US2883631A - High frequency transmitting windows - Google Patents

High frequency transmitting windows Download PDF

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Publication number
US2883631A
US2883631A US522988A US52298855A US2883631A US 2883631 A US2883631 A US 2883631A US 522988 A US522988 A US 522988A US 52298855 A US52298855 A US 52298855A US 2883631 A US2883631 A US 2883631A
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US
United States
Prior art keywords
window
waveguide
high frequency
axis
frequency power
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Expired - Lifetime
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US522988A
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English (en)
Inventor
Blackadder Robert Lennox Scott
Vaughan James Rodney Mitchell
Young Peter
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EMI Ltd
Electrical and Musical Industries Ltd
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EMI Ltd
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Application filed by EMI Ltd filed Critical EMI Ltd
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Publication of US2883631A publication Critical patent/US2883631A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/08—Dielectric windows

Definitions

  • This invention relates to devices having windows for transmitting high frequency electromagnetic power such as are required for sealing an evacuated device whilst at the same time permit-ting the transmission of high frefinding a satisfactory glass which can withstand the heat which is generated during transmission of high degrees of Moreover, if refractory materials capable of employed for such windows then it is also found that these windows give rise to reflections which it is found not only causes the oscillations generated in the klystron or magnetron to change their mode of oscillation but also alfects the resonant frequency of the generated oscillations.
  • the object of the present invention is to provide an improved device having a window which is capable of withstanding such high powers whilst at the same time reducing radio frequency reflections which might arise.
  • a device for transmitting high frequency electromagnetic power of refractory material capable of transmitting high frequency power and having a single optic axis, said window being sealed to an apertured support, said optic axis being so orientated and the arrangement being such that radio frequency reflections which arise in said window and at the edge of the aperture in said support are substantially mutually cancelling.
  • the window is preferably made of sapphire and is sealed between a pair of apertured diaphragms and the optic axis of said window is arranged to be parallel to the axis along which power is transmitted through said window.
  • the window is sealed to a single diaphragm and in this-case the optic axis to be oblique to the axisalong through the window.
  • Figure 2 is a similar view of a device in accordance with another embodiment of the invention.
  • the reference numeral 1 illustrates a section of waveguidewhich may be connected to the resonant cavity of an electron discharge valve such as a kly'stron or magnetron and is proof the window is arranged which power is transmitted vided with a window indicated at 2 which as shown is positioned in a plane normal to the axis of the waveguide l and which serves to seal the end of the waveguide 1 in a vacuum tight manner.
  • the window 2 is made of crystalline refractory material having a single optic axis and which is capable of transmitting high frequency power.
  • Optic axis is defined by Jenkins and White in Funda mentals of Optics (McGraw-Hill Publishing Co.) as be ing the one and only one direction through a crystal in which ordinary and extraordinary raysbehave alike in all respects.
  • the optic axis of the window is so orientated in relation to the axis of the waveguide 1, i.e. the axis along which high frequency power is transmitted through the waveguide, that reflections which arise in said window and at the edges of a support for said window are substantially mutually cancelling.
  • the window 2 is preferably made in the form of a disc of artificial sapphire (crystalline alumina), the disc being so formed for the embodiment shown in Figure 1 that the optic axis thereof is normal to the plane of said disc.
  • the disc is mounted so as to close an aperture in a support, which in the embodiment shown in Figure 1 comprises a pair of apertured diaphragms 3 and 4 between which the disc is sealed, the rims 5 and 6 of the latter being .in turn sealed as by welding to the end of the waveguide 1.
  • the diaphragms 3 and 4 are made of a material having a coefficient of expansion lying in the range 5.7 to 5.9x 10- such as a nickel-cobalt-iron alloy for example a material known by the registered trademarks Kovar or Nicosel.
  • the two diaphragms 3 and 4 and the window 2 are sealed together by applying a powdered glass, having a coefficicnt of expansion of about 5.7 x 10- such as a glass having a composition of about 67% SiO 21% B 0 4 /2% K 0, 4% A1 0 and 3% Na o such as one known by the registered trademark Kodial around the edge of the disc 2 as indicated at 7 and to the adjacent metal surfaces of the diaphragms 3 and 4 and heating'the assembly to about 900 C. to fuse the powdered glass.
