JPH07193418A - On-vehicle antenna - Google Patents

Abstract

PURPOSE:To obtain a satisfactory antenna characteristic by matching an applied frequency after the appearance of a vehicle is satisfied and to prevent wind whistle by connecting and constituting the conductive core wire of a specified length and a spiral conductor in a unique form. CONSTITUTION:In an antenna element 3, a straight line conductive core wire 31 exists at the center part and the outer peripheral part of this core wire 31 is covered by insulating coating 32. On the outer peripheral part of this coating 32, a spiral conductor 33 is spirally wound up by prescribed pitch over the area from the tip part of the core wire 31 to the vicinity of a base end part. The tip part 33a of this conductor 33 and the tip part 31 a of the core wire 31 are short-circuited by a short-circuiting element means 34. The base end part of the core wire 31 and the base end part of the conductor 33 is kept open. When the wavelength of a using frequency band is defined as lambda, the length of the core wire 31 is defined as M, the length of the conductor 33 is defined as N, the inductance of the conductor 33 is defined as L and the correction constant of the electrical length by this L is defined as K, for each part of the element 3, the electrical length H of the element 3 is set to satisfy H=M +N+KL=lambda/4.

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 mounted on a vehicle such as a passenger car.

[0002]

2. Description of the Related Art As a conventional antenna of this type, there is an antenna in which a glass fiber with a core wire having a length of about 400 mm is used as a mast. This antenna has a resonance frequency of 16
It is about 0 to 170 MHz, and has characteristics as shown in the Smith chart shown in FIG. 3A and the SWR characteristic shown in FIG. As is clear from (a) and (b) of FIG. 3, this antenna has a frequency band (8
It was completely inconsistent for 8 to 108 MHz).

[0003]

As described above, the conventional vehicle-mounted antenna, even if the characteristics of the antenna are considerably deteriorated, mainly for the reasons of appearance of the vehicle and the purpose of avoiding various obstacles during traveling, for example, There is an increasing tendency to set the total length of the antenna element to about 400 mm.

However, even if the antenna is mounted on a vehicle where the design reason is given priority, if the antenna element length does not match the applied frequency at all, the original function of the antenna cannot be exhibited.

It is a problem that a so-called wind noise generated while the vehicle is traveling at high speed is transmitted as noise into the vehicle and causes discomfort to a person in the vehicle.

The object of the present invention is to meet the requirements of the appearance of the vehicle, to obtain the antenna characteristics which are matched with the applied frequency and to be sufficiently satisfied. An object of the present invention is to provide a vehicle-mounted antenna capable of significantly suppressing wind noise.

[0007]

In order to solve the above problems and achieve the object, the vehicle-mounted antenna of the present invention is constructed as follows.

(1) A linear conductive core wire, an insulating coating covering the outer periphery of the conductive core wire, and an outer periphery of the insulating coating covering a region from the tip end portion to the base end portion of the conductive core wire. A spiral conductor wound in a spiral shape and short-circuiting means for short-circuiting the tip of the spiral conductor and the tip of the conductive core wire are provided.

(2) The on-vehicle antenna according to (1) above, wherein the wavelength of the radio wave in the frequency band used is λ, the length of the linear conductive core wire is M, and the length of the spiral conductor. N, the inductance of this spiral conductor is L,
When the correction constant of the electrical length due to the inductance L is K, each part is set so as to satisfy the relational expression M + N + KL = λ / 4.

[0010]

As a result of taking the above-mentioned means, the following effects occur.

(1) The total length of the antenna element is, for example, 40
Since it can be formed to a thickness of about 0 mm, the requirements for the appearance of the vehicle can be satisfied in the same manner as in the past, and the electric length of the antenna element can be made to be a length adapted to the applied frequency by the action of the spiral conductor. All the antennas can be matched and sufficiently satisfactory antenna characteristics can be obtained. Further, since the spiral conductor wound in a spiral shape is provided on the outer circumference of the antenna element, the spiral conductor causes disturbance of the air and diffuses the low-pressure region that is about to occur in the lee of the antenna element. . As a result, so-called wind noise due to the antenna element generated while the vehicle is traveling is significantly suppressed.

