US2533239A - Impedance transformer for coaxial lines - Google Patents

Impedance transformer for coaxial lines Download PDF

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Publication number
US2533239A
US2533239A US639290A US63929046A US2533239A US 2533239 A US2533239 A US 2533239A US 639290 A US639290 A US 639290A US 63929046 A US63929046 A US 63929046A US 2533239 A US2533239 A US 2533239A
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United States
Prior art keywords
conductors
section
impedance
line
conductor
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Expired - Lifetime
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US639290A
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English (en)
Inventor
Gent Alfred Walter
Wallis Peter John
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International Standard Electric Corp
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International Standard Electric 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
    • H01P5/02—Coupling devices of the waveguide type with invariable factor of coupling
    • H01P5/022—Transitions between lines of the same kind and shape, but with different dimensions
    • H01P5/026—Transitions between lines of the same kind and shape, but with different dimensions between coaxial lines

Definitions

  • the inner or outer conductors having different diameters.
  • a section of coaxial transmission line having conductors whose diameters at one end are equal to the diameters of the conductors of said line and decrease or increase gradually in the direction of the desired conductor change to the other end of the said section so that there are no discontinuous steps in conductor size anywhere, and said section having an electrical length equal to an integral number of half-wavelengths at the operating freu quency.
  • coaxial cables are usually ernployed for wide frequency bands and it is usually not suflicient to match a coaxial conductor transmission line as regards the impedance at one frequency only by an impedance transformer. It is another object of this invention to provide a coaxial section impedance matching trans former for transforming over a wide band oi' yfrequencies the impedance of a coaxial conductor transmission line to a line of another impedance.
  • This object is attained in accordance with the present invention by providing a section of tapered coaxial conductor transmission line, having conductor diameters at one end equal to the diameters of the conductors of the line to Awhich said section is connected, said section conductors tapering in opposite directions with such tapers as to produce on said transmission line unity standing wave ratio at the mid band operating frequency and having an electrical length equal substantially to an integral number of half-wave-lengths at said mid-band frequency.
  • Another object of the invention is to provide an impedance transformer for transforming over a wide band of operating frequencies the impedance of a coaxial conductor transmission line to a given impedance coaxial conductor transmission line having one conductor of predetermined diameter.
  • a transformer according to this invention comprises two series connected sections of tapered coaxial transmission line, one of said sections having conductor diameters at one end equal to the diameters of the conductors of the line to which said section is connected, said section conductors tapering in opposite directions with such tapers as to produce on said transmission line unity standing wave ratio at the said mid-band operating frequency and having an electrical length equal substantially to an integral number of halfwave-lengths at said mid-band frequency, and the other section having conductors tapering in the same direction from the dimensions of the conductors at the junction of said two sections to the dimensions of the conductors of the line of known impedance having a conductor of known diameter.
  • the outer or inner conductors of the two transmission lines to be coupled have the same radius it is ⁇ thus desirable to taper both conduct tors of the coupling section impedance transformer in opposite ways from the diameters o' the conductors of one transmission line for a half-wave-length of the said mid-band frequency and then in the same direction tothe diameters of the conductors of the other transmission line.
  • Figs. l to 6 each show in longitudinal section an impedance transformer according to the present invention connecting together two coaxial conductor transmission lines of different conductor radial dimensions.
  • Fig. '7 shows' several curves used in the description and Fig'. 8 shows a curve of Fig. 7 extended to greater limits than in Fig. 7.
  • Fig, 1 two coaxial conductor lines indicated as line I and line 2.
  • the outer conductors 3, 4 of these two lines have different diameters as also the inner conductors 5, 6, and hence the lines have different characteristic impedances Z1 and Zz respectively.
  • These lines I and 2 are coupled by a coaxial line impedance transformer 1, 8 whose outer conductor 9 tapers from the larger conductor 3 to the smaller conductor 4 and whose inner conductor l tapers in the reverse direction from the larger conductor 6 to the smaller conductor 5.
  • a coaxial line impedance transformer 1, 8 whose outer conductor 9 tapers from the larger conductor 3 to the smaller conductor 4 and whose inner conductor l tapers in the reverse direction from the larger conductor 6 to the smaller conductor 5.
  • Such a general arrangement does not provide a good impedance match between the lines l and 2.
  • the optimum length of connecting section to use is one whose electrical length is an integral number of half-wave-lengths at the operating frequency.
