US3581311A - Linearly polarized microwave feed assembly for parabolic antennas and the like - Google Patents

Linearly polarized microwave feed assembly for parabolic antennas and the like Download PDF

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Publication number
US3581311A
US3581311A US780052A US3581311DA US3581311A US 3581311 A US3581311 A US 3581311A US 780052 A US780052 A US 780052A US 3581311D A US3581311D A US 3581311DA US 3581311 A US3581311 A US 3581311A
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United States
Prior art keywords
feeder line
line
wave
slots
segments
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Expired - Lifetime
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US780052A
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English (en)
Inventor
Alfred Kach
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Patelhold Patenverwertungs and Elektro-Holding AG
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Patelhold Patenverwertungs and Elektro-Holding AG
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/08—Radiating ends of two-conductor microwave transmission lines, e.g. of coaxial lines, of microstrip lines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
    • H01Q19/12—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces wherein the surfaces are concave
    • H01Q19/13—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces wherein the surfaces are concave the primary radiating source being a single radiating element, e.g. a dipole, a slot, a waveguide termination

Definitions

  • the present invention relates to a microwave feed assembly for parabolic antennas and the like designed for energization by a coaxial feeder line and radiation of linearly polarized electromagnetic waves.
  • dipole antennae are chiefly used as primary radiators for the illumination of parabolic reflectors, among other things on account of the low gain factor and slight directional effect of the dipole radiator.
  • a dipole stub is fitted to each of the segments thus formed of the outer conductor.
  • the conductor is connected to the respective segment through a short-circuiting stub at right angles to and disposed at a point of the conductor coincident with .the bisecting plane of the slots.
  • a splash or reflector disc arranged on the side of the slots remote from the input side of the line insures that the parabolic reflector is optimally illuminated by the dipole radiator.
  • a symmetrical coupling for the dipole stubs is provided by the effect of the half-wave (M2) resonance of the two conductor segments.
  • Such an antenna with pronounced dipole stubs is especially suitable for frequencies in the region of 1-4 gc. (gigacycles), corresponding to a wave length range 30-7 cm. At higher frequencies, or for still shorter wave lengths, for example 6-8 gc. or about -3 cm., respectively, the dipole stubs become so small that, regard being had to the dimension of the feeder line, it is practically no longer possible to comply with the existing geometrical and space requirements for the antenna to function satisfactorily.
  • the use of dipole stubs has heretofore been one of the most simple means for the illumination of a parabolic reflector with linearly polarized electromagnetic radiation.
  • An important object of the present invention is, therefore, the provision of an improved dipole antenna of the referred to type which is especially, though not limitatively, suitable as a primary radiator for the illumination of a parabolic reflector with linearly polarized waves by way of a coaxial feeder line, without requiring any pronounced dipole stubs, which anten na exhibits good radiation and matching properties over a relatively wide frequency range and in spite of its relatively large dimensions compared with the operating wave length; and which is both simple in design and suitable for structural embodiment with a parabolic reflector.
  • FIG. 1 is a longitudinal sectional view of a microwave feed assembly for parabolic antennas for the radiation of linearly polarized waves and embodying the invention
  • FIG. 2 is a sectional view taken on line 2-2 of FIG. I;
  • FIG. 3a and 311 show substitute electrical circuits explanatory of the function and operation of the invention.
  • FIGS. 4a4c further illustrate the formation of a linearly polarized radiation field in accordance with the principles of the invention.
  • the dipole antenna according to the invention is characterized generally by the connection of the inner conductor of a slotted coaxial feeder line to one of the segments of the outer conductor of said line by way of an inductive link or coupling impedance, on the one hand, and by the connection of the inner conductor of the line to the other segment by way of capacitive link or coupling impedance, respectively, the effective impedance values of these couplings being substantially equal and opposite at a mean operating frequency or wave length (A0) in the coupling plane which bisects the slots in the outer conductor of the line.
