EP0464127B1

EP0464127B1 - Mobile communications antenna

Info

Publication number: EP0464127B1
Application number: EP90905715A
Authority: EP
Inventors: Ulf Saldell
Original assignee: Allgon AB
Current assignee: Allgon AB
Priority date: 1989-03-17
Filing date: 1990-03-16
Publication date: 1995-08-23
Anticipated expiration: 2010-03-16
Also published as: SE8900965D0; EP0464127A1; SE8900965L; SE463285B; DE69021875T2; DE69021875D1; WO1990011627A1

Abstract

Radio antennae are known for vehicles for mounting against a glass pane and include an antenna rod fastened to an electrically conductive base which is mounted against the outside of the glass pane, a connection device (8) coacting with the base and mounted on the inside of the glass pane directly opposite the base. The connection device (8) is connected to an antenna cable taking the form of a coaxial cable from the vehicle radio, and the connection device comprises a box (8) of at least partially electrically conductive material with an open side facing towards the base, the box being mounted against the glass pane with the aid of a non-conductive disc (9) covering the open side. For improving signal transfer from the antenna to the antenna cable the conductor of the latter extends insulated through the connections means box (8) and has a connection (11, 13) to an opposing plane (12) at the inside of the glass pane, this opposing plane lying in the covering disc (9) directly opposite the base of the antenna.

Description

A radio antenna for vehicles for mounting against a glass pane on a vehicle and including an antenna rod fastened to an electrically conductive base, which is mounted against the outside of the glass pane, a connection device coacting with the base and mounted on the inside of the glass pane directly opposite the base, an antenna cable in the form of a coaxial cable connecting the vehicle radio with the connection device, the connection device comprising a housing of at least partially electrically conductive material and which has an open side facing towards the base, the housing being mounted against the glass pane with the aid of a plate of non-conductive material covering the open side, whereby a connection extends insulated through the housing between the end of the antenna cable conductor and an opposing plane on the inside of the glass pane, said opposing plane lying in the covering plate directly opposite the base of the antenna.
In sending and receiving radio signals via an antenna on a vehicle it is known to-day to allow this to take place without making holes in the vehicle body, despite of the antenna being mounted on the outside of the vehicle. The most usual method in such a case is to mount the antenna on the outside of a window pane and arrange a connection device on the inside thereof, the device being connected via a cable to a communication radio or any other kind of radio. An insulated connection is formed between the cable and the connection device. This is described i.a. in EP 0 137 391 and EP 0 279 117.
The present invention has the object of improving known constructions so that the antenna can be mounted on any kind of dielectric plates, i.e. not solely glass, and that there is the possibility of removing the mounting if so desired. It is also endeavoured to connect the cable from the communication radio to the connection device so that a capacitance can be formed with the assistance of the connection.
The antenna rod together with its mounting determines the impedance of the system. Then radio signals or waves are transferred from the antenna rod via its base to a connection device by the base and a part in the connection device forming a capacitor. Since the connection device is insulated in relation to the vehicle body, the vehicle does not participate in forming the antenna earth, and the antenna is thus usable as a standard component independent of the vehicle body configuration and size.
What is characterizing for the invention is disclosed in the following claims, and two embodiments will be described below with reference to the accompanying drawing figures, where
Fig. 1 is a side view partially in section of a mounting for the antenna rod.
Fig. 2 is plane view of the mounting.
Fig. 3 is a cross section of the connection device for mounting on the inside of the glass pane.
Fig. 4 is a section through the connection device along the line IV-IV in Fig. 3.
Fig. 5 schematically illustrates an alternative embodiment of the connection device.
The mounting for the antenna rod comprises a circular metallic base 1. In its central region the base has two upstanding lugs 2 and 3, and between these the lower end of the antenna is mounted with the aid of a pipeting pin 4 which allows the antenna to be swung round the pin from an upright positon illustrated in Fig. 1 to a position turned 90° and illustrated by chain dotted lined. The antenna is preferably mounted on a small rod 5 which is pivotably mounted on the lugs 2 and 3. The outer end of the rod 5 is provided with a thread 6 or engaging an internal thread on the antenna, enabling the lug to be attached to the rod 5 and removed when so desired. The base 1 is made from electricly conductive material and is mounted against the outside of the windshield with aid of such as double-sided tape 7. Impedance is determined by the antenna length and configuration as well as by the base 1.
The connection device, which together with the base on the outside of the windshield is to form the connection for passing radio waves from the antenna to the communication radio comprises a box 8 of at least partially electricly conductive material. The box has an open side facing towards the inside of the windshield and directly opposite the base 1. In Fig. 3 this open side is covered by a disc 9 which in the present case is a circuit card which can contain control means for capacitance and/or inductance. The outside of the disc 9 is covered by a double-sided tape 10. Through the centre of the disc there extends a pin 11 which has an enlarged end 12 enabling the formation of a small disc-like surface. This surface constitutes the opposing plane forming together with the base the capacitor connection in the connection device. The pin 11 is connected to a wire loop 13 which is insulated against the box 8 and extends through the side wall of the box and can be connected to the conductor in a cable which is connected to the communication radio in the vehicle. The wire loop 13 has, in a plane parallel to the disc 9, a specific form which is to be seen in Fig. 4. This form can be said to correspond to that of a hook.
The loop 13 is connected to a capacitor plate 14, the configuration of which is approximately rectangular and which is also apparent from Fig. 4. The capacitor plate has a given spacing from the bottom of the box 8 and this spacing can be varied with the aid of an insulated screw 15. Between the capacitor plate 14 and the bottom 20 of the box 8 is an insulation disc 16, which has an upwardly bent side 17 extending a distance upwards into the box. The side 17 covers a sleeve 18 projecting inwardly in the box 8. The wire loop 13 extends into the sleeve 18 and is insulated against it. The sleeve 18 receives the cable going to the communication radio, and the chief of this cable passes into the sleeve 18 and its conductor connects to the part 19 of the wire loop 13 extending inwards into the sleeve 18. The conductor of the cable from the communication radio thus connects via the part 19 and via loop 13 to the pin which is connected via a capacitor to the antenna. A further capacitor circuit is formed by the capacitor plate 14 and the bottom 20 of the of the box 8, and this capacitor circuit is connected to the cable to the communication radio via the loop 13 and part 19. It will be seen from Figs. 3 and 4 that the wire loop 13 and its part 19 are insulated from the sleeve 18 with the aid of an insulator 21 placed in the sleeve.
A variant is illustrated in Fig. 5 and differs from what is shown in Fig. 3 in that the capacitor plate 14 is lacking and in that the loop 13 has another configuration. Instead of the loop 13 there is a connection between the part 19 and the pin 11 in the form of a loop circuit 22. This circuit has a certain extension in the plane parallel to the bottom plane 20 of the box 8 and is disposed so closed to the bottom 20 that it forms one side of a capacitor where the other side is the bottom 20, and there is an intermediate insulation disc 16 between them in the same way as in the previous embodiment.
In the description so far the box 8 has been described as being made of metal. However, this is not necessary, and what is important is that there is at least some metal surface in the box, so that the capacitance between the wire loop 13 and the metal part of the box can be formed. In addition, so-called stray capacitances and at least on stray capacitance can be said to be formed between the enlarged part 12 of the pin 11 and the metal part in the box 8.
It will be noted that the description of embodiments really provides two conceivable embodiments of a principle were the conductor from the communication radio is insulated the whole way right up to the capacitor surface constituting one side of the capacitor which transfers the signals to the antenna. The sole connection with conductive material which otherwise is present is via capacitor where one side consists of the conductive metal part of the box and the other side the conductor itself, or a capacitor plate connected to the conductor. Conductances and capacitances are otherwise formed in dependence of what capacitances are required for adapting the antenna to a given frequency. For guidance in understanding the description it may be said that the drawing figures are approximately to a scale of 2:1, and that the antenna system is intended for frequencies used in ordinary communication radio systems.

