Coalesced mode coupled cavity slow wave tube

Claim 1

In a microwave tube; means for projecting a beam of electrons over an elongated beam path; slow wave circuit means disposed along the beam path in electromagnetic energy exchanging relation with the beam; said slow wave circuit means including, an array of cavity resonators arranged along the beam path for successive electromagnetic interaction with the beam, adjacent ones of said cavity resonator having common end walls, an array of wave energy coupling slot means disposed in the common end walls of said cavity resonators for wave energy coupling together the array of cavity resonators to define a slow wave circuiT having a cavity mode passband of frequencies associated with the coupled cavities and a slot mode passband of frequencies centered at a higher frequency than the cavity mode passband and associated with the array of slots, said slots being dimensioned to have a resonant frequency at substantially the upper band edge frequency of the cavity mode and the low frequency band edge of the slot mode for increasing the width of the passband of the composite slow wave circuit, THE IMPROVEMENT WHEREIN, said coupling slots are comprised of at least two sets of slots, each set of said slots being disposed in opposite end walls of each of said cavities with their geometric centers lying on one side of the beam path and falling substantially in a plane defined by the axis of the beam path and the centers of said coupling slots, whereby the total slot impedance for each coupled cavity is substantially reduced for substantially increasing the operating bandwidth of the tube compared to a tube using only one set of similar coupling slots.