GB1561969A

GB1561969A - Apparatus for producing circularly or eliptically polarised electromagnetic radiation

Info

Publication number: GB1561969A
Application number: GB4696375A
Authority: GB
Original assignee: Marconi Co Ltd
Current assignee: BAE Systems Electronics Ltd
Priority date: 1975-11-13
Filing date: 1975-11-13
Publication date: 1980-03-05
Also published as: NL7612526A

Description

(54) IMPROVEMENTS IN OR RELATING TO APPARATUS FOR PRODUCING CIRCULARLY OR ELIPTICALLY POLARISED ELECTROMAGNETIC RADIATION (71) We, THE MARCONI COMPANY LIMITED, a British Company, of Marconi House, New Street, Chelmsford, Essex, CM 1 1PL, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to apparatus for producing circularly or eliptically polarised electromagnetic radiation and is particularly applicable to the transmission of high power microwave energy.

According to this invention there is provided apparatus for producing circularly or eliptically polarised electromagnetic energy comprising means for supplying linearly polarised energy and at least two arrays of cylindrical conductive wires or rods, the arrays being spaced in the direction of propagation of the energy; all the wires or rods being inclined at an angle of substantially 45" to the plane of polarisation of the linearly polarised energy; each array being arranged on the surface of a dielectric sheet; and the arrays being separated by air.

Said arrays may be planar or curved in one plane or in two planes in order to produce optimum circular polarisation over a given sector of space from a primary source constituting the said means for supplying the linearly polarised energy.

The number of arrays will be dependent upon the required frequency band width.

Two arrays of conductors would be utilised for narrow band width applications. As the number of arrays of conductors increases, however, the overall insertion loss increases.

Typically three arrays of conductors would be utilised.

The spacing of the conductors in an array and the spacing of the arrays will be dependent upon the required frequency of operation. Where three arrays of conductors are provided in spaced strata, the spacings of the conductors are preferably such as to provide a binomial distribution of susceptance from the outer to the inner arrays.

The invention is illustrated in and further described with reference to Figure 1 of the drawings accompanying the Provisional Specification and the accompanying Figure 2 in the drawings: Figure 1 is a plan view of one transmission polariser in accordance with the present invention, and Figure 2 is a section along the line A-A of Figure 1.

Referring to Figures 1 and 2, the transmission polariser consists of three arrays 1, 2 and 3 of conductive cylindrical wires or rods mounted on sheets of fibreglass material 5, 6 and 7 respectively. Each array lies in a respective stratum, in this case planar. As best seen from Figure 1, each conductor in each array is inclined at an angle of 45" to the plane of incidence of an electric vector, represented by the arrow 8, of energy transmitted through the polariser in a direction D indicated in Fig. 2. In this particular embodiment, the polariser is intended for operation, at 3 GHz, with a relatively high power density of MW peak or more per square centimetre. Each wire conductor is an eighth of an inch in diameter. The arrangement of the conductors in the three layers is such as to provide a binomial distribution of sus ceptance from the outer arrays 1 and 3 to the inner array 2.

The spaces between the three arrays 1, 2 and 3 are air filled. As has already been mentioned the arrays may be planar, as illustrated, or they may be curved in one or two planes to provide optimum circular polarisation over a given sector of space from a given primary source in the radiation path of which the polariser is positioned during operation.

Claims

WHAT WE CLAIM IS:

1. Apparatus for producing circularly or eliptically polarised electromagnetic energy comprising means for supplying linearly polarised energy and at least two arrays of cylindrical conductive wires or rods, the arrays being spaced in the direction of propagation of the energy; all the wires or rods being inclined at an angle of substantially 45" to the plane of polarisation of the linearly polarised energy; each array being arranged on the surface of a dielectric sheet; and the arrays being separated by air.

2. Apparatus as claimed in claim 1 and wherein said arrays are planar.

3. Apparatus as claimed in claim 1 and wherein each arry is curved in one plane or in two planes in order to produce optimum circular polarisation over a given section of space.

4. Apparatus as claimed in any of claims 1 to 3 comprising only two of said arrays.

5. Apparatus as claimed in any of claims 1 to 3 comprising three of said arrays.

6. Apparatus as claimed in claim 5 and wherein the spacings of the wires or rods is such as to provide a binomial distribution of susceptance from the outer to the inner arrays,

7. Apparatus for transmitting circularly or eliptically polarised electromagnetic energy substantially as herein described with reference to Figure 1 of the drawings accompanying the Provisional Specification and Figure 2 of the drawings accompanying the complete specification.