Phase noise reduction in voltage controlled oscillators

• US 9,330,214 B2
• Filed: 01/10/2014
• Issued: 05/03/2016
• 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:
  US14/152,330
• Publication Number:
  US 20150200627A1
• Time in Patent Office: 844 Days
• Field of Search: 331/167, 331/177.V, 331/117.R, 331/117.FE
• US Class Current: 1/1
• 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; and

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.

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

3. The voltage controlled oscillator according to claim 1, wherein the noise by-pass circuit comprises a series resonance tuned to resonate at approximately twice the oscillator frequency.

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

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

6. The voltage controlled oscillator according to claim 3, further comprising a frequency control to apply a variable signal to the by-pass circuit to adjust the frequency at which the noise by-pass circuit resonates.

7. The voltage controlled oscillator according to claim 6, wherein the frequency control includes a variable voltage source to apply a variable voltage to the by-pass circuit to adjust the frequency at which the noise by-pass circuit resonates.

8. The voltage controlled oscillator according to claim 6, wherein the frequency control includes a variable digital signal source to apply a variable digital signal to the by-pass circuit to adjust the frequency at which the noise by-pass circuit resonates.

9. The voltage controlled oscillator according to claim 6, wherein:

the by-pass circuit includes a variable capacitor; and

the frequency control applies the variable signal to the variable capacitor to vary a capacitance thereof and thereby to vary the frequency at which the noise by-pass circuit resonates.

10. The voltage controlled oscillator according to claim 1, wherein:

the noise by-pass circuit includes a capacitor.