# US 7,746,190 B2 · Polarization-preserving waveguide filter and transformer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,746,190 B2 - Document ID: US7746190B2 - Status: Granted - Kind: B2 - Application number: 11/748,969 - Filed: 2007-05-15 - Published: 2007-11-15 - Granted: 2010-06-29 - Earliest claimed: 2006-05-15 - Assignees: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration - Inventors: Felice M. Vanin; Edward J. Wollack - Web page: https://patentgrep.com/patent/US7746190B2 ## CPC - H01P 1/208: Cascaded cavities; Cascaded resonators inside a hollow waveguide structure (H01P1/205 takes precedence) - H01P 3/123: with a complex or stepped cross-section, e.g. ridged or grooved waveguides (H01P3/14 takes precedence) - H01P 5/024: {between hollow waveguides} - H01P: WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE (operating at optical frequencies G02B) ## Abstract A microwave waveguide filter includes an input waveguide section, an output waveguide section, a plurality of resonator sections disposed between the input and output waveguide sections, and a plurality of coupling sections disposed on either side of each of the resonator sections. The input waveguide section, the resonator sections, and the output waveguide section have at least four fold symmetric quadruple ridge cross-sections and the coupling sections have at least four fold symmetric cross-sections. ## Claims ### Claim 1 A waveguide filter, the waveguide filter comprising: an input waveguide section, the input waveguide section supporting two polarization modes that are degenerate in frequency; an output waveguide section; a plurality of resonator sections disposed between the input and output waveguide sections; a plurality of coupling sections disposed on either side of each of the resonator sections, wherein the input waveguide section, the resonator sections, and the output waveguide section comprise at least four-fold symmetric quadruple ridge cross-sections, the cross-sections being four-fold symmetrical along the axis of propagation, and the coupling sections comprise at least four-fold symmetric cross-sections such that polarization of each input mode is preserved. ### Claim 2 (depends on 1) The waveguide filter of claim 1, wherein interior perimeters of the input waveguide section, the resonator sections, the output waveguide section, and the coupling sections are generally square. ### Claim 3 (depends on 1) The waveguide filter of claim 1, wherein interior perimeters of the input waveguide section, the resonator sections, the output waveguide section, and the coupling sections are generally circular. ### Claim 4 (depends on 1) The waveguide filter of claim 1, wherein at least one of an interior perimeter of the input waveguide section, the resonator sections, the output waveguide section, and the coupling sections is generally square, and at least one of the interior perimeters is generally circular. ### Claim 5 (depends on 1) The waveguide filter of claim 1, wherein lengths of the coupling sections decrease from a midpoint of the waveguide filter towards ends of the waveguide filter. ### Claim 6 (depends on 1) The waveguide filter of claim 1, wherein lengths of the resonator sections increase from a midpoint of the waveguide filter towards ends of the waveguide filter. ### Claim 7 (depends on 1) The waveguide filter of claim 1, wherein a number of coupling sections is one greater than a number of resonator sections. ### Claim 8 (depends on 1) The waveguide filter of claim 1, wherein the waveguide filter includes an input waveguide section of approximately 2.0 millimeters, an output waveguide section of approximately 2.0 millimeters, a first coupling section of approximately 0.27 millimeters, a resonator section of approximately 1.27 millimeters, and a second coupling section of approximately 0.63 millimeters. ### Claim 9 (depends on 1) The waveguide filter of claim 1, wherein the waveguide filter includes an input waveguide section of approximately 1.0 millimeters, an output waveguide section of approximately 1.0 millimeters, a first resonator of approximately 1.39 millimeters, a second resonator of approximately 1.08 millimeters, a third resonator of approximately 0.94 millimeters, a first coupling section of approximately 0.08 millimeters, a second coupling section of approximately 0.027 millimeters, a third coupling section of approximately 0.47 millimeters, and a fourth coupling section of approximately 0.47 millimeters. ### Claim 10 (depends on 1) The waveguide filter of claim 1, wherein the waveguide filter includes an input waveguide section of approximately 1.5 millimeters, an output waveguide section of approximately 1.5 millimeters, a first resonator of approximately 1.32 millimeters, a second resonator of approximately 1.06 millimeters, a third resonator of approximately 0.96 millimeters, a fourth resonator of approximately 0.92 millimeters, a first coupling section of approximately 0.1 millimeters, a second coupling section of approximately 0.28 millimeters, a third coupling section of approximately 0.041 millimeters, and a fourth coupling section of approximately 0.046 millimeters. ### Claim 11 (depends on 1) The waveguide filter of claim 1, wherein the quadruple ridge cross-sections include an interior perimeter of approximately 0.75 millimeters, a ridge of approximately 0.2 millimeters, a cross-section of approximately 2.7 ×2.7 millimeters, a ridge height of approximately 1.7 millimeters, and a interior perimeter height of approximately 0.05 millimeters. ### Claim 12 (depends on 1) The waveguide filter of claim 1, the waveguide filter further comprising: a housing, the housing including a number of sides, where the number of sides equals 2·2n, where n is an integer greater than or equal to 1. ### Claim 13 A waveguide filter, the waveguide filter comprising: an input waveguide section, the input waveguide section supporting two polarization modes that are degenerate in frequency; an output waveguide section; a first at least four fold symmetric quadruple-ridge section adjacent the input waveguide section; a plurality of resonator sections disposed between the first quadruple-ridge section and the output waveguide section, a first resonator section being disposed adjacent the first quadruple-ridge section; a plurality of coupling sections alternately disposed between the resonator sections, wherein the input waveguide section, the resonator sections, and the output waveguide section have second, at least four-fold symmetric quadruple ridge cross-sections, the cross-sections being four-fold symmetrical along the axis of propagation, the coupling sections have at least four-fold symmetric cross-sections, and the first quadruple-ridge