 0.6 times.

  FIG. 8 is a perspective view of the planar trapezoidal element antenna 30 in the first reference configuration. FIG. 9 is a top view of the planar trapezoidal element antenna 30 in the first reference configuration.

  When the trapezoidal element antenna 1 is vertically installed in parallel to the GND plate 5 with a distance of 5a, the trapezoidal element antenna 1 has directivity characteristics similar to those of a dipole antenna. Therefore, Null is generated in the direction in which the antenna element extends along the metal body, that is, in the vicinity of the lateral direction of the vehicle (0 °, 180 °), and the antenna gain tends to decrease. There is a problem that a direction in which radio waves cannot be received occurs.

  FIG. 10 is a gain-frequency characteristic diagram of the planar trapezoidal element antenna 30 in the first reference configuration. The gain-frequency characteristic of the antenna varies depending on the distance 5 a between the trapezoidal element antenna 1 and the GND plate 5. This is because the impedance of the antenna changes as the distance between the feeding point 2 and the GND plate 5 becomes narrower. Therefore, when the dimension of the distance 5a is built in the bumper which is in use (d = 15 mm distance). Then, there arises a problem that the antenna gain is decreased by −10 dBd as compared with the case of d = 50 mm.

  In a dipole antenna, it is widely known that the directivity gradually approaches omnidirectional from the figure 8 by changing the antenna shape to a V-shape, but the GND plate 5 is in a state of being built in the bumper. Or this is not the case when the body of a car is close.

  FIG. 11 is a perspective view of the open trapezoidal element antenna 40 in the second reference configuration. The aperture-type trapezoidal element antenna 40 has a shape that is open in a V shape (for example, 90 °) with the feeding point 2 of the trapezoidal element antenna 1 as an axis and both ends of the trapezoidal element antenna 1 away from the GND plate 5 from the feeding point 2. And is fixed by a support member (not shown).

  FIG. 12 is a top view of the aperture trapezoidal element antenna 40 in the second reference configuration. In the figure, the lower direction indicates the rear of the vehicle, and the upper direction indicates the front of the vehicle. FIG. 13 is a directivity pattern characteristic diagram of the aperture trapezoidal element antenna 40 in the second reference configuration. Even if the directivity pattern is formed in a V shape that is bent at a bending angle θ away from the GND plate 5, the gain in the 90 ° and 270 ° directions is improved, but the direction in which the trapezoidal element 3 extends (eg, 135 °). Null is generated at 225 °, and the result is that the direction in which Null is generated is shifted even when compared with a flat trapezoidal element antenna.

  FIG. 14 is a gain-frequency characteristic diagram of the aperture trapezoidal element antenna 40 in the second reference configuration. With respect to the target minimum gain of the antenna of -10 dBd, the minimum gain becomes -13 dBb and the target gain cannot be obtained.

  The antenna in the present embodiment is arranged in front of and behind the vehicle and covers, for example, 180 ° behind the vehicle, and does not need to receive radio waves coming from the front of the vehicle (for example, diversity antenna).

  FIG. 1 is a perspective view of an in-vehicle V-shaped trapezoidal element antenna 10 according to the first embodiment of the present invention. The trapezoidal element antenna 1 has a trapezoidal element 3, a feeding point 2, and a parasitic element 4. Further, the in-vehicle V-shaped trapezoidal element antenna 10 includes a trapezoidal element antenna 1, a GND plate 5, and a support member 6.

  The trapezoidal element 3 is a plate made of conductive metal or the like, and the feeding point 2 is connected to the trapezoidal element 3. Further, the feeding point 2 is connected to the transceiver and feeds the trapezoidal element antenna 1. In the figure, 3a indicates the length of L1, 3b indicates L2, 4a indicates L3, 3c indicates H1, 4c indicates H2, and 4b indicates the length of H3.

  The trapezoidal element antenna 1 is disposed on the isosceles side of the isosceles triangular prism-shaped support member 6 made of a synthetic resin plate, and the bending angle θ sandwiching the two sides of the support member 6 is greater than 0 ° and 180 °. The angle θ is preferably less than 0 °, more preferably 80 ° to 100 °, and more preferably the angle θ is 90 °. Further, the height from the hypotenuse is set to 50 mm, for example. For this reason, the trapezoidal element antenna 1 has a shape bent in a V shape toward the GND plate.

  FIG. 2 is a top view of the in-vehicle V-shaped trapezoidal element antenna 10 according to the first embodiment of the present invention. In the figure, the lower direction is the rear of the vehicle, the upper direction is the front of the vehicle, and the GND plate 5 is disposed on the slope side of the isosceles triangular prism. In the present embodiment, the trapezoidal element antenna 1 is arranged on an isosceles triangular prism, but it may be a thin film or a shape supported by the GND plate 5 using a synthetic resin support member. Needless to say, it is suitable.

  3 is a directivity pattern characteristic diagram of the in-vehicle V-shaped trapezoidal element antenna 10 according to the first embodiment of the present invention, and FIG. 4 is an in-vehicle V-shape according to the first embodiment of the present invention. FIG. 3 is a gain-frequency characteristic diagram of the type trapezoidal element antenna 10.

  As shown in FIG. 1, by arranging the GND plate 5 as a back surface with the feeding point 2 of the trapezoidal element 3 as an axis and closed in a V shape, the direction in which Null is generated is moved to the front surface of the vehicle. 2 and the GND plate 5 have a wide space 5a, so that the directivity is 180 degrees behind the screen, there is no null in the range, and almost flat, and the gain-frequency characteristic is a flat trapezoid with d = 50 mm. As in the case of the element antenna 1, the minimum gain of -9 dBd was obtained and an advantageous effect was obtained.

