JPH0120563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glass antenna for a vehicle, and more particularly to a glass antenna for a vehicle 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 wire and an antenna wire, and uses the heating wire as an auxiliary antenna wire. 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 or 1.5C-2V, there was a risk of short circuits caused by the direct current generated during anti-fog heating. Another drawback was that radio noise was generated while the heating wire was being energized.

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 FIG. 1 in OdB, where F indicates the fixed direction of the vehicle and the radial direction indicates the arrival direction of radio waves. Also, curve A is 80MHz, curve B is
83MHz, curve C shows the case when 86MHz FM radio waves are received.

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, the distance between the heating strip and the upper edge of the window glass is as narrow as 100 mm or less, for example, 80 mm. There are some things that impede the improvement of reception gain. In addition, in recent years, glass antennas with the feeding point located on the side of the window glass have begun to be adopted as they have good directional characteristics (omnidirectional) in this second type, but depending on the structure of the car, wiring, etc. In some cases, it may be difficult to provide it on the side of the window glass.

The present invention provides a second type in which the heating strip and the antenna strip are provided independently, or a type without the heating strip, in which the distance between the heating strip and the upper edge of the window glass is relatively narrow. The purpose of the present invention is to provide a vehicle glass antenna with a feed point located at the upper center of the window glass, which improves the average reception gain for FM broadcast radio waves and also improves the directional characteristics. In the glass antenna installed in the window glass, the main antenna is a U-shaped antenna in which two parallel wires are horizontally arranged from the vertical center of the window glass to one side and connected by a vertical line at the end. This is achieved by connecting the auxiliary antenna to the vertical line of the main antenna and providing a feed point or a lead-out point to the feed point generally on the open side of the main antenna.

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. 3 is two parallel lines 4 (upper side) arranged horizontally above the heating line on the plate glass surface;
4' (lower side) and a vertical line connecting their ends 5
6 is an auxiliary antenna connected to the lower end of the vertical line 5 of the first main antenna 3 , the feeding point 7 is provided at the vertical center of the upper part of the window glass, and the conductive wire 8 It is connected to the extraction point 9 at the end of the upper parallel line 4 on the open side of the main antenna.

FIG. 4 shows a glass antenna showing a second embodiment of the present invention, in which an auxiliary antenna 6 is connected to the upper end of the vertical line 5 of the main antenna 3 , and the symbols are the same as in FIG. 3 (first embodiment). show something

FIG. 5 shows a glass antenna showing a third embodiment of the present invention, in which the lead-out point to the feeding point is the end of the lower parallel line 4' on the open side of the main antenna, and the auxiliary antenna 6
is connected to the middle part of the vertical line 5 of the main antenna 3 , and the reference numerals indicate the same ones as in FIG. 3 (first embodiment).

FIGS. 6 and 7 show glass antennas showing a fourth embodiment and a fifth embodiment, respectively, which are modified examples of the auxiliary antenna, and the reference numerals indicate the same ones as in FIG. 3 (first embodiment).

When the glass antenna of the present invention receives FM broadcast waves, the U-shaped antenna acts as the main antenna over the entire FM frequency range, and by connecting the auxiliary antenna to the vertical line of the main antenna, indirect waves from the vehicle body, etc. This makes it possible to reduce the influence caused by this, improve the directivity characteristics, and also improve the average gain.

In the vehicle glass antenna having such a configuration, the glass dimensions shown in FIG. 3 (first embodiment) are A=1.060 mm, A′=1.510 mm, and B=595 mm.
The dimensions of each part of the antenna are M ₁ = 260mm, M ₂ = 245mm,
N=265mm, L=1.010mm, f=10mm, d=15mm,
When the directional characteristics of the antenna were measured using e=15 mm, g=10 mm, and h=30 mm, the characteristics shown in FIGS. 8, 9, and 10 were obtained. Figure 8 shows the directivity characteristics of the FM band at 80MHz, Figure 9 at 83MHz, and Figure 10 at 86MHz.The solid line shows the glass antenna in Figure 3, and the dotted line shows the case of only the main antenna in Figure 3. Figure 8, Figure 9,
As is clear from Figure 10, 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 even for radio waves. In addition, the receiving gain of the first embodiment is expressed as the 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.
+4.6dB at 80MHz, + at 83MHz
2.0dB, +3.9dB at 86MHz, average 3.5dB, which shows improvement over a wide band.

In addition, when the impedance of the glass antenna of the first embodiment was measured at the feeding point, at 80MHz.
Rs (pure resistance) = 88Ω, Xs (reactance, + is inductive, - is capacitive) = -45Ω, Rs at 80MHz
=34Ω, Xs=-20Ω, Rs=72Ω at 86MHz,
In both cases, Xs = +47Ω, the pure resistance Rs is approximated to 75Ω,
Moreover, the reactance Xs is close to 0Ω, indicating that this glass antenna performs the function of stably matching the impedance over the entire FM frequency range and fully demonstrating the unique characteristics of the antenna. 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 antenna of the second embodiment shown in FIG. 4 and the third embodiment shown in FIG. (M ₁ = 245 mm, M ₂ = 260 mm only in Figure 5), the average gain in the FM band was measured, and the gain of the antenna of the first embodiment was determined to be OdB. In terms of the gain difference when
1.4dB, +0.1dB at 83MHz, -0.3dB, 86M
+0.6dB, +0.1dB, average +0.3dB, + at Hz
It can be seen that the result is 0.4dB, showing equivalent characteristics.

