JPH0119766B2 - - 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 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 circuits caused by the direct current 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 directional characteristic diagram of the antenna of FIG. 1 when the antenna is set to 0 dB, 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.

The present invention provides a vehicle that improves the average gain for FM broadcast radio waves and also improves the directivity characteristics in a second type in which heating strips and antenna strips are provided independently or in a type without heating strips. The object of the present invention is to provide a glass antenna for vehicles, especially automobiles, which is provided on the window glass surface, and the antenna includes a T-shaped first antenna consisting of a horizontal part and a vertical part;
a second antenna for phase adjustment having at least one horizontal filament connected to one side of the vertical part, and a part connected to the other side of the vertical part via the horizontal filament being open or All closed rectangular impedance matching third
This is achieved by providing a third antenna for impedance matching and providing a feeding point at the third antenna for impedance matching.

The present invention will be explained below based on the drawings. FIG. 3 shows a glass antenna according to a first embodiment of the present invention, which has an antenna pattern particularly suitable for receiving FM broadcasting (horizontally polarized waves). is a heating line provided on this plate glass 1. Reference numeral 3 denotes an antenna provided above the heating wire 2 on the plate glass surface, including a T-shaped first antenna 6 consisting of a horizontal part 4 and a vertical part 5, and an antenna 1 connected to one side of the vertical part 5.
An impedance having an auxiliary second antenna 7 made of horizontal filaments of a book whose end is folded back, and a rectangular element 8 connected to the other side of the vertical part 5 and partially open or completely closed. Feed point 1 consisting of a third antenna 9 for matching
0 is provided in the impedance matching antenna 9.

FIG. 4 shows a glass antenna according to a second embodiment of the present invention, and FIG. 5 shows a glass antenna according to a third embodiment of the present invention, and the reference numerals indicate the same ones as in FIG. 3 (first embodiment).

In the vehicle glass antenna of the present invention, when receiving FM broadcast waves, the T-shaped first antenna acts as a main antenna over the entire FM frequency range, and the auxiliary antenna provided on one side of the vertical part of the T-shaped antenna acts as a main antenna over the entire FM frequency range. This antenna reduces the influence of reflected waves from the vehicle body, improves directional characteristics, and improves the average gain.In addition, by providing an impedance matching antenna, the impedance of the antenna can be adjusted to match the impedance of the feeder line (coaxial cable) (75Ω). ) to increase reception sensitivity, and improve antenna gain and frequency characteristics by adjusting the connection position (tap) of a rectangular element with a partially open or completely closed impedance matching antenna and the length of the main antenna. This is something that can be improved.

In a vehicle glass antenna with such a configuration, the glass dimensions shown in Fig. 3 are A = 1100 mm,
A' = 1450mm, B = 590mm, and the dimensions of each part of the antenna wire are M = 520mm, L = 530mm, l = 60mm, d
=10mm, e=60mm, f=30mm, x=260mm, y=
500mm, p=15mm, q=15mm, c=30mm, g=30
When the directional characteristics of the antenna were measured using mm, j=10 mm, k=20 mm, and h=40 mm, the characteristics shown in FIGS. 6, 7, and 8 were obtained. Figure 6 is 80MHz, Figure 7 is 83MHz, Figure 8 is
The solid line shows the directivity diagram of the FM band at 86MHz (the dotted line shows the directivity without a 1m long whip antenna, and the dashed-dotted line shows the directivity without the second antenna).
As is clear from FIGS. 6, 7, and 8, the glass antenna of this embodiment can provide extremely good omnidirectionality for radio waves arriving from any direction. Also, the reception gain of this example is the 6th
It can be seen that the average gain in the FM band is higher than that of the whip antennas shown in Figures 1, 7, and 8, but the average gain in the FM band is expressed as the gain difference when the gain of the conventional glass shown in Figure 1 is set to 0 dB. +5.3dB at 80MHz, 83M
+7.8dB at Hz, +2.7dB at 86MHz,
You can see that the average is +5.3dB, which is a significant improvement.

In addition, in the antenna pattern of the first embodiment, when there is no T-shaped first antenna 6, when there is no auxiliary second antenna 7, and in place of the third antenna 9 for impedance matching, a conductive wire is used. When the average gain in the FM band is actually measured when one end is connected to the vertical part and power is fed to the other end, and it is expressed as the gain difference when the gain of the antenna of the first embodiment is 0 dB, it is T type. Without the first antenna 6 (with only the auxiliary antenna 7 and impedance matching antenna 9) -12.2dB at 80MHz, 83M
-12.5dB at Hz, -9.8dB at 86MHz,
The average value is -11.5 dB, and it can be seen that the first antenna contributes very greatly to the gain improvement and is the main antenna.

Next, when there is no auxiliary second antenna 7 (when only the first antenna 6 and impedance matching antenna 9 are used), -1.1 dB at 80 MHz, 83 M
-0.7dB at Hz, -1.5dB at 86MHz,
Although there is not much difference with the average of -1.1 dB, Figures 6 and 7
If you look at the directivity diagram in Figure 8 and Figure 8 without the phase adjustment antenna 7, there is a dip in gain.
This is thought to be due to the phase difference between the direct wave and the indirect wave caused by the ground, vehicle body, etc., and the second auxiliary antenna of this application has the effect of eliminating dips, contributing to improving the directional characteristics. I know what you're doing.

