Half-wavelength antenna device and low-profile antenna device using the same

Abstract

To provide a compact, half-wavelength antenna device with adjustable directivity. [Solution] The half-wavelength antenna device for vehicles consists of a conductive plate 10, a base 40, a half-wavelength element 20, and a powerless element 30. The conductive plate 10 has a power supply section 11 and a ground 12. The base 40 is made of a plate-shaped dielectric that is erected on the conductive plate. The half-wavelength element 20 is The base 40 is a plate-shaped component that is positioned on one side of the base 40, connected to the power supply unit 11, and insulated from the ground 12. The unpowered element 30 is a plate-shaped component that is positioned on the other side of the base 40, parallel to and close to the half-wavelength element 20 so as to electromagnetically couple to the half-wavelength element 20 via the base 40, and is insulated from the ground 12.

Description

Technical Field

[0001] The present invention relates to a half-wave antenna device and a low-profile antenna device using the same, and more particularly to a half-wave antenna device capable of adjusting directivity and a low-profile antenna device using the half-wave antenna device.

Background Art

[0002] Currently, various antenna devices are mounted on vehicles. Such antenna devices include, for example, an AM / FM radio antenna capable of receiving AM broadcast and FM broadcast. Generally, a rod antenna is used as the AM / FM radio antenna. The rod antenna includes an element portion in which an element (helical element) made of a spiral conductor is covered with a cover, and a base plate for attaching the element portion.

[0003] When this rod antenna is attached to the vehicle body, the element portion protrudes significantly from the vehicle body, which impairs the appearance and design of the vehicle, and there is a risk of damage during garage entry or car washing. In addition, since the element portion is attached outside the vehicle, there is also a risk of theft.

[0004] Due to such problems, a low-profile antenna device has been proposed in which the overall height of the antenna device is made lower than that of the rod antenna, the element is housed in an antenna case to protect it from exposure outside the vehicle, and the antenna case is configured in a shark fin shape in consideration of the design of the entire vehicle after the antenna is mounted. Such low-profile antenna devices are often 70 mm or less in height and around 200 mm in length in the longitudinal direction due to considerations such as legal regulations.

[0005] However, such antenna devices have a problem in that their radiation efficiency tends to decrease due to the effects of conductor loss (shortening of element length) caused by the low profile of 70 mm or less, which can lead to a degradation of sensitivity. Furthermore, in recent years, vehicles have needed to be equipped with composite antenna devices that include various antennas such as TEL antennas, GPS antennas, and V2X antennas for vehicle-to-vehicle and vehicle-to-infrastructure communication. Therefore, the challenge has been how to accommodate these multiple antennas in the narrow space of a low-profile antenna device. And when accommodating them in a narrow space, it has been necessary to adjust the directivity of the antennas depending on the combination of antennas.

[0006] For example, Patent Document 1 discloses an antenna device that adjusts the directivity of a patch antenna having curved or bent patch elements. Specifically, the device in Patent Document 1 adjusts the directivity in the zenith direction by configuring the patch elements to be curved or bent.

[0007] Furthermore, Patent Document 2 discloses an antenna device in which the directivity of the antenna element is adjusted. Specifically, the device in Patent Document 2 has a configuration in which a ground and a parasitic element are arranged parallel to the antenna element that functions as a dipole antenna or monopole antenna, and the parasitic element is used as a reflector to adjust the directivity. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2019-068124 [Patent Document 2] International Publication No. 2018 / 198349 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, Patent Document 1 describes how to adjust the directivity of a patch antenna, not a linearly polarized antenna. Also, Patent Document 2 describes how to adjust the directivity of a plate-shaped antenna element for quarter wavelengths.

[0010] Furthermore, in the case of a composite antenna system housing multiple antennas, it is possible to use other antennas as reflectors or radiators. In this case, the distance between each antenna needed to be separated by a quarter wavelength. However, in the confined space of a low-profile antenna system, it was difficult to increase the distance between each antenna.

[0011] In view of these circumstances, the present invention aims to provide a compact, directionally adjustable half-wavelength antenna device. Furthermore, it aims to provide a low-profile antenna device using such a half-wavelength antenna device. [Means for solving the problem]

[0012] To achieve the above-mentioned objectives of the present invention, the half-wavelength antenna device according to the present invention comprises a conductive plate having a feed point and a ground; a base made of a plate-shaped dielectric erected on the conductive plate; a plate-shaped half-wavelength element disposed on one side of the base and connected to the feed point and insulated from the ground; and a plate-shaped unpowered element disposed on the other side of the base and positioned parallel to and close to the half-wavelength element so as to be electromagnetically coupled to the half-wavelength element via the base, and insulated from the ground.

