Collapsible Antenna Employing Flexible Tape Radiators

Abstract

A plurality of radiating elements fabricated of flexible thin steel is secured to a telescoping mast. A ground plane is formed of a plurality of similar steel members which are mounted in a plane perpendicular to the mast. Within the mast are cables and auxiliary electrical equipment. The radiating elements, the ground plane elements, and the mast are completely collapsible into a compact package.

Description

The invention relates in general to collapsible antenna and more particularly to an antenna for field use which may be transported in a compact size and rapidly set up.

BACKGROUND OF THE INVENTION

The conventional planar turnstile antenna whose radiating elements are mounted in a horizontal plane has the advantage of transmitting and receiving signals of either right-circular polarization or left-circular polarization, together with a circular pattern symmetry about a vertical or polar axis. For horizontally polarized signals, hemispherical coverage is maintained. However, the antenna is insensitive to vertically polarized signals arriving from the horizon and as a result would have a theoretically infinite ellipticity ratio at the horizon decreasing to a relatively low value at the zenith point.

In order to overcome the attendant disadvantages of prior art antennas while simultaneously providing a compact lightweight, collapsible antenna, the antenna of the present invention provides sensitivity to vertically polarized signals as well as horizontally and circularly polarized signals over the hemisphere of coverage. Further, the antenna provides good elevation pattern coverage in a normal operational environment with a considerable reduction in the multipath propagation effects of the signal resulting in a reduction in the elevation null depth. While the elevation beamwidth of the horizontally polarized component of the signal is reduced because of modifications from conventional planar antennas, this disadvantage is more than overcome by the advantage of increased sensitivity to the vertically polarized component. Further, the resultant antenna is of lightweight, flexible design. Moreover, the antenna can be deployed and erected in a minimum time and contains a minimum number of movable parts. Diplexing and matching electronics components interconnecting the radiating elements are completely encapsulated resulting in a weatherproof package.

SUMMARY OF THE INVENTION

More particularly, the invention comprises a plurality of radiating elements fabricated of flexible thin steel secured to a telescoping mast in a manner which allows them to be easily retracted for storing purposes. When the antenna is operationally deployed, the radiating elements are positioned at an angle of 45.degree. relative to the horizontal and vertical axis of the antenna mast. The ground plane is formed of a plurality of steel members of similar material to that of the radiating elements and which are mounted in a plane perpendicular to the mast of the antenna. Contained within the mast are cables for connecting the radiating elements to external electronics equipment and electrical circuitry for matching the cables to the antenna. The radiating elements and ground plane elements are completely collapsible and the mast is made of tubular sections for telescoping, resulting in a compact package. The advantage of this invention, both as to its construction and mode of operation, will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a preferred embodiment of the antenna setup for transmission or reception of signals;

FIG. 2 shows the antenna of FIG. 1 in its stored position; and

FIG. 3 depicts a cross-sectional view of the radiating elements and ground plane elements of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1 there is shown a preferred embodiment of the antenna set up for transmission or reception of signals in two separate bands of frequencies. The antenna 12 is supported on a mast 14, formed of a plurality of telescoping sections 16, interconnected by collars 17, the bottom section 18 being in the form of a spike which can be driven into the ground. Secured to one of the sections 16 is a guy ring having a plurality of holes 24, therein to which guy wires 26 are tied at one end and secured to spikes 28 thus providing a relatively sturdy package.

Radiating elements 32 are fixed to a top member 34 at one end and extend downwardly and outwardly therefrom at an angle of 45.degree. with the mast 14. Within the top member are normally provided an impedance matching member for matching the radiating elements 32 to the cable within the mast 14. Also a diplexer or multiplexer may be provided within the top member 34 for diplexing or multiplexing the radiating elements into separate cable connections when the antenna is to be used in more than one frequency range.

