US2491662A - Attenuator - Google Patents

Attenuator Download PDF

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Publication number
US2491662A
US2491662A US585707A US58570745A US2491662A US 2491662 A US2491662 A US 2491662A US 585707 A US585707 A US 585707A US 58570745 A US58570745 A US 58570745A US 2491662 A US2491662 A US 2491662A
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United States
Prior art keywords
attenuation
vane
attenuator
vanes
frequency
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US585707A
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English (en)
Inventor
Edward W Houghton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL71522D priority Critical patent/NL71522C/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US585707A priority patent/US2491662A/en
Priority to GB9663/46A priority patent/GB617092A/en
Priority to FR54938D priority patent/FR54938E/fr
Application granted granted Critical
Publication of US2491662A publication Critical patent/US2491662A/en
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
    • H01P1/22—Attenuating devices
    • H01P1/222—Waveguide attenuators

Definitions

  • This invention relates to attenuators and more particularly to those for use with wave guides.
  • the principal object of the invention is to minimize the change in the attenuation of a wave guide attenuator caused by varying the frequency over a selected range.
  • Another object is to make the attenuation of a variable wave guide attenuator a linear function of the angular rotation of a control shaft while maintaining the condition of minimum attenuation variation with frequency.
  • a wave guide attenuator may comprise one or more resistive vanes positioned longitudinally within the guide.
  • the attenuation introduced by such an attenuator depends, for one thing, upon the intensity of the electric field at the location of the vane. Therefore, in order to vary the attenuation the vane may be moved from a position of one intensity to a position of greater or less intensity.
  • two vanes may be positioned opposite each other and means provided for moving them from the side of the guide toward each other to the center.
  • the vanes are symmetrically positioned and moved at the same rate, the attenuation at any particular setting may not be sufficiently constant with frequency.
  • the change in attenuation with frequency is very much reduced by positioning the vanes unsymmetrically and moving them at different rates so chosen that, for any setting, the attenuation has a minimum variation with frequency over a selected range.
  • the positions of the two vanes may, for example, be controlled by two cams on a single shaft.
  • the cams may be so shaped that the attenuation varies linearly with the angular rotation of the shaft.
  • Fig. l is a perspective view, partly cut away, of a variable double-vane wave guide attenuator in accordance with the invention.
  • Fig. 2 is a plan view of the cams used in the attenuator
  • Fig. 3 is a horizontal sectional view of a portion of the attenuator showing the vanes in their extreme positions;
  • Fig. 4 gives the attenuation-frequency characteristics over a selected range for a fixed main vane insertion and different compensating vane insertions
  • Fig. 5 shows the insertion of the vanes and the attenuation of the attenuator, both plotted against the angular rotation of the cams.
  • the attenuator comprises a section of wave guide I of rectangular cross section within which are two resistive elements 2 and 3 in the form of vanes having ends which are tapered to reduce reflection.
  • the vanes 2 and 3 are positioned longitudinally opposite each other in the guide I with their major planes parallel to a side 4 of the guide I having the shorter transverse dimension.
  • Each of the vanes 2 and 3 is attached to the ends of two rods 6 by the screws I.
  • the rods 6 pass through the side 4 of the guide I through holes 8 which are large enough in diameter to clear the rods 6 all around.
  • Collars 9 attached to the sides 4 on the outside surround the rods 6 and help to prevent the escape of energy.
  • each pair of rods 6 associated with one of the vanes 2 or 3 are clamped in the slots H at the ends of a yoke l2 by means of the clamping screws l3.