Next, FIG. 6 (fourth embodiment) and FIG. 7 (fifth embodiment) show modified examples of the phase adjustment antenna, where L ₁ = 480
mm, L ₂ = 530 mm, d ₁ = 7.5 mm, d ₂ = 7.5 mm, and the other glass dimensions and antenna dimensions are the same as those of the glass antenna in Figure 3 (first embodiment). The average gain in the FM band is measured by a device, and when the gain of the antenna of the first embodiment is OdB, the gain difference is -0.4 dB at 80 MHz, -0.4 dB at 83 MHz, and +1.0 dB at 83 MHz. ,+
It can be seen that at 0.6 dB and 86 MHz, they are -0.8 dB, -0.7 dB, and average -0.1 dB, -0.2 dB, showing equivalent characteristics.

In the above embodiment, the effects of this embodiment were explained by specifying the dimensions of each part of the antenna wire and actually measuring the characteristics of the antenna. However, the dimensions of each part of the antenna wire depend on the type of car (opening,
The optimum value may vary depending on the angle of glass installation, feeder length, wiring location, etc.
When receiving FM broadcast waves between Hz and 90MHz,
Regarding the length M ₁ of the upper parallel line and the length M ₂ of the lower parallel line of the main antenna, make M ₂ by keeping the dimensions of each part the same except M ₂ in the glass antenna pattern of Fig. 3 (first embodiment). Figure 11 shows the change in reception gain when changing the gain (: 80MHz, : 83MHz,
:86MHz) For _M2 , as is clear from
When the wavelength of the FM broadcast frequency is λ (λ/8)
It can be seen that it is preferably within the range of α to (λ/24)α (α is the wavelength shortening rate of the glass antenna, 0.7), that is, 150 to 400 mm. Regarding M ₁ , the dimensions other than M ₁ are the same as in the glass antenna pattern in Figure 3, and M ₁ is 150 mm (in this case, the feeding point is 110 mm to the right from the vertical center line CL of the window glass). Even if the feeding point is changed to 410mm (in this case, the feeding point is 150mm to the left of the center line CL), the gain is almost the same as the glass antenna in Figure 3 (first embodiment) (Gain comparison with Figure 3: +0 .2dB to -0.5dB), and as with _M2 , the optimum value can be selected as appropriate within the range of 150 to 400 mm. In this case, M ₁ and M ₂ do not necessarily have to be equal, and (M ₁ -M ₂ ) may have a difference within a range of approximately 0 to 165 mm, preferably within a range of 0 to 85 mm.

Also, the length Θ of the vertical line of the main antenna is 5
It has been confirmed that the antenna exhibits characteristics (gain comparison with FIG. 3: −0.2 dB to +0.3 dB) that are almost equivalent to those of the glass antenna in FIG. 3 (first embodiment) within the range of ~50 mm.

Next, it is better for the auxiliary antenna to have a total length of at least 1000 mm, and therefore it is better to secure the length by folding it back on the vertical side of the main antenna. It can be selected as appropriate.

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 the heating wire, occupies a small antenna area on an automobile window glass, and has directivity characteristics over the entire FM broadcast area even under the disadvantageous condition of central feeding. This has remarkable effects in that the average gain is improved 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 7 are plan views of a glass antenna showing an embodiment of the present invention, and Figs. FIG. 11 is a diagram showing the directivity characteristics of the antenna at 80 MHz, 83 MHz, and 86 MHz, respectively, and is a diagram showing the change in reception gain when the length M ₂ of the lower parallel line of the main antenna is changed in the antenna of FIG. 3. DESCRIPTION OF SYMBOLS 1...Plate glass, 2...Heating wire, 3 ...Main antenna, 4, 4'...2 parallel lines, 5...Vertical line, 6 ...Auxiliary antenna, 7...Feeding point, 8...Conducting wire, 9...Leading point.

Claims (1)

[Claims] 1 In a glass antenna for a vehicle in which an antenna line is provided on the plate glass surface, the length from the longitudinal center of the plate glass to one side is (λ/24) α ~ (λ/
8) A U-shaped main antenna with two parallel lines of α (λ = wavelength of the receiving frequency, α = wavelength shortening rate of the glass antenna) arranged horizontally and one end of which is connected by a vertical line. An auxiliary antenna is connected to the vertical line of the main antenna, extends to one side, is folded back at the part, and extends at least horizontally to the other side, and the feed point or the lead-out point to the feed point is connected to the main antenna. A glass antenna for a vehicle, characterized in that it is provided at one end of an open side.