L-c oscillator tunable by external dc voltage through phase shifted feedback network

{
  "publication_number": "US3641462A",
  "country": "US",
  "kind": "A",
  "title": "L-c oscillator tunable by external dc voltage through phase shifted feedback network",
  "abstract": "An L-C oscillator circuit is tunable as a function of the value of an externally applied DC voltage. The phase of the resonant circuit is shifted 90* by a phase shifting circuit and the amplitude of the output of the phase shifting circuit is controlled by the externally applied DC voltage. A current, the amplitude of which is proportional to the controlled output of the phase shifting circuit is generated by a current generator and fed back to the resonant circuit. As this current is shifted 90* out of phase, the capacitive element of the resonant circuit is controlled by controlling the output of the phase shifter by means of the applied DC voltage. A wave shaping circuit may be used to convert the output of the phase shifting circuit from a sinusoidal to a square wave.",
  "claims": [
    "1. An oscillator circuit comprising a resonant circuit composed of an inductance and a capacitance, phase shifting means for shifting the oscillation signal of said resonant circuit by 90*, means for applying an external DC voltage to control the amplitude of the output of said phase shifting means, a current generator generating a current the amplitude of which is proportional to the amplitude of the output of said phase shifting means as controlled by said external DC voltage and means for applying said current to said resonant circuit and thereby controlling the oscillation frequency as a function of said external DC voltage.",
    "2. An oscillator circuit according to claim 1, further comprising wave shaping circuit means connected to the output of said phase shifting means for shaping the output signal thereof.",
    "3. An oscillator circuit according to claim 2, in which said wave shaping circuit means shapes a sinusoidal wave into a square wave.",
    "4. An oscillator circuit according to claim 2, in which said wave shaping circuit comprises two Zener diodes arranged back-to-back and connected in parallel with an operational amplifier.",
    "5. An oscillator circuit according to claim 1, in which said current generator comprises a transistor having a current flow controlled by the output voltage of said phase shifting means controlled by said external DC voltage.",
    "6. An oscillator circuit according to claim 5, in which said inductance has a center tap and in which said transistor has a grounded base, a collector connected to said resonant circuit between said inductance and said capacitance and to the input of said phase shifting means, and an emitter connected through a resistor to a negative voltage supply, to the voltage controlled output of said phase shifting means and through a series connected resistor and a capacitor to said center of said inductance.",
    "7. An oscillator according to claim 1, in which said means for applying an external DC voltage to control the output of said phase shifting means comprises an external DC voltage supply, a diode, and a transistor having a base connected to said voltage supply and an emitter connected through said diode to the output of said phase shifting means."
  ],
  "cpc": [
    "H03C 3/08",
    "H03B 5/1203",
    "H03B 5/1231",
    "H03B 5/1243",
    "H03B 5/1296"
  ],
  "assignees": [
    "FUJITSU LTD"
  ],
  "filing_date": "1970-06-24",
  "publication_date": "1972-02-08",
  "grant_date": "1972-02-08",
  "priority_date": "1969-07-11",
  "application_number": "US-3641462D-A",
  "family_id": "12994816",
  "citations": [
    "US3551846A"
  ]
}