[0013] Here, the half-wavelength element may have slits on both sides of the feed line to the feed point for impedance matching.

[0014] Furthermore, the passive element may allow for adjustment of the directivity of the half-wavelength element by adjusting the width and / or height of its plate-like portion.

[0015] Furthermore, a low-profile antenna device for a vehicle using the half-wavelength antenna device of the present invention may also include a base plate fixed to the vehicle, a first-frequency band element positioned at a height distance from the base plate and functioning as an antenna for the first frequency band, and an antenna cover fitted to the base plate and housing the first-frequency band element inside, wherein at least the half-wavelength element and the parasitic element of the half-wavelength antenna device are positioned so as to be covered by the first-frequency band element when viewed from above.

[0016] Furthermore, the antenna comprises a circuit board placed on a base plate and having a power supply terminal, and a coil connected between the first frequency band element and the power supply terminal, which is adjusted to function as a resonant antenna for the second frequency band by a series circuit of the first frequency band element and the coil, wherein the coil is positioned so that its axial direction is parallel to the base plate and parallel to the longitudinal direction of the first frequency band element. [Effects of the Invention]

[0017] The half-wavelength antenna device and low-profile antenna device of the present invention have the advantages of being compact and having adjustable directivity. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a schematic side view illustrating the half-wavelength antenna device of the present invention. [Figure 2] Figure 2 is a schematic perspective view illustrating a specific example of the half-wavelength antenna device of the present invention. [Figure 3] Figure 3 shows the directional pattern of the half-wavelength antenna device of the present invention. [Figure 4] Figure 4 shows the directional pattern when a powerless element is connected to ground as a comparative example. [Figure 5] Figure 5 is a schematic perspective view illustrating another specific example of the half-wavelength antenna device of the present invention. [Figure 6]FIG. 6 is a schematic diagram for explaining still another specific example of the half-wave antenna device of the present invention. [Figure 7] FIG. 7 is a schematic side view for explaining a low-profile antenna device using the half-wave antenna device of the present invention.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments for carrying out the present invention will be described together with illustrated examples. FIG. 1 is a schematic side view for explaining the half-wave antenna device of the present invention. As shown in the figure, the half-wave antenna device of the present invention includes a conductive plate 10, a half-wave element 20, and a non-powered element 30. And it is fed using a coaxial cable 1.

[0020] The conductive plate 10 has a feeding portion 11 and a ground 12. The conductive plate 10 may be provided, for example, by a printed circuit board. That is, the solid ground portion of the printed circuit board becomes the ground 12, and the portion insulated from the ground 12 becomes the feeding portion 11. It is only necessary that the inner conductor of the coaxial cable 1 is connected to the feeding portion 11 and the outer conductor is connected to the ground 12. Note that the conductive plate 10 does not necessarily have to be provided by a printed circuit board, and for example, if it is configured such that through holes are formed in a plate-like conductor and the feeding portion 11 is provided, it is acceptable.

[0021] The half-wave element 20 is erected on the conductive plate 10. The half-wave element 20 is connected to the feeding portion 11 and is insulated from the ground 12. In the illustrated example, an example in which the half-wave element 20 is installed at a right angle on the conductive plate 10 is shown. However, the present invention is not limited to this, and a certain inclination is allowed as long as the conductive plate 10 is arranged so as to be a ground plane with respect to the half-wave element 20. Also, in the illustrated example, the half-wave element 20 is shown as an example composed of a rod-shaped element. However, the present invention is not limited to this, and it may be composed of a plate-shaped element.

[0022] Here, the half-wavelength element 20 is a monopole antenna whose element length is half the wavelength of the corresponding frequency band. Specifically, the element length of the half-wavelength element 20 should be such that, for example, if it is an element for V2X, it is half the wavelength of the 5.9 GHz band. The element length of the half-wavelength element 20 can be adjusted as appropriate depending on the shortening factor, etc.

[0023] The parasitic element 30 is positioned parallel to and close to the half-wavelength element 20 so as to electromagnetically couple with the half-wavelength element 20. The parasitic element 30 is insulated from the ground 12. That is, the parasitic element 30 is not connected to the ground 12 or the feed point 11. The parasitic element 30 is preferably the same size as or larger than the half-wavelength element 20 so as to electromagnetically couple with the half-wavelength element 20 over as wide an area as possible. The half-wavelength antenna device of the present invention allows for adjustment of the antenna's directivity by changing the position, length, and width of the parasitic element 30 and its distance from the half-wavelength element 20. Specifically, for example, the parasitic element 30 may be positioned parallel to and close to the half-wavelength element 20 at a distance of, for example, about 1 / 20 of a wavelength. Also, the parasitic element 30 may be positioned about 1 mm above the ground 12.