  • Each yoke 12 is attached by means of the screws I! to a guide bar l8 which slides in a transverse groove formed on the upper side of the wave guide I by the cross members l9 and covered by the plate 2%.
  • the guide bar I8 is forced toward the bottom of the groove by an arcuate spring 20 which is inserted between the plate 2
  • Each guide bar [8 has an arm 22 the end of which is held against the edge of one of the cams 23 or 24 by a helical spring 25.
  • the cams 23 and 24 are aflixed to a rotatable shaft 25 which carries a dial 21 graduated in decibels of attenuation.
  • the dial 2'! may be read at a slot 28 in the arm 29.
  • FIG. 2 A typical lay out for the cams 23 and $24 is shown in Fig. 2.
  • they are so designed that, for any setting of the dial 21, the change in attenuation with frequency over a selected range will be a minimum.
  • this requires that the vanes 2 and 3 have difierent insertions. That is, the distance d3 between the side 4 of the wave guide I and the vane 3 will diiier from the distance 112 between the op posite side and the vane 2.
  • Fig. 3 shows, in full line, the positions of the vanes 2 and 3 at maximum insertion and, in broken line, their positions at minimum insertion.
  • the curves of Fig. 4 show, for example, typical attenuation-frequency characteristics for a main vane insertion d2 of 200 mils and various compensating vane insertions (is over a selected rangeof 8.5 to 9.6 kilomegacycles. It is seen that curve A, corresponding to da equal to 160 mils, has the least change in attenuation over the range. For this insertion the attenuation has approximately the same value at the lowest frequency of 8.5 and at the highest frequency of 9.6 and is a maximum at approximately the geometric mean frequency of 9.03 kilomegacycles. These criteria are useful in determining if the optimum insertion (is for the compensating vane 53 has been found.
  • the attenuation is not a linear function of the insertion d2 of the main vane 2.
  • the earns 23 and 24 may be so designed that the attenuation varies linearly with the angle of rotation of the shaft 26. are shown in Fig. 5. If, for example, the attenuation is to vary from a minimum of zero to a maximum of 40 decibels over an angular rotation from to 330 degrees, the attenuation, read on the right-hand scale, is plotted as a straight line F against cam rotation as ahscissas. Next, the insertion (12 for the main vane 2 is plotted against the nominal attenuation, for the different insertion steps, to give curve G.
  • the nominal attenuation may be taken as that at the geometric mean frequency. Then the corresponding insertion (is for the compensating vane 59 is plotted to give the curve H. Data for the layout of the cams 23 and 24 may be read from the curves G and H, and for the calibration of the dial 2? from the curve F. At the Ill-degree point on the cams the vanes 2 and 3 will be held against the sides of the wave guide I. To get an insertion of 200 mils for the vane 2, for example, will require a decrease of 200 mils in the distance from the edge to the center of the cam 24.
  • electromagnetic waves are impressed upon one end of the attenuator and a suitable load device is connected to the other end.
  • the waves may, for example, be of the transverse electric type, with the electric lines of force parallel to the side i of the wave guide 5.
  • the attenuation introduced is determined by the position of the vanes 2 and 3,,under the control of the The required curves 1 shaft 25 and the cams 23 and M, and may be a read on the dial 21.
  • the vanes 2 and 3 are positioned for maximum constancy of attenuation, as .the frequency is varied over the selected range. Furthermore, the
  • the equal insertion double-vane attenuator is superior to the single-vane type because the added vane couples, by mutual inductance, a compensating reactance in series with the intrinsic self-reactance of each vane, thus reducing the net series reactance in the vane and thereby reducing frequency sensitivity of the attenuation by making each vane act more like a true shunt resistance across the wave guide.