(2) Each part of the antenna element is M + N + K
Since the relational expression L = λ / 4 is satisfied, the action described in (1) above is commonly generated not only for FM broadcast waves but also for any applicable frequencies.

[0013]

1 (a) and 1 (b) are side views showing the entire structure of an on-vehicle antenna according to an embodiment of the present invention with a part thereof broken away, and a structure of a main part of the antenna. It is a side view which fractures | ruptures and shows.

In FIGS. 1 (a) and 1 (b), 1 is a mounting base for mounting on the vehicle body, and the antenna element holding portion 2 of this mounting base 1 is provided with a base end portion of the antenna element 3. It is set up. The antenna element 3 has a linear conductive core wire 31 having a length of about 400 mm at the center thereof, and the outer circumference of the conductive core wire 31 is covered with an insulating coating 32 made of glass fiber. A spiral conductor (coil) 33 is spirally wound around the outer periphery of the insulating coating 32 at a predetermined pitch P over a region from the tip of the conductive core wire 31 to the vicinity of the base end. The tip 33a of the spiral conductor 33 and the tip 31a of the conductive core wire 31 are short-circuited by a short-circuiting means (joining means) 34 such as soldering.
It should be noted that the space between the base end of the conductive core wire 31 and the base end of the spiral conductor 33 is kept open. At the tip of the antenna element 3, a protective top cover 35 made of synthetic resin or the like is fitted.

In each part of the antenna element 3, the wavelength of the radio wave in the used frequency band is λ, and the linear conductive core wire 3 is used.
When the length of 1 is M, the length of the spiral conductor 33 is N, the inductance of the spiral conductor 33 is L, and the correction constant of the electrical length by the inductance L is K,
The electrical length H of the antenna element 3 is set so as to satisfy the relational expression H = M + N + KL = λ / 4.

As for the inductance L of the spiral conductor 33, assuming that the winding inner diameter of the spiral conductor 33 is D, the wire thickness is d, the number of turns is α, and the total length of the winding (the length of the spiral conductor 33) is N. , L = K1 αD + K2 α ² D Where K1 is a constant that depends on d / D,
K2 is a constant that depends on N / D.

2 (a) and 2 (b) are diagrams showing the results of actual measurement of the characteristics of the vehicle-mounted antenna of the above embodiment, (a) is a Smith chart, and (b) is a SWR characteristic curve diagram. . As shown in (a) and (b) of FIG. 3, the vehicle-mounted antenna of this embodiment has a resonance frequency adapted to the frequency band 88 to 108 MHz of the FM broadcast wave,
It is clear that they are well aligned.

When the conventional on-vehicle antenna having a total length of about 400 mm and the antenna of this embodiment were compared in terms of dipole ratio, the following results were obtained.

"In the case of the conventional antenna" Frequency 87.9 MHz ... 59.5 dB Frequency 98.1 MHz ... 46.5 dB Frequency 107.1 MHz ... 65.0 dB "In case of the antenna of this embodiment" Frequency 87.9 MHz ... 54. 0 dB frequency 98.1 MHz ... 43.0 dB frequency 107.1 MHz ... 65.0 dB When both ends of the conductive core wire 31 and the spiral conductor 33 are opened, the same characteristics as those of the conventional example are shown and both are short-circuited. In this case, the frequency is 8 compared to the conventional example.
It was confirmed that the value is slightly improved only when the frequency is 7.9 MHz. Thus, it has been found that the antenna constructed as in this embodiment has a considerably improved sensitivity as compared with the conventional antenna.

The configuration and operational effects of the above-mentioned embodiment are summarized as follows.

