US2967259A - Resistance-strapped helix for a traveling wave tube - Google Patents
Resistance-strapped helix for a traveling wave tube Download PDFInfo
- Publication number
- US2967259A US2967259A US829169A US82916959A US2967259A US 2967259 A US2967259 A US 2967259A US 829169 A US829169 A US 829169A US 82916959 A US82916959 A US 82916959A US 2967259 A US2967259 A US 2967259A
- Authority
- US
- United States
- Prior art keywords
- helix
- resistance
- strapped
- wave
- wave tube
- 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
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
- H01J23/16—Circuit elements, having distributed capacitance and inductance, structurally associated with the tube and interacting with the discharge
- H01J23/24—Slow-wave structures, e.g. delay systems
- H01J23/26—Helical slow-wave structures; Adjustment therefor
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
- H01J23/16—Circuit elements, having distributed capacitance and inductance, structurally associated with the tube and interacting with the discharge
- H01J23/24—Slow-wave structures, e.g. delay systems
- H01J23/30—Damping arrangements associated with slow-wave structures, e.g. for suppression of unwanted oscillations
Definitions
- This invention relates to a slow-wave structure for traveling-wave amplifier tubes and more particularly to a resistance-strapped helix.
- An object of the invention is to provide a travelingwave amplifier tube which has a large 3-db bandwidth and which is very nearly free from self-oscillation caused by beam interaction with a backward space harmonic of the structure having a velocity very nearly synchronous with the electron beam.
- bandwidth is meant to those skilled in the art that the ratio of the frequencies at the 3-db down points on the response curve is of the order of 1.521 or 2:1.
- Fig. 1 is a more or less schematic representation of a traveling-wave tube showing a preferred embodiment of the helix of this invention
- Fig. 2 is an enlarged axonometric view of a portion of the helix removed from the tube of Fig. l;
- Fig. 3 is a cross-section taken along the line 33 in Fig. 1.
- the illustrated embodiment is a bifilar helix although the invention comprehends the use of multifilar helices made of more than two helices.
- the bifilar helix comprises two separate helices 2 and 4 of uniform conducting tapes of width W and thickness T. Each has the form of a helix of constant pitch p (the axial distance in which the conductor makes one complete rotation about the axis) constant pitch angle ,9 (the angle between a line tangent to an edge of one of the tapes and a plane perpendicular to the cylindrical axis of the helix), and constant mean radius a.
- the helices are spaced equally from each other a distance d.
- the helices are connected across the center of the structure every distance d by means of resistance straps generally indicated at 6.
- the portions 8 of each strap are shown as being conducting bars and the central portion is a resistance. very small region on the axis of the helix extending, for example, a distance not greater than /6 of the strap.
- another embodiment envisions a resistance strap or lossy strap which is uniformly lossy through its length.
- the resistance straps can be fabricated in any one of a number of ways which would be apparent to those skilled in the art.
- the conducting sections 8 can be simply solid conductors forming good electrical contact with the helix conductors and the resistor 10 can be a very thin microwave resistor known in the art or any other suitable resistor.
- the helix of the illustrated embodiment is shown in.
- a conventional traveling-wave tube generally indicated at 12 which includes an electron gun 14 and a collector 16 as well as input terminals 18 and output terminals 20.
- the helix is supported by dielectric rods passing through its interior but omitted from the drawing for the sake of clarity.
- the unstrapped bifilar helix has an infinity of possible modes of propagation, two of which are important here.
- the symmetric mode is characterized by having the same RF voltage on both helix conductors at any given cross-section.
- the symmetric mode has a forward-traveling space harmonic which is useful for wideband forward-wave amplification.
- the antisymmetric mode is characterized by having opposite voltages on the two helix conductors at any given cross-section.
- the antisymmctricmode has a very strong backward space harmonic that will generally cause oscillations under the operating conditions necessary for forward amplification.
- a periodicity can be introduced in one mode which does not affect the other, with the result that a mode-selective stop band is created.
- the circuit can be made lossy in one mode, with negligible loss in the other. Since excess loss is wanted in the antisymmetric mode, to prevent oscillations occasioned by the strong backward space harmonic, the invention involves the insertion of series resistance which absorbs energy from the conduction current in the strap. With an ideal infinitesimal resistor at the center of each strap, the attenuation is zero in the symmetric mode because of the null in current flow at the position of the resistor.
- the amount of attenuation and the size of the resistor in a practical case required to suppress backward wave oscillations depend on the details of a particular tube design.
- the calculation of the particular resistor size can be performed using, for example, the analysis set forth in the article entitled Strapped Bifilar Helices for High-Peak-Power Traveling- Wave Tubes by Watkins and Dow, IRE Transactions on Electron Devices, January 1959, page 106, et seq.
