Quadrature ring oscillator

• US 6,744,325 B2
• Filed: 04/03/2002
• Issued: 06/01/2004
• Est. Priority Date: 04/03/2002
• Status: Expired due to Term

• Current Assignee: Sierra Monolithics, Inc. (Semtech Corporation)
• Original Assignee: Sierra Monolithics, Inc. (Semtech Corporation)
• Inventors: Krawczyk, Thomas W. Jr., Rowe, David A.
• Primary Examiner(s): Kinkead, Arnold
• Application Number:
  US10/115,400
• Publication Number:
  US 20030189467A1
• Time in Patent Office: 790 Days
• Field of Search: 331/57, 331/117.R, 331/56, 331/45, 331/177.R, 331/135, 375/376
• US Class Current: 331/57
• CPC Class Codes: H03B 2200/0078 generating or using signals in quadrature
• CPC Class Codes: H03B 27/00 Generation of oscillations providing a plurality of outputs of the same frequency but differing in phase, other than merely two anti-phase outputs
• CPC Class Codes: H03B 5/1218 the generator being of the balanced type
• CPC Class Codes: H03B 5/1231 the amplifier comprising one or more bipolar transistors
• CPC Class Codes: H03B 5/1243 the means comprising voltage variable capacitance diodes
• CPC Class Codes: H03B 5/1253 the transistors being field-effect transistors

Abstract

A quadrature ring oscillator for high clock-rate applications is disclosed. A quadrature LC ring oscillator may use two stages of LC oscillators and variable mixers to provide consistent oscillation even at high clock rates. One stage of the quadrature ring oscillator comprises a first resonating element having an input and an output, and a first variable summer having L and P inputs and an output, with its L input being connected to the output of the first resonating element. The output of the first variable summer is connected to the input of the first resonating element The first variable summer may generate its output at a first phase by combining the L and P inputs. A second stage of the LC ring oscillator comprises a second resonating element, which has an input and an output, with its output being connected to the P input of the first variable summer. An inverter is used to produce an inverted signal of the output of the first resonating element. This stage also comprises a second variable summer having L and P inputs and an output, with its output connected to the input of the second resonating element. The P input of this second variable summer is connected to the inverted signal from the inverter and the L input is connected to the output of the second resonating element. The second variable summer may generate its output at a second phase by combining its L and P inputs.

Claims

1. An oscillator comprising:

a first resonating element having an input and an output;

a second resonating element having an input and an output, said second resonating element for generating an output that is a quadrature phase shift of said output of said first resonating element;

a first summer coupled to said first resonating element and said second resonating element, said first summer being adapted to selectively generate its output at a first phase shift;

a second summer coupled to said second resonating element, said second summer being adapted to selectively generate its output at a second phase shift;

an inverter coupled to said first resonating element and said second summer, said inverter being adapted to invert an input to generate an output.

2. An oscillator of claim 1, wherein said first and second resonating elements are varactor-less oscillators.

3. An oscillator of claim 1, wherein each of said first and second resonating elements comprises a fixed value capacitor and a fixed value inductor,

wherein each of said first and second resonating elements is adapted to achieve a predetermined operating frequency based on a phase difference between its output and input.

4. An oscillator of claim 1, wherein said first summer comprises inputs,

wherein one of said inputs of said first summer is coupled to said output of said second resonating element,

wherein a second one of said inputs of said first summer is coupled to said output of said first resonating element,

wherein said inputs of said first summer are quadrature inputs,

wherein outputs of said oscillator are said inputs of said first summer.

5. An oscillator of claim 1, wherein said second summer comprises inputs,

wherein one of said inputs of said second summer is coupled to said output of said second resonating element,

wherein a second one of said inputs of said second summer is coupled to said output of said inverter,

wherein said inputs of said second summer are quadrature inputs.

6. An oscillator of claim 1, wherein said first summer comprises a delay element.

7. An oscillator of claim 1, wherein said first summer is adapted to receive a tuning control signal.

8. An oscillator of claim 4, wherein said first phase shift is between a phase of said one of said inputs of said first summer and a phase of said second one of said inputs of said first summer.

9. An oscillator of claim 1, wherein said quadrature phase shift is substantially plus or minus 90°

of said output of said first resonating element,

wherein said quadrature phase shift is a time delay,

wherein said first phase shift is a time delay,

wherein said second phase shift is a time delay.

