Voltage-controlled oscillator decreasing phase noise
A voltage-controlled oscillator includes an LC bank, a negative resistor circuit, a DC block, an AC block including a source resistor, and a first bias circuit controlled by a junction node of a first and second transistor, wherein the first bias circuit provides a first feedback voltage to a first control node, and maintains a voltage at the junction node of the first and second transistors, and a second bias circuit controlled by the junction node, wherein the second bias circuit provides a second feedback voltage to a second control node and maintains a voltage at the junction node.
1. A voltage-controlled oscillator comprising:
an inductor-capacitor bank supplied with a power source voltage and a control voltage, wherein the inductor-capacitor bank oscillates first and second oscillation nodes from which first and second oscillation signals are generated, respectively;
a negative resistor circuit including first and second control nodes and first and second transistors which provide negative resistance to the inductor-capacitor bank, wherein the negative resistor circuit maintains the oscillation of the first and second oscillation nodes;
a direct current block which couples the second oscillation node with the first control node and couples the first oscillation node with the second control node, wherein the first control node controls the first transistor and the second control node controls the second transistor;
an alternating current block including a source resistor disposed between a junction node, which is connected to the first and second transistors, and a ground voltage;
a first bias circuit controlled by the junction node, wherein the first bias circuit provides a first feedback voltage to the first control node and maintains a voltage at the junction node of the first and second transistors; and
a second bias circuit controlled by the junction node, wherein the second bias circuit provides a second feedback voltage to the second control node and maintains a voltage at the junction node of the first and second transistors.
2. The voltage-controlled oscillator as set forth in claim 1 , wherein the inductor-capacitor bank comprises:
a first inductor disposed between the first oscillation node and the power source voltage;
a first oscillation capacitor disposed between the first oscillation node and the control voltage;
a second inductor disposed between the second oscillation node and the power source voltage; and
a second oscillation capacitor disposed between the second oscillation node and the control voltage.
3. The voltage-controlled oscillator as set forth in claim 1 , wherein the first and second transistors are n-channel metal-oxide-semiconductor transistors,
wherein the first control node is connected to a gate of the first transistor and the second control node is connected to a gate of the second transistor.
4. The voltage-controlled oscillator as set forth in claim 1 , wherein the direct current block comprises:
a first direct current block capacitor disposed between the second control node and the first oscillation node; and
a second direct current block capacitor disposed between the first control node and the second oscillation node.
5. The voltage-controlled oscillator as set forth in claim 1 , wherein the first bias circuit comprises:
a first voltage supply disposed between the power source voltage and a first common connection node electrically connected to the first control node; and
a third transistor disposed between the first common connection node and the ground voltage and controlled by a voltage level of the junction node, and
wherein the second bias circuit comprises:
a second voltage supply disposed between the power source voltage and a second common connection node electrically connected to the second control node; and
a fourth transistor disposed between the second common connection node and the ground voltage and controlled by a voltage level of the junction node.
6. The voltage-controlled oscillator as set forth in claim 5 , wherein the third and fourth transistors are n-channel metal-oxide-semiconductor transistors,
wherein gates of the third and fourth transistors are coupled to the junction node.
7. The voltage-controlled oscillator as set forth in claim 1 , wherein the frequencies of the first and second oscillation signals are regulated by the control voltage.
8. A voltage-controlled oscillator comprising:
an inductor-capacitor bank supplied with a power source voltage and a control voltage, wherein the inductor-capacitor bank oscillates first and second oscillation nodes from which first and second oscillation signals are generated, respectively;
a negative resistor circuit including first and second control nodes and first and second transistors which provide negative resistance to the inductor-capacitor bank, wherein the negative resistor circuit maintains the oscillation of the first and second oscillation nodes;
a direct current block which couples the second oscillation node with the first control node and couples the first oscillation node with the second control node, wherein the first control node controls the first transistor and the second control node controls the second transistor;
an alternating current block including a source resistor disposed between a junction node, which is connected to the first and second transistors, and a ground voltage; and
a bias circuit controlled by the junction node, wherein the first bias circuit provides first and second feedback voltages to the first and second control nodes, respectively, and maintains a voltage at the junction node of the first and second transistors.
9. The voltage-controlled oscillator as set forth in claim 8 , wherein the inductor-capacitor bank comprises:
a first inductor disposed between the first oscillation node and the power source voltage;
a first oscillation capacitor disposed between the first oscillation node and the control voltage;
a second inductor disposed between the second oscillation node and the power source voltage; and
a second oscillation capacitor disposed between the second oscillation node and the control voltage.
10. The voltage-controlled oscillator as set forth in claim 8 , wherein the first and second transistors are n-channel metal-oxide-semiconductor transistors,
wherein the first control node is connected to a gate of the first transistor and the second control node is connected to a gate of the second transistor.
11. The voltage-controlled oscillator as set forth in claim 8 , wherein the direct current block comprises:
a first direct current block capacitor disposed between the second control node and the first oscillation node; and
a second direct current block capacitor disposed between the first control node and the second oscillation node.
12. The voltage-controlled oscillator as set forth in claim 8 , wherein the bias circuit comprises:
a voltage supply disposed between the power source voltage and a common connection node;
a third transistor disposed between the common connection node and the ground voltage and controlled by a voltage level of the junction node;
a first resistor disposed between the common connection node and the first control node; and
a second resistor disposed between the common connection node and the second control node.
13. The voltage-controlled oscillator as set forth in claim 12 , wherein the third transistor is an n-channel metal-oxide-semiconductor transistor, and
wherein the gate of the third transistor is coupled to the junction node.
14. The voltage-controlled oscillator as set forth in claim 8 , wherein the frequencies of the first and second oscillation signals are regulated by the control voltage.