AU598595B2 - Thin-film circulator with three matched gates - Google Patents

Description

-F 59 8595 Form

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: This document contains the amendments made under Section 49 and is correct for printing.

Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: 0 0 TO BE COMPLETED BY APPLICANT Name of Applicant: !9ame'ns. m.omnu.3cfaCin GT-E-T-ELEGGMUNCI-AZ-IeN-I-Sp.

A.

Address of Applicant: S.S. 11 PADANA SUPERIORE KM 158 20060 CASSINA DE' PECCHI

MILANO

ITALY

CLEMENT HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Actual Inventor: Address for Service: Complete Specification for the invention entitled: THIN-FILM CIRCULATOR WITH THREE MATCHED GATES The following statement is a full description of this invention including the best method of performing it known to me:- L7 -11- "Thin-Film Circulator With Three Matched Gates" The present invention relates to a three-gate thin-film circulator with impedance matching.

A three-gate thin-film circulator is a device which when inserted in a transmission line makes the path nonreciprocal i.e. not two-directional.

If inserted in a microwave branching system said device permits conveyance to a single antenna of the signals of several transmitters or else distribution of signals from said antenna to appropriate receivers. If one of the three matched gates is closed on a matching termination the device ensures decoupling if placed between t0 0 0 0 two microwave circuits or matching if inserted .0 0 oft upstream from the circuit in question.

A known three-gate circulator is made at pres- 0o, ent with a substrate of magnetizable material o00, formed of a garnet or ferrite disk entirely metallized on both sides and inserted in a special oo 00 4hole made in a dielectric substrate. Access thereto is through three transmission lines depos- 0o: ited on the dielectric substrate and arranged at 1200 to each other. If a magnetizable substrate in circular form is not available, one of the sides of the magnetizable substrate is metallized with a circular geometry of appropriate diameter the access to which is likewise obtained with three transmission lines arranged at 1200 on the magnetizable substrate.

2 Said known circulator has several shortcomings, specifically rather large space occupied linked to the diameter of the magnetizable substrate, the need to use impedance transformers to match output impedance to that of the circuit with which it is associated (with the resulting further increase in size) and finally the greater insertion losses introduced by the matching lines.

To overcome these shortcomings there has recently been s0Q0 0 m, o a accomplished another known circulator in which metallization of loop 00100 the accessible face of the magnetizable substrate is no longer 0 Il .o uniformly circular but divided in three distinct areas by narrow 00 0 radial nonconducting segments 1200 apart, the external edges of o o said areas constituting the input and output gates.

This metallization geometry made it possible to reduce the i5 diameter of the magnetizable substrate and hence the space 0.o0. occupied by the device, transmission frequency being equal, but didn't solve the problem of matching. The operation of the 00.0 o~uo .000 circulator was also unsatisfactory.

The object of the present invention is accordirgly to a 0 20 achieve a thin-film three-gate circulator which would occupy little space and display selfmatching impedance characteristics such that no external adapters would be needed.

In accordance with the invention there is provided thinfilm circulator with three gates comprising a substrate of magnetizable material having one face provided with unbroken thin-film metallization and another face provided with thin-film metallization having a geometry such as to describe three ,P~iL1AZ1transmission lines 1200 apart converging at a common centre from i- 1 e 3 respective input and output gates characterized in that said circulator further comprises three other line sections, wherein adjacent pairs of transmission lines are separated by a respective interval, and respective ones of said three other line sections are disposed in respective ones of the intervals between said transmission lines, said three other line sections coming together at said common centre to accomplish impedance matching of said input and output gates to an external circuit.

eoao 0° An embodiment of the present invention takes as its starting oo 1 point the known three-area circulator, reducing the extent of said areas in favour of the intervals between said areas, wherein o there have been inserted respective line sections (stubs) having oau an impedance matching function. The result is a circulator made up of three transmission lines 1200 apart provided with impedance matching units. The space occupied by the circulator is thus 809D eo'° further reduced and the insertion losses otherwise caused by the external matching networks are eliminated.