[0024] The half-wavelength antenna device of the present invention, configured in this way, behaves like a monopole antenna because the half-wavelength element 20 is erected on the conductive plate 10, and also behaves like a microstrip antenna because the parasitic element 30 is electromagnetically coupled to the half-wavelength element 20.

[0025] The half-wavelength antenna device of the present invention allows for adjustment of directivity using the parasitic element 30. Specifically, the directivity of the half-wavelength element 20 can be directed in the opposite direction from the side on which the parasitic element 30 is provided. In other words, the parasitic element 30 behaves like a reflector with respect to the half-wavelength element 20. However, since reflectors typically need to be located at a distance of 1 / 4 wavelength or more, the parasitic element 30 behaves differently from a reflector.

[0026] Thus, because the half-wavelength antenna device of the present invention has the half-wavelength element 20 and the parasitic element 30 arranged in close proximity, it is possible to make a compact antenna device. Furthermore, the parasitic element 30 makes it possible to adjust the directivity of the antenna device despite its compact size.

[0027] Figure 2 is a schematic perspective view illustrating a specific example of the half-wavelength antenna device of the present invention. In the figure, parts with the same reference numerals as in Figure 1 represent the same components. As shown in the figure, in this example, the half-wavelength element 20 is composed of a plate-shaped element. The plate-shaped half-wavelength element 20 can be formed, for example, by cutting out a sheet metal by sheet metal processing. The passive element 30 is also composed of a conductive plate-shaped body. Similarly, the plate-shaped passive element 30 can be formed, for example, by cutting out a sheet metal by sheet metal processing. With this configuration, the passive element 30 can be more strongly electromagnetically coupled to the half-wavelength element 20, making it possible to adjust the directivity over a wider range.

[0028] Figure 3 shows the directivity pattern of the half-wavelength antenna device of the present invention, with Figure 3(a) showing the vertical directivity and Figure 3(b) showing the horizontal directivity. Without a parasitic element, the antenna is omnidirectional. However, in the case of the half-wavelength antenna device of the present invention, as shown in the figure, the directivity is oriented in the opposite direction to the side where the parasitic element 30 is provided. Thus, in the half-wavelength antenna device of the present invention, the directivity of the half-wavelength element 20 can be adjusted by using a parasitic element 30 placed in close proximity.

[0029] When the parasitic element 30 is connected to ground 12, the directivity is as shown in Figure 4. Figure 4 is a comparative example of the directivity pattern when the parasitic element is connected to ground, with Figure 4(a) showing the vertical directivity and Figure 4(b) showing the horizontal directivity. As shown in the figure, when the parasitic element 30 is connected to ground 12, it approaches omnidirectional compared to the half-wavelength antenna device of the present invention. Therefore, it is preferable that the parasitic element 30 is not connected to ground 12 and is insulated from ground 12. Thus, in the present invention, it is not necessary to connect the parasitic element 30 to ground 12, so there is a high degree of freedom in the placement of the parasitic element 30.

[0030] Figure 5 is a schematic perspective view illustrating another specific example of the half-wavelength antenna device of the present invention. In the figure, parts with the same reference numerals as in Figure 1 represent the same components. As shown in the figure, the half-wavelength element 20 is composed of a plate-shaped element, similar to Figure 2. In this example, slits 21 are formed on both sides of the feed line to the feed section 11 of the half-wavelength element 20. The slits 21 are used for impedance matching. That is, by adjusting the depth of the slits 21, it is possible to change the length of the feed line without changing the element length of the plate-shaped element, and to achieve impedance matching to, for example, 50Ω. By providing slits 21 on the plate-shaped element in this way, it becomes unnecessary to provide, for example, a separate matching circuit.

[0031] In the illustrated example, a base 40 is positioned between the half-wavelength element 20 and the passive element 30. The base 40 can be made of an insulator. The base 40 can be erected and fixed to the conductive plate 10, and the half-wavelength element 20 and passive element 30 can be placed on the front and back surfaces of the base 40, respectively. By providing locking holes 22 in the half-wavelength element 20 and the passive element 30 as appropriate, and providing locking claws 41 that engage with the locking holes 22 in the base 40, assembly can be made easier. Furthermore, if the base 40 is made of a dielectric material, the element length can be shortened, making it possible to further miniaturize the device.

