US2608670A

US2608670A - High-frequency tube structure

Info

Publication number: US2608670A
Application number: US716211A
Authority: US
Inventors: Edward L Ginzton
Original assignee: Sperry Corp
Current assignee: Sperry Corp
Priority date: 1942-01-29
Filing date: 1946-12-14
Publication date: 1952-08-26
Anticipated expiration: 1969-08-26
Also published as: GB606794A; FR999982A; GB606804A; GB606801A; NL77933C; GB607203A; GB606802A; GB606803A; GB607201A

Description

Aug. 26, 1952 E. L. GINZTON 2,603,670

HIGH-FREQUENCY TUBE STRUCTURE Original Filed Jan. 29, 1942 INVENTOR. [OW/9RD L $m/z7'0/s/ A TTOR/VEY Patented Aug. 26, 1952 2,608,678 HIGH-FREQUENCY TUBE STRUCTURE.

Edward L. Ginzton, Redwood, Calif., assignor to The Sperry Corporatloma corporation of Delaware Original application January 29, 1942, Serial No. 428,682. Divided and this application December 14, 1946, Serial No. 716,211

10 Claims. 1

The present invention relates to the art including electron discharge devices and is more particularly directed to improvements in such devices utilizing cavity resonators and adapted to operate at ultra-high and super-high frequencies (also termed microwaves) "of the order of about 300 megacycles per second and higher.

The present application is a division of application Serial No. 428,682 for High Frequency Tube Structure filed January 29, 1942 issued as Patent No. 2,414,785 on January21, 1947.

As disclosed in United States Patents No. 2,280,824 and No. 2,391,016, it is known to provide a vacuum envelope containing the electrodes producing and interacting with an electron stream, and to provide a cavity resonator external of the envelope and coupled through the envelope to the stream-interacting electrodes. An example of such a structure is shown in Fig. 7 of the above-mentioned Patent No. 2,391,016 wherein this type of apparatusis included in a reflex klystron tube. l I

Especially where capacitive coupling between the external resonator and the internal electrodes is used, difliculty may be encountered because of the leakage of high frequency energy through the dielectric material of the envelope between the resonator and the'electro'des within the envelope. This effect decreases the useful Y.

power output and also impairs the effectiveness of the resonator by lowering its shunt impedance.

The present invention is directed toward improved apparatus for overcoming these difficulties. I

According to the present invention, a microwave filter structure is provided in conjunction with external cavity resonators of this type so as to present substantially a short circuit or zero impedance between the internal electrodes and the external resonator. From another viewpoint, this structure provides a wave trap arrangement preventing microwave leakage.

Accordingly, it is an object of the present invention to provide improved electron'discharge apparatus having cavity resonator structures external to the vacuum envelope and substantially minimizing undesired leakage from such reso nator.

In particular, it is an object of th e present invention to provide an improved reflex klystron device wherein the beam-producing and controlling electrodes are contained within a vacuum envelope with a cavity resonator external to the envelope and capacitively coupled tothe internal electrodes, means being provided according to the invention forminimizing leakage from betweenthe resonator'and its electrodes andfor providing a substantially zero impedance therebetween. v

Other'objects and advantages will become ap parent from the following specification taken in connection with the appended drawings, in which Fig. 1 is a longitudinal cross-sectional view of a preferred embodiment of the present invention, and

Fig. 2 is a cross-sectional view of the device of Fig. 1 taken along line 22 thereof, and turned 90 degrees.

Referring to the drawing, there is shown an evacuated envelope having a tubular smalldiameter section 89, and an enlarged section [ll connected thereto by a connecting portion I. Preferably, envelope section 89 is formed of dielectric material having low-loss at the operating frequency and may, for example, be formed of quartz. Section [0 may be formed of a conventional soft glass suitable for forming into a press such as shown at 93, the connecting section I being a graded seal for connecting these two different materials. Contained within envelope section 89 is a cathode 90 supported upon an insulator 80, which in turn, is supported from press 93 by rigid leads 92. Adjacent the upper end of cathode 98, which is its emitting surface, are a pair of grids B5, 88 formed, for example, of radially inward-directed strips fixed to a supporting encircling ring. Grids 85, 88 are supported at the adjoining ends of respective tubular members 84, 81, which, are positioned within envelope section 89 and close to the inner surface thereof. On the side of grid 85 opposite cathode 90 is a reflector electrode 9| rigidly supported by a lead 10 from the upper end of envelope section 89. Tubular members 84, 81 have respective leads 30, 3|, which serve to position these members and to provide leads for applying suitable potentials thereto. I

