US2972700A

US2972700A - Ultra-high frequency oscillator tubes

Info

Publication number: US2972700A
Application number: US502267A
Authority: US
Inventors: Charles Daniel; Dohler Oscar
Original assignee: CSF Compagnie Generale de Telegraphie sans Fil SA
Current assignee: Thales SA
Priority date: 1954-04-27
Filing date: 1955-04-19
Publication date: 1961-02-21
Anticipated expiration: 1978-02-21
Also published as: FR1106301A; GB773834A

Description

Feb. 21, 1961 D. CHARLES EI'AL 2,972,700

ULTRA-HIGH FREQUENCY OSCILLATOR TUBES Filed April 19, 1955 2 Sheets-Sheet 1 Fig.1.

Fig.2.

Feb. 21, 1961 D. CHARLES ETAL ULTRA-HIGH FREQUENCY OSCILLATOR TUBES 2 Sheets-Sheet 2 Filed April 19, 1955 ULTRA-HIGH FREQUENCY OSCILLATOR TUBES Daniel Charles and Oscar Dohler, Paris, France, assignors to Compagnie Generale de Telegraphic Sans Fil, a corporation of France Filed Apr. 19, 1955, Set. No. 502,267 Claims priority, application France Apr. 27, 1954 15 Claims. (Cl. SIS-3.6)

The present invention relates to high frequency oscillators, and more particularly to centimetric and millimetric wave oscillators.

Oscillators are already known in which the oscillations are produced by the interaction between one or more electron beams and the field of a geometrically periodical line in which the ultra-high frequency waves are generated.

It is sometimes difficult to construct a delay line capable of propagating ultra-high frequency waves in a given frequency band. In particular, when the wavelength is in the millimetric band, it becomes increasingly difiicult to construct the delay line with a sufiicient precision; the slightest irregularity in its configuration, for example, in its geometrical periodicity, may sufiice to make the line unable to propagate the ultra-high frequency waves in the desired band, which makes the oscillator unable to operate.

It is an object of the present invention to provide a new oscillator in which oscillations are obtained by means of a periodical structure unable to propagate ultra-high frequency waves along its length, i.e. a structure offering an infinite impedance to the propagation therealong of ultrahigh frequency waves, which accordingly does not require the high degree of accuracy necessary in traveling wave oscillators and is therefore easier to manufacture.

The oscillator tube in accordance with the invention comprises two electron emissive sources positioned to propagate two parallel beams in opposite directions. These beams are separated along their length by a geometrically periodical structure along which electromagnetic waves are incapable of being propagated in the operating frequency band of the tube, i.e., a structure ofiering an infinite impedance to the propagation therealong of ultra-high frequency waves in the operating band of this tube. Such a structure may, for instance, be a ladder line of the type shown by Pierce in his book Traveling Wave Tubes, Van Nostrand, New York 1950, in Figs. 5, 7, page 90. It may also consist of a grid with square, circular or polygonal meshes. As will be shown hereinafter, in operation, the two beams of this tube interact with each other thereby converting the direct current energy applied to the tube into ultra-high frequency oscillations.

The invention will be better understood from the following description with reference to the attached drawings wherein:

Fig. 1 shows in longitudinal section one embodiment of the tube in accordance with the invention;

accordance with the invention.

The tube shown in Fig. 1 comprises, within a cylindrical evacuated envelope 12, a cathode 8 at one end thereof,

.and an annular cathode 9 at the opposite end. These two States Patent cathodes which are substantially coaxial with the envelope 12 emit, respectively in opposite directions, two coaxial 2,912,100 Patented Feb. 21, 1961 beams 1 and 2. Beam 2 is cylindrical and beam 1 is tubular. The electrons of these beams are respectively captured at the end of their paths by collectors 10 and 11, the latter being annular in form. The beams are separated by a cylindrical structure 3, shown in longitudinal and transverse sections respectively in Figs. 2 and 3. This structure consists of a series of wires coiled in parallel rings 18, separated by gaps 16 and supported by metal mountings 17 to which these rings are integrally connected. This type of line is known as ladder type line and forms in fact a grid. It is known that in such a geometrically periodical structure electromagnetic waves are not propagated, as shown for instance by Pierce (see above). At both ends of structure 3 are respectively arranged two delay line sections 6 and 7, for instance, intended only for coupling the two beams 1 and 2 to the output circuits respectively in the desired frequency band. The ends of these sections in the neighborhood of structure 3 are provided with attenuators 4 and 5, to absorb without reflection any energy that might be propagated in those sections toward these attenuators, for instance, because of a mismatch between the output and a load connected thereto. These attenuators may for instance be constituted by a dissipative substance such as aquadag covering the ends of the sections 6 and 7. The other ends of the latter are coupled, in the neighborhood of the cathodes, to the respective outputs 14 and 15 which may be joined together by means of a connection 30 shown diagrammatically inside the tube.

