JPH0120564B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a glass antenna for an automobile, and more particularly to a glass antenna for an automobile suitable for receiving radio waves provided on a window glass of an automobile. In recent years, automobile window glasses equipped with heating stripes and antenna stripes have begun to be used.
There are two types of these so-called anti-fog glass antennas. The first type connects a heating filament and an antenna filament and uses the heating filament as an auxiliary antenna filament. In the second type, for example, as shown in FIG. 1, a heating line 2 and an antenna line 3 are provided independently on a rear window glass 1, and each function is provided separately. However, in the first type above, the received radio waves are transmitted through the ground of the heating wire,
It is necessary to prevent the direct current from flowing to the ground, and it is also necessary to prevent the direct current supplied to the heating wire from flowing to the power supply terminal of the radio receiver. For this reason, the circuit becomes very complicated, and the feeder line
When using thin coaxial cables such as 3C-2V, there was a risk of short circuit accidents caused by the direct current during anti-fog heating. Another drawback was that radio noise was generated while electricity was being applied to the heating wires. On the other hand, although the second type does not have the drawbacks of the first type, it has a major drawback of low average gain for FM broadcast radio waves and AM broadcast radio waves. In particular, when receiving FM broadcast radio waves, the directional characteristics are strong as shown in Figure 2, and depending on the direction of the car, the gain decreases and the FM
The drawback was that it became difficult to receive broadcasts. Furthermore, Figure 2 shows the gain of the conventional whip antenna.
This is a diagram of the directivity characteristics of the antenna in Figure 1 when set to OdB, where F is the fixed direction of the vehicle and the radial direction loses the arrival direction of the radio wave. Also, curve A is 80MHz, curve B is
83MHz, curve C shows the case of receiving 86MHz FM radio waves. In addition, the distance between the heating line and the upper edge of the window glass is usually 100 to 200 mm in the vertical center, but depending on the car model, it is less than 100 mm, for example, narrower than 80 mm. There are some things that impede the improvement of the reception gain of the antenna. Furthermore, in this second type, glass antennas in which the feeding point is placed on the side of the window glass have recently begun to be adopted as they have good directional characteristics (omnidirectionality), but due to the structure of the car, wiring, etc. In some cases, it may be difficult to install it on the side of a window glass. The present invention applies to a second type in which a heating strip and an antenna strip are provided independently, or an independent type without a heating strip, when the distance between the heating strip and the upper edge of the window glass is relatively narrow. Even though
The purpose is to provide a glass antenna for automobiles that has a feeding point at the upper center of the window glass, which improves the average reception gain for FM broadcast radio waves and also improves the directivity characteristics. In a glass antenna provided in a glass antenna provided in An auxiliary antenna having the function of reducing the influence of indirect waves from the vehicle body, etc. and the ability of impedance matching is connected to the short-circuit wire of the first main antenna, which consists of a short-circuit wire connecting the This is achieved by providing a point at one end of the first main antenna in the center of the window glass. The description will be given below based on the drawings. FIG. 3 shows a glass antenna according to a first embodiment of the present invention, which is particularly suitable for receiving FM broadcasting. 1 is a glass plate forming the rear window of an automobile, and 2 is a glass antenna on which the plate glass 1 is placed. There are heating stripes provided. Reference numeral 3 indicates a first horizontal filament 4 extending from the center to one side and a second horizontal filament 5 provided on one side, which are disposed laterally above the heating filament 2 on the plate glass surface. and a short-circuit wire 6 connecting their tips; 7 is the first main antenna;
This is an auxiliary antenna in which the tip of the horizontal filament connected to the short-circuit line 6 of the antenna is folded back upward. section (withdrawal point 1
