US3732511A - Waveguide mode filter - Google Patents

Waveguide mode filter Download PDF

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Publication number
US3732511A
US3732511A US00234867A US3732511DA US3732511A US 3732511 A US3732511 A US 3732511A US 00234867 A US00234867 A US 00234867A US 3732511D A US3732511D A US 3732511DA US 3732511 A US3732511 A US 3732511A
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Prior art keywords
strips
mode
modes
lining
filter
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Expired - Lifetime
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US00234867A
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English (en)
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C Den
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AT&T Corp
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Bell Telephone Laboratories Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/16—Auxiliary devices for mode selection, e.g. mode suppression or mode promotion; for mode conversion
    • H01P1/163—Auxiliary devices for mode selection, e.g. mode suppression or mode promotion; for mode conversion specifically adapted for selection or promotion of the TE01 circular-electric mode

Definitions

  • ABSTRACT A waveguide mode filter comprises a plurality of very thin, narrow, axially oriented resistive strips deposited on the inner surface of a dielectric lined waveguide section.
  • the circumferential surface impedance of the strips is essentially purely reactive while the longitudinal or axial surface impedance has significant resistive and reactive components.
  • the strips present high attenuation to non-TE modes and low attenuation to the desired TE, modes thereby providing the same filtering function as helix waveguide while offering the manufacturing advantages of dielec tric lined waveguide.
  • This invention relates to waveguide mode filters and in particular to filters utilizing thin resistive strips on the inner surface of a dielectric lining to change the propagation constants of spurious modes with respect to the desired mode of propagation.
  • the TE circular wave mode is known to be well suited for long distance transmission of high frequency broad band signals because the attenuation of this mode decreases with increasing frequency.
  • waveguides which are large enough to transmit the TE wave mode can also support other unwanted modes. Conversion and reconversion of energy between the TE mode and other modes has a degrading effect on the quality of the transmission. Con sequently, much effort has been directed toward finding ways of preventing the conversion of the TE mode into spurious modes and removing or filtering these spurious modes from the waveguide system.
  • Waveguides containing a thin dielectric lining have been effective in reducing the conversion of the TIE. mode into spurious modes by increasing the difference in phase constants between these modes.
  • Dielectric lined waveguide is relatively easy and economical to manufacture because an outside-in process is used involving placing a dielectric lining in a preformed metal tube which can be made relatively accurately.
  • Helix waveguide is an effective-means of removing or filtering unwanted modes from a waveguide transmis sion system.
  • Helix waveguide is relatively difficult and expensive to manufacture.
  • Helix waveguide is normally formed by an inside-out process involving winding a helix wire on a mandrel and subsequent encasement in a desired tube.
  • the helix waveguide thus obtained is normally not as straight and accurate as dielectric lined waveguide which utilizes preformed metal tubing.
  • vanes of dissipative or resistive material within the waveguide provides one alternative to helix waveguide.
  • Such vanes can comprise separate structures which are inserted in the waveguide or which can be formed within the dielectric lining itself.
  • the vanes primarily affect the attenuation constants and provide a distributed loading effect because of the size of the vanes with respect to the wavelengths of the signals being transmitted. Often, however, a discrete load rather than a distributed load is desirable and more effective mode filters can be obtained by controlling both the attenuation and phase constants.
  • the vanes involving the use of separate structures are difficult to manufacture and therefore relatively costly.
  • the formation of vanes within the dielectric lining itself offers many advantages but may not be possible where very thin dielectric linings are used.
  • a waveguide mode filter which utilizes a plurality of thin resistive strips on the inner surface of the dielectric lining.
  • Very thin, narrow, closely spaced strips of an appropriate material are formed on the inner surface of the lining in the axial direction of the waveguide.
  • the circumferential surface impedance of the strips is essentially reactive while the axial surface impedance has substantial resistive and reactive components.
  • FIG. 1 is a perspective view partly broken away of a waveguide mode filter in accordance with the invention
  • FIG. 2 is a schematic representation of a plane model for the filter of FIG. 1;
  • FIGS. 3A and 3B are respectively illustrations of the interaction of an electromagnetic wave with the wall of the mode filter and a transmission line equivalent representation thereof.
  • FIGS. 4A and 4B are illustrations similar to FIGS. 3A and 38, respectively, for a plane wave having a different polarization.
