DOUBLE OCTAVE BROADBAND TRAVELING WAVE TUBE

• US 3,716,745 A
• Filed: 07/22/1971
• Issued: 02/13/1973
• Est. Priority Date: 07/22/1971
• Status: Expired due to Term

• Current Assignee: Robert Matthews Phillips
• Original Assignee: Robert Matthews Phillips
• Inventors: Phillips, Robert Matthews
• Primary Examiner(s): Lieberman, Eli
• Assistant Examiner(s): Chatmon, Jr., Saxfield
• Application Number:
  US05/165,263
• Time in Patent Office: 572 Days
• Field of Search: 315/3.6,3.5 330/43
• US Class Current: 315/3.6
• CPC Class Codes: H01J 23/27 Helix-derived slow-wave structures
• CPC Class Codes: H01J 25/38 the forward travelling wave being utilised

Abstract

An O-type traveling wave tube of the invention includes a slow wave structure having a broad band characteristic over a predetermined range of frequencies and in some cases is capable of broad band operation over a double octave of frequencies. In this the slow wave structure comprises a combination of a substantially nondispersive delay line, such as a helix, with a substantially dispersive delay line, such as a ring loop section. The ring loop sections complement in gain the gain drop off characteristic of the helix at the edges of the frequency band at which the gain from the helix circuit tapers off. In this the overall gain of the traveling wave tube is enhanced and extended over a frequency spectrum greater than that which is available solely with the helix construction.

Claims

1. An O-type traveling wave tube having a uniform level of gain over at least a one octave frequency range which comprises:

a cathode for providing a source of electrons, a collector electrode spaced from said cathode for collecting electrons, an accelerator electrode spaced in between said cathode and collector for accelerating electrons from said cathode for travel through an interaction region defined in the space between said accelerator electrode and said collector, and slow wave structure means located within said interaction region, said slow wave structure including an input for receiving signals to be amplified and an output for passing signals amplified as a result of interaction in said interaction region to a load; and

said slow wave structure including;

first and second substantially nondispersive delay lines spaced apart in said interaction region, said first and second delay lines possessing an overall gain characteristic which is of a substantially uniform level over a first predetermined range of frequencies and which decreases to lesser levels of gain at other frequencies above and below said first range;

said input being coupled to the end of said first non-dispersive delay line most proximate said cathode and said output being coupled to an end of said second nondispersive delay line most proximate said collector;

a first substantially dispersive delay line section spaced from and located in the space between said first and second delay lines, said dispersive delay line section having a second predetermined gain characteristic effectivE to provide gain substantially only in an increment of frequencies adjacent and outside said first predetermined range for complementing the gain characteristic of said first and second delay lines in an increment of frequencies adjacent and outside said first predetermined range without providing substantially any gain within said predetermined frequency range to thereby extend said uniform level of gain over an additional increment of frequencies adjacent and outside said first predetermined range;

support means for supporting all said delay lines in said interaction region; and

microwave loss material located on said support means at those locations thereon corresponding to the locations of the opposed ends of said nondispersive and dispersive delay lines for absorbing microwave energy propagating to said opposed ends.

2. The invention as defined in claim 1 wherein each of said first and second delay lines comprises further:

elongated helixes of electrically conductive material.

3. The invention as defined in claim 1 wherein said substantially dispersive delay line comprises an equivalent contrawound helix assembly.

4. The invention as defined in claim 3 wherein said equivalent contrawound helix assembly comprises further a ring loop line.

5. The invention as defined in claim 2 wherein said substantially dispersive delay line comprises a ring loop assembly.

6. A broad band double octave O-type traveling wave tube of the type having a metal envelope containing a cathode and accelerator means for generating an electron beam of a predetermined velocity for travel into an interaction region and a slow wave structure located within said interaction region;

said slow wave structure comprising a first section of helix having an end most proximate said cathode connnected to a microwave input coupling means and an end most remote from said cathode connected electrically in common with said envelope;

a second section of helix located in said interaction region spaced from said first section of helix;

said second helix having its end most remote from said cathode connected to a microwave output coupling means and having its end most proximate said cathode connected electrically in common with said envelope;

a ring-loop type slow wave circuit of a predetermined length;

said ring-loop structure comprising a plurality of spaced rings of metallic material in which adjacent rings are coupled together electrically by short metal loops;

said ring-loop section being located within said interaction region in between said first and second helix sections and having at least one end thereof connected electrically in common with said envelope;

said first and second helix sections capable of providing a relatively flat gain characteristic over a predetermined range of frequencies, designated omega 1 to omega 2, and having a decreasing gain characteristic in an adjacent upper range of frequencies, omega 2 to omega u, and in a lower range of frequencies, omega 1 to omega , where omega u >

omega 2 and omega <

omega 1, and said ring-loop structure including a first plurality of rings spaced apart a first predetermined distance and a second plurality of rings spaced apart a second predetermined distance different from said first predetermined distance and having a gain characteristic effective substantially only in the region of frequencies omega 2 to omega u and omega 1 to omega and which gain characteristic complements that of said helix structure substantially only within the region of frequencies of omega 2 to omega u and omega 1 to omega to extend said relatively flat gain characteristic for said traveling wave tube over the larger frequency range of omega to omega u.