section adjacent the input waveguide section includes ridges having lengths that are less than lengths of ridges of the second quadruple ridge cross-sections, such that polarization of each input mode is preserved. ### Claim 14 (depends on 13) The waveguide filter of claim 13, wherein interior perimeters of the input waveguide section, the output waveguide section, the first at least four fold symmetric quadruple-ridge section, the plurality of resonator sections, and the plurality of coupling sections are generally square. ### Claim 15 (depends on 13) The waveguide filter of claim 13, wherein interior perimeters of the input waveguide section, the output waveguide section, the first at least four fold symmetric quadruple-ridge section, the plurality of resonator sections, and the plurality of coupling sections are generally circular. ### Claim 16 (depends on 13) The waveguide filter of claim 13, wherein at least one of an interior perimeter of the input waveguide section, the output waveguide section, the first at least four fold symmetric quadruple-ridge section, the plurality of resonator sections, and the plurality of coupling sections is generally circular, and at least one of the interior perimeters is generally square. ### Claim 17 (depends on 13) The waveguide filter of claim 13, wherein lengths of the coupling sections decrease from a midpoint of the waveguide filter towards ends of the waveguide filter. ### Claim 18 (depends on 13) The waveguide filter of claim 13, wherein lengths of the resonator sections increase from a midpoint of the waveguide filter towards ends of the waveguide filter. ### Claim 19 (depends on 13) The waveguide filter of claim 13, wherein a number of coupling sections is equal to a number of resonator sections. ### Claim 20 (depends on 13) The waveguide filter of claim 13, the waveguide filter further comprising: a housing, the housing including a number of sides, where the number of sides equals 2·2n, where n is an integer greater than or equal to 1. ### Claim 21 A transformer, the transformer comprising: a housing with an at least four fold symmetric interior perimeter, the housing including a number of sides, where the number of sides equals 2·2n, where n is an integer greater than or equal to 1; and four ridges disposed at ninety degree intervals inside the interior perimeter, each ridge comprising a series of steps. ### Claim 22 (depends on 21) The transformer of claim 21, wherein ridge length increases along a longitudinal axis of the housing. ### Claim 23 (depends on 21) The transformer of claim 21, wherein the interior perimeter is generally square. ### Claim 24 (depends on 21) The transformer of claim 21, wherein the interior perimeter is generally circular. ### Claim 25 An apparatus, the apparatus comprising: a waveguide filter, the waveguide filter comprising: an input waveguide section, the input waveguide section supporting two polarization modes that are degenerate in frequency; an output waveguide section; a first at least four fold symmetric quadruple-ridge section adjacent the input waveguide section; a plurality of resonator sections disposed between the first quadruple-ridge section and the output waveguide section, a first resonator section being disposed adjacent the first quadruple-ridge section; a plurality of coupling sections alternately disposed between the resonator sections, wherein the input waveguide section, the resonator sections, and the output waveguide section have second, at least four-fold symmetric quadruple ridge cross-sections, the cross-sections being four-fold symmetrical along the axis of propagation, the coupling sections have at least four-fold symmetric cross-sections, and the first quadruple-ridge section adjacent the input waveguide section includes ridges having lengths that are less than lengths of ridges of the second quadruple ridge cross-sections; and a transformer comprising an at least four fold symmetric quadruple ridge cross section having four ridges, each ridge comprising a series of steps wherein ridge length increases along a longitudinal axis in the house, wherein the second end of the transformer is fixed to the waveguide filter such that the four ridges of the transformer abut the quadruple ridge cross section of one of the input and output waveguide sections, such that polarization of each input mode is preserved. ### Claim 26 (depends on 25) The apparatus of claim 25, further comprising: a second transformer identical to the transformer and having its second end fixed to the waveguide filter such that the four ridges of the second transformer abut the quadruple ridge cross section of the other of the input and output waveguide sections. ### Claim 27 An apparatus, the apparatus comprising: a waveguide filter, the waveguide filter comprising: an input waveguide section, the input waveguide section supporting two polarization modes that are degenerate in frequency; an output waveguide section; a plurality of resonator sections disposed between the input and output waveguide sections; a plurality of coupling sections disposed on either side of each of the resonator sections, wherein the input waveguide section, the resonator sections, and the output waveguide section comprise at least four-fold symmetric quadruple ridge cross-sections, the cross-sections being four-fold symmetrical along the axis of propagation, and the coupling sections comprise at least four-fold symmetric cross-sections; and a transformer comprising an at least four fold symmetric quadruple ridge cross section having four ridges, each ridge comprising a series of steps wherein ridge length increases along a longitudinal axis in the house, wherein the second end of the transformer is fixed to the waveguide filter such that the four ridges of the transformer abut the quadruple ridge cross section of one of the input and output waveguide sections, such that polarization of each input mode is preserved. ### Claim 28 (depends on 27) The apparatus of claim 27, further comprising: a second transformer identical to the transformer and having its second end fixed to the waveguide filter such that the four ridges of the transformer abut the quadruple ridge cross section of the other of the input and output waveguide sections. ### Claim 29 A waveguide structure, the waveguide structure comprising: a pair of quadruple ridge waveguide sections having at least four fold symmetry, the waveguide sections supporting two polarization modes that are degenerate in frequency, the four fold symmetry being along the axis of propagation; and a four fold symmetric evanescent section disposed between the pair of quadruple ridge resonator sections, the modes being evanescent along the axis of propagation.