US3176248A - Microwave coaxial termination - Google Patents

Microwave coaxial termination Download PDF

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Publication number
US3176248A
US3176248A US223152A US22315262A US3176248A US 3176248 A US3176248 A US 3176248A US 223152 A US223152 A US 223152A US 22315262 A US22315262 A US 22315262A US 3176248 A US3176248 A US 3176248A
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United States
Prior art keywords
termination
coaxial line
termination portion
microwave
shield
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Expired - Lifetime
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US223152A
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English (en)
Inventor
Vincent J Mchenry
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MA Com Omni Spectra Inc
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Omni Spectra Inc
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Priority to US223152A priority Critical patent/US3176248A/en
Application granted granted Critical
Publication of US3176248A publication Critical patent/US3176248A/en
Priority to BE692057D priority patent/BE692057A/xx
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/24—Terminating devices
    • H01P1/26—Dissipative terminations
    • H01P1/266—Coaxial terminations

Definitions

  • a device terminating an electrical circuit capable ⁇ ot absorbing incident power over the entire microwave spectrum i. e., 1000 megacycles per second to 12,080 megacycles per second, with substantially no reflection of the incident wave'.
  • One application for such a terminating device is where it is desired to determine or measure various characteristics of microwave equipment, ie., as tor a coupling, in which it is necessary for test purposes that there be substantially no reilected energy from a particular propagation path.
  • ports are provided across various stages of the circuits to allow measurements to be made at ⁇ t ese points. Another example of use for the microwave termination would be to terminate these ports. It is an object of this invention to provide a novel microwave termination for substantially absorbing the incident power of electromagnetic waves within the microwave spectrum.
  • One type of microwave termination is of a coaxial construction having a center conductor and an outer shield with a lossy or microwave absorbing materiall disposed between the center conductor and the outer shield.
  • the amount of reflected energy from the microwave termination must be maintained at a minimum, good impedance-matching must be obtained between the termh tion and the line with which itis associated.
  • lt is an object ci this invention to provide a microwave coaxial termination of a rela- ⁇ tively small size for substantially, completely absorbing,
  • terminations of the long taper type, previously mentioned, i-n which the tapered lossy material or load is movable axially relative to the shield and center conductor. By properly adjusting the location of the load along the line, the point of maximum absorption can be found for that given frequency. It is an object of this invention to provide a novel termination for absorbing the incident power of electromagnetic waves within the microwave spectrum in which means are provided for accurately adjusting the termination for maximum absorption of a desired frequency.
  • FIGURE 2 is a side elevational, sectional view, with some parts shown broken away, of a termination of modilied construction, exempliiying the features of this invention.
  • FlG-Ull 3 is a fragmentary, side elevational, sectional view depicting a modification of the termination shown 'n FlGURE l. v
  • a coaxial termination exemplitying the features of this invention, is generally indicated by the numeral lll and has a coaxial conductor I Z having input end portion ld and a coiled, termination end portion
  • the coaxial conductor l2 can be of a conventional construction having a center conductor lll surrounded by an outer electrical conductor or shield l with the conductors fil and i3 separated from each other by an electrical insulator l5.
  • the termination portion "lo is coiled or wound in the form of a helix tapering radially inwardly while extending axially from its input end (connected to input end portion M) to its opposite end.
  • the coiled portion l5 can be thought or" as dell. .g radially inner and outer surfaces.
  • the outside diameter along the radially outer surface of the termination portion lo varies from a maximum at its input end to a min mum at its opposite end.
  • the radially irner surface of the coiled termination portion lr6 would be of a similarly tapered configuration.