  • FIG. 1 there is shown a waveguide mode filter 101 comprising a tube 2 of conductive material about the interior surface of which is a dielectric layer 4 so as to form a section of dielectric lined waveguide known in the prior art.
  • Tube 2 can, for example, comprise a copper tube or a copper plated steel tube which can be formed very accurately and layer 4 can comprise polyethylene.
  • the dielectric lined waveguide section is converted into a mode filter by forming a plurality of thin, resistive strips 6 on the inner surface 5 of layer 4.
  • Strips 6 are oriented parallel to the longitudinal axis 1 of filter 101.
  • the thickness 7 of strips 6 is much less than the shortest free space wavelength of the frequencies being transmitted through filter 101. For example, if the shortest free space wavelength is in the order of 3 millimeters, the thickness 7 of strips 6 should be not greater than approximately 300 Angstroms. Strips 6 should appear continuous in the axial or longitudinal direction with respect to the frequencies being transmitted. This condition is essentially satisfied if the length of strips 6 is greater than 10 times the free space wavelength of any frequency of interest.
  • Strips 6 are advantageously formed from a conductive material such as silver. However, because of their small dimensions strips 6 are essentially resistive. Strips 6 can be formed on layer 4 by selective deposition or similar film-forming techniques, by removing portions of a continuous metal layer by selective etching or by other techniques which would be apparent to those skilled in the art.
  • FIG. 2 The interaction of a propagating electromagnetic wave with the cylindrical wall of filter 101 can be ap proximated by a plane wave incident upon a plane surface as illustrated in FIG. 2 in which both the cylindrical coordinates r, d), as shown in FIG. l, and the local rectangular coordinates x, y, z are shown.
  • an electromagnetic wave represented by electric field vector 20 propagating in the direction of the z axis has a plane of incidence 21 parallel to the x-z plane, i.e., parallel to resistive strips 24.
  • vector 20 is polarized as shown by indicator 26 in a direction normal to plane 21, i.e., normal to strips 24, as is shown in FIG.
  • the array of resistive strips 24 can be replaced with an equivalent impedance sheet 26 over a dielectric layer 27 having a thickness 29 and a conducting wall 28.
  • the surface impedance of sheet 26 in the y or :1) direction i.e., equivalent to the impedance of strips 24 in the y or (1) direction, is given by:
  • R and X are the resistive and reactive components, respectively, of the surface impedance.
  • the reactive component X is capacitive in nature with respect to this polarization.
  • the transmission line equivalent for a wave having the foregoing polarization is shown in FIG. 3B in which Z is the wall impedance in the y direction, Z, is the surface impedance defined by equation 1 and Z is the transmission line impedance.
  • the wall impedance can be defined by: Z Z E,,/H ([N tan pt) (R j 8u)/( y p s1 j su) where:
  • E is the electric field in the y direction
  • H is the magnetic field in the z direction
  • # is the permeability of free space
  • s is the permittivity of free space
  • A is the free space wavelength of the frequency of interest.
  • t is the thickness 29 of dielectric layer 27.
  • the array of strips 24 can be replaced by an equivalent impedance sheet 31 having a surface impedance in the z direction of:
  • R and X are the resistive and reactive components, respectively, and the reactive component X is inductive in nature for this polarization.
  • the transmission line equivalent for this polarization is shown in FIG. 4B in which Z is the wall impedance in the z direction, Z is the surface impedance defined by equation (3) and 2, is the transmission line impedance.
  • This wall impedance is given by:
  • E is the electric field in the z direction
  • H is the magnetic field in the y direction
  • N is 1/6.
  • the loss or attenuation of a TE mode through filter 101 is proportional to the magnitude of the real part of Z whereas the attenuation of a non-TE mode is proportional to the magnitude of the real part of Z provided the following conditions are met:
  • the width 23 and spacing 25 of strips 24 are chosen, subject to the previously mentioned constraint of macroscopic homogeneity so that:
  • a mode filter for passing the TE mode and suppressing wave modes having longitudinal current components comprising, in combination:
  • a plurality of thin resistive strips mounted on the inner surface of said lining and extending in the direction of the longitudinal axis of said section, said strips having dimensions and spacings such that the circumferential component of wall impedance of said filter comprises essentially a reactive component and the longitudinal component of wall impedance of said filter comprises both reactive and resistive components so that said TE mode is passed while said wave modes having longitudinal current components are suppressed.
  • Z circumferential component of wall impedance
  • Z longitudinal component of wall impedance
  • a mode filter for passing the TE mode and suppressing non-circular wave modes comprising, in combination:
  • a plurality of thin resistive strips mounted on the inner surface of said lining and extending in the direction of the longitudinal axis of said section.