(1) The vehicle-mounted antenna shown in the embodiment is
A straight conductive core wire 31, an insulating coating 32 that covers the outer periphery of the conductive core wire 31, and a spiral winding around the outer periphery of the insulating coating wire 32 from the distal end portion to the proximal end portion of the conductive core wire 31. The spiral conductor 33 is provided, and a short-circuit means 34 such as soldering for short-circuiting the tip of the spiral conductor 33 and the tip of the conductive core wire 31 is provided.

Therefore, since the total length of the antenna element 3 can be formed to a length of, for example, about 400 mm, the requirements for the external appearance of the vehicle can be satisfied in the same manner as in the conventional case, and the function of the spiral conductor 33 causes the antenna element 31 to be electrically Since the length can be adapted to the applied frequency, matching with the required frequency can be achieved and sufficiently satisfactory antenna characteristics can be obtained. The spiral conductor 33 spirally wound around the outer periphery of the antenna element 3 disturbs the flow of air hitting the antenna element 3, and as a result, the low-pressure region that is about to be generated in the lee of the antenna element 3 is diffused. It will be. Thus, the so-called wind noise caused by the antenna element 3 generated while the vehicle is traveling is significantly suppressed.

(2) The vehicle-mounted antenna shown in the embodiment is
The wavelength of the radio wave in the operating frequency band is λ, the length of the linear conductive core wire 31 is M, the length of the spiral conductor 33 is N, the inductance of the spiral conductor 33 is L, and the electrical length by the inductance L is The correction constant of K
Then, each part is set so as to satisfy the relational expression M + N + KL = λ / 4.

Therefore, each part of the antenna element 3 is
By setting so that the relational expression + N + KL = λ / 4 is satisfied, the function and effect described in (1) are commonly generated not only for FM broadcast waves but also for any applicable frequencies.

(3) The vehicle-mounted antenna of the above embodiment includes the following modifications.

A. A so-called telescopic on-vehicle antenna is applied instead of the on-vehicle antenna that is mounted and fixed on the vehicle body.

B. It is applied to an antenna having a structure in which the mounting angle is variable, instead of the antenna in which the antenna mounting angle is fixed.

[0028]

According to the present invention, it is possible to satisfy not only the appearance requirements of a vehicle but also antenna characteristics that match the applied frequency and are sufficiently satisfied. It is possible to provide a vehicle-mounted antenna capable of significantly suppressing the so-called wind noise.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an in-vehicle antenna according to an embodiment of the present invention, FIG. 1A is a side view showing a part of the entire antenna, and FIG. The side view fractured and shown.

FIG. 2 is a diagram showing a result of actual measurement of characteristics of the vehicle-mounted antenna according to the above-described embodiment, in which (a) is a Smith chart,
(B) is a SWR characteristic curve diagram.

FIG. 3 is a diagram showing a result of actually measuring characteristics of a vehicle-mounted antenna according to a conventional example, in which (a) is a Smith chart;
(B) is a SWR characteristic curve diagram.

[Explanation of reference numerals] 1 ... Mounting base 2 ... Antenna element holding portion
3 ... Antenna element 31 ... Conductive core wire 32 ... Insulation coating (glass fiber) 33 ... Spiral conductor 34 ... Short-circuit means 35 ...
Protective top cover

Claims (2)

[Claims] 1. A linear conductive core wire, an insulating coating covering the outer periphery of the conductive core wire, and a spiral extending from the tip to the base end of the conductive core wire on the outer periphery of the insulating coating. An in-vehicle antenna, comprising: a spiral conductor wound in a spiral shape; and a short-circuit means for short-circuiting a tip portion of the spiral conductor and a tip portion of the conductive core wire. 2. The wavelength of the radio wave in the frequency band used is λ, the length of the linear conductive core wire is M, the length of the spiral conductor is N, the inductance of the spiral conductor is L, and the inductance L is The correction constant of electrical length is K
2. The vehicle-mounted antenna according to claim 1, wherein each part is set so as to satisfy the relational expression M + N + KL = λ / 4.