US3659228A - Strip-type directional coupler having elongated aperture in ground plane opposite coupling region - Google Patents

Strip-type directional coupler having elongated aperture in ground plane opposite coupling region Download PDF

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Publication number
US3659228A
US3659228A US59479A US3659228DA US3659228A US 3659228 A US3659228 A US 3659228A US 59479 A US59479 A US 59479A US 3659228D A US3659228D A US 3659228DA US 3659228 A US3659228 A US 3659228A
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Prior art keywords
conductors
phase velocity
coupling region
odd
strip
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Expired - Lifetime
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US59479A
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English (en)
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Louis Sebastian Napoli
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RCA Corp
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RCA Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P5/00—Coupling devices of the waveguide type
    • H01P5/12—Coupling devices having more than two ports
    • H01P5/16—Conjugate devices, i.e. devices having at least one port decoupled from one other port
    • H01P5/18—Conjugate devices, i.e. devices having at least one port decoupled from one other port consisting of two coupled guides, e.g. directional couplers
    • H01P5/184—Conjugate devices, i.e. devices having at least one port decoupled from one other port consisting of two coupled guides, e.g. directional couplers the guides being strip lines or microstrips
    • H01P5/185—Edge coupled lines

Definitions

  • ABSTRACT A compact, microstrip directional coupler is described wherein two narrow strip-like conductors are closely spaced to each other so as to provide a signal coupling region therebetween.
  • the two narrow conductors are spaced from a ground planar conductor by a substrate of dielectric material having a relatively high dielectric constant compared to the adjacent medium wherein the odd mode phase velocity of a signal propagating along the coupler is unequal to the even mode phase velocity thereof.
  • An elongated aperture is located in the ground planar conductor in the coupling region to alter the odd mode phase velocity so that it is equal to the even mode phase velocity.
  • microstrip transmission line
  • This microstrip can be fabricated by the use of low cost printed circuit techniques and when using relatively high dielectric constant material is very compact in size.
  • Microstrip directional couplers wherein two such narrow strip-like conductors are closely spaced from a common ground planar'conductor and are closely spaced from each other along a given coupling region are known.
  • Microstrip directional couplers using relatively high dielectric constant material are however relatively recent and have been associted with miniaturized microwave devices and systems.
  • first and second narrow strip-like conductors are spaced from a ground planar conductor.
  • the first and second narrow strip-like conductors are closely spaced to each other andto the ground planar conductor so as to provide an electromagnetic coupling region therebetween.
  • these signals propagate in the odd and even mode along the coupling region of the coupler.
  • the spacing between the narrow strip-like conductors and the ground planar conductor is provided by a substrate having a dielectric constant of at least six causing the inherent phase velocity of signals propagating in the odd mode to be substantially different from the signals in the even mode.
  • the odd mode only is perturbed sufficiently to an extent such that the odd mode phase velocity is equal to the even mode phase velocity.
  • FIG. 1 is a top plan view of a prior art directional coupler
  • FIG. 2 is a cross sectional view of FIG. 1 illustrating odd mode propagation
  • FIG. 3 is a cross sectional view of FIG. 1 illustrating even mode propagation
  • FIG. 4 is a top plan view of a directional coupler in accordance with the principles of the present invention.
  • FIG. 5 is a cross sectional view of the coupler of FIG. 4 taken along axis 5-5, and
  • FIG. 6 is a plot of coupling versus frequency for a directional coupler of the type following the principles of the present invention.
  • FIGS. 1 and 2 there is illustrated a perspective view of a prior art edge coupled microstrip directional coupler 10.
  • Two narrow strip-like conductors 13 and 15 are fixed to one surface of a dielectric substrate 11.
  • a closely spaced ground planar conductor 12 is located on the opposite surface of the substrate 11.
  • the conductors 13 and 15 are closely spaced to each other over a coupling region 17 which is usually about a quarter of a wavelength along at the center operating frequency of the coupler.
  • Electromagnetic signals coupled across conductors l3 and 12 at one end 16 propagate along conductor 13 toward the opposite end 18.
  • the electromagnetic signal energy propagating along this coupling region 17 propagates in both odd and even mode.
  • the voltage at one of the conductors 13 is positive with respect to the ground conductor 12, and the'voltage at the other narrow conductor 15 is negative with respect to ground conductor 12.
