Abstract
A device for converting microwave power into either
DC power or low-frequency AC power has been investigated both theoretically and
experimentally. Rotational
energy is stored in an electron beam by a Cuccia
coupler, then converted to longitudinal energy by interaction with a
space-dependent DC magnetic field, and finally recovered as electric energy
by a depressed collector. A simple kinematic
analysis demonstrates that the Cuccia coupler can
convert large amounts of microwave power into electron beam rotation. Limits
on the electric field strength and asynchronism
between signal frequency and cyclotron frequency are established for both
classical and relativistic coupler operation. Efficiency analyses of the
process of conversion from orbital energy to DC electric energy, both
classical and relativistic, indicate that the efficiency exceeds 95 per cent
for a particular range of operating conditions. As an AC power supply, the
device responds to the modulating frequency of the signal. Theory predicts
near-negligible harmonic distortion as well as flatness of frequency response
from DC to about 1.0 MHz modulating frequency. Four tubes and a prototype
(with "artificial" coupler) were tested experimentally. The first
three tubes exhibited efficiencies up to 22 per cent, being hindered by
reflection of electrons into the coupler. Certain design changes were tested
on the prototype, where efficiencies from 36 per cent to 75 per cent were
obtained. Incorporating these design changes into the fourth tube yielded
measured efficiencies of up to 34 per cent, or when
corrected to disregard unusually large cavity losses, up to 59 per cent.
Experimental tests of the tube as an AC converter yielded excellent frequency
response and about 20 per cent second-harmonic distortion. It is concluded
that the theoretical foundation of efficiency predictions has thus far been
based on too-optimistic assumptions.
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