  • the diaphragm 3 is, as shown, spaced from the end of the waveguide 1 which is of the usual rectangular crosssection.
  • the body 8 in which the waveguide 1 is formed is of circular cross-section and the end wall is provided with the usual annular high frequency choke 9, whilst the opposite longer walls of the waveguide 1 at their mid positions are provided with chamfered portions 10 .of known form in order to reduce the danger of sparking between the end of the waveguide and the window 2.
  • chamfered portions 10 of known form in order to reduce the danger of sparking between the end of the waveguide and the window 2.
  • the expansion of the sapphire disc in the plane of the disc is 5.7 1() per degree centigrade which matches the material known by the registered trademark Kovar sufficiently well for a sound hermetic seal to be produced.
  • the expansion along the optic axis 15 of the sapphire disc is 6.4 10- which would cause a mismatch if it were in or near the plane of the disc.
  • the cross-sectional dimensions of the waveguide 1 are 0.280 inch 0.l40 inch; the thickness of the window 2 is 0.0055 inch with a dielectric constant of 9.4; the optic axis of the window is parallel to the axis of the waveguide 1; the thickness of diaphragms 3 and 4 is 0.010 inch, the diameter of the apertures in the diaphragms are 0.205 inch; the gap between the diaphragm 3 and the end of the waveguide 1 is 0.008 inch; the diameter of the choke 9 is 0.345 inch and the depth of the choke is 0.086 inch, and the radius of the chamfered portions 10 is 0.078 inch.
  • the waveguide 11 which is coupled to the waveguide 1 may be spaced from the diaphragm 4 by a distance of 0.016 inch.
  • the dielectric loss of artificial sapphire is found to be rather less than that of the best low-loss glass at millimetre wavelengths. Moreover, the dielectric constant is more than twice as high (9.4 against 4.3) so that, the thickness for a matched window is less than half that of a glass window.
  • the cooling of the window which mainly arises by convection from the outer face of the window is, therefore, at least twice as effective and this, coupled with the high melting point of sapphire which is over 2,000 C., affords a window with a power handling capacity which is more than twice that of a glass window.
  • the window 2 is only sealed to a single diaphragm 3 and in order to obtain cancellation of reflections occurring from said window and from the edge of the diaphragm 3 the optic axis, instead of being disposed parallel to the axis of the waveguide 1, as in the arrangement shown in Figure 1 is disposed obliquely to the axis as indicated by the dotted line 16.
  • the optic axis is not perpendicular to the plane of the sapphire disc then both ordinary and extraordinary rays are propagated in the disc and give rise to reflections having an appreciable difference of phase.
  • this apparent reflecting plane can be made to coincide with the plane of the diaphragm so that a radio frequency match can be obtained with only one diaphragm.
  • this one diaphragm is disposed on the vacuum side of the window so that the limiting peak power at which the window assembly will spark is considerably raised. The obliquity of the optic axis will not be found to be so great as appreciably to disturb the thermal expansion match to the diaphragm.
  • the cross-sectional dimensions of the waveguide 1 are 0.280 inch 0.140 inch; the thickness of the window 2 is .006 inch with a dielectric constant of 9.4; the optic axis of the window makes an angle of 40 with the axis of the waveguide 1 and lies in that plane through the waveguide axis which makes an angle of 20 with the narrow side of the waveguide; the thickness of the diaphragm 3 is 0.010 inch; the diameter of the aperture in the diaphragm is 0.205 inch; the gap between the diaphragm 3 and the end of the waveguide 1 is .008 inch; the diameter of the choke 9 is 0.345 inch and the depth of the choke is 0.086 inch and the radius of the chamfered portions 10 is 0.078 inch.
  • the waveguide 11 which is coupled to the waveguide 1 may be spaced from the diaphragm 3 by a distance of 0.022 inch.
  • a device for transmitting high frequency power comprising a waveguide, a crystalline window disposed in a plane normal to the axis of the waveguide and made of a refractory material having a single optic axis and capable of transmitting high frequency power, an apertured support to which said window is sealed, said optic axis being so orientated to effect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edge of the aperture in said support.
  • a device for transmitting high frequency power comprising a waveguide, a crystalline plane window disposed in a plane normal to the axis of the waveguide and made of a refractory material having a single optic axis and capable of transmitting high frequency power, an apertured support to which said window is sealed, said optic axis being so orientated to eifect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edge of the aperture in said support.