  FIG. 5 is a front view of the in-vehicle V-shaped trapezoidal element antenna 10 according to the second embodiment of the present invention. By forming the parasitic element 4 into a trapezoid rather than a narrow rectangle, the bandwidth can be made wider. However, since the width (H3) tends to increase, it is necessary to consider a trade-off between downsizing and wideband related to the mounting property on the vehicle.

  From the above, when the embodiment according to the present invention is used, there is an effect that the gain of the bandwidth 473 MHz to 701 MHz can be used for receiving terrestrial digital broadcasting satisfying the target value of −10 dBd. Further, when compared with a dipole antenna planarized by using a parasitic element for miniaturization of the element portion, a trapezoidal element antenna capable of miniaturizing the element size is obtained.

  In the above-described embodiment, the shape of the GND plate 5 is a rectangular flat plate. However, not only the flat plate but also a conductive metal plate such as an automobile body or a conductive three-dimensional structure. It may be a thing.

  Similarly, the position where the antenna is mounted is not limited to the inside of the bumper of the vehicle, and if a metal body (GND plate) is disposed in the vicinity of the antenna, it can be suitably operated regardless of the position on the door, roof, bonnet, etc. Is possible.

  Furthermore, the distance between the feeding point 2 and the GND plate 5, the distance between the tip of the parasitic element 4 and the GND plate 5, and the bending angle θ are preferably set appropriately according to the space in which the antenna is mounted. It is possible to operate.

1 is a perspective view of an in-vehicle V-shaped trapezoidal element antenna according to a first embodiment of the present invention. 1 is a top view of an in-vehicle V-shaped trapezoidal element antenna according to a first embodiment of the present invention. It is a directivity pattern characteristic view of the in-vehicle V-shaped trapezoidal element antenna in the first embodiment according to the present invention. It is a gain-frequency characteristic figure of the V-shaped trapezoid element antenna for vehicles in a 1st embodiment concerning the present invention. It is a front view of the vehicle-mounted V-shaped trapezoidal element antenna in 2nd Embodiment which concerns on this invention. It is an element pattern figure of the planar trapezoid element antenna in the 1st reference composition. It is a return loss characteristic view of the planar trapezoidal element antenna in the first reference configuration. It is a perspective view of the planar trapezoid element antenna in the 1st reference composition. It is a top view of the planar trapezoidal element antenna in the first reference configuration. It is a gain-frequency characteristic figure of the planar trapezoid element antenna in the 1st reference composition. It is a perspective view of the aperture type trapezoidal element antenna in the 2nd reference composition. It is a top view of the aperture type trapezoidal element antenna in the second reference configuration. It is a directivity pattern characteristic figure of an aperture type trapezoidal element antenna in the 2nd reference composition. It is a gain-frequency characteristic figure of an aperture type trapezoid element antenna in the 2nd reference composition. It is a structural diagram of a dipole antenna in a conventional configuration. It is a characteristic view of the directivity pattern of the dipole antenna in a conventional configuration. It is the characteristic figure which showed the return loss of the dipole antenna in a conventional structure. It is a schematic diagram which shows the condition which mounted the antenna inside the bumper of a vehicle. FIG. 6 is a characteristic diagram of a directivity pattern when a dipole antenna having a conventional configuration is mounted inside a bumper of a vehicle.

Explanation of symbols

  1 trapezoidal element antenna, 2 feeding point, 3 trapezoidal element, 4 parasitic element, 5 GND plate, 6 support member, 10 V-shaped trapezoidal element antenna for vehicle use, 20 dipole antenna, 30 flat trapezoidal element antenna, 40 opening Type trapezoidal element antenna.

Claims (5)

A plate-shaped trapezoidal conductor formed of opposing long sides and short sides, a feeding point for feeding power to the trapezoidal conductors arranged side by side, and a parasitic element arranged on the short side of the trapezoidal conductor, And a trapezoidal element antenna bent in a V shape across a feeding point, a reflector connected to the body or ground of a conductive vehicle, and the trapezoidal element antenna and the reflection A vehicle-mounted V-shaped trapezoidal element antenna having a support member for supporting a plate;
The trapezoidal element antenna and the parasitic element are folded in the direction of the reflector so as to be closed in a V shape with the reflector on the back side, and arranged in the front and rear of the vehicle to form a diversity antenna configuration. V-shaped trapezoidal element antenna for vehicle use. The in-vehicle V-shaped trapezoidal element antenna according to claim 1,
The on-vehicle V-shaped trapezoidal element antenna, wherein the feeding point is supported by a support member at a position farther from the reflector than the trapezoidal conductor. The in-vehicle V-shaped trapezoidal element antenna according to claim 1,
The parasitic element of the trapezoidal element antenna is a V-shaped trapezoidal element antenna for vehicle use, which has a narrow rectangular shape or a trapezoidal shape that is bent toward the reflection plate with an axis passing through a feeding point as a center. The in-vehicle V-shaped trapezoidal element antenna according to claim 1,
The V-shaped trapezoidal element antenna for vehicle use, wherein the trapezoidal element antenna has a bending angle larger than 0 degree and smaller than 180 degrees. The in-vehicle V-shaped trapezoidal element antenna according to claim 1,
An in-vehicle V-shaped trapezoidal element antenna, characterized in that a Null whose gain is reduced is arranged on the reflector side by making the trapezoidal element antenna and the parasitic element closed in a V-shape.

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