Low impedance grid-anode interaction region for an inductive output

Abstract

A linear beam amplification device includes an axially centered electron emitting cathode and an anode spaced therefrom. The cathode provides an electron beam in response to a relatively high voltage potential defined between the cathode and the anode. A control grid is spaced between the cathode and anode for modulating the electron beam in accordance with an input signal. A signal input assembly of the linear beam amplification device comprises an axial input cavity into which the input signal is inductively coupled. The grid-cathode region is electrically connected to the input cavity. A low impedance grid-anode cavity is disposed coaxially with the input cavity and is in electrical communication with an interaction region defined between the grid and the anode. The low impedance of the grid-anode cavity is provided by constructing the cavity of a material having a relatively high surface resistivity, such as iron. The high surface resistivity tends to reduce the Q (quality factor) of the grid-anode cavity, which also reduces the impedance of the grid-anode cavity. Alternatively, the grid-anode cavity may be tuned to define a transmission line having an electrical length approximately equal to n.lambda./4, where .lambda. is the wavelength of the input RF signal, and n is an even integer.