  • the current in the odd mode as indicated by ar- I rows 19 and 21 is in one direction (into the paper of FIG. 2) along conductor 13 and in an opposite direction (out of the paper of FIG. 2) along conductor 15.
  • the electric field of the electromagnetic signal energy is between the narrow conductors 13 and 15 with a sub stantial portion thereof being located outside of the substrate 1 1
  • FIG. 3 there is illustrated the even mode condition wherein the voltages on the conductors 13 and 15 are both positive with respect to the ground planar conductor 12. The currents travel along the conductors 13 and 15 for the even mode condition, as indicated by arrows 24 and 25 into the paper and arrow 26 out of the paper, in the same direction, and there is no transverse current associated with the even mode condition.
  • the electric field as indicated by the dashed arrows is mainly within the substrate 11.
  • the electromagnetic signal energy propagating along conductor 13 from end 16 toward end 18 is coupled to a given terminal end 21 of conductor 15.
  • the ratio of the coupled energy to one terminal end 21 'of conductor 15 with respect to the other end 23 of conductor 15 is the directivity.
  • High directivity is dependent on the phase velocities of the even and odd mode being equal. If the even and odd mode phase velocities are substantially different, the directivity deteriorates substantially and becomes lower as the velocity difference increases.
  • FIGS. 4 and 5 there is illustrated a coupler 30 comprising a dielectric substrate 31 having a ground planar conductor 32 on one surface and the narrow strip-like conductors 33 and 35 closely spaced at coupling region 37 to each other on the opposite surface of said substrate 31.
  • the narrow the narrow conductors 33 and 35 Referring to the cross sectional view of FIG. 5, this aperture or slot 38 is placed in the ground planar conductor 32 such as to be centered below the coupling region 37.
  • FIGS. 2 and 3 it is noted that in the even mode excitation, there is no component of current at the ground plane transverse to the direction of propagation of the signals, but there is a component of current for the odd mode excitation that is transverse to the direction of propagation of the signals.
  • the transverse odd mode current as indicated by arrow 22 of FIG. 2 is interrupted, but the even mode current is not.
  • the odd mode inductance can be adjusted so that the odd and even mode phase velocities are substantially equal.
  • the width of the slot 38 is increased.
  • a highly directional coupler as illustrated in FIGS. 4 and 5 was operated at a frequency range of from 2 to 6 GHz and had the following dimensions: I
  • Narrow strip-like conductors 33 and 35 were 0.0145 inch wide and were 2 to 3 microns thick copper
  • Ground conductor 32 was 2 to 3 microns thick copper
  • Coupling region 37 was about 7.4 mm. long
  • Coupling distance between conductors 33 and 35 at region 37 was 0.0075 inch
  • Substrate 31 was 99.5% A1 0 material, dielectric constant of 10.4 and was 0.025 inch thick.
  • FIG. 6 there is illustrated the improved directivity of the above-described coupler for signals within the 2 to 6 gigahertz frequency region applied at terminal 39.
  • Plot a of F IG. 6 illustrates the coupled power in decibels at the desired terminal43 relative to the input power applied at terminal 39.
  • Plot b of FIG. 6 illustrates the coupled power in decibels at the undesired terminal 45 relative to the input power at terminal 39.
  • plot a it is shown that signals within the 2 to 6 gigahertz frequency region applied at terminal 39 of the above coupler are coupled about 10 db down to terminal 43.
  • plot 12 it is shown that signals within the 2.to 6 gigahertz frequency region applied at terminal 39 of the above coupler are coupled about 30 db down to terminal 45.
  • the directivity, the relative power at terminal 43 relative to terminal 45 was 20 db. This amounts to an improvement on the order of 10 to 15 db for a similar coupler as described above without the aperture in the ground planar conductor.
  • a directional coupler of the type comprising:
  • a dielectric substrate a pair of narrow strip-like conductors on one surface of said dielectric substrate, , a single ground planar conductor on the surface of said substrate opposite said one surface so as to be spaced directly opposite said strip-like conductors, said pair of narrow strip-like conductors being closely spaced to each other and to said ground planar conductor so as to provide an electromagnetic coupling region between said strip-like conductors so that electromagnetic signals applied to said coupler are propagated in odd and even modes along said pair of conductors at said region, said substrate having a dielectric constant of at least six causing a marked difference between the phase velocity of signals propagating in the odd mode and in the even mode, said ground planar conductor having an elongated aperture which extends along said surface opposite said one surface and directly opposite and parallel to said region for perturbing the odd mode sufficiently so that said odd mode phase velocity eqlual said even mode Phase velocity.

