Voltage controlled oscillator, system circuit, and control method thereof

1 . A voltage controlled oscillator (VCO), comprising:

a first oscillator circuit comprising:

a first active oscillation core electrically coupled to a first output end and a second output end of the first oscillator circuit; and

a first inductor, wherein a first end and a second end of the first inductor are electrically coupled to the first output end and the second output end of the first oscillator circuit, respectively; and

a second oscillator circuit comprising:

a second active oscillation core electrically coupled to a first output end and a second output end of the second oscillator circuit; and

a second inductor, wherein a first end and a second end of the second inductor are electrically coupled to the first output end and the second output end of the second oscillator circuit, respectively,

wherein the first inductor is separate from the second inductor and embedded inside the second inductor,

wherein a total mutual inductance between the first and second inductors is smaller than or equal to a predetermined coupled inductance threshold, and

wherein the second inductor is wound in an annular shape, and the first inductor is wound in a figure-of-eight shape nested inside the annular shape of the second inductor.

2 . The VCO of claim 1 , wherein:

the first oscillator circuit further comprises a first current control circuit, wherein a first end and a second end of the first current control circuit are electrically coupled to the first active oscillation core and ground, respectively; and

the second oscillator circuit further comprises a second current control circuit, wherein a first end and a second end of the second current control circuit are electrically coupled to the second active oscillation core and the ground, respectively.

3 . The VCO of claim 1 , wherein:

the first active oscillation core is electrically coupled to a first power supply through a first switch of a first type;

the first output end of the first oscillator circuit is electrically coupled to ground through a first switch of a second type; and

the second output end of the first oscillator circuit is electrically coupled to the ground through a second switch of the second type.

4 . The VCO of claim 3 , wherein:

the second active oscillation core is electrically coupled to a second power supply through a third switch of the second type;

the first output end of the second oscillator circuit is electrically coupled to the ground through a second switch of the first type; and

the second output end of the second oscillator circuit is electrically coupled to the ground through a third switch of the first type.

5 . The VCO of claim 1 , wherein:

the first oscillator circuit further comprises a first variable capacitor connected in parallel with the first inductor, wherein a first end and a second end of the first variable capacitor are electrically coupled to the first and second output ends of the first oscillator circuit, respectively; and

the second oscillator circuit further comprises a second variable capacitor connected in parallel with the second inductor, wherein a first end and a second end of the second variable capacitor are electrically coupled to the first and second output ends of the second oscillator circuit, respectively.

6 . A method for controlling a voltage controlled oscillator (VCO) which comprises a first oscillator circuit and a second oscillator circuit, the first oscillator circuit comprising a first inductor, the second oscillator circuit comprising a second inductor, the method comprising:

controlling, at a transmit mode, an operation of the first oscillator circuit to provide a transmitter (TX) local oscillator signal for data transmission, wherein the first inductor is configured to implement a first resonant frequency selection network for the first oscillator circuit at the transmit mode; and

controlling, at a receive mode, an operation of the second oscillator circuit to provide a receiver (RX) local oscillator signal for data transmission, wherein the second inductor is configured to implement a second resonant frequency selection network for the second oscillator circuit at the receive mode,

wherein the first oscillator circuit further comprises a first active oscillation core electrically coupled to a first output end and a second output end of the first oscillator circuit, and a first end and a second end of the first inductor are electrically coupled to the first output end and the second output end of the first oscillator circuit, respectively,

wherein the second oscillator circuit further comprises a second active oscillation core electrically coupled to a first output end and a second output end of the second oscillator circuit, and a first end and a second end of the second inductor are electrically coupled to the first output end and the second output end of the second oscillator circuit, respectively,

wherein a total mutual inductance between the first and second inductors is smaller than or equal to a predetermined coupled inductance threshold, and

wherein the second inductor is wound in an annular shape, and the first inductor is wound in a figure-of-eight shape nested inside the annular shape of the second inductor.

7 . The method of claim 6 , wherein controlling, at the transmit mode, the operation of the first oscillator circuit to provide the TX local oscillator signal for data transmission comprises:

connecting a first power supply to the first oscillator circuit;

disconnecting the first output end and the second output end of the first oscillator circuit from ground; and

outputting the TX local oscillator signal through the first and second output ends of the first oscillator circuit.

8 . The method of claim 7 , further comprising:

turning off, at the transmit mode, the operation of the second oscillator circuit.

9 . The method of claim 8 , wherein turning off, at the transmit mode, the operation of the second oscillator circuit comprises:

disconnecting a second power supply from the second oscillator circuit; and

connecting the first output end and the second output end of the second oscillator circuit to the ground.

10 . The method of claim 9 , wherein controlling, at the receive mode, the operation of the second oscillator circuit to provide the RX local oscillator signal comprises:

connecting the second power supply to the second oscillator circuit;

disconnecting the first output end and the second output end of the second oscillator circuit from the ground; and

outputting the RX local oscillator signal through the first and second output ends of the second oscillator circuit.

11 . The method of claim 10 , further comprising:

turning off, at the receive mode, the operation of the first oscillator circuit.

12 . The method of claim 11 , wherein turning off, at the receive mode, the operation of the first oscillator circuit comprises:

disconnecting the first power supply from the first oscillator circuit; and

connecting the first output end and the second output end of the first oscillator circuit to the ground.

13 . A system circuit, comprising:

a communication unit configured for data communication with an external communication network, the communication unit comprising:

a voltage controlled oscillator (VCO), comprising:

a first oscillator circuit comprising:

a first active oscillation core electrically coupled to a first output end and a second output end of the first oscillator circuit; and

a first inductor, wherein a first end and a second end of the first inductor are electrically coupled to the first output end and the second output end of the first oscillator circuit, respectively; and

a second oscillator circuit comprising:

a second active oscillation core electrically coupled to a first output end and a second output end of the second oscillator circuit; and

a second inductor, wherein a first end and a second end of the second inductor are electrically coupled to the first output end and the second output end of the second oscillator circuit, respectively,

wherein the first inductor is separate from the second inductor and embedded inside the second inductor,

wherein a total mutual inductance between the first and second inductors is smaller than or equal to a predetermined coupled inductance threshold, and

wherein the second inductor is wound in an annular shape, and the first inductor is wound in a figure-of-eight shape nested inside the annular shape of the second inductor.

14 . The system circuit of claim 13 , wherein:

the VCO is configured to provide a transmitter (TX) local oscillator signal for data transmission through the first output end and the second output end of the first oscillator circuit; and

the VCO is configured to provide a receiver (RX) local oscillator signal through the first output end and the second output end of the second oscillator circuit.

15 . The VCO of claim 1 , wherein the first active oscillation core comprises a first control transistor, a second control transistor, a third control transistor, and a fourth control transistor,

wherein the first control transistor and the second control transistor are configured as a first cross-coupled switch pair, and

wherein the third control transistor and the fourth control transistor are configured as a second cross-coupled switch pair.

16 . The VCO of claim 15 , wherein the second active oscillation core comprises a fifth control transistor, a sixth control transistor, a seventh control transistor, and an eighth control transistor,

wherein the fifth control transistor and the sixth control transistor are configured as a third cross-coupled switch pair, and

wherein the seventh control transistor and the eighth control transistor are configured as a fourth cross-coupled switch pair.

17 . The system circuit of claim 13 , wherein:

the first active oscillation core is electrically coupled to a first power supply; and

the second active oscillation core is electrically coupled to a second power supply different from the first power supply.