GB2201044A

GB2201044A - High frequency waveguide circulator

Info

Publication number: GB2201044A
Application number: GB08703207A
Authority: GB
Inventors: Ann Catherine Gravina
Original assignee: Marconi Electronic Devices Ltd
Current assignee: Marconi Electronic Devices Ltd
Priority date: 1987-02-12
Filing date: 1987-02-12
Publication date: 1988-08-17
Anticipated expiration: 2007-02-12
Also published as: EP0281712A1; GB8703207D0; GB2201044B

Description

J 1 2 0 10 4 4 I/7346/MEDL/CFH

body is present in input- at one port is port. An external circulator such that the field is of the ferrite bodv and when all

HIGH FREQUENCY CIRCULATOR This invention relates to a high frequency circulator in which three signal ports angularly offset by 120 0 from each other are linked at a common point at which a ferrite order that an electromagnetic wave output at a different predetermined magnetic field is applied to the aligned with the axis the ferrite junction and are correctly adjusted for a given entering at a first port is to a second port whilst the third port is_ isolated. Similarly, a signal entering at the second port is transmitted to the third port whilst the first port is isolated, and finally a signal entering at the third port is transmitted to the first port with the second port being isolated. Such devices are conveniently used for separating or combining electromagnetic high frequency signals.

It is generally desired to operate the circulator over a reasonably wide frequency band rather than at a single spot frequency and this can be achieved by adapting the design, but a high degree of geometrical symmetry with respect to all three ports is found to be. essential for proper operation. It can be difficult and time consuming to manufacture high frequency circulators having a magnetic parameters frequency, a signal transmitted sufficiently good wideband operating performance.

particularly as for some kinds of circulator the degree of symmetry is very critical. The present invention seeks to provide an improved circulator.

According to this invention a high frequency circulator - includes a ferrite body located at the junction point of three equally angularly spaced waveguide ports which are capable of supporting propagation of an wave, the ferrite body being in the form which is closely surrounded by dielectric outer surface of which engages with three each wall region being associated with a of ports such that the ferrite body is centrally with respect to the three ports.

material is preferably in the form of a ube which is placed around the electromagnetic of a cylinder material, the wall regions, different pair thereby located The dielectr ic preformed sleeve or cylindrical ferrite body The electric vector of the electromagnetic energy is in the direction of the short wall of a rectangular waveguide channel. The invention is particularly suitable for use with an E-plane circulator:. that is to say. a circulator in which the direction of the electric vector in the waveguide is normal to the axis of the ferrite cylinder. 25 The height of the waveguide will be determined primarily by the operating frequency of the circulator and it is unlikely to coincide with the required length of ferrite body. AcccOrdingly. the ferrite body is preferably k 3 of shorter length than the height of each port.

Conveniently, two short ferrite rod portions which are axially aligned with each other are placed in short dielectric tubes which are each then attached to opposite faces of the waveguides. Alternatively, a common tube can be used to locate the two ferrite rod portions. In each instance the thickness of the wall of the dielectric tube is chosen so as to bridge the space between ferrite rod and the junction points of each pair of ports so as to firmly and securely locate the ferrite' rods in their required position of symmetry. The length and diameter of the ferrite material, and of course the lengths of the dielectric can then be adjusted so as to give the correct electrical and magnetic properties.

The invention is further described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a sectional plan view of an E-plane ferrite circulator, Figure 2 shows a sectional view of the circulator on the line XXI, and Figures 3 and 4 show sectional-views of alternative embodiments of the port of.the circulator.

Referring to Figure 1, there is shown therein a through the central plane of an E-plane In an E-plane circulator, the axis of of the ferrite'is shown in the direction of the shown in Figure 2 and this is aligned with the rl- dielectric sectional view circulator symmetry arrow 1 4 - maximum dimension of a rectangular waveguide channel 2. An external field is applied to the ferrite and the direction of the field is aligned with the arrow 1. The polarity of the external field determines the direction of circulation of the electromagnetic energy.

