JP3466408B2 - Automotive antenna - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted antenna that operates as an antenna for a plurality of band signals such as AM / FM and has a short physical length.

[0002]

2. Description of the Related Art In a conventional general antenna as an on-vehicle AM / FM antenna, a telescope-like multistage rod antenna is constructed so as to project and retract. The protruding length is about 1 m, which is about 1/4 of the wavelength of the FM band signal in the protruding state so that the FM band signal can resonate.

In such a conventional structure, the structure for projecting or retracting is complicated. Also,
It is not desirable in appearance that the antenna protrudes from the vehicle body by as much as 1 m.

Therefore, the applicant of the patent has already proposed in Japanese Patent Application No. Hei 8 (1999) -58242 a technique for operating as an on-vehicle antenna with a shorter protruding length.
-114296 is proposed. The proposed technology is
Approximately 15c in physical length using helical coil antenna
m is shorter than 1/4 of the wavelength of the FM band signal, and the antenna effective length is about 1 m so that the FM band signal can resonate.

[0005]

In the above proposed technique, the structure for projecting and retracting is simple because the physical length is short, and the length projecting from the vehicle body is short. Has also been improved. Moreover,
The antenna characteristics for FM band signals have a protruding length of about 1 m.
It is no different from the conventional in-vehicle antenna.

However, deterioration of the antenna characteristics is recognized for AM band signals. Here, even in the conventional antenna with a protruding length of about 1 m, the AM band signal does not resonate, and the output impedance of the antenna is capacitive. In addition, the external load due to the cable connected to the base end of the antenna is also capacitive, and the signal voltage received by the antenna is divided by the output impedance of the antenna and the external load impedance of the cable to become the antenna output. . More specifically, referring to FIG. 10, for example, in a conventional antenna having a protruding length of about 1 m, the output impedance capacitance of the antenna is 10 pF and the external load impedance capacitance of the cable or the like is 100 pF.
If converted into AC resistance values R ₁ and R ₂ , R ₁ is about 16 kΩ, R ₂ is 1.6 kΩ, and the antenna output is about 1/10 of the signal voltage VA. Will end up. In order to improve this, the capacity of the cable or the like should be made as small as possible so that the AC resistance value R ₂ of the external load impedance becomes larger. However, in practice, there is a limit to improvement in cables and the like.

Therefore, if the physical length is made shorter as in the proposed technique, the output impedance of the antenna becomes more capacitive, and the AC resistance value R ₁ exceeds, for example, 50 kΩ. In addition, the signal voltage decreases as much as the protruding length of the antenna. So AM
The band signal antenna output is inevitably attenuated and significantly smaller than the conventional one.

The present invention has been made in view of the circumstances of the above-mentioned proposed technique, and by improving the external load impedance, the attenuation of the antenna output is suppressed, and the antenna characteristics are improved. The purpose is to provide a short onboard antenna.

[0009]

In order to achieve such an object, the vehicle-mounted antenna of the present invention has a long delay wavelength among a plurality of band signals to be transmitted / received to / from the linear delay antenna section by an electric delay structure. It is formed so that it does not resonate with a band signal, but resonates with a band signal with a short wavelength with a physical length shorter than ¼ of the short wavelength, and a signal is provided at the base end of this linear delay antenna unit. A path member is provided, and the linear delay antenna section is formed by the signal path member from the vehicle body and a conductive member having the same potential as the vehicle body, and the physical lengths of the linear delay antenna section and the signal path member are The stray capacitances are arranged at a distance of 50 mm, which is ⅓ of the sum distance, to reduce the stray capacitance generated between the linear delay antenna section, the vehicle body and the conductive member.

Further, the electrical delay structure does not cause the linear delay antenna section to resonate with respect to a band signal having a long wavelength out of a plurality of band signals to be transmitted and received, but to a signal having a short wavelength with respect to a band signal having a short wavelength. The physical length is shorter than 1/4 of the above, and at least the base end portion is formed so as to have a narrow taper shape at the base end and to resonate, and a signal path member is provided at the base end of the linear delay antenna portion. It is also possible to reduce the stray capacitance generated between the linear delay antenna section, the vehicle body, and the conductive member having the same potential as the vehicle body in the tapered shape.