  • the intrinsic self-reactance of each vane probably varies with its insertion into the guide and, in order to compensate it exactly by mutual coupling from another vane, this coupling must be varied in a definite way as the main vane insertion increases.
  • this coupling is properly controlled by providing the required compensating vane insertion d3 for each insertion dz of the main vane 2.
  • the non-equal insertion double-vane attenuator may be regarded as a compensatedsingle-vane attenuator where the iunctionof the main vane 2 is to increase the attenuation by a continuous increase in its insertion d2, as shown by curve G of Fig. 5, while the action of the compensating vane 3 is that of a tuning adjustment which couples in the proper amount of cancelling reactance at each position of the Vans 2 As may be seen from curve H of Fig.
  • the compensating vane 3 has a rate of insertion only slightly lower than that of the main vane 2.
  • the insertion d3 of the vane 3 reaches a maximum value, in the vicinity of the point 3
  • th insertion d3 of the vane 3 remains substantially constant.
  • a variable attenuator to cover the limited range between the points 32 and 33 may, therefore, have a main vane 2 which is continuously inserted and a fixed compensating vane 3 with its insertion d3 equal to the mean value for the range.
  • Such an attenuator is simpler in construction since one cam 23, one of the guide bars it, one of the yokes l2, and other associated parts may be eliminated.
  • An attenuator comprising a section of Wave guide having unequal cross-sectional dimensions and adapted to transmit a transverse electric wave with its electric vector parallel to the shorter of said dimensions and two thin, fiat resistive elements longitudinally positioned within said section, said elements being opposite each other, parallel to said shorter dimension and at different distances from the respective sides of said section and said distances being so related that the attenuation has a minimum variation over a selected range of frequencies.
  • An attenuator comprising a section of wave guide of rectangular cross section and two resistive vanes positioned Within said section beside each other, parallel to opposite sides thereof, and at different distances therefrom so related that 5 the attenuation has a minimum variation over a selected range of frequencies.
  • An attenuator in accordance with claim 2 which includes means for moving said vanes laterally to vary the attenuation over a range while maintaining the condition of minimum attenuation variation with frequency.
  • An attenuator in accordance with claim 2 which includes unitary control means for moving said vanes laterally to vary the attenuation over a range while maintaining the condition of minimum attenuation variation with frequency.
  • An attenuator in accordance with claim 2 which includes means comprising a rotatable control shaft for moving said vanes laterally to vary the attenuation over a range While maintaining the condition of minimum attenuation variation with frequency, said attenuation being a linear function of the angular rotation of said shaft.
  • An attenuator in accordance with claim 2 which includes means comprising a rotatable control shaft and two cams for moving said vanes laterally to vary the attenuation over a range, said cams being shaped to make the attenuation a linear function of the angular rotation of said shaft while maintaining the condition of minimum attenuation variation with frequency.
  • An attenuator in accordance with claim 2 which includes unitary control means for moving said vanes laterally to vary the attenuation over a range while maintaining the condition of minimum attenuation variation with frequency, one of said vanes moving in one direction only throughout said range and the other of said vanes moving in opposite directions in different parts of said range.
  • An attenuator in accordance with claim 2 which includes means for moving one of said vanes laterally to vary the attenuation over a range, the other of said vanes having a fixed position such that the condition of minimum attenuation variation with frequency is substantially maintained throughout said attenuation range.

