Beating high-Q resonators oscillator

• US 10,523,225 B2
• Filed: 08/29/2017
• Issued: 12/31/2019
• Est. Priority Date: 08/29/2017
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Bahr, Bichoy, Haroun, Baher, Kiaei, Ali
• Primary Examiner(s): Johnson, Ryan
• Application Number:
  US15/690,144
• Publication Number:
  US 20190068198A1
• Time in Patent Office: 854 Days
• CPC Class Codes: H03H 9/54 comprising resonators of piezoelectric or electrostrictive material H03H9/64 takes precedence
• CPC Class Codes: H03H 9/589 Acoustic mirrors
• CPC Class Codes: H03K 3/013 Modifications of generator to prevent operation by noise or interference
• CPC Class Codes: H03K 3/0315 Ring oscillators
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation
• CPC Class Codes: H03L 7/24 using a reference signal directly applied to the generator

Abstract

For producing a low-power, low-phase noise oscillating signal using a self-injection locking oscillator, examples include: producing, using an oscillator, a signal having a base frequency component, an Mth harmonic component and a Pth harmonic component, in which M and P are selected integers and M>P>1; filtering the signal through one or more bandpass filters including at least two resonators, the filters having Q factor ≥5, the filters configured to pass the Mth and Pth harmonic components; multiplying the filtered Mth and Pth harmonic components together to produce a multiplied signal, and filtering the multiplied signal using a low pass filter to pass a difference between the filtered Mth and Pth harmonic components, the difference including a filtered beat frequency waveform; and injecting the filtered beat frequency waveform into the oscillator to injection lock the signal to the filtered beat frequency waveform.

Claims

1. A method of producing a clock signal, the method comprising:

a) producing, using an oscillator, a signal having a base frequency component, an Mth harmonic component and a Pth harmonic component, in which M and P are integers, and M>

P>

1;

b) filtering the signal through one or more bandpass filters including at least two resonators, in which the bandpass filters have Q factor ≥

5and pass the Mth and Pth harmonic components as filtered Mth and Pth harmonic components, respectively;

c) multiplying the filtered Mth and Pth harmonic components together to produce a multiplied signal, and filtering the multiplied signal using a low pass filter to pass a difference between the filtered Mth and Pth harmonic components, the difference including a filtered beat frequency waveform; and

d) injecting the filtered beat frequency waveform into the oscillator to injection lock the signal to the filtered beat frequency waveform, in which the base frequency of the signal is self-injection locked.

2. The method of claim 1, wherein the bandpass filters include two BAW resonators that cancel out thermal drifts in the beat frequency.

3. The method of claim 1, wherein the bandpass filters are exposed to a same absolute drift-inducing phenomena, and the bandpass filters respond to the same absolute drift-inducing phenomena.

4. The method of claim 1, wherein the producing includes using a harmonic generator to generate the signal using an output of the oscillator.

5. The method of claim 1, wherein the beat frequency is an Nth harmonic of the base frequency.

6. The method of claim 1, wherein the oscillator is a ring oscillator including N stages, and the injecting includes injecting the filtered beat frequency waveform into each of the N stages.

7. The method of claim 1, further comprising inducing a group delay in the Mth and Pth harmonic components of the signal using the bandpass filters.

8. The method of claim 1, wherein the multiplying includes squaring the sum of the Mth and Pth harmonic components.

9. The method of claim 1, wherein M−

P=1.

10. The method of claim 1, wherein M−

P>

1.

11. The method of claim 1, wherein the bandpass filters are affixed relative to a same substrate.

12. A self-injection locking clock circuit, comprising:

a) an oscillator configured to output a periodic signal with at least a base frequency and configured to injection lock to an injected signal;

b) one or more bandpass filters having Q factor ≥

5, the bandpass filters configured to pass an Mth harmonic and a Pth harmonic of the base frequency to output a filtered Mth harmonic and a filtered Pth harmonic, M and P being integers at least partially dependent on the base frequency, in which M>

P>

1, and the bandpass filters are operatively coupled to the oscillator and configured to filter the oscillator output;

c) a multiplier configured to multiply the filtered Mth harmonic by the filtered Pth harmonic to produce a multiplied Mth*Pth harmonic waveform having a beat frequency component including a difference between the filtered Mth harmonic and the filtered Pth harmonic; and

d) a low pass filter configured to pass the beat frequency component as a filtered beat frequency component to inject the, filtered beat frequency component into the oscillator.

13. The circuit of claim 12, wherein ones of the bandpass filters include a MEMS resonator or an LC tank.

14. The circuit of claim 12, wherein ones of the bandpass filters include a bulk acoustic wave resonator.

15. The circuit of claim 12, wherein the bandpass filters include two BAW resonators configured to cancel out thermal drifts in the beat frequency.

16. The circuit of claim 12, wherein the bandpass filters are exposed to a same absolute drift-inducing phenomena, and the bandpass filters are configured to respond to the same absolute drift-inducing phenomena.

17. The circuit of claim 12, wherein the beat frequency component has a same frequency as an Nth harmonic of the base frequency, and N is an integer, and N>

1.

18. The circuit of claim 12, further comprising a harmonic generator operatively connected to the oscillator to use the periodic signal to generate the Mth and Pth harmonics.

19. The circuit of claim 12, wherein the oscillator is a ring oscillator including N stages, and the injecting includes injecting the filtered beat frequency component into each of the N stages, and N is an integer and N>

1.

20. The circuit of claim 12, wherein the bandpass filters are affixed relative to a same substrate.