EP0194749A2

EP0194749A2 - Collapsible antenna assembly

Info

Publication number: EP0194749A2
Application number: EP86300869A
Authority: EP
Inventors: Andrew Philip Cheer
Original assignee: Plessey Overseas Ltd
Current assignee: Plessey Overseas Ltd
Priority date: 1985-02-12
Filing date: 1986-02-10
Publication date: 1986-09-17
Also published as: EP0194749A3; GB8503550D0; GB2170958A

Abstract

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

Description

The present invention relates to antenna assemblies.
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 desired bandwidth for transmission.
The bandwidth of single element antenna structures can be increased significantly by providing a plurality of elements which are disposed 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 approximately 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 antenna making it impractical for many applications.
It is an object of the present invention to provide a collapsable antenna assembly which can be manufactured relatively cheaply compared to known designs of antenna assemblies.
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 element, and retaining means for maintaining the distal ends of the resilient elements in juxtaposition to the central element, and wherein the resilient elements deploy, by bias stored therein, to operative positions about the central element when the distal ends thereof disengage the retaining means.
Preferably the operative positions of the resilient 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 element.
Conveniently the resilient elements comprise 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 resilient 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 invention. For example, the central element 6 may also comprise a resilient element and furthermore, the resilient elements 8 need not extend at an angle of 20° to the central element 6.

Claims

1. An antenna assembly characterised by a central 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 juxtaposition 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 ends thereof disengage the retaining means.

2. An antenna assembly according to claim 1 characterised in that 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 characterised in that the resilient elements in the substantially 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 characterised in that the central element comprises a resilient element.

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

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

7. An antenna assembly according to any one of the preceding claims characterised in that 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 characterised in that the resilient elements comprise spring steel.