GB2321342A

GB2321342A - Cellular telephone antenna

Info

Publication number: GB2321342A
Application number: GB9700859A
Authority: GB
Inventors: Andrew Jesman; Christopher Jesman
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-01-16
Filing date: 1997-01-16
Publication date: 1998-07-22
Also published as: GB9700859D0

Abstract

An antenna for use at selected frequencies of cellular telephony and Global Positioning System (GPS) systems, comprises a base terminal intended to be secured to a motor vehicle, from which terminal extends a first radiator element 2 connected via a phasing coil 3 to a second vertical radiator element 5. The geometry of the radiators 2,5 is such that they respond to the selected frequencies.

Description

Cellular telephone antenna The present invention relates to a cellular telephone antenna, particularly, although not exclusively, for use with a vehicle body mount.

It is well known that cellular telephony may operate on a range of different frequencies and standards. In Europe, for example, there are a number of different standards for cellular communication. Analogue networks (TACS or ETACS) operate at a frequency of around 900MHz within Europe, whilst digital networks such as the Global System for Mobile communications (GSM or D-Net as it is known in Germany) operates at a similar frequency of around 900MHz. An alternative digital network is the Personal Communications Network (PCN or E-Net as it is known in Germany) which operates at a much higher frequency of around 1800MHZ. Of the latter two systems it has been found that GSM is better able to cover larger geographical areas whilst PCN should provide better service in urban areas.

Presently available digital cellular telephones are committed to utilising one or other of the two systems.

However, new equipment is emerging which can operate under either system although present antennae and particularly those used with vehicles are incapable of operating efficiently with such equipment.

Thus, although dual frequency or trap antennae are known they suffer from a number of disadvantages, in particular the need for relatively complicated frequency separation circuity. Consequently, is an object of the present invention to provide an antenna which operates equally effectively with either system. It is a further object of the present invention to provide an antenna which is compatible with signals received from Global Positioning System (GPS) satellites such as are becoming more common for vehicle navigation systems.

According to the invention there is provided an antenna for use at selected frequencies of cellular and GPS systems, the antenna having a base terminal incorporating a first radiator connected via a phasing coil to a second vertical radiator, the arrangement being such that both radiators respond to the selected frequencies.

Preferably, the antenna is attached to a mount suitable for fitting to a vehicle panel, although it is envisaged that the antenna could be used with a glass mount base in which case separately tuned coupling circuitry would be required to couple the antenna signals across the glass to the interior of the vehicle. Advantageously, the first radiator may be formed as an extension of the base terminal which may additionally provide a crimping point for connection to the phasing coil.

Clearly, the dimensions of the antenna are selected to provide resonance at the frequencies of interest, namely those of the GSM, PCN and GPS systems, respectively 870960MHz, 1700-2000Mhz and 1570-1580MHz. Once more, by the choice of suitable geometry, it will recognised by one skilled in the art that the E-plane (Electric plane) may be biased towards the horizon and thereby increase the suitability of the antenna to cellular systems although reducing the effectiveness of the antenna at receiving GPS signals. Nevertheless, the antenna remains capable of detecting such GPS signals. An antenna having an omnidirectional H-plane (magnetic plane) is, of course, preferred for efficient operation with cellular systems.

In order to aid in understanding the invention a specific embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a sectional side view of the separate components of an antenna according to the invention; Figure 2 is a cross-sectional side view of the antenna of Figure 1 at an intermediate stage of assembly; Figure 3 is a similar view to that of Figure 2 at later stage of assembly; Figure 4 is a similar view a still further stage of assembly; and Figure 5 is side view of the assembled antenna of Figure 1 mounted on a vehicle.

Referring to the Figures, the antenna 1 comprises a combined bottom crimp terminal and first radiating element 2, a metallic helically wound spring or phasing coil 3, a top crimp terminal 4, and a stainless steel rod or second radiating element 5. The bottom crimp terminal 2 is formed with an end connector suitably threaded or otherwise formed for connection to a base 7 mounted on the roof 8 or other body panel of a vehicle. Antenna signals are fed to terminals (not shown) within the base 7 which terminals connect to a coaxial or other suitable antenna lead 6.

The antenna is assembled in a series of stages as set out in Figures 2 to 4 of the drawings. Firstly, one free end 9 of the coil 3 is crimped to a crimp point 10 in the bottom crimp terminal and first radiating element 2. The other free end 11 of the coil 3 is then crimped within the top crimp terminal 4 leaving space within the terminal 4 for the second radiating element 5 to be similarly inserted and crimped in place. To complete the basic assembly, a pressed butterfly 12 is secured to the remaining free end 13 of the element 5 to facilitate plastics material encapsulation.

Turning to Figures 3 and 4, these show a two step moulding process, in which firstly (Figure 3) a black engineering plastics material moulding 14 is formed around the coil 3. A second later moulding stage follows (Figure 4), in which a black plastics material moulding 15 is formed around the bottom crimp terminal 2 and the previously encapsulated coil 3,14. Such a two stage process enhances the surface finish of the completed moulding which otherwise might reveal the contours of the encapsulated coil. A separate end plastics material end tip 16 is moulded around the butterfly 12 at the free end of the element 5.

An assembled antenna is shown in Figure 5 attached to the base 7 of the panel mount type on the vehicle containing the cellular and/or GPS equipment.

It will be appreciated by one skilled in the art that the above antenna could, instead of being made up of several separate elements, be formed as a unitary item which would advantageously increase the performance and simplify assembly of the antenna. However, the skilled person would also recognise the difficulty in manufacturing such an antenna and in particular the difficulty of ensuring that the first and second radiating elements remain coaxial with the phase coil.

Claims

Claims:

1. A mobile telephony antenna for use at selected frequencies of cellular and Global Positioning System (GPS) systems, the antenna having a base terminal incorporating a first radiator connected via a phasing coil to a second vertical radiator, the arrangement being such that both radiators respond to the selected frequencies.

2. An antenna as claimed in Claim 1, wherein the base terminal is attached to a mount suitable for fitting to a vehicle panel.

3. An antenna as claimed in Claim 1, wherein the base terminal is attached to a glass mount which includes tuned coupling circuitry to couple the antenna signals across the glass to a coupling box on the interior of the vehicle.

4. An antenna as claimed in any preceding Claim, wherein the first radiator is formed as an extension of the base terminal.

5. An antenna as claimed in Claim 4, wherein the first radiator provides a crimping point for connection to the phasing coil.

6. An antenna as claimed in any one of Claims 1, 2 or 3, wherein the first and second radiating elements are formed as a unitary item in conjunction with the phase coil.

7. An antenna as claimed in any preceding Claim, wherein the phasing coil comprises a metallic helically wound spring.

8. A mobile telephony antenna for use at selected frequencies of cellular and Global Positioning System (GPS) systems substantially as described herein with reference to the accompanying drawings.