JPH0119763B2 - - 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, so-called anti-fog glass antennas that are equipped with heating stripes and antenna stripes have begun to be used in the rear window glass of automobiles.

However, when such an anti-fog glass antenna receives FM broadcast radio waves, the reception gain is minimum for radio waves arriving from the front and rear of the car, and the reception gain is maximum for radio waves arriving from the side of the car. The gain difference was large, and high gain could not be obtained over the entire frequency band.
Therefore, conventional anti-fog glass antennas have strong directional characteristics and cannot be used for FM in places with weak electric field strength.
When receiving broadcast radio waves, the disadvantage is that the gain decreases depending on the direction of the car or the frequency, making it difficult to receive FM broadcasts.

The present invention eliminates such drawbacks and improves the directivity characteristics over the entire frequency range of FM broadcast radio waves.
The purpose is to provide a glass antenna for vehicles that has improved average gain and is also suitable for receiving FM broadcasts (vertical polarization) in the United States and Europe. It has a heating wire/receiving antenna with a pair of busbars at both ends provided in the heated area, and a horizontal part and a vertical part provided outside the heated area above the antenna, where the vertical part is the heating wire/receiving antenna. A T-shaped main antenna connected to the antenna, an auxiliary antenna consisting of at least one horizontal line connected to one side of the vertical part of the main antenna, and an auxiliary antenna provided on the other side of the vertical part of the main antenna. It is equipped with an impedance matching antenna, and one end of the rectangular impedance matching antenna, which is partially open or completely closed, is connected to the ground side bus bar or the topmost heating wire near it via a conductive wire, and the feed point This is achieved by providing an impedance matching antenna.

The present invention will be explained below based on the drawings.

FIG. 1 shows a glass antenna showing a first embodiment of the present invention, which has an antenna pattern particularly suitable for receiving domestic FM broadcasting (horizontally polarized waves). 1 is a plate glass forming the rear window of a car, for example; 2 is a heating filament and receiving antenna (hereinafter referred to as a heating filament).
A plurality of heating wires 3 are provided horizontally at predetermined intervals, and a pair of busbars 4 are connected at both ends thereof.
4'. The bus 4 is grounded via the high-frequency choke coil 5, and the bus 4' is grounded via the high-frequency choke coil 5' and the heating power source 6. shall be.

Note that the chiyoke coils 5, 5' may not be provided.

Next, 7 is a T-shaped main antenna having a horizontal portion 8 and a vertical portion 9, 10 is an auxiliary antenna, 11 is an impedance matching antenna, and 12 is a feeding point.

FIG. 2 and FIG. 3 show glass antennas respectively showing a second embodiment and a third embodiment of the present invention, and numerals indicate glass antennas equivalent to those in FIG. 1 (first embodiment).

In the glass antenna for vehicles of the present invention, the T-shaped antenna acts as the main antenna, the heating wire acts as a receiving antenna, and the auxiliary antenna acts to reduce the influence of reflected waves from the car body etc., so the antenna gain is increased. In addition, by providing an impedance matching antenna, the impedance of the antenna and receiver can be approximated to increase reception sensitivity, and by adjusting the tap position of the impedance matching antenna and the length of the main antenna. It is possible to improve antenna gain and frequency characteristics. In particular, the impedance matching of the glass antenna of the present invention is achieved by a novel method in which one end of the matching antenna 11 is connected to the ground side bus bar or a nearby hot wire, and an appropriate point (tap) of the impedance matching antenna is connected to the feeding point. This method allows impedance matching over a wide range of FM wave frequencies, so it is possible to improve the directivity characteristics and average gain in the entire frequency band of FM broadcasting, as shown below.

