OSCILLATOR CIRCUIT WITH SERIES RESONANT COUPLING TO MIXER

• US 3,573,631 A
• Filed: 08/30/1968
• Issued: 04/06/1971
• Est. Priority Date: 08/30/1968
• Status: Expired due to Term

• Current Assignee: RCA Corporation
• Original Assignee: David J. Carlson
• Inventors: Carlson, David J.
• Application Number:
  US04/756,620
• Time in Patent Office: 949 Days
• US Class Current: 455/195.1
• CPC Class Codes: H03B 2200/004 including a variable capacitance, e.g. a varicap, a varactor or a variable capacitance of a diode or transistor
• CPC Class Codes: H03B 2201/0208 the means being an element with a variable capacitance, e.g. capacitance diode
• CPC Class Codes: H03B 5/1203 the amplifier being a single transistor
• CPC Class Codes: H03B 5/1231 the amplifier comprising one or more bipolar transistors
• CPC Class Codes: H03B 5/1243 the means comprising voltage variable capacitance diodes

Abstract

An oscillator circuit tuned by a voltage dependent variable capacitance diode is coupled to a mixer stage by a wide band injection circuit which includes a series connected inductor and capacitor adapted to series resonate at a frequency within the oscillator tuning range. A resistor interconnects the voltage dependent variable capacitance diode and a tuning bias potential supply. The resistor is of a value to cause the tuning of the oscillator circuit to track the tuning of the other circuits controlled by the bias supply.

Claims

1. In a television tuner tunable over a desired band of frequencies and including a mixer stage, an oscillator comprising:

a transistor having a first electrode, a second electrode, and a control electrode;

a source of operating potential;

circuit means interconnecting the first electrode and the control electrode of said transistor with said source of operating potential;

a source of tuning bias potential;

tunable circuit means coupled to the first electrode of said transistor, including a voltage dependent variable capacitance diode which is conductive over a portion of said desired band of frequencies;

a resistor interconnecting said voltage dependent variable capacitance diode and said tuning bias potential such that when said diode is conductive, a voltage is established across said resistor of a polarity that opposes the tuning bias potential; and

an injection circuit interconnecting said mixer stage and said oscillator including a serially connected capacitor and inductor series resonant at a frequency within said desired band of frequencies.

2. In a television tuner tunable over a desired band of frequencies and including a mixer stage, an oscillator comprising:

an oscillator transistor;

a source of operating potential;

circuit means interconnecting said transistor with said source of operating potential;

tunable circuit means coupled to said transistor; and

an injection circuit interconnecting said mixer stage and said oscillator including a serially connected capacitor and inductor series resonant at a frequency within said desired band of frequencies.

3. An oscillator as defined in claim 2 wherein said series connected capacitor and inductor are series resonant at a frequency within a band of frequencies ranging from 88 MHz to 174 MHz.

4. An oscillator as defined claim 2 wherein said series connected capacitor and inductor are series resonant at an unused frequency within said band of desired frequencies.

5. An oscillator as defined in claim 4 further including a capacitor connected between said injection circuit and a point of fixed reference potential, said capacitor and said injection circuit forming a series resonant circuit between said mixer stage and said point of fixed reference potential which is resonant at a frequency above the frequency at which said injection circuit is series resonant.

6. In a television tuner tunable over a desired band of frequencies and including a mixer stage, an oscillator comprising:

a transistor having a first electrode, a second electrode and a control electrode;

a source of operating potential;

circuit means interconnecting the first electrode and the control electrode of said transistor with said source of operating potential;

a source of tuning bias potential;

tunable circuit means coupled to the first electrode of said transistor, including a voltage dependent variable capacitance diode;

means interconnecting said voltage dependent variable capacitance diode and said tuning bias potential; and

an injection circuit iNterconnecting said mixer stage and the second electrode of said transistor, said injection circuit including a serially connected capacitor and inductor series resonant at a frequency within a band of frequencies ranging from 88 MHz to 174 MHz.

7. An oscillator as defined in claim 6 further including a capacitor connected between said injection circuit and a point of fixed reference potential, said capacitor and said injection circuit forming a series resonant trap circuit between said mixer stage and said point of fixed reference potential which is series resonant at a frequency above the frequency at which said injection circuit is series resonant.

8. In a television tuner tunable over a desired band of frequencies and including a mixer stage, an oscillator comprising:

a transistor having an emitter electrode, a collector electrode and a base electrode;

a source of operating potential;

circuit means interconnecting the collector electrode and the base electrode of said transistor with said source of operating potential;

tunable circuit means coupled to the collector electrode of said transistor; and

an injection circuit interconnecting said mixer stage and the emitter electrode of said transistor, said injection circuit including a serially connected capacitor and inductor series resonant at a frequency within a band of frequencies ranging from 88 MHz to 174 MHz.

9. An oscillator as defined in claim 8 wherein said tunable circuit means includes a voltage dependent variable capacitance device.