The electrical delay structure may have a helical coil shape.

Further, the electrical delay structure may be formed in a zigzag shape or a ninety-nine folded shape provided on one plane.

Further, the electrical delay structure may be formed in a zigzag shape or a 99-fold shape provided on a conical surface having a columnar shape or at least a narrow base end.

Further, the signal path member may be composed of a linear wire portion extending from the base end of the wire delay antenna portion.

Further, the signal path member may be constituted by a plate member made of a conductive material and continuously provided at the base end of the linear delay antenna section.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a structural diagram of a first embodiment of a vehicle-mounted antenna according to the present invention. FIG. 2 is a graph showing the antenna output capacity when the length L ₂ is changed while keeping the total length L constant in the vehicle-mounted antenna of FIG.

The AM / FM antenna will be described as an example. First, the linear delay antenna unit 10 is formed by a helical coil having an electrical delay structure. The linear delay antenna unit 10 is set to have an antenna effective length at which an FM band signal can resonate, but its physical length L ₁ is naturally shorter than ¼ of the wavelength of the FM band signal. Then, a linear wire portion 12 as a signal path member extends from the base end of the wire delay antenna portion 10, and the linear wire portion 12 is a hole formed in the body 14 for grounding. 16 is inserted through. Further, a dielectric 18 is interposed as a support member between the linear filament portion 12 and the edge of the hole 16. Further, due to the linear wire member 12, the wire delay antenna unit 10 is arranged such that the base end thereof is separated from the vehicle body body 14 by the distance L ₂ . The vehicle-mounted antenna of the present invention has such a configuration. A conductive member having the same potential as the vehicle body body 14 such as a top nut for fixing the vehicle-mounted antenna to the vehicle body body 14 has the same electrical function as the vehicle body body 14, and will be described below including the vehicle body body 14. There is.

By the way, the physical length L ₁ of the linear delay antenna unit 10, the linear delay antenna unit 10 and the vehicle body 1
The sum L of the distance L ₂ of 4 is fixed to 150 mm, and the distance L ₂
FIG. 2 is a graph of the antenna output capacity when V is changed. Here, the winding diameter φ ₁ of the helical coil is 10 mm
And the wire is a solid wire with a diameter of 0.5 mm,
The diameter φ _{2 of the} hole 16 is 20 mm.

As is clear from the graph of FIG. 2, the distance L
₂ is short and the antenna output capacity increases as the base end of the linear delay antenna unit 10 approaches the vehicle body 14. The antenna output capacitance as the distance L ₂ is longer is reduced. It should be noted that increasing the distance L ₂ shortens the physical length L ₁ of the linear delay antenna unit 10 and requires a dense coil pitch, which ultimately impairs antenna characteristics for FM band signals. There is a practical limit to this. From Figure 2, the distance _{L 2} between 50 mm (about 1/3 of the distance of the sum of the physical lengths _{L 1} and physical length _{L 2} of the linear striatum 12 of the linear delay antenna unit 10 L) Thus, the antenna output capacity is almost half that when the distance L ₂ is 0 mm.

Referring to these facts, the distance L _{2 is set} to 50 m.
When the antenna characteristics of the in-vehicle antenna set to m were measured, the receiving sensitivity of the antenna output with respect to the AM band signal was found to be significantly improved by about 6 dB as compared with the case where the distance L ₂ was 0 mm. This is because the linear delay section 12 separates the linear delay antenna section 10 from the vehicle body body 14 by a distance L ₂ , so that the stray capacitance generated between the two is greatly reduced, and the external load impedance is increased. This is because the voltage division ratio of the signal voltage VA can be significantly improved.

FIG. 3 shows a linear delay antenna part provided on one plane with another structure used for the vehicle-mounted antenna of the present invention, and FIG. 3 (a) is formed in a zigzag shape.
(B) is formed in a lateral 99-fold shape, and (c) is formed in a vertical 99-fold shape.