In a vehicle glass antenna with such a configuration, the dimensions of the plate glass shown in Fig. 1 are A = 1100.
mm, A'=1450mm, B=590mm, and the dimensions of each part of the antenna wire are M=510mm, L=520mm, l=80mm,
d=10mm, e=60mm, f=30mm, x=250mm, y
=520mm, s=30mm, c=20mm, g=30mm, j=
10 mm, k = 20 mm, h = 40 mm, and 13 wires were arranged at a spacing of 35 mm as the heating wire 3. The FM band directivity characteristics of the antenna were measured as shown in Figures 4 and 5. The characteristics shown in Fig. 6 were obtained. Figure 4 is 80MHz, Figure 5 is 83MHz, Figure 6 is
The solid line shows the directional characteristics of the horizontally polarized FM band at 86MHz, compared with the directional characteristics of a 1m long rear whip antenna (dotted line). As is clear from this, it can be seen that the glass antenna of this example has extremely good omnidirectionality for radio waves arriving from any direction. Moreover, the gain of the glass antenna of this example is as shown in FIGS. 4, 5, and 6.
It can be seen that the gain is similar and high compared to the whip antenna shown in the figure, but the horizontally polarized FM
The average gain of the band is 80MHz, expressed as the gain difference when the gain of a 1m long rear whip antenna is 0dB.
-7.0dB at 83MHz, -4.2dB at 83MHz,
-5.2dB at 86MHz, average -5.4dB, and the average gain of a conventional good glass antenna is about -8dB.
Therefore, it can be seen that it is extremely high. In addition, in the antenna pattern of the first embodiment, when there is no auxiliary antenna, and when there is only a conductive wire instead of the impedance matching antenna, one end of which is connected to the ground side bus bar and power is supplied to the other end, horizontally polarized wave of
When the average gain in the FM band is actually measured and expressed as the gain difference when the antenna gain of the first embodiment is 0 dB, it is - at 80 MHz without the auxiliary antenna line.
6.5 dB, -4.7 dB at 83 MHz, -5.1 dB at 86 MMHz, and -5.4 dB on average, which is the same when one end is connected to the earth side bus bar and power is fed to the other end with a conductive wire instead of an impedance matching antenna. When the antenna gain of the first embodiment is 0 dB, the gain difference is -15.3 dB at 80 MHz,
-14.2dB at 83MHz, -14.2dB at 86MHz
10.6dB, average -13.3dB, and it can be seen that the auxiliary antenna and the impedance matching antenna, especially the impedance matching antenna, greatly contribute to the gain improvement. In particular, since it sufficiently compensates for the drop in gain of the whip antenna, it is very effective as a glass antenna in a so-called diversity receiving antenna, which uses both a whip antenna and a glass antenna and switches to the antenna with the best reception condition each time.

Next, Fig. 2 shows a second embodiment in which the number of auxiliary antenna wires is two (10, 10') in the type of the first embodiment, and the dimensions shown in Fig. 2 are M = 510 mm.
L=500mm, L'=350mm, d=30mm, e=30mm, f
=30mm, x=250mm, y=520mm, S=30mm, c=
20mm, g=30mm, j=10mm, k=20mm, h=40mm
The horizontal polarization of the antenna is calculated by arranging 13 heating wires 3 with an interval of 35 mm.
When we measured the average gain in the FM band, the gain difference when the gain of a 1m long rear whip antenna was 0dB was -8.7dB at 80MHz, 83M
-6.2dB at Hz, -5.8dB at 86MHz,
It can be seen that the average value is -6.9 dB, showing characteristics similar to those of the first embodiment.

Next, the antenna of FIG. 3 showing the third embodiment of the present invention is used especially in the United States, Europe, etc. from 90MHz to 108M.
Suitable for receiving FM broadcasts (vertical polarization) at Hz, the dimensions shown in Figure 3 are M = 300.
mm, L=390mm, e=60mm, f=30mm, x=250
mm, y=500mm, S=30mm, c=20mm, g=30mm,
j = 10 mm, k = 20 mm, h = 40 mm, heating filament 3
When we measured the average gain of the vertically polarized FM band of the antenna using 13 wires arranged at a spacing of 35 mm, we found that when the gain of a 1 m long rear whip antenna was 0 dB. In terms of gain difference, -18.6dB at 90MHz, -20.1dB at 100MHz, -11.1dB at 108MHz, average -
This is 16.6 dB, which is extremely high since the average gain of a conventional glass antenna with good quality is about -20 dB. Compared to the antenna of the first embodiment, the antenna of the third embodiment has a reception harmonic number of 90MHz~
Since the frequency is as high as 108MHz, the length of the main antenna wire is shortened, and the auxiliary antenna is constructed with only a relatively short horizontal section without folding back the ends.Other than that, the dimensions and shape are almost the same, and the vertically polarized wave is When the average gain is expressed as the gain difference assuming that the antenna gain of the first embodiment is 0 dB, it is -1.4 dB at 90 MHz,
+5.9dB at 100MHz, + at 108MHz
It is 12.7dB, average +5.8dB, and is clearly an antenna suitable for receiving vertically polarized FM radio waves.