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  • Control Of Motors That Do Not Use Commutators (AREA)
  • Waveguide Switches, Polarizers, And Phase Shifters (AREA)
US00234867A 1972-03-15 1972-03-15 Waveguide mode filter Expired - Lifetime US3732511A (en)

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US23486772A 1972-03-15 1972-03-15

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US (1) US3732511A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
JP (1) JPS494951A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
CA (1) CA948726A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DE (1) DE2312065A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
FR (1) FR2176038B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
GB (1) GB1384200A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3916355A (en) * 1973-03-24 1975-10-28 Fujikura Ltd Circular TE{HD on {b mode filter
EP1224711A1 (en) * 1999-09-29 2002-07-24 Innovative Technology Licensing, LLC Rectangular waveguide with high impedance wall structure
WO2003043119A1 (en) * 2001-11-12 2003-05-22 Kildal Antenn Consulting Ab Strip-loaded dielectric substrates for improvements of antennas and microwave devices
US20070159277A1 (en) * 2004-02-02 2007-07-12 Tdk Corporation Waveguide of rectangular waveguide tube type
WO2012128866A1 (en) 2011-03-22 2012-09-27 Giboney Kirk S Gap-mode waveguide
US9531048B2 (en) 2013-03-13 2016-12-27 Space Systems/Loral, Llc Mode filter

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS52110875A (en) * 1976-03-12 1977-09-17 Kikkoman Shoyu Co Ltd Production of beef like flavor substance and said flavor imparting agent
DE102023133088B3 (de) 2023-11-27 2024-12-05 Dieter Girlich Rauschfilter für Radarmesssysteme, Radarmesssystem sowie Abschussvorrichtung mit Radarmesssystem

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB603119A (en) * 1944-04-28 1948-06-09 Philco Radio & Television Corp Improvements in or relating to electrically resonant cavities
US2981907A (en) * 1957-10-18 1961-04-25 Hughes Aircraft Co Electromagnetic wave attenuator
US3016502A (en) * 1959-12-23 1962-01-09 Bell Telephone Labor Inc Spurious mode suppressing wave guide
US3078428A (en) * 1959-09-30 1963-02-19 Bell Telephone Labor Inc Spurious mode suppressing wave guide
US3251011A (en) * 1959-11-05 1966-05-10 Bell Telephone Labor Inc Filter for passing selected te circular mode and absorbing other te circular modes
US3275955A (en) * 1963-08-06 1966-09-27 Lignes Telegraph Telephon Dielectric-metal waveguide

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB603119A (en) * 1944-04-28 1948-06-09 Philco Radio & Television Corp Improvements in or relating to electrically resonant cavities
US2981907A (en) * 1957-10-18 1961-04-25 Hughes Aircraft Co Electromagnetic wave attenuator
US3078428A (en) * 1959-09-30 1963-02-19 Bell Telephone Labor Inc Spurious mode suppressing wave guide
US3251011A (en) * 1959-11-05 1966-05-10 Bell Telephone Labor Inc Filter for passing selected te circular mode and absorbing other te circular modes
US3016502A (en) * 1959-12-23 1962-01-09 Bell Telephone Labor Inc Spurious mode suppressing wave guide
US3275955A (en) * 1963-08-06 1966-09-27 Lignes Telegraph Telephon Dielectric-metal waveguide

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Barlow, H. E. M. A Method of Changing the Dominant Mode in a Hollow Metal Waveguide & Its Application to Bends IEE Vol. 106B Supp. 13, 1959, pp. 100 105. *
Karbowiak, A. E. Microwave Propagation in Anisotropic Waveguides IEE Vol. 103 C, 1956, pp. 139 144. *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3916355A (en) * 1973-03-24 1975-10-28 Fujikura Ltd Circular TE{HD on {b mode filter
EP1224711A1 (en) * 1999-09-29 2002-07-24 Innovative Technology Licensing, LLC Rectangular waveguide with high impedance wall structure
US6603357B1 (en) * 1999-09-29 2003-08-05 Innovative Technology Licensing, Llc Plane wave rectangular waveguide high impedance wall structure and amplifier using such a structure
WO2003043119A1 (en) * 2001-11-12 2003-05-22 Kildal Antenn Consulting Ab Strip-loaded dielectric substrates for improvements of antennas and microwave devices
US20050040918A1 (en) * 2001-11-12 2005-02-24 Per-Simon Kildal Strip-loaded dielectric substrates for improvements of antennas and microwave devices
US20070159277A1 (en) * 2004-02-02 2007-07-12 Tdk Corporation Waveguide of rectangular waveguide tube type
US7495533B2 (en) * 2004-02-02 2009-02-24 Tdk Corporation Waveguide of rectangular waveguide tube type having sub ground electrodes
WO2012128866A1 (en) 2011-03-22 2012-09-27 Giboney Kirk S Gap-mode waveguide
US8952678B2 (en) 2011-03-22 2015-02-10 Kirk S. Giboney Gap-mode waveguide
US9531048B2 (en) 2013-03-13 2016-12-27 Space Systems/Loral, Llc Mode filter

Also Published As

Publication number Publication date
DE2312065A1 (de) 1973-09-27
FR2176038B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1977-09-02
FR2176038A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1973-10-26
GB1384200A (en) 1975-02-19
CA948726A (en) 1974-06-04
JPS494951A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1974-01-17

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