  • a device for transmitting high frequency power comprising a waveguide, a window disposed in a plane normal to the axis of the waveguide and made of sapphire, an apertured support to which said window is sealed, the optic axis of the window being so orientated to effect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edge of the aperture in said support.
  • a device for transmitting high frequency power comprising a waveguide, a plane window disposed in a plane normal to the axis of the waveguide and made of sapphire, an apertured support to which said window is sealed, the optic axis of the window being so orientated to elfect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edge of the aperture in said support.
  • a device for transmitting high frequency power comprising a waveguide, a crystalline window disposed in a plane normal to the axis of the waveguide and made of a refractory material having a single optic axis and capable of transmitting high frequency power, an apertured support comprising two apertured metal diaphragms between which said window is sealed, said optic axis being orientated parallel to the axis along which said high frequency power is transmitted to effect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edges of the apertures in said diaphragms.
  • a device for transmitting high frequency power comprising a waveguide, a crystalline plane window disposed in a plane normal to the axis of the waveguide and made of a refractory material having a single optic axis and capable of transmitting high frequency power, an apertured support comprising two apertured metal diaphragms between which said window is sealed, said optic axis being orientated parallel to the axis along which said high frequency power is transmitted to effect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edges of the apertures in said diaphragms.
  • a device for transmitting high frequency power comprising a waveguide, a window disposed in a plane normal to the axis of the waveguide and made of sapphire, an apertured support comprising two apertured metal diaphragms between which said window is sealed, the optic axis of the window being orientated parallel to the axis along which said high frequency power is transmitted to effect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edges of the apertures in said diaphragms.
  • a device for transmitting high frequency power comprising a waveguide, a plane window disposed in a plane normal to the axis of the waveguide and made of sapphire, an apertured support comprising two apertured metal diaphragms between which said window is sealed, the optic axis of the window being orientated parallel to the axis. along which said high frequency power is transmitted to effect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edges of the apertures in said diaphragms.
  • a device for transmitting high frequency power comprising a waveguide, a crystalline window disposed in a plane normal to the axis of the waveguide and made of a refractory material having a single optic axis and capable of transmitting high frequency power, an apertured support comprising a single apertured metal diaphragm to which said window is sealed, said optic axis being orientated obliquely to the axis along which said high fre quency power is transmitted to effect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edge of the aperture in said diaphragm.
  • a device for transmitting high frequency power comprising a waveguide, a crystalline plane window disposed in a plane normal to the axis of the waveguide and made of a refractory material having a single optic axis and capable of transmitting high frequency power, an apertured support comprising a single apertured metal dia phragm to which said window is sealed, said optic axis being orientated obliquely to the axis along which said high frequency power is transmitted to effect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edge of the aperture in said diaphragm.
  • a device for transmitting high frequency power 6 comprising a waveguide, a window disposed in a plane normal to the axis of the waveguide and made of sapphire, an apertured support comprising a single apertured metal diaphragm to which said window is sealed, the optic axis of the window being orientated obliquely to the axis along which said high frequency power is transmitted to effect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edge of the aperture in said diaphragm.
  • a device for transmitting high frequency power comprising a waveguide, a plane window disposed in a plane normal to the axis of the waveguide and made of sapphire, an apertured support comprising a single apertured metal diaphragm to which said window is sealed, the optic axis of the window being orientated obliquely to the axis along which said high frequency power is transmitted to eifect substantially mutual cancellation of radio frequency reflections which arise in said window and at the edge of the aperture in said diaphragm.