7. An O-type traveling wave tube of the type containing a source of electrons;

means for forming said electrons into an electron beam for travel into an interaction reGion;

a collector electrode for collecting electrons traveling from said interaction region, input coupling means, output coupling means, a slow wave structure located within said interaction region for receiving signals, omega , to be amplified at one end and providing amplified signals at an output end; and

said tube having a gain characteristic of a predetermined uniform level over a predetermined range of frequencies, between omega a and omega b, where omega a is a predetermined first frequency and omega b is a predetermined second frequency in said range of frequencies;

the improvement thereto wherein said slow wave structure comprises;

first substantially nondispersive slow wave structure means substantially nondispersive over the frequency range of omega b to omega i, where omega i is a third predetermined frequency within the range of omega a to omega b, and having a substantially uniform flat gain characteristic over said frequency range omega b to omega i and a gain drop off at frequencies between omega i and omega a;

said first nondispersive slow wave structure comprising two spaced helix sections and said input means coupled to the input end of said first helix section and said output means coupled to the output end of said second helix section; and

second substantially dispersive slow wave structure means disposed between said two spaced helix sections;

said dispersive slow wave structure means having a gain characteristic limited to a narrow range of frequencies substantially less than the difference omega b-omega a and said gain characteristic of said second slow wave structure being substantially complementary with said gain characteristic of said first slow wave structure means in the frequency range between omega i and omega a to provide in combination with said nondispersive slow wave structure a uniform gain characteristic over the frequency range of omega a to omega b.

8. The invention as defined in claim 7 wherein omega b >

omega i >

omega a.

9. The invention as defined in claim 7 wherein omega b <

omega i <

omega a.

10. The invention as defined in claim 8 wherein said second slow wave structure comprises a ring loop line.

11. An O-type traveling wave tube of the type which includes:

a source of electrons, means for forming electrons from said source into an electron beam for travel through an interaction region, a collector electrode for collecting electrons traveling from said interaction region, and a slow wave structure in said interaction region for receiving signals to be amplified by interaction with said electron beam in said interaction region, said tube having a gain characteristic of a predetermined flat level over the range of frequencies omega to omega u, where omega is the lower frequency of the range and omega u is the upper frequency of the range, the improvement wherein said slow wave structure comprises;

first nondispersive slow wave structure means substantially nondispersive over the frequency range of omega x to omega y and having a substantially flat gain characteristic over the frequency range omega x to omega y and a gain drop off at frequencies greater than omega y and lesser than omega x, where omega <

omega x <

omega y <

omega u;

said first nondispersive slow wave structure including;

a first helix section, and a second helix section, said second helix section being spaced from said first helix section; and

second dispersive slow wave structure means having a relative peaked gain characteristic and effective to provide gain substantially only within the range of frequencies between omega and omega x and between omega u and omega y, said gain characteristic of said second slow wave structure means beinG substantially complementary with said gain characteristic of said first slow wave structure means in the range of frequencies between omega u and omega y and in the range of frequencies between omega and omega x;

said second dispersive slow wave structure means being located in between and spaced from said first and second helix sections; and

microwave energy input coupling means coupled to one end of said first helix section and microwave energy output coupling means coupled to one end of said second helix section.

12. The invention as defined in claim 11 wherein said second dispersive slow wave structure comprises a ring-loop line.

13. The invention as defined in claim 11 wherein said second slow wave structure comprises a ring-loop line.

14. The invention as defined in claim 11 wherein said second slow wave structure means comprises a member of the contra-wound helix family of circuits.

15. The invention as defined in claim 14 wherein said member of said contrawound helix family of circuits comprises further a ring loop line.

16. An O-type traveling wave tube which comprises:

a cathode for providing a source of electrons;

a collector electrode spaced from said cathode for collecting electrons;

an accelerator electrode spaced in between said cathode and collector for accelerating electrons from said cathode for travel through an interaction region defined in the space between said accelerator electrode and said collector; and

slow wave structure means located within said interaction region, said slow wave structure including an input at one end for receiving signals to be amplified and an output at its other end for passing signals amplified as a result of interaction in said interaction region to a load, said slow wave structure including;

first and second substantially nondispersive delay lines spaced apart in said interaction region, each of which comprises an elongated helix of electrically conductive material, said first and second delay lines possessing an overall gain characteristic which is of a substantially uniform level over a first predetermined range of frequencies and which decreases to lesser levels of gain at other frequencies above and below said first range;

a first substantially dispersive delay line section spaced from and located in the space between said first and second delay lines, said substantially dispersive delay line comprising a ring-loop assembly having a first portion with a relatively wide spacing between rings for providing gain at high frequencies, and a second portion with a relatively small spacing between rings for providing gain at low frequencies, said dispersive delay line section having a gain characteristic which complements the gain characteristic of said first and second delay lines in an increment of frequencies adjacent and outside said first range to extend said uniform level of gain for an additional increment of frequencies adjacent and outside said first predetermined range;

support means for supporting all said delay lines in said interaction region; and

microwave loss material located on said support means at those locations thereon corresponding to that of the opposed ends of each said delay lines for absorbing microwave energy propagating to said ends.

17. The invention as defined in claim 16 wherein the pitch of each of said first and second of said ring loop structures are tapered to provide a tailored gain characteristic.