By the way, the linear delay antenna unit 10 shown in FIG. 3 has a wide base end and is likely to generate a large amount of stray capacitance between itself and the vehicle body 14.
2, it is necessary to be separated from the vehicle body 14 by a distance L ₂ . Therefore, if the width of the base end of the linear delay antenna unit 10 is narrow, the value is small even if stray capacitance occurs. An antenna formed based on this technique is shown in FIG.

FIG. 4 shows a linear delay antenna portion which is provided on one plane and has a tapered base end, which is another structure used for the vehicle-mounted antenna of the present invention, and (a) is zigzag. It is formed in the shape of
(B) is formed in a lateral ninety-nine fold shape, and (c) is formed in a substantially ninety-nine fold shape from the base end.

The linear delay antenna unit 10 shown in FIG.
Has an extremely small width at the base end, is substantially the same as the linear filamentous body 12, and does not require the distance L ₂ as shown in FIGS. 1 and 2. Further, even in the case shown in FIG. 4B, the width of the base end is small, and it suffices to provide a slight distance L ₂ . 4C, the width of the base end is small, but in order to further improve the antenna characteristic, the base end of the linear delay antenna unit 10 is fixed to the vehicle body body by the linear linear part 12. It may be provided at a distance L ₂ from 14.

Further, FIG. 5 shows still another structure used for the vehicle-mounted antenna of the present invention, which is a linear delay antenna portion provided on a cylindrical surface, and (a) is a ninety-nine folding in the lateral direction. The shape is formed in a vertical shape, and FIG.

The linear delay antenna section 10 shown in FIG. 5 has a linear linear section 12 extending from the center of the base end thereof. The linear delay antenna unit 10 is arranged with its base end separated from the vehicle body. It is not limited to the one provided on the cylindrical surface as shown in the figure, but may be provided on an appropriate prismatic surface such as a square pillar or a hexagonal pillar.

Further, FIG. 6 shows still another structure used in the vehicle-mounted antenna of the present invention, which is a linear delay antenna portion provided on a conical surface with a narrow base end, and (a) is a lateral direction. Which is formed into a ninety-nine folded shape,
Is formed in a vertical 99-fold shape.

The linear delay antenna section 10 shown in FIG. 6 has a narrow base end, and the base end need not necessarily be separated from the vehicle body. Therefore, the linear filament portion 12 is long enough to be inserted through the vehicle body from the base end.
Should be provided. Here, it goes without saying that the base end of the linear delay antenna unit 10 may be arranged apart from the vehicle body. It should be noted that the present invention is not limited to the one provided on the conical surface as shown in the drawing, but may be provided on an appropriate pyramidal surface such as a quadrangular pyramid or a hexagonal pyramid.

Further, FIG. 7 shows still another structure used for the vehicle-mounted antenna of the present invention, which is a wire provided in a spiral shape on a quadrangular prism and a quadrangular pyramid-shaped surface connected to the base end side thereof. It is a strip delay antenna section.

The linear delay antenna section 10 shown in FIG. 7 has a linear linear section 12 extending from the base end thereof, and the proximal end of the linear delay antenna section 10 may or may not be separated from the vehicle body. It is arranged appropriately.

FIG. 8 is a structural diagram in which the vehicle-mounted antenna of the present invention is applied to an antenna device attached to the outer surface of a vehicle body. In FIG. 8, the base end of the linear delay antenna unit 10 made of a helical coil is fixed to and electrically connected to the mounting member 20 made of a conductive material. The linear delay antenna unit 10 includes an antenna cover 2 made of insulating resin.
2 is covered. The base housing 24 is vertically divided into two parts, and an upper housing 26 made of an insulating resin at the top and a base metal fitting 28 made of a conductive material at the bottom are assembled and fixed by screws 30. The mounting bracket 20 is fixed to the upper housing 26. Then, in the base casing 24, a substrate 32 forming an amplifier circuit, a matching circuit, or the like is fixed and housed in the base metal fitting 28. The base metal fitting 28 is attached to the vehicle body 36 by mounting bolts 34, 34 made of a conductive material.
Is fixed to and electrically connected. Then, the coaxial cable 38 passing through the base metal fitting 28 and the vehicle body 36 is electrically connected to the substrate 32. Further, one end of a strip-shaped plate member 40 as a signal path member made of a conductive material is fixed to a mounting member 20 projecting in the base housing 24 by a screw or the like and electrically connected to the mounting member 20. The other end is fixed to the substrate 32 and is electrically connected.