  • the invention involves the provision of a further hollow outer conductor or concentric sleeve surrounding the coaxial feeder line at least over the region of its longitudinal slots, whereby to provide a second line having an inner conductor formed by the outer conductor of the first line.
  • a TB wave is excited in the second line by a TEM wave propagated in the first line energized by a suitable source of microwave energy.
  • This TE wave exhibiting a substantial cross-field as a result of the geometry of the concentric conductors is converted into a substantially linearly polarized field suitable for radiation by av TEM wave being directly coupled into the second line through the slots in the outer conductor of the first line, the width of the slots being such as to provide a TEM field in the second line substantially cancelling, at or near the radiation aperture of the line, the cross-field component of the TE wave being radiated, in a manner as will become further apparent from the description of the construction and function of the invention in reference to the drawing.
  • FIGS. 1 and 2 show a dipole antenna and parabolic reflector in longitudinal and transverse section, respectively.
  • a coaxial feeder line 2 energized by a suitable microwave generator (not shown)
  • two diametrically opposite longitudinal slots 3 and 4 having a length equal to half the mean operating wave length (ho/2) and subdividing the outer conductor 5 of the line into two opposite segments 6 and 7, respectively.
  • the inner conductor 8 of the line is linked or coupled via a shorting stub 9 to the segment 6 at a point coincident with the cross-sectional plane x-x which bisects the slots 3 and 4 and which will hereafter be referred to as the coupling plane of the line.
  • a short-circuiting disc 10 terminating the end portion 1 of the line 2 at a distance of five-eighthsseven-eighths of the slot length (five-sixteenthsseven-sixteenths of k0) from the coupling plane X-x, constitutes a composite structural part together with the inner conductor 8 and the shorting stub 9. Additional coupling elements in the form of stubs or screws 11 and 12 are fitted in the segments 6 and 7, respectively. The screw 11 moreover serves to fasten the stub 9 to the segment 6.
  • An outer cylindrical conductor or sleeve 13 is secured, via a thread 14, to the outer conductor 5 of the line 2 and forms, together with said conductor a further coaxial line or feeder of annular cross section which is terminated at one end, that is, adjacent to the outer ends I5 of the slots in the example illustrated, by the base 16 of the sleeve acting as a short-circuiting disc.
  • the opposite end of the sleeve 13 is extended by an insulating tube 17 terminating in a conical end piece 17'.
  • Line 2 may be fitted with a suitable impedance matching means located ahead of the input-feed ends 19 of the slots 3 and 4 and consisting, in the example shown of a step or shoulder 19' on the inside of the outer conductor 5 and Ito/4 line section between said shoulder and the ends 19 of slots 3 and 4.
  • a suitable impedance matching means located ahead of the input-feed ends 19 of the slots 3 and 4 and consisting, in the example shown of a step or shoulder 19' on the inside of the outer conductor 5 and Ito/4 line section between said shoulder and the ends 19 of slots 3 and 4.
  • FIG. 3a shows an equivalent electric circuit diagram of the feeder radiator according to FIGS. 1 and 2. It is assumed that the coaxial feeder line 2 up to and including the AD/4 line sections has an internal resistance R
  • the segments 6 and 7 of the outer conductor may then be considered as a two-wire transmission line 20 short-circuited at a distance of half a wave length from the input-feed plane and having its individual conductors connected to the inner conductor of the line at the coupling plane x-x, or at a point one-quarter wave length from the input-feed plane, via a coupling inductor L and a coupling capacitor C, respectively.
  • the inductance L and capacitance C are so chosen that their impedance values are substantially equal and opposite at the mean operating frequency of wave length (AOL-whereby to provide a symmetrical coupling of the feeder line 2 with the antenna load or radiation resistance R,.
  • the coupling inductance L and coupling capacitance C take the form, respectively, of the shorting stub and a trimmer screw 12 protruding into the coaxial feeder and adjusted to provide equal and opposite inductive and capacitive coupling .reactances between the inner conductor 8 and segments 6 and 7 of the line 2.
