GB2273206A - Antenna for windows of automobiles - Google Patents

Abstract

A rear window antenna (1) is disposed on a glass panel (2) of an automobile above a plurality of horizontally disposed heating electric wires (3). The antenna includes a feeder terminal (5) disposed on the rear window panel (2) near an edge thereof, and a plurality of antenna wires (4). A first section (4a) of the antenna extends from the feeder terminal along an edge of the rear window panel, a second section (4b) is folded from an end of the first section (4a) towards a vertical central line (6) of the rear window panel, and a third section (4c) extends as a main antenna section from an end of the second section (4b). The second section (4b) includes a horizontally folded portion which comprises a plurality of thin wires lying parallel to each other. The parallel thin wires are equivalent to a thicker wire for achieving increased gain in a wider frequency band and also reduced impedance. <IMAGE>

Description

ANTENNA FOR WINDOWS OF AUTOMOBILES The present invention relates to an antenna for use on a window, for example the rear window, of an automobile for receiving radio or television broadcast signals.

It is customary for automobiles to have an antenna on a rear window glass panel for receiving radio or television broadcast signals in combination with a plurality of defrosting electric wires. The rear window glass antenna has antenna wires including a folded portion to achieve phase adjustment with respect to certain frequency bands for an increased reception gain.

Any portions of the antenna wires which are exposed out of a masked area on the rear window glass would pose a problem on the appearance of the rear window glass.

Therefore, the width of the folded portion of the antenna wires which is exposed out of the masked region should not be too large, and is usually held to 1 mm.

The antenna wires in the masked area where they are concealed by a flange of the automobile body have a width ranging from 3 to 5 mm.

Since the folded portion of the antenna wires has a high impedance, its sensitivity is very low because of the small width of about 1 mm.

One known rear window glass antenna is disclosed in Japanese patent publication No. 61-5282 published February 17, 1986.

According to the present invention, there is provided an antenna on a window of an automobile, comprising: a feeder terminal disposed on the window near an edge thereof; and a plurality of antenna wires disposed on the window and including a first section extending from said feeder terminal along an edge of the window, a second section folded from an end of said first section toward a vertical central line of the window, and a third section extending as a main antenna section from an end of said second section, said second section comprising a plurality of thin wires lying parallel to each other.

The second section may include a horizontally folded portion, the horizontally folded portion comprising the plurality of thin wires lying parallel to each other.

The number of thin wires of the second section may range from 2 to 4.

Each of the thin wires may have a width ranging from 0.4 to 1.2 mm, and the distance between the central axes of the thin wires may range from 1 to 3 mm.

Embodiments of the present invention may provide an antenna for the rear glass window of automobiles which has a relatively high sensitivity that is achieved without increasing the width of antenna wires exposed out of a masked area on a rear window glass panel.

Embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings in which: FIG. 1 is a plan view of a wire pattern of a rear window glass antenna, on a rear window glass panel of an automobile, embodying the present invention; FIG. 2 is an enlarged fragmentary plan view of a folded region of a rear window glass antenna, which is composed of two thin antenna wires; FIG. 3 is an enlarged fragmentary plan view of a folded region of a rear window glass antenna, which is composed of three thin antenna wires; FIG. 4 is a graph showing sensitivity vs. frequency characteristics of different rear window glass antennae; FIG. 5 is a table of some numerical values of the sensitivity vs. frequency characteristics shown in FIG.

4; and FIGS. 6(a) and 6(b) are enlarged fragmentary plan views of modified rear window glass antennae.

As shown in FIG. 1, a rear window glass antenna 1 embodying the present invention comprises a group 3 of heating electric wires disposed on and extending horizontally on an automobile rear window glass panel 2, a group 4 of antenna wires disposed on the rear window glass panel 2 above the group 3 of heating electric wires, and a feeder terminal 5 connected to the antenna wires at a vertical (i.e. side) edge of the rear window glass panel 2 for transmitting a received radio or television broadcast signal to a receiver (not shown).

The group 3 of heating electric wires is connected to a battery (not shown) through a pair of buses 3a, 3b on their opposite ends. When energized, the heating electric wires defrost the rear window glass panel 2.

The group 4 of antenna wires comprises three antenna sections including an L-shaped section 4a, an L-shaped section 4b, and a T-shaped section 4c which is a main antenna section.

The L-shaped section 4a comprises a vertical portion 4d extending upwardly from the feeder terminal 5 and a horizontal portion 4e bent from an upper end of the vertical portion 4d along an upper horizontal edge of the rear window glass panel 2 beyond a vertical central line 6 thereof.

The L-shaped section 4b comprises a vertical portion 4f extending downwardly from a distal end of the horizontal portion 4e of the L-shaped section 4a, and a horizontal portion 4g bent from a lower end of the vertical portion 4f up to the vertical central line 6.

The T-shaped section 4c, which is electromagnetically coupled to the group 3 of heating electric wires at high frequencies, comprises a vertical portion 4h extending downwardly from a distal end of the horizontal folded portion 4g of the L-shaped section 4b along the vertical central line 6, and a horizontal portion 4i extending in opposite horizontal directions from a lower end of the vertical portion 4h and lying above the group 3 of heating electric wires.

The group 4 of antenna wires has certain preferable dimensions that are given in the table below:

I 1 I I I l a I b I c / d I e I I I I (mm) 200 1 10 1 40 1 30 1 900 In the above table, the dimension a is the length of a segment of the horizontal portion 4a which extends beyond the vertical central line 6 to its distal end, the dimension b is the length of the vertical portion 4f, the dimension c is the length of the vertical portion 4h, the dimension d is the distance between the horizontal portion 4i and the uppermost heating electric wire of the group 3, and the dimension e is the length of the horizontal portion 4i.

