Phase noise reduction in voltage controlled oscillators

• US 10,574,183 B2
• Filed: 08/01/2018
• Issued: 02/25/2020
• Est. Priority Date: 01/10/2014
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Valdes-Garcia, Alberto, Sadhu, Bodhisatwa
• Primary Examiner(s): Kinkead, Arnold M
• Application Number:
  US16/052,192
• Publication Number:
  US 20180375472A1
• Time in Patent Office: 573 Days
• Field of Search: 331167, 331117 FE, 331117 R, 331177 V
• CPC Class Codes: G06F 2119/10 Noise analysis or noise optimisation
• CPC Class Codes: G06F 30/30 Circuit design
• CPC Class Codes: G06F 30/327 Logic synthesis; Behaviour synthesis, e.g. mapping logic, HDL to netlist, high-level language to RTL or netlist
• CPC Class Codes: G06F 30/36 Circuit design at the analogue level
• CPC Class Codes: H03B 1/00 Details
• CPC Class Codes: H03B 2200/0038 including a current mirror
• CPC Class Codes: H03B 2200/009 Reduction of phase noise
• 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 5/1228 the amplifier comprising one or more field effect transistors
• CPC Class Codes: H03B 5/1243 the means comprising voltage variable capacitance diodes
• CPC Class Codes: H03B 5/1281 the parameter being the amount of feedback

Abstract

A voltage controlled oscillator (VCO), a method of designing a voltage controlled oscillator, and a design structure comprising a semiconductor substrate including a voltage controlled oscillator are disclosed. In one embodiment, the VCO comprises an LC tank circuit for generating an oscillator output at an oscillator frequency, and an oscillator core including cross-coupled semiconductor devices to provide feedback to the tank circuit. The VCO further comprises a supply node, a tail node, and a noise by-pass circuit connected to the supply and tail nodes, in parallel with the tank circuit and the oscillator core. The by-pass circuit forms a low-impedance path at a frequency approximately twice the oscillator frequency to at least partially immunize the oscillator core from external noise and to reduce noise contribution from the cross-coupled semiconductor devices.

Claims

1. A voltage controlled oscillator (VCO) comprising:

an LC tank circuit for generating an oscillator output signal at an oscillator frequency (f_o);

an oscillator core including first and second cross-coupled semiconductor devices connected to the tank circuit to provide regenerative feedback to the tank circuit to help maintain the oscillator output stable;

a supply node connected to the tank circuit for connecting the VCO to a voltage source;

a tail node connected to the oscillator core for connecting the VCO to a current source;

a noise by-pass circuit having a first end connected to the supply node and a second end connected to the tail node and forming a low-impedance by-pass circuit connecting the supply node and the tail node, in parallel with the LC tank circuit and the oscillator core, at a frequency approximately twice the oscillator frequency to at least partially immunize the oscillator core from external noise and to reduce noise contribution from the cross-coupled semiconductor devices, and including a variable capacitor and a variable inductance transmission line; and

a frequency control including a voltage control applied to the variable capacitor and a digital control applied to the variable inductance transmission line, the voltage control and the digital control being used in tandem to adjust the frequency at which the noise by-pass circuit resonates to adjust a performance of the VCO.

2. The voltage controlled oscillator according to claim 1, wherein the voltage control and the digital control are linearly related to each other.

3. The voltage controlled oscillator according to claim 1, wherein the voltage control and the digital control are set using an analog based control.

4. The voltage controlled oscillator according to claim 1, wherein the voltage control and the digital control are set using a digital based control.

5. The voltage controlled oscillator according to claim 1, wherein the LC tank circuit includes a variable capacitor and a voltage control applied to the variable capacitor of the LC tank circuit to control the capacitor of the LC tank circuit.

6. The voltage controlled oscillator according to claim 5, wherein the voltage control of the LC tank circuit is set using an analog based control.

7. The voltage controlled oscillator according to claim 5, wherein the voltage control of the LC tank circuit is set using a digital based control.

8. The voltage controlled oscillator according to claim 5, wherein the voltage control of the LC tank circuit is linearly related to the voltage control and to the digital control of the frequency control.

9. The voltage controlled oscillator according to claim 1, further comprising a high impedance component between the supply node and the voltage source.

10. The voltage controlled oscillator according to claim 1, wherein the variable capacitor and the variable inductance transmission line are located in series in the noise by-pass circuit.

11. A method of operating a voltage controlled oscillator (VCO) comprising an LC tank circuit and an oscillator core, the method comprising:

using the LC tank circuit for generating an oscillator output signal at an oscillator frequency (f_o);

operating the oscillator core to provide regenerative feedback to the tank circuit to help maintain the oscillator output stable;

connecting the VCO to a voltage source;

connecting the VCO to a current source;

operating a low-impedance, noise by-pass circuit in parallel with the LC tank circuit and the oscillator core, at a frequency approximately twice the oscillator frequency to at least partially immunize the oscillator core from external noise and to reduce noise contribution from the oscillator core, the low-impedance, noise by-pass circuit including a variable capacitor and a variable inductance transmission line; and

applying a voltage control to the variable capacitor and a digital control to the variable inductance transmission line, and using the voltage control and the digital control in tandem to adjust the frequency at which the noise by-pass circuit resonates to adjust a performance of the VCO.

12. The method according to claim 11, wherein the voltage control and the digital control are linearly related to each other.

13. The method according to claim 11, further comprising using an analog based control to set the voltage control and the digital control.

14. The method controlled oscillator according to claim 11, further comprising using a digital based control to set the voltage control and the digital control.

15. The method according to claim 11, wherein the LC tank circuit includes a variable capacitor, and the method further comprises applying a voltage control to the variable capacitor of the LC tank circuit to control the capacitor of the LC tank circuit.

16. A design structure comprising machine readable instructions tangibly embodied in a machine readable hardware medium for design, manufacturing, or testing a semiconductor device, the design structure, when executed in the machine, generating a representation of a semiconductor substrate including a voltage controlled oscillator (VCO) comprising:

an LC tank circuit for generating an oscillator output signal at an oscillator frequency (f_o);

an oscillator core including first and second cross-coupled semiconductor devices connected to the tank circuit to provide regenerative feedback to the tank circuit to help maintain the oscillator output stable;

a supply node connected to the tank circuit for connecting the VCO to a voltage source;

a tail node connected to the oscillator core for connecting the VCO to a current source;

a noise by-pass circuit having a first end connected to the supply node and a second end connected to the tail node and forming a low-impedance by-pass circuit connecting the supply node and the tail node, in parallel with the LC tank circuit and the oscillator core, at a frequency approximately twice the oscillator frequency to at least partially immunize the oscillator core from external noise and to reduce noise contribution from the cross-coupled semiconductor devices, and including a variable capacitor and a variable inductance transmission line; and

a frequency control including a voltage control applied to the variable capacitor and a digital control applied to the variable inductance transmission line, the voltage control and the digital control being used in tandem to adjust the frequency at which the noise by-pass circuit resonates to adjust a performance of the VCO.

17. The design structure according to claim 16, wherein the voltage control and the digital control are linearly related to each other.

18. The design structure according to claim 16, wherein the voltage control and the digital control are set using an analog based control.

19. The design structure controlled oscillator according to claim 16, wherein the voltage control and the digital control are set using a digital based control.

20. The design structure according to claim 16, wherein the LC tank circuit includes a variable capacitor and a voltage control applied to the variable capacitor of the LC tank circuit to control the capacitor of the LC tank circuit.