Conveniently, such a waveguide channel 2 is machined from a pair of conductive metallic blocks 3 and 4, the two blocks mating together exactly so as to constitute the required waveguide structure. It will be seen that there are three ports 11, 12 and 13 which have a junction region at the centre of which is positioned a circular ferrite body'15. It is located in place by a preformed sleeve or tube 16 of dielectric material having a wall thickness which is such that the inner diameter of the tube closely surrounds the ferrite body 15 and the outer surface of the tube fitting closely within the three contact points 17, 18 and 19 at the junction regions of respective pairs of ports 11, 12 and 13. Although in Figure 1, each junction region is in the form of just a line contact with sleeve 16, this need not always be so, and will depend on the geometry of the structure.

one possible configuration of the ferrite body 15 and the dielectric tube is illustrated in Figure 3, in which two relatively thick walled dielectric tubes 20 and 21 surround separate short ferrite rods 22 and 23. Although the tubes do not fit'tigtly on the rods, they are a close fit so that there is negligible clearance between A 1 1 r t them. Similarly the co-operate with the the rods 22 and 23 retained portion.

contact low loss In 1 outer surfaces-of the tubes 20 and 21 contact points 17 18, 19, so that are aligned with each other precisely at the centre The rods and tubes are with the walls 24 and are of the waveguide retained firmly in of the waveguide by means of a (RTM) adhesive such as one known as SilasticúRTV. this construction, the tubes 20 and 21 together with the length and diameter of the ferrite rods 22 and 23 enable the bandwidth of operation of the circulator to be tailored to particular requirements, and they permit the assembly to be quickly and accurately located without the need for setting jigs, machined locating recesses, or-the use of a microscope.

In this example,the rods 22, 23, material known as L3 Lithium Titanium available from MarconiElectronic although other materials are suitable.

dimensions are made from a Zinc Iron Spinel, Devices Limited, Impedance matching is -provided by the sleeve or tubes 20,21 each having an external diameter of 4.95mm, made from "Rexolite 142211, a dielectric made by Oak Materials Group Inc, USA. - The of the E-plane waveguide channel are 10.67 x 4.32mm approximately.

Figure 4 shows an alternative embodiment in which the ferrite rods 25, 26, are located by a common sleeve or tube 27 of dielectric material.

- 6

Claims

1. A high frequency circulator including a ferrite' body located a-t the Junction of three equally angularly spaced waveguide ports which are capable of supporting propagation of an electromagnetic wave, the ferrite body being in the form of a cylinder which is closely surrounded by a dielectric material, the outer surface of which engages with three wall regions, each wall region being associated with a different pair of ports such that the ferrite body is thereby located centrally with respect to the three ports.

2. A circulator as claimed in claim 1 in which the dielectric body is in the form of a preformed tube or sleeve.

3. A circulator as claimed in claim 1 or 2 and wherein it is configured as an E-plane circulator.

4. A circulator as claimedin claim 1, 2 or 3 and wherein the ferrite body does not extend over the full height of the waveguide ports.

5. A circulator as claimed in cl-aim 1, 2, 3 or 4 and.

wherein the ferrite body is in the form of two cylinders mounted coaxially, with the remote ends of the cylinders in contact with opposite surfaces of a waveguide.

6. A circulator substantially as illustrated in and described with reference to the accompanying drawings.

0 A ^91 1 1 i 1 i 1 1 1 f 1/ 1 1 J:

ill 1. A high frequency circulator including a ferrite body located at the jUnction of three angularly spaced waveguide ports which are capable of supporting propagation of an electromagnetic wave, the ferrite body being closely surrounded by a dielectric material, the outer surface of which engages with three wall regions, each wall region being associated with a different pair of ports such that the ferrite body is thereby located centrally with'respect to the three ports.

- 'Z,-. = - 6 A circulator comprising a body defining three or more waveguide ports opening onto a cavity, a ferrite resonator positioned -in the --avity, and a dielectric member which serves to match the impedence of the resonator to each waveguide and whicb,-e.ng.g.-2s the.;aid body at positions -e the resonator correctly between the ports so as to locat in the cavity.

7. A circulator substantially as illustrated i described with reference to the accompany drawings.

n and Published 1988 at The Patent Office, State House, 66"71 High Holborn, London WCIR 47P. Further copies may be obtaineI from The Patent OMce. Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd. St Mary Cray, Kent. Con. 1/87.