In such a structure, the substrate 32 is provided with a ground pattern for circuit configuration, and there is a portion of the conductive member having the same potential as the vehicle body 36.
Therefore, the mounting metal fitting 20 as the base end of the linear delay antenna unit 10 is electrically connected to the substrate 32 via the plate member 40, so that the base end of the linear delay antenna unit 10 and the vehicle body 36 have the same potential. The substrates 32 having the conductive members can be separated from each other by L ₂ . Therefore, the stray capacitance generated between the base end of the linear delay antenna unit 10 and the conductive member having the same potential as the vehicle body 36 of the substrate 32 can be reduced.

Here, one end of the plate member 40 is attached to the mounting member 20.
When it is fixed to the substrate 32, it is formed so that its posture is constant and self-supporting, so that the substrate 32 can be easily assembled. The plate member 40 may have any shape as long as the stray capacitance is small. Further, it is not limited to the plate-shaped one, and a copper wire or the like having a rigidity sufficient to stand alone may be used. Furthermore, if the assembly is devised, a flexible conductive wire may be used.

FIG. 9 is a structural diagram of a main part in which the vehicle-mounted antenna of the present invention is applied to a motor drive antenna device. Figure 9
In, a linear filament portion 12 is extended from the base end of the filament delay antenna portion 10 composed of a helical coil. Then, the insulating resin pipe 42 is integrally formed with the linear delay antenna portion and the linear linear portion 12 by insert molding. Further, the insulating resin pipe 42 is covered with an antenna cover 44 made of an insulating material. The antenna cover 44 is inserted into the guide pipe 46 so as to be movable in the axial direction. A top nut 48 having a narrowed portion is screwed into the opening of the tip of the guide pipe 46, and the enlarged portion 44a provided on the outer peripheral portion of the antenna cover 44 restricts outward pull-out. Further, the ground metal fitting 50 is screwed into the screw engraved on the outer periphery of the guide pipe 46. Then, the guide pipe 46 is inserted into the hole 52a formed in the vehicle body 52.
Through, and attach the tip of the grounding metal fitting 50 to the vehicle body 52.
Of the guide pipe 46, and the support member 54 is fitted to the front end of the guide pipe 46, and brought into contact with the surface of the vehicle body 50, and the top nut 48 is tightened to fix the motor drive antenna device to the vehicle body 52. It

In such a structure, if the top nut 48 is a conductive member that is made of a conductive material and is electrically connected to the vehicle body 52 and has the same potential when the antenna is at the rising end, the linear delay antenna is provided. By setting the base end of the portion 10 to be separated from the top nut 48 by the distance L ₂ , the stray capacitance generated between both members can be made small. If the top nut 48 and the support member 54 are made of an insulating material, and the guide pipe 46 is a conductive material and has the same electric potential as the vehicle body 52,
The distance between the proximal end of the linear delay antenna unit 10 and the distal end of the guide pipe 46 or the vehicle body 52 may be set to an appropriate length. Further, if the guide pipe 46 is also an insulating material, it goes without saying that the distance between the base end of the linear delay antenna unit 10 and the vehicle body 52 may be set appropriately.

Although a drive mechanism for raising and lowering the antenna cover 44 and the like is not shown in FIG. 9, a rack cord is connected to the lower end of the antenna cover 44, and a pinion gear meshing with the rack of the rack cord is directly moved by a motor. The reverse rotation drive is the same as the conventional device of this type.

The electrical delay structure forming the linear delay antenna section 10 is not limited to the one described in the above embodiment, and the antenna effective length that can resonate with a band signal having a short wavelength, but a physical length. Any structure may be used as long as the length can be made shorter than 1/4 of the wavelength. The plurality of band signals to be transmitted / received are not limited to AM / FM, and may be any combination of FM band signals and PHS band signals, AM band signals, FM band signals and car phone band signals. Further, the vehicle-mounted antenna of the present invention,
Needless to say, it may be used only for transmission or reception, and "should be transmitted and received" used in the claims is not limited to use for both transmission and reception, but used for one of them. Also includes.

