GB1559871A

GB1559871A - Multiband antenna for window panes

Info

Publication number: GB1559871A
Application number: GB3203476A
Authority: GB
Original assignee: Societa Italiana Vetro SIV SpA
Current assignee: Societa Italiana Vetro SIV SpA
Priority date: 1976-07-31
Filing date: 1976-07-31
Publication date: 1980-01-30

Description

(54) MULTIBAND ANTENNA FOR WINDOW PANES (71) We, SOCIETA ITALIANA VETRO SIV S.p.A., an Italian Joint Stock Company of Vasto (Chieti), Italy, do hereby declare the invention for which we pray that a patent may be granted to us, and the method' by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a multiband receiving antenna supported on a window pane, particularly on the windshield of a motor vehicle, for a radio receiving set.

The term "windowpane" is intended to mean a pane of glass or of plastics material.

The antenna may consist of conductors deposited by the silk screen process on the pane. In the case of an antenna supported on the windshield of a motor vehicle it is preferred where the windshield is formed from tempered glass that the antenna is deposited on that face of the pane which, when fitted in the vehicle, is the internal one, and where the windshield is formed from two glass panes bonded together that the antenna is deposited on one of the faces of the pane which is in contact with another face. Instead of deposit- ing the conductors by the silk screen process, a conducting metal wire may be used.

Obviously, an antenna may be supported on any window of a motor vehicle, although the windshield is the most suitable place.

The present invention further relates to an antenna for receiving radio signals lying in various wave bands, for example, in the long wave band, the medium wave band, the short wave band, the metric or VHF wave band, the decimetric wave band, and the UHF wave band, and generally in all the wave bands used for sound and television transmission, including the frequencies reserved for radio amateurs.

In the case of a motor vehicle, an antenna supported on a windowpane, particularly on the windshield, is preferred to a conventional freely supported antenna because such antennas are subjected to various drawbacks such as:a) considerable vibration during driving which causes signal fluctuations, particularly when receiving distant stations with the receiver operating in threshold conditions; b) marked instability in their characteristics, such as increase in their resistance and consequent increase in their losses and changes in the antenna capacitance due to aging, and to water penetration into the bottom cylindrical element, which causes corrosion and oxidation of the tubu lar elements in the resulting damp atmosphere; c) in the case of monopole antennas, the fact that they project beyond the motor vehicle contours, which leads often to their break ing, for instance, when entering a garage or underpass, or damaging persons or goods if thev are badly installed; d) furthermore a monopole antenna is also subject to being willfully broken by vandals.

For all these reasons, windshield antennas have been developed.

It is well known that the majority of radio; receiving sets for motor vehicles are provided with a single antenna socket, in contrast to domestic receivers which have one input for the medium wave band and another input for the metric wave band. Therefore a problem which must be faced with antennas provided on motor vehicle windshields is that of obtaining good reception, for example, in the medium wave band as well as in the metric wave band with a single antenna socket provided in the radio-receiving set.

In order to obtain good reception, the ideal would be that of having an antenna of a length equal to a well defined fraction of the wave length to be received, such as A/2 or X/4 according to whether the antenna is of a symmetrical or assvmmetrical type. The standard sizes of motor vehicle windshields render, at least for the medium wave band, antennas of such length impossible.

In one arrangement, the present invention provides a multi-band receiving antenna supported on a window pane for a radio receiver having a single input terminal, the antenna comprising an antenna terminal located at a position adjacent to the rim of the window pane and a pair of conductors electrically connected to the antenna terminal, each con ductor comprising a first portion extending from the terminal to a position adjacent to an opposite part of the rim, the two first portions being parallel to each other, a second portion extending from the end of the first portion in a direction away from the other conductor and running alongside part of the rim, and a third portion which doubles back on, and runs parallel to, at least part of the second portion.

In another arrangement, the present invention provides a multi-band receiving antenna supported on a window pane for a radio receiver having a single input terminal, the antenna comprising an antenna terminal located at a position adjacent to the rim of the window pane and a conductor electrically connected to the antenna terminal, the conductor comprising a first portion extending away from the terminal to a position adjacent to an opposite part of the rim, a pair of second portions, the second portions connected to and extending away from the end of the first portion in opposite directions and running alongside respective parts of the rim, and a pair of third portions, each third portion doubling back on, and running parallel to, at least part of a respective one of the second portions.

The present invention will now be described in more detail, by way of example, with reference to the accompanying drawings in which: Figure 1 represents a conventional two conductor T-type antenna supported on a motor vehicle windshield; and Figures 2a and b and 3a and b show examples of the present invention.