It is assumed, for instance that collectors 10 and 11 and delay lines 6 and 7 are grounded and the cathodes 8 and 9 are raised by a source 19 to a negative potential which can be adjusted by means of the tap 21. The structure 3 is brought to a positive potential with respect to the cathodes 8 and 9 by means of a source 20, provided for instance with a potentiometer 13 having a variable .tap 22.

In operation, by suitably adjusting the respective velocities of the beams 1 and 2, ultra-high frequency oscillations are provided at the outputs 14 and 15.

The adjustment of the beam velocities is performed by adjustingthe positive potential of the structure 3, whereby both beams 1 and 2 will have substantially the same velocity.

The operation of this device according to the invention may be explained in the following way, although applicant does not wish to be bound by any theoretical explanation.

Supposing one of beamsl and 2 is initially density modulated, then the high frequency electric field of the space charge due to this beam penetrates through period- 'ically spaced apertures in the structure 3 and interacts with the second beam, thereby velocity modulating the electron flow thereof. Since this second beam propagates in a direction opposite to the first beam and at uniform velocity, this velocity modulation takes place at a series of periodically spaced points in the beam. As the second beam progresses, the velocity modulation transforms itself into density modulation, thereby creating a high frequency electric field of the space charge due to the second beam. This high frequency electric field reciprocally penetrates through apertures of the structure 3 and interacts with the first beam, thereby creating in the flow thereof velocity modulation at a series of periodically spaced points. Since this velocity modulation transforms itself into density modulation of the first beam, it may be readily seen that there is reciprocal feedback interaction between both beams through these apertures of the periodic structure, whereby density'modulations are amplified and oscillations are able to start up, if the beam currents are sufficiently high. The initial density modulation may be due to the noise inherently present in the beams. As

Designating the frequency of the output oscillations by f and the pitch of the structure 3 by p, it may be the- .oretically stated that assuming the velocities of both me. 5. p

If V=2,500 volts and 2p=0.04 cm., the output frequency 7 will be of 75,000 mc./s., i.e., the wavelength of the output energy will be '4 mm. which shows that the oscillator is well suited to be used as a millimeter wave oscillator. The voltage V may be regulated by means of the potentiometer 13. I

It may be easily shown that if the beam 1 has a velocity v and beam 2 a velocity v the output frequency is equal to beams being equal:

1 1.1 2 p( i+ z) Of course, more than two beams having same or difierent velocities could be used.

Another embodiment of the invention is shown in Figs. 4 and 5. In this tube the

beams

31 and 32 are propagated in a direction normal to an electric and magnetic field which are perpendicular to each other.

In the embodiment shown, the tube comprises a metallic envelope 33 whose lateral walls are joined by metallic bars 34 forming a ladder type delay line 35. Parallel to this line are located two

smooth electrodes

36 and 37, respectively on opposite sides of the line 35. They bound with the latter two interaction spaces where

beams

31 and 32 are respectively propagated from two

guns

38 and 39 respectively located at the opposite ends of the tube substantially at the same level as

electrodes

36 and 37 respectively. The latter are negatively biassed with respect to the structure 35 which is grounded, by means of sources 40 and 41 respectively, and are made .slightly positive with respect to the respective cathodes of the

guns

38 and 39 by means of

sources

42 and 43 respectively. A magnetic field, normal to the beam propagation direction and to the electric field set up by the sources 42 and 4-3, is provided in the interaction spaces by means of polar pieces 4 and 45 which may be seen in Fig. 5.

The electrons of the beams are respectively collected at the end of their travel by collectors 46 and 47.

It should be noted that the structure and the relative location of the

electrodes

36 and 37 of the

electron guns

38 or 39, and of the polar pieces 44 and 45, are entireIy similar to those encountered in any travelling wave tube of the magnetron type.

At the end of their respective paths, the

beams

31 and 32 pass through delay line portions 48 and 49, which, in the embodiment shown, are flat helices whose ends remote from the adjacent collector are covered with an absorbing material as in the case of Fig. 1. As in this latter case, they serve to couple the beams to the outputs S and 51 respectively.

The velocity of the beams may be adjusted for instance by means of the

adjustable taps

52 and 53, or by adjusting the intensity of the magnetic field.

The operation of the tube is the same as in the casev of Fig. 1.

It will be appreciated that many variations, obvious to those skilled in the art, may evidently be considered without departing from the scope of the invention. In particular, the tube of Fig. 4- could be of circular shape instead of being of straight shape.

