# US 4,399,415 A · Resonant isolator for maser amplifier > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,399,415 A - Document ID: US4399415A - Status: Granted - Kind: A - Application number: 06/246,778 - Filed: 1981-03-23 - Granted: 1983-08-16 - Earliest claimed: 1981-03-23 - Assignees: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration - Inventors: Robert C. Clauss; Rex B. Quinn - Web page: https://patentgrep.com/patent/US4399415A ## CPC - H01P 1/36: Isolators - H01P: WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE (operating at optical frequencies G02B) ## Abstract An isolator is described for use in a low-noise maser amplifier, which provides low loss across a wide bandwidth and which can be constructed at moderate cost. The isolator (40) includes a train of garnet or ferrite elements (50, 52) extending along the length of a microwave channel (14) parallel to the slow-wave structure (24), with the elements being of staggered height, so that the thin elements (50) which are resonant to the microwaves are separated by much thicker elements (52). The thick garnet or ferrite elements reduce the magnetic flux passing through the thin elements (50), to permit altering of the shape of the thin elements so as to facilitate their fabrication and to provide better isolation with reduced loss, by increasing the thickness (T) of the thin elements and decreasing their length (L) and width (W). ## Claims ### Claim 1 In a traveling wave maser which includes a pumped channel, a maser material strip extending along the channel, a slow wave structure including multiple comb fingers spaced along the channel, and means for applying a magnetic field within said channel, the improvement of an isolator extending along the channel, comprising: a train of isolator portions extending along said channel substantially parallel to said slow wave structure, each isolator portion formed of magnetic material, a first group of said isolator portions formed of microwave resonance isolator material and being spaced apart and with each first isolator portion lying halfway between a postion opposite a pair of adjacent comb fingers, and the isolator portions of said first group having sharply different magnetic permeability under the operating magnetic field in said channel than isolator portions lying between said first isolator portions. ### Claim 2 (depends on 1) The improvement described in claim 1 wherein: said train includes first isolator elements of a first thickness forming the isolator portions of said first group, and second isolator elements which are at least twice as thick as said first elements and which lie between said first elements. ### Claim 3 (depends on 2) The improvement described in claim 2 wherein: each of said second elements fills the entire space between each pair of first elements to thereby precisely separate the first elements. ### Claim 4 A maser amplifier comprising: a housing having walls forming a channel; a strip of maser material extending along said channel and having a first face lying against a channel wall; a slow wave structure extending along said channel parallel to and adjacent to said maser material strip along a second face of the strip which is opposite said first face; and an isolator structure extending along said channel parallel to said maser strip and lying on a side of said slow wave structure which is opposite said maser strip; said isolator structure including a substantially continuous strip of microwave resonance isolator material, extending parallel to said strip, said strip of isolator material having a variable thickness. ### Claim 5 (depends on 4) The amplifier described in claim 4 wherein: said slow wave structure includes a plurality of fingers spaced from one another along the length of said channel; and said strip of isolator material includes thin portions lying at positions opposite the spaces between said fingers and thick portions that are at least twice as thick as said thin portions lying between said thin portions. ### Claim 6 (depends on 4) The amplifier described in claim 4 wherein: said strip of isolator material includes thick and thin portions, each portion being formed of a separate block of material, and said blocks abut one another to form a substantially continuous strip. ### Claim 7 An isolator for attenuating signals propagating in the reverse direction along a waveguide, comprising: a train of blocks of microwave resonance isolator material of staggered height. ### Claim 8 (depends on 7) The isolator described in claim 7 wherein: said isolator material is chosen from the group which includes yttrium iron garnet and ferrite material. ### Claim 9 An isolator for attenuating signals propagating in the reverse direction along a waveguide, comprising: a train of block portions of soft magnetic material, with at least first alternate block portions formed of microwave resonance isolator material, and with the second block portions lying between said first portions and having a much greater permeability than said first portions. ### Claim 10 (depends on 9) The isolator described in claim 9 including: walls forming a maser amplifier channel; a maser strip extending along said channel; a slow wave structure extending beside said maser strip and forming regions of circularly polarized microwave energy when microwaves pass therealong; and means for applying a magnetic field through said maser strip and in regions adjacent thereto; said train of block portions extending along said channel, with said first block portions lying in said regions of circularly polarized energy. ### Claim 11 (depends on 9) The isolator described in claim 9 wherein: said second block portions are thicker than said first block portions.