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  • Attenuators (AREA)
  • Non-Reversible Transmitting Devices (AREA)
US585707A 1945-03-30 1945-03-30 Attenuator Expired - Lifetime US2491662A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL71522D NL71522C (en)van) 1945-03-30
US585707A US2491662A (en) 1945-03-30 1945-03-30 Attenuator
GB9663/46A GB617092A (en) 1945-03-30 1946-03-28 Improvements in attenuators for use with wave guides
FR54938D FR54938E (fr) 1945-03-30 1946-08-27 Atténuateurs d'ondes électromagnétiques

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US585707A US2491662A (en) 1945-03-30 1945-03-30 Attenuator

Publications (1)

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US2491662A true US2491662A (en) 1949-12-20

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US585707A Expired - Lifetime US2491662A (en) 1945-03-30 1945-03-30 Attenuator

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US (1) US2491662A (en)van)
FR (1) FR54938E (en)van)
GB (1) GB617092A (en)van)
NL (1) NL71522C (en)van)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2682641A (en) * 1949-05-28 1954-06-29 Sperry Corp Selective mode attenuator for wave guides
US2683255A (en) * 1950-05-16 1954-07-06 Bell Telephone Labor Inc Switch attenuator for wave guides
US2684469A (en) * 1949-06-23 1954-07-20 Sperry Corp Mode selective attenuator
US2724112A (en) * 1950-03-03 1955-11-15 Collins Radio Co Energy absorber
US2741745A (en) * 1952-08-14 1956-04-10 Philco Corp Adjustable waveguide elements
US2745069A (en) * 1950-05-17 1956-05-08 Bell Telephone Labor Inc Microwave magnetized ferrite attenuator
DE949070C (de) * 1954-08-27 1956-09-13 Lorenz C Ag Anzeigemechanik eines variablen Hohlleiter-Daempfungsgliedes
US2796588A (en) * 1946-02-01 1957-06-18 Richard M Walker Compact waveguide attenuator
US2913683A (en) * 1954-12-20 1959-11-17 Aladdin Ind Inc Ultrahigh frequency tuner
US2923899A (en) * 1960-02-02 Ferrite
US3175172A (en) * 1960-07-26 1965-03-23 Wandel & Goltermann Low reflection energy absorbers for waveguides
US3209288A (en) * 1963-09-23 1965-09-28 North American Aviation Inc Attenuator with constant phase shift effected by the compensatory insertion and removal of dielectric material

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2180950A (en) * 1935-10-05 1939-11-21 Bell Telephone Labor Inc Guided wave transmission
US2197123A (en) * 1937-06-18 1940-04-16 Bell Telephone Labor Inc Guided wave transmission
US2207845A (en) * 1938-05-28 1940-07-16 Rca Corp Propagation of waves in a wave guide
US2425345A (en) * 1942-12-23 1947-08-12 Bell Telephone Labor Inc Microwave transmission system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2180950A (en) * 1935-10-05 1939-11-21 Bell Telephone Labor Inc Guided wave transmission
US2197123A (en) * 1937-06-18 1940-04-16 Bell Telephone Labor Inc Guided wave transmission
US2207845A (en) * 1938-05-28 1940-07-16 Rca Corp Propagation of waves in a wave guide
US2425345A (en) * 1942-12-23 1947-08-12 Bell Telephone Labor Inc Microwave transmission system

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2923899A (en) * 1960-02-02 Ferrite
US2796588A (en) * 1946-02-01 1957-06-18 Richard M Walker Compact waveguide attenuator
US2682641A (en) * 1949-05-28 1954-06-29 Sperry Corp Selective mode attenuator for wave guides
US2684469A (en) * 1949-06-23 1954-07-20 Sperry Corp Mode selective attenuator
US2724112A (en) * 1950-03-03 1955-11-15 Collins Radio Co Energy absorber
US2683255A (en) * 1950-05-16 1954-07-06 Bell Telephone Labor Inc Switch attenuator for wave guides
US2745069A (en) * 1950-05-17 1956-05-08 Bell Telephone Labor Inc Microwave magnetized ferrite attenuator
US2741745A (en) * 1952-08-14 1956-04-10 Philco Corp Adjustable waveguide elements
DE949070C (de) * 1954-08-27 1956-09-13 Lorenz C Ag Anzeigemechanik eines variablen Hohlleiter-Daempfungsgliedes
US2913683A (en) * 1954-12-20 1959-11-17 Aladdin Ind Inc Ultrahigh frequency tuner
US3175172A (en) * 1960-07-26 1965-03-23 Wandel & Goltermann Low reflection energy absorbers for waveguides
US3209288A (en) * 1963-09-23 1965-09-28 North American Aviation Inc Attenuator with constant phase shift effected by the compensatory insertion and removal of dielectric material

Also Published As

Publication number Publication date
FR54938E (fr) 1951-04-30
GB617092A (en) 1949-02-01
NL71522C (en)van)

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