We claim:

1. A microwave oscillator tube for a given frequency band, comprising within an evacuated envelope: a geometrically periodical electrically conductive structure, having periodically spaced apertures, two ends and two sides, and offering an infinite impedance to the propagation therealong of electromagnetic waves in at least said given frequency band; two electron sources each positioned at one end and respectively on opposite sides of said structure, to emit respectively in opposite directions two electron beams parallel to said structure and effectively entering into mutual interaction only through said periodically spaced apertures of said structure; two collectors each positioned at one end andrespectively on opposite sides of said structure to collect respectively the electrons of said beams; means for controlling the velocity of said beams; output means at least at one end of said structure; and coupling means for coupling in said predetermined frequency band the electromagnetic field of at least one of said beams to said output means.

2. A microwave oscillator tube for a given frequency band, comprising Within an evacuated envelope: a geometrically periodical electrically conductive structure, having periodically spaced apertures, two ends and two sides, and offering an infinite impedance to the propaga tion therealong of electromagnetic waves in at least said given frequency band; two electron sources each positioned at one end and respectively on opposite sides of said structure, to emit respectively in opposite directions two electron beams parallel to said structure and effectively entering into mutual interaction only through said periodically spaced apertures of said structure; two collectors each positioned at one end and respectively on opposite sides of said structure to collect respectively the electrons of said beams; means for bringing said structure to a predetermined direct current potential; output means at least at one end of said structure; and coupling means for coupling in said predetermined frequency band the electromagnetic field of at least one of said beams to said output means.

3. A microwave oscillator tube for a given frequency band, comprising within an evacuated envelope: a geometrically periodical electrically conductive structure, having periodically spaced apertures, two ends and two sides, and offering an infinite impedance to the propagation therealong of electromagnetic waves in at least said given frequency band; two electron sources each positioned at one end and respectively on opposite sides of said structure, to emit respectively in opposite directions two electron beams parallel to said structure and effectively entering into mutual interaction only through said periodically spaced apertures of said structure; two collectors each at one end and respectively on opposite sides of said structure to collect respectively the electrons of said beams; means for controlling the velocity of said beams; output means at least at one end of said structure; and at least one delay line section adjacent one of said collectors and in coupled relationship with at least one beam and with said output in said predetermined frequency band.

4. A microwave oscillator tube for a given frequency band, comprising within an evacuated envelope: a geometrically periodical electrically conductive structure, having periodically spaced apertures, two ends and two sides, and ofiering an infinite impedance to the propagation therealong of electromagnetic waves in at least said given frequency band; two electron sources each positioned at one end and respectively on opposite sides of said structure, to emit respectively in opposite directions two electron beams parallel to said structure and effectively entering into mutual interaction only through said periodically spaced apertures of said structure; two collectors each positioned at one end and respectively on opposite sides of said structure to collect respectively the electrons of said beams; means for controlling the -velocity of said beams; two outputs each positioned at one end of said structure; and two delay line portions respectively adjacent said collectors and respectively in coupled relationship with at least one of said beams and said outputs in said predetermined frequency band.

, 5. A microwave oscillator tube for a given frequency band, comprising within an evacuated envelope: a geometrically periodical electrically conductive structure, having periodically spaced apertures, two ends and two sides, and olfering an infinite impedance to the propagation therealong of electromagnetic waves in at least said given frequency band; two electron sources each positioned at one end and respectively on opposite sides of said structure, to emit respectively in opposite directions two electron beams parallel to said structure and effectively entering into mutual interaction only through said periodically spaced apertures of said structure; 'two collectors each positioned at one end and respectively on opposite sides of said structure to collect respectively the electrons of said beams; two elongated electrodes parallel to said structure and defining therewith two interaction spaces; means for providing in said interaction spaces an electric field and a magnetic field normal to each other and to the propagation direction of said beams; two outputs each positioned at one end of said structure; and two delay line portions respectively adjacent said collectors and in respective coupled relationship with said beams and said outputs in said predetermined frequency band.

6. A microwave oscillator tube for a given frequency band, comprising means forming a geometrically periodical structure essentially preventing propagation therealong of electromagnetic waves in at least said given frequency band and provided with aperture means, means for propagating two electron beams in opposite directions with respect to each other and exclusively on opposite sides of said first-mentioned means to generate oscillatory electromagnetic energy by the effective mutual interaction of said two beams through said aperture means, and output means for extracting said oscillatory electromagnetic energy from said tube.

