JPH0147045B2 - - 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 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 longitudinal center.
Depending on the vehicle model, there are antennas that are as narrow as 100 mm or less, for example, about 80 mm, that is, the area occupied by the antenna is small, which hinders the improvement of the reception gain of the glass antenna. 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 heating stripes and antenna stripes are provided independently, and even if the distance between the heating strip and the upper edge of the window glass is relatively narrow, the average reception of FM broadcast waves can be improved. The purpose is to provide a glass antenna for vehicles that has a feeding point at the upper center of the window glass and has improved gain and directional characteristics. The first one whose length is (λ/2)α±(λ/20)α
A second antenna line with a length of (λ/8)α to (λ/4)α, or a third antenna line, is installed at a predetermined interval below the main antenna line and the main antenna, respectively. This is achieved by connecting these antenna lines at one end and providing a feed point or a lead-out point to the feed point in the center of the first main antenna line.

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 a particularly suitable antenna pattern for receiving FM broadcasting. 1 is a glass plate forming the rear window of a car, and 2 is a glass antenna on the glass plate 1. It is a heating strip provided in the. Reference numeral 3 indicates a first antenna wire provided horizontally above the heating line 2 on the plate glass surface, and reference numeral 4 indicates a second antenna wire provided laterally at a predetermined interval below the first antenna wire 3. In the antenna line, the first and second antenna lines are connected at one end thereof by a vertical line 5, and an extraction point 7 to a feed point 6 is provided in the central part of the first antenna line, The extraction point 7 is connected to the power feeding point 6 by a conductive wire 8 .

FIG. 4 shows a glass antenna showing a second embodiment of the present invention, in which a third antenna line 9 is arranged horizontally below the first antenna line 3 and above or below the second antenna line 4 at a predetermined interval. Other symbols indicate the same as in FIG. 3 (first embodiment).

FIGS. 5 and 6 are glass antennas that are modifications of the second embodiment and show the third and fourth embodiments, respectively, and the reference numerals indicate the same ones as in FIG. 4 (second embodiment).

When the vehicle glass antenna of the present invention receives FM broadcast waves, the first antenna line serves as the main antenna over the entire FM frequency range, and strictly speaking, the length of the main antenna is M ₁ (connected to the second antenna line). (from one end of the side that is connected to the extraction point to the extraction point) +M ₂ (from the extraction point to the other end)
When _M2 acts as a main antenna as described later, the impedance is matched by connecting one end of the second antenna wire to the end of the first antenna wire with a vertical line, and furthermore, the vehicle body, It is possible to improve directivity characteristics by reducing the influence of indirect waves from the earth, buildings, human bodies, etc., and also to improve average gain.

Further, a third antenna line is provided below the first antenna line and above or below the second antenna line,
By connecting one end to one end of the first and second antenna wires via a vertical line, it is presumed that it works together with the second antenna wire to reduce the influence of indirect waves and at the same time match impedance. .

In a vehicle glass antenna with such a configuration, the glass dimensions shown in Figure 3 are A=1060.
mm, A′ = 1510mm, B = 595mm, and the dimensions of each part of the antenna are M ₁ = M ₂ = 520mm, L = 450mm, f = 10
mm, e=30mm, g=10mm, h=30mm, and the glass dimensions shown in Figure 4 are A=1060mm, A'=1510mm,
Assuming B = 595 mm, the dimensions of each part of the antenna are M ₁ = M ₂
=520mm, K=1050mm, L=450mm, f=10mm,
When we measured the directivity characteristics of the antenna using d' = e' = 15 mm, g = 10 mm, and h = 30 mm, we obtained the characteristics shown in Figures 7, 8, and 9. . Figure 7 is 80MHz, Figure 8 is 83MHz, Figure 9 is
In the directivity diagram of the FM band at 86MHz, the dashed line shows the characteristics of the glass antenna in Fig. 3 (first embodiment), and the solid line shows the characteristics of the glass antenna in Fig. 4 (second embodiment) (the dotted line shows the characteristics of the glass antenna in Fig. 4 (second embodiment)). ). As is clear from FIG. 7, FIG. 8, and FIG. 9, both the antennas of the first and second embodiments are
The antenna works to eliminate the dip in gain that is thought to be caused by the influence of indirect waves when only the main antenna is used (dotted line), and it provides an extremely good response to radio waves arriving from any direction. It can be seen that omnidirectionality is obtained. In addition, the reception gain of the first and second embodiments is the average gain in the FM band, which is OdB higher than the gain of the conventional glass antenna shown in Figure 1.
The gain difference when 80MHz is +4.2dB, +5.7dB, 83MHz is +1.3dB,
+2.2dB, +4.9dB, +4.6dB at 86MHz, average +3.5dB, +4.2dB, which shows improvement over a wide band.