Surrounding the envelope section 89 is a cavity resonator structure 82, having a pair of tubular portions 83, 8 6 closely surrounding envelope 89 and capacitively coupled to the tubular members 84, 81 respectively through the vacuum envelope 89. Resonator 82 also has an outer cylindrical wall 96 connected to the

tubular members

83, 86 by respective disc walls H, 12. In this way, the field within resonator 82, and especially that portion thereof between the juxtaposed ends of

tubular members

83, 86, is impressed between electrodes 85, 88 by means of the capacitive coupling between

tubular members

83 and 84 and between 86 and 81.

This structure thus far described is very similar to that shown in Fig. '7 of the above mentioned Patent No. 2,391,016. However, serious lossof energy which may result by leakage out through the vacuum envelope 89 from between the

capacitive elements

83, 84 and 86,

8'! is greatly minimized in the present construction. The outer cylindrical wall'of resonator is 82 is extended in both directions to form the outer wall of cavities 9'5, 98 on each side thereof. The ends of cavity 81, 98 are closed by apertured discs 99, I60 respectively thereby forming an enclosing vessel having three

cavities

82, 91 and 98 therein. Tubular conductors llll, l02'snugly fitting the vacuum envelope 89 are fastened within the apertures of discs 99, I respectively; whereby a portion of each of these tubes I0 I, I02 extends into the

cavities

91, 98 and a portion extends beyond the discs 99, 1'80 respectively. Tubes HM, 83, 8 and 102 are each made substantially electrically a quarter-wavelength long, the distance between tubes Nil and 83 and that between tubes 86 and 192 also being substantially electrically equal to a quarter-wavelength of the operating frequency.

The manner in which this construction minimizes microwave energy leakage, will be apparent from the following theoretical considerations. Tube 32 and member 81 form a coaxial transmission line of length equal to one-quarter-wavelength and of a characteristic impedance which may be designated by Z1. The impedance at point 3 viewed outwardly from the resonator is largely resistive and may be designated by R. By virtue of the transmission line 102, 81, this resistance R, istransformed to an impedance equal to viewed outwardly from point ,4. If the characteristic impedance defined by cavity 98 be designated as Z2, the impedance at point 5 viewed toward point 4 is V Z2 R X (a) Tubes 36 and 81 form a quarter-wavelength section of concentric transmission line of character istic impedance equal to Z1. Therefore, the impedance at point 6v viewed outwardly is given by the following expression:

Since Z1 is relatively small and Z2 is relatively large, this last value of impedance is very small so that little or no energy can leak down the envelope 89 to the external point 3. It will be understood that similar considerations apply with respect to leakage upwardly from the gap between grids 8'5 and 88.

For withdrawing useful output from resonator 82, a concentric transmission line terminal H, having a coupling loop l2 perpendicularto the plane of the section of Fig. 2 is insulatedly supported from resonator 82 by meansof an insulating-bushing is so that resonator '82 may be held at any desired potential relative to line i E. Tuning of resonator 82 may be accomplished by means of a plug M threaded to the wall of resonator 82. Adjustment of the extension of screw 4 l4 into resonator 82 accomplishes tuning of the resonator in the manner disclosed in United States Patent 2,259,690. Similar or other tuning means may be provided in cavities 9'! and 98 as desired.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departure from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In a. high frequency tube structure, means for producing an electron stream, an evacuated substantially cylindrical insulating envelope surrounding said stream, spaced grid members within said envelope, a hollow resonator capacitively coupled through said envelope to said grid members for setting up an alternating electric field therebetween for coacting with said electron stream, and means including a portion of said envelope and said resonator providing an impedance between said grid members and the respective ends of said envelope for reducing, the escape of electromagnetic energy endwise of said envelope, said last-named means including a quarter wavelength coaxial 7 transmission line having open ends. a

2. Apparatus as defined in claim 1 wherein said last-named means includes resonant chamber means for loading the end 'of said transmission linemost remote from said grid members with a relatively high impedance.

3. A high frequency tube structure as defined in claim 2 wherein said coaxial transmission line is coaxial with said cylindrical envelope, one end of said line extending substantially to one of said grid members, and said resonant chamber means communicating with said alternating electric field via the material of said envelope. 1

4. A high frequency tube structure as defined in claim 1 wherein one end of said coaxial transmission line extends to the juncture of said grid members and said hollow resonatonsaid linebeing coaxial with the path of said-electron stream, and a further open-ended quarter wavelength transmission line is provided, said further line be.- ing spaced 2, quarter wavelength from the end of said first-mentioned line most remote from said grid members, both said lines having inner and outer conductors in contact with said envelope.

