The invention discloses a power-adjustable
backward wave oscillator. The power-adjustable
backward wave oscillator is characterized in that: by inserting upper and lower two rows of periodically complementary split-ring
resonator structure into the middle part of a cavity of rectangular
waveguide vertically, the complementary split-ring
resonator structure has a relatively higher
electric field resonant response at the slit of the opening, that is, between the horizontal branches of the two half parts, and shows the meta-material electromagnetic characteristic with a negative
dielectric constant epsilon and a negative magnetic permeability Mu; longitudinal resonant
field intensity is formed at the upper surface and lower surface of the periodically complementary split-ring
resonator structure, thus being conductive to interaction between charged particles of band-shaped
electron beams and electromagnetic
waves; and at the same time, three
electron beam channels are formed. Therefore, compared with a traditional relativism
backward wave oscillator, the power-adjustable backward wave oscillator has higher
coupling impedance and can obtain very
high power output and
electron efficiency. Besides, the structure enables one electron beam to work individually, or enables two electron beams or three electron beams to work, so that three kinds of adjustable
power output of
single beam, double beam and three-beam can be formed and then multi-band-shaped power can be adjustable.