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US59479A 1970-07-30 1970-07-30 Strip-type directional coupler having elongated aperture in ground plane opposite coupling region Expired - Lifetime US3659228A (en)

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US5947970A 1970-07-30 1970-07-30

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US (1) US3659228A (fr)
JP (1) JPS5210345B1 (fr)
AU (1) AU463605B2 (fr)
CA (1) CA927938A (fr)
DE (1) DE2138315A1 (fr)
FR (1) FR2112191B1 (fr)
GB (1) GB1302658A (fr)
NL (1) NL7110480A (fr)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3961296A (en) * 1975-03-06 1976-06-01 Motorola, Inc. Slotted strip-line
US3970927A (en) * 1973-11-30 1976-07-20 Plessey Handel Und Investments A.G. Method and apparatus including a sensing head with a pair of strip transmission lines for detecting metallic objects
JPS51132948A (en) * 1975-05-15 1976-11-18 Nippon Telegr & Teleph Corp <Ntt> Distribution coupling type directional coupler
US4211986A (en) * 1977-07-25 1980-07-08 Tokyo Shibaura Denki Kabushiki Kaisha Strip line coupler having spaced ground plate for increased coupling characteristic
US4375054A (en) * 1981-02-04 1983-02-22 Rockwell International Corporation Suspended substrate-3 dB microwave quadrature coupler
US4737740A (en) * 1983-05-26 1988-04-12 The United States Of America As Represented By The Secretary Of The Navy Discontinuous-taper directional coupler
US4792773A (en) * 1985-09-20 1988-12-20 Thomson-Csf Ultra high frequency circuit with low parasite capacities
EP0415558A2 (fr) * 1989-08-31 1991-03-06 NGK Spark Plug Co. Ltd. Filtres passe-bande et méthode d'ajustage de leur caractéristique de réponse
US5138287A (en) * 1990-05-11 1992-08-11 Hewlett-Packard Company High frequency common mode choke
US5446425A (en) * 1993-06-07 1995-08-29 Atr Optical And Radio Communications Research Laboratories Floating potential conductor coupled quarter-wavelength coupled line type directional coupler comprising cut portion formed in ground plane conductor
US5561378A (en) * 1994-07-05 1996-10-01 Motorola, Inc. Circuit probe for measuring a differential circuit
EP0735605A1 (fr) * 1995-03-28 1996-10-02 Nippon Telegraph And Telephone Corporation Ligne de transmission à couches multiples avec conducteur de masse à fente, et circuit hybride l'utilisant
US6323741B1 (en) * 1998-10-13 2001-11-27 Lg Electronics Inc. Microstrip coupler with a longitudinal recess

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3228993A1 (de) * 1982-08-03 1984-02-09 Siemens AG, 1000 Berlin und 8000 München Mikrowellen-microstrip-mehrleitersystem, bestehend aus n parallelen streifenleitern
AT393048B (de) * 1987-04-17 1991-07-25 Siemens Ag Oesterreich Richtkoppler in mikrostrip-technik
JPH10173413A (ja) * 1996-12-16 1998-06-26 Murata Mfg Co Ltd 結合線路および結合線路の作成方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2951218A (en) * 1957-02-19 1960-08-30 Itt Directional couplings
US3094677A (en) * 1960-12-19 1963-06-18 Bell Telephone Labor Inc Strip line wave guide coupler
US3480884A (en) * 1968-08-26 1969-11-25 Hewlett Packard Co Electromagnetic wave energy coupling apparatus comprising an anisotropic dielectric slab
US3512110A (en) * 1968-05-06 1970-05-12 Motorola Inc Microstrip-microwave coupler
US3575674A (en) * 1969-05-09 1971-04-20 Microwave Ass Microstrip iris directional coupler