- lossy strap can be represented by a strap wnich is uniformly lossy along its length instead of having its resistance concentrated on the axis of the helix. This form has a large amount of mode-selective loss, but is not completely selective.
- a slow-wave structure for use in traveling-wave tubes comprising a multifilar helix including a plurality of separate helices, each separate helix having the same constant pitch; the;- same constant pitch angle, and the same mean radius; said helices being spaced equally from each other along a common axis; and a plurality of 2.
- the slow-wave structure of claim 1 wherein, the,
- multifilar helix is a bifilarhelix.
- a traveling-wave tube an electron gun, a collector for electrons, and a slow-wave structure; said slow-wave structure being; structure of claim 1'.
Description
Jan. 3, 1961 RQP. LAGERSTROM ET AL 2,967,259
RESISTANCE-STRAPPED HELIX FOR A TRAVELING WAVE TUBE Filed July 25, 1959 INVENTORS RICHARD P LAGERSTROM DAN/EL 6. DOW
RESISTANCE-STRAPPED HELIX FOR A TRAVELING WAVE TUBE Richard P. Lagerstrom, Palo Alto, and Daniel G. Dow, Altadena, Calif., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed July 23, 1959, sr. No. 829,169
'5 Claims. 01. SIS-3.6)
This invention relates to a slow-wave structure for traveling-wave amplifier tubes and more particularly to a resistance-strapped helix.
An object of the invention is to provide a travelingwave amplifier tube which has a large 3-db bandwidth and which is very nearly free from self-oscillation caused by beam interaction with a backward space harmonic of the structure having a velocity very nearly synchronous with the electron beam. By the aforementioned description of bandwidth is meant to those skilled in the art that the ratio of the frequencies at the 3-db down points on the response curve is of the order of 1.521 or 2:1.
Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Fig. 1 is a more or less schematic representation of a traveling-wave tube showing a preferred embodiment of the helix of this invention;
Fig. 2 is an enlarged axonometric view of a portion of the helix removed from the tube of Fig. l; and
Fig. 3 is a cross-section taken along the line 33 in Fig. 1.
Reference is now made to the drawing. The illustrated embodiment is a bifilar helix although the invention comprehends the use of multifilar helices made of more than two helices. The bifilar helix comprises two separate helices 2 and 4 of uniform conducting tapes of width W and thickness T. Each has the form of a helix of constant pitch p (the axial distance in which the conductor makes one complete rotation about the axis) constant pitch angle ,9 (the angle between a line tangent to an edge of one of the tapes and a plane perpendicular to the cylindrical axis of the helix), and constant mean radius a.
The helices are spaced equally from each other a distance d.
The helices are connected across the center of the structure every distance d by means of resistance straps generally indicated at 6. In the preferred illustrated embodiment the portions 8 of each strap are shown as being conducting bars and the central portion is a resistance. very small region on the axis of the helix extending, for example, a distance not greater than /6 of the strap. On the other hand, another embodiment envisions a resistance strap or lossy strap which is uniformly lossy through its length. The resistance straps can be fabricated in any one of a number of ways which would be apparent to those skilled in the art. For example, in the case of the concentrated resistance located on the axis, the conducting sections 8 can be simply solid conductors forming good electrical contact with the helix conductors and the resistor 10 can be a very thin microwave resistor known in the art or any other suitable resistor. Another way of fabricating lossy straps, adaptable either to the concentrated resistance form or the The resistance can be all concentrated in a distributed resistance form, would be by using a dielectric rod as a core, plating its ends for good electrical contact with the helix conductors and plating its length either thinly or thickly to provide resistance at the cen-. ter or uniformly along its length as desired.
The helix of the illustrated embodiment is shown in.
a conventional traveling-wave tube generally indicated at 12 which includes an electron gun 14 and a collector 16 as well as input terminals 18 and output terminals 20.
The helix is supported by dielectric rods passing through its interior but omitted from the drawing for the sake of clarity.