  • the radially inner surface of the termination portion ld is cut substantially to a uniform diameter D.
  • the outer shield i3 is provided with an opening which faces radially inwardly, with the opening being a minimum proxima e the input end of the termination portion lo and progressively increasing to a maximum at the opposite end.
  • the terminus of the coaxial coil l2 at the opposite end of the termination portion lo has been reduced to one-half its original cross section; note that, in reducing the cross section of the line l2, both the shield i3 and center conductor ll are nartially removed to provide more effective power dissipation.
  • the cross section is not reduced greater than one-half, since, with less than one-halt of the coaxial line l2 remaining, the mechanical connection maintaining the shield l, insulator l5, and center conductor ll. together would be broken.
  • the total straightened length of the coi ed termination portion lo is approximately equal to twice the wave length oi the lowest frequency of the microwave spectrum to be absorbed, i.e., for a termination to absorb the entire microwave spectrum the straightencd length would be approximately equal to twice the wave length of the i900 megacycle per second wave.
  • the coaxial line l2 is located in a tubular housing ld constructed of metal or plastic and having a generally circular cross section; in tue embodiment of FGURE l the housing ld is made of a material which is a good conductor, i.e., high conductivity, of electricity.
  • the housing i3 is of a substantially uniform diameter in the region ot the termination portion ld tapering at one end to a reduced diameter neck portion l@ which is of a diameter to matably accommodate the terminus of the coaxial line l2 at the input portion ld.
  • An epoxy resin indicated by the numeral Eil, can be applied between the housing and the outside diameter of the terminating portion l5 to thereby secure the coaxial linel?I witln the housing
  • the opposite end of the housing 118 can be sealed by a cap 2.2.
  • intermediate portiony 16 is s ly connected to the cap 22.
  • a threadedjfeniale connector 24 Secured by aretainer ring Z3 to the necked portion 19 of the housingi18 is a threadedjfeniale connector 24.
  • the terminus of the-inputportion 14'of the coaxial line y12 has the centerconductor 11 extending axially outwardly( beyond the' shieldl and .insulationA 15 and is oldered or otherwise electrical- Y 28 vand is accessible through an elongatedwindow or slot 36 located in the extension Yportion 32.
  • the knob Y 34 can be manipulated by hand to cause the'v lossy core matably engageable withA a'suitablefemaleV connectornot ,Y
  • a core of lossy material 26 is locatedin the inside dif' ameter ofthe-terminating portion 16 and canjbe made of pressed carbon, a. ferromagnetic loss material, or some other type oflossyv material well known'in theart.
  • FIGUREJZ depictsamoditication ofthe embodiment of FIGUREy 1 in which components having similar functions are given the samenumbers'with the addition Vof a letter subscript.
  • uInFIGURE 2 Vthe microwave coaxial ter#V mination 10a has a coaxial linelZa havingan'input end portion 14a and a termination portion 16a whichis'heli- ⁇ s cally Wound to form a coil tapering radially inwardly ⁇ which extends axially in aV direction toward the inputend portion: 14a.'Y
  • the insidediameterof the Vtermination portion 16a varies froma minimumat the input end to amaximurn at the opposite end.
  • the outside diameter is Acut to a diameter DaA such,Y that the shield 13a' ispro;
  • the diameter f torwhich the coaxial 'line ⁇ v is wound is not critical, hence allowingrconsiderable variation lin the final physical dimensionrof the termination; e -f y/Next, the internal diameter ofv the'termination portion ofthe-'coil is cut-toa uniform'diameter'D, preferably l whereby the shield VY13 Yat the rirstcoil is just slightly vided with an opening ⁇ which faces radial1y ⁇ outwardly,
  • the shield 13M ⁇ and center conductor-11m have been approximately cut in.” half.
  • the terminating portion Marsan beprovided-with ⁇ abroken While thev crosssection-of the ⁇ last coil is'substantiallyreduced 'to one-half ofitsorigin'al cross section.
  • the-coil is. ⁇ tapered such thatjthe inside diameter vofthe first coil -at the-large eend is just 'slightly less than the uniform diameter D and i the mean diameterI of thelast coil at the small end is center core of epoxy materialfZtia and is providedrwith a Y portion.
  • Y vThe slug and"coaxial line, as'assembled, can
  • the coaxialline 12aY can be mounted in a'housing 18a which is similarrto housing'18. Again, inthe construction shown in FIGURE 2, the-microwave energyV traveling along the coaxial line! 12a is gradually, increas- Vtionsin the ydegree of V"absorption forditerent'frequencies;