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2951218A (en) * 1957-02-19 1960-08-30 Itt Directional couplings
US3094677A (en) * 1960-12-19 1963-06-18 Bell Telephone Labor Inc Strip line wave guide coupler
US3512110A (en) * 1968-05-06 1970-05-12 Motorola Inc Microstrip-microwave coupler
US3480884A (en) * 1968-08-26 1969-11-25 Hewlett Packard Co Electromagnetic wave energy coupling apparatus comprising an anisotropic dielectric slab
US3575674A (en) * 1969-05-09 1971-04-20 Microwave Ass Microstrip iris directional coupler

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3970927A (en) * 1973-11-30 1976-07-20 Plessey Handel Und Investments A.G. Method and apparatus including a sensing head with a pair of strip transmission lines for detecting metallic objects
US3961296A (en) * 1975-03-06 1976-06-01 Motorola, Inc. Slotted strip-line
JPS51132948A (en) * 1975-05-15 1976-11-18 Nippon Telegr & Teleph Corp <Ntt> Distribution coupling type directional coupler
US4211986A (en) * 1977-07-25 1980-07-08 Tokyo Shibaura Denki Kabushiki Kaisha Strip line coupler having spaced ground plate for increased coupling characteristic
US4375054A (en) * 1981-02-04 1983-02-22 Rockwell International Corporation Suspended substrate-3 dB microwave quadrature coupler
US4737740A (en) * 1983-05-26 1988-04-12 The United States Of America As Represented By The Secretary Of The Navy Discontinuous-taper directional coupler
US4792773A (en) * 1985-09-20 1988-12-20 Thomson-Csf Ultra high frequency circuit with low parasite capacities
EP0415558A2 (fr) * 1989-08-31 1991-03-06 NGK Spark Plug Co. Ltd. Filtres passe-bande et méthode d'ajustage de leur caractéristique de réponse
EP0415558A3 (en) * 1989-08-31 1992-04-22 Ngk Spark Plug Co. Ltd. Bandpass filter and method of trimming response characteristics thereof
US5138287A (en) * 1990-05-11 1992-08-11 Hewlett-Packard Company High frequency common mode choke
US5446425A (en) * 1993-06-07 1995-08-29 Atr Optical And Radio Communications Research Laboratories Floating potential conductor coupled quarter-wavelength coupled line type directional coupler comprising cut portion formed in ground plane conductor
US5561378A (en) * 1994-07-05 1996-10-01 Motorola, Inc. Circuit probe for measuring a differential circuit
EP0735605A1 (fr) * 1995-03-28 1996-10-02 Nippon Telegraph And Telephone Corporation Ligne de transmission à couches multiples avec conducteur de masse à fente, et circuit hybride l'utilisant
US5634208A (en) * 1995-03-28 1997-05-27 Nippon Telegraph And Telephone Corporation Multilayer transmission line using ground metal with slit, and hybrid using the transmission line
US6323741B1 (en) * 1998-10-13 2001-11-27 Lg Electronics Inc. Microstrip coupler with a longitudinal recess

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Publication number Publication date
AU3126871A (en) 1973-01-18
CA927938A (en) 1973-06-05
AU463605B2 (en) 1975-07-31
GB1302658A (fr) 1973-01-10
FR2112191A1 (fr) 1972-06-16
FR2112191B1 (fr) 1976-09-03
JPS5210345B1 (fr) 1977-03-23
NL7110480A (fr) 1972-02-01
DE2138315A1 (de) 1972-02-03

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