Operation An understanding of the operation of the present invention can perhaps best be achieved by considering first an unstrapped bifilar as a slow-wave structure. The unstrapped bifilar helix has an infinity of possible modes of propagation, two of which are important here. The symmetric mode is characterized by having the same RF voltage on both helix conductors at any given cross-section. The symmetric mode has a forward-traveling space harmonic which is useful for wideband forward-wave amplification. The antisymmetric mode is characterized by having opposite voltages on the two helix conductors at any given cross-section. The antisymmctricmode has a very strong backward space harmonic that will generally cause oscillations under the operating conditions necessary for forward amplification. It can be reasoned qualitatively that a short wire or strap connecting opposite sides of the bifilar helix will be a strong perturbation to the antisymmetric mode since it connects two points of opposite voltage, but will be only a minor perturbation to the symmetric mode since the two points connected carry the same voltage. The great advantage of the strapped bifilar helix as a slow-wave structure for traveling-wave amplifier tubes lies in the mode-selective properties of the straps. In particular, the exact center of each strap has a maximum of electric field and a zero of current in the symmetric mode, while it has a maximum of current and a zero of axial field (or voltage) in the antisymmetric mode.
Two things can be done to exploit this mode-selective current pattern. A periodicity can be introduced in one mode which does not affect the other, with the result that a mode-selective stop band is created. Or, as accomplished with this invention, the circuit can be made lossy in one mode, with negligible loss in the other. Since excess loss is wanted in the antisymmetric mode, to prevent oscillations occasioned by the strong backward space harmonic, the invention involves the insertion of series resistance which absorbs energy from the conduction current in the strap. With an ideal infinitesimal resistor at the center of each strap, the attenuation is zero in the symmetric mode because of the null in current flow at the position of the resistor. The amount of attenuation and the size of the resistor in a practical case required to suppress backward wave oscillations depend on the details of a particular tube design. The calculation of the particular resistor size can be performed using, for example, the analysis set forth in the article entitled Strapped Bifilar Helices for High-Peak-Power Traveling- Wave Tubes by Watkins and Dow, IRE Transactions on Electron Devices, January 1959, page 106, et seq.
As previously explained, one practical form of lossy strap can be represented by a strap wnich is uniformly lossy along its length instead of having its resistance concentrated on the axis of the helix. This form has a large amount of mode-selective loss, but is not completely selective.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within Patented Jan. 3, 1961;-
3 the-scope of the" appended claims, the invention may be practicedotherwise than as specifically described.
What is claimed is:
1. A slow-wave structure for use in traveling-wave tubescomprising a multifilar helix including a plurality of separate helices, each separate helix having the same constant pitch; the;- same constant pitch angle, and the same mean radius; said helices being spaced equally from each other along a common axis; and a plurality of 2. The slow-wave structure of claim 1 wherein, the,
multifilar helix is a bifilarhelix.
3. The slow-wave structure of claim 1 wherein the 4-. lossy material is concentrated in the region of the axis of the helix.
4. The slow-wave structure of claim 3 wherein the straps are spaced from each other a distance equal to half the pitch distance of each separate helix.
5. In a traveling-wave tube an electron gun, a collector for electrons, and a slow-wave structure; said slow-wave structure being; structure of claim 1'.
References Cited in the file of this patent UNITED STATES PATENTS 2,742,588 Hollenberg Apr. 17, 1956 2,768,322 Fletcher Oct. 23, 1956 2,806,975 Johnson Sept. 17, 1957 2,809,321 Johnson et a1. Oct. 8, 1957 2,840,752 Cutler et al. June 24, 1958 2,889,487 Birdsall et a1. June 2, 1959 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent Now 2,967,259 January 3 1961 Richard Pt Lagerstrom et al.
that error appears in the above numbered pat- Patent should readas It is Hereby certified ent requiring correction and that ohe said Letters corrected below.
Column 2 line 16, after "bifilar" insert helix Signed and sealed this 6th day of June 1961.