44000 Two practical examples of the accomplishment of the present invention are illustrated for greater clarity in the annexed o0 e0 S 20 drawings wherein FIG. 1 shows a plan view of a circulator in accordance with the invention made in circular form, FIG 2 shows a cross section along line II-II of FIG. 1 of said circular,

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-L4 FIG. 3 shows a plan view of a circulator in accordance with the invention made in triangular form.

The circulator illustrated in FIGS. 1 and 2 comprises a substrate of magnetizable material 1 made in the form of a garnet or ferrite disc.

One face thereof (the bottom face shown in the drawings) is completely coated with circular thin-film metallization 2, also called "ground plane", while the other face thereof (the top face in the drawings) has thin-film metallization of a I o more complex geometry describing the electrical circuit of the circulator described below.

As shown in FIG. 1 the metallization of the top 0000 face of the substrate 1 comprises three trans- 9 mission lines 3 arranged 1200 apart and converging at a common centre 4 from respective input and 0o output gates 5 which pass through a circular non-metallized periphery of the substrate 1 which is not necessary for the electrical operation of 0 o0o the circulator and serves only to make clear the binput and output gates 5 thereof.

Again as shown in FIG. 1 in the intervals between the transmission lines 3 are placed three more line sections 6 which come together in the common centre 4 and operate as impedance adaptors (stubs).

The conformation of the line sections 6, generally of uniform width up to a terminal narrowing 7 before the common centre 4, is such that the i transmission lines 3 have in turn an innermost line portion 8 of uniform width (and hence impedance) and an outermost line portion 9 of variable width (and hence impedance) in the direction of propagation. The outermost portion 9 communicates with the corresponding input/output gate The circulator of FIGS. 1 and 2 is designed to be inserted in a dielectric substrate on which is made a microwave circuit and together therewith in a container in which there is also housed a magnet capable of supplying a steady magnetic field.

This design is known in itself and is therefore not described and illustrated in detail here.

ooo 000 While it is essential that metallization of the top face (in the drawings) of the substrate 1 have the geometry described with the three transmission lines 3 and three matching line sections 6 it is 0 not essential that said metallization and the circulator in general have a circular conform- Sation. Alternatively there can be provided a o triangular conformation like that shown in FIG. 3 where the same reference numbers as in FIGS. 1 and 2 are used to indicate corresponding parts.

Finally it should be noted that an alternative use of the circulator of FIGS. 1 and 2 or of the one shown in FIG. 3 can call for the deposit directly on the substrate 1 between a gate 5 and the ground plane 2 of a resistance having a value equal to that of the characteristic impedance of 6 the circuit. In this case the circulator functions as a separator, offering low attenuation in one direction and high attenuation in the other.

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Claims (4)

1. 2. Circulator in accordance with claim 1 characterized in 4 that said matching line sections have essentially uniform width with narrowing ends toward said common centre and said 0s*t transmission lines have an innermost portion of constant width and an outermost portion of variable width in the direction of 00 .4 o 14 o 20 propagation.
2. 3. Circulator in accordance with claim 1 characterized in that said metallization of the other face of the substrate is circular in form.
3. 4. Circulator in accordance with claim 1 characterized in that said metallization of the other face of the substrate is of triangular form. PL 5. Circulator in accordance with claim 1 characterized in C:Phat it comprises a resistance of a value equal to that of the 1 characteristic impedance of a microwave circuit with which it is associated placed on said substrate between one of said gates and said .face provided with thin metallization in such a manner as to function as a separator.
4. 6. A circulator substantially as herein described with reference to and as illustrated in any one or more of the accompanying drawings. 0 0 0 A0 o a0o Dated this 3rd day of April, 1990 SIEMENS TELECOMUNICAZIONI S.P.A. 04 a By Its Patent Attorneys: 00 GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia. 0 i 0 04 04 04