CAPACITIVE-DEGENERATION DOUBLE CROSS-COUPLED VOLTAGE-CONTROLLED OSCILLATOR

• US 20090134944A1
• Filed: 05/02/2008
• Published: 05/28/2009
• Est. Priority Date: 11/27/2007
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Lee, Sang Heung, Lee, Ja Yol, Yu, Hyun Kyu, Kim, Hae Cheon
• Granted Patent: US 7,852,165 B2
• Time in Patent Office: Days
• US Class Current: 331/48
• CPC Class Codes: H03B 5/1212 the amplifier comprising a pair of transistors, wherein an output terminal of each being connected to an input terminal of the other, e.g. a cross coupled pair
• CPC Class Codes: H03B 5/1215 the current source or degeneration circuit being in common to both transistors of the pair, e.g. a cross-coupled long-tailed pair
• CPC Class Codes: H03B 5/1221 the amplifier comprising multiple amplification stages connected in cascade
• CPC Class Codes: H03B 5/1231 the amplifier comprising one or more bipolar transistors
• CPC Class Codes: H03B 5/1253 the transistors being field-effect transistors

Abstract

A capacitive-degeneration double cross-coupled voltage-controlled oscillator is provided. The capacitive-degeneration double cross-coupled voltage-controlled oscillator includes a main cross-coupled oscillating unit including an oscillation transistor pair cross-coupled to first and second output nodes of a resonating unit to perform an oscillation operation; and an auxiliary cross-coupled oscillating unit including a positive-feedback transistor pair cross-coupled to the first and second output nodes and the transistor pair of the main cross-coupled oscillating unit and a degeneration capacitance connected between emitters of the positive-feedback transistor pair so as to increase a negative resistance of the main cross-coupled oscillating unit. Accordingly, it is possible to increase a maximum attainable oscillation frequency and to decrease an input capacitance.

Claims

1. A voltage-controlled oscillator comprising:

a main cross-coupled oscillating unit including an oscillation transistor pair cross-coupled to first and second output nodes of a resonating unit to perform an oscillation operation; and

an auxiliary cross-coupled oscillating unit including a positive-feedback transistor pair cross-coupled to the first and second output nodes and the oscillation transistor pair and a degeneration capacitance connected between emitters of the positive-feedback transistor pair so as to increase a negative resistance of the main cross-coupled oscillating unit.

2. The voltage-controlled oscillator of claim 1, wherein the main cross-coupled oscillating unit comprises:

first and second transistors of which bases are connected to the respective first and second output nodes of the resonating unit and of which collectors and bases are cross-coupled to each other; and

a second current source connected to emitters of the first and second transistors.

3. The voltage-controlled oscillator of claim 2, wherein the auxiliary cross-coupled oscillating unit comprises:

a third transistor having a collector connected to the base of the first transistor and a base connected to the emitter of the second transistor;

a fourth transistor having a collector connected to the base of the second transistor and a base connected to the emitter of the first transistor;

a degeneration capacitance connected between emitters of the third and fourth transistors; and

a first current source connected to emitters of the third and fourth transistors.

4. The voltage-controlled oscillator of claim 2, wherein the resonating unit comprises:

first and second inductors commonly connected to a supply voltage; and

first and second NMOS varactors of which sources and drains are commonly connected to a tuning voltage and of which gates are connected to the respective first and second inductors.

5. The voltage-controlled oscillator of claim 1, wherein the main cross-coupled oscillating unit comprises:

first and second coupling capacitances connected to the respective first and second output nodes;

a first transistor having a base connected to the second output node of the resonating unit and a collector connected to a supply voltage;

a second transistor having a base connected to the first output node of the resonating unit and a collector connected to the supply voltage; and

a second current source connected to emitters of the first and second transistors.

6. The voltage-controlled oscillator of claim 5, further comprising first and second load impedances connected between the supply voltage and the collector of the first transistor and between the supply voltage and the collector of the second transistor, respectively.

7. The voltage-controlled oscillator of claim 5, wherein the auxiliary cross-coupled oscillating unit comprises:

a third transistor having a collector commonly connected to the base of the first transistor and the second output node and a base connected to the emitter of the second transistor;

a fourth transistor having a collector commonly connected to the base of the -second transistor and the first output node and a base connected to the emitter of the first transistor;

a degeneration capacitance connected between emitters of the third and fourth transistors; and

a first current source connected to emitters of the third and fourth transistors.

8. The voltage-controlled oscillator of claim 5, wherein the resonating unit comprises:

a base bias resistance connected to a base voltage;

a center-tapped inductor connected to the base bias resistance; and

a varactor capacitance connected in parallel to the center-tapped inductor.

9. A voltage-controlled oscillator comprising:

a main cross-coupled oscillating unit including an oscillation transistor pair cross-coupled to first and second output nodes of a resonating unit to perform an oscillation operation; and

an auxiliary cross-coupled oscillating unit including a positive-feedback transistor pair cross-coupled to the first and second output nodes and the transistor pair of the main cross-coupled oscillating unit so as to increase a negative resistance of the main cross-coupled oscillating unit.

10. The voltage-controlled oscillator of claim 9, wherein the main cross-coupled oscillating unit comprises:

first and second transistors of which bases are connected to the respective first and second output nodes, and of which collectors and bases are cross-coupled to each other; and

a second current source connected to emitters of the first and second transistors.

11. The voltage-controlled oscillator of claim 10, wherein the auxiliary cross-coupled oscillating unit comprises:

a third transistor having a collector connected to the base of the first transistor and a base connected to the emitter of the second transistor;

a fourth transistor having a collector connected to the base of the second transistor and a base connected to the emitter of the first transistor; and

a first current source commonly connected to emitters of the third and fourth transistors.

12. The voltage-controlled oscillator of claim 10, wherein the auxiliary cross-coupled oscillating unit comprises:

a third transistor having a collector connected to the base of the first transistor and a base connected to the emitter of the second transistor;

a fourth transistor having a collector connected to the base of the second transistor and a base connected to the emitter of the first transistor; and

first current sources connected to the emitters of the third and fourth transistors, respectively.