[0032] Figure 6 is a schematic diagram illustrating yet another specific example of the half-wavelength antenna device of the present invention, where Figure 6(a) is a front view and Figure 6(b) is a rear view. In the figure, parts with the same reference numerals as in Figure 2 represent the same components. As shown in the figure, in this example, the base 40 is made of a dielectric substrate. The half-wavelength element 20 and the parasitic element 30 are arranged on the front and back surfaces of the base 40 made of the dielectric substrate, respectively. In the illustrated example, the base 40 is shown as a double-sided printed circuit board having a thin metal film on both sides. The thin metal film of the double-sided printed circuit board is appropriately patterned to form the half-wavelength element 20 and the parasitic element 30 of the half-wavelength antenna device of the present invention. Thus, it may be provided by patterning of a printed circuit board rather than by sheet metal processing.

[0033] As described above, the half-wavelength antenna device of the present invention is compact and has adjustable directivity, and therefore may be applied to low-profile antenna devices for vehicles. That is, even when applied to low-profile antenna devices with a shark fin shape and a height of 70 mm or less, which have limited internal space, the half-wavelength antenna device of the present invention can be easily housed and further adjusted to have a desired directivity.

[0034] Figure 7 is a schematic side view illustrating a low-profile antenna device using the half-wavelength antenna device of the present invention. A partial cross-sectional view is provided to illustrate the internal structure of the low-profile antenna device. As shown in the figure, the low-profile antenna device to which the half-wavelength antenna device of the present invention is applied comprises a base plate 50, a first-frequency band element 60, and an antenna cover 70.

[0035] The base plate 50 is fixed to the vehicle. Specifically, the base plate 50 may be a so-called resin base formed of an insulator such as resin, or a so-called metal base formed of a conductor such as metal. Alternatively, the base plate 50 may be a composite base of resin and metal. The base plate 50 is provided with, for example, screw bosses 51. The screw bosses 51 are inserted into holes provided in the roof of the vehicle, and the base plate 50 is fixed to the roof by, for example, using nuts to clamp the roof from inside the vehicle. Power cables, coaxial cables, etc., that connect the inside of the vehicle to the antenna device are inserted through the screw bosses 51. The base plate 50 is also configured to be covered by an antenna cover 70, which will be described later.

[0036] The first frequency band element 60 functions as an antenna for the first frequency band. For example, the first frequency band element 60 can be a so-called capacitively charged antenna element. Specifically, the first frequency band can be the AM frequency band. In the AM frequency band, the first frequency band element 60 functions as a capacitive antenna. The element length of the first frequency band element 60 may also be such that it corresponds to a desired frequency band. For example, it could be the DTV frequency band. In the DTV frequency band, the first frequency band element 60 functions as a resonant antenna. The first frequency band element 60 is positioned with a height gap between it and the base plate 50. In the example shown in Figure 7, the left side of the drawing is the direction of vehicle travel, and the longitudinal direction of the first frequency band element 60 is oriented in the direction of vehicle travel.

[0037] The antenna cover 70 fits onto the base plate 50 and houses the first frequency band element 60 inside. In the illustrated example, the antenna cover 70 defines the external shape of the low-profile antenna device. However, the low-profile antenna device of the present invention is not limited to this, and for example, the antenna cover 70 may consist of an inner cover and an outer cover. That is, it may be a double cover. In this case, the inner cover houses the first frequency band element 60 inside, and the outer cover defines the external shape.

[0038] The half-wavelength antenna device of the present invention is positioned so as to be covered by the first frequency band element 60 when viewed from above. Specifically, the conductive plate 10 is fixed to a boss provided on the base plate 50. The half-wavelength element 20 and the parasitic element 30 are positioned so as to be covered from below the first frequency band element 60. The conductive plate 10 does not necessarily need to be completely covered by the first frequency band element 60; it is sufficient that at least the half-wavelength element 20 and the parasitic element 30 are covered by the first frequency band element 60. Furthermore, the conductive plate 10 does not have to be provided separately from the base plate 50 as shown in the illustrated example; if the base plate 50 is a metal base, the base plate 50 may be used as the conductive plate 10.