In the first and second embodiments described above, the effects of this embodiment were explained by specifying the dimensions of each part and actually measuring the characteristics of the antenna. However, the optimum dimensions of each part of the antenna wire can vary depending on the type of car (opening, glass installation angle, feeder length, wiring location, etc.), and the optimum value is 76MHz.
When receiving horizontally polarized FM waves at ~90MHz, the length M of the horizontal part that mainly operates as the main antenna is (λ/4)a±(λ/20) where the wavelength of the FM broadcast frequency is λ. a (a is the wavelength shortening rate of the glass antenna, approximately 0.7), that is, 450 to 850
For the length L of the auxiliary antenna in the range of mm,
Same as M (λ/4)a±(λ/20)a or 450
In the range of ~850mm, y of the impedance matching antenna is ((λ/8)a - (λ/20)a)
~((λ/4)a+(λ/20)a) i.e. 200~
In the range of 850 mm, the capacitance is increased for the length l of the folded part, and the impedance has an effect over a wide band with less change, but when L is the resonance length, Q (= 1/ωCR) increases. , the gain will be high, so in this case it is better not to fold back, but in other cases it is better to fold back.
In the following range, the length x of the connection point of the impedance matching antenna is in the range o to y (x = y in the case of Fig. 12 described later), and other d, e,
As for the lengths of f, S, c, g, j, k, and h, the optimum values may be selected as appropriate within a range of at least 3 mm or more so as to reduce stray capacitance with other elements adjacent in parallel.

Although the present invention has been described above using three embodiments, the antenna of the present invention is not limited to these examples, and the following modifications can be made.

(1) The T-type main antenna wire is shown in Figures 7, 8, and 9.
As shown in the figure, the horizontal portion may be composed of two or more filaments (FIG. 7), or the ends thereof may be folded back (FIG. 8). Further, the vertical portion may also be configured to have two filaments instead of one so that the T-shape forms a loop (FIG. 9).

(2) The number of horizontal lines on the auxiliary antenna is 1 in Figure 1.
It is not limited to books; it may be larger than that as shown in FIG. 2, and exhibits almost the same characteristics.

(3) The impedance matching antenna is the 10th antenna.
As shown in FIG. 11 and FIG.
It may also be shaped as shown in FIGS. 14, 14, and 15. It is presumed that what is most effective in matching the impedance here is the stub-shaped one or the one with the shape shown in Figure 13, which is smaller than a conductive wire. Since the filaments do not have any effect on impedance matching, they are treated as part of the impedance matching antenna in this specification.

Further, in the embodiments of the present invention, the glass antenna is printed and baked with a conductive paste, but it goes without saying that it may also be formed by embedding thin metal wires in the laminated window glass.

As described above, the glass antenna of the present invention is particularly characterized by impedance matching, and compared to conventional glass antennas, the directivity characteristics are improved over the entire FM frequency band, and the average gain is significantly improved. Along with vertically polarized FM
This has the great effect of improving the average gain in the frequency band as well.

[Brief explanation of drawings]

1, 2, and 3 are plan views of a glass antenna showing one embodiment of the present invention, and FIGS. 4 and 5,
Figure 6 shows the directivity characteristics of the glass antenna in Figure 1 (first embodiment) at 80MHz, 83MHz, and 86MHz (the dotted line is a 1m long rear whip antenna), Figures 7, 8, and 9. The figures show modified examples of the main antenna of the present invention, Fig. 10, Fig. 11, Fig. 12,
13, 14, and 15 show modified examples of the impedance matching antenna of the present invention. 1... Plate glass, 2... Heating wire and receiving antenna, 3... Heating wire, 4... Earth side bus bar, 4'
... Power supply side bus bar, 5, 5' ... High frequency choke coil, 6 ... DC heating power supply, 7 ... Main antenna, 8 ... Horizontal section, 9 ... Vertical section, 10 ... Auxiliary antenna, 11 ... Impedance matching antenna, 12... feeding point.

Claims (1)

[Claims] 1. In a glass antenna for a vehicle, which has a plurality of heating wire/receiving antennas each having a pair of busbars at both ends, which are provided in a heated area of plate glass, and an antenna provided above the heated area outside of the heated area, the heated area The external antenna has a horizontal part and a vertical part, and the vertical part includes a main antenna connected to the heating wire and receiving antenna, and at least one main antenna connected to one side of the vertical part of the main antenna. an auxiliary antenna consisting of one horizontal line; and a partially open or completely closed rectangular impedance matching antenna provided on the other side of the vertical portion of the main antenna; One end of the antenna is connected to the heating wire on the ground side bus bar or the topmost heating wire in the vicinity of the pair of bus bars through a conductive wire, and a lead-out point to the feeding point is provided on the impedance matching antenna. Features glass antenna for vehicles.