Further, although the linear delay antenna section 10 and the linear linear section 12 in the above-mentioned embodiment are formed by wires and are self-supporting, when they are provided on one plane, they are flexible. It may be formed by providing a pattern on a printed wiring board that does not have a space, or if it is provided on a three-dimensional surface, a pattern is provided on a flexible printed wiring board and the pattern is formed on a pillar or a cone. It may be attached to the stand.
Further, at least the surface of a columnar body or a conical body whose surface is made of an insulating material may be disposed by vapor deposition, plating, or the like.

Further, when it is provided three-dimensionally such as a columnar shape or a conical shape, it is not limited to the above-mentioned embodiment, and it may be a frustum shape, a taper whose inclination is changed on the way, or a curved surface of the change. It can be anything.

[0040]

As is apparent from the above description, the vehicle-mounted antenna of the present invention has the following special effects.

In the vehicle-mounted antenna according to the first aspect of the present invention, the base end of the linear delay antenna unit is connected to the linear delay antenna unit and the signal path member from the vehicle body and the conductive member having the same potential as the vehicle body. 1 / the sum of the physical lengths
3 and 50 mm apart to suppress stray capacitance between the base end of the linear delay antenna and the body of the vehicle. Therefore, the signal voltage of the linear delay antenna is output without being attenuated. To be done. Therefore, even if the linear delay antenna section has a short physical length due to the electrical delay structure, the antenna characteristics for a band signal of a long wavelength that cannot resonate in the linear delay antenna section are improved.

Further, in the vehicle-mounted antenna according to the second aspect of the invention, the linear delay antenna portion is formed in a narrow taper shape at the base end to suppress the stray capacitance generated between the base end portion and the vehicle body or the like. That is, the signal voltage of the linear delay antenna unit is output without being attenuated. Therefore, even if the base end of the linear delay antenna unit is not necessarily separated from the vehicle body and the conductive member having the same potential as the vehicle body, the linear delay antenna unit is similar to that of claim 1. The antenna characteristics for a long-wavelength band signal that cannot resonate are improved.

In the on-vehicle antenna according to the third aspect of the invention, since the linear delay antenna section is formed by the helical coil, it is relatively easy to set the winding diameter, pitch, etc. appropriately. A linear delay antenna unit having desired characteristics can be constructed. Therefore, it is easy to manufacture the vehicle-mounted antenna.

Further, in the vehicle-mounted antenna according to the fourth aspect, since the linear delay antenna portion is formed on one plane, it can be configured by a pattern or the like provided on the printed wiring board, which is suitable for mass production. It is suitable.

Further, in the vehicle-mounted antenna according to the fifth aspect, the linear delay antenna portion is formed on a three-dimensional surface, and the physical length is short, like the helical coil. It can be formed in a small space.

Further, in the vehicle-mounted antenna according to the sixth aspect of the invention, the linear delay line portion extends from the base end of the linear delay line antenna unit to serve as a signal path member. It is sufficient to simply form the wire rod constituting the above at the base end thereof in a straight shape, and the manufacturing is easy. Moreover, the surface area of the linear filament portion is small, and the stray capacitance is accordingly small.

Further, in the vehicle-mounted antenna according to the seventh aspect, since the signal path member is formed by the plate member,
As compared with using a conductive wire or the like that can maintain a constant and independent posture and is highly flexible, it is easier to assemble the plate member to electrically connect it to another member.

[Brief description of drawings]

FIG. 1 is a structural diagram of a first embodiment of an in-vehicle antenna according to the present invention.

FIG. 2 is a graph showing the antenna output capacity when the length L ₂ is changed while keeping the total length L constant in the vehicle-mounted antenna of FIG. 1.

FIG. 3 is a linear delay antenna portion provided on one plane with another structure used for the vehicle-mounted antenna of the present invention, (a)
Is formed in a zigzag shape, (b) is formed in a horizontal 99-fold shape, and (c) is formed in a vertical 99-fold shape. .