All the embodiments of the invention shown are supported on motor vehicle windshields.

Each Figure marked (a) shows an arrangement having two antenna conductors, and each Figure marked (b) shows an arrangement having a single antenna conductor. The same reference numerals are used for like elements in all Figures.

The known antenna shown in Figure la comprises an antenna terminal located at a position adjacent to the middle of the lower rim of the windshield and a pair of conductors 2, 3 electrically connected to the antenna terminal. The antenna terminal 1 is located a few centimetres from the lower rim of the windshield. Each of the conductors 2, 3 comprises a first portion for receiving radio signals in the metric wave band which extends vertically upwards from the terminal 1 to a position adjacent the middle of the upper rim of the windshield, and a second portion which extends away from the other conductor and runs alongside the upper part of the rim at a distance of 7 cm from the rim.

The known antenna shown in Figure 1b comprises an antenna terminal 1' located adjacent to the middle of the lower rim of the windshield and a single antenna conductor 2'. The antenna terminal 1' is located a few centimetres above the lower rim of the windshield. The conductor 2' comprises a first portion for receiving radio signals lying in the metric wave band which extends from the terminal 1' vertically upwards to a position adjacent the middle of the upper rim of the windshield and then branches in opposite directions to form two second portions which mn alongside the upper rim of the windshield and spaced a distance of 7m therefrom.

In the example shown in Figure 2a, each second portion is extended to a position adjacent to the terminal 1 and each conductor further includes a third portion which doubles back on, and runs parallel to the second portion for 2 of its length.

In Figure 2b, each second portion is extended to a position adjacent to the terminal 1. and the conductor 2' further includes a third portion which doubles back on the second portion, and runs parallel to it, for i of its length.

In Figure 3a each second portion, is extended to a position adjacent to the terminal 1, and each conductor further includes a third portion 7 which doubles back on the second portion. and runs parallel to it, for almost its entire length.

In Figure 3b, each second portion of the conductor 2' is extended to a position adjacent to the terminal 1', and each second portion has a third portion 7' which doubles back on it. and runs parallel to it, for almost its entire length.

It has been found by extending the second nortions in this manner and by providing the third portions reception of signals in the medium wave band is improved.

The antennas shown in Figure 2a, 2b, 3a, and 3b provide good reception in the medium wave band as each of these antennas has a capacitance of 70 to 100 picofarads and a loss resistance of several hundred kilohoms, and a complex antenna impedance in the metric wave band which is prevalently resistive of approximately 150 ohms. which a phase angle lying in the range +300 to 300.

It has been found that for the antenna examples shown in Figures 2 and 3 the optimum spacing for the second and third portions from the windshield rim is 7 cm and, when the windshield dimensions permitted without interfering with visibilitv, it has been found that the spacing may be advantageously increased to approximately 9 or 10 cm.

In Figures 2 and 3, it has been found that the spacing between the second and third portions should lie in the range 0.2 to 1.2 cm, or in the range 0.3 to 1.2 cm, or preferably be 0.4 cm.

The antenna conductors may be made from wire, which normally has a diameter of 0.1 to 0.2 mm, or by the silk screen process.

Also, when using wire, the antenna is sandwiched between the two panes of glass which form the windshield, whilst when an antenna is made from the silk screen process, it may be supported either on the interface of the two panes of glass or on the internal face of the windshield. As the speed of propagation of electromagnetic waves varies according to the structure of the antenna and also its position, the length of the antenna should be varied accordingly.

The antennas shown in Figures 2 and 3 may be supported on a windshield somewhat smaller than 60 by 130 cm whilst, at the same time, obtaining an antenna capacitance in the range 60 to 70 picofarads, an antenna loss resistance in excess of 400 kilohms, and a complex antenna impedance of approximately 150 ohms, with a phase angle lying in the range +30 to 300.

In the following table, there is shown the increase in voltage as measured at a receiver terminal for an antenna having a configuration as shown in Figure 3 compared with the voltage obtained with the conventional antenna shown in Figure 1. These measurements were made on antennas supported on a windshield having a size of 60 by 130 cm for the reception of radio signals in the medium wave band (MW) and in the metric wave band (FM).

This table clearly shows the improvement obtained by using the antennas of the present invention over the known antenna of Figure 1.