0). 4, 5, and 6 show glass antennas showing the second, third, and fourth embodiments of the present invention, respectively, and FIG. 4 (second embodiment) shows the glass antennas of the first embodiment. An auxiliary antenna is provided between the horizontal filament 4 and the second horizontal filament 5, with the tip of the horizontal filament folded downward. It is arranged above the first horizontal filament 4, and FIG. 6 (fourth embodiment) shows the first horizontal filament 4.
The shape of the short-circuiting filament connecting the first horizontal filament 5 and the second horizontal filament 5 is made straight (vertical filament), and each reference numeral indicates the same as in FIG. 3 (first embodiment). 7, 8, and 9 show glass antennas showing a fifth embodiment, a sixth embodiment, and a seventh embodiment, respectively, which are modified examples of the auxiliary antenna, and the reference numerals are shown in FIG. 3 (first embodiment). ) and equivalents. When receiving FM broadcast waves, the glass antenna of the present invention has a first horizontal line extending from the center to one side over the entire FM frequency range, and a relatively short second horizontal line provided on the same side. An antenna consisting of a short-circuit line connecting the tips of the first horizontal filament and a second horizontal filament acts as a main antenna, and an auxiliary antenna having at least one horizontal filament is connected to the short-circuit line of the main antenna. It is possible to match impedance, reduce the influence of indirect waves from the vehicle body, improve directional characteristics, and improve average gain. In the glass antenna for a vehicle having such a configuration, the glass dimensions shown in FIG. 3 (first embodiment) are A = 1.080 mm, A' = 1.510 mm, and B = 595 mm.
The dimensions of each part of the antenna are M ₁ = 535mm, M ₂ = 75mm,
L=1.060mm, l=25mm, f=10mm, d=7.5mm,
e ₁ = 7.5 mm, e ₂ = 15 mm, e = 22.5 mm (e ₁ + e ₂ ), g
When the directivity characteristics of the antenna were measured with = 10 mm, h = 30 mm, and d' = 10 mm, the first result was
Characteristics as shown in FIGS. 0, 11, and 12 were obtained. Figure 10 is 80MHz, Figure 11 is 83MHz,
Figure 2 shows the directivity characteristic of the FM band at 86MHz, the solid line shows the glass antenna in Figure 3, and the dotted line shows the 3rd antenna.
The figure shows a case where only the first main antenna is used.
As is clear from Figures 10, 11, and 12, the auxiliary antenna acts to eliminate the dip in gain that is thought to be due to the influence of indirect waves when only the main antenna is used (dotted line). It can be seen that extremely good omnidirectionality can be obtained for radio waves arriving from any direction. In addition, the receiving gain of the first embodiment is expressed as a gain difference when the average gain in the FM band is set to OdB as the gain of the conventional glass antenna in Fig. 1. At 80 MHz, the receiving gain is +
It can be seen that the improvement is 4.5dB, +2.8dB at 83MHz, +2.9dB at 86MHz, and +3.4dB on average, over a wide band. In addition, when the impedance of the glass antenna of the first embodiment was measured at the feeding point (for comparison, the impedance in the case of no auxiliary antenna, that is, only the main antenna is shown in parentheses), it was found that at 80MHz, Rs (pure Resistance) = 83Ω (42Ω), Xs (reactance, +: inductive, -: capacitive) = -42Ω (-96Ω), 83MHz
At Rs = 35Ω (27Ω), Xs = −18Ω (−28
Ω), Rs = 71Ω (90Ω) at 86MHz, Xs = +
30Ω (+19Ω), the pure resistance Rs is more similar to 75Ω, and the reactance Xs is more similar to 0Ω, respectively.The auxiliary antenna matches the impedance stably over the entire FM frequency band, and fully utilizes the unique characteristics of the antenna. It can be seen that it works to make the body perform. In particular, since the glass antenna of the present invention exhibits good omnidirectionality, it can compensate for the drop in gain of a pole antenna, and is suitable for diversity reception with a pole antenna. Next, regarding the glass antennas of the second embodiment, third embodiment, and fourth embodiment shown in FIGS. 4, 5, and 6, respectively, e ₁ = e ₂ =
7.5mm, e ₃ = 15mm, e = 30mm, Figures 5 and 6
In the figure, d = 15 mm, e = 15 mm, and the other dimensions of the glass and the dimensions of each part of the antenna are the dimensions of the first embodiment shown in Figure 3 (A, A', B, M ₁ , M ₂ ,
L, l, f, e, g, h, d'), the average gain in the FM band is measured, and the gain when the gain of the antenna of the first embodiment is set to OdB. When expressed as a difference, the values shown in Table 1 were obtained.