FIG. 4 is a linear delay antenna portion which is provided on one plane and has a narrow base end and is formed in a taper shape in yet another structure used for the vehicle-mounted antenna of the present invention, and (a) is formed in a zigzag shape. (B) is formed in a lateral ninety-nine fold shape, and (c) is formed substantially radially from the base end in a ninety-nine fold shape.

FIG. 5 is still another structure used for the vehicle-mounted antenna of the present invention, which is a linear delay antenna portion provided on a cylindrical surface, and (a) is formed in a zigzag shape in the lateral direction. (B) is formed in a vertical 99-fold shape.

FIG. 6 is still another structure used for the vehicle-mounted antenna of the present invention, which is a linear delay antenna portion provided on a conical surface with a narrow base end, and (a) is a lateral 99-fold shape. (B) is formed in a vertical 99-fold shape.

FIG. 7 is still another structure used in the vehicle-mounted antenna of the present invention, which is a linear delay antenna portion provided in a spiral shape on a quadrangular prism and a quadrangular pyramid-shaped surface connected to the base end side thereof. .

FIG. 8 is a structural diagram in which the vehicle-mounted antenna of the present invention is applied to an antenna device attached to the outer surface of a vehicle body.

FIG. 9 is a structural diagram of a main part in which the vehicle-mounted antenna of the present invention is applied to a motor drive antenna device.

FIG. 10 is a diagram for explaining that the signal voltage received by the antenna is divided and attenuated by the output impedance of the antenna and the external load impedance to be the antenna output.

[Explanation of symbols]

10 linear delay antenna section 12 linear linear sections 14, 36, 52 vehicle body 40 plate member L ₂ distance at which the base end of the linear delay antenna section is separated from the vehicle body

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-5-347507 (JP, A) JP-A-6-97723 (JP, A) JP-A-7-94929 (JP, A) JP-A-7- 154121 (JP, A) Actually open 1-179610 (JP, U) Actually open 62-196410 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01Q 1/32 H01Q 1 / 36 H01Q 5/01 H01Q 9/02

Claims (7)

(57) [Claims] 1. A linear delay antenna unit having an electrical delay structure does not resonate with a band signal having a long wavelength among a plurality of band signals to be transmitted and received, and has a short wavelength with respect to a band signal having a short wavelength. Is formed so as to have a physical length shorter than 1/4 and to resonate, and a signal path member is provided at the base end of the linear delay antenna section, and the linear delay antenna section is connected to the vehicle body by the signal path member. The wire and the conductive member having the same potential as the vehicle body are arranged at a distance of about 50 mm, which is 1/3 of the sum of the physical lengths of the wire delay antenna unit and the signal path member, An in-vehicle antenna, which is configured to reduce a stray capacitance generated between a delay antenna section, the vehicle body, and the conductive member. 2. The electric delay structure prevents the linear delay antenna section from resonating with a band signal having a long wavelength among a plurality of band signals to be transmitted and received, and having a short wavelength with respect to a band signal having a short wavelength. The physical length is shorter than 1/4 of the above, and at least the base end portion is formed so as to have a narrow taper shape at the base end and to resonate, and a signal path member is provided at the base end of the linear delay antenna portion. An in-vehicle antenna, which is configured to reduce a stray capacitance generated between the taper-shaped linear delay antenna unit, a vehicle body, and a conductive member having the same potential as the vehicle body. 3. The vehicle-mounted antenna according to claim 1, wherein the electrical delay structure has a helical coil shape. 4. The vehicle-mounted antenna according to claim 1 or 2, wherein the electrical delay structure has a zigzag shape or a 99-fold shape provided on one plane. 5. The vehicle-mounted antenna according to claim 1 or 2, wherein the electrical delay structure has a columnar shape, or at least a zigzag shape or a 99-fold shape provided on a conical surface with a narrow base end. In-vehicle antenna characterized by. 6. The in-vehicle antenna according to claim 1 or 2, wherein the signal path member is formed by a linear wire portion extending from a base end of the wire delay antenna portion. antenna. 7. The vehicle-mounted antenna according to claim 1 or 2, wherein the signal path member is formed of a plate member made of a conductive material and continuously provided at a base end of the linear delay antenna unit. For antenna.