ANTENNA OF FIG. 1 7 FIG. 3 MW 1 1.8 FM 1 1.35 WHAT WE CLAIM IS: 1. A multi-band receiving antenna supported on a windowpane for a radio receiver having a single input terminal, the antenna comprising an antenna terminal located at a position adjacent to the rim of the window pane and a pair of conductors electrically connected to the antenna terminal, each conductor comprising a first portion extending from the terminal to a position adjacent to an opposite part of the rim, the two first portions being parallel to each other, a second portion extending from the end of the first portion in a direction away from the other conductor and running alongside part of the rim, and a third portion which doubles back on, and runs parallel to, at least part of the second portion 2. An antenna according to claim 1 in which each second portion runs alongside the rim to a position adjacent the =antenna terminal.

3. An antenna according to claim 2 in which each third portion runs parallel to the second portion for substantially the whole length of the second portion.

4. An antenna according to any one of the preceding claims in which in each conductor the second and third portions are spaced from each other by a distance lying in the range 0.2 to 1.2 cm.

5. An antenna according to claim 4 in which in each conductor the second and third portions are space from each other by a distance lying in the range 0.3 to 1.2 cm.

6. An antenna according to claim 5 in which in each conductor the second and third portions are spaced from each other by 0.4 cm.

7. An antenna according to any one of the preceding claims in which in each conductor the second and third portions are spaced from the rim by a distance lying in the range 7 to 10 cm.

8. A multi-band receiving antenna supported on a windowpane for a receiver having a single input terminal, the antenna comprising an antenna terminal located at a position adjacent to the rim of the window pane and a conductor electrically connected to the antenna terminal, the conductor comprising d first portion extending away from the terminal to a position adjacent to an opposite part of the rim, a pair of second portions, the second portions connected to and extending away from the end of the first portions in opposite directions and running alongside respective parts of the rim, and a pair of third portions, each third portion doubling back on, and running parallel to, at least part of a respective one of the second portions.

9. An antenna according to claim 8 in which each second portion runs alongside the rim to a position adjacent the antenna terminal.

10. An antenna according to claim 9 in which each third portion runs parallel to the respective second portion for substantially the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. wire, which normally has a diameter of 0.1 to 0.2 mm, or by the silk screen process. Also, when using wire, the antenna is sandwiched between the two panes of glass which form the windshield, whilst when an antenna is made from the silk screen process, it may be supported either on the interface of the two panes of glass or on the internal face of the windshield. As the speed of propagation of electromagnetic waves varies according to the structure of the antenna and also its position, the length of the antenna should be varied accordingly. The antennas shown in Figures 2 and 3 may be supported on a windshield somewhat smaller than 60 by 130 cm whilst, at the same time, obtaining an antenna capacitance in the range 60 to 70 picofarads, an antenna loss resistance in excess of 400 kilohms, and a complex antenna impedance of approximately 150 ohms, with a phase angle lying in the range +30 to 300. In the following table, there is shown the increase in voltage as measured at a receiver terminal for an antenna having a configuration as shown in Figure 3 compared with the voltage obtained with the conventional antenna shown in Figure 1. These measurements were made on antennas supported on a windshield having a size of 60 by 130 cm for the reception of radio signals in the medium wave band (MW) and in the metric wave band (FM). This table clearly shows the improvement obtained by using the antennas of the present invention over the known antenna of Figure 1. ANTENNA OF FIG. 1 7 FIG. 3 MW 1 1.8 FM 1 1.35 WHAT WE CLAIM IS:

1. A multi-band receiving antenna supported on a windowpane for a radio receiver having a single input terminal, the antenna comprising an antenna terminal located at a position adjacent to the rim of the window pane and a pair of conductors electrically connected to the antenna terminal, each conductor comprising a first portion extending from the terminal to a position adjacent to an opposite part of the rim, the two first portions being parallel to each other, a second portion extending from the end of the first portion in a direction away from the other conductor and running alongside part of the rim, and a third portion which doubles back on, and runs parallel to, at least part of the second portion

2. An antenna according to claim 1 in which each second portion runs alongside the rim to a position adjacent the =antenna terminal.

whole length of the second portion.

11. An antenna according to any one of claims 8 to 10 in which each second portion is spaced from its respective third portion by a distance lying in the range 0.2 to 1.2 cm.

12. An antenna according to claim 11 irL which each second portion is spaced from its respective third portion by a distance lying in the range 0.3 to 1.2 cm.

13. An antenna according to claim 12 in which each second portion is spaced from its respective third portion by 0.4 cm.

14. An antenna according to any one of claims 8 to 13 in which the second and third portions are spaced from the rim by a distance lying in the range 7 to 10 cm.

15. A multi-band receiving antenna supported on a window pane substantially as hereinbefore described with reference to and as shown in Figure 2a, Figure 2b, Figure 3a, or Figure 3b of the accompanying drawings.