| Summary: | 碩士 === 國立交通大學 === 電子研究所 === 82 === Variable-Frequency Oscillators (VFO's), or Voltage Con- rolled
Oscillators (VCO's), are widely used in communicationystems.
Categorically, oscillators can be divided into twolasses :(1)
tuned oscillators which provide nearly sinusoidalutputs; and
(2) multivibrators circuits which switch back andorth between
two astable states. In this thesis, oscillators implemented
with differentechniques, such as LC-sinusoidal oscillators in
the firstategory and relaxation type oscillators in the second
cate-ory, are presented and compared. Besides, a prototype of
ope-ational transconductance amplifier-capacitor (OTA-C)
typescillator is also studied and discussed. Most important of
all, we invented a novel monolithic ne-ative-resiatance LC VFO'
s for use in the microwave range. Its composed of (1) negative
impedance converter; (2) variableapacitance converter; and (3)
monolithically fabricated induc-ors. By simulation results, the
oscillator can operate at fre-uency from 1.7 GHz to 2.25 GHz.
This circuit theoreticallyxhibits the benefits of both the two
classes of oscillatorsentioned above.
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