Next, the third antenna 9 for impedance matching
Instead, if you connect only a conductive wire at one end to the vertical part 5 and feed power to the other end, - at 80MHz.
6.2 dB, -9.9 dB at 83 MHz, -5.3 dB at 86 MHz, and -7.1 dB on average.The third antenna contributes to gain improvement, and the impedance of the antenna when there is an impedance matching antenna is measured at the feeding point. (In parentheses it shows the impedance when there is no impedance matching antenna, that is, when power is supplied only by a conductive wire.) At 80MHz, Rs (pure resistance) = 227Ω
(108Ω), Xs (reactance, + is inductive, - is capacitive) = -61Ω (+296Ω), Rs at 83MHz =
93Ω (504Ω), Xs = -99Ω (-486Ω), at 86MHz, Rs = 83Ω (133Ω), Xs = -13Ω (-241Ω), so the pure resistance Rs is close to 75Ω, and the reactance |Xs| It can be seen that the small, third antenna functions to stably match the impedance over the entire FM frequency band and fully utilize the unique characteristics of the antenna.

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, the glass antenna shown in FIG. 4, which shows the second embodiment of the present invention, is the same as the antenna of the first embodiment except that the stub of the impedance matching antenna is open. When the average gain was actually measured and expressed as a gain difference when the gain of the antenna of the first embodiment was 0 dB, it was -0.6 dB at 80 MHz and -0.6 dB at 83 MHz.
1.5dB, +1.4dB at 86MHz, and -0.2dB on average, showing similar characteristics.

Next, the glass antenna shown in FIG. 5, which shows the third embodiment of the present invention, is made by adding one antenna with an open end as an auxiliary antenna to the antenna of the first embodiment, making it two, L' = 500 mm. Assuming that the other dimensions (glass and antenna) are the same, we actually measured the average gain in the FM band, and expressed it as the gain difference when the gain of the antenna of the first example was 0 dB. At 80 MHz, - 0.7dB, + at 83MHz
1.8dB, +0.4dB at 86MHz, and +0.5dB on average, indicating similar or better characteristics.

In the above example, the effects of this example were explained by specifying the dimensions of each part of the antenna wire 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.).
When receiving FM waves between 76MHz and 90MHz,
Regarding the length M of the horizontal part that mainly operates as the main antenna, let the wavelength of the FM broadcast frequency be λ,
(λ/4) α±(λ/20) α (α is the wavelength shortening rate of the glass antenna, approximately 0.7) In other words, in the range of 450 to 750 mm, the length L of the second antenna is M
Same as (λ/4)α±(λ/20)α i.e. 450～
In the range of 750 mm, y of the impedance matching antenna is ((λ/8) α - (λ/20) α) ~
((λ/4)α+(λ/20)α) i.e. 200 to 750
In the range of mm, the length l of the folded part of the second antenna increases the capacitance, and the impedance has an effect over a wide band with less change, but when L is the resonance length, Q(=1/ ωCR) becomes high and the gain increases, so in this case it is better not to fold back, but in other cases it is better to fold back.Within a range of 300 mm or less, the length x of the connection point of the impedance matching antenna is o～y(x=
In the case of Fig. 13 described below), other d, e, f, p, q, c, g, j, k, h
Regarding the length, the optimum value 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) As shown in Figures 9, 10, and 11, the T-shaped main antenna wire may consist of two or more wires in its horizontal portion (Figure 9), and its ends The portion may be folded back (FIG. 10). Further, the vertical portion may also be configured to have two filaments instead of one so that the T-shape forms a loop (FIG. 11).

(2) The number of horizontal stripes of the auxiliary antenna is not limited to one as shown in FIG. 1, but may be greater than that as shown in FIG. 5, and almost the same characteristics will be obtained.

(3) The impedance matching antenna is shown in Figure 12.
As shown in FIG. 13, there are of course stub-shaped ones as in the embodiment, as well as FIGS. 14, 15,
It may be shaped as shown in FIG. 16. It should be noted that what is most effective in matching the impedance here seems to be things other than conductive wires, such as stub-shaped ones or 〓-shaped ones in Figure 14, but the conductive wires connected to these Since the strips 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.

Further, in the embodiment of the present invention, an anti-fogging antenna having the heating strip 2 is shown, but the heating strip may not be provided, and the antenna of the present invention may be provided on the windshield.

As described above, the glass antenna of the present invention has the characteristics of a separate type that does not connect with the heating wire, and also eliminates the disadvantages of the separate type, has a high average gain over the entire FM frequency band, and has improved directivity characteristics. It has the remarkable effect of being able to do the following.

[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 in Figure 1, Figures 3, 4 and 5 are plan views of a glass antenna showing an embodiment of the present invention, and Figures 6, 7 and 8 are Third
80MHz, 83MHz, respectively in the figure (first example)
Directional characteristic diagram at 86MHz (the dotted line is a 1m long rear whip antenna, the dashed line is the antenna of the first embodiment without the second auxiliary antenna), Figures 9, 10, 11 The figure shows a modification of the first antenna of the invention, and FIGS. 12, 13, 14, 15, and 16 show modifications of the third antenna of the invention. DESCRIPTION OF SYMBOLS 1... Plate glass, 2... Heating line, 3 ... Antenna, 4... Horizontal part, 5... Vertical part, 6... First
antenna, 7...second antenna, 9...third antenna
antenna, 10... feeding point.

Claims (1)

[Claims] 1. In a glass antenna for a vehicle in which an antenna strip is provided on a plate glass surface, the antenna includes a T-shaped first antenna consisting of a horizontal part and a vertical part, and at least one antenna connected to one side of the vertical part. a second auxiliary antenna consisting of a horizontal line, and a third antenna for impedance matching in a partially open or completely closed rectangular shape connected to the other side of the vertical part via a horizontal line. A glass antenna for a vehicle, characterized in that the third antenna for impedance matching is provided with an extraction point to a feeding point.