  • the reactance X can be brought to a minimum by the use of a connecting section an integral number of half-wave lengths long, it cannot be brought to zero if only one of the conductors is tapered. To make the reactance zero, it is necessary to taper both c'onductors in a uniquely determinate way, as will be explained hereinafter.
  • the standing wave ratio 0 for any standing wave is the ratio of the maximum root mean square voltage measured at the voltage antipodes to the minimum root mean square voltage measured at the voltage nodes.
  • the input impedance Zin to a quarter wave transducer is given by:
  • the curve C of standing wave ratio against wavelength in this case is very flat, and for large enough departures from the central frequency the curve C crosses the curve A for the quarter wave stepped uniform line and thereafter lies below it.
  • the singly tapered line is preferred to the stepped uniform line, for although the standing wave ratio is worse than for the stepped uniform line at the centre of the band, if the band is wide the standing wave ratio will be better at the edges of the band than for the stepped uniform line.
  • the optimum doubly tapered line is better both at the centre and edges of the band, and is much to be preferred.
  • the two impedances Z1 and Z2 between which to match and the size of either one or both of the lines will be known.
  • R1 and R3 are the radii of the inner and outer conductors of one line, impedance Z1, and R2, R4 the radii of the inner and outer conductors of the other coaxial line of characteristic impedance Z2.
  • the section II connected to the line I has the optimum length of one half the wavelength of the mid-band frequency the diameters of the conductors at the end of the section I3--I4 being determined as hereinbefore described so that lea e E
  • the conducto-rs of the other section I2 are then tapered up from dimensions of R5 and Re at the connecting plane I3I4 to dimensions R2 and R4 respectively such that Thus if R2 or R4 is known, the other is determined accordingly.
  • the inner 1 'conductors of the two lines I and 2 have the same diameters, but the outer conductors have different diameters.
  • the outer conductors have the same diameters but the inner conductors have different diameters.
  • the sections II are given the optimum length of half a wave-length of the mid-band frequency but the section I2 may be of any convenient length.
  • Figs. 5 and 6 are the reverse cases of those shown respectively in Figs. 3 and 4. In all these Icases, it will be observed that in the section I I having the optimum length of half wave-length the inner and outer conductors taper in opposite directions while in the section I2, the inner and outer conductors taper in the same direction.
  • the lengths of the sections I2 are shown as being different in all four cases, sin'ce there is no restrictive condition on this length.
  • the lengths of the tapered sections in which the tapering is in the opposite sense in the two conductors, may be of course made an integral number of half wave-lengths long, but there is tor 6.,. little to be gained by using more than one half wave-length.
  • sections where the tapering is in the same sense in the two lines i. e. where mere scaling up or down is carried out, there is no restriction to half wavelength sections.
  • These latter sections may be of any length.
  • An impedance matching section for transforming over a wide band of operating frequencies the impedance of a coaxial conductor transmission line to the impedance of another coaxial conductor transmission line comprising a section of tapered coaxial conductor transmission line having conductor diameters at one end equal to the diameters of the conductors of one of the lines to which said section is to be connected, said section conductors tapering in opposite directions and having an electrical length equal substantially to an integral number of half wave-lengths at the mid frequency of the operating band, said section conductors further tapering in the direction to the diameters of the other line to which the section is to be connected.
  • An impedance matching transformer for transforming over a wide frequency band the impedance of a coaxial conductor transmission line to a given impedance coaxial conductor line having one conductor of predetermined diameter comprising two series connected sections of tapered coaxial transmission lines, one of said sections having conductors tapering in opposite directions andhaving an electrical length equal substantially to an integral multiple including unity, of one half wave-length at the mid-frequency of the operating band and the other section having conductors tapering in the same direction from the dimensions of the conductors at the junction of said two sections to the dimensions of the conductors of the line to which said other section is to be connected.
  • An impedance matching section for transforming the impedance Z1 of a coaxial conductransmission line having conductors of diameters R1 and R3 to an impedance Z2 of another coaxial conductor transmission line having conductors of diameters R2 and R4 by transforming the diameters of the inner and outer conductors respectively, comprising a section of coaxial transmission line having conductors whose diameters at one end are equal respectively to R1 and R3 and which taper in opposite directions to diameters R5 and Re respectively, said section having an electrical length equal to an integral number of half wave lengths at the REFERENCES CITED Operatmg frequency the (hamsters R5 R6 being The following references are of record in the such that file of this patent:
  • Ro 626 r UNITED STATES PATENTS l E: e Number Name Date t v 1,841,473 Green Jan. 19, 19132 and a second section of coaxlal transmisslon line 1,932,443 Clavier Octl 21I 1933 having conductors Whose diame ers a one end OTHER REFERENCES are equal respectively to Rs and R6 and which 10 taper to diameters R2 and R4.

