Nippon Electric Co., Ltd.

Kunio Tsutaki

Takao Kageyama

Sadanori Hamada

Hiroyuki Hashimoto

Two coupled cavity type, slow-wave circuits are separated, with a drift space section between them. An electron beam and an electromagnetic wave, which do not interact with each other, over a certain length, are in the drift space. A waveguide type non-reflective termination structure has a waveguide axis directed in the same direction as the electron beam and is coupled to the cavity, slow-wave circuits with respect to a high frequency wave disposed in the drift space section. With such a construction, a traveling wave tube is formed with a PPM focusing and with a non-reflective termination structure includes a waveguide member having a through-hole for passing an electron beam and two waveguides formed on the opposite sides of the through-hole. A lossy ceramic member is disposed within one of the two waveguides for a forwardly traveling wave and another lossy ceramic member is disposed in the other waveguide for a backwardly traveling wave. Each of the two waveguides has one end sealingly closed with tapered ceramic members of the forwardly traveling wave and for the backwardly traveling wave secured on the respective waveguide walls. During its propagation, an electromagnetic wave is perfectly absorbed by the lossy ceramic members.

Coupled cavity type traveling wave tube

A helix-type traveling wave tube delay line extends from an input side to an output side. An electron gun adjacent the input side of the helix means transmits an electronic beam to a collector adjacent the output side. An attenuator divides the helix at a location between the input side and the output side. Between the attenuator and input, the helix has a pitch (P.sub.0). Between the attenuator and the output, the pitch (P.sub.1) of the helix is greater than the pitch (P.sub.0) to form a fast velocity circuit. The pitch (P.sub.2) of a second part of the helix between the attenuator and output is less than the pitch (P.sub.0) to form a slow velocity circuit. A third part of the helix is interposed between the first and second parts to form a velocity taper section having a helical pitch which varies from the larger pitch (P.sub.1) to the smaller pitch (P.sub.2). One fairly central position in the third part of the helix has an average pitch of (P.sub.1 +P.sub.2)/2. A first length (L.sub.1) of the helix includes all of the first part and continues to the position of average pitch. A second length (L.sub.2) of the helix includes all of the second part and continues to the position of average pitch. The ratio L.sub.1 /L.sub.2 ranges from 0.6 to 2, and the ratio (2(P.sub.1 -P.sub.2)/(P.sub.1 +P.sub.2)) of the difference between pitches P.sub.1 and P.sub.2 to the average pitch ranges from 0.04 to 0.14.

Helix type traveling wave tube

A coupled cavity type traveling wave tube is provided with at least one sever termination means comprising a waveguide extending outwardly from one cavity. A ceramic type attenuator is brazed to the interior surface of one thin wall of the extending waveguide. A ceramic type plate is brazed to the exterior side of the same wall whose thickness is selected to permit the thin wall to undergo plastic deformation as a result of thermal deformation of the ceramic members. An enclosure wall is provided to surround at least the ceramic type plate. The enclosure wall is capable of maintaining a vacuum condition even in the case where the thin wall may develop a leak or hole. Two sever termination means may be provided. The sever termination means may be located on the same side of the coupled cavity type structure or they may be located on the same side and share a common dividing wall, said dividing wall being the aforementioned thin, plastically deformable wall.

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Tokyo, Japan

Kunio Tsutaki