Claims

A radio antenna for vehicles for mounting against a glass pane on a vehicle and including an antenna rod fastened to an electrically conductive base (1-4), which is mounted against the outside of the glass pane, a connection device (8) coacting with the base and mounted on the inside of the glass pane directly opposite the base, an antenna cable in the form of a coaxial cable connecting the vehicle radio with the connection device, the connection device comprising a housing (8) of at least partially electrically conductive material and which has an open side facing towards the base, the housing being mounted against the glass pane with the aid of a plate (9)of non-conductive material covering the open side, whereby a connection (13; 22) extends insulated through the housing (8) between the end of the antenna cable conductor (19) and an opposing plane (12)on the inside of the glass pane, said opposing plane lying in the covering plate (9) directly opposite the base (1-4) of the antenna, characterized in that the connection (13; 22) extending in the housing has a configuration such that it forms a capacitance (13, 16; 22) with the electrically conductive part (20) of the housing (8).
Radio antenna as claimed in claim 1, characterized in that the connection inside the housing is further connected to one side of a capacitor plate (14), the other side of the capacitor being the conductive part (20) of the housing (8).
Radio antenna as claimed in claim 1, characterized in that the connection in its extension between the end of the antenna cable conductor and the opposing plane is in the form of a simple loop (22) which is extended at a given small distance from and without contact with a surface (22) of the housing (8), which surface includes the electrically conductive part.
Radio antenna as claimed in claim 1, characterized in that the opposing plane (12) comprises a surface-enlarged end of a pin (11).