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US522988A 1954-07-27 1955-07-19 High frequency transmitting windows Expired - Lifetime US2883631A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB21850/54A GB778299A (en) 1954-07-27 1954-07-27 Improvements in or relating to devices having windows for transmitting high frequency electromagnetic power

Publications (1)

Publication Number Publication Date
US2883631A true US2883631A (en) 1959-04-21

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US522988A Expired - Lifetime US2883631A (en) 1954-07-27 1955-07-19 High frequency transmitting windows

Country Status (5)

Country Link
US (1) US2883631A (zh)
DE (1) DE1003825B (zh)
FR (1) FR1134162A (zh)
GB (1) GB778299A (zh)
NL (2) NL101791C (zh)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2932806A (en) * 1958-12-02 1960-04-12 Bomac Lab Inc Broadband microwave window
US3058074A (en) * 1959-12-01 1962-10-09 Gen Electric Transmission line windows
US3101461A (en) * 1959-01-05 1963-08-20 Cie De Telegraphie Sans Fil Vacuum tight waveguide transmission window having means guarding window edges from electric stress
US4352077A (en) * 1979-05-18 1982-09-28 Varian Associates, Inc. Ridged waveguide window assembly
US5629657A (en) * 1996-04-30 1997-05-13 Hughes Electronics High power waveguide RF seal
US5770990A (en) * 1995-11-15 1998-06-23 Krohne Messtechnik Gmbh & Co. Kg Microwave window
CN104638320A (zh) * 2015-02-10 2015-05-20 中国电子科技集团公司第十六研究所 大口径低损耗微波真空窗口

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1222585A (fr) * 1959-01-05 1960-06-10 Csf Dispositif anti-rupture pour fenêtres isolantes de sortie de tubes hyperfréquencesde grande puissance

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2567701A (en) * 1944-06-02 1951-09-11 Gen Electric Ultra high frequency coupling device for wave guides
US2637776A (en) * 1948-04-20 1953-05-05 Bell Telephone Labor Inc Sealed wave guide window
GB724195A (en) * 1951-10-19 1955-02-16 Gen Electric Co Ltd Improvements in or relating to electrical devices including hollow tubes adapted to act as waveguides

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2567701A (en) * 1944-06-02 1951-09-11 Gen Electric Ultra high frequency coupling device for wave guides
US2637776A (en) * 1948-04-20 1953-05-05 Bell Telephone Labor Inc Sealed wave guide window
GB724195A (en) * 1951-10-19 1955-02-16 Gen Electric Co Ltd Improvements in or relating to electrical devices including hollow tubes adapted to act as waveguides

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2932806A (en) * 1958-12-02 1960-04-12 Bomac Lab Inc Broadband microwave window
US3101461A (en) * 1959-01-05 1963-08-20 Cie De Telegraphie Sans Fil Vacuum tight waveguide transmission window having means guarding window edges from electric stress
US3058074A (en) * 1959-12-01 1962-10-09 Gen Electric Transmission line windows
US4352077A (en) * 1979-05-18 1982-09-28 Varian Associates, Inc. Ridged waveguide window assembly
US5770990A (en) * 1995-11-15 1998-06-23 Krohne Messtechnik Gmbh & Co. Kg Microwave window
US5629657A (en) * 1996-04-30 1997-05-13 Hughes Electronics High power waveguide RF seal
CN104638320A (zh) * 2015-02-10 2015-05-20 中国电子科技集团公司第十六研究所 大口径低损耗微波真空窗口

Also Published As

Publication number Publication date
FR1134162A (fr) 1957-04-08
NL101791C (zh)
GB778299A (en) 1957-07-03
DE1003825B (de) 1957-03-07
NL198932A (zh)

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