Phase noise reduction in voltage controlled oscillators

• US 10,224,872 B2
• Filed: 04/07/2016
• Issued: 03/05/2019
• Est. Priority Date: 01/10/2014
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Valdes-Garcia, Alberto, Sadhu, Bodhisatwa
• Primary Examiner(s): Kinkead, Arnold
• Application Number:
  US15/093,169
• Publication Number:
  US 20160226441A1
• Time in Patent Office: 1,062 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 method of operating a voltage controlled oscillator (VCO) comprising an LC tank circuit, an oscillator core, and a noise by-pass circuit connected in parallel with the LC tank circuit and the 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; and

operating the noise by-pass circuit to form 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 oscillator core.

2. The method according to claim 1, wherein the oscillator core includes first and second cross-coupled semiconductor devices, and the operating the noise-by-pass circuit includes operating the noise by-pass circuit to reduce noise contributions from the cross-coupled semiconductor devices.

3. The method according to claim 1, wherein the noise by-pass circuit comprises a series resonance, and the operating the noise by-pass circuit includes operating the series resonance to resonate at approximately twice the oscillator frequency.

4. The method according to claim 3, wherein the noise by-pass circuit includes a capacitor and an inductor located in series.

5. The method according to claim 3, wherein the noise by-pass circuit includes a capacitor and a transmission line located in series.

6. The method according to claim 3, wherein the operating the noise by-pass circuit includes adjusting the frequency at which the noise by-pass circuit resonates.

7. The method according to claim 6, wherein the adjusting the frequency at which the noise by-pass circuit resonates includes applying a variable voltage to the by-pass circuit to adjust the frequency at which the noise by-pass circuit resonates.

8. The method according to claim 6, wherein the adjusting the frequency at which the noise by-pass circuit resonates includes applying a variable digital signal to the by-pass circuit to adjust the frequency at which the noise by-pass circuit resonates.

9. The method according to claim 6, wherein the by-pass circuit includes a variable capacitor, and the adjusting the frequency at which the noise by-pass circuit resonates includes varying the capacitance of the variable capacitor to vary the frequency at which the noise by-pass circuit resonates.

10. The voltage controlled oscillator according to claim 9, wherein the varying the capacitance of the variable capacitor includes applying a variable control signal to the variable capacitor to vary the capacitance thereof.

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

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.

12. The method according to claim 11, wherein the operating a low-impedance, noise by-pass circuit includes:

introducing the noise by-pass circuit into the VCO, with the noise by-pass circuit connected to a supply node and to a tail node, in parallel with the LC tank circuit and the oscillator core; and

tuning the noise by-pass circuit to obtain a specified performance of the VCO.

13. The method according to claim 12, wherein the introducing the noise by-pass circuit includes including a capacitor and a transmission line in the noise by-pass circuit.

14. The method according to claim 12, wherein the tuning the noise by-pass circuit includes operating the capacitor and the transmission line wherein the noise by-pass circuit resonates at approximately twice the frequency of the oscillator output.

15. The method according to claim 11, wherein the tuning the noise by-pass circuit includes applying a variable signal to the by-pass circuit to vary the frequency at which the noise by-pass circuit resonates.

16. A method of operating a voltage controlled oscillator (VCO) comprising an LC tank circuit, an oscillator core including first and second cross-coupled semiconductor devices, and a noise by-pass circuit connected in parallel with the LC tank circuit and the 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; and

operating the noise by-pass circuit to form 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 cross-coupled semiconductor devices of the oscillator core.

17. The method according to claim 16, wherein the operating the noise by-pass circuit includes applying a variable voltage source to the by-pass circuit to adjust the the frequency at which the noise by-pass circuit resonates.

18. The method according to claim 17, wherein the operating the noise by-pass circuit includes applying a variable digital signal source to the noise by-pass circuit to adjust the frequency at which the noise by-pass circuit resonates.

19. The method according to claim 16, wherein the by-pass circuit includes a variable capacitor, and the operating the noise by-pass circuit includes varying the capacitance of the variable capacitor to vary the frequency at which the noise by-pass circuit resonates.

20. The method according to claim 19, wherein the varying the capacitance of the variable capacitor includes applying a variable control signal to the variable capacitor to vary the capacitance thereof.