Patent ID: 6255913
Filing Date: 2001-07-03
Classification: H03B

Abstract:
A tunable variable frequency oscillator (VFO) circuit operable for selectively adjusting the oscillating frequency of the circuit to a frequency value within a range extending from below to above a set frequency of the circuit, comprising:a tank inductor having an inductance value L;a tank capacitor having a capacitance value C and connected in parallel with said tank inductor;a varactor connected in parallel with said tank capacitor for selectively increasing an overall capacitance of said VFO circuit to thereby decrease the oscillating frequency of the circuit below the set frequency; anda second inductor electromagnetically coupled with said tank inductor and selectively conductable to decrease an overall inductance of said VFO circuit without causing any parasitic capacitance effect to said VFO circuit and thereby increase the oscillating frequency of said VFO circuit above the set frequency.