GB2170958A - Antenna assembly - Google Patents

Abstract

An antenna assembly comprises a central element 6 extending from a support 4, a plurality of resilient elements 8 extending from the suport and arranged about the central element, and retaining means 10 for maintaining the distal ends of the resilient elements in juxtaposition to the central element, wherein the resilient elements 8 deploy, by bias stored therein, to operative positions about the central element when the distal ends thereof disengage the retaining means. <IMAGE>

Description

1 GB2170958A 1

SPECIFICATION

Antenna The present invention relates to antenna as- 70 semblies.

Single element vertical antenna structures are known. However, such structures have a relatively narrow electrical bandwidth which, when used with certain types of radio transmitter, necessitate adjustment of certain transmitter circuit elements to provide a de sired bandwidth for transmission.

The bandwidth of single element antenna structures can be increased significantly by providing a plurality of elements which are dis posed about the single element so as to form a conical array of elements about the single element with the single element extending from the apex of the conical array. However, antenna arrays of this design are inconvenient for many applications as the array is rather bulky to transport; each element being approx imately one meter in length. In order to reduce the size of the antenna for transportation the elements of the conical array may be arranged to pivot at the fixed end so that they may be folded against the central single element. For multi element arrays, however, this form of pivotal mounting of the elements increases substantially the manufacturing cost of the an tenna making it impractical for many applica tions.

It is an object of the present invention to provide a collapsable antenna assembly which can be manufactured relatively cheaply com pared to known designs of antenna assem blies.

According to the present invention there is provided an antenna assembly comprising a central element extending from a support, a plurality of resilient elements extending from the suport and arranged about the central ele ment, and retaining means for maintaining the distal ends of the resilient elements in juxtapo sition to the central element, and wherein the resilient elements deploy, by bias stored therein, to operative positions about the cen tral element when the distal ends thereof dis engage the retaining means.

Preferably the operative positions of the re silient elements about the central element form a conical array of resilient elements with the central element extending from the apex of the conical array.

Advantageously, the resilient elements in the conical array extend at an angle in the range of 15' to 25' with respect to the central ele ment.

Conveniently the resilient elements comprise 125 spring steel elements.

The central element may also comprise a resilient element.

Preferably the antenna assembly comprises six resilient elements.

The support may comprise a connection terminal for the antenna assembly.

The distal ends of the resilient elements may be linked to the central element by flexible restraining means to provide support for the distal ends of the resilient elements in the operative positions.

The present invention will now be described, by way of example, with reference to the accompanying drawing which illustrates an antenna assembly in accordance with the present invention.

Referring to the drawing, an antenna assembly 2 comprises a support such as a boss 4. The boss 4 may comprise a connection plug or socket (not shown) to enable connection of the antenna assembly 2 to a suitable transmitter or receiver. A central element 6 is mounted on an extends from the boss 4. The antenna assembly 2 also comprises a plurality of resilient elements 8, also mounted on a extending from the boss 4, and arranged about the central element 6. The resilient elements 8 may be fabricated from any suitable material, such as spring steel, and may be secured to the boss 4 by any suitable means, such as by soft solder. Retaining means, such as a ring 10, is provided so that the resilient element 8 may be maintained in a collapsed inoperative position with the distal ends 12 thereof in juxtaposition to the central element 6. The distal ends 12 of the resilient elements 8 may be linked to the central element 6 by flexible restraining means, such as lengths of cord or wire (not shown).

It can be seen from the accompanying drawing that the resilient elements 8 are arranged about the central element 6 such that, when the distal ends 12 are retained by the ring 10, spring bias is stored in the resilient elements 8. When the resilient elements 8 are retained in this manner, the antenna assembly 2 provides a compact unit which is convenient for transportation as the resilient elements 8 are held like a bundle of fingers surrounding the central element 6.

To deploy the antenna assembly 2 the ring 10 is moved to disengage from the resilient elements 8. The spring bias stored in the re- silient elements 8 causes them to assume their operative positions as a conical array of elements disposed about the central element 6. Typically, the resilient elements 8 have a length of approximately one meter and, the six resilient elements having operative positions extending at an angle of about 20' with respect to the central element 6, as shown by the far right resilient element 8 in the accompanying drawing, the antenna assembly 2 has a frequency range extending between 20 and 100 MHz.

Although the present invention has been described with respect to a particular embodiment it is to be understood that modifications can be effected within the scope of the inven- 2 GB2170958A 2 tion. For example, the central element 6 may also comprise a resilient element and furthermore, the resilient elements 8 need not ex- tend at an angle of 20' to the central element 6.

Claims (9)

1. An antenna assembly comprising a cen- tral element extending from a support, a plurality of resilient elements extending from the support and arranged about the central element, and retaining means for maintaining the distal ends of the resilient elements in juxtapo- sition to the central element, and wherein the resilient elements are arranged to deploy, by bias stored therein, to operative positions about the central element when the distal end's thereof disengage the retaining means.

2. An antenna assembly according to claim 1 wherein the operative positions of the resilient elements about the central element form a substantially conical array of resilient elements with the central element extending from the apex of the substantially conical array.

3. An antenna assembly according to claim 2 wherein the resilient elements in the sub stantially conical array extend at an angle in the range of 15' to 25' with respect to the central element.

4. An antenna assembly according to any one of claims 1 to 3 wherein the central element comprises a resilient element.

5. An antenna assembly according to any one of the preceding claims comprising six resilient elements.

6. An antenna assembly according to any one of the preceding claims wherein the support comprises a connection terminal for the antenna assembly.

7. An antenna assembly according to any one of the preceding claims wherein the distal ends of the resilient elements are linked to the central element by flexible restraining means to provide support for the distal ends of the resilient elements in the operative positions.

8. An antenna assembly according to any one of the preceding claims wherein the resilient elements comprise spring steel.

9. An antenna assembly substantially as hereinbefore described with reference to the accompanying drawing.

Printed in the United Kingdom for Her Majesty's Stationery Office, Dd 8818935, 1986. 4235. Published at The Patent Office, 25 Southampton Buildings, London, WC2A 1 AY, from which copies may be obtained.