Methods and circuitry for reducing intermodulation in integrated transceivers

• US 7,050,777 B2
• Filed: 10/22/2001
• Issued: 05/23/2006
• Est. Priority Date: 10/22/2001
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Cai, Yijun
• Primary Examiner(s): Chan, Wing
• Assistant Examiner(s): Jamal, Alexander
• Application Number:
  US10/037,897
• Publication Number:
  US 20030078022A1
• Time in Patent Office: 1,674 Days
• Field of Search: 375371-376, 331/46, 331/2, 331/16, 455 86- 87, 455/236.1, 455/255, 455208-209, 455/259, 455/264, 455/265, 455/295, 455/204
• US Class Current: 455/295
• CPC Class Codes: H03L 1/00 Stabilisation of generator output against variations of physical values, e.g. power supply
• CPC Class Codes: H03L 7/07 using several loops, e.g. for redundant clock signal generation
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input

Abstract

Methods and circuitry reduce adverse impacts of intermodulation and optimize performance of integrated circuits that include two or more oscillator circuits on the same chip. In one embodiment, intermodulation between voltage-controlled oscillators (VCOs)in the receiver and transmitter paths of a transceiver is reduced by adjusting relative power of the VCOs and/or bandwidths of the phase-locked loops (PLLs). The invention measures the injection lock frequency range of the VCOs based on which transmitter and receiver VCO power and loop bandwidths are adjusted.

Claims

1. A method of measuring an injection lock frequency range for an integrated circuit having a first voltage-controlled oscillator and a second voltage-controlled oscillator, the method comprising the steps of:

applying a control voltage to an input of the second voltage-controlled oscillator such that an output frequency of the second voltage-controlled oscillator locks to an output frequency of the first voltage-controlled oscillator; and

varying the output frequency of the first voltage-controlled oscillator until the output frequency of the second voltage-controlled oscillator falls out of lock with the output frequency of the first voltage-controlled oscillator.

2. A method as in claim 1, wherein the step of applying the control voltage to the input of the second voltage-controlled oscillator involves the step of switching the input of the second voltage-controlled oscillator from an output of a low pass filter to a control signal to which the control voltage is applied.

3. A method as in claim 1, wherein the step of applying the control voltage to the input of the second voltage-controlled oscillator further involves the step of:

monotonically changing the control voltage until the output frequency of the second voltage-controlled oscillator locks to the output frequency of the first voltage-controlled oscillator.

4. A method as in claim 1, wherein the first voltage-controlled oscillator is an element of a first phase-locked loop.

5. A method as in claim 1, wherein the step of varying the output frequency of the first voltage-controlled oscillator involves the step of:

changing a frequency of an input stream to the first phase-locked loop.

6. A method as in claim 1, wherein the second voltage-controlled oscillator is an element of a second phase-locked loop.

17. A method as in claim 1, wherein the step of varying the output frequency of the first voltage-controlled oscillator involves the step of:

changing a frequency of an input stream to the first phase-locked loop.

18. A method as in claim 17, wherein the second voltage-controlled oscillator is an element of a second phase-locked loop.

7. A method of computing an injection signal power within a voltage-controlled oscillator on an integrated circuit, the method comprising the steps of:

determining an injection lock frequency range of the voltage-controlled oscillator;

determining a que of an LC tank within a voltage-controlled oscillator;

determining a free-run frequency of the voltage-controlled oscillator;

determining a free-run output power of the voltage-controlled oscillator; and

calculating an injection signal power value proportional to a product of a square of the injection lock frequency range, a square of the que, and the free-run output power of the voltage-controlled oscillator divided by a square of the free-run output frequency of the voltage-controlled oscillator, wherein the step of determining an injection lock frequency range comprises the step of measuring an injection lock frequency range of the voltage-controlled oscillator, and wherein the step of measuring the injection lock frequency range of the voltage-controlled oscillator comprises the steps of;

applying a control voltage to an input of the voltage-controlled oscillator such that the output frequency of the voltage-controlled oscillator locks to an output frequency of another voltage-controlled oscillator on the integrated circuit; and

varying the output frequency of the voltage-controlled oscillator until the output frequency of the voltage-controlled oscillator falls out of lock with the other voltage-controlled oscillator.

8. A method as in claim 7, further comprising the steps of:

wherein the step of applying the control voltage to the input of the voltage-controlled oscillator involves the step of switching the input of the voltage-controlled oscillator from an output of a low pass filter to a control signal to which the control voltage is applied.

9. A method as in claim 8, wherein the step of applying the control voltage to the input of the second voltage-controlled oscillator further involves the step of:

monotonically changing the control voltage until the output frequency of the second voltage-controlled oscillator locks to the output frequency of the first voltage-controlled oscillator.

10. A method as in claim 7, wherein the other voltage-controlled oscillator is an element of a first phase-locked loop.

11. A method as in claim 10, wherein the step of varying the output frequency of the other voltage-controlled oscillator comprises the step of:

changing a frequency of an input stream to the first phase-locked loop.

12. A method as in claim 11, wherein the voltage-controlled oscillator is an element of a second phase-locked loop.

13. A method of reducing an injection lock frequency range of a second voltage-controlled oscillator in an integrated circuit having first and second voltage-controlled oscillators, the method comprising the steps of:

measuring an injection lock frequency range of the second voltage controlled oscillator; and

increasing a free-run output power of the second voltage-controlled oscillator,

wherein the step of measuring the injection lock frequency range of the second voltage-controlled oscillator comprises the steps of;

applying a control voltage to an input of the second voltage-controlled oscillator such that an output frequency of the second voltage-controlled oscillator locks to an output frequency of the first voltage-controlled oscillator; and

varying the output frequency of the first voltage-controlled oscillator until the output frequency of the second voltage-controlled oscillator falls out of lock with the output frequency of the first voltage-controlled oscillator.

14. A method as in claim 13,

wherein the step of applying the control voltage to the input of the second voltage-controlled oscillator involves the step of switching the input of the second voltage-controlled oscillator from an output of a low pass filter to a control signal to which the control voltage is applied.

15. A method as in claim 14, wherein the step of applying the control voltage to the input of the second voltage-controlled oscillator further involves the step of:

monotonically changing the control voltage until the output frequency of the second voltage-controlled oscillator locks to the output frequency of the first voltage-controlled oscillator.

16. A method as in claim 13, wherein the first voltage-controlled oscillator is an element of a first phase-locked loop.

19. A method as in claim 13, wherein the step of increasing the free-run output power of the second voltage-controlled oscillator is accomplished by increasing a signal amplitude of the second voltage-controlled oscillator.

20. A method as in claim 13, wherein the step of increasing the free-run output power of the second voltage-controlled oscillator is accomplished by reducing a loading of an output signal of the second voltage-controlled oscillator.

21. A method as in claim 16, further comprising the step of:

increasing a loop bandwidth in the first phase-locked loop.

22. A method as in claim 21, wherein the step of increasing the loop bandwidth in the first phase-locked loop is accomplished by increasing a pass band of a loop filter within the first phase-locked loop.

23. A method of reducing intermodulation between a first voltage-controlled oscillator (VCO) in a first phase-locked loop (PLL) and a second VCO in a second PLL, comprising:

measuring an injection lock frequency range of the second VCO with respect to the first VCO;

measuring a signal power of the second VCO;

determining a crosstalk power between the first and the second VCOs using the measured injection lock frequency range and the measured signal power of the second VCO; and

adjusting a signal power ratio between the first VCO and the second VCO to reduce intermodulation.

24. The method of claim 23 further comprising adjusting a loop bandwidth of the first PLL relative to that of the second PLL to reduce intermodulation.

25. The method of claim 24, wherein the first PLL is part of a transmitter and the second PLL is part of a receiver, and wherein the step of adjusting a signal power ratio comprises increasing a power of the first VCO relative to that of the second vCO.

26. The method of claim 25, wherein the step of adjusting a loop bandwidth comprises increasing a loop bandwidth of the second PLL relative to that of the first PLL.