5. In a high frequency tube structure, electronstream-producing means, an evacuated insulating envelope surrounding the path of said stream, a tubular sleeve coaxial with said path, spaced gridmembers within said envelope and defining a gap, one of said grid members being located adjacent one end of said sleeve, a hollow resonator capacity-coupled through said envelope to said grid members for setting up an alternating electric field there'oetween for coacting with said electron stream, a portion of said sleeve and a portion of said resonator providing an open-ended quarter wavelength coaxial transmission line having one. end adjacent said gap, and resonant chamber means for providing a variable imped-.

ance along the length of said envelope substantially a distance electrically equal to a quarter wavelengthextending from the other end of said transmission line in a direction away from said gap, whereby the escape of electromagnetic energy endwise of said envelope is minimized.

6. A high frequency tube. structure comprising an evacuated insulating envelope, tube electrodes within said envelope disposed so that their opposed ends are somewhat spaced apart, a hollow resonator surrounding said envelope, said resonator being coupled to said tube electrodes and serving to establish an alternating electric field between the opposed end portions of said tube electrodes, means for setting up an electron stream within said envelope coacting upon said alternating electric field, and filter means comprising cavity members located at opposite ends of said hollow resonator and surrounding said envelope, said cavity members being capacity coupled to said tube electrodes and providing impedance means variable along the length 01' said envelope substantially a distance electrically equal to a quarter wavelength for blocking the escape of energy endwise of said insulating envelope, said resonator cooperating with said envelope to provide a quarter wavelength trap for further blocking the escape energy endwise of said envelope.

'7. A high frequency tube structure comprising an evacuated substantially cylindrical envelope, means within said envelope for producing an electron stream, a pair of spaced electrodes within said envelope along the path of said stream and defining a gap therebetween, a pair of first tubular members outside said envelope having a gap registering with said first gap, said first members being electrically one-quarter-wavelength long at the operating frequency, means coupled to said members and defining a cavity resonator therewith, and means for presenting leakage of high frequency energy from between said electrodes and said members, said last-named means comprising a pair of further quarter-wavelength tubular members each surrounding said envelope and spaced a quarter-wavelength from a respective one of said first members, and means coupled between one of said first tubular members and one of said further tubular members and defining therewith a cavity having a high characteristic impedance for minimizing energy leakage.

8. Tube structure as in claim 7 further including a pair of tubular members within said envelope connected respectively to said electrodes and coaxial with said first and further tubular members, and forming therewith over their coextensive portions coaxial line sections of low characteristic impedance.

9. A high frequency tube structure comprising an evacuated substantially cylindrical envelope, means within said envelope for producing an electron stream, a pair of spaced electrodes within said envelope along the path of said stream and defining a gap therebetween, a pair of first tubular members outside said envelope having a gap registering with said first gap, said members be ing a, quarter-wavelength long at the operating frequency, a second tubular member within said first envelope connected to one of said electrodes and coaxial with said first tubular members means coupled to said first members and defining a first cavity resonator therewith, means comprising a, third quarter-wavelength tubular member surrounding the envelope and spaced a quarter-wavelength from the end of one of said pair of tubular members most remote from said electrodes, and means including a portion of said first cavity resonator defining means and a portion of said third member coupled between said one of said first tubular members andsaid third further tubular member and defining a second cavity resonator having a high characteristic impedance, one of said first members and said third member forming with the co-extensive portions of said second member coaxial line sections of low characteristic impedance, whereby energy leakage is minimized.

10. An electron discharge device comprising a vessel having a portion defining a cylindrical, metallic concave surface, a unitary electrode assembly within said vessel including a pair of cooperative electrodes, and means mounting said electrode assembly within said vessel including a cylindrical metallic member connected electrically to one of said electrodes and a cylinder of dielectric material, surrounding said cylindrical metallic member, said cylinder of dielectric material being located immediately adjacent said cylindrical concave surface and defining a con denser therewith and with said cylindrical member.

EDWARD L. GINZTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,128,234 Dallenbach Aug. 30, 1938 2,163,589 Dallenbach et a1. June 27, 1939 2,167,201 Dallenbach July 25, 1939 2,391,016 Ginzton et al Dec. 18, 1945 2,411,299 Sloan Nov. 19, 1946