IP Library › Granted Patent US 12671364
Granted Patent B2
US 12671364 · App. 18/939,145 · Granted Jun 30, 2026

Multi-mode voltage-controlled oscillator (VCO) with transformer-based coupling

Inventors: Shilei Hao (San Diego, CA); Yiwu Tang (San Diego, CA)
Assignee: Qualcomm Incorporated
H03B5/1296H03B5/1212H03B5/124
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Quick Facts
Patent No.
US 12671364
App. No.
18/939,145
Granted
Jun 30, 2026
Kind
B2
Abstract

Techniques and apparatus for oscillating signal generation using a multi-mode voltage-controlled oscillator (VCO) circuit with transformer-based coupling. An example VCO circuit generally includes a first pair of transistors associated with a first active negative transconductance circuit; a second pair of transistors associated with a second active negative transconductance circuit; a transformer comprising a primary winding and a secondary winding, the primary winding being coupled to the second pair of transistors; a first set of switches coupled between gates of the first pair of transistors and the secondary winding of the transformer; and a second set of switches coupled between the gates of the first pair of transistors and a first voltage node.

Claims (84)

1 . A voltage-controlled oscillator (VCO) circuit comprising:

a first pair of transistors for a first active negative transconductance circuit;

a second pair of transistors for a second active negative transconductance circuit;

a transformer comprising a primary winding and a secondary winding, the primary winding being coupled between drains of the second pair of transistors;

a first set of switches coupled between gates of the first pair of transistors and the secondary winding of the transformer; and

a second set of switches coupled between the gates of the first pair of transistors and a first voltage node.

2 . The VCO circuit of claim 1 , further comprising a switch including a first terminal coupled to a tap of the primary winding and including a second terminal coupled to a second voltage node.

3 . The VCO circuit of claim 2 , wherein in a first mode:

the first set of switches are configured to be open;

the second set of switches are configured to be closed; and

the switch is configured to be closed to couple the tap of the primary winding to the second voltage node.

4 . The VCO circuit of claim 3 , wherein in the first mode, the first active negative transconductance circuit is disabled and the second pair of transistors are effectively cross-coupled in the second active negative transconductance circuit.

5 . The VCO circuit of claim 3 , wherein in a second mode:

the first set of switches are configured to be closed;

the second set of switches are configured to be open; and

the switch is configured to be open.

6 . The VCO circuit of claim 2 , further comprising:

a third set of switches coupled between gates of the second pair of transistors and the secondary winding of the transformer; and

a fourth set of switches coupled between the gates of the second pair of transistors and a third voltage node, wherein the switch further includes a third terminal coupled to a fourth voltage node and wherein the switch can be configured to at least one of: be open, couple the first terminal to the second terminal, or couple the first terminal to the third terminal.

7 . The VCO circuit of claim 6 , wherein in a first mode:

the first set of switches are configured to be open;

the second set of switches are configured to be closed;

the switch is configured to couple the tap of the primary winding to the second voltage node;

the third set of switches are configured to be closed;

the fourth set of switches are configured to be open; and

the first active negative transconductance circuit is disabled.

8 . The VCO circuit of claim 7 , wherein in a second mode:

the first set of switches are configured to be closed;

the second set of switches are configured to be open;

the switch is configured to couple the tap of the primary winding to the fourth voltage node;

the third set of switches are configured to be open;

the fourth set of switches are configured to be closed; and

the second active negative transconductance circuit is disabled.

9 . The VCO circuit of claim 8 , wherein in a third mode:

the first set of switches are configured to be closed;

the second set of switches are configured to be open;

the switch is configured to be open;

the third set of switches are configured to be closed; and

the fourth set of switches are configured to be open.

10 . The VCO circuit of claim 8 , wherein the second voltage node comprises a power supply rail for the VCO circuit and wherein the fourth voltage node comprises a reference potential node for the VCO circuit.

11 . The VCO circuit of claim 1 , wherein the first active negative transconductance circuit comprises a plurality of controllable active negative transconductance cells and wherein one of the controllable active negative transconductance cells comprises the first pair of transistors, the first set of switches, and the second set of switches.

