Apparatus for increasing rf conversion efficiency of a traveling wave tube

Claim 2

In a traveling wave tube: means for forming and projecting a stream of electrons over a predetermined beam path; periodic slow wave circuit means disposed along said beam path in electromagnetic wave energy exchanging relation with the stream of electrons for producing output electromagnetic wave energy; a microwave ground plane structure disposed along said slow wave circuit and including periodic electrically conductive loading means projecting into the region between adjacent periodic elements of said periodic slow wave circuit means for decreasing the dispersiveness of said slow wave circuit means, and wherein the degree of penetration of said periodic loading means into the region between adjacent periodic elements of said slow wave circuit varies along the length of said slow wave circuit to increase the radio frequency conversion efficiency of the traveling wave tube at the low frequency end of the operating band of the tube.

Claim 3

The apparatus of claim 1 wherein the degree of said penetration of said periodic loading means increases in the mean direction of microwave output power flow on said slow wave circuit.

Claim 4

The apparatus of claim 1 wherein said slow wave circuit means comprises a topologically equivalent helix circuit selected from the class consisting of, ring and bar, meander line, double meander line, helix, cross wound helix, double ring and bar, and ladder line circuits.

Claim 5

The apparatus of claim 3 wherein said microwave ground plane structure includes an electrically conductive barrel coaxially surrounding said slow wave circuit.

Claim 6

The apparatus of claim 4 wherein said periodic electrically conductive loading means comprises an array of electrically conductive vanes projecting from said ground plane structure into the region between adjacent electrically conductive elements of said slow wave circuit means.

Claim 7

The apparatus of claim 1 including, dielectric support means interposed between said microwave ground plane structure and said slow wave circuit for supporting said slow wave circuit relative to said ground plane structure, said dielectric support means including a plurality of dielectric vane portions spaced apart along the direction of the stream of electrons with the plane of each of said vanes being generally transversely disposed of the beam path, and wherein said periodic electrically conductive loading means includes an array of electrically conductive vane members with one of said loading members being interposed between adjacent ones of said dielectric vane portions, said loading vanes being electrically coupled for microwave energy to said microwave ground plane structure to provide a microwave ground disposed between periodic elements of said microwave circuit.

Claim 8

The apparatus of claim 6 wherein each of said electrically conductive loading vanes has a root portion adjacenT said microwave ground plane structure and a tip portion adjacent said slow wave circuit, and wherein said tip portions of said loading vanes are closer to said slow wave circuit in a region of said vane loaded slow wave circuit that is displaced in the direction of microwave output power flow on said circuit from another region of said vane loaded slow wave circuit to increase the microwave conversion efficiency of the traveling wave tube.

Claim 9

The apparatus of claim 6 including, means for electrically isolating at least a portion of said electrically conductive loading vanes for d.c. operating potential relative to an upstream portion of said microwave ground plane structure to permit application of an independent operating potential to said electrically isolated portion of said loading vanes relative to the operating d.c. potential of said upstream portion of said ground plane structure for increasing the microwave conversion efficiency of the traveling wave tube.

Claim 10

In a traveling wave tube: means for forming and projecting a stream of electrons over a predetermined beam path; periodic slow wave circuit means disposed along said beam path in electromagnetic wave energy exchanging relation with the stream of electrons for producing output electromagnetic wave energy; means for providing a microwave ground plane structure disposed along said slow wave circuit and including periodic electrically conductive loading means projecting into the region between adjacent periodic elements of said periodic slow wave circuit means for decreasing the dispersiveness of said slow wave circuit means, means for electrically isolating at least a portion of said periodic loading means for d.c. operating potential relative to an upstream portion of said ground plane structure to permit application of an independent operating potential to said electrically isolated portion of said loading means relative to the operating d.c. potential of said upstream portion of said ground plane structure for increasing the microwave conversion efficiency of the traveling wave tube.

Claim 11

In a traveling wave tube: means for forming and projecting a stream of electrons over a predetermined beam path; periodic slow wave circuit means disposed along said beam path in electromagnetic wave energy exchanging relation with the stream of electrons for producing output electromagnetic wave energy; means for providing a microwave ground plane structure disposed along said slow wave circuit and including periodic electrically conductive loading means projecting into the region between adjacent periodic elements of said periodic slow wave circuit means for decreasing the dispersiveness of said slow wave circuit means, means for electrically isolating at least a portion of said periodic loading means for d.c. operating potential relative to an upstream portion of said ground plane structure to permit application of an independent operating potential to said electrically isolated portion of said loading means relative to the operating d.c. potential of said upstream portion of said ground plane structure for increasing the microwave conversion efficiency of the traveling wave tube.

Claim 12

The apparatus of claim 9 wherein each of said electrically conductive loading means has a root portion adjacent said microwave ground plane structure and a tip portion adjacent said slow wave circuit, and wherein said means for electrically isolating said upstream portion of said ground plane structure from said downstream portion of said loading means includes a capacitor means interposed between the root portions of said downstream electrically conductive loading means members and an adjacent portion of said ground plane structure.

Claim 13

The apparatus of claim 1 wherein the degree of penetration of said periodic microwave ground plane structure increases at the output end of said slow wave circuit.

Claim 14

The apparatus of claim 9 wherein said downstream electrically isolated portion of said loading means is disposed at the output end of said slow wave circuit means.