  • the t outside diameter is machined to ⁇ a uniform diameter DE, whereby theamount of materialremovcdfrornfthe Y outside'diameteris a minimumy proximate .the input end Tand gradually increases, ⁇ Withthe. last-coil being substanto the shield Aand to ⁇ thepcenter conductor.- Ingorderlto allow theitermination torbesetfor maximum absorption. f
  • a core 2611 of lossy material is slidably dis- ⁇ posed withiny the inside diameter of thetermination 'portion 1Gb and 4has -a rod 2S secured at one .end-thereto. ⁇
  • Apparatus for absorbing incident power of electromagnetic waves within the microwave spectrum comprising a coaxial line having a center conductor surrounded by an outer tubular shield, a termination portion of said coaxial line, said outer shield of said coaxial line of said termination portion being partially removed to define an opening progressively increasing from a minimum proximate an input end of said termination portion to a maximum at an opposite end, and a member of microwave absorbing material disposed proximate to and in .confrontation with said opening.
  • Apparatus for absorbing incident power of electromagnetic Waves within the microwave spectrum comprising a coaxial line having a center conductor surrounded by an outer tubular shield, a termination portion of said coaxial line, said coaxial line of said termination portion decreasing in cross sectional area gradually from one end of said termination portion to an opposite end with said outer shield of said coaxial line of said termination portion having an opening progressively increasing from a minimum proximate said one end of said termination portion to a maximum at said opposite end, an input portion of said coaxial line at said one end of said termination portion, and a member of microwave absorbing material disposed to and in confrontation with said opening,
  • Apparatus for absorbing incident power of electromagnetic waves within the microwave spectrum comprising a coaxial line having a center conductor surrounded by an outer tubular shield, a termination portion of said coaxial line, said coaxial line of said termination portion decreasing in cross sectional area gradually from oney end of said termination portion to an opposite end with said outer shield of said coaxial line of said termination portion having an opening progressively increasing from a minimum proximate said one end of said termination portion to a maximum at said opposite end, an input portion of said coaxial line at said one end of said termination portion, a member of microwave absorbing material disposed to and in confrontation with said opening, and means operatively associated with said member and said termination portion of said coaxial line o for moving said member relative to said termination portion.
  • Apparatus for absorbing incident power of electromagnetic wavcs within the microwave spectrum comprising a coaxial line having a center conductor surrounded by an outer tubular shield, a termination portion of said coaxial line defining a coil having inner and outer surfaces, one of said surfaces of said termination portion of said coaxial line having the material of said coaxial line partially removed with the amount of material removed from said one of said surfaces on adjacent coils gradually increasing from a minimum at one end to a maximum at the opposite end, an input portion of said coaxial line at said one end of said termination portion, and a member of microwave absorbing material disposed in peripheral proximity to said one of said surfaces of said termination portion.
  • Apparatus for absorbing incident power of electromagnetic waves within the microwave spectrum comprising a coaxial line having a center conductor surrounded by an outer tubular shield, a termination portion of said coaxial line defining an axially extending, radially tapering coil having similarly tapering radially inner and outer surfaces, one of said surfaces of said termination portion of said coaxial line having the material of said coaxial line partially removed to a substantially uniform diameter with the amount of material removed from said one of said surfaces on adjacent coils gradually increasing from a minimum at one end to a maximum at the opposite end, an input portion of said coaxial line connected to said one end of said termination portion, and a member of microwave absorbf ing material disposed in peripheral proximity to said one of said surfaces of said termination portion.