7. A microwave discharge system adapted to operate as an ultra-high frequency oscillator within a given frequency band, comprising means for producing a plurality of electron beams having velocity components in mutually opposite directions and propagating to provide an area of overlap in the direction of said components, means including a geometrically periodical structure located within said area of overlap and essentially preventing propagation therealong of electromagnetic waves within at least said given frequency band for generating oscillatory electromagnetic energy by the mutual interaction of the effects of 'said beams within said area of overlap, and output means for extracting said oscillatory energy from said tube.

8. A microwave discharge system adapted to operate as an ultra-high frequency oscillator within a given frequency band and provided with means forming a geometrically periodical structure essentially inoperative to enable the propagation therealong of electromagnetic energy within at least said given frequency band, comprising cathode means operative to emit electrons adapted to flow in a plurality of paths along at least a portion of said geometrically periodical structure, means including said portion of said geometrically periodical structure for generating oscillatory electromagnetic energy within said tube by the indirect interaction of the electron flow in said paths in relation to said geometrically periodical lap in the region of said portion of said geometrically periodical structure in the direction of said components, and output means for extracting said oscillatory electromagnetic wave energy from said tube.

9. A microwave discharge system adapted to operate as an ultra-high frequency oscillator within a. given frequency band, comprising means for producing a plurality of electron beams having velocity components in mutually opposite directions and propagating to provide an area of overlap in the directionof said components, means including a geometrically periodical structure having means essentially preventing propagation therealong of electromagnetic waves within at least said given frequency band and located within said area of overlap between beams having velocity components in said opposite directions for generating oscillatory electromagnetic energy by the mutual interaction of the electric fields of said beams within said area of overlap, and output means for extracting said oscillatory energy from said tube.

10. A microwave discharge system according to claim 9 'wherein said geometrically periodic structure is provided with a plurality of spaced apertures.

11. A microwave discharge system adapted to operate as an ultra-high frequency oscillator within a given frequency band, comprising means for producing two electron beams having velocity components in mutually opposite directions and propagating to provide an area of overlap in the direction of said components, means including a geometrically periodical structure essentially preventing propagation therealong of electromagnetic waves within at least said given frequency band and located intermediate said two beams for generating oscillatory electromagnetic energy by the mutual interaction of the effects of said .beams through said geometrically periodic structure within said area of overlap, and output means for extracting said oscillatory energy from said tube.

12. A microwave discharge system according to claim 11, wherein each of said beams is of substantial width.

13. A microwave discharge system adapted to operate as an ultra-high frequency oscillator within a given frequency band and provided with means forming a geometrically periodical structure essentially inoperative to enable the propagation therealong of electromagnetic energy within at least said given frequency band, comprising cathode means operative to emit electrons adapted to 'fiow in a plurality of paths along at least a portion of said geometrically periodical structure and on opposite sides thereof, means including said portion of said geometrically periodical structure for generating oscillatory electromagnetic energy within said tube by the mutual interaction of the electron flow in said paths in relation to said geometrically periodical structure including means for producing electron flow in said paths having velocity components in essentially mutually opposite directions and defining an area of overlap in the region of said portion of said geometrically periodical structure in the direction of saidcomponents, and output means for extracting said oscillatory electromagnetic wave energy from said tube.

14. A microwave discharge system adapted to operate as an ultra-high frequency oscillator within a given frequency band, comprising means for producing two electron beams having velocity components in mutually opposite directions and propagating with a spatial extension such that the projection of one of said beams on the other defines a common area extended substantially in the direction of said components, means including a geometrically periodical structure disposed between said beams with-in said common area and essentially preventing propagation therealong of electromagnetic waves within at least said given frequency band for generating oscillatory electromagnetic energy by the mutual interaction of the electric fields of said beams Within said area of overlap, and output means for-extracting said oscillatory ture essentially inhibiting propagation therealong of elecf tromagnetic waves within at least said given frequency bandand provided with aperture means, means for propagating two electron beams of substantial width on opposite sides of said first-mentioned means in diiferent directions with velocity components thereof in mutually opposite directions and defining a common area of overlap in said mutually opposite directions by the projection of one of said beams on the other for generating oscillatory electromagnetic energy by the effective mutual intermittent interaction of said two beams through said aperture means, and output means for extracting said oscillatory electromagnetic energy from said tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,636,948 Pierce Apr. 28, 1953 8 Hollenberg Sept..1'5, Pierce- May 10, Pierce Jan. .10, Webber Feb. 14, Hagelbarger et a1. May 15, Walker May 15, Huber et al. July 31, Cutler Oct. 22, Diemer July 22, Ashkin et al. Jan. 27, Charles et al. Nov. 3,

FOREIGN PATENTS France July 18, Great Britain Nov. 4, Great Britain Mar. 24,

OTHER REFERENCES Traveling Wave Tubes, by J. R. Pierce, pub. 1950 by V. Van Nostrand Co., Inc., New York, page 90.