Broad-band lumped-element circulator

Abstract

A circulator preferably fabricated using thin film techniques. Broad-band isolation and insertion loss characteristics are obtained in the gigahertz frequency range by replacing the conventional series resonant circuit typically employed in circulation, with three symmetrically arranged lumped parameter LC circuits fabricated by thin-film techniques and having the junctions of the LC elements interconnected through conductive paths, such as inductors, for example.

What is claimed is: 
     
       1. A broad-band thin-film circulator having a plate of ferromagnetic material, means creating a D.C. magnetic field transverse to said plate, at least three arms of mutually insulated thin conductor films formed on one major surface of said plate, terminal members connected respectively to one end of each of said arms; a centrally located conductive film formed on the opposite surface of said plate; means connected respectively to said conductor films for electrically connecting the other ends of said conductor film arms to said central conductive film and including resonant means including LC circuit elements and connected at one end to said central film and electrostatically coupled at the opposite end with the other ends of said conductive film arms, wherein said resonant means comprises three LC series circuit paths each comprising an inductor and capacitor; conductive elements connecting each junction between an inductor and capacitor to every other junction. 
     
     
       2. A circulator as claimed in claim 1, wherein said LC series circuit elements are formed of symmetrical thin film conductor patterns formed on the other major surface of said plate. 
     
     
       3. A circulator as claimed in claim 1, wherein said LC series circuit elements are formed on a major surface of a ceramic plate separate from said ferrite plate and coupled with said ferrite plate. 
     
     
       4. A circulator comprising a substantially disc-shaped body of ferromagnetic material; means creating a D.C. magnetic field transverse to said body;   a thin-film conductive pattern formed on one face of said body said pattern comprising three conductive arms arranged at predetermined equal angles relative to one another;   a circular shaped conductive thin-film formed on the opposite face of said body;   means connecting one end of each arm to said circular-shaped thin-film;   an annular conductive thin-film formed on said opposite face and surrounding said circular shaped thin-film, the thin-films defining an annular space therebetween;   a plurality of thin-film LC circuit paths arranged at predetermined locations within said annular space, each path containing first and second lumped parameter circuit elements joined to one another;   one end terminal of each circuit path being connected to said circular thin-film and the opposite end terminal of each circuit path being connected to said annular shaped thin-film;   a thin-film conductive pattern formed in said annular space for electrically interconnecting the junctions between the first and second lumped parameter elements of each of said series circuits.   
     
     
       5. The circulator of claim 4 wherein said thin-film conductive pattern in said annular space comprises a plurality of inductors each of said inductors being connected between the junctions of a pair of said circuit paths. 
     
     
       6. The circulator of claim 5 wherein first, second and third series circuit paths are provided and are arranged at equi-spaced intervals about said annular space; said plurality of inductors comprising first, second and third inductors arranged at equi-spaced intervals about said annular space and each being electrically connected between the junctions of two associated ones of said series circuit paths.   
     
     
       7. The circulator of claim 6 wherein each of said series circuit paths comprises series connected inductance and capacitance elements.