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  • Non-Reversible Transmitting Devices (AREA)
  • Microwave Amplifiers (AREA)
US639290A 1944-11-16 1946-01-05 Impedance transformer for coaxial lines Expired - Lifetime US2533239A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB268056X 1944-11-16

Publications (1)

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US2533239A true US2533239A (en) 1950-12-12

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US639290A Expired - Lifetime US2533239A (en) 1944-11-16 1946-01-05 Impedance transformer for coaxial lines

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US (1) US2533239A (xx)
CH (1) CH268056A (xx)
FR (1) FR58156E (xx)
GB (1) GB586619A (xx)
NL (2) NL69844C (xx)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2859418A (en) * 1955-06-21 1958-11-04 Joseph H Vogelman High power transmission line filters
US2938182A (en) * 1955-11-18 1960-05-24 Raytheon Co Microwave tube output coupling
US4283694A (en) * 1978-07-11 1981-08-11 U.S. Philips Corporation Impedance-matching network realized in microstrip technique
US4853656A (en) * 1987-08-03 1989-08-01 Aerospatiale Societe Nationale Industrielle Device for connecting together two ultra-high frequency structures which are coaxial and of different diameters
US6222500B1 (en) * 1998-05-08 2001-04-24 Telefonaktiebolaget Lm Ericsson (Publ) Device for impedance adaption
US20090278622A1 (en) * 2008-05-12 2009-11-12 Andrew Llc Coaxial Impedance Matching Adapter and Method of Manufacture

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2652544A (en) * 1948-12-10 1953-09-15 Sperry Corp Coaxial line connector
DE962715C (de) * 1953-02-21 1957-04-25 Pintsch Electro G M B H Transformationsleitung mit stetig ortsabhaengigem Wellenwiderstand, insbesondere fuer Dezimeterwellen

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1841473A (en) * 1930-01-30 1932-01-19 American Telephone & Telegraph Arrangement for connecting or terminating coaxial conductors
US1932448A (en) * 1931-12-15 1933-10-31 Int Communications Lab Inc Conical adapter for microray transmission lines

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1841473A (en) * 1930-01-30 1932-01-19 American Telephone & Telegraph Arrangement for connecting or terminating coaxial conductors
US1932448A (en) * 1931-12-15 1933-10-31 Int Communications Lab Inc Conical adapter for microray transmission lines

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2859418A (en) * 1955-06-21 1958-11-04 Joseph H Vogelman High power transmission line filters
US2938182A (en) * 1955-11-18 1960-05-24 Raytheon Co Microwave tube output coupling
US4283694A (en) * 1978-07-11 1981-08-11 U.S. Philips Corporation Impedance-matching network realized in microstrip technique
US4853656A (en) * 1987-08-03 1989-08-01 Aerospatiale Societe Nationale Industrielle Device for connecting together two ultra-high frequency structures which are coaxial and of different diameters
US6222500B1 (en) * 1998-05-08 2001-04-24 Telefonaktiebolaget Lm Ericsson (Publ) Device for impedance adaption
US20090278622A1 (en) * 2008-05-12 2009-11-12 Andrew Llc Coaxial Impedance Matching Adapter and Method of Manufacture
US7898357B2 (en) 2008-05-12 2011-03-01 Andrew Llc Coaxial impedance matching adapter and method of manufacture

Also Published As

Publication number Publication date
NL136052B (xx)
GB586619A (en) 1947-03-25
CH268056A (de) 1950-04-30
NL69844C (xx)
FR58156E (fr) 1953-09-29

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