Cost-effective, simple, low-noise, crossed-field devices such as
a microwave magnetron, a microwave oven utilizing same, and crossed-field amplifier
utilize an azimuthally varying, axial magnetic field. The magnetic configuration
reduces and eliminates microwave and radio frequency noise. This microwave noise
is present near the carrier frequency and as sidebands, far separated from the
carrier. The device utilizes azimuthally-varying, axial, magnetic field perturbations.
At least one permanent perturbing magnet having an azimuthally-varying magnetic
field impressed thereupon causes the axial magnetic field to vary azimuthally in
the magnetron and completely eliminates the microwave noise and unwanted frequencies.
Preferably, the number of axial magnetic field perturbations is based on the number
of cavities of the magnetron.