12 . The VCO circuit of claim 1 , wherein the VCO circuit lacks an alternating current (AC) coupling capacitor coupled between transistors in the first pair of transistors.

13 . The VCO circuit of claim 1 , wherein the gates of the first pair of transistors are directly connected to the secondary winding via respective switches of the first set of switches.

14 . The VCO circuit of claim 1 , further comprising a third set of switches, wherein the transformer further comprises a tertiary winding and wherein the third set of switches are coupled between gates of the second pair of transistors and the tertiary winding of the transformer.

15 . The VCO circuit of claim 14 , wherein the secondary winding and the tertiary winding have different coupling coefficients.

16 . The VCO circuit of claim 1 , wherein the primary winding is coupled to drains of the first pair of transistors and to the drains of the second pair of transistors.

17 . A method of oscillating signal generation using a voltage-controlled oscillator (VCO) circuit, the method comprising:

controlling a first set of switches coupled between gates of a first pair of transistors for a first active negative transconductance circuit and a secondary winding of a transformer; and

controlling a second set of switches coupled between the gates of the first pair of transistors and a first voltage node, wherein a primary winding of the transformer is coupled between drains of a second pair of transistors for a second active negative transconductance circuit.

18 . The method of claim 17 , further comprising controlling a switch including a first terminal coupled to a tap of the primary winding and including a second terminal coupled to a second voltage node.

19 . The method of claim 18 , wherein in a first mode:

controlling the first set of switches comprises opening the first set of switches;

controlling the second set of switches comprises closing the second set of switches; and

controlling the switch comprises closing the switch to couple the tap of the primary winding to the second voltage node, such that the first active negative transconductance circuit is disabled and the second pair of transistors are effectively cross-coupled in the second active negative transconductance circuit.

20 . The method of claim 19 , wherein in a second mode:

controlling the first set of switches comprises closing the first set of switches;

controlling the second set of switches comprises opening the second set of switches; and

controlling the switch comprises opening the switch.

21 . The method of claim 18 , further comprising:

controlling a third set of switches coupled between gates of the second pair of transistors and the secondary winding of the transformer; and

controlling a fourth set of switches coupled between the gates of the second pair of transistors and a third voltage node, wherein the switch further includes a third terminal coupled to a fourth voltage node and wherein the switch can be configured to at least one of: be open, couple the first terminal to the second terminal, or couple the first terminal to the third terminal.

22 . The method of claim 21 , wherein in a first mode:

controlling the first set of switches comprises opening the first set of switches;

controlling the second set of switches comprises closing the second set of switches;

controlling the switch comprises coupling the tap of the primary winding to the second voltage node;

controlling the third set of switches comprises closing the third set of switches; and

controlling the fourth set of switches comprises opening the fourth set of switches, such that the first active negative transconductance circuit is disabled.

23 . The method of claim 22 , wherein in a second mode:

controlling the first set of switches comprises closing the first set of switches;

controlling the second set of switches comprises opening the second set of switches;

controlling the switch comprises coupling the tap of the primary winding to the fourth voltage node;

controlling the third set of switches comprises opening the third set of switches; and

controlling the fourth set of switches comprises closing the fourth set of switches, such that the second active negative transconductance circuit is disabled.

24 . The method of claim 23 , wherein in a third mode:

controlling the first set of switches comprises closing the first set of switches;

controlling the second set of switches comprises opening the second set of switches;

controlling the switch comprises opening the switch;

controlling the third set of switches comprises closing the third set of switches; and

controlling the fourth set of switches comprises opening the fourth set of switches.

25 . The method of claim 23 , wherein the second voltage node comprises a power supply rail for the VCO circuit and wherein the fourth voltage node comprises a reference potential node for the VCO circuit.

26 . The method of claim 17 , wherein:

the first active negative transconductance circuit comprises a plurality of controllable active negative transconductance cells;

one of the controllable active negative transconductance cells comprises the first pair of transistors, the first set of switches, and the second set of switches; and

the method further comprises controlling a number of the plurality of controllable active negative transconductance cells for operation of the VCO circuit.