In addition, when the impedance of the glass antenna of the first example and the second example was measured at the feeding point (the impedance of the antenna of the second example is shown in parentheses), at 80MHz, R _S (pure resistance) = 138Ω
(148Ω), X _S (reactance, + is inductive, - is capacitive) = -64Ω (-29Ω), R _S = 74Ω at 83MHz
(89Ω), X _S = -82Ω (-77Ω), R _S at 86MHz
= 61 Ω (82 Ω), X _S = −43 Ω (−49 Ω), and in both cases, the pure resistance _R
X _S is approximated to O, and the second antenna line or the second antenna line and the third antenna line are FM
It can be seen that it works by stably matching the impedance over the entire frequency range and fully demonstrating the unique characteristics of the antenna.

In particular, the glass antenna of the present invention exhibits good omnidirectionality and can compensate for the drop in gain of a pole antenna, making it suitable for diversity reception with a pole antenna.

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 specificity 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 glass installation angle, feeder length, wiring location, etc.
When receiving FM broadcast waves between Hz and 90MHz,
For _M2 , which operates as the main antenna, for example, if the wavelength of the FM broadcast frequency is λ, then (λ/4)α±
(λ/20) α (α is the wavelength shortening rate of the glass antenna, approximately 0.7), that is, an optimal value may be appropriately selected in the range of 450 to 850 mm. _M1 does not necessarily have to be within the same range as _M2 , but for aesthetic reasons or as a third antenna line (length K should be longer as described later)
The same range as M ₂ (λ/4) α±
(λ/20) α is preferable. In other words, the length of the main antenna M ₁ + M ₂ is (λ/2) α± (λ/20)
It is preferable that it be α. In this case, the power supply point or the point of extraction to the power supply point is the vertical center line of the window glass.
Figure 5 is not limited to the CL,
As shown in FIG. 6, it may be offset within a range of approximately 150 mm to the left and right from the center line CL. The average gain of the glass antenna in the case of Fig. 5 was actually measured and compared with the second example, it was -1.7 dB at 83 MHz and -1.7 dB at 83 MHz.
It has been confirmed that the characteristics are almost the same at 0.8dB, +1.2dB at 86MHz, and -0.4dB on average.

Next, regarding the length L of the second antenna wire, the figure showing the reception gain when L is changed while keeping all dimensions other than L the same in the glass antenna pattern of FIG. 4 (second embodiment), Figure 10 ( _XL :
80M _Z , Y _L : 83M _Z , Z _L : 86M _Z
It can be seen that it is preferable to be within the range of 650 mm.

Next, regarding the length K of the third antenna wire, see Figure 11, which shows the gain when K is changed while keeping all dimensions other than K the same in the glass antenna pattern of Figure 4 (second embodiment). Figure ( _XK : 80MHz,
Y _K : 83M _Z , Z _K : 86MHz),
Even without the third antenna line itself (in the case of K=O), there is no big difference compared to the case where K is large, but
It can be seen that when the third antenna is added, the gain improves as K becomes larger. Therefore, the length K may be ensured by folding back the end of the third antenna wire as shown in FIG. 6 or by providing a branch part in the middle as shown in FIG. Further, the second and third antennas may be upside down and the second antenna may be provided above the third antenna.

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 a car 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 6 are plan views of a glass antenna showing one embodiment of the present invention, and Figs. 7, 8, and 9 are diagrams of the first embodiment. ,
Directional characteristic diagrams of the second embodiment at 80MHz, 83MHz, and 86MHz, respectively. Figure 10 is a diagram showing the change in reception gain when the length L of the second antenna wire is changed. Figure 11 is a diagram showing the change in reception gain when the length L of the second antenna wire is changed. FIG. 6 is a diagram showing a change in reception gain when the length K of the line is changed. DESCRIPTION OF SYMBOLS 1... Plate glass, 2... Heating filament, 3... First antenna line, 4... Second antenna line, 5... Vertical line, 6
... Feeding point, 7... Leading point, 9... Third antenna line.

Claims (1)

[Claims] 1. A first main antenna wire is provided above the heating filament of the plate glass and outside the heated area, and a second antenna wire is provided below the main antenna at a predetermined interval, and the first and second antenna wires are provided horizontally. In a glass antenna for a vehicle in which one end of the antenna wire is connected by a vertical line, a feeding point or an extraction point to the feeding point is provided in the center of the first antenna wire, and the length of the first main antenna wire is ( λ/2)α±(λ/20)α, second
Let the length of the antenna wire be (λ/8)α~(λ/
4) A glass antenna for vehicles characterized by α (λ: wavelength of the received FM broadcast wave, α: wavelength shortening rate of the glass antenna).