  • Apparatus for absorbing incident power of electromagnetic waves within the microwave spectrum comprising a coaxial line having a center conductor surrounded by an outer tubular shield, a termination portion of said coaxial line coiled about an axis with axially adjacent coils defining radially inner and outer surfaces, said coaxial line of said termination portion decreasing in cross sectional area gradually from one end of said termination portion to an opposite end with said outer shield of said coaxial line of said termination portion having an opening facing radially from one of said surfaces with said opening progressively increasing from a minimum proximate said one end of said termination portion to a maximum at said opposite end, an input portion of said coaxial line at said one end of said termination portion, and a member of microwave absorbing material disposed in peripheral proximity to said one of said surfaces of said termination portion.
  • Apparatus for absorbing incident power of electromagnetic waves within the microwave spectrum comprising a generally tubular housing, a coaxial line disposed in said housing and having a center conductor surrounded by an outer tubular shield, a termination portion of said coaxial line coiled about an axis with axially adjacent coils defining radially inner and outer surfaces, said coaxial line of said termination portion decreasing in cross sectional area gradually from one end of said termination portion to an opposite end with said outer shield of said coaxial line of said termination portion having an opening facing radially from one of said surfaces with said opening progressively increasing from a minimum proximate said one end of said termination portion to a maximum at said opposite end, an input portion of said coaxial line at said one end of said termination portion having a terminus coextensive with one end of said housing and with said center conductor extending axially beyond said shield, connector means secured to said one end of said housing and operative with said terminus of said input portion to define an electrical connector, and a member of microwave absorbing material disposed in peripheral proximity
  • Apparatus for absorbing incident power of electromagnetic waves within the microwave spectrum comprising a coaxial line having a center conductor surrounded by an outer tubular shield, a termination portion of said coaxial line coiled about an axis with axially adjacent coils defining radially inner and outer surfaces, one of said surfaces of said termination portion tapered radially between one end and an opposite end, the other of said surfaces of said termination portion extending axially substantially radially uniformly with said outer shield of said coaxial line being partially removed to define an opening facing radially from said other of said surfaces and with said opening progressively increasing from a minimum proximate said one end to a maximum at said opposite end, an input portion of said coaxial line at said one end of said termination portion, and a member of microwave absorbing material disposed in peripheral proximity to said other of said surfaces of said termination portion.
  • Apparatus for absorbing incident power of electromagnetic waves within the microwave spectrum comprising a coaxial line having a center conductor surrounded by an outer tubular shield, a termination portion of said coaxial line coiled about an axis with axially adjacent coils defining radially inner and outer surfaces, one of said surfaces of said termination portion tapered radially between one end and an opposite end, the other of said surfaces of said termination portion extending axially substantially radially uniformly with said outer shield of said coaxial line being partially removed to define an opening facing' radially lfrom said other'of'said-surfaces and with y Y progressively increasingVfr-om aY minimum Vproximate said said opening progressivelyincreasing from Ya minimum proximate saidone-end to.an1aximum atV saidV opposite endsaidopening.
  • a y Y 10 Apparatus for absorbing incident power of electromagnetic waves within the microwave spectrum comprising a coaxial line having a center conductor surrounded l opposite endto a maximurnat said .0ne-end, :an input ypor- ⁇ tion of saidl Y.coaxial line at said opposite end of said termination portion, and a member of microwave absorbing material disposed in peripheral proximity to said outer4 surface of said termination portion.
  • Apparatus for absorbing incident power of electrof magnetic waves withingthe microwave spectrum comprising a generallytubular housing, acoaxial line disposed, in-said housing and having a center conductor surrounded. by an outer tubular-shield, a'termination portion of said coaxial line coiled 'about any axis with axially adjacent by an outer tubular shield, a termination portion of ksaid coaxialY line coiled about an axis with axially adjacent coils defining radially inner and outer surfaces, one of said Surfaces of said terminationfportion: tapered radially between one end and an opposite end,vthe other of saidv surfaces of said termination portion extending axiallysubi stantiallykradially uniformly, said coaxial line ofy said,