10. An oscillator of claim 1, wherein said first summer is adapted to produce an inherent delay.

11. An oscillator of claim 3, wherein said first resonating element further comprises a second capacitor, said second capacitor for being selectively turned on or off,

wherein said second resonating element further comprises a third capacitor, said third capacitor for being selectively turned on or off.

12. An oscillator of claim 1 for generating an output of at least 15 GHz.

13. An oscillator of claim 3, wherein said predetermined operating frequency of said first resonating element is determined based further on (i) a value of said fixed value capacitor, (ii) a value of said fixed value inductor, and (iii) a value of a control input to said first summer.

24. An oscillator of claim 1, each of said first and second resonating elements for receiving differential input signals and for generating differential output signals,

each of said first and second summers for receiving differential input signals and for generating differential signals.

14. A clock generator comprising:

a first resonating element with an input and an output, said first resonating element being adapted to generate said output with a first predetermined phase;

a phase adjustor having an input and an output, said input of said phase adjustor connected to said output of said first resonating element, said output of said phase adjustor connected to said input of said first resonating element, said phase adjustor being adapted to selectively generate its output with a second predetermined phase,

wherein said phase adjustor comprises;

a first variable summer having inputs and an output, one of said inputs of said first variable summer connected to said output of said first resonating element, said output of said first variable summer connected to said input of said first resonating element, said first variable summer being adapted to selectively generate its output with a first phase in response to said inputs of said first variable summer;

a second variable summer having inputs and an output, one of said inputs of said second variable summer connected to said output of said first resonating element, said second variable summer being adapted to selectively generate its output with a second phase in response to said inputs of said second variable summer;

a second resonating element having an input and an output, said input of said second resonating element connected to said output of said second variable summer, said output of said second resonating element connected to a second one of said inputs of said second variable summer, said output of said second resonating element coupled to a second one of said inputs of said first variable summer.

15. A clock generator of claim 14, wherein said phase adjustor further comprises:

an inverter having an input and an output, said output of said second resonating element coupled to said second one of said inputs of said first variable summer through said inverter, said input of said inverter connected to said output of said second resonating element, said output of said inverter connected to said second one of said inputs of said first variable summer.

16. A clock generator of claim 14, wherein:

said inputs of said first variable summer are quadrature inputs;

said inputs of said second variable summer are quadrature inputs.

17. A clock generator of claim 14, wherein:

said inputs of said first variable summer have a phase of about 0° and

270°

;

said inputs of said second variable summer have a phase of about 90° and

0°

.

18. A system comprising:

a clock recovery and demultiplexer unit;

said clock recovery and demultiplexer unit comprising;

a first resonating element with an input and an output, said first resonating element having a variable operating frequency determined in response to a phase difference between said output and said input;

a phase adjustor having an input and an output, said input of said phase adjustor connected said output of said first resonating element, said output of said phase adjustor connected to said input of said first resonating element, said phase adjustor being adapted to selectively generate its output with a first phase.

19. A system of claim 18, wherein said first resonating element is a varactor-less oscillator.

20. A system of claim 18, wherein said first resonating element comprises a fixed-value capacitor and a fixed-value inductor.

21. A system of claim 18, wherein said phase adjustor comprises:

a first variable summer having inputs and an output, one of said inputs of said first variable summer connected to said output of said first resonating element, said output of said first variable summer connected to said input of said first resonating element, said first variable summer being adapted to selectively generate its output with said first phase in response to said inputs of said first variable summer;

a second variable summer having inputs and an output, one of said inputs of said second variable summer connected to said output of said first resonating element, said second variable summer being adapted to selectively generate its output with a second phase in response to said inputs of said second variable summer;

a second resonating element having an input and an output, said input of said second resonating element connected to said output of said second variable summer, said output of said second resonating element connected to a second one of said inputs of said second variable summer;

an inverter having an input and an output, said input of said inverter connected to said output of said second resonating element, said output of said inverter connected to a second one of said inputs of said first variable summer.

22. A system of claim 21, wherein:

said inputs of said first variable summer are quadrature inputs;

said inputs of said second variable summer are quadrature inputs.

23. A system of claim 21, wherein:

said inputs of said first variable summer have a phase of about 0° and

270°

;

said inputs of said variable summer have a phase of about 90° and

0°

.