The L-shaped section 4a of the antenna wires has a width of 3mm, and the other sections of the antenna wires except the horizontal folded portion 4g have a width of 1 mm.

In embodiments of the present invention, the horizontal folded portion 4g comprises a plurality of thin wires, preferably in the range of two to three thin wires.

FIG. 2 shows a horizontal folded portion 4g which is composed of two thin wires lying parallel to each other.

FIG. 3 shows a horizontal folded portion 4g which is composed of three thin wires lying parallel to each other.

In FIGS. 2 and 3, the horizontal portion 4e is concealed by a masked area 7 on the rear window glass panel 2.

The thin wires lying parallel to each other of the horizontal folded portion 4g are equivalent to a thicker wire for achieving an increased gain in a wider frequency band and also achieving a reduced impedance.

Each of the thin wires of the horizontal folded portion 4g has a width ranging from 0.4 to 1.2 mm, and the distance between the central axes of adjacent thin wires ranges from 1 to 3 mm. The width of the entire horizontal folded portion 4g, including the widths of the thin wires and the distance or distances therebetween, ranges from 3 to 10mum.

The group 3 of heating electric wires, the buses 3a,3b, the group 4 of antenna wires, and the feeder terminal 5 may be formed by printing an electrically conductive paste composed of fine particles of silver or glass of low melting point which are mixed with an organic solvent on the rear window glass panel 2 by screen process printing, or by sandwiching metallic wires between two glass layers.

When electromagnetic waves are received by the rear window glass antenna 1, the signal produced by the rear window glass antenna 1 is transmitted from the feeder terminal 5 to the receiver through a coaxial cable (not shown).

FIG. 4 shows sensitivity vs. frequency characteristics of different rear window glass antennas used to receive FM broadcasts in an FM broadcast frequency range from 76 MHz to 90 MHz. The horizontal axis of the graph illustrated in FIG. 4 represents the frequency, and the vertical axis thereof represents the sensitivity. Some numerical values of the sensitivity vs. frequency characteristics are shown in FIG. 5.

The solid-line curve a shown in FIG. 4 indicates sensitivities, plotted against the frequency, of a rear window glass antenna whose horizontal folded portion 4g comprises a single wire. The dot-and-dash-line curve b shown in FIG. 4 indicates sensitivities, plotted against the frequency, of a rear window glass antenna whose horizontal folded portion 4g comprises two thin parallel wires. The dotted-line curve c shown in FIG. 4 indicates sensitivities, plotted against the frequency, of a rear window glass antenna whose horizontal folded portion 4g comprises three thin parallel wires.

The average sensitivities of these rear window glass antennas in terms of sensitivity differences (dipole ratios) with the sensitivity of a reference dipole antenna which is 0 dB are - 13.9 dB, - 12.8 dB, and - 12.2 dB, respectively. It can thus be seen that the sensitivity of the rear window glass antenna can be increased at all frequencies by increasing the number of thin parallel wires. Therefore, the rear window glass antenna 1 embodying the present invention has very good sensitivity vs. frequency characteristics.

Since the antenna portions which are exposed out of the masked area 7 are relatively thin, they are less visible than thicker wires and do not make the rear window glass panel 2 unsightly.

The rear window glass antenna 1 embodying the present invention may be used singly on the rear window glass panel 2 for receiving radio or television broadcast waves. For better results, however, the rear window glass antenna 1 may be used in combination with glass antennas or the like on side window glass panels of the automobile for diversity reception.

FIG. 6(a) shows a modified rear window glass antenna. In FIG. 6(a), the masked area 7 on the rear window glass panel 2 is relatively large to reduce any problem on the appearance of the rear window glass panel 2, and the antenna portion concealed by the masked area 7 has a relatively large width in its entirety.

FIG. 6(b) illustrates another modified rear window glass antenna. In FIG. 6(b), both the horizontal folded portion 4g and also the vertical portion 4h are composed of a plurality of thin wires.

Although there have been described what are at present considered to be the preferred embodiments of the invention, it will be understood that the invention may be embodied in other specific forms without departing from the essential characteristics thereof.

The present embodiments are therefore to be considered in all respects as illustrative, and not restrictive.

The scope of the invention is indicated by the appended claims rather than by the foregoing description.

Claims (7)

1. An antenna on a window of an automobile, comprising: a feeder terminal disposed on the window near an edge thereof; and a plurality of antenna wires disposed on the window and including a first section extending from said feeder terminal along an edge of the window, a second section folded from an end of said first section toward a vertical central line of the window, and a third section extending as a main antenna section from an end of said second section, said second section comprising a plurality of thin wires lying parallel to each other.

2. An antenna as claimed in claim 1, wherein said second section includes a horizontally folded portion, said horizontally folded portion comprising said plurality of thin wires lying parallel to each other.

3. An antenna as claimed in claim 1 or 2, wherein the number of thin wires of said second section ranges from 2 to 4.

4. An antenna according to claim 1, 2 or 3, wherein each of said thin wires has a width ranging from 0.4 to 1.2 mm, and the distance between the central axes of said thin wires ranges from 1 to 3mm.

5. An antenna as claimed in any preceding claim, wherein said antenna is arranged on the rear window of an automobile.

6. An antenna as claimed in claim 5, wherein a plurality of heating electric wires are disposed substantially horizontally on said rear window.

7. An antenna substantially as hereinbefore described with reference to Figures 1 to 5, 6(a) or 6(b).