Inductive output tube with multistage depressed collector electrodes providing a near-constant efficiency

A method for amplifying a UHF frequency signal having a high ratio of peak to average power comprising the steps of:

• accelerating an electron beam from an electron gun assembly having a cathode and an anode spaced therefrom by application of a relatively high voltage potential between said cathode and said anode;
• density modulating said electron beam by application of said UHF frequency signal to a control grid disposed between said cathode and said anode;
• electrically biasing said control grid relative to said cathode to preclude transmission of said electron beam during the negative half cycle of said UHF frequency signal;
• passing said density modulated beam across a gap to induce an amplified UHF signal into a cavity coupled to said gap;
• extracting said amplified UHF signal from said cavity;
• and
• collecting the electrons of said beam remaining after transit across said gap on a plurality of electrode stages, each stage respectively having electric potential applied thereto ranging between ground and said cathode potential, said respective electrode stage potentials being selected to have corresponding voltage values such as to provide near-constant high efficiency across a power range of said UHF signal.

A linear amplifier for amplifying a UHF frequency signal having a high ratio of peak to average power, comprising:

• an electron gun assembly having a cathode and an anode spaced therefrom, said cathode being coupled to a voltage source providing said cathode with a high voltage potential relative to said anode, said cathode providing an electron beam in response to said high voltage potential;
• a control grid spaced between said cathode and anode, and means for density modulating said electron beam by application of said UHF frequency signal to said control grid, said control grid being coupled to a bias voltage source providing said grid with a bias voltage relative to said cathode to preclude transmission of said electron beam during the negative half cycle of said UHF frequency signal;
• a drift tube spaced from said electron gun and surrounding said beam and including a first portion and a second portion, a gap being defined between said first and second portions;
• an inductive output cavity coupled with said drift tube, said density modulated beam passing across said gap and inducing an amplified UHF frequency signal into said cavity;
• means, disposed within said cavity, for extracting said amplified UHF frequency signal from said inductive output cavity;
• and
• a multistage depressed collector spaced from said drift tube, the electrons of said beam passing into said collector after transit across said gap and being collected on a plurality of electrode stages therein, each stage respectively having electric potential applied thereto ranging between ground and said cathode potential, wherein said respective electric potential applied to each one of said electrode stages precludes collection of said electrons having a potential equal to that of said anode, said respective electrode stage potentials having corresponding voltage values such as to provide a near-constant level of efficiency across a power range of said UHF frequency signal.