[Table] As is clear from Table 1, it can be seen that all of the samples exhibit characteristics equivalent to or better than those of the first example. Next, regarding the modified examples of the auxiliary antenna shown in FIG. 7 (fifth embodiment), FIG. 8 (sixth embodiment), and FIG. 9 (seventh embodiment), d ₁ = d ₂ = 7.5 mm ( d = 7.5 mm for the fifth embodiment only), e ₁ = e ₂ = 7.5 mm (e ₂ = 15 mm for the fifth embodiment only), e = 15 mm (e = 22.5 mm for the fifth embodiment only), L Measure the average gain in the FM band when ₁ = L ₂ = 530 mm and the other glass dimensions and dimensions of each part of the antenna are the same as those of the glass antenna in Figure 3 (first example). When the gain of the antenna of the first embodiment is expressed as OdB, the values shown in Table 2 are obtained.

[Table] As is clear from Table 2, it can be seen that both exhibit properties equivalent to those of the first example. In the above embodiment, the effects of this embodiment were explained by specifying the dimensions of each part of the antenna and actually measuring the characteristics of the antenna. but,
The optimum dimensions for each part of the antenna may vary depending on the type of car (opening, glass installation angle, feeder length, wiring location, etc.).
When receiving FM broadcast waves at ~90MHz, the length of the first horizontal line that operates as the main antenna
For M ₁ , for example, let the wavelength of the FM broadcast frequency be λ, and (λ/4)α±(λ/20)α (α is the wavelength shortening rate of the glass antenna, approximately 0.7), that is, 450~
It is sufficient to select an appropriate optimum value within the range of 850 mm, and as for the length M ₂ of the second horizontal line, the dimensions of each part other than M ₂ are the same as in the glass antenna shown in Fig. 3 (first embodiment). Figure 13 shows the change in reception gain when changing M ₂ (: 80MHz,
:83MHz, :86MHz)
It can be seen that it is preferable to be within the range of ~300 mm. The second horizontal filament forms a stub with the first horizontal filament or the auxiliary antenna filament, or both, to improve the current flow of the received radio wave,
It is estimated that it has the effect of compensating for the shift of the resonance point in the case of wideband reception, and its placement is better than placing it above the first horizontal line as shown in Figure 5 (third embodiment). As is clear from Tables 1 and 2, it is preferable to provide a lower portion as in the other embodiments because the gain is higher. Furthermore, it has been confirmed that the shorting line e is preferably within the range of 10 to 50 mm. In this case, the shape of the shorting line is not only a straight line (vertical line) as shown in Figures 5 and 6, but also a straight line (vertical line) as shown in Figures 3, 7, 8, and 9.
It may be shaped like this, or it may be shaped like the one shown in Fig. 4. In addition, in each of the embodiments, the power feeding point and the extraction point are arranged on the vertical center line CL of the window glass, but the power feeding point and the extraction point
It has been confirmed that almost the same gain as in each of the examples can be obtained even if it is placed 100 mm left and right from the CL (the length M ₁ of the first horizontal line is also changed at the same time). Next, the auxiliary antenna, which has the function of reducing the influence of indirect waves from the vehicle body etc. and the ability of impedance matching, must have at least a horizontal line whose length L is in the range of 950 to 1160 mm.
It is also possible to add horizontal filaments of similar length, or to fold back the ends thereof, which may be selected as appropriate without being limited to the embodiments. The glass antenna of the present invention is said to be suitable when heating strips for anti-fogging are placed side by side on the rear window glass of an automobile, and when the distance between the heating strips and the edge of the window glass is narrow. The antenna wire is not limited to the above, and may be a stand-alone antenna wire without heating stripes, or may be provided on the front window glass. As described above, the glass antenna of the present invention is a separate type that is not connected to a heating strip or an independent type that does not have a heating strip, and the antenna occupies a small area on an automobile window glass, and is not subject to the disadvantageous central feeding condition. The directivity characteristics are improved over the entire FM broadcast range, and the average gain is also high.

[Brief explanation of drawings]

Figure 1 is a plan view of a conventional glass antenna, Figure 2 is a plan view of a conventional glass antenna.
The figure is a directional characteristic diagram of the antenna shown in Fig. 1, Figs. 3 to 9 are plan views of a glass antenna showing an embodiment of the present invention, and Figs. Directional characteristic diagrams of the antennas at 80MHz, 83MHz, and 86MHz, respectively. Figure 13 shows the change in reception gain when the length M ₂ of the second horizontal line constituting the first main antenna is changed in the antenna in Figure 3. FIG. DESCRIPTION OF SYMBOLS 1... Plate glass, 2... Heating line, 3 ... First main antenna, 4... First horizontal line, 5... Second horizontal line, 6... Short circuit line, 7 ... Auxiliary antenna, 8... Feeding point, 10 ...withdrawal point.

Claims (1)

[Claims] 1 In a glass antenna for a vehicle in which an antenna line is provided on the surface of a plate glass, the length (λ/4) α± extending from the longitudinal center of the plate glass to one side
(λ/20)α (λ: wavelength of the receiving frequency, α: wavelength shortening rate of the glass antenna) and a second horizontal line with a length of 40 mm to 300 mm provided on one side. and a short-circuit line connecting the tips of the first horizontal filament and the second horizontal filament; Length extending to the sides 950mm
It is equipped with a second auxiliary antenna having at least a horizontal line of ~1160 mm, and the feed point or the lead-out point to the feed point is connected to the first antenna in the longitudinal center of the plate glass.
A glass antenna for an automobile, characterized in that one end of a main antenna is provided.