Illustrated in FIG. 1 are a first set of parasitic elements 36 and a second set of parasitic elements 38 which provide separate ground planes for a high band and low band of frequencies, respectively, dependent upon which frequency band the radiating elements are transmitting or receiving. Elements 36 and 38 are secured at one end to collets 39, 40 respectively, on the mast. The elements 36 and 38 may be expanded simultaneously even though one set may be in use at a time. External connections are made to the cable in the mast through a connector 42 mounted thereon, and a removable cable 44 is secured thereto for connection to a transmitter or receiver or both.

Referring now to FIG. 2, the antenna of FIG. 1 is depicted in its collapsed state. First, the elements 36 are wrapped around the collet 39 and the radiating elements 32 secured over them. These elements are then held together by a cylindrical member 46. Then, the elements 38 are wound around the collet 40 and a cylindrical member 48 which can clear the top of the device is secured around the elements. Then the mast is collapsed and fitted into a storage case. Alternatively, the elements 36 and 38 and their respective collets 39, 40 may be designed so that the elements retract into the collet upon rotation of the collet.

The radiating elements and parasitic elements are normally formed of a thin steel tape which is concave along its length, as shown in cross section in FIG. 3, similar to a flexible steel measuring tape. The tape may be coated with a protective material such as Teflon or Mylar to provide additional environmental protection. The elements may also be formed of good conducting materials other than steel, such as beryllium copper. The telescoping mast normally is made of aluminum tubing which is relatively close fitting and is locked in the extended position by a split-compression ring activated by a collar that squeezes the ring tightly around the tubing.

As can readily be seen, the antenna provides relatively good hemispherical coverage for circularly polarized as well as vertically polarized and horizontally polarized waves. Should it be desirable to enhance antenna response to the vertically polarized signals, vertical reflecting members could be attached to the ends of the parasitic elements 36 and 38.

Further, while the parasitic elements 36 and 38 are shown as four members, it should be understood of course, that more members could be used with resultant slight variations in antenna patterns. Moreover, while four elements have been depicted as radiating elements, it should be understood that other members of elements in multiples of two and greater than four could be used, such as six or eight elements, and a satisfactory circularly polarized wave pattern could be obtained. Also, by allowing the radiating elements to extend downwardly and outwardly at a 45.degree. angle, a satisfactory response to both the horizontally and vertically polarized components can be obtained.

While one set of radiator arms for use with two sets or parasitic elements for two separate frequency bands has been described, it should be understood that a separate set of radiator arms in combination with a separate set of parasitic elements could be used. Moreover, should one set of radiator arms be used in combination with two sets of parasitic elements and if a single transmission cable for each frequency is preferred, resonant circuit components may be located within the mast structure to allow multiple frequency operation and eliminate the need for a diplexer.

It should be further understood that the foregoing disclosure relates only to preferred embodiments of the invention, and it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention.

Claims

We claim:

1. A collapsible antenna for mounting on a mast comprising: a plurality of radiating elements formed of a flexible material secured to said mast, said radiating elements being secured at one end to said mast and extending downwardly and outwardly therefrom a predetermined angle when operational; and a plurality of elements forming a ground plane formed of flexible material and secured to said mast at one end, said ground plane elements extending outwardly in a plane perpendicular to said mast when said antenna is operational, said flexible material comprising conductive tape which collapses to a closed position from an open position when said antenna is not in use.

2. A collapsible antenna in accordance with claim 1 wherein said predetermined angle is 45.degree., said antenna being designed to transmit and receive circularly polarized waves.

3. A collapsible antenna in accordance with claim 1 wherein said radiating elements and said ground plane elements are made of thin flexible steel.

4. A collapsible antenna in accordance with claim 1 wherein said radiating elements and said ground plane elements are of concave shape along their length.

5. A collapsible antenna in accordance with claim 1 wherein said radiating elements are secured to said mast in planes parallel to said mast when stored and said ground plane elements are secured in overlapping arrangement when stored.