  • terminationportion decreasing in cross-sectional area gradually from one endl'oi"A said termination portion toY approximately one-half its original cross sectional area' atan opposite end with said 'outer shield of-y said coaxial line ⁇ being partially removed toy define anropening facing radiallyl kfrom saidother surface and with saidopeningV progressively increasing from a minimum proximate said one endk to a maximumat said opposite end, an input por-.7.
  • c oils defining radially'inner and outer-surfaces, said outer surfacelof said termination portion tapered radially inwardly from one end toward an opposite end, said inner surfaceof ,said termination portion extending axially sub-l stantially radially uniformly with said'outer shield of said coaxial line being partially lremoved to define an opening facing radially inwardly and with said openingprogressively- 's'ivelyincreasing from a minimum proximate. said one en d to a maximum at said opposite end, an input portion of said coaxial line at said one end of'said termination portion, a member of microwave absorbing material disposed. in peripheral proximity to said inner surface of said termination portion,l and means operatively associated with said member, said'housingvand lsaid coaxial line for movj ing said member axially Yrelative to said termination portion.
  • Apparatus for absorbing incident power of'electro-VV magnetic waves within the microwave spectrum comprising a coaxial line having a center conductor surrounded by an outer'tubular shield, a termination portion of said@ .j coaxial line coiled 'about an axis with axially adjacent coils dening radially inner and 'outer surfaces, said outerk Y surface offsaid termination portion tapered radially.
  • said 'innerY surface of said termination portion r extend axially substantially radially uniformly with said outer-:shield ofvsaid coaxial line-being partially removed' to ⁇ define an openingvr facing radially inwardly and with said opening progressively increasing from a minimum'proximate said one endYV r to a maximum at ,saidoppositeend', an input. portion of c said coaxial line at'said oneend of said terminationk por tion, anda member of microwave absorbing material dis-v to saidinner surface of said posedin peripheral proximity termination portion.
  • Apparatus for absorbing incident power of electromagne'tic'waves within the microwavespectrum comprisV ing a coaxial line having a center conductor surroundedby an. outer tubular shield, a termination portion of said" coaxial line coiled" about Van axis with axially adajcent Y coils defining radially inner and outer surfaces, said inner surface of said termination Iportion taperedr radially inwardly from one; end toward an opposite end, said'outer surface of said termination portion extending axially sub'- stantially radially uniformly with said outer shield'ofA said coaxial rline being partially removed' to V-defineV an opening facing radiallyV outwardly andwith said opening openingfacing radially outwardly and with said opening progressively increasing from a'minimum proximate said opposite-end to a maximumy at said one end, an input' 'n portionV of Vsaid coaxial line at said opposite end of said material disposedin peripheral proximity to said outerl termination portion

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3334324A (en) * 1967-08-01 Electrical resistor
US4716389A (en) * 1986-10-20 1987-12-29 Honeywell Inc. Millimeter wave microstrip surface mounted attenuator

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2968775A (en) * 1957-12-20 1961-01-17 Bell Telephone Labor Inc Electromagnetic wave attenuator
US3079552A (en) * 1961-01-24 1963-02-26 Beloit Iron Works Instrument for the measurement of moisture and the like
US3092793A (en) * 1959-09-28 1963-06-04 Bendix Corp Phase shift apparatus adjustable by movement of dielectric slug

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2968775A (en) * 1957-12-20 1961-01-17 Bell Telephone Labor Inc Electromagnetic wave attenuator
US3092793A (en) * 1959-09-28 1963-06-04 Bendix Corp Phase shift apparatus adjustable by movement of dielectric slug
US3079552A (en) * 1961-01-24 1963-02-26 Beloit Iron Works Instrument for the measurement of moisture and the like

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3334324A (en) * 1967-08-01 Electrical resistor
US4716389A (en) * 1986-10-20 1987-12-29 Honeywell Inc. Millimeter wave microstrip surface mounted attenuator

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