[0039] Normally, when the antenna element of a low-profile antenna device is positioned behind the vehicle in the direction of travel, the radiation directed forward in the direction of travel is affected by the first frequency band element 60, etc. However, in the half-wavelength antenna device of the present invention, the directivity is adjustable and is adjusted to point towards the rear in the direction of travel. Specifically, the parasitic element 30 is positioned on the front side in the direction of travel, and the half-wavelength element 20 is positioned on the rear side in the direction of travel. As a result, the directivity of the half-wavelength element 20 is directed towards the rear in the direction of travel. Furthermore, even if there is an influence from surrounding metals or dielectrics in the narrow space of the low-profile antenna device, it is possible to adjust the directivity by adjusting the width and height of the parasitic element 30 and the distance to the half-wavelength element 20.Therefore, since it is not necessary to position the half-wavelength antenna device while avoiding the first frequency band element 60, there is a high degree of freedom in positioning within the narrow space inside the antenna cover of the low-profile antenna device.

[0040] Here, an example of a low-profile antenna device using the half-wavelength antenna device of the present invention shown in Figure 7 is shown, which has a circuit board 80 and a coil 90. It is also possible to make a composite antenna in this way. The circuit board 80 is placed on the base plate 50 and has a feed terminal 81. The circuit board 80 is appropriately equipped with amplifier circuits, filter circuits, etc., and is configured to receive signals. The coil 90 is connected between the first frequency band element 60 and the feed terminal 81. The series circuit of the first frequency band element 60 and the coil 90 is adjusted to function as a resonant antenna for the second frequency band. Specifically, the second frequency band can be the FM frequency band. For example, the inductor of the coil 90 is appropriately selected so that the series circuit of the first frequency band element 60 and the coil 90 functions as a resonant antenna in the FM frequency band.

[0041] As shown in the figure, the coil 90 is positioned so that its axial direction is parallel to the base plate 50 and parallel to the longitudinal direction of the first frequency band element 60. With this arrangement, even if the length (number of turns) of the coil 90 changes depending on the vehicle model, since the coil 90 is positioned horizontally, only the length changes horizontally, and the distance from the circuit board 80 does not change. Therefore, even if the length of the coil 90 is adjusted, the change in the antenna reception characteristics of the low-profile antenna device will be minimal.

[0042] It should be noted that the half-wavelength antenna device of the present invention is not limited to the illustrated example described above, and various modifications can be made without departing from the spirit of the present invention. [Explanation of Symbols]

[0043] 1 Coaxial Cable 10 Conductive plate 11 Power supply section 12 Grounds 20 Half-wavelength element 21 slits 22 Locking holes 30 Powerless elements 40 bases 41 Locking claw 50 base plate 51 Boss 60 Element for the first frequency band 70 Antenna cover 80 Circuit boards 81 Power supply terminal 90 coils

Claims

1. A half-wavelength antenna device for a vehicle, wherein the half-wavelength antenna device is A conductive plate having a power supply section and a ground, A base made of a plate-shaped dielectric material erected on the conductive plate, A plate-shaped half-wavelength element is positioned on one side of the base and connected to the power supply section, and is insulated from the ground. A plate-shaped passive element is positioned on the other side of the base and is located parallel to and close to the half-wavelength element so as to be electromagnetically coupled to the half-wavelength element via the base, and is insulated from the ground. A half-wavelength antenna device characterized by comprising the following:

2. A half-wavelength antenna device according to claim 1, characterized in that the half-wavelength element is provided with slits on both sides of the feed line to the feed section for impedance matching.

3. A half-wavelength antenna device according to claim 1 or claim 2, characterized in that the directivity of the half-wavelength element can be adjusted by adjusting the width and / or height of the plate-shaped portion of the passive element.

4. A low-profile antenna device for a vehicle using a half-wavelength antenna device according to any one of claims 1 to 3, wherein the low-profile antenna device is A base plate that is fixed to the vehicle, A first frequency band element is positioned with a height gap relative to the base plate and functions as an antenna for the first frequency band, An antenna cover that fits onto the base plate and houses the element for the first frequency band on the inside, It is equipped with, At least the half-wavelength element and the parasitic element of the half-wavelength antenna device are positioned so as to be covered by the element for the first frequency band when viewed from above. A low-profile antenna device characterized by the following features.

5. A low-profile antenna device according to claim 4, further, A circuit board having power supply terminals is placed on the base plate, A coil connected between the first frequency band element and the feed terminal, which is adjusted to function as a resonant antenna for the second frequency band by a series circuit of the first frequency band element and the coil, It is equipped with, The coil is positioned such that its axial direction is parallel to the base plate and parallel to the longitudinal direction of the element for the first frequency band. A low-profile antenna device characterized by the following features.

Images