SEAL) Attest:
ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US829169A US2967259A (en) | 1959-07-23 | 1959-07-23 | Resistance-strapped helix for a traveling wave tube |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US829169A US2967259A (en) | 1959-07-23 | 1959-07-23 | Resistance-strapped helix for a traveling wave tube |
Publications (1)
Publication Number | Publication Date |
---|---|
US2967259A true US2967259A (en) | 1961-01-03 |
Family
ID=25253731
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US829169A Expired - Lifetime US2967259A (en) | 1959-07-23 | 1959-07-23 | Resistance-strapped helix for a traveling wave tube |
Country Status (1)
Country | Link |
---|---|
US (1) | US2967259A (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3200286A (en) * | 1960-12-30 | 1965-08-10 | Varian Associates | Traveling wave amplifier tube having novel stop-band means to prevent backward wave oscillations |
US3268761A (en) * | 1963-04-03 | 1966-08-23 | Hughes Aircraft Co | Traveling-wave tube slow-wave structure including multiple helices interconnected byspaced conductive plates |
US3278483A (en) * | 1962-06-01 | 1966-10-11 | Shell Oil Co | Polyolefins containing a trithiophosphite and either a salicylate or a benzophenone as stabilizer |
US4855644A (en) * | 1986-01-14 | 1989-08-08 | Nec Corporation | Crossed double helix slow-wave circuit for use in linear-beam microwave tube |
US20040065270A1 (en) * | 2002-09-17 | 2004-04-08 | Lise King | Pet stroller |
US20050166861A1 (en) * | 2002-09-17 | 2005-08-04 | Lise King | Double decker pet stroller |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2742588A (en) * | 1950-01-07 | 1956-04-17 | Bell Telephone Labor Inc | Electronic amplifier |
US2768322A (en) * | 1951-06-08 | 1956-10-23 | Bell Telephone Labor Inc | Interdigital filter circuit |
US2806975A (en) * | 1955-04-01 | 1957-09-17 | Hughes Aircraft Co | Transition from bifilar helix to waveguide for backward wave oscillator |
US2809321A (en) * | 1953-12-30 | 1957-10-08 | Hughes Aircraft Co | Traveling-wave tube |
US2840752A (en) * | 1954-12-30 | 1958-06-24 | Bell Telephone Labor Inc | Backward wave tube |
US2889487A (en) * | 1954-09-15 | 1959-06-02 | Hughes Aircraft Co | Traveling-wave tube |
-
1959
- 1959-07-23 US US829169A patent/US2967259A/en not_active Expired - Lifetime
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2742588A (en) * | 1950-01-07 | 1956-04-17 | Bell Telephone Labor Inc | Electronic amplifier |
US2768322A (en) * | 1951-06-08 | 1956-10-23 | Bell Telephone Labor Inc | Interdigital filter circuit |
US2809321A (en) * | 1953-12-30 | 1957-10-08 | Hughes Aircraft Co | Traveling-wave tube |
US2889487A (en) * | 1954-09-15 | 1959-06-02 | Hughes Aircraft Co | Traveling-wave tube |
US2840752A (en) * | 1954-12-30 | 1958-06-24 | Bell Telephone Labor Inc | Backward wave tube |
US2806975A (en) * | 1955-04-01 | 1957-09-17 | Hughes Aircraft Co | Transition from bifilar helix to waveguide for backward wave oscillator |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3200286A (en) * | 1960-12-30 | 1965-08-10 | Varian Associates | Traveling wave amplifier tube having novel stop-band means to prevent backward wave oscillations |
US3278483A (en) * | 1962-06-01 | 1966-10-11 | Shell Oil Co | Polyolefins containing a trithiophosphite and either a salicylate or a benzophenone as stabilizer |
US3268761A (en) * | 1963-04-03 | 1966-08-23 | Hughes Aircraft Co | Traveling-wave tube slow-wave structure including multiple helices interconnected byspaced conductive plates |
US4855644A (en) * | 1986-01-14 | 1989-08-08 | Nec Corporation | Crossed double helix slow-wave circuit for use in linear-beam microwave tube |
US20040065270A1 (en) * | 2002-09-17 | 2004-04-08 | Lise King | Pet stroller |
US20050166861A1 (en) * | 2002-09-17 | 2005-08-04 | Lise King | Double decker pet stroller |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US2610308A (en) | Hyperfrequency electron tube | |
US2720609A (en) | Progressive wave tubes | |
US2967259A (en) | Resistance-strapped helix for a traveling wave tube | |
US2726291A (en) | Traveling wave tube | |
US2836758A (en) | Electron discharge device | |
US3005126A (en) | Traveling-wave tubes | |
US2939035A (en) | Helical delay lines | |
US2882440A (en) | Delay lines for travelling wave tubes | |
US3571651A (en) | Log periodic electron discharge device | |
US2824257A (en) | Traveling wave tube | |
US4358704A (en) | Helix traveling wave tubes with reduced gain variation | |
US2971114A (en) | Helically-strapped multifilar helices | |
US3096457A (en) | Traveling wave tube utilizing a secondary emissive cathode | |
US2821652A (en) | Multihelix traveling wave tubes | |
US3089975A (en) | Electron discharge device | |
US2843797A (en) | Slow-wave structures | |
US3096485A (en) | Diode traveling wave parametric amplifier | |
US3972005A (en) | Ultrawide band traveling wave tube amplifier employing axially conductive circuit loading members | |
US2843776A (en) | Traveling wave tube electron gun | |
US3636402A (en) | Coupled cavity-type slow-wave structure | |
US2823333A (en) | Traveling wave tube | |
US3054017A (en) | Electron discharge devices | |
US2817037A (en) | Traveling wave electron tubes and circuits | |
US3466493A (en) | Circuit sever for ppm focused traveling wave tubes | |
US2961573A (en) | Stop bands in multifilar helices |