Abstract A crossed field microwave amplifier tube is disclosed. The amplifier employs a meander line slow wave circuit arranged for interaction with a stream of electrons to amplify signal radio frequency wave energy on the circuit to produce an amplified output signal. The meander line slow wave circuit includes a zigzag shaped conductor disposed over a ground plane member to define a meander line slow wave circuit. An insulative structure is disposed between the zig-zag conductor and the ground plane for insulatively supporting the zig-zag conductor over the ground plane. A conductive shield structure is provided which projects from the ground plane structure into the space between adjacent zig-zag portions of the zig-zag shaped conductor to decrease the capacitance between adjacent zig-zag portions of the meander line, thereby shaping the dispersion characteristic of the shielded meander line circuit to provide nearly constant phase velocity for r.f. wave energy within an ultra wide passband of the circuit. More particularly, the phase velocity within the passband of the circuit is constant to within 1 percent for 1 octave of bandwidth and constant to 1.5 percent for a 2 octave bandwidth. In a preferred embodiment, the insulative support structure is recessed into the ground plane structure to reduce the shunt capacity of the meander line to the dielectric support structure, thereby reducing the insertion loss of the circuit. In addition the conductive shield structure serves to shield the insulative support structure from sputtered cathode materials which would otherwise tend to be deposited on and to short out the insulative structure.
In a slow wave circuit, means forming a conductive ground plane structure, means forming a zig-zag-shaped conductor disposed over said ground plane to define a meander line slow wave circuit with said ground plane structure, the improvement comprising, means forming an insulative support structure disposed between said zig-zag conductor and said ground plane structure for supporting said zig-zag conductor over said ground plane structure, said insulative support structure being recessed into said ground plane structure by at least an amount equal to 20 percent of the spacing between said zig-zag conductor and said ground plane to substantially reduce the shunt capacity between said zig-zag conductor and said ground plane structure.
Claim 2
Dependent Claim
110 words
In a slow wave circuit, means forming a conductive ground plane structure, means forming a zig-zag-shaped conductor disposed over said ground plane to define a meander line slow wave circuit with said ground plane structure, the improvement comprising, means forming an insulative support structure disposed between said zig-zag conductor and said ground plane structure for supporting said zig-zag conductor over said ground plane structure, said insulative support structure being recessed into said ground plane structure by at least an amount equal to 20 percent of the spacing between said zig-zag conductor and said ground plane to substantially reduce the shunt capacity between said zig-zag conductor and said ground plane structure.
Claim 3
Dependent Claim
48 words
The apparatus of claim 1 further including a plurality of elongated conductive vane-shaped shield members projecting from said ground plane structure toward said zig-zag conductor, said vane-shaped conductors being elongated in the direction transversely of the mean direction of power flow on said meander line slow wave circuit.
Claim 4
Dependent Claim
36 words
The apparatus of claim 2 wherein said vane-shaped shield members have a free side edge portion which terminates within said zig-zag conductor in the region of space defined between adjacent zig-zag portions of said zig-zag conductor.
Claim 5
Dependent Claim
22 words
The apparatus of claim 3 wherein said zig-zag conductor is a strip line conductor having a thickness less than half its width.
Claim 6
Dependent Claim
70 words
The apparatus of claim 1 including means for projecting a stream of electrons adjacent a face of said zig-zag conductor on the side thereof faced away from said ground plane for electromagnetic interaction between the fields between adjacent zig-zag portions of said zig-zag conductor to produce amplification of wave energy on said meander line slow wave circuit, and means for extracting the amplified wave energy from said slow wave circuit.