  • the end portion 1 of the line 2 being terminated by the short-circuiting disc at a distance of fiveeights-seven-eigh ths of the slot length, or five-sixteenthsseven-sixteenths of the operating wave length, from the coupling plane x-x, is represented by an equivalent two-wire line 21 being short-circuited at its end in the manner shown.
  • the stub 9 which connects the inner conductor 8 to the segment 6 is represented in the equivalent circuit by the inductor L.
  • the end portion 1 of the feeder line 2 being terminated at the stated distance from the coupling plane x-x provides a capacitive coupling for the segment 7 corresponding to the capacity C according to FIG. 30, on the one hand, while additionally acting to transform the inductance L of the stub 9 up to approximately twice of the inductance L according to FIG. 3a, on the other hand.
  • the arrangement as shown in FIG. 1 provides a doubling of the effective coupling inductance compared with the previously mentioned variant of a capacitive coupling by means of a trimmer stub or screw 12, thus providing a four times impedance transformation for matching the feeder line to the load resistance R of the antenna.
  • the cross section of the stub 9 may be made large enough, even at very high operating frequencies, to impart good mechanical stability to the arrangement when using impedance-transformation ratios as required in practice.
  • the length of the sleeve 13 is so chosen that the distance of its open end or radiating aperture from the coupling plane x-x is at least substantially equal to half the operating wave length of the TE, wave.
  • Optimal compensation of the cross-components of the TE field may thus be achieved at or near the radiating aperture or open end of the outer line or wave guide.
  • the strength of the field of the TEM wave can moreover be so adapted, such as by varying the width of the coupling slots 3 and 4, that the crossfield components of the TE wave are substantially completely compensated at the open end or radiating aperture of the antenna.
  • FIG. 4c The resultant field of the TE wave with its distortion removed in this manner at the open end or radiating aperture of the outer line is shown in FIG. 4c, illustrating the attainment of substantially symmetrical linearly polarized waves radiated from the open end of the outer line and in turn by the antenna 22.
  • the insulating tube 17 which extends the outer line from its open end serves to partially delay the radiated waves, whereby as the electromagnetic field emerges from the open end of the insulating tube, the electric field lines extend at least in part tangentially to the conical surface of the end piece 17.
  • the insulating tube 17 When the antenna is used as a rear feed radiator of a parabolic reflector, as shown at 22, FIG. 1, the insulating tube 17 imparts increased divergence to the radiated waves, resulting thereby in a more uniform illumination of the parabolic reflector.
  • the optimum cone angle depends on the irradiation angle which it is required to attain. Good results have been achieved with a cone angle of 30 for most practical purposes.
  • the insulating tube 17 furthermore acts at least partly as a transformation means between the wave-resistance of free space and the radiation resistance (R of the line 5, l3, and also protects the antenna from the effects of atmospheric infl uence.
  • the screws 11 and 12 furthermore serve as coupling stubs for the purpose of matching the line 2 to the symmetrizing transformer formed by the means for the symmetrical coupling of the segments 6 and 7 to the inner conductor 8 of line 2.
  • a linearly polarized microwave feed assembly for parabolic antennas and the like comprising in combination:
  • I a first coaxial feeder line having an inner conductor and an outer conductor
  • said outer conductor being provided with a pair of opposed longitudinal slots located adjacent to the output end of said feeder line and having a length approximately equal to one-half the operating wave length, to provide a pair of intervening segments of said outer conductor between said slots,
  • said inductive and capacitive coupling means offering substantially equal and opposite impedances, to excite a symmetrical TE wave in said second feeder line by a TEM wave propagated through said first feeder line, and
  • said inductive coupling means consists of a short-circuiting stub coincident with said bisecting plane and connecting said inner conductor to one of said segments, and wherein said capacitive coupling means consists of an adjustable coupling stub mounted in the other of said segments coincident with said plane.
  • said inductive coupling means consists of a short-circuiting stub disposed within said bisecting plane and connecting said inner conductor to one of said segments, and wherein said capacitive coupling means consists in the short-circuited end of said first line having a spacing distance from said plane equal to five-sixteenthsseven-sixtecnths of the operating wave length.

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  • Waveguide Aerials (AREA)
  • Aerials With Secondary Devices (AREA)
US780052A 1967-12-01 1968-11-29 Linearly polarized microwave feed assembly for parabolic antennas and the like Expired - Lifetime US3581311A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1692167A CH466383A (de) 1967-12-01 1967-12-01 Antenne für linear polarisierte Wellen

Publications (1)

Publication Number Publication Date
US3581311A true US3581311A (en) 1971-05-25

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Family Applications (1)

Application Number Title Priority Date Filing Date
US780052A Expired - Lifetime US3581311A (en) 1967-12-01 1968-11-29 Linearly polarized microwave feed assembly for parabolic antennas and the like

Country Status (8)

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US (1) US3581311A (xx)
AT (1) AT281923B (xx)
CH (1) CH466383A (xx)
DE (2) DE1616300C2 (xx)
FR (1) FR1597774A (xx)
GB (1) GB1238200A (xx)
NL (1) NL6817091A (xx)
SE (1) SE356640B (xx)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4197549A (en) * 1977-08-17 1980-04-08 Harris Corporation Slot antenna
US4443804A (en) * 1981-09-28 1984-04-17 Ford Aerospace & Communications Corporation Modified difference mode coaxial antenna with flared aperture
US4811031A (en) * 1986-05-02 1989-03-07 Borg-Warner Chemicals Europe Bv DBS antenna
US4872211A (en) * 1988-08-10 1989-10-03 The United States Of America As Represented By The Secretary Of The Navy Dual frequency launcher for circularly polarized antenna
US4907008A (en) * 1988-04-01 1990-03-06 Andrew Corporation Antenna for transmitting circularly polarized television signals
US5086303A (en) * 1988-02-19 1992-02-04 The Agency Of Industrial Science And Technology Primary feed with central conductor defining a discharge path
US6819297B2 (en) * 2002-07-10 2004-11-16 University Of Kansas Wideband planar antenna
US20110062965A1 (en) * 2009-09-14 2011-03-17 Airbus Operations Gmbh Device for the measurement of coating thicknesses by means of microwaves

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3049532A1 (de) * 1980-12-31 1982-07-29 Aeg-Telefunken Ag, 1000 Berlin Und 6000 Frankfurt Selbsttragender primaererreger fuer spiegelantennen
EP0105677B1 (en) * 1982-09-27 1986-12-10 Kureha Kagaku Kogyo Kabushiki Kaisha Endotract antenna device for hyperthermia
EP0304722B1 (de) * 1987-08-12 1992-10-28 Siemens Aktiengesellschaft Richtfunkantenne
US5938692A (en) * 1996-03-26 1999-08-17 Urologix, Inc. Voltage controlled variable tuning antenna
US5861021A (en) * 1996-06-17 1999-01-19 Urologix Inc Microwave thermal therapy of cardiac tissue

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2954556A (en) * 1956-10-10 1960-09-27 Andrew Corp Cross polarized dual feed

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2465245A (en) * 1945-03-03 1949-03-22 Westinghouse Electric Corp Terminus for concentric transmission lines
US2694778A (en) * 1953-05-29 1954-11-16 Howard J Rowland Antenna
GB825532A (en) * 1955-09-03 1959-12-16 Mini Of Supply Improvements in or relating to radiating waveguide feeders for radio-frequency electromagnetic waves

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2954556A (en) * 1956-10-10 1960-09-27 Andrew Corp Cross polarized dual feed

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4197549A (en) * 1977-08-17 1980-04-08 Harris Corporation Slot antenna
US4443804A (en) * 1981-09-28 1984-04-17 Ford Aerospace & Communications Corporation Modified difference mode coaxial antenna with flared aperture
US4811031A (en) * 1986-05-02 1989-03-07 Borg-Warner Chemicals Europe Bv DBS antenna
US5086303A (en) * 1988-02-19 1992-02-04 The Agency Of Industrial Science And Technology Primary feed with central conductor defining a discharge path
US4907008A (en) * 1988-04-01 1990-03-06 Andrew Corporation Antenna for transmitting circularly polarized television signals
US4872211A (en) * 1988-08-10 1989-10-03 The United States Of America As Represented By The Secretary Of The Navy Dual frequency launcher for circularly polarized antenna
US6819297B2 (en) * 2002-07-10 2004-11-16 University Of Kansas Wideband planar antenna
US20110062965A1 (en) * 2009-09-14 2011-03-17 Airbus Operations Gmbh Device for the measurement of coating thicknesses by means of microwaves
US8866496B2 (en) 2009-09-14 2014-10-21 Airbus Operations Gmbh Device for the measurement of coating thicknesses by means of microwaves

Also Published As

Publication number Publication date
CH466383A (de) 1968-12-15
AT281923B (de) 1970-06-10
NL6817091A (xx) 1969-06-03
SE356640B (xx) 1973-05-28
GB1238200A (xx) 1971-07-07
DE1616300A1 (de) 1971-04-01
FR1597774A (xx) 1970-06-29
DE6608680U (de) 1971-10-07
DE1616300C2 (de) 1984-02-02

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