Injection-locked phase-locked loop with a self-aligned injection window

• US 8,432,198 B2
• Filed: 09/02/2011
• Issued: 04/30/2013
• Est. Priority Date: 09/10/2010
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Liang, Che-Fu, Hsiao, Keng-Jan
• Primary Examiner(s): Donovan, Lincoln
• Assistant Examiner(s): Cole, Brandon S
• Application Number:
  US13/225,274
• Publication Number:
  US 20120062293A1
• Time in Patent Office: 606 Days
• Field of Search: 327/141, 327144-163, 331/1/A, 331 15- 17, 375373-376
• US Class Current: 327/156
• CPC Class Codes: H03L 7/23 with pulse counters or frequency dividers

Abstract

An injection-locked phase-locked loop (ILPLL) with a self-aligned injection window is disclosed. In the ILPLL, a phase detector is provided to detect a phase difference between a pair of differential terminals of an injection-locked voltage-controlled oscillator (ILVCO) of the ILPLL. According to the detection, the phase detector generates a control signal, to align an oscillation output, generated from the pair of differential terminals of the ILVCO, with an injection pulse utilized in the ILVCO.

Claims

1. An injection-locked phase-locked loop with a self-aligned injection window, comprising:

a loop filter, providing a control voltage;

an injection pulse generator, generating an injection pulse based on a reference oscillation signal;

an injection-locked voltage-controlled oscillator, controlled by the control voltage and the injection pulse, and having a pair of differential terminals for generation of an oscillation output, wherein the control voltage is operative to adjust a frequency and/or a phase of the oscillation output, and the oscillation output is aligned with the injection pulse to limit a phase difference between the oscillation output and the injection pulse; and

a phase detector, coupled to the pair of differential terminals of the injection-locked voltage-controlled oscillator to detect, according to the injection pulse, a phase difference between signals on the pair of differential terminals and thereby generate a control signal, wherein the control signal is operative to further adjust the phase difference between the oscillation output and the injection pulse.

2. The injection-locked phase-locked loop as claimed in claim 1, wherein the phase detector comprises:

a sample and hold circuit, sampling and holding the signals at the pair of differential terminals of the injection-locked voltage-controlled oscillator according to the injection pulse, to generate a first sample and hold output and a second sample and hold output; and

a voltage-to-current converter, providing the control signal by converting a voltage difference between the first and second sample and hold outputs to a current output.

3. The injection-locked phase-locked loop as claimed in claim 2, wherein the current output generated by the voltage-to-current converter of the phase detector is coupled to the loop filter to adjust the control voltage.

4. The injection-locked phase-locked loop as claimed in claim 3, further comprising:

a divider, generating a frequency-divided oscillation signal by dividing the frequency of the oscillation output;

a phase and frequency detector, detecting a phase difference and a frequency difference between the frequency-divided oscillation signal and the reference oscillation signal to generate charge pump control signals; and

a charge pump, controlled by the charge pump control signals for adjusting the control voltage provided by the loop filter.

5. The injection-locked phase-locked loop as claimed in claim 3, wherein the injection-locked voltage-controlled oscillator comprises:

a differential ring oscillator, wherein one stage thereof provides differential outputs as the pair of differential terminals; and

an injection switch, turned on according to the injection pulse to short the pair of differential terminals.

6. The injection-locked phase-locked loop as claimed in claim 5, wherein the sample and hold circuit of the phase detector comprises:

a first capacitor and a second capacitor; and

a first sample switch and a second sample switch, both turned on according to the injection pulse, to couple the pair of differential terminals of the injection-locked voltage-controlled oscillator to the first and second capacitors, respectively,

wherein the first and second capacitors provide the first and second sample and hold outputs, respectively.

7. The injection-locked phase-locked loop as claimed in claim 3, wherein the voltage-to-current converter of the phase detector comprises:

a first bias current source; and

a first current mirror and a second current mirror, sharing the first bias current source to generate a first current and a second current according to the first and second sample and hold outputs,

wherein the first current mirror and the second current mirror are coupled to an output terminal of the voltage-to-current converter to provide a current difference between the first and the second currents as the current output of the voltage-to-current converter.

8. The injection-locked phase-locked loop as claimed in claim 7, wherein the voltage-to-current converter of the phase detector further comprises:

a pulser, generating a current path setting pulse;

a first switch, turned on according to an inverted signal of the current path setting pulse to couple an output terminal of the first current mirror to the output terminal of the voltage-to-current converter;

a second switch, turned on according to the current path setting pulse to couple an output terminal of the second current mirror to the output terminal of the voltage-to-current converter;

a third switch and a fourth switch, connected at a connection terminal, wherein the third switch is turned on according to the current path setting pulse to couple the output terminal of the first current mirror to the connection terminal, and the fourth switch is turned on according to the inverted signal of the current path setting pulse to couple the connection terminal to the output terminal of the second current mirror; and

a unit gain buffer, having an input terminal coupled to the output terminal of the voltage-to-current converter, and having an output terminal coupled to the connection terminal between the third and the fourth switches.

9. The injection-locked phase-locked loop as claimed in claim 8, wherein the pulser is biased by a second bias current source which mirrors the first bias current source.

10. The injection-locked phase-locked loop as claimed in claim 8, wherein the pulser generates the current path setting pulse based on the reference oscillation signal from the crystal oscillator.

11. The injection-locked phase-locked loop as claimed in claim 2, further comprising:

a delay line, coupled to the injection pulse generator, and driven by the current output from the voltage-to-current converter of the phase detector.

12. The injection-locked phase-locked loop as claimed in claim 11, further comprising:

a divider, generating a frequency-divided oscillation signal by dividing the frequency of the oscillation output;

a phase and frequency detector, detecting a phase difference and a frequency difference between the frequency-divided oscillation signal and the reference oscillation signal to generate charge pump control signals; and

a charge pump, controlled by the charge pump control signals for adjusting the control voltage provided by the loop filter.

13. The injection-locked phase-locked loop as claimed in claim 11, wherein the injection-locked voltage-controlled oscillator comprises:

a differential ring oscillator, wherein one stage thereof provides differential outputs as the pair of differential terminals; and

an injection switch, turned on according to the injection pulse to short the pair of differential terminals.

14. The injection-locked phase-locked loop as claimed in claim 13, wherein the sample and hold circuit of the phase detector comprises:

a first capacitor and a second capacitor; and

a first sample switch and a second sample switch, both turned on according to the injection pulse, to couple the pair of differential terminals of the injection-locked voltage-controlled oscillator to the first and second capacitors, respectively,

wherein the first and second capacitors provide the first and second sample and hold outputs, respectively.

15. The injection-locked phase-locked loop as claimed in claim 11, wherein the voltage-to-current converter of the phase detector comprises:

a first bias current source; and

a first current mirror and a second current mirror, sharing the first bias current source to generate a first current and a second current according to the first and second sample and hold outputs,

wherein the first current mirror and the second current mirror are coupled to an output terminal of the voltage-to-current converter to provide a current difference between the first and the second currents as the current output of the voltage-to-current converter.

16. The injection-locked phase-locked loop as claimed in claim 15, wherein the voltage-to-current converter of the phase detector further comprises:

a pulser, generating a current path setting pulse;

a first switch, turned on according to an inverted signal of the current path setting pulse to couple an output terminal of the first current mirror to the output terminal of the voltage-to-current converter;

a second switch, turned on according to the current path setting pulse to couple an output terminal of the second current mirror to the output terminal of the voltage-to-current converter;

a third switch and a fourth switch, connected at a connection terminal, wherein the third switch is turned on according to the current path setting pulse to couple the output terminal of the first current mirror to the connection terminal, and the fourth switch is turned on according to the inverted signal of the current path setting pulse to couple the connection terminal to the output terminal of the second current mirror; and

a unit gain buffer, having an input terminal coupled to the output terminal of the voltage-to-current converter, and having an output terminal coupled to the connection terminal between the third and the fourth switches.

17. The injection-locked phase-locked loop as claimed in claim 16, wherein the pulser is biased by a second bias current source which mirrors the first bias current source.

18. The injection-locked phase-locked loop as claimed in claim 16, wherein the pulser